Inhibition of Amyloid Fibril Growth by Nanoparticle Coated with

Aug 27, 2014 - Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122050, India. •S Supporting ...
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Inhibition of Amyloid Fibril Growth by Nanoparticle Coated with Histidine-Based Polymer Sharbari Palmal,† Nihar R. Jana,*,‡ and Nikhil R. Jana*,† †

Centre for Advanced Materials, Indian Association for the Cultivation of Science, Kolkata, West Bengal 700032, India Cellular and Molecular Neuroscience Laboratory, National Brain Research Centre, Manesar, Gurgaon 122050, India

‡

S Supporting Information *

ABSTRACT: Amyloid protein fibrillation is responsible for variety of neurological disorders and thus inhibition of fibrillation is a potential therapeutic strategy for these diseases. Recent study shows that nanoparticles can significantly influence the kinetics of amyloid fibrillation, depending on their surface chemistry. Here we demonstrate that amyloid fibril formation can be completely inhibited by nanoparticles coated with histidine-based polymer. We have designed nanoparticles with modular surface chemistry and found that the presence of cationic and anionic surface charge, along with weakly hydrophobic functional groups, is essential in inhibiting the amyloid fibrillation processes. This work shows that the appropriate nanoprobe can be designed for controlling the amyloid fibrillation kinetics and for complete inhibition of fibrillation.

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INTRODUCTION

We work on the biomedical application of nanoparticles and toward this goal, we have synthesized a library of functional nanoparticles of 5−100 nm hydrodynamic diameters.41 They include different types of nanoparticles with varied surface charges and chemical functionalities. Here we have explored the interaction of amyloid peptide with the nanoparticles having various functional groups, with the possibility to develop a general functionalization strategy of nanoparticles for efficient amyloid inhibition. We found that the simple histidine based polymer coating on the nanoparticle surface can efficiently inhibit the amyloid fibrillation processes in a dose-dependent manner. Our study also shows that both cationic and anionic surface charges, as well as the hydrophobic functionality, are necessary for efficient amyloid inhibition.

Amyloid protein misfolding to form highly ordered fibrillar aggregates is believed to be the main characteristic feature of various neurodegenerative disorders like Alzheimer’s, Parkinson’s, and Huntington’s disease.1−8 It is now well understood that self-assembly of beta amyloid peptide/protein into a cross β-sheeted fibril causes the neuronal dysfunction.1−8 So, inhibiting the beta amyloid (Aβ) fibril growth has been considered as one therapeutic approach for these diseases. Thus, various approaches have been reported to inhibit amyloid fibrillation processes that include small molecules,9−16 functional polymers,17−19 and nanoparticles.20−29 Among them, nanoparticle-based inhibition is the most efficient, and it has been shown that nanoparticles can stimulate, inhibit, or delay the fibrillation kinetic, depending on their surface chemical functional groups. For example, a variety of bare nanoparticles,30,31 anionic nanoparticles,32,33 and specific proteins/ peptides (α-synuclein, Aβ1−40, and others) functionalized nanoparticles23,34,35 are reported to promote amyloid fibrillation. Cationic nanoparticles are also reported to induce amyloid fibrillation.22 In contrast, hydrophobic nanoparticles or nanoparticles functionalized with hydrophobic molecules such as KLVFF peptide,24 phenylalanine-phenylalanine dipeptide,27 and dihydrolipoic acid26 are reported to inhibit the fibrillation process. In addition, nanoparticles functionalized with specific affinity molecules, such as curcumin,36−38 dextran,39 and sialic acid,40 are reported to inhibit fibrillation processes. These results indicate that further studies are required for better understanding of the effects of modular surface chemistry on amyloid fibrillation. © XXXX American Chemical Society

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EXPERIMENTAL SECTION Reagents. Gold(III) chloride, didodecyldimethylammonium bromide (DDAB), tetrabutylammonium borohydride (TBAB), igepal CO-520, imidazole, L-histidine monohydrochloride monohydrate, 2,4,6-tris(bromomethyl) mesitylene, oleylamine, oleic acid, thioflavin T (ThT) were purchased from Sigma-Aldrich. Succinic anhydride and phthalic anhydride were purchased from Loba Chemie Pvt., Ltd. Amyloid β protein fragment 1−42 with >90% purity was purchased from Genpro Biotech. Amyloid β protein fragment 1−40 with >90% purity was purchased from Sigma. All the reagents were used without further purification. Received: June 6, 2014 Revised: August 25, 2014

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Scheme 1. Structure of Polymer Coated Au Nanoparticles with Different Functional Groups on Their Surfacea

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(I) Histidine based polymer coating; (II) polyacrylate coating with polyethylene glycol and amine groups; (III) polyacrylate coating with polyethylene glycol, amine, and carboxylate groups; (IV) polyacrylate coating with polyethylene glycol, amine, and phthalic groups; and (V) polyacrylate coating with polyethylene glycol, amine, and oleyl groups.

