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Gold Nanoflower for Selective Detection of Single Arginine Effect in #-helix Conformational Change over Lysine in 310-helix Peptide Shahbaz Ahmad Lone, and Kalyan K. Sadhu Bioconjugate Chem., Just Accepted Manuscript • DOI: 10.1021/acs.bioconjchem.9b00301 • Publication Date (Web): 01 May 2019 Downloaded from http://pubs.acs.org on May 2, 2019

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Bioconjugate Chemistry

Gold Nanoflower for Selective Detection of Single Arginine Effect in -helix Conformational Change over Lysine in 310-helix Peptide Shahbaz Ahmad Lone,† Kalyan K. Sadhu,*,† †Department

of Chemistry, Indian Institute of Technology Roorkee, Roorkee-247667, Uttarakhand, India

ABSTRACT: Hydroxylamine based growth reaction in presence of natural L-amino acids (9 mM) and gold nanoparticle seed mostly produce aggregated or non-aggregated gold nanostructures except the cases of immediate precipitation with aspartic acid, glutamic acid, cysteine and tyrosine. Among the other amino acids, arginine shows the control growth reaction to form gold nanoflower from gold nanoparticle seeds, which have been pre-incubated with amine modified DNA (NH2-oln). The absorbance trend with NH2-oln in presence of arginine is similar to the aggregation behavior in presence of histidine and methionine. The formations of gold nanoflower with arginine and aggregation due to histidine and methionine in presence of NH2-oln have been sorted out with lower concentration (50 M) of these amino acids. This observation has been successfully transferred to differentiate 310helical Ac-(AAAAK)3A-NH2 from -helical Ac-(AAAAR)3ANH2. The concept has been further applied for the detection of single arginine modification closest to the carboxy terminus of 310-helical Ac-(AAAAK)3A-NH2 peptide for maximum conformational change towards -helix. KEYWORDS: DNA, arginine, growth reaction, nanoflower, peptide INTRODUCTION Gold nanoparticle are useful detecting tools for biomolecules in contemporary research.1 Nanopore has been used recently for the sensing of proteins in the single molecular level.2 Interaction between gold nanoparticle and DNA has been well explored within last two decades.3 Recently, transfer of DNA patterns from 3D-DNA nanostructures to gold nanoparticle has been reported.4 Among the DNA based gold nanoarchitectures, gold nanoflower shows important biological application such as surface-enhanced Raman scattering,5 which has been further exploited to live cell imaging. DNA stabilized gold nanoparticle has been modified to gold nanoflower architecture, where small DNA sequence has been used to staple big DNA scaffold.6 Formation mechanism of gold nanoflower with DNA sequence was studied in detail and this nanoflower had been explored in dark field microscopy for cells.7 Nam and coworkers showed the selective role of amine functionalized organic molecule in the development of complex concave rhombic dodecahedral gold nanoarchitecture even in presence of thiol functional group.8 In recent times gold nanoflower, originated from diverse pathways, have shown biological applications such as imaging of cellular alkaline phosphate,9 in vivo inhibition of bacteria.10 We have also compared the role of gold nanoflower and nanosphere in the detection of target DNA sequence.11 Quercetin functionalized gold nanoparticle has been successfully explored for the detection of arginine, histidine and lysine without any selectivity.12 Dicoumarol and sodium chloride have been treated separately for the detection of cysteine by aggregation of gold nanoparticle.13 In 2018, Lee et.

