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Interfacing DNA Oligonucleotides with Calcium Phosphate and Other Metal Phosphates Liu Wang, Zijie Zhang, Biwu Liu, Yibo Liu, Anand Lopez, Jian Wu, and Juewen Liu Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.7b03204 • Publication Date (Web): 11 Dec 2017 Downloaded from http://pubs.acs.org on December 12, 2017

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Interfacing DNA Oligonucleotides with Calcium Phosphate and Other

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Metal Phosphates

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Liu Wang1,2, Zijie Zhang2, Biwu Liu2, Yibo Liu2, Anand Lopez2, Jian Wu1* and Juewen Liu2*

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College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058,

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China

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Email: [email protected]

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Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo,

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Waterloo N2L 3G1, Ontario, Canada

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Email: [email protected]

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ACS Paragon Plus Environment

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Abstract

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Calcium phosphate (CaP) has long been used for DNA delivery, although its fundamental

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interaction with DNA, especially with single-stranded DNA oligonucleotides, remains to be fully

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understood. Using fluorescently labeled oligonucleotides, we herein studied DNA adsorption

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isotherm and the effect of DNA length and sequence. Longer DNAs are adsorbed more strongly,

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and at neutral pH, poly-C DNAs are adsorbed more than the other three DNA homopolymers.

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However, at near pH 11, the pH of CaP synthesis, T30 DNA is adsorbed more strongly than C30

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or A30. This can explain why T30 and G30 can fully inhibit the growth of CaP, while A30 and C30

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only retarded its growth kinetics. DNA adsorption also reduces aggregation of CaP. DNA

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desorption experiments were carried out using concentrated urea, thymidine or inorganic

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phosphate as competitors, and desorption was observed only in the presence of phosphate,

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suggesting that DNA uses its phosphate backbone to interact with the CaP surface. Desorption

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was also promoted by raising the NaCl concentration suggesting the electrostatic nature of

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interaction. Finally, ten different metal phosphate materials were synthesized by co-precipitating

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each metal ion (Ce3+, Fe3+, Ca2+, Ni2+, Zn2+, Mn2+, Ba2+, Cu2+, Sr2+, Co2+), and DNA adsorption

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by these phosphate precipitants was found to be related to their surface charge and metal

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chemistry. This work has revealed fundamental surface science of DNA adsorption by CaP and

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other metal phosphate salts, and this knowledge might be useful for gene delivery,

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biomineralization and DNA-directed assembly of metal phosphate materials.

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Introduction

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Hybrid nanomaterials containing DNA is of particular interest for applications in DNA delivery,1

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nanotechnology,2-3 and biosensor development.4-10 While extensive studies have been performed

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on DNA adsorption by noble metal nanoparticles,9,

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nanomaterials,10 metal phosphates are relatively under-explored. For example, calcium

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phosphate (CaP) is the most abundant inorganic component in biological hard tissues, such as

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teeth and bones. Synthetic CaP materials have good biocompatibility,13 and CaP has been widely

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used as biomaterials and for drug delivery.14-18 CaP has many phases, such as octacalcium

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phosphate, dicalcium phosphate, tetracalcium phosphate, amorphous calcium phosphate, and

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metal oxides,12 and carbon-based

hydroxyapatite (HAp).19-20 Among them, HAp is the most commonly used.

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An important application of CaP is to deliver DNA. Free naked DNA cannot enter cells

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due to their negative charges. CaP is a popular non-viral delivery vehicle for its safety,

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biocompatibility, biodegradability, and cost-effectiveness.13, 18 Typically, DNA is co-precipitated

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with calcium and phosphate ions,21 and the low intracellular pH leads to dissolution of CaP and

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release of DNA. CaP has also been utilized for purifying DNA from cells and virus.22-23 Epple

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synthesized multi-shelled CaP nanoparticles, in which DNA was incorporated both inside and

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outside. The interior DNA was protected from degradations, while the adsorbed DNA served as a

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protection layer against aggregation.24-25 CaP was also used as a target for selection of aptamers

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to achieve specific binding.26

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Given the importance of this system, many fundamental studies have been performed.

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For example, Okazaki et al believed that DNA was not in the HAp structure but adsorbed at the

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surface.27 Wang et al reported that DNA can be intercalated into the lamellar HAp through ion-

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exchange and electrostatic attraction.28-29 Revilla-López and coworkers reported that B-form 3


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duplex DNA could be encapsulated inside the nanopores and the phosphate backbone acts as a

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template for HAp growth.30-31 Ngourn et al reported the nucleation of DNA-templated CaP

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mineralization in 15 min.32 Given these progress, however, a full fundamental understanding on

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the interaction between DNA and CaP is still lacking, and most previous work only focused on

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long double-stranded DNA. In this work, we systematically explore the adsorption of short

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single-stranded DNA. We also extended this study to many other metal phosphate materials for

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their DNA adsorption properties.

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Materials and Method

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Chemicals. Our FAM-labeled DNAs were from Integrated DNA Technologies (Coralville, IA),

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and unmodified DNAs were from Eurofins Genomics. The sequences of DNA are listed in Table

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S1. Sodium chloride, urea, thymidine free base, and 4-(2-hydroxyethyl) piperazine-1-

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ethanesulfonate (HEPES) were from Mandel Scientific (Guelph, Ontario, Canada). Sodium

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phosphate monobasic and ammonium phosphate monobasic were from Sigma-Aldrich. Calcium

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nitrate tetrahydrate was from Fisher Scientific. Ammonium hydroxide (28.0 ~ 30.0 %) was from

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Alfa Aesar. Milli-Q water was used for all experiments.