Synthesis of Hydrophobic Gold Nanoparticle. Hydrophobic gold nanoparticles in toluene were prepared according to a reported method.42 Briefly, 5 mL toluene solution of AuCl3 (0.01M) was prepared in the presence of DDAB (0.02M). Next, 100 μL oleyl amine and 100 μL oleic acid were added to this solution. Then, 500 μL toluene solution of TBAB (prepared by mixing 25 mg TBAB and 25 mg DDAB in 500 μL toluene) was added under stirring to produce gold nanoparticle. The synthesized nanoparticles were precipitated twice by adding ethanol into the nanoparticle solution, followed by centrifugation to remove excess reagent. Finally, the precipitated nanoparticles were dissolved in 5 mL cyclohexane and used as stock solution for polymer coating. Histidine Based Polymer Coating of Gold Nanoparticle. We used histidine based polymer coating on gold nanoparticle surface following a reported method with minor modification.43 Briefly, about 9.5 mL of cyclohexane-igepal reverse micelle solution was prepared by mixing 8 mL cyclohexane and 1.5 mL igepal CO-520. Next, 10 mg of 2,4,6-tris(bromomethyl) mesitylene was dissolved in the reverse micelle solution, and then 500 μL of gold nanoparticle solution was added to it. Thereafter, 125 μL of aqueous solution of L-histidine monohydrochloride (32 mg dissolved in 500 μL water) was mixed to the reverse micelle solution. Finally, 6 μL of N,N,N′,N′-tetramethyl ethylene diamine was added, and the optically clear solution was stirred overnight for in situ polymerization. The polymer coated nanoparticle was precipitated by ethanol addition, repeatedly washed with ethanol, and finally dissolved in 0.5 mL distilled water. Histidine-based polymer has been synthesized as a control polymer, using the same procedure, with the exception that Au nanoparticle has not been used during polymerization. Polyacrylate Coating of Gold Nanoparticle. Polyacrylate coated gold nanoparticle was prepared using our reported method.44 Briefly, 12 mL of igepal-cyclohexane reverse micelle solution was prepared and mixed with 100 μL aqueous solution

of N-(3-aminopropyl) methacrylamide hydrochloride (18 mg dissolved in 100 μL water), 100 μL aqueous solution of poly(ethylene glycol) methacrylate (36 μL dissolved in 100 μL water), and 100 μL aqueous solution of methylene-bisacrylamide (3 mg dissolved in 100 μL water by 10 min sonication). In this solution, 2 mL cyclohexane solution of gold nanoparticle and 100 μL of tetramethyl ethylene diamine were mixed. The solution was taken in a three naked flask, put under inert atmosphere by purging nitrogen for 20 min, and kept under magnetically stirring conditions. Finally, ammonium persulfate solution (3 mg dissolved in 100 μL water) was injected as a radical initiator to initiate the polymerization. The polymerization was continued at room temperature for 1 h, and then particles were precipitated by adding ethanol. The particles were washed with chloroform and ethanol and finally dissolved in 2 mL distilled water or ethanol. Conjugation with succinic and phthalic anhydride was performed by mixing 0.5 mL ethanolic dispersion of nanoparticle with 0.5 mL ethanolic solution of anhydride (prepared by dissolving 0.05 mM succinic or pthalic anhydride in 1 mL ethanol) followed by overnight stirring. Then particles were precipitated by adding 1:1 mixture of toluene/chloroform. The precipitate was finally dissolved in 0.5 mL distilled water. Conjugation with oleyl group was performed via glutaraldehyde based coupling chemistry. Glutaraldehyde was conjugated with oleylamine in 1:1 molar ratio by mixing ethanolic solution of gluteraldehyde (0.1M) and ethanolic solution of oleylamine (0.1M) and after 15 min of their mixing, 25 μL of this mixture was added to 0.5 mL of gold nanoparticle solution dissolved in borate buffer of pH-9. After 1 h, NaBH4 solution was added to this to reduce the imine bond formed by the reaction between the aldehyde and amine. Subsequently, this solution was dialyzed overnight against distilled water using a 12−14 kDa molecular weight cutoff (MWCO) membrane to remove unbound reagents. B