al. have developed chiral plasmonic gold nanoparticle from cubic seed controlled by amino acid and peptides.14 The same group have also shown the growth of gold nanoparticle in presence of peptide sequence containing five amino acids.15 Till date, the biomolecule detection technology by gold nanoparticle solely depends on interactions of gold nanoparticle with either biomolecule or DNA or amino acids. However, so far gold nanoparticle has not been reconnoitered in the biomolecule detection process, where interactions between two biomolecules such as DNA and amino acids or peptides play a major role. In our current effort, we have developed gold nanoflower from spherical gold nanoparticle seed with the help of amino acids and amine modified DNA. This has been further applied to differentiate the 310-helical and -helical peptides containing lysine and arginine respectively. The translocation of peptide through cell membrane is observed in the case of arginine rich peptide.16 In the same study, it has been reported that the replacement of arginine with lysine do not show translocation. However, Wu’s group has shown the role of CGC nucleic bases at the end of the positively charged miniproteins containing either arginine or lysine for the equal uptake due to thiol-disulfide exchange on the cell surface.17 Not only the uptake of peptide but also the release of peptide from late endosome to cytosol depends upon the threshold concentration of arginine in the peptide sequence.18 Too high concentration of arginine does not release the peptides from late endosomes. The detection of arginine in peptide sequence is an active area of research over two decades. Among the arginine detection technique in peptide sequence, capillary

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electrophoresis and laser induced fluorescence was introduced to enhance the

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Au(III) salt and hydroxyl amine for the growth reaction (Figure 1A). Among all the natural amino acids, Asp, Glu, Cys

Scheme 1. The role of amine modified DNA (NH2-oln) based gold nanoflower for the detection of arginine containing peptide via the growth controlled reactions of gold nanoparticle seed. sensitivity of the benzoin based fluorogenic detection process.19 Monolithic HPLC followed by chemiluminescence had been used for separation of arginine containing peptide.20 Aerolysin nanopore has been utilized very recently to calculate the number of arginine residue within the uniformly charged homopolymeric peptide.21 The substitution of lysines by arginines of 310-helical Ac-(AAAAK)3A-NH2 (KKK) peptide lead to the formation of the -helical Ac-(AAAAR)3A-NH2 (RRR) peptide.22 We have developed gold nanoflower for the detection of this arginine substitution in peptide (Scheme 1), which is responsible for the structural change in the parent peptide. The strong interaction between arginine and DNA has explored its usage as positively charged amino acid in protamines for DNA packaging.23 The other positively charge amino acids such lysine and ornithine have not been found useful. In our current study, we have explored the preferable interaction between arginine and amine modified 8-mer DNA sequence to develop an easy technique for the detection of helical peptide sequence RRR, where all the lysines of 310helical KKK peptide have been replaced with arginine (Scheme 1). Moreover, the methodology has been extended to the AcAAAAKAAAAKAAAARA-NH2 (KKR) peptide, where single lysine has been replaced with arginine closest to the carboxy terminal. We have compared this observation with other two control peptides Ac-AAAARAAAAKAAAAKA-NH2 (RKK) and Ac-AAAAKAAAARAAAAKA-NH2 (KRK). The conformational change in the helicity due to single arginine substitution at lysine residue22 plays the crucial role in the detection process. RESULTS AND DISCUSSION In order to develop a tool for selective arginine detection among other amino acids, we have tested the growth dependent strategy7 of gold nanoparticle synthesis. We have tested all the natural amino acids for the same purpose. Initially gold nanoparticle seeds (16±3 nm) have been prepared with standard citrate reduction method.11 We have used 675  108 per mL seed amount in all the cases for growth reactions in presence of amino acids. The seed nanoparticles have been incubated with 9 mM amino acid solutions for 30 minutes before the treatment of

Figure 1. A) Scheme for L-amino acid (9 mM) based growth reactions to form instantaneous precipitation, aggregated and non-aggregated gold nanoparticles; representative absorbance spectra of B) non-aggregated (left) and aggregated (right) gold nanoparticle in presence of different amino acids.

Figure 2. TEM images of aggregated or non-aggregated gold nanoparticles after the growth reaction in presence of A) Lys, B) Leu, C) Arg and D) Phe. Scale bar: 100 nm. and Tyr show the instantaneous precipitation after the growth reaction (Figure S1). Arg, His, Ser, Phe, Met and Trp show blue color solution after the growth reaction (Figure 1B). Red color

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Bioconjugate Chemistry solutions have been obtained for the remaining amino acids (Figure 1B). The TEM (Transmission Electron

order of water mediated bonding interaction between amino acids and DNA backbone follows the order

Scheme 2. The proposed mechanism of selective formation of nanoflower after the growth reaction in presence of Arg due to the highly specific hydrogen bonding interaction between DNA and Arg.

