Mussel-Inspired Polydopamine Coating on Tobacco Mosaic Virus

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Mussel-inspired polydopamine coating on tobacco mosaic virus: one-dimensional hybrid nanofiber for gold nanoparticles growth Quan Zhou, Xiangxiang Liu, Ye Tian, Man Wu, and Zhongwei Niu Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.7b02252 • Publication Date (Web): 29 Aug 2017 Downloaded from http://pubs.acs.org on August 31, 2017

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Mussel-inspired polydopamine coating on tobacco mosaic virus: one-dimensional hybrid nanofiber for gold nanoparticles growth Quan Zhou,ab Xiangxiang Liu,a Ye Tian,*a Man Wua and Zhongwei Niu*ac a

Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.

b

Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China.

c

School of Future Technology, University of Chinese Academy of Sciences, Beijing 100049, China. * E-mail: [email protected] (Z.N); [email protected] (Y.T).

ABSTRACT: One-dimensional (1D) hybrid nanofibers with surface deposited gold nanoparticles (AuNPs) have been fabricated by self-assembly of rod-like tobacco mosaic virus (TMV) with mussel-inspired polymerization of dopamine and in-situ reduction of gold ion, providing a method for sensing the endocytic pathway of nanomaterial.

KEYWORDS:

tobacco

mosaic

virus,

polydopamine,

self-assembly,

nanofiber,

gold

nanoparticles. 1. INTRODUCTION The nano-structured functional materials have received extensive attention and thorough research,1 especially one-dimensional (1D) inorganic-organic hybrid materials such as nanowire,

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nanotube and nanofiber, due to the unique properties and multiple applications in electronic, catalytic and sensing fields.2 One of the most favorable methods is “Bottom up” by controlled assembly of bio-template into 1D nano-structure and then surface deposition of inorganic nanoparticles on the template.3 The nano-sized bio-templates including DNA,4 polymer,5 peptide6 and virus7-8 have been exploited for gold nanoparticles (AuNPs) growing on the outer surface using the biomineralization approaches. Here, we present AuNPs hybrid nanofibers as 1D nanomaterial to enhance the observation of endocytosis, which is constituted by tobacco mosaic virus (TMV) assembled nanofibers with polydopamine coating and gold nanoparticles (AuNPs) deposited on the nanofiber surface. TMV is a classic rod-like bionanoparticle with 300 nm length, 18 nm outer diameter, exhibiting high aspect ratio and narrow dispersity characteristics,9 which has contributed to fabricating 1D nanofiber materials for many applications.10 Recent studies show that the conductive composite long fibers were prepared with head-to-tail assembly of TMV as template, assisted by in-situ polymerization of aniline11-12 or pyrrole with poly(sulfonated styrene) (PSS).13 Based on these works, as illustrated in Scheme 1, we have fabricated TMV head-to-tail assembled nanofibers assisted by bio-inspired polymerization of dopamine. Unlike polyaniline or polypyrrole which have great potential in nanoelectronics, polydopamine exhibits good biocompatibility and can be further surface modified with bioactive molecules or inorganic nanoparticles, which may have promising applications in biomedical field.14 After polydopamine coating, chloroauric acid was reduced into AuNPs on the nanofiber surface without any extra reductants. And then the AuNPs hybrid nanofibers were incubated with HeLa cells for further endocytic observation.


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Scheme 1. Preparation of AuNPs hybrid nanofibers as 1D nanomaterial for endocytic observation. 2. RESULTS AND DISCUSSION 2.1 Preparation of Polydopamine/TMV nanofibers. Polydopamine is made by autoxidation and polymerization of dopamine (3,4-dihydroxyphenethylamine), consisting of aggregated covalent oxidative oligomers and self-assembled physical trimer building blocks via noncovalent interaction including hydrogen bond, π-π stacking and hydrophobic interactions, which has extraordinary adhesion property bio-inspired by mussels.15-17 According to literatures, polydopamine can deposit on the surface of inorganic materials, organic polymers, and even on protein surface.14, 17-18 We have added ammonium persulfate as oxidant for the polymerization of dopamine.19 Moreover, TMV particularly favor head-to-tail assembly in acidic condition by minimizing the repulsion at each polar end of protein self-assembled sites.20-21 Therefore, oxidative polymerized dopamine oligomers are aggregated into a thin layer of polydopamine coating on TMV exterior surface, fixing the head-to-tail assembly structure of TMV based