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Amyloid Formation Study. Aβ1−42 peptide was used for most of the studies and in some control experiments Aβ1−40 peptide was also used. A stock solution of Aβ peptide with one mM concentration was prepared by dissolving lyophilized Aβ peptide in anhydrous DMSO. Next, working solution of Aβ peptide with 25 μM concentration was prepared by diluting the stock solution in acidic water of pH 2 (adjusted by concentrated HCl solution) containing 140 mM NaCl and 2.5 mM KCl. The peptide stock solution was mixed with 4− 200 μL of nanoparticle solution (∼3 μM) keeping final volume of the solution fixed at 400 μL and then incubated at 37 °C for up to 14 days. In control experiments, the Aβ peptide solution was kept at 37 °C for up to 14 days without adding any nanoparticles. Fibrillation of Hen egg white lysozyme (HEWL) protein of 140 μM was studied in presence or absence of nanoparticle at 60 °C with the solution at pH 2 in the presence of 140 mM NaCl and 2.5 mM KCl. Fibril formation kinetics was monitored by a thioflavin T (ThT) based fluorescence assay. A stock solution of ThT with 10 μM concentration was prepared in PBS buffer of pH 7.4. Next, 30 μL peptide solution was collected at different time point and mixed with 200 μL of ThT solution. After 5 min, the ThT fluorescence was measured at 480 nm under 440 nm excitation. Instrumentation. Fluorescence spectra were measured in a BioTek Synergy MX microplate reader. Fourier transform infrared spectroscopy (FTIR) on a KBr pellet was performed using a PerkinElmer Spectrum 100 FTIR spectrometer. DLS and Zeta potential measurements were done using a NanoZS (Malvern) instrument. TEM study was performed using an FEI Tecnai G2 F20 microscope with a field-emission gun operating at 200 kV. CD spectra were performed using a JASCO J-815 CD Spectrometer (Model J-815−1508).

with phthalic anhydride. Similarly, type V nanoparticle is synthesized from type II nanoparticle via reaction of some of their primary amines with oleyl amine through gluteraldehyde based coupling chemistry.44 Properties of five types of nanoparticles are summarized in Figures 1 and 2 and Supporting Information (SI) Figures S1

Figure 1. Representative TEM images of type I (a) and type II nanoparticles (b), UV−visible absorption spectra of Au nanoparticle of type I−V (c), and their corresponding digital images (d). Scale bars in (a) and (b) represent 100 nm.

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and S2. The presence of different surface functional groups has been characterized by FTIR study (SI Figures S1 and S2). Colloidal solutions of each type particle are pink in color due to the presence of Au nanoparticle with a surface plasmon peak at around 530 nm (Figure 1). The hydrodynamic sizes of particles varies between 18 and 40 nm that include 3−5 nm Au core and polymeric organic shell (Figures 1 and 2). However, the surface charge of nanoparticle varies depending on the nature of functional groups and solution pH. For example, type I, II, and V nanoparticles possess high positive charge in acidic and neutral pH but approached neutral charge at basic pH. These results can be explained by protonation of amine groups at acidic pH that become deprotonated with increasing pH. In contrast, type III and IV nanoparticles possess positive charge in acidic and neutral pH, but becomes negatively charged at basic pH. This is due to the additional contribution of carboxylate groups that deprotonate with increasing pH. Influence of Amyloid Fibrillation Kinetics by Nanoparticle Surface Chemistry. In order to study the effect of nanoparticles on the fibrillation process, the Aβ1−42 monomer is co-incubated with nanoparticles under the fibril forming condition, and fibrillation is monitored via optical and microscopic methods (Figures 3−7 and SI Figures S3 and S4). The typical concentration of the peptide has been kept at 25 μM and the nanoparticle concentration has been varied from 0 to 1.5 μM. Thioflavin T (ThT) based fluorescence assay has been used for optical-based monitoring of amyloid aggregation kinetics. ThT is an amyloid-specific dye whose fluorescence intensity enhances upon binding with the fibril.45,46 Results of ThT based assay are summarized in Figures 3 and 4. It shows

RESULTS Synthesis of Nanoparticle with Different Surface Functional Group. The type of nanoparticle used in this work is shown in Scheme 1, highlighting the structure of the surface functional groups. Type I nanoparticle has histidine based functional groups, type II nanoparticle has polyethylene glycol along with primary amine groups, type III nanoparticle has polyethylene glycol along with amine and carboxylate groups, type IV nanoparticle has polyethylene glycol along with amine and phthalic acid groups, and type V nanoparticle has polyethylene glycol along with amine and oleyl groups. The synthetic steps involve preparation of hydrophobic Au nanoparticles, followed by polymer coating and conjugation chemistry. Hydrophobic gold nanoparticles of 3−5 nm size are synthesized according to an earlier report.42 This hydrophobic Au nanoparticle is then converted into different types of nanoparticles via reverse micelle based polymer coating using our reported methods.41,43,44 (See experimental section and Supporting Information (SI), Scheme S1 for details.) Type I nanoparticle is synthesized by histidine based polymer coating. Type II nanoparticle has been synthesized by polyacrylate coating with monomer mixtures of poly(ethylene glycol) methacrylate and N-(3-aminopropyl) methacrylamide, where the first monomer provides polyethylene glycol functionality and the second monomer provides amine functionality. Type III nanoparticle is synthesized from type II nanoparticle via reaction of some of their primary amines with succinic anhydride. Type IV nanoparticle is synthesized from type II nanoparticle via reaction of a fraction of their primary amines C

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Figure 2. pH dependent surface charge and hydrodynamic size of five different types of nanoparticles used in this work.

