Protein-Induced Gold Nanoparticle Assembly for Improving the

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Protein-Induced Gold Nanoparticle Assembly for Improving the Photothermal Effect in Cancer Therapy Jie Wang,† Ying Zhang,† Na Jin,† Chuanbin Mao,*,‡,§ and Mingying Yang*,†

ACS Appl. Mater. Interfaces Downloaded from pubs.acs.org by UNIV OF TEXAS AT DALLAS on 03/14/19. For personal use only.

†

Institute of Applied Bioresource Research, College of Animal Science, Zhejiang University, Yuhangtang Road 866, Hangzhou, 310058 Zhejiang, China ‡ Department of Chemistry & Biochemistry, Stephenson Life Science Research Center, Institute for Biomedical Engineering, Science and Technology, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma 73019-5251, United States § School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, China S Supporting Information *

ABSTRACT: Gold nanoparticles (AuNPs) are promising photothermal agents for cancer therapy. However, the absorption of spherical AuNPs is weak in the desired tissue-penetrating near-infrared (NIR) window, resulting in low photothermal efficiency within this window. Here, we show that fibrous nanostructures assembled from spherical AuNPs since the templating effect of silk fibroin (SF) could red-shift the optical absorption to NIR and thus present improved photothermal efficiency within the NIR window. Specifically, negatively charged SF, a protein derived from Bombyx mori, was assembled into nanofibers due to the interaction with the positively charged AuNPs and concomitantly templated the AuNPs into fibrous nanostructures. The resultant AuNPs/SF nanofibers presented higher NIR light absorption at 808 nm and higher photothermal efficiency under 808 nm NIR irradiation than nonassembled AuNPs. In vitro and in vivo analyses proved that AuNPs/SF nanofibers could efficiently kill breast cancer cells and destruct breast cancer tumor tissues under one-time NIR irradiation for 6 min by photothermal therapy (PTT) but nonassembled AuNPs could not. This work suggests that the selfassembled AuNPs/SF nanofibers are effective photosensitizers for PTT, and biotemplated assembly of photothermal agents into highly ordered nanostructures is a promising approach to increasing the PTT efficiency. KEYWORDS: gold nanoparticles, silk fibroin, biotemplates, assembly, photothermal cancer therapy applications.27−29 For instance, amphiphilic block copolymers can control the formation of various AuNP assemblies for improving the efficiency of PTT.30 AuNPs aggregated into the form of liposomes can also enhance the photothermal efficiency.31 This proves that turning on a template to drive AuNPs to be assembled into aggregates is a possible route to improve the efficiency of PTT. Therefore, it is urgent to find out an ideal biotemplate that is green and capable of controlling the self-assembly of AuNPs. Silk fibroin (SF) spun from Bombyx mori silkworm is a fibrous protein.32 It has unique characteristics including biocompatibility, plasticity, and green synthesis.33−36 In addition to the application in tissue engineering, SF is a perfect biotemplate for mediating the mineralization.37−39 This is because the primary structure of SF, including negatively charged amino acids like glutamic acid (Glu) and aspartic acid (Asp), is prone to bind cations such as Ca2+ and consequently drives the self-assembly of SF resulting in mineralization.40 SF is also used as a template, successfully mediating the nucleation

1. INTRODUCTION Photothermal therapy (PTT) has become an increasingly attractive cancer therapy with advantages such as controllability and high-efficiency without side effects.1−5 PTT uses nanomaterials to convert light into heat for killing cancer cells. These nanomaterials called photosensitizers include gold nanomaterials, 6,7 Fe 3 O 4 nanoparticles, 8,9 carbon nanotubes,10,11 graphene oxide,12,13 and black phosphorus.14 Specifically, gold nanomaterials have been used as photosensitizers for PTT because of their great photothermal conversion ability and stability.15−17 In particular, gold nanoparticles (AuNPs), the first-studied gold nanomaterials, can be easily prepared and are biocompatible.18−20 However, the low light absorption of AuNPs in the near-infrared (NIR) window results in their low photothermal conversion in this window although the NIR light has stronger tissue penetration capability and better tissue compatibility than visible light in light-triggered cancer therapy.21−24 Accordingly, the Mie theory proposed that induction of AuNP aggregation can generate a red shift for the light absorption peak and consequently improve PTT in the NIR window.25,26 Selfassembly of AuNPs mediated by other materials was accepted as an effective way to improve their performance in biomedical © XXXX American Chemical Society