Figure 3. A) Scheme for NH2-oln (0.6 M) and L-amino acid (9 mM) based growth reactions to form aggregated and nonaggregated gold nanoparticles; B) absorbance spectra of aggregated gold nanoparticle in presence of Arg, Met and His and non-aggregated gold nanoparticles in presence of Phe and Ser. Microscopy) images from the solutions after growth reaction in presence of different amino acids show different extent of nonaggregated and aggregated gold nanoparticle (Figure 2 and S2). This result shows clear difference between Arg and Lys in the growth reaction. The hydrodynamic radii have further confirmed the aggregations after the growth reaction in presence of selected amino acids (Figure S3). However, the growth reaction at this stage for the detection of Arg is not selective. In order to introduce selectivity among the Arg, His, Ser, Phe, Met and Trp, we have introduced 8-mer amine modified DNA (NH2-oln) sequence before the incubation with these five amino acids (Figure 3A). We have recently studied this 8-mer DNA sequence for the selective formation of gold nanoflower.11 In this current study, we have experimentally explored the theoretical concept24 of different types of weak interactions between DNA and amino acids. The major stability of DNA and amino acids combination depends upon van der Waals interactions, which do not vary too much for Lys or Arg. In addition to the van der Waals interactions between DNA and amino acids, two other weak interactions, such as hydrogen bonding and water-mediated bonds, play an important role in the specificity24 of DNA and amino acid combination (Fig. 3A and Scheme 2). The order of hydrogen bonding interaction between amino acids and DNA backbone follows the order Arg>>Lys>Ser>Thr≈Asn>Gln>Gly≈His≈Tyr> Ala.24 The

Figure 4 TEM images of aggregated or non-aggregated gold nanoparticles after the growth reaction in presence of NH2-oln A) Phe, B) Ser, C) Arg and D) His. Scale bar: 100 nm. Arg>>Lys>Asn≈ Ser>Thr≈Gln> Tyr≈Ala≈Gly≈His.24 We have tried to explore these highly specific weak interactions between arginine and DNA in our strategy. Before the incubation with 9 mM amino acids, 0.6 M NH2-oln has been incubated with seed solution for 30 min. In the case of Phe, Ser and Trp red color solutions have been obtained during the growth reactions after the combined treatment of NH2-oln and amino acids (Figure 3B). However, in the case of Arg and Met the solution is still blue color even after the treatment of NH2oln (Figure 3B). In the case of His, the solution shows dual peak with low intensity (Figure3B). It is noteworthy to mention that all other amino acids results in either precipitation or red color after the growth reaction in presence of NH2-oln (Figure S4 and S5). The polydispersity index (PDI) values after the growth



reaction significantly decreases in presence of NH2-oln with respect the data obtained without NH2-oln

Figure 5 A) Normalized absorbance after the growth reaction in presence of Arg, His and Met (50 M) and NH2-oln (0.6 M); B-D) TEM images of gold nanoflower and spherical gold nanoparticles after the growth reaction in presence of Arg, His and Met. Scale bar for B-D: 100 nm. (Figure S6). The selectivity of arginine for nanoflower formation has been further checked via broadening of absorption peak in presence of relevant metal ions (Na+, K+, Ca2+, Mg2+, Mn2+, Fe2+, Fe3+, Co2+, Ni2+, Cu2+ and Zn2+), anions (Cl–, PO43–, F–and CH3CO2–), biomolecules (glutathione – reduced and oxidized forms) and slightly acidic to basic pH buffer close to physiological pH 7.4 (Figure S7 and S8). The TEM images of the solutions obtained from growth reactions after the treatment of NH2-oln and Arg (Figure 4) show the gold nanoflower architecture. The gold nanoflower, which is generally obtained after growth reaction with NH2-oln sequence,11 cannot form in presence of other amino acids. The strong interaction between Arg and NH2-oln sequence is responsible for the formation of the nanoflower. In the case of Phe, Lys, Leu, Asn and Ser (Figure 4A-B and S8), the excess amount of amino acids can replace the NH2-oln from the gold nanoparticle surface. Therefore, gold nanoflower cannot be obtained after the growth reactions from the combination of NH2-oln with these amino acids. However, in the case of His and Met, there are aggregation of gold nanoparticle after the growth reaction (Figure 4D and S9). The strategy requires further improvement in order to develop selective detection of Arg via growth mechanism. We have lowered the concentration of amino acids to 50 M after the treatment with 0.6 M NH2-oln. At this low concentration of amino acids, we have followed the same strategy for the growth reaction. Interestingly, within Arg, His and Met, blue color solution has been only obtained from Arg case. The absorbance of this blue solution (Figure 5A) is broad in natureand is similar to the earlier report of gold nanoflower