Figure 3. Fibrillation kinetics of Aβ1−42 peptide in the presence of type I nanoparticle of micromolar concentrations (a) and in the presence of micromolar concentration of histidine (b), showing that fibrillation is inhibited by type I nanoparticle but almost undisturbed by histidine. The fibrillation kinetics is monitored by conventional thioflavin T based fluorescence assay. Values in the bracket in (a) correspond to the respective concentration of histidine.

that type I nanoparticle with histidine based polymer coating has significantly inhibited the fibrillation process, as observed from low fluorescence signal, and this inhibition effect is more prominent with the increasing particle concentration (Figure 3a). Other nanoparticles are relatively less efficient in inhibiting the fibrillation processes as observed from higher fluorescence intensity of ThT (Figure 4). The control experiment shows that the histidine monomer of similar or higher concentration is almost inefficient in inhibiting the fibrillation processes (Figure 3b and SI Figures S5 and S6). Fibril formation has been extensively investigated under TEM and agrees well with the results of ThT based assay (Figures 5−8 and SI Figures S3, S7, and S8). While long fibrils

are clearly observed in the absence of any nanoparticle, the fibril length becomes shorter in the presence of 0.15 μM of type I nanoparticle, and fibrils are almost invisible in the presence of 0.8 μM of type I nanoparticle (Figure 5). Length distribution histograms of fibrils have been prepared by measuring the fibril length from TEM images (Figure 8). The results clearly indicate the formation of 0.1−1.5 μm (average length 0.45 μm) long fibrils in the absence of nanoparticles, whereas the length is shortened to 0.05−0.7 μm (average length 0.25 μm) in the presence of 0.15 μM of type I nanoparticles, shortened to 0.05−0.55 μm (average length 0.19 μm) in the presence of 0.30 μM of type I nanoparticles, and becomes 0.05−0.35 μm (average length 0.1 μm) in the presence of 0.8 μM of type I D

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Figure 4. Fibrillation kinetics of Aβ1−42 peptide at 0.3 μM concentration (a) and 0.8 μM concentrations (b) in the presence of type II, III, IV, and V nanoparticles, showing that fibrillation is partially inhibited. The fibrillation kinetics is monitored by conventional thioflavin T based fluorescence assay.

Figure 7. TEM images of Aβ1−42 fibrils formed in the presence of 0.8 μM polyacrylate coated type II, III, IV, and V nanoparticles. Scale bars represent 0.5 μm.

Figure 5. Representative transmission electron microscopic images of Aβ1−42 fibrils formed in the absence of any nanoparticles and in the presence of type I nanoparticles with histidine based polymer coatings of different concentrations. The result shows that fibril formation is inhibited with the increasing concentration of nanoparticles. Scale bars represent 0.5 μm.

fibrillation process in a dose-dependent manner. The control fibrillation experiment in the presence of histidine monomer shows fibrillar morphology, suggesting that histidine is unable to inhibit fibrillation (Figure 6a). An additional control fibrillation experiment has been performed in the presence of histidine-based polymer and found that they have an insignificant effect in amyloid fibril inhibition (Figure 6b). In order to understand the role of the type I nanoparticle that severely inhibits the amyloid fibrillation processes, the conformational change of Aβ1−42 secondary structure has been investigated before and after fibrillation steps via circular dichroism (CD) spectroscopy (Figure 9). The results show that the negative band corresponding to the β-sheet structure of the peptide at 216 nm emerges after fibrillation, but becomes weaker or absent if type I nanoparticles are present during the fibrillation stage. In addition, a new negative band at 222 nm appears, which is attributed to an α-helix structure. These results suggest that type I nanoparticles efficiently interact with Aβ1−42 peptide and inhibits its conformational transition from α-helix to β-sheet structure during the fibrillation stage.

Figure 6. (a) Representative transmission electron microscopic images of Aβ1−42 fibrils formed in the presence of 10 mM histidine monomer (a) and fibrillation kinetics of Aβ1−42 peptide in the presence of various concentrations of histidine-based polymer (b). Scale bars represent 0.5 μm.

nanoparticles. These results confirm that histidine based polymer coatings inhibit the elongation of the Aβ 1−42 E

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Figure 8. Length distribution of Aβ1−42 fibrils formed in the presence of type I nanoparticles at various concentrations (a) and in the presence of 0.8 μM polycrylate coated type II, III, IV, and V nanoparticles (b).