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Preparation of CaP. In a typical experiment, calcium nitrate tetrahydrate (0.0588 g) was

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dissolved in 25 mL H2O. Ammonium hydroxide (28.0 ~ 30.0%) was added to adjust the pH to

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11.0. Then ammonium phosphate monobasic (0.0172 g) was dissolved in 25 mL H2O and added

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dropwise into the calcium nitrate solution. The mixture was stirred at room temperature for 3 h

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and then aged for 48 h. The obtained products were washed with Milli-Q water and ethanol

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successively and centrifuged at 2000 rpm for 10 min. The products were dried with a vacuum 4


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oven for 12 h at around 70 °C. To grow CaP in the presence of DNA, DNA (500 µM, 60 µL) was

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mixed with 250 µL of the above calcium nitrate solution. Then 250 µL ammonium dihydrogen

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phosphate was added dropwise. The mixture was stirred at room temperature for 3 h.

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Transmission electron microscopy (TEM), dynamic light scattering (DLS), and X-ray

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diffraction (XRD). The TEM samples were prepared by dropping the CaP dispersion (100

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µg/mL) on a copper grid followed by air drying. TEM was performed on a Philips CM10

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microscope. The ζ-potential and DLS of CaP (50 µg/mL) were measured in 10 mM HEPES (pH

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7.6) using a Zetasizer Nano ZS90 (Malvern) at 25°C. Powder XRD was performed using a

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PANalytical Empyrean X-ray diffractometer with Cu Kα radiation (λ = 1.789 01 Å).

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Adsorption of DNA. The fluorescence of FAM-labeled DNA (200 nM) in 10 mM HEPES

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buffer (pH 7.6) was measured before adding CaP. We also included 100 mM NaCl in the buffer

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in some experiments. After knowing that NaCl weakens DNA adsorption, we excluded NaCl in

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subsequent experiments. Then 50 µg/mL CaP was added and incubated with the FAM-DNA for

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1 h. The mixture was centrifuged at 5000 rpm for 10 min and the fluorescence of the supernatant

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was measured. The adsorbed DNA was calculated based on the decreased fluorescent signal.

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Desorption of DNA. After incubating the FAM-labeled DNA with CaP in 10 mM HEPES buffer

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(pH 7.6) for 1 h. The mixture was centrifuged at 5000 rpm for 10 min and the supernatant was

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used for measuring the fluorescence signal. The precipitate was then dispersed in 10 mM HEPES

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(pH 7.6) containing 4 M urea, 1 mM phosphate or 1 mM thymidine at room temperature for 1 h

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and then centrifuged at 5000 rpm for 10 min. The supernatant fluorescence was then measured to

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quantify the amount of desorbed DNA.

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DNA adsorption by other metal phosphates. To prepare metal phosphate nanomaterials, 0.154

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g cerium (III) chloride heptahydrate, 0.112 g iron (III) chloride hexahydrate, 0.123 g manganese

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(II) chloride tetrahydrate, 0.148 g cobalt (II) chloride hexahydrate, 0.148 g nickel (II) chloride

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hexahydrate, 0.106 g copper (II) chloride dihydrate, 0.085 g zinc chloride, 0.166 g strontium

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chloride hexahydrate, 0.152 g barium chloride dihydrate, or 0.147 g calcium nitrate tetrahydrate

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was separately dissolved in 5 mL Milli-Q water to make a final molar concentration of metal to

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be 0.124 mM for divalent metal ions and 0.083 mM for trivalent metal ions. Then 0.043 g

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ammonium phosphate monobasic (in 0.075 mM solution) was added dropwise under pH 11. The

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mixture was stirred for 3 h at room temperature. After washing with water and ethanol, the

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precipitants were dried at 70 °C for 48 h. The solid was then dispersed in water with sonication

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for 12 h. For DNA adsorption, 100 µg/mL metal phosphate was used for adsorbing 200 nM

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FAM-T15 for 1 h in 10 mM HEPES buffer (pH 7.6). To monitor DNA adsorption, the solution

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was centrifuged at 15000 rpm for 15 min before taking pictures in a dark room with 470 nm LED

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excitation. To study the effect of NaCl and phosphate on DNA desorption, the supernatant was

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discarded after adsorption. Then the precipitate was dispersed in 10 mM HEPES buffer (pH 7.6)

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with 100 mM NaCl or 2 mM phosphate and incubated for 1 h. The solution was then centrifuged

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at 15000 rpm for 15 min before measuring the fluorescence.

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Results and Discussion

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Adsorption of DNA. Our calcium phosphate (CaP) samples were prepared by simply mixing

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calcium nitrate with ammonium phosphate monobasic salts in ammonium hydroxide at pH

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~11.33 To achieve a systematic understanding, we first varied the ratio of these two components

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by keeping the calcium concentration constant but varying the concentration of phosphate. These

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products were then characterized by TEM (Figure 1A). Their morphologies were very similar

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regardless of the ratio between calcium and phosphate. ζ-potential showed that they were all

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close to charge neutral (Figure 1B).

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Figure 1. (A) TEM micrographs and (B) ζ-potential of CaP synthesized at various Ca/P ratios.

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(C) Fluorescence photographs showing the mixture of FAM-T15 (200 nM) and CaP (50 µg/mL)

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in buffer (10 mM HEPES, pH 7.6, 100 mM NaCl) (tube 1) before and (tube 2) after

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centrifugation. (D) Percentage of DNA adsorption by CaP synthesized at various Ca/P ratios.