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solution.7 In the case of His and Met, red color solutions (Figure 5A) of non-aggregated gold nanoparticle (Figure 5C-D) have been obtained. The TEM images show the formation of gold

Figure 6 A) Change of absorption maxima wavelength after the growth reactions in presence of 0.6 M NH2-oln and different concentration of peptides and (inset) the color of the solutions after the growth reaction with 3 M peptide (KKR, RRR and KKK) concentration and B-D) TEM images of gold nanoflower and spherical gold nanoparticles after the growth reaction in presence of 3 M peptides KKK, RRR and KKR. Scale bar for B-D: 100 nm nanoflower only in the Arg (Figure 5B). The combination of 0.6 M NH2-oln and 50 M of remaining amino acids produce red color solution (Figure S10). The surface charge (-potential) of the growth-controlled nanoparticle in presence of NH2-oln and 50 M concentration of amino acids are almost the same (Figure S11). However, Met showed different behavior in high concentration probably due to some favorable interaction between thio ether functional group and gold nanoparticle. The gold nanoflower based selective detection of Arg from the growth reaction in presence of NH2-oln has then been further extended to the determination of Arg in peptide sequence. The positive charge in Arg is mostly compared with Lys residue in terms of cellular as well as cytosolic entry of peptide containing these amino acids. Therefore we have targeted two peptide sequences KKK and RRR, where three Lys residues in one peptide have been replaced with three Arg residues. Interestingly, these three changes in the amino acid residues not only maintain the charge uniformity of the peptide sequence but also show two completely different structural configurations, 310-helical configuration with three Lys and helix configuration with three Arg in the peptide sequences.22 The same report showed the increasing global helicity of the peptide series in the order of KKK < RKK < KRK < KKR < RRR on the basis of circular dichroism data. We have chosen RKK, KRK and KKR, where the substitution closest to the