nanoparticles coated with histidine-based polymer can strongly influence fibrillation steps in a dose-dependent manner and completely inhibit the fibril formation at high concentrations. A TEM study at lower nanoparticle concentrations clearly shows that nanoparticles are attached to the growing fibrils, and, in most cases, they are attached at the long end of the growing fibrils (Figure 5 and SI Figure S3). This indicates that attachment of nanoparticles at the growing end blocks the fibril elongation, and at the high particle concentration, the inhibition is so strong that the fibril growth is completely stopped. We have tested the amyloid fibrillation in the presence of different concentrations of histidine, and the results clearly show that monomeric histidine of similar or higher concentration is almost inefficient. For example, we have tested the fibrillation experiment in the presence of 10 mM histidine, which is 15 times higher than the histidine present in 0.8 μM of type I nanoparticle, but the fibrils found are of similar length as those under standard conditions. Similarly, histidine-based polymer is also inefficient in inhibiting amyloid fibrillation. These results clearly indicate that histidine becomes effective amyloid inhibition agent when they are in nanoparticle form. This may be due to the fact that in nanoparticle form histidine offers multivalent interaction with the growing fibril, which is insignificant in monomeric or polymeric histidine. Similar type multivalent interaction has been reported for the peptide functionalized protein microsphere24 and trehalose functionalized polymer18 toward the inhibition of amyloid fibrillation. A tentative mechanism has been proposed for the nanoparticle induced amyloid fibril inhibition processes (Scheme 2). Role of Nanoparticle Surface Chemistry in Inhibiting Amyloid Fibrillation. As a histidine-based coating is most efficient in the amyloid inhibition process, further investigation has been carried out to understand the exact role of this coating. Histidine based polymer coating introduces cationic charge due to its amine and imidazole ring, anionic charge due to its carboxylate, and weak hydrophobicity due to its imidazole ring and methylene groups. We have independently synthesized nanoparticles with each type of component and then tested their role on fibrillation processes. For example, we have separately synthesized nanoparticles having different surface functionality, such as primary and secondary amine, carboxylate, phthalate, polyethylene glycol, and oleyl groups. Among them, primary and secondary amine provides a cationic surface

Figure 9. Circular dichroism spectra of solution of Aβ1−42 peptide (12 μM) before and after exposing under fibrillation conditions, showing the influence of type I nanoparticles on the Aβ1−42 secondary structure: (i) before fibrillation, (ii) after fibrillation by 14-day exposure under fibrillation conditions, (iii) after 14-day exposure under fibrillation conditions in the presence of 0.3 μM of type I nanoparticle, and (iv) after 14-day exposure under fibrillation conditions in the presence of 0.8 μM of type I nanoparticle.

We have also performed the immunoblot analysis to investigate the nature of oligomer formed with respect to monomer and fibril. (SI Figure S9) The concentration of Aβ peptide is kept the same in terms of monomer (100 ng) for all the experiments. A clear peptide dimer band and smeared oligomer bands are observed when amyloid fibrils are prepared in the presence of nanoparticles. Although the peptide dimer intensity is the same for all types of nanoparticles, the intensity of the smeared oligomer band is higher for polyacrylate coated nanoparticles (i.e., type II to V) and almost absent for type I nanoparticles. This result corrolates with smaller fibril formation with polyacrylate-coated particles, as compared to the insignificant fibril formation for type I nanoparticles.

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DISCUSSION Inhibition of Amyloid Fibrillation by Nanoparticle Coated with Histidine Based Polymer. Fibrillation of Aβ occurs via nucleation−growth steps, i.e., initial formation of small nuclei through oligomerization of peptide and then elongation of the fibril via protofibril formation.20−36 Nanoparticles can greatly influence this nucleation−growth process by interacting at the intermediate stage of the fibril growth, and the nature of interaction is highly dependent on the nanoparticle surface functionality. Our finding shows that F

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functional groups are essential for efficient inhibition of amyloid fibril growth.

Scheme 2. Proposed Mechanism of Amyloid Fibril Inhibition by Type I Nanoparticle

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CONCLUSIONS The interaction of amyloid peptide with various functional nanoparticles has been explored for the development of nanoparticle based inhibition strategy of amyloid fibrillation. We found that simple histidine based polymer coated nanoparticles can efficiently inhibit the amyloid fibrillation processes. Control experiments with various functional nanoparticles show that both cationic and anionic surface charge along with weakly hydrophobic functional groups are necessary for efficient amyloid inhibition. This work provides a general guideline for the development of nanoparticle-based probes for amyloid targeting, detection, and inhibition.