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Adsorption of DNA was then studied. We previously reported the adsorption of DNA by

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other materials such as gold,34 graphene oxide,35-36 and a few metal oxides.37 Most of these

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materials are fluorescence quenchers and DNA adsorption can be easily followed. After mixing

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our CaP with a carboxyfluorescein (FAM)-labeled DNA, however, the sample remained strongly

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fluorescent (Figure 1C, tube 1). We then centrifuged the sample and observed a strongly

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fluorescent pellet, while the supernatant was dark (tube 2). This indicated that CaP adsorbed the

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DNA, although it did not quench fluorescence. Regardless of the Ca/P ratio, the resulting

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materials all had a similar ability of adsorbing DNA (Figure 1D). Since the Ca/P ratio did not

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appear to affect DNA adsorption, we used a ratio of 1.67 for subsequent work.

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DNA adsorption isotherm and dissolution of CaP. To quantitatively understand the adsorption

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of single-stranded DNA by CaP, we first measured the adsorption isotherm. We fixed the

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concentration of CaP (50 µg/mL), and the concentration of DNA (FAM-T15) was varied. With

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increasing of DNA concentration, the amount of adsorbed DNA also increased (Figure 2A), and

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the adsorption profile could be fitted to a Langmuir isotherm, suggestion monolayer adsorption.

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This is reasonable since after adsorption, the surface DNA may repel further incoming DNA. By

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fitting the data to the Langmuir isotherm θ = aKC / (1 + KC) equation, where K is the Langmuir

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constant, a is the adsorption capacity, C is the DNA concentration, and θ is the fraction of

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adsorbed surface, we determined that K = 0.0047 ± 0.0002 nM-1, and around 188 nM DNA could

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be adsorbed by 50 µg/mL of CaP. This capacity is comparable with that reported in the literature

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for DNA on other nanomaterials.38

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We then switched the order of mixing by fixing the FAM-T15 DNA at 50 nM and varied

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the concentration of CaP (Figure 2B). In general, the more CaP added, the more DNA adsorbed,

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and ~95% DNA was adsorbed with 100 µg/mL of CaP. It is interesting to note that no DNA was 8


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adsorbed with 10 µg/mL CaP. We attributed this to the dissolution of CaP at neutral pH. The

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amount of adsorbed DNA was linearly related to the concentration of CaP between 20 and 50

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µg/mL. By extrapolating this line, we calculated the critical CaP concentration to be 14.2 µg/mL

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(e.g. the solubility limit), below which no adsorption occurred. From the CRC handbook, the

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solubility of different forms of CaP varies (e.g. CaHPO4, ~200 µg/mL; Ca3(PO4)2, ~1.2 µg/mL;

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while Ca(H2PO2)2, is rather soluble in water).39 Our measured solubility is within this range. This

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experiment suggests that to keep DNA adsorbed on CaP, the concentration of CaP needs to be

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relatively high to avoid dissolution. We previously also noticed the solubility issue of ZnO in

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affecting DNA adsorption,40 while most other inorganic materials are much less soluble.

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Figure 2. (A) Adsorption isotherm of FAM-T15 DNA on 50 µg/mL CaP fitted to a Langmuir

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isotherm model. (B) 50 nM FAM-T15 DNA adsorption as a function of CaP concentration.

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Adsorption was performed in 10 mM HEPES (pH 7.6), 100 mM NaCl. The linear region was

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fitted to a straight line, and the intercept at y = 0 is the solubility limit of CaP.

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Length and sequence dependent DNA adsorption. To further understand DNA adsorption, we

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studied the effect of DNA length with FAM-labeled poly-T DNA of 5, 10, 15 and 30 mer (Figure 9


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3A). All these DNAs were used at the same molar concentration. Almost no T5 DNA was

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adsorbed, while ~90% of T30 was adsorbed. Therefore, longer DNA was adsorbed more strongly,

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suggesting that individual nucleotide on the DNA chain was adsorbed weakly, and stable

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adsorption was achieved only when via polyvalent interactions. In contrast, for strong adsorption

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system (e.g. poly-A DNA on gold surface), DNA adsorption capacity is inversely proportional to

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the length of DNA.41-42 In this case, the capacity is limited by the surface area and both long and

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short oligonucleotides are adsorbed stably. In the CaP case, DNA has to reach a certain length to

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be adsorbed. We then compared the adsorption by using FAM-labeled 15-mer homo-DNAs

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(Figure 3B). The adsorption efficiency followed the order of C15 > G15 > T15 > A15. We recently

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noticed that poly-C DNA adsorbs more favorably on many surfaces, including graphene oxide,

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carbon nanotubes, tungsten disulfide, molybdenum disulfide, and a few metal oxides. Herein

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CaP added another example.43

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Desorption and adsorption mechanism. To understand the surface force responsible for DNA

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adsorption, we performed desorption experiments. CaP adsorbed with FAM-T15 was dispersed in

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buffer, and then various chemicals were respectively added, including 4 M urea, 1 mM

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phosphate and 1 mM thymidine. After incubation for 1 h, the samples were centrifuged and the

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supernatant fluorescence from desorbed DNA was measured (Figure 3C). Almost no DNA was

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desorbed by urea (a hydrogen bond disruptor), and thus hydrogen bonding was unlikely to be

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important for DNA adsorption. Free thymidine also failed to induce DNA desorption, suggesting

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DNA base did not contribute much to adsorption either. In contrast, inorganic phosphate ions

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nearly fully desorbed the DNA, suggesting that the DNA phosphate backbone is responsible for

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adsorption, likely by interacting with the Ca2+ centers on the surface of CaP.25 We further

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compared a double-stranded DNA of random sequence with its single-stranded components, and 10


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a similarly high adsorption efficiency was observed for all the samples, which also indicated that

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adsorption was through the phosphate backbone (Figure S1).