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Bioconjugate Chemistry carboxy terminal in KKR is the major factor in the change of helical configuration.22 We have checked the formation of gold nanoflower from the combination of 0.6 M NH2-oln and 0.5 M to 3 M range of five peptides KKK, RKK, KRK, KKR and RRR. Like the previous cases, we have first incubated the gold nanoparticle seed with 0.6 M NH2-oln for 30 min. This mixture has been further incubated with peptides for another 30 min before performing the growth reaction with hydroxylamine and Au(III) salt. The solution color changes from red to blue with increasing concentration of either KKR or RRR (Figure 6A, inset). The changes in the absorption maxima have been plotted for these five peptides (Figure 6A and S12). This plot confirms the detection of single arginine substitution to lysine during the helical conformational change. In the case of RKK and KRK, the color has been shifted from red to violet (Figure 6A) and confirmed the gradual change in color due to the change in peptide configuration. This change of peptide configuration even after the growth reactions have been further analyzed with circular dichroism (CD) data at 195 to 255 nm (Figure S13). The structural change of the peptides from KKK, KKR and RRR are clear from the mean residual ellipticity of CD spectra at 222 nm. However, the change of ellipticity for RKK, KRK and KKR are close to each other. This trend is similar to the ellipticity of the free peptides (Figure S14). The limit of detection for KKR peptide is 0.22 M via this growth analysis. The hydrodynamic radii after growth reaction increase in presence of increasing concentration of the peptides (Figure S15). Maximum enhancement of hydrodynamic radius has been observed in the case of RRR peptide. The PDI of the solution after the growth reaction decreases with increasing concentration of the peptides (Figure S16). However, the potentials of the gold nanoparticles after the growth reaction are almost constant in all these peptides (Figure S17). In the case of KKK, gold nanosphere has been observed in TEM image (Figure 6B). The formations of gold nanoflowers in presence of RRR and KKR have been also confirmed from TEM images (Figure 6C-D). CONCLUSION In summary, we have developed a gold nanoflower based strategy to detect the substitution of Lys to Arg in the peptide sequence. The interference from other amino acids has been sequentially nullified and the detection of the peptide has been performed within 3 M concentration range. The detection strategy has been guided by the strongest interaction between arginine and DNA sequence. The amine modified DNA sequence has been chosen for its unique property of gold nanoflower formation during the growth reaction in presence of gold nanoparticle seed. We have further explored the methodology for the single substitution of Lys by Arg in the peptide sequence. We are currently exploring the possibility of detection of single Lys to Arg substitution in a peptide of more than 50 mixed amino acid sequence. EXPERIMENTAL SECTION Materials. All the oligonucleotides used in the study were purchased from the GeneX India Bioscience Pvt. Ltd. Hydrogen

tetrachloroaurate (III) hydrate (HAuCl4.3H2O), metal perchlorate salts and HEPES (4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid) were purchased from the Sigma-Aldrich, Hydroxylamine hydrochloride (NH2OH.HCl) and glutathione (oxidized and reduced forms) were purchased from SISCO Research Laboratories, Sodium hydroxide were purchased from Thomas Baker and trisodium citrate dihydrate was purchased from Merck chemicals. L-Amino acids were purchased for Himedia Laboratories Pvt. Ltd. The peptides were purchased from GL Biochem (Shanghai) Ltd. Tetra-n-butyl ammonium salts of acetate, phosphate and fluoride were purchased from Alfa aesar. The amino acids solutions were prepared in a 1: 1 mixture of ethanol and water. Aspartic acid, Glutamic acid and tyrosine were prepared in 1: 1 mixture of ethanol and 1N HCl, where as cysteine was prepared in 1N HCl. Amino acids at low concentration were prepared by taking stock from high concentration and diluting in Millipore water. The peptide solutions were prepared in pure Millipore water. Synthesis of seed stock solution. The seed solution was prepared as previously mentioned.11 Growth reactions of gold nanoparticles with L-amino acids. 675  108 per mL gold nanoparticles seed solutions were incubated with 9 mM amino acid for 30 minutes. 3 μL 200 mM NH2OH (adjusted to pH 5 with NaOH) was added to these solutions and stirred vigorously for 10 minutes. 5 μL of 0.8% (w/v) HAuCl4 was added to these solutions to initiate the reduction reaction. The final volume in all reactions was maintained at 340L. The color change was observed within seconds. Growth reactions of gold nanoparticles with NH2-oln and L-amino acids. 675  108 per mL gold nanoparticles seed solutions were incubated with 0.6 μM DNA for 30 minutes. 9 mM amino acid was added and further incubated for 30 minutes. 3 μL 200 mM NH2OH (adjusted to pH 5 with NaOH) was added to these solutions and stirred vigorously for 10 minutes. 5 μL of 0.8% (w/v) HAuCl4 was added to these solutions to initiate the reduction reaction. The final volume in all reactions was maintained at 340L. The color change was observed within seconds. Growth reactions of gold nanoparticles with NH2-oln and L-amino acidsat low concentration. 675  108 per mL gold nanoparticles seed solutions were incubated with 0.6 μM DNA for 30 minutes. 50 M amino acid was added and further incubated for 30 minutes. 3 μL 200 mM NH2OH (adjusted to pH 5 with NaOH) was added to these solutions and stirred vigorously for 10 minutes. 5 μL of 0.8% (w/v) HAuCl4 was added to these solutions to initiate the reduction reaction. The final volume in all reactions was maintained at 340L. The color change was observed within seconds. Growth reactions of gold nanoparticles with NH2-oln and peptide. 675  108 per mL gold nanoparticles seed solutions were incubated with 0.6 μM DNA for 30 minutes. Peptide (0.5M, 1 M. 2 M or 3 M) were added and further incubated for 30 minutes. 3 μL 200 mM NH2OH (adjusted to pH 5 with NaOH) was added to these solutions and stirred vigorously for 10 minutes. 5 μL of 0.8% (w/v) HAuCl4 was added to these solutions to initiate the reduction reaction. The final volume in all reactions was maintained at 340L. The color change was observed within seconds.