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nanofiber in acidic condition. Besides, π−π stacking between the catechols of polydopamine and the phenolic hydroxyl groups of Tyr-139 at TMV exterior surface may play a key role in the formation of polydopamine adlayer. As shown in Figure 1, polydopamine/TMV nanofibers were confirmed by transmission electron microscopy (TEM). Most nanofibers were 1,230 ± 750 nm in average length (Figure 2a), far longer than 300 nm of the native TMV length. Compared with 18 nm of the original TMV diameter, the average diameter of nanofibers was 23.3 ± 3.1 nm (Figure 2b), indicating the formation of polydopamine thin layer on TMV protein surfaces. The length data of nanofibers were measured from more than 120 TEM images with sampling over 600 data points and the diameter data of nanofibers were measured from more than 55 TEM images with sampling over 400 data points, which were analyzed by ImageJ software v1.50.22 Some TEM images for the length and diameter distribution analysis are shown in Figure S1 & S2 (see Supporting Information).


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Figure 1. TEM images of (a) TMV; (b) polydopamine/TMV nanofibers; (c) a single nanofiber at length of 2,142 nm; (d) a single nanofiber at diameter of 23.5 nm.

Figure 2. Statistical analysis for the length distribution (a) and diameter distribution (b) of nanofibers. In addition, the dynamic light scattering (DLS) data closely corresponds with the length distribution of nanofibers, despite that the hydrodynamic radius does not directly reflect the length of nanofibers (Figure 3). The hydrodynamic radius at 89.4 nm belongs to the free TMV, and the emergence of hydrodynamic radius at 721.8 nm confirms the head-to-tail assembly of TMV during the polydopamine coating process. The polydopamine layer was also identified by UV-vis spectrum at 314 & 480 nm (Figure S3), and zeta potential measurement (Figure S4) shows that the zeta potential of polydopamine coating nanofibers are not affected by the pH value, not like the uncoated TMV (see Supporting Information).


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Figure 3. DLS data of TMV and polydopamine/TMV nanofibers. 2.2 Tuning the co-assembly morphology of polydopamine and TMV. Without TMV as the bio-template, polydopamine colloidal nanospheres (CNS) could be obtained because of dopamine over self-aggregation.23 The very attractive feature of the nanofiber reaction is that the polymerization of dopamine mostly generated on TMV surface in acidic condition (pH 5.5) with proper dopamine concentration (≤ 0.5 mg·mL-1). After dialysis and freeze dehydration process, the morphology of polydopamine/TMV nanofibers was aggregated into long filamentary network structures at micron scale, characterized by scanning electron microscope (SEM) (Figure 4 and Figure S5, see Supporting Information). Little bulk polydopamine CNS was observed. The transparent colour of the supernatant was turned to light brown after polymerization, demonstrating that only a little bulk polydopamine CNS was formed.


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Figure 4. SEM image of polydopamine/ TMV nanofibers after dialysis and freeze dehydration. The concentration of dopamine and the pH value of buffer are especially important to the nanofiber reaction, which can influence the assembly pattern and surface morphology of nanofibers. At pH value from 3.5 to 4.5, polydopamine/TMV assembly preferred to aggregate into bundle-like structure (Figure 5a). At pH value above 8.0, TMV capsid tended to disassemble, more amorphous protein and broken short-rod structure of TMV with polydopamine CNS could be observed (Figure 5b). At pH 5.5, when the concentration of dopamine was higher than 0.5 mg mL-1, the polydopamine CNS was formed and they preferred to deposit on TMV ends, thus a cross-linked network structure of nanofibers was obtained (Figure 5c). Moreover, the co-assembly structure of TMV embedded in polydopamine CNS was observed when the concentration of dopamine was surpassed 2.0 mg mL-1 at pH 7.4 (Figure 5d).