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Although CaP is overall nearly charge neutral, we reason that the interaction between

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DNA phosphate backbone and CaP might still be of electrostatic nature.44 To test this, we

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incubated FAM-T15 with CaP in the presence of various concentrations of NaCl (Figure 3D). The

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adsorbed DNA was inversely proportional to NaCl concentration.44 With 300 mM NaCl, DNA

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adsorption was nearly fully inhibited. Besides, a high concentration of NaCl also increased DNA

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desorption (Figure S2). In addition to screening the electrostatic interaction between phosphate

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and Ca2+, salt can condense DNA to make it into more folded structures, further decreasing its

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contact area on CaP. From the above DNA length-dependent studies, we know that the

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adsorption of each phosphate is important and a folded DNA might be less favorable for

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adsorption.

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Figure 3. The percentage of adsorption of 200 nM (A) FAM-labeled ploy-T DNA of different

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lengths; and (B) FAM-labeled 15-mer homo-DNA sequences by 50 µg/mL CaP in buffer (10

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mM HEPES, pH 7.6, 100 mM NaCl). (C) Desorption of FAM-labeled T15 from CaP by using 4

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M urea, 1 mM phosphate, or 1 mM thymidine in buffer (10 mM HEPES, pH 7.6). (D) FAM-T15

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(250 nM) adsorbed by 50 µg/mL CaP in 10 mM HEPES, pH 7.6 with different concentrations of

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NaCl.

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Poly-T and poly-G DNA inhibit the growth of CaP crystals. When a polymer is adsorbed on a

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growing inorganic crystal, it might affect its growth. This has been demonstrated for gold and

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silver nanoparticles using DNA.45-48 To study the effect of DNA on the synthesis of CaP, we first

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used the A30 DNA. The CaP appeared more agglomerated from TEM when synthesized without

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DNA (Figure 4A). By introducing the DNA before mixing Ca2+ and phosphate, the resulting CaP

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was better dispersed,25 and a higher DNA concentration yielded better dispersity (Figure 4B-D),

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which was also confirmed by DLS (Figure 4E-H). This can be attributed to the increased

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negative charges on the surface of CaP upon DNA adsorption (Figure S3). We also challenged

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the samples by adding NaCl, which screened the negative charges. With more DNA, the samples

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were more resistant to salt-induced aggregation (Figure 4E-H, red and blue bars).

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Figure 4. TEM micrographs of CaP synthesized with (A) 0 µM, (B) 7 µM, (C) 20 µM, and (D)

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60 µM A30 DNA. DLS histograms of CaP (50 µg/mL) synthesized with (E) 0 µM, (F) 7 µM, (G)

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20 µM, and (H) 60 µM A30 DNA in buffer (10 mM HEPES, pH 7.6 with 0, 10, and 100 mM

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NaCl). DNA was mixed with Ca2+ before adding phosphate.

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To study the effect of DNA sequence, each 30-mer homo-DNA was used. We observed

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that CaP grew more slowly in the presence of DNA, and this can be explained by DNA

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competing with phosphate ions for Ca2+.27 After 2 days, no precipitate was observed with G30 or

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T30 after centrifugation, indicating these sequences fully inhibited the growth (Figure 5D). On

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the other hand, A30 and C30 still produced CaP nanoparticles. The morphology of these CaP

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nanoparticles were observed by TEM (Figure 5A-C). For CaP synthesized without DNA or with

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A30 or C30, they appeared typical needle-like structures. DLS data indicates that both A30 and C30

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can enhance the dispersity of CaP (Figure 4E-H and Figure S4). X-ray diffraction indicates that

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the main components of these two materials are very similar, and the peaks could be assigned 13


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according to the standard spectrum from HAp (Figure 5E). Thus DNA does not affect the

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crystallinity of the CaP products. The broad diffraction peaks of these materials might be

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attributed to their nanoscale sizes.

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Poly-T DNA is adsorbed more tightly at high pH. It is interesting that T30 and G30 could fully

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inhibit the growth of CaP. From our adsorption capacity study, C30 was adsorbed more than T30

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or G30, and thus one would expect that C30 might have a stronger inhibition effect. A possible

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reason is that we measured DNA adsorption at neutral pH (Figure 3B), while CaP was

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synthesized at a basic pH. To explore the reason, we used phosphate to desorb FAM-labeled A30,

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T30 and C30 from CaP under neutral and basic condition, respectively. We did not try FAM-G30

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because of the difficulty in synthesizing this sequence. As shown in Figure 5F, the highest

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desorption was observed with A30 at pH 7.6, while C30 had the lowest desorption, which was

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consistent with our data in Figure 3B.

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When the desorption experiment was performed at pH 10.8 (Figure 5G), a pH close to

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our synthesis condition, > 60% A30 and ~ 24% C30 were desorbed even without adding phosphate,

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while almost no T30 desorbed under the condition. With 1 mM inorganic phosphate, A30 and C30

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fully desorbed, while T30 desorbed < 50%. This experiment indicated that the adsorption strength

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between DNA and CaP is strongly pH dependent. A30 has the weakest affinity to CaP under both

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neutral and basic conditions. Although C30 is adsorbed more strongly than T30 at neutral pH, T30

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is stronger at basic pH. This should be the reason why T30 inhibited the growth of CaP. The N3

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of thymine can be deprotonated with a pKa of 9.9, while the N1 on guanine can also be

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deprotonated with a pKa of 9.2. We suspect that these deprotonated bases may contribute to the

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tighter adsorption of DNA at basic pH. It was recently reported that G-rich DNA might be

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aptamers for CaP,26 and we showed here that poly-T and poly-G DNA are tight binders at high 14


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pH. At neutral pH, it appears that poly-C DNA binds CaP more strongly. Therefore, even though

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DNA is adsorbed mainly by its phosphate backbone, the base composition can also influence

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adsorption by deprotonation and by forming various secondary structures.