Received: December 8, 2018 Accepted: March 4, 2019

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DOI: 10.1021/acsami.8b21488 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces

Figure 1. Schematic diagram of the templated assembly of AuNPs on SF fibers into AuNPs/SF nanofibers and their use in photothermal breast tumor destruction. (A) Schematic describing the regulation process of AuNPs by SF. (B) Proposed schematic representing the templated assembly of AuNPs by SF nanofibers. (C) AuNPs/SF nanofibers were injected into the tumor site. (D) 808 nm laser was irradiated on the MCF-7 breast cancer tumor. (E) The tumor was destructed. (a) SF solution was prepared by dissolving the cocoons with LiBr. (b) AuNPs were interacted with SF in a solution. (c) SF with a secondary structure of random coil was negatively charged. (d) AuNPs were positively charged after modification with PEI. (e) The AuNPs/SF nanofibers were formed due to the electrostatic interaction between the AuNPs and SF.

and assembly of silica nanoparticles.41 Hence, here we speculated that SF could serve as a biotemplate by binding Au to trigger the self-assembly of SF and to drive the aggregation of AuNPs, leading to aggregated AuNPs that can improve PTT efficiency. As far as we know, there has been no report on using SF as a biotemplate to regulate AuNP assembly into a material for improving the efficiency of PTT for tumor therapy. To test our assumption, we first prepared SF solution by dissolving B. mori silkworm cocoons. The aqueous SF solution has negative surface potential under neutral conditions. At the same time, we synthesized positively charged AuNPs by surface modification with polyethyleneimine (PEI) according to a previous protocol.42 The electrostatic attraction between the negatively charged SF and positively charged AuNPs would enable the formation of SF nanofibers due to the transition of the secondary structure from random coils to β-sheets, to template the assembly of AuNPs into AuNPs/SF nanofibers (Figure 1). Therefore, the AuNPs/SF nanofibers are expected to have red-shifted the light absorption in the NIR region and thus show improved PTT in comparison to monodispersed AuNPs.

that, 10 mM freshly prepared NaBH4 aqueous solution was added dropwise until the solution color stopped changing. According to the varying electric potential of SF at different pH values (Figure S1A), the pH of the AuNPs colloidal solution was adjusted to 4.5−5.0 with 10 mM NaOH for further use. Moreover, PEI with a larger molecular weight of 10 000 Da was also used to synthesize AuNPs for studying its effect on the assembly. 2.3. Preparation of Aqueous SF Solution. The aqueous SF solution was extracted from cocoons of B. mori silkworm based on our previous protocol.45 Briefly, cocoons were placed into a boiled aqueous solution with 0.5 wt % Na2CO3 for degumming the sericin twice. Then, the silk fiber was dried naturally and dissolved with 9.3 M LiBr solution. The resultant mixture was subject to dialysis against deionized water for 3 days to remove LiBr. The SF solution was then filtered and purified by centrifugation. Finally, the aqueous SF solution was obtained and kept at 4 °C for further experiments. 2.4. SF-Mediated AuNPs To Form Ordered Self-Assembly Arrangement. For regulating the assembly of AuNPs, 300 μL of SF solution with varying concentrations (50−200 μg mL−1) was slowly added to 1 mL of the prepared AuNP solution under sustained oscillation. In the solution, SF was assembled into nanofibers. After that, the colloidal AuNPs were allowed to interact with the SF nanofibers for different time periods (2, 4, 6, and 24 h). Then, the resultant AuNPs/SF nanofibers were collected through centrifugation at 8000 rpm for 5 min. They were then cleaned with deionized water a few times and resuspended into 200 μL of deionized water. 2.5. Characterization of AuNPs/SF Nanofibers. The morphologies of AuNPs/SF nanofibers were visualized using transmission electron microscopy (TEM). The samples were first diluted 5−10 times with deionized water, and 10 μL of the diluent was dropped onto a formvar-covered copper grid for observation. The absorbance spectra of SF, AuNPs, and AuNPs/SF nanofibers were recorded using a UV-Vis spectrophotometer. The secondary structure of SF and AuNPs/SF nanofiber solution was measured by circular dichroism (CD) at room temperature. The ζ potential and size distribution of AuNPs, AuNPs/SF nanofibers, and SF solution at different pH values were measured using Zetasizer NANO-ZS90 (Malvern Instruments, Malvern, UK) based on photon correlation spectroscopy. The concentration of the SF solution was 100 μg mL−1 for each measurement.