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Figure 5. TEM images of the polydopamine/TMV nanofiber prepared at different pH value and dopamine concentration. (a) at pH 4.2, bundle like structure; (b) at pH 8.5, broken short-rod structure with polydopamine CNS; (c) at pH 5.5 and dopamine concentration of 1.0 mg·mL-1, cross-linked network structure; (d) at pH 7.4 and dopamine concentration of 10.0 mg·mL-1, TMV embedded in polydopamine CNS structure. 2.3 Surface modification of nanofibers with AuNPs. The Polydopamine thin layer can reduce gold ions into AuNPs efficiently,17,23-24 which could be utilized as the surface modification for 1D inorganic-organic hybrid nanomaterial. After directly adding 10 µL 1 wt% chloroauric acid (HAuCl4) into the nanofiber solution, without any extra reductants, AuNPs were gradually grown on the exterior surface of nanofibers with dense coverage (Figure 6 and Figure S6). The size of AuNPs on nanofibers is 15-30 nm in spherical shape (Figure S7 a-b). These


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nanoparticles are gold polycrystalline, cubic crystal structure and the lattice constant is about 0.231 nm, which exactly accord with the characteristics of AuNPs, confirmed by the combination of high resolution TEM (HR-TEM), selected-area electron diffraction (SAED) and Energy-dispersive X-ray (EDX) spectroscopy (Figure S7 c-d and Figure S8, see Supporting Information).

Figure 6. (a-b) TEM images of AuNPs hybrid nanofibers. More images of AuNPs hybrid nanofibers are shown in supporting information Figure S6. The AuNPs-coating efficiency is depending on the HAuCl4 concentration in solution (Figure 7). It is a heterogeneous nucleation process. The catechol groups contained in polydopamine layer could serve as both the reductant of gold ions and the anchor for the resultant AuNPs.24 If we use a lower HAuCl4 concentration (adding 5 µL 1 wt% HAuCl4 aqueous solution into 2 mL nanofiber solution), the AuNPs coating density will be decreased sharply (Figure 7a). Whereas a higher HAuCl4 concentration (adding 50 µL 1 wt% HAuCl4 aqueous solution into 2 mL nanofiber solution) will cause bulk AuNPs formation and nanofiber aggregation by the reducing capacity of residual free dopamine in the solution (Figure 7c).23


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Figure 7. TEM images of the AuNPs coating when (a) 5 µL, (b) 10 µL and (c) 50 µL 1 wt% HAuCl4 aqueous solution was added into 2 mL nanofiber solution. 2.4 Observation of AuNPs hybrid nanofibers with HeLa cells. Cellular endocytic pathways play key roles in elucidating the bioactivity and cytotoxicity of nanoparticle.25 And the interaction of nanoparticles with cell membrane is critical process for the cellular endocytic pathway,26 which is considerable influenced by the size,27 shape,28 charge29 and surface composition30 of nanoparticles. The endocytic process of rod-like nanoparticles has initiated with upright docking position on cell membrane through a laying-down and standing-up sequence in theoretical simulation, significantly different from the spherical nanoparticles.31 However, actual observation of the cellular endocytic pathway for rod-like nanoparticles still remains a challenge. Nanofiber as one-dimensional (1D) nanomaterial with higher aspect ratio than nanorod may provide an ideal probe to sense the endocytic pathway of eukaryotic cells.32 In the eukaryotic cells, different cellular uptake pathways are available for nanoparticles. For some special nanoparticles, such as arginine-rich cell-penetrating peptides,33 they can directly penetrate through the cell membrane. And for most nanoparticles, they enter into eukaryotic cells through endocytosis, including caveolae-mediated endocytosis, clathrin-mediated endocytosis, micropinocytosis, phagocytosis and so on. Depending on the size of nanoparticles and the type of the cells, an endocytosis process is associated with cell membrane ruffles such as membrane invagination, vacuole formation or membrane extrusion induced by the activation of actin and