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Figure 5. TEM micrographs of CaP synthesized with (A) no DNA; (B) 60 µM A30; and (C) 60

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µM C30 DNA for 48 h. (D) A photograph showing the CaP products synthesized with 60 µM A30,

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C30, G30 and T30, and without DNA. No products were observed with G30 or T30. (E) Powder

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XRD spectra of CaP synthesized without and with 5 µM A30. The short lines at the bottom in

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blue are standard spectrum of HAp and the main diffraction peaks are assigned. DNA was added

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into calcium nitrate before mixing with ammonium phosphate monobasic at pH ~11. Percentage

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of desorbed FAM-labeled A30, T30 and C30 DNA from 50 µg/mL CaP (F) by 1 mM inorganic

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phosphate at pH 7.6, and (G) at pH 10.8 with or without 1 mM phosphate.

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DNA adsorption by other metal phosphates. After a careful study of the CaP system, and

2

understanding that Ca2+ was mainly responsible for DNA adsorption, we were curious about

3

other phosphate containing nanoparticles. We then synthesized ten types of metal phosphate

4

nanoparticles by co-precipitating each metal ion with phosphate. Most metal phosphates showed

5

distinct colors with various metal species (Figure 6A). We compared these nanoparticles (100

6

µg/mL) for adsorbing FAM-labeled T15 in buffer (10 mM HEPES, pH 7.6). As shown in Figure

7

6B, the fluorescence was quenched by the phosphates of nickel, copper and cobalt, indicating

8

DNA adsorption by these nanoparticles. Though strong fluorescence was still observed with the

9

calcium and cerium samples, the fluorescence was mainly in the pellets, suggesting that they

10

could adsorb DNA but were not good quenchers. For the rest samples, strong fluorescence

11

remained in the solution phase after centrifugation, and thus they could not effectively adsorb

12

DNA. Among them, we notice that manganese and iron did not form much precipitant with

13

phosphate, which might also explain their poor DNA adsorption (less than 20%) (Figure 6E,

14

black bars).

15

The ζ-potential of the samples were measured (Figure 6F). Interestingly, all the samples

16

with a low DNA adsorption efficiency (Fe3+, Zn2+, Mn2+, Ba2+ and Sr2+) were negatively charged.

17

This can be rationalized by that they can repel negatively charge DNA. On the other hand,

18

although cobalt phosphate was also negatively charged, it could effectively adsorb DNA.

19

Therefore, a negatively charged surface does not preclude strong DNA adsorption. Similar

20

examples are seen on negatively charged graphene oxide and gold nanoparticles for strong DNA

21

adsorption.10,11

22

To further compare their DNA adsorption, we probed adsorption stability by adding free

23

inorganic phosphate (2 mM, Figure 6C) or NaCl (100 mM, Figure 6D) to the adsorption 16


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complexes. After centrifugation, the supernatant fluorescence was measured to quantify desorbed

2

DNA. For cerium phosphate and copper phosphate, the fluorescence was recovered by phosphate

3

ions but not by NaCl. It is interesting to note that cerium phosphate can be positively charged

4

with a higher cerium ratio (Figure S5),49 while the surface charge of CaP is quite independent of

5

the Ca/P ratio. This might be explained by a much stronger affinity between Ce3+ and phosphate,

6

and thus the initial stoichiometry was reflected on the property of the final product. Calcium and

7

nickel phosphate samples showed DNA desorption by both phosphate and NaCl, suggesting that

8

electrostatic interaction with the metal ion is an important part of the adsorption force.

9 10

Figure 6. (A) A photograph of dispersions of the phosphate precipitants formed with Ce3+, Fe3+,

11

Ca2+, Ni2+, Zn2+, Mn2+, Ba2+, Cu2+, Sr2+, and Co2+. Fluorescence photographs of (B) 200 nM

12

FAM-T15 after incubating with 100 µg/mL of different metal phosphates for 1 h in 10 mM

13

HEPES (pH 7.6); (C) after adding 2 mM phosphate to the purified adsorption complexes; and (D)

14

after adding 100 mM NaCl. For (B-D), the samples were centrifuged for 15 min at 15000 rpm

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before taking the pictures. (E) Quantification of the adsorbed or desorbed DNA in (B-D). (F) ζ-

2

potential of the metal phosphates (100 µg/mL) in 10 mM HEPES, pH 7.6.

3

It is interesting to note that the fluorescence is not recovered from cobalt phosphate either

4

by phosphate ion or by NaCl, suggesting its strongly adsorbing DNA. We previously also

5

observed strong DNA adsorption by CoO,37,

6

responsible for the tight DNA adsorption. Therefore, both the surface charge and the chemistry

7

of the metal species are important for DNA adsorption. DNA is a polyphosphate, and studying

8

its adsorption on inorganic phosphate salt is an interesting biointerface problem.