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charge, carboxylate provides an anionic surface charge, phthalate provides weak hydrophobicity along with an anionic surface charge, and the oleyl group provides strong hydrophobicity. Using these functional groups, we have synthesized nanoparticles having modular surface charges and lipophillicity that partially or significantly mimic the property of histidine based polymer coatings. For example, the surface charges of type II and V nanoparticles are highly positive at acidic and neutral pH, but approach zero at basic pHa property which mimics type I nanoparticles; type III and IV nanoparticles mimic type I nanoparticles in possessing both positively and negatively charged functional groups and modular overall surface charge varying from positive to negative with increasing solution pH; type IV and type I nanoparticles both possess weakly hydrophobic functional groups. The disadvantage of strongly hydrophobic functional groups (e.g., oleyl) is that the excessive number of it decreases the water solubility of nanoparticles unless other hydrophilic functional groups (e.g., amine and polyethylene glycol) are present to counter it. The role of the polyethylene glycol functional group has been tested after functionalizing type 1 nanoparticles with polyethylene glycol. It is observed that polyethylene glycol functionalization lowers the fibril inhibition property of type I nanoparticles (SI Figure S8). This result implies that the presence of polyethylene glycol in type II, III, IV, and V nanoparticle surfaces slightly lowers their fibril inhibition property. As the hydrodynamic sizes of all the particles are in the range of 18−40 nm, it can be expected that particle size does not influence the amyloid fibrillation in the present case. Our results clearly show that amyloid inhibition efficiency increases in the order I > III, IV, V > II. This result indicates that cationic and anionic functional groups, as well as lipophillicity, are required for effective inhibition of nanoparticle. Our results partially corroborate the earlier reported works. It is reported that if nanoparticles have only anionic or cationic charge, then they are not efficient amyloid inhibitors, but if both charge and hydrophobicity are introduced in a nanoparticle, then it become more efficient. For example, negatively charged nanoparticles are reported to accelerate32 or inhibit29 fibrillation. Similarly, positively charged nanoparticles are reported to accelerate the amyloid fibrillation process at lower concentration, but inhibit the fibrillation process at higher concentration.22,39 In contrast, dihydrolipoic acid capped hydrophobic-anionic nanoparticles26 and hydrophobic polymeric nanoparticles20 can inhibit the fibrillation processes.26 Other amyloid inhibiting nanoparticles are also having charged surface and lipophilic character.23,24,34,35 Thus, anionic and cationic surface charge as well as weakly hydrophobic surface

ASSOCIATED CONTENT

S Supporting Information *

Details of coating schemes, FTIR characterization of functionalized nanoparticle, determination of number of histidine per nanoparticle, fibrillation study using Aβ1−40, HEWL protein, and an additional TEM image of amyloid fibrils and Western blot analysis data. This material is available free of charge via Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors would like to thank DST and DBT, government of India for financial assistance. S.P. acknowledges CSIR, India for providing research fellowship. We acknowledge Sreetama Basu of NBRC for performing Western blot analysis.

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REFERENCES

(1) Selkoe, D. J. Translating Cell Biology into Therapeutic Advances in Alzheimer’s Disease. Nature 1999, 399, A23−A31. (2) Selkoe, D. J. Folding Proteins in Fatal Ways. Nature 2003, 426, 900−904. (3) Jana, N. R.; Nukina, N. Recent Advances in Understanding the Pathogenesis of Polyglutamine Diseases: Involvement of Molecular Chaperones and Ubiquitin-Proteasome Pathway. J. Chem. Neuroanat. 2003, 26, 95−101. (4) Fink, A. L. The Aggregation and Fibrillation of α-Synuclein. Acc. Chem. Res. 2006, 39, 628−634. (5) Ban, T.; Yamaguchi, K.; Goto, Y. Direct Observation of Amyloid Fibril Growth, Propagation, and Adaptation. Acc. Chem. Res. 2006, 39, 663−670. (6) Eisenberg, D.; Nelson, R.; Sawaya, M. R.; Balbirnie, M.; Sambashivan, S.; Ivanova, M. I.; Madsen, A. Ø.; Rieke, C. The Structural Biology of Protein Aggregation Diseases: Fundamental Questions and Some Answers. Acc. Chem. Res. 2006, 39, 568−575. (7) Jellinger, K. A. Alzheimer 100Highlights in the History of Alzheimer Research. J. Neural Transm. 2006, 113, 1603−1623. (8) Rambaran, R. N.; Serpell, L. C. Amyloid Fibrils: Abnormal Protein Assembly. Prion 2008, 2, 112−117. (9) Ono, K.; Hasegawa, K.; Naiki, H.; Yamada, M. Curcumin has Potent Anti-amyloidogenic Effects for Alzheimer’s β-Amyloid Fibrils in Vitro. J. Neurosci. Res. 2004, 75, 742−750. G

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The Journal of Physical Chemistry C