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microfilaments.34-35 To investigate the cellular uptake pathway of the fabricated AuNPs hybrid nanofibers, we co-incubated the AuNPs hybrid nanofibers with HeLa cells for 30 min, and then fixed the cells for TEM observation. It is shown from Figure 8 a-b that AuNPs hybrid nanofibers are forming small aggregates, which may result from the serum protein coating.28 TEM images also show the phenomena of membrane invagination and vacuole formation during the cellular uptake process of the AuNPs hybrid nanofibers, which are indicative of endocytosis (Figure 8 a-b). Furthermore, it is found that the intracellular localization is different depending on the aspect ratio of the AuNPs hybrid nanofibers. Short AuNPs hybrid nanofibers with low aspect ratio are localized in the cytoplasmic vesicles (Figure S9, see Supporting Information), whereas the long AuNPs hybrid nanofibers with high aspect ratio directly expose to the cytoplasm, without membrane surrounded (Figure 8 c-d).

Figure 8. TEM images of HeLa cells incubated with AuNPs hybrid nanofibers in 30 min, embedded in resin for ultrathin section at 70 nm. (a-b) show that HeLa cells uptake AuNPs


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hybrid nanofibers via vacuole formation; (c-d) show that AuNPs hybrid nanofibers with high aspect ratio stay in the cytoplasm, not in the cytoplasmic vesicles; (d) is enlarged view of (c). Compared with the fluorescence labelling and laser scanning confocal microscope (LSCM) method to observe the endocytic process of nanoparticles, this method showed advantages in much higher resolution (~0.2 nm for TEM and ~200 nm for LSCM), which could illustrate the ultrastructure of the cytoplasmic organelle, the nanofiber direction and the membrane structure around the nanofibers. 3. CONCLUSIONS We have demonstrated a two-step method to fabricate AuNPs hybrid nanofibers as 1D nanomaterial with TMV head-to-tail assembly assisted by polydopamine coating and deposited AuNPs on nanofiber surface for observing the pathway of cellular uptake. After being incubated with HeLa cells, the TEM images show that aggregated AuNPs hybrid nanofibers enter into the eukaryotic cell through endocytosis, and the 1D nanomaterial with high aspect ratio may stay directly in the cytoplasm, not in the cytoplasmic vesicles. Our work offers an effective AuNPs hybrid nanofibers probe for the observation of cellular uptake pathway and may inspire new application of 1D nanomaterial for cellular sensing, imaging and controlled cell entry in the future. 4. EXPERIMENTAL SECTION 4.1 Materials. 3,4-dihydroxyphenethylamine hydrochloride (Dopamine·HCl) was purchased from Sigma-Aldrich Co., Ltd. Ammonium persulfate (APS) was obtained from Beijing Biodee Biotechnology Co., Ltd. Chloroauric acid was bought from Shanghai Aladdin Industrial Inc. Dulbecco’s modified Eagle’s medium (DMEM), fetal bovine serum (FBS), penicillin,


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streptomycin and glutaraldehyde were purchased from Gibco Invitrogen. Sodium acetate (NaAc), tris(hydroxymethyl)aminomethane (Tris), dipotassium hydrogen phosphate (K2HPO4), acetic acid (HAc), hydrochloric acid (HCl) and citric acid were analytical grade and ordered from Beijing Chemical Works Co., Ltd. Dialysis membrane (Biotech Cellulose Ester, Molecular Weight Cut Off is 1,000,000 Daltons, MWCO 1,000,000) was bought from Spectrum Laboratories, Inc. Deionized water was obtained from Chengdu Pingchen ultrapure water system (18.25 MΩ·cm-1). Carbon-coated copper grids were purchased from Beijing Xinxing Braim Technology Co., Ltd. Uranyl acetate solution was ordered from Beijing Zhongjingkeyi Technology Co., Ltd. All other reagents were commercially available and used without further purification. 4.2 Instrumentation. 4.2.1 Ultraviolet-visible (UV-vis) Spectrometry. The absorption spectra of nanofiber solutions were measured by UV-3900 Spectrophotometer (Hitachi, Japan) at the wavelengths from 200 to 800 nm in room temperature. All samples were diluted with 5 times volume of deionized water and measured with time-point sampling in the reaction running time. 4.2.2 Transmission electron microscopy (TEM). The TEM images were obtained by JEM2100 transmission electron microscope (JEOL, Japan) at 200 kV accelerating voltage. The nanofiber samples were prepared by dropping 10 µL solutions on the carbon-coated copper grid for 10 min and drying with filter paper. Then the sample grids were placed inverted on 10 µL uranyl acetate solutions for negative staining and dried with filter paper. Some sample solutions were direct obtained in the reaction running time and diluted with 5 times volume of deionized water for TEM analysis. The high resolution TEM (HR-TEM) and selected-area electron diffraction (SAED) images were also obtained by JEM-2100 TEM.