50

and it is likely that the cobalt species is

9

10

Conclusions

11

In summary, we systematically studied the interaction between short single-stranded DNA

12

oligonucleotides and calcium phosphate (CaP) nanoparticles. Being a traditional nanomaterial

13

for DNA delivery, its application might be further improved by understanding its fundamental

14

interaction with DNA. Using fluorescently labeled oligonucleotides, we studied DNA adsorption

15

isotherm. A Langmuir type of isotherm was obtained suggesting monolayer DNA adsorption.

16

We also observed dissolution of CaP at low CaP concentrations, leading to a calculated solubility

17

limit of 14.2 µg/mL. Longer DNA is adsorbed more strongly, and poly-C DNA is adsorbed more

18

than the other three DNA homopolymers at neutral pH, while poly-T and poly-G DNAs are

19

adsorbed more tightly at basic pH. Desorption experiments were carried out using concentrated

20

urea, thymidine and inorganic phosphate, and desorption was observed only in the presence of

21

phosphate, suggesting that DNA uses its phosphate backbone to interact with the CaP surface.

22

Adsorption is also decreased by raising the NaCl concentration suggesting the electrostatic 18


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nature of interaction. DNA adsorption in general has reduced the aggregation of CaP. DNA can

2

slow down the growth of CaP nanocrystals, and especially poly-T and poly-G DNA nearly fully

3

inhibited the growth. To further broaden the scope of this study, we synthesized ten different

4

metal phosphate materials (Ce3+, Fe3+, Ca2+, Ni2+, Zn2+, Mn2+, Ba2+, Cu2+, Sr2+, Co2+), and their

5

DNA adsorption was found to be related to surface charge. The fundamental insights obtained

6

from this work might be useful for a number of important applications such as gene delivery,

7

biomineralization and DNA directed assembly of nanomaterials.

8

9

Acknowledgement

10

Funding for this work was from The Natural Sciences and Engineering Research Council of

11

Canada (NSERC). L. Wang was supported by National Natural Science Foundation of China

12

(No. 31571918) and the Program of Supporting Graduate Students Studying Abroad by Zhejiang

13

University. The authors thank for Q. Pang for help in the XRD experiment.

14

15

Supporting Information

16

The Supporting Information is available free of charge on the ACS Publication website at DOI:

17

xxxxxxx.

18

DNA sequences used in this work (Table S1); adsorption of 24-mer random ssDNA and

19

dsDNA (Figure S1); DNA desorption in different concentrations of NaCl (Figure S2); ζ-

20

potential of CaP (50 µg/mL) synthesized with different concentrations of DNA (Figure S3);

21

DLS histograms of CaP (50 µg/mL) synthesized with 60 µM C30 DNA (Figure S4); and the 19


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effect of the ratio of phosphate to cerium and pH on the ζ-potential of cerium phosphate

2

(Figure S5).

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References

2

(1) Giljohann, D. A.; Seferos, D. S.; Daniel, W. L.; Massich, M. D.; Patel, P. C.; Mirkin, C. A.

3

Gold Nanoparticles for Biology and Medicine. Angew. Chem., Int. Ed. 2010, 49, 3280-3294.

4

(2) Jones, M. R.; Seeman, N. C.; Mirkin, C. A. Programmable Materials and the Nature of the

5

DNA Bond. Science 2015, 347, 1260901.

6

(3) Tan, L. H.; Xing, H.; Lu, Y. DNA as a Powerful Tool for Morphology Control, Spatial

7

Positioning, and Dynamic Assembly of Nanoparticles. Acc. Chem. Res. 2014, 47, 1881-1890.

8

(4) Rosi, N. L.; Mirkin, C. A. Nanostructures in Biodiagnostics. Chem. Rev. 2005, 105, 1547-

9

1562.

10

(5) Liu, J.; Cao, Z.; Lu, Y. Functional Nucleic Acid Sensors. Chem. Rev. 2009, 109, 1948-1998.

11

(6) Zhou, W.; Saran, R.; Liu, J. Metal Sensing by DNA. Chem. Rev. 2017, 117, 8272-8325.

12

(7) Wang, H.; Yang, R.; Yang, L.; Tan, W. Nucleic Acid Conjugated Nanomaterials for

13

Enhanced Molecular Recognition. ACS Nano 2009, 3, 2451-2460.

14

(8) Song, S.; Qin, Y.; He, Y.; Huang, Q.; Fan, C.; Chen, H.-Y. Functional Nanoprobes for

15

Ultrasensitive Detection of Biomolecules. Chem. Soc. Rev. 2010, 39, 4234-4243.

16

(9) Zhao, W.; Brook, M. A.; Li, Y. Design of Gold Nanoparticle-Based Colorimetric Biosensing

17

Assays. ChemBioChem 2008, 9, 2363-2371.

18

(10) Liu, B.; Salgado, S.; Maheshwari, V.; Liu, J. DNA Adsorbed on Graphene and Graphene

19

Oxide: Fundamental Interactions, Desorption and Applications. Curr. Opin. Colloid Interface Sci.

20

2016, 26, 41-49.

21

(11) Liu, J. Adsorption of DNA onto Gold Nanoparticles and Graphene Oxide: Surface Science

22

and Applications. Phys. Chem. Chem. Phys. 2012, 14, 10485-10496.

21


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 27

1

(12) Pautler, R.; Kelly, E. Y.; Huang, P.-J. J.; Cao, J.; Liu, B.; Liu, J. Attaching DNA to

2

Nanoceria: Regulating Oxidase Activity and Fluorescence Quenching. ACS Appl. Mater.

3

Interfaces 2013, 5, 6820-6825.