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(10) Yang, F.; Lim, G. P.; Begum, A. N.; Ubeda, O. J.; Simmons, M. R.; Ambegaokar, S. S.; Chen, P.; Kayed, R.; Glabe, C. G.; Frautschy, S. A.; Cole, G. M. Curcumin Inhibits Formation of Amyloid β Oligomers and Fibrils, Binds Plaques, and Reduces Amyloid in Vivo. J. Biol. Chem. 2005, 280, 5892−5901. (11) Garcia-Alloza, M.; Borrelli, L. A.; Rozkalne, A.; Hyman, B. T.; Bacskai, B. J. Curcumin Labels Amyloid Pathology in Vivo, Disrupts Existing Plaques, and Partially Restores Distorted Neurites in an Alzheimer Mouse Model. J. Neurochem. 2007, 102, 1095−1104. (12) Stains, C. I.; Mondal, K.; Ghosh, I. Molecules that Target βAmyloid. ChemMedChem. 2007, 2, 1674−1692. (13) Austen, B. M.; Paleologou, K. E.; Ali, S. A. E.; Qureshi, M. M.; Allsop, D.; El-Agnaf, O. M. A. Designing Peptide Inhibitors for Oligomerization and Toxicity of Alzheimer’s β-Amyloid Peptide. Biochemistry 2008, 47, 1984−1992. (14) Frydman-Marom, A.; Rechter, M.; Shefler, I.; Bram, Y.; Shalev, D. E.; Gazit, E. Cognitive-Performance Recovery of Alzheimer’s Disease Model Mice by Modulation of Early Soluble Amyloidal Assemblies. Angew. Chem., Int. Ed. 2009, 48, 1981−1986. (15) Vilasi, S.; Iannuzzi, C.; Portaccio, M.; Irace, G.; Sirangelo, I. Effect of Trehalose on W7FW14F Apomyoglobin and Insulin Fibrillization: New Insight into Inhibition Activity. Biochemistry 2008, 47, 1789−1796. (16) Yu, W.-B.; Jiang, T.; Lan, D.-M.; Lu, J.-H.; Yue, Z.-Y.; Wang, J.; Zhou, P. Trehalose Inhibits Fibrillation of A53T Mutant α-Synuclein and Disaggregates Existing Fibrils. Arch. Biochem. Biophys. 2012, 523, 144−150. (17) Shi, W.; Dolai, S.; Rizk, S.; Hussain, A.; Tariq, H.; Averick, S.; L’Amoreaux, W.; Idrissi, A. E.; Banerjee, P.; Raja, K. Synthesis of Monofunctional Curcumin Derivatives, Clicked Curcumin Dimer, and a PAMAM Dendrimer Curcumin Conjugate for Therapeutic Applications. Org. Lett. 2007, 9, 5461−5464. (18) Miura, Y.; You, C.; Ohnishi, R. Inhibition of Alzheimer Amyloid-β Aggregation by Polyvalent Trehalose. Sci. Technol. Adv. Mater. 2008, 9, 024407−024413. (19) Wada, M.; Miyazawa, Y.; Miura, Y. A Specific Inhibitory Effect of Multivalent Trehalose toward Aβ (1−40) Aggregation. Polym. Chem. 2011, 2, 1822−1830. (20) Cabaleiro-Lago, C.; Quinlan-Pluck, F.; Lynch, I.; Lindman, S.; Minogue, A. M.; Thulin, E.; Walsh, D. M.; Dawson, K. A.; Linse, S. Inhibition of Amyloid β Protein Fibrillation by Polymeric Nanoparticles. J. Am. Chem. Soc. 2008, 130, 15437−15443. (21) Xiao, L.; Zhao, D.; Chan, W.-H.; Choi, M. M. F.; Li, H.-W. Inhibition of Beta (1−40) Amyloid Fibrillation with N-acetyl-Lcysteine Capped Quantum Dots. Biomaterials 2010, 31, 91−98. (22) Cabaleiro-Lago, C.; Quinlan-Pluck, F.; Lynch, I.; Dawson, K. A.; Linse, S. Dual Effect of Amino Modified Polystyrene Nanoparticles on Amyloid-β Protein Fibrillation. ACS Chem. Neurosci. 2010, 1, 279− 287. (23) Skaat, H.; Shafir, G.; Margel, S. Acceleration and Inhibition of Amyloid-β Fibril Formation by Peptide-Conjugated FluorescentMaghemite Nanoparticles. J. Nanopart. Res. 2011, 13, 3521−3534. (24) Richman, M.; Wilk, S.; Skirtenko, N.; Perelman, A.; Rahimipour, S. Surface-Modified Protein Microspheres Capture Amyloid-β and Inhibit its Aggregation and Toxicity. Chem.Eur. J. 2011, 17, 11171− 11177. (25) Yoo, S. I.; Yang, M.; Brender, J. R.; Subramanian, V.; Sun, K.; Joo, N. E.; Jeong, S.-H.; Ramamoorthy, A.; Kotov, N. A. Inhibition of Amyloid Peptide Fibrillation by Inorganic Nanoparticles: Functional Similarities with Proteins. Angew. Chem., Int. Ed. 2011, 50, 5110−5115. (26) Thakur, G.; Micic, M.; Yang, Y.; Li, W.; Movia, D.; Giordani, S.; Zhang, H.; Leblanc, R. M. Conjugated Quantum Dots Inhibit the Amyloid β (1−42) Fibrillation Process. Int. J. Alzheimers Dis. 2011, 2011, No. 502386. (27) Skaat, H.; Chen, R.; Grinberg, I.; Margel, S. Engineered Polymer Nanoparticles Containing Hydrophobic Dipeptide for Inhibition of Amyloid-β Fibrillation. Biomacromolecules 2012, 13, 2662−2670.