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4.2.3 Scanning electron microscope (SEM). The SEM images were obtained by S-4800 scanning electron microscope (Hitachi, Japan) at 5 kV accelerating voltage. The nanofiber samples were prepared by submerging 1 mL solution in liquid nitrogen for 15 min and dehydrating in vacuum overnight. After the freeze dehydration process, the gray-brown powder was obtained, which was pasted on copper holder by conducting resin. Then the sample was sputtered gold coating in 45 seconds for SEM Observation. 4.2.4 Energy-dispersive X-ray (EDX) spectroscopy. The EDX data of AuNPs hybrid nanofibers was obtained by Inca X-Max (Oxford Instruments, UK) with SEM S-4800 at 5 kV accelerating voltage. 4.2.5 Zeta potential measurements. The zeta potential values of TMV, polydopamine CNS and nanofibers were measured by Zetasizer NanoZS 3600 (Malvern Instruments, UK). All samples were diluted with 10 times volume of deionized water, then the diluent was added 1 µL buffer solution (1 M Tris-HCl at pH 8.5 or 1 M potassium phosphate at pH 7.4) before injected to the testing cell. All samples were measured 3 times to calculate average values and deviations. 4.2.6 Dynamic light scattering (DLS). The DLS data of TMV and nanofibers were collected by Dynapro NanoStar (Wyatt Technology Corporation, US). All samples were diluted to 0.1 mg·mL-1 with deionized water before measured 3 times. 4.3 Isolation and purification of tobacco mosaic virus (TMV). Tobacco mosaic virus (TMV) was isolated according to the method reported previously.36 In briefly, infected tobacco leaves was crushed and homogenized, then filtered by 4 layers of gauze and centrifuged 20 min at 10,500 rpm 4 °C. The supernatant was mixed equally with the chloroform-butanol solution and stirred for 30 min in ice water, centrifuged 10 min at 6,000 rpm 4 °C subsequently. The aqueous solution portion was carefully separated. After that, 8% wt. poly (ethylene glycol) (Mw