2. MATERIALS AND METHODS 2.1. Materials. B. mori silkworm cocoons were provided by the Institute of Huzhou Fiber Inspection, China. Lithium bromide (LiBr ≥ 95%), gold chloride trihydrate (HAuCl4·3H2O, 99.99%), sodium borohydride (NaBH4), and branched polyethyleneimine (PEI) with molar masses of 1800 and 10 000 Da were purchased from Aladdin Reagent. Dulbecco’s modified Eagle’s medium (DMEM) with 4.5 g L−1 glucose, 1% penicillin−streptomycin, fetal bovine serum (FBS), and trypsin with 0.25% EDTA were all purchased from Gibco. 2.2. Synthesis of Colloidal AuNPs. Colloidal AuNPs were synthesized according to the reported procedures with slight modification.43,44 Briefly, 15% PEI (Mw = 1800 Da) with varying volumes (1, 2, and 3 μL) was dispersed in 850 μL of deionized water with gentle stirring. Then, 150 μL of 12 mM HAuCl4 was mixed with the above solution, followed by continuous stirring for 5 min. After B

DOI: 10.1021/acsami.8b21488 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces

Figure 2. CD spectra and TEM images of AuNPs/SF nanofibers describing the arrangement and self-assembly of AuNPs into fibrous structures by SF. (a) The CD spectra of SF and AuNPs/SF nanofibers. (b−f) TEM images of AuNPs/SF nanofibers mediated by SF with varying concentrations: (b) 0, (c) 50 μg mL−1, (d) 100 μg mL−1, (e) 150 μg mL−1, and (f) 200 μg mL−1. The incubation time between AuNPs and SF solution was set as 2 h, and the molecular weight and volume of PEI were chosen as 1800 Da and 2 μL. μL single-cell suspension of MCF-7 cells with a number of (2−3) × 106 into the back of each mouse. After tumors grew to reach a diameter of appropriately 5 mm, the tumor-bearing mice were randomly divided into three groups (n = 4): PBS group, AuNP group, and AuNPs/SF nanofiber group. Then, 50 μL of PBS, AuNPs, or AuNPs/SF nanofiber solution (100 μg mL−1) was intratumorally injected in each treatment group, respectively. After 30 min of injection, tumors received irradiation of an 808 nm laser at 4 W cm−2 for 6 min. During the process of laser irradiation, the temperature of the tumor site of mice was recorded with an infrared camera every 30 s. The tumor size was recorded every other day after photothermal treatment. Two weeks later, all the mice were euthanized and the tumors were collected for weighing and H&E staining analysis.

2.6. Photothermal Study of AuNPs/SF Nanofibers. 2.6.1. Measurement of the Temperature Change of AuNPs/SF Nanofiber Solution. Since the NIR light could penetrate tissues deeper, the NIR laser with a wavelength of 808 nm was used here to trigger photothermal therapy. Then, the temperature change of the aqueous solution of AuNPs or AuNPs/SF nanofibers was measured. The sample solutions in a quartz cuvette with a concentration of Au particles at 100 μg mL−1 were irradiated by an 808 nm laser with a power intensity at 4 W cm−2 for 6 min. An infrared camera (FLTR S65) was used to record the temperature of the solutions every 30 s. The change in the temperature of PBS was also recorded as a control. Then, the photothermal conversion efficiency (η) of AuNPs and AuNPs/SF nanofibers was calculated according to earlier reports46,47 and using the following equation η=