Selectivity in presence of metal ions, anions and biologically important molecules. 675  108 per mL gold nanoparticles seed solution were incubated with 0.6 M NH2oln for 30 minutes. 50 M arginine were added and further incubated for 30 minute. 20 M of metal ions, anion, glutathione were added and further incubated for 30 minutes. 3 L 200 mM NH2OH was added to these solutions and stirred vigorously for 10 minutes. 5 L of 0.8% (w/v) HAuCl4 was added to these solutions to initiate the reduction reaction. The final volume in all reactions was maintained at 340L. The color change was observed within seconds. The control reactions for selectivity were performed in absence of DNA. Effect of pH. 675  108 per mL gold nanoparticles seed solution in 10 mM HEPES buffer of pH 6.0, 7.0, 7.4 and 8.0 were incubated with 0.6 M NH2-oln for 30 minutes. 50 M arginine were added and further incubated for 30 minute. 3 L 200 mM NH2OH was added to these solutions and stirred vigorously for 10 minutes. 5 L of 0.8% (w/v) HAuCl4 was added to these solutions to initiate the reduction reaction. The final volume in all reactions was maintained at 340L. The color change was observed within seconds. Characterizations. GNPs solution was characterized using UV-Vis Synergy micro plate reader (BIOTEK, USA). Absorbance measurement was taken over 300-800 nm wavelength range. The TEM images were taken using FEI, Technai G2 20 S-TWIN. The solid sample was dispersed in Millipore water and drop casted on Carbon coated 200 mesh TEM grid. Seed solution per mL was calculated as per method available in the literature.25 The PDI and -potential of the nanocomposites were measured using a Zetasizer Nano ZS90 (Malvern Instruments). DTS applications 7.03 software was used to analyze the data. All PDI reported here were based on intensity average. For each sample, three DLS measurements were conducted with a fixed 11 runs and each run lasts 10 s. Circular dichroism spectra of growth solutions from peptides were measured with a J-1500 CD spectropolarimeter at 25 °C. The spectra were collected from 195 nm to 255 nm by using a 10 mm path length quartz cuvette while keeping the HT voltage less than 500 V for reliability. The data were accumulated from three repeated runs and a smoothing process was done. Limit of Detection. The limit of detection was calculated by the formula; LOD = 3.3 x So’; where, So’= So /n, So’= the standard deviation used for calculating LOD, So = the estimated standard deviation of m single results near zero concentrations and n = the number of replicate observations averaged when reporting results where each replicate is obtained following the entire measurement procedure. Replicate measurements (10) of test samples were performed with lowest concentrations of analyte. ■ ASSOCIATED CONTENT Supporting Information: The Supporting Information is available free of charge on the ACS Publications website at DOI: Electronic absorption, TEM images, hydrodynamic radii, PDI, -potentials and circular dichroism graphs are mentioned in supporting information. ■ AUTHOR INFORMATION