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80,000, PEG8k) and 2% wt. sodium chloride were added to precipitate TMV. The mixture was stirred in ice water for 30 min and stored in freezer for 1 h, then centrifuged 15 min at 12,000 rpm 4 °C. The pellet was resuspended and centrifuged 15 min at 9,500 rpm 4 °C to remove extra PEG and other impurities. Pure TMV solution was obtained by final ultracentrifugation 3 h at 45,000 rpm 4 °C and then resuspended in deionized water overnight and kept in freezer for further use. 4.4 Preparation of polydopamine/TMV nanofibers. To prepare polydopamine/TMV nanofibers, 0.5 mg·mL-1 purified TMV was firstly dispersed in 5 mL NaAc-HAc buffer (pH 5.5, 50 mM). After adding 1.25 mg dopamine and 3.02 mg APS (the molar ratio of APS to dopamine is 2:1), the mixture was stirred for 4 h. Then the pH value of the mixture was adjusted to 7.8 by adding 0.1 M NaOH, and the mixture was kept stirring for 2 h. After dialysis against deionized water for 24 h to remove uncoated polydopamine, the polydopamine/TMV nanofibers were obtained. All experiments were performed in room temperature. In the above process, the acidic condition (pH 5.5) at the first stage is for the decreasing of TMV surface charge, the head-to-tail assembly of TMV and the depositing of polydopamine to fix the nanofiber structure. The neutral condition (pH 7.8) at the second stage is for the crosslinking and ageing of polydopamine shell. 4.5 Preparation of different co-assembly structure of polydopamine and TMV. To investigate the dopamine polymerization in different conditions, the mixture of TMV 2.5 mg and dopamine 2.5 mg were added to a series of buffer solutions 5 mL respectively, including buffer solutions with 50 mM concentration at pH 4.5 (NaAc-HAc), pH 5.5 (NaAc-HAc), pH 7.4 (Citric acid-K2HPO4), pH 8.0 (Tris-HCl), and pH 8.5 (Tris-HCl). APS was added in acidic buffers solutions with the molar ratios of APS to dopamine 1:2, 1:1 and 2:1, separately. The extent of


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reaction of dopamine for 24 h polymerization was monitored by UV-vis spectrometer (Figure S3 b-c). The effect of different dopamine concentrations was also investigated by adding dopamine 0.1, 0.3, 0.5, 0.7, and 1.0 mg·mL-1 to NaAc-HAc buffer solution (pH 5.5, 50 mM, 5 mL) with APS in the molar ratio of 1:2, respectively. Another series experiments with dopamine concentration of 2.0, 4.0, 6.0, 8.0 and 10.0 mg·mL-1 in Tris-HCl buffer solution (pH 8.5, 10 mM, 5 mL) were tested as well. The concentration of TMV was 0.5 mg·mL-1 in all experiments and other conditions were the same as mentioned above. 4.6 Preparation and Characterization of AuNPs hybrid nanofibers. After dialyzing against deionized water overnight, 2 mL nanofiber solution (0.5 mg mL-1) was mixed with 10 µL HAuCl4 aqueous solution (1 wt%). The mixture was shook for a while, and then kept in dark for 24 h to get final AuNPs hybrid nanofibers 1D nanomaterial. The sample was analyzed by TEM with negative staining. HR-TEM images indicated that the lattice constant of the nanoparticles was 0.231 nm, which is in accordance with (111) crystal face of gold (d = 0.236 nm) belonging to cubic crystal structure (Figure S7c). SAED image illustrated that the nanoparticles were polycrystalline with 0.237 nm lattice constant, fitting in with gold cubic crystal structure (Figure S7d). All the results were measured and analyzed by ImageJ software v1.50. 4.7 Cell Culture. HeLa cells (human cervical cancer epithelial cell) were incubated in DMEM medium with 1% penicillin-streptomycin and 10% FBS at 37 °C in a humidified atmosphere containing CO2 5% (v/v).


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4.8 Incubation of AuNPs hybrid nanofibers with HeLa cells. HeLa cells were seeded and incubated in 5 cm plastic culture plate overnight. Then AuNPs hybrid nanofibers 1D nanomaterial 50 µL (0.5 mg·mL-1) were dispersed in culture medium and incubated with the cells for 30 min. After removing the medium and washing thrice with PBS, the cells were fixed with 2.5 % glutaraldehyde 2 mL at room temperature. The ultrathin section of HeLa cells incubated with AuNPs hybrid nanofibers was observed by TEM after fixing, dehydration, embedding and slicing process. ASSOCIATED CONTENT Supporting Information The Supporting Information is available: TEM images of nanofibers for statistical analysis of the length and diameter distribution, UV-vis spectra of nanofibers reaction, zeta potential of nanofibers measured at pH 7.4 & 8.5, SEM images of nanofibers after dialysis and freeze dehydration process, TEM images of AuNPs hybrid nanofibers, HR-TEM, SAED images and EDX spectroscopy of AuNPs, and TEM images of intracellular distribution of AuNPs hybrid nanofibers in HeLa cells. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] (Z.N) *E-mail: [email protected] (Y.T) Notes The authors declare no competing financial interest.