4

(13) Lee, D.; Upadhye, K.; Kumta, P. N. Nano-Sized Calcium Phosphate (CaP) Carriers for

5

Non-Viral Gene Deilvery. Mater. Sci. Eng., B 2012, 177, 289-302.

6

(14) Uskoković, V.; Uskoković, D. P. Nanosized Hydroxyapatite and Other Calcium Phosphates:

7

Chemistry of Formation and Application as Drug and Gene Delivery Agents. J. Biomed. Mater.

8

Res. B: Appl. Biomater. 2011, 96B, 152-191.

9

(15) Ginebra, M. P.; Traykova, T.; Planell, J. A. Calcium Phosphate Cements as Bone Drug

10

Delivery Systems: A Review. J. Control Release 2006, 113, 102-110.

11

(16) Vallet-Regí, M.; González-Calbet, J. M. Calcium Phosphates as Substitution of Bone

12

Tissues. Prog. Solid State Chem. 2004, 32, 1-31.

13

(17) Bose, S.; Tarafder, S. Calcium Phosphate Ceramic Systems in Growth Factor and Drug

14

Delivery for Bone Tissue Engineering: A Review. Acta Biomater. 2012, 8, 1401-1421.

15

(18) Dorozhkin, S. V. Bioceramics of Calcium Orthophosphates. Biomaterials 2010, 31, 1465-

16

1485.

17

(19) Dorozhkin, S. V. Calcium Orthophosphates. J. Mater. Sci. 2007, 42, 1061-1095.

18

(20) Dorozhkin, S. V.; Epple, M. Biological and Medical Significance of Calcium Phosphates.

19

Angew. Chem., Int. Ed. 2002, 41, 3130-3146.

20

(21) Jordan, M.; Schallhorn, A.; Wurm, F. M. Transfecting Mammalian Cells: Optimization of

21

Critical Parameters Affecting Calcium-Phosphate Precipitate Formation. Nucleic Acids Res.

22

1996, 24, 596-601.

22


Page 23 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

1

(22) Anissi, J.; El Hassouni, M.; Ouardaoui, A.; Sendide, K. A Simple Method for Large-Scale

2

Purification of Nucleic Acids from Plants Using Calcium Phosphate-Type Monetite. Process.

3

Biochem. 2017, 52, 259-266.

4

(23) Andrews-Pfannkoch, C.; Fadrosh, D. W.; Thorpe, J.; Williamson, S. J. Hydroxyapatite-

5

Mediated Separation of Double-Stranded DNA, Single-Stranded DNA, and RNA Genomes from

6

Natural Viral Assemblages. Appl. Environ. Microb. 2010, 76, 5039-5045.

7

(24) Sokolova, V. V.; Radtke, I.; Heumann, R.; Epple, M. Effective Transfection of Cells with

8

Multi-Shell Calcium Phosphate-DNA Nanoparticles. Biomaterials 2006, 27, 3147-3153.

9

(25) Sokolova, V.; Kovtun, A.; Prymak, O.; Meyer-Zaika, W.; Kubareva, E. A.; Romanova, E.

10

A.; Oretskaya, T. S.; Heumann, R.; Epple, M. Functionalisation of Calcium Phosphate

11

Nanoparticles by Oligonucleotides and Their Application for Gene Silencing. J. Mater. Chem.

12

2007, 17, 721-727.

13

(26) Baillargeon, K.; Meserve, K.; Faulkner, S.; Watson, S.; Butts, H.; Deighan, P.; Gerdon, A.

14

Precipitation Selex: Identification of DNA Aptamers for Calcium Phosphate Materials Synthesis.

15

Chem. Commun. 2017, 53, 1092-1095.

16

(27) Okazaki, M.; Yoshida, Y.; Yamaguchi, S.; Kaneno, M.; Elliott, J. C. Affinity Binding

17

Phenomena of DNA onto Apatite Crystals. Biomaterials 2001, 22, 2459-2464.

18

(28) Zuo, G.; Wan, Y.; Meng, X.; Zhao, Q.; Ren, K.; Jia, S.; Wang, J. Synthesis and

19

Characterization of a Lamellar Hydroxyapatite/DNA Nanohybrid. Mater. Chem. Phys. 2011, 126,

20

470-475.

21

(29) Wan, Y.; Wu, C.; Zuo, G.; Xiong, G.; Jin, J.; Guo, R.; Wang, Z.; Luo, H. Controlled

22

Template Synthesis of Lamellar Hydroxyapatite Nanoplates as a Potential Carrier for Gene

23

Delivery. Mater. Chem. Phys. 2015, 156, 238-246. 23


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 27

1

(30) Revilla-López, G.; Casanovas, J.; Bertran, O.; Turon, P.; Puiggalí, J.; Alemán, C. Modeling

2

Biominerals Formed by Apatites and DNA. Biointerphases 2013, 8, 10.

3

(31) Bertran, O.; del Valle, L. J.; Revilla-Lopez, G.; Chaves, G.; Cardus, L.; Casas, M. T.;

4

Casanovas, J.; Turon, P.; Puiggali, J.; Aleman, C. Mineralization of DNA into Nanoparticles of

5

Hydroxyapatite. Dalton Trans. 2014, 43, 317-327.

6

(32) Ngourn, S. C.; Butts, H. A.; Petty, A. R.; Anderson, J. E.; Gerdon, A. E. Quartz Crystal

7

Microbalance Analysis of DNA-Templated Calcium Phosphate Mineralization. Langmuir 2012,

8

28, 12151-12158.