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Corresponding Author *E-mail: [email protected] ORCID Kalyan K. Sadhu: 0000-0001-5891-951X Notes The authors declare no competing financial interest. ■ ACKNOWLEDGMENTS KKS acknowledges the DST Nanomission (DST/NM/NB/ 2018/237) for funding. ■ REFERENCES (1) Saha, K.; Agasti, S. S.; Kim, C., Li, X., and Rotello, V. M. (2012) Gold Nanoparticles in Chemical and Biological Sensing. Chem. Rev. 112, 2739. (2) Varongchayakul, N.; Xong, J.; Meller, A.; and Grinstaff, M. W. (2018) Single-molecule protein sensing in a nanopore: a tutorial. Chem. Soc. Rev. 47, 8512. (3) Zhou, W.; Gao, X.; Liu, D.; Chen, X. (2015) Gold Nanoparticles for In Vitro Diagnostics. Chem. Rev. 115, 10575. (4) (a) Edwardson, T. G. W., Lau, K. L., Bousmail, D., Serpell, C. J., and Sleiman, H. F. (2016) Transfer of molecular recognition information from DNA nanostructures to gold nanoparticles. Nat. Chem. 8, 162. (b) Zhang, Y., Chao, J., Liu, H., Wang, F., Su, S., Liu, B., Zhang, L., Shi, J., Wang, L., Huang, W., Wang, L., and Fan, C. (2016) Transfer of TwoDimensional Oligonucleotide Patterns onto Stereocontrolled Plasmonic Nanostructures through DNA-Origami-Based Nanoimprinting Lithography. Angew. Chem. Int. Ed. 55, 8036. (5) (a) Li, Q., Jiang, Y., Han, R., Zhong, X., Liu, S., Li, Z.-Y., Sha, Y., and Xu, D. (2013) High surface-enhanced Raman scattering performance of individual gold nanoflowers and their application in live cell imaging. Small 9, 927. (b) Wu, J., Liang, D., Jin, Q., Liu, J., Zhang, M., Duan, X., and Tang, X. (2015) Bioorthogonal SERS Nanoprobes for Mulitplex Spectroscopic Detection, Tumor Cell Targeting, and Tissue Imaging. Chem. Eur. J. 21, 12914. (c) Kariuki, V. M., Hoffmeier, J. C., Yazgan, I.; Sadik, O. A. (2017) Seedless synthesis and SERS characterization of multi-branched gold nanoflowers using water soluble polymers. Nanoscale 9, 8330. (6) Schreiber, R., Santigo, I., Ardavan, A., Turberfield, A. J. (2016) Ordering Gold Nanoparticles with DNA Origami Nanoflowers. ACS Nano 10, 7303. (7) (a) Tan, L. H., Yue, Y., Satyavolu, N. S. R., Ali, A. S., Wang, Z., Wu. Y., and Lu, Y. (2015) Mechanistic Insight into DNA-Guided Control of Nanoparticle Morphologies. J. Am. Chem. Soc. 137, 14456. (b) Wang, Z.; Zhang, J.; Ekman, J. M.; Kenis, P. J. A.; and Lu, Y. (2010) DNA-Mediated Control of Metal Nanoparticle Shape: One-Pot Synthesis and Cellular Uptake of Highly Stable and Functional Gold Nanoflowers. Nano Lett. 10, 1886. (8) Lee, H.-E., Yang, K. D., Yoon, S. M., Ahn, H.-Y., Lee, Y. Y., Chang, H., Jeong, D. H., Lee, Y.-S., Kim, M. Y., and Nam, K. T. (2015) Concave Rhombic Dodecahedral Au Nanocatalyst with Multiple High-Index Facets for CO2 reduction. ACS Nano 9, 8384. (9) Wang, K., Jiang, L., Zhang, F., Wei, Y., Wang, K., Wang, H., Qi, Z., and Liu, S. (2018) Strategy for In Situ Imaging of Cellular Alkaline Phosphatase Activity Using Gold Nanoflower Probe and Localized Surface Plasmon Resonance Technique. Anal. Chem. 90, 14056.


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Gold Nanoflower for Selective Detection of Single ... - ACS Publications

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