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ACKNOWLEDGMENT We gratefully acknowledge the National Natural Science Foundation of China (Grant No. 21474123, 21304103, 51303191 and 51173198), the Ministry of Science and Technology of the People’s Republic of China (Grant No. 2013CB933800) and Youth Innovation Promotion Association of the Chinese Academy of Sciences (2017039). REFERENCES (1) Xia, Y.; Yang, P.; Sun, Y.; Wu, Y.; Mayers, B.; Gates, B.; Yin, Y.; Kim, F.; Yan, H. Onedimensional nanostructures: synthesis, characterization, and applications. Adv. Mater. 2003, 15, 353-389. (2) Descalzo, A.B.; Martínez-Máñez, R.; Sancenón, F.; Hoffmann, K.; Rurack, K. The supramolecular chemistry of organic-inorganic hybrid materials. Angew. Chem., Int. Ed. 2006, 45, 5924-5948. (3) Yuan, J.; Müller, A.H.E. One-dimensional organic–inorganic hybrid nanomaterials. Polymer 2010, 51, 4015-4036. (4) Mirkin, C.A.; Letsinger, R.L.; Mucic, R.C.; Storhoff, J.J. A DNA-based method for rationally assembling nanoparticles into macroscopic materials. Nature 1996, 382, 607-609. (5) Zhang, T.; Wang, W.; Zhang, D.; Zhang, X.; Ma, Y.; Zhou, Y.; Qi, L. Biotemplated synthesis of gold nanoparticle-bacteria cellulose nanofiber nanocomposites and their application in biosensing. Adv. Funct. Mater. 2010, 20, 1152-1160. (6) Acar, H.; Genc, R.; Urel, M.; Erkal, T.S.; Dana, A.; Guler, M.O. Self-assembled peptide nanofiber templated one-dimensional gold nanostructures exhibiting resistive switching. Langmuir 2012, 28, 16347-16354. (7) Dujardin, E.; Peet, C.; Stubbs, G.; Culver, J.N.; Mann, S. Organization of metallic nanoparticles using tobacco mosaic virus templates. Nano Lett. 2003, 3, 413-417. (8) Liu, N.; Wang, C.; Zhang, W.; Luo, Z.; Tian, D.; Zhai, N.; Zhang, H.; Li, Z.; Jiang, X.; Tang, G.; Hu, Q. Au nanocrystals grown on a better-defined one-dimensional tobacco mosaic virus coated protein template genetically modified by a hexahistidine tag. Nanotechnology 2012, 23, 335602.