(28) Mahmoudi, M.; Akhavan, O.; Ghavami, M.; Rezaee, F.; Ghiasi, S. M. A. Graphene Oxide Strongly Inhibits Amyloid Beta Fibrillation. Nanoscale 2012, 4, 7322−7325. (29) Liao, Y.-H.; Chang, Y.-J.; Yoshiike, Y.; Chang, Y.-C.; Chen, Y.-R. Negatively Charged Gold Nanoparticles Inhibit Alzheimer’s Amyloid-β Fibrillization, Induce Fibril Dissociation, and Mitigate Neurotoxicity. Small 2012, 8, 3631−3639. (30) Linse, S.; Cabaleiro-Lago, C.; Xue, W.-F.; Lynch, I.; Lindman, S.; Thulin, E.; Radford, S. E.; Dawson, K. A. Nucleation of Protein Fibrillation by Nanoparticles. Proc. Natl. Acad. Sci. U.S.A. 2007, 104, 8691−8696. (31) Wu, W.-H.; Sun, X.; Yu, Y.-P.; Hu, J.; Zhao, L.; Liu, Q.; Zhao, Y.-F.; Li, Y.-M. TiO2 Nanoparticles Promote β-Amyloid Fibrillation in Vitro. Biochem. Biophys. Res. Commun. 2008, 373, 315−318. (32) Zhang, D.; Neumann, O.; Wang, H.; Yuwono, V. M.; Barhoumi, A.; Perham, M.; Hartgerink, J. D.; Wittung-Stafshede, P.; Halas, N. J. Gold Nanoparticles Can Induce the Formation of Protein-Based Aggregates at Physiological pH. Nano Lett. 2009, 9, 666−671. (33) Wagner, S. C.; Roskamp, M.; Pallerla, M.; Araghi, R. R.; Schlecht, S.; Koksch, B. Nanoparticle-Induced Folding and Fibril Formation of Coiled-Coil-Based Model Peptides. Small 2010, 6, 1321−1328. (34) Roberti, M. J.; Morgan, M.; Menéndez, G.; Pietrasanta, L. I.; Jovin, T. M.; Jares-Erijman, E. A. Quantum Dots as Ultrasensitive Nanoactuators and Sensors of Amyloid Aggregation in Live Cells. J. Am. Chem. Soc. 2009, 131, 8102−8107. (35) Vannoy, C. H.; Leblanc, R. M. Effects of DHLA-Capped CdSe/ ZnS Quantum Dots on the Fibrillation of Human Serum Albumin. J. Phys. Chem. B 2010, 114, 10881−10888. (36) Taylor, M.; Moore, S.; Mourtas, S.; Niarakis, A.; Re, F.; Zona, C.; Ferla, B. L.; Nicotra, F.; Masserini, M.; Antimisiaris, S. G.; et al. Effect of Curcumin-Associated and Lipid Ligand-Functionalized Nanoliposomes on Aggregation of the Alzheimer’s Aβ Peptide. Nanomed.: Nanotechnol., Biol., Med. 2011, 7, 541−550. (37) Mathew, A.; Fukuda, T.; Nagaoka, Y.; Hasumura, T.; Morimoto, H.; Yoshida, Y.; Maekawa, T.; Venugopal, K.; Kumar, D. S. Curcumin Loaded-PLGA Nanoparticles Conjugated with Tet-1 Peptide for Potential Use in Alzheimer’s Disease. PLoS One 2012, 7, e32616. (38) Palmal, S.; Maity, A. R.; Singh, B. K.; Basu, S.; Jana, N. R.; Jana, N. R. Inhibition of Amyloid Fibril Growth and Dissolution of Amyloid Fibrils by Curcumin−Gold Nanoparticles. Chem.Eur. J. 2014, 20, 6184−6191. (39) Mahmoudi, M.; Quinlan-Pluck, F.; Monopoli, M. P.; Sheibani, S.; Vali, H.; Dawson, K. A.; Lynch, I. Influence of the Physiochemical Properties of Superparamagnetic Iron Oxide Nanoparticles on Amyloid-β Protein Fibrillation in Solution. ACS Chem. Neurosci. 2013, 4, 475−485. (40) Kouyoumdjian, H.; Zhu, D. C.; El-Dakdouki, M. H.; Lorenz, K.; Chen, J.; Li, W.; Huang, X. Glyconanoparticle Aided Detection of βAmyloid by Magnetic Resonance Imaging and Attenuation of βAmyloid Induced Cytotoxicity. ACS Chem. Neur. Sci. 2013, 4, 575− 584. (41) Jana, N. R. Design and Development of Quantum Dots and Other Nanoparticles based Cellular Imaging Probe. Phys. Chem. Chem. Phys. 2011, 13, 385−396. (42) Jana, N. R.; Peng, X. Single-Phase and Gram-Scale Routes toward Nearly Monodisperse Au and Other Noble Metal Nanocrystals. J. Am. Chem. Soc. 2003, 125, 14280−14281. (43) Jana, N. R.; Patra, P. K.; Saha, A.; Basiruddin, S.; Pradhan, N. Imidazole Based Biocompatible Polymer Coating in Deriving