9

(33) Loo, S. C. J.; Siew, Y. E.; Ho, S.; Boey, F. Y. C.; Ma, J. Synthesis and Hydrothermal

10

Treatment of Nanostructured Hydroxyapatite of Controllable Sizes. J. Mater. Sci. Mater. Med.

11

2008, 19, 1389-1397.

12

(34) Zhang, X.; Servos, M. R.; Liu, J. Surface Science of DNA Adsorption onto Citrate-Capped

13

Gold Nanoparticles. Langmuir 2012, 28, 3896-3902.

14

(35) Wu, M.; Kempaiah, R.; Huang, P.-J. J.; Maheshwari, V.; Liu, J. Adsorption and Desorption

15

of DNA on Graphene Oxide Studied by Fluorescently Labeled Oligonucleotides. Langmuir 2011,

16

27, 2731-2738.

17

(36) Lu, C.; Huang, P.-J. J.; Liu, B.; Ying, Y.; Liu, J. Comparison of Graphene Oxide and

18

Reduced Graphene Oxide for DNA Adsorption and Sensing. Langmuir 2016, 32, 10776-10783.

19

(37) Liu, B.; Liu, J. Comprehensive Screen of Metal Oxide Nanoparticles for DNA Adsorption,

20

Fluorescence Quenching, and Anion Discrimination. ACS Appl. Mater. Interfaces 2015, 7,

21

24833-24838.

24


Page 25 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

1

(38) Wu, M.; Kempaiah, R.; Huang, P.-J.J.; Maheshwari, V.; Liu, J. Adsorption and Desorption

2

of DNA on Graphene Oxide Studied by Fluorescently Labeled Oligonucleotides. Langmuir 2011,

3

27, 2731–2738.

4

(39) Properties of the Elements and Inorganic Compounds. In CRC Handbook of Chemistry and

5

Physics, 85 ed.; Lide, D. R., Ed. CRC Press: Boca Raton, FL, 2005; pp 4-49.

6

(40) Ma, L.; Liu, B.; Huang, P.-J. J.; Zhang, X.; Liu, J. DNA Adsorption by ZnO Nanoparticles

7

near Its Solubility Limit: Implications for DNA Fluorescence Quenching and Dnazyme Activity

8

Assays. Langmuir 2016, 32, 5672-5680.

9

(41) Pei, H.; Li, F.; Wan, Y.; Wei, M.; Liu, H.; Su, Y.; Chen, N.; Huang, Q.; Fan, C. Designed

10

Diblock Oligonucleotide for the Synthesis of Spatially Isolated and Highly Hybridizable

11

Functionalization of DNA–Gold Nanoparticle Nanoconjugates. J. Am. Chem. Soc. 2012, 134,

12

11876-11879.

13

(42) Opdahl, A.; Petrovykh, D. Y.; Kimura-Suda, H.; Tarlov, M. J.; Whitman, L. J. Independent

14

Control of Grafting Density and Conformation of Single-Stranded DNA Brushes. Proc. Natl.

15

Acad. Sci. U.S.A. 2007, 104, 9-14.

16

(43) Lu, C.; Huang, Z.; Liu, B.; Liu, Y.; Ying, Y.; Liu, J. Poly-Cytosine DNA as a High-Affinity

17

Ligand for Inorganic Nanomaterials. Angew. Chem., Int. Ed. 2017, 56, 6208-6212.

18

(44) Banik, M.; Basu, T. Calcium Phosphate Nanoparticles: A Study of Their Synthesis,

19

Characterization and Mode of Interaction with Salmon Testis DNA. Dalton Trans. 2014, 43,

20

3244-3259.

21

(45) Tan, L. H.; Yue, Y.; Satyavolu, N. S. R.; Ali, A. S.; Wang, Z.; Wu, Y.; Lu, Y. Mechanistic

22

Insight into DNA-Guided Control of Nanoparticle Morphologies. J. Am. Chem. Soc. 2015, 137,

23

14456-14464. 25


Langmuir 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 27

1

(46) Shen, J.; Xu, L.; Wang, C.; Pei, H.; Tai, R.; Song, S.; Huang, Q.; Fan, C.; Chen, G.

2

Dynamic and Quantitative Control of the DNA-Mediated Growth of Gold Plasmonic

3

Nanostructures. Angew. Chem., Int. Ed. 2014, 53, 8338-8342.

4

(47) Wu, J.; Tan, L. H.; Hwang, K.; Xing, H.; Wu, P.; Li, W.; Lu, Y. DNA Sequence-Dependent

5

Morphological Evolution of Silver Nanoparticles and Their Optical and Hybridization Properties.

6

J. Am. Chem. Soc. 2014, 136, 15195-15202.

7

(48) Li, J.; Zhu, Z.; Liu, F.; Zhu, B.; Ma, Y.; Yan, J.; Lin, B.; Ke, G.; Liu, R.; Zhou, L.; Tu, S.;

8

Yang, C. DNA-Mediated Morphological Control of Silver Nanoparticles. Small 2016, 12, 5449-

9

5487.

10

(49) Lopez, A.; Zhang, Y.; Liu, J. Tuning DNA Adsorption Affinity and Density on Metal Oxide

11

and Phosphate for Improved Arsenate Detection. J. Colloid Interf. Sci. 2017, 493, 249-256.

12

(50) Liu, J.; Liu, B.; Ma, L.; Huang, Z.; Hu, H.; Wu, P. Janus DNA Orthogonal Adsorption of

13

Graphene Oxide and Metal Oxide Nanoparticles Enabling Stable Sensing in Serum. Mater.

14

Horizons 2017, DOI: 10.1039/C7MH00804J.

15

16

17

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