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(9) Liu, Z.; Qiao, J.; Niu, Z.; Wang, Q. Natural supramolecular building blocks: from virus coat proteins to viral nanoparticles. Chem. Soc. Rev. 2012, 41, 6178-6194. (10) Shenton, W.; Douglas, T.; Young, M.; Stubbs, G.; Mann, S. Inorganic-organic nanotube composites from template mineralization of tobacco mosaic virus. Adv. Mater. 1999, 11, 253-256. (11) Niu, Z.; Bruckman, M.; Kotakadi, V.S.; He, J.; Emrick, T.; Russell, T.P.; Yang, L.; Wang, Q. Study and characterization of tobacco mosaic virus head-to-tail assembly assisted by aniline polymerization. Chem. Commun. 2006, 28, 3019-3021. (12) Niu, Z.; Bruckman, M.A.; Li, S.; Lee, L.A.; Lee, B.; Pingali, S.V.; Thiyagarajan, P.; Wang, Q. Assembly of tobacco mosaic virus into fibrous and macroscopic bundled arrays mediated by surface aniline polymerization. Langmuir 2007, 23, 6719-6724. (13) Niu, Z.; Liu, J.; Lee, L.A.; Bruckman, M.A.; Zhao, D.; Koley, G.; Wang, Q. Biological templated synthesis of water-soluble conductive polymeric nanowires. Nano lett. 2007, 7, 3729-3733. (14) Liu, Y.; Ai, K.; Lu, L. Polydopamine and its derivative materials: synthesis and promising applications in energy, environmental, and biomedical fields. Chem. Rev. 2014, 114, 50575115. (15) d'Ischia, M.; Napolitano, A.; Ball, V.; Chen, C.T.; Buehler, M.J. Polydopamine and eumelanin: from structure-property relationships to a unified tailoring strategy. Acc. Chem. Res. 2014, 47, 3541-3550. (16) Hong, S.; Na, Y.S., Choi, S.; Song, I.T.; Kim, W.Y.; Lee, H. Non-covalent self-Assembly and covalent polymerization co-contribute to polydopamine formation. Adv. Funct. Mater. 2012, 22, 4711-4717. (17) Lee, H.; Dellatore, S.M.; Miller, W.M.; Messersmith, P.B. Mussel-inspired surface chemistry for multifunctional coatings. Science 2007, 318, 426-430. (18) Ouyang, R.; Lei, J.; Ju, H. Surface molecularly imprinted nanowire for protein specific recognition. Chem. Commun. 2008, 44, 5761-5763. (19) Wei, Q.; Zhang, F.; Li, J.; Li, B.; Zhao, C. Oxidant-induced dopamine polymerization for multifunctional coatings. Polym. Chem. 2010, 1, 1430-1433. (20) Lu, B.; Stubbs, G.; Culver, J.N. Carboxylate interactions involved in the disassembly of tobacco mosaic tobamovirus. Virology 1996, 225, 11-20.


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Table of Contents Graphic


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Scheme 1. Preparation of AuNPs hybrid nanofibers as 1D nanomaterial for endocytic observation. 64x50mm (300 x 300 DPI)


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Figure 1. TEM images of (a) TMV; (b) polydopamine/TMV nanofibers; (c) a single nanofiber at length of 2,142 nm; (d) a single nanofiber at diameter of 23.5 nm. 691x691mm (72 x 72 DPI)


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Figure 2. Statistical analysis for the length distribution (a) and diameter distribution (b) of nanofibers. 70x29mm (300 x 300 DPI)


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Figure 3. DLS data of TMV and polydopamine/TMV nanofibers. 66x51mm (300 x 300 DPI)


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Figure 4. SEM image of polydopamine/ TMV nanofibers after dialysis and freeze dehydration. 85x85mm (300 x 300 DPI)


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Figure 5. TEM images of the polydopamine/TMV nanofiber prepared at different pH value and dopamine concentration. (a) at pH 4.2, bundle like structure; (b) at pH 8.5, broken short-rod structure with polydopamine CNS; (c) at pH 5.5 and dopamine concentration of 1.0 mg·mL-1, cross-linked network structure; (d) at pH 7.4 and dopamine concentration of 10.0 mg·mL-1, TMV embedded in polydopamine CNS structure. 83x83mm (600 x 600 DPI)


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Figure 6. (a-b) TEM images of AuNPs hybrid nanofibers. More images of AuNPs hybrid nanofibers are shown in supporting information Figure S6. 87x44mm (300 x 300 DPI)


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Figure 7. TEM images of the AuNPs coating when (a) 5 µL, (b) 10 µL and (c) 50 µL 1 wt% HAuCl4 aqueous solution was added into 2 mL nanofiber solution. 37x8mm (300 x 300 DPI)


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Figure 8. TEM images of HeLa cells incubated with AuNPs hybrid nanofibers in 30 min, embedded in resin for ultrathin section at 70 nm. (a-b) show that HeLa cells uptake AuNPs hybrid nanofibers via vacuole formation; (c-d) show that AuNPs hybrid nanofibers with high aspect ratio stay in the cytoplasm, not in the cytoplasmic vesicles; (d) is enlarged view of (c). 87x87mm (300 x 300 DPI)


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Table of Contents Graphic 29x11mm (300 x 300 DPI)


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Mussel-Inspired Polydopamine Coating on Tobacco Mosaic Virus

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