3. RESULTS AND DISCUSSION 3.1. SF-Mediated Self-Assembly of AuNPs. As we expected, electrostatic attraction between the cationic AuNPs and anionic SF triggered the change of the secondary structure of the SF from random coils to β-sheets (Figure 2a), proving that SF can regulate the assembly of AuNPs. Therefore, addition of the SF solution into AuNPs solution induced the self-assembly of AuNPs into nanofibers (Figure 2c−f). The color change of nanoparticle solutions and the transformation of the size and potential of AuNPs/SF nanofibers also indicated that SF induced the self-assembly of AuNPs (Figure S2). We previously confirmed that the secondary structural transition from random coils to β-sheets could induce the SF to be assembled into nanofibers.49 The conformation balance of SF will be broken in the presence of cations because of electrostatic attraction.50−52 Thus, addition of positively charged AuNPs accelerated the unbalanced process and in turn promoted the formation of β-sheets in the SF. In the absence of SF, AuNPs were not assembled into the nanofibers (Figure 2b). To further prove our speculation that electrostatic interaction resulted in the self-assembly of AuNPs on the SF nanofibers, we used SF as a template to regulate the negatively charged AuNPs and the positively charged silver nanoparticles (AgNPs), respectively. Indeed, SF could not induce the assembly of the negatively charged AuNPs into nanofibers (Figure S1B). However, SF can regulate the positively charged AgNPs to be assembled into nanofibers (Figure S1C). These results further verified our hypothesis that SF could really regulate the self-assembly of AuNPs into nanofibers through

hA(ΔTmax,mix − ΔTmax,H2O) −Aλ

I(1 − 10

)

where h is the heat transfer coefficient, A is the container surface area, ΔTmax,mix and ΔTmax,H2O are the change in the temperature of AuNPs or AuNPs/SF nanofibers and the solvent (water) for reaching the maximum steady-state temperature, respectively. I is the laser power, and Aλ is the absorbance of AuNPs or AuNPs/SF nanofibers at 808 nm. In this study, the concentration of AuNPs was defined as the content of gold that can be determined by combining UV−vis spectra with inductively coupled plasma test according to the reported study.48 2.6.2. In Vitro Photothermal Therapy. MCF-7 cells (from the cell bank of the Chinese Academy of Sciences) were cultured in DMEM with 10% FBS until the desired density was reached. Then, the cells were digested and cultured on 96-well plates for 24 h with a density of 1 × 104 cells per well. After that, the medium was replaced with 100 μL of fresh medium containing AuNPs or AuNPs/SF nanofibers with the concentration varying from 50, 100, to 150 μg mL−1. Then, the cells were coincubated with nanoparticles for half an hour and irradiated with the 808 nm laser with a power density of 4 W cm−2 for 6 min. Finally, the cells were washed with PBS 2 times and fresh medium was added again. The cell viability was determined by using the Cell Counting Kit-8 (CCK-8, Dojindo). The treated cells were also stained with acridine orange (AO)/ethidium bromide (EB) dye (Solarbio, Beijing) to directly differentiate live and dead cells, which would be stained by green and red colors, respectively. 2.6.3. In Vivo Photothermal Therapy. Nude mice (BALB/c, 4 weeks, female) from Shanghai Slak laboratory animal Co., Ltd. were used for the in vivo study. Animal studies were approved by the Zhejiang University Institutional Animal Care and Use Committee. Tumor-bearing mice were prepared by subcutaneous injection of 100 C

DOI: 10.1021/acsami.8b21488 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces electrostatic attraction between SF and AuNPs as illustrated in Figure 1. Furthermore, we found that not only the concentrations of SF solution but also the incubation times and PEI concentrations would determine the morphology of AuNPs/ SF nanofibers. SF having low concentrations of 50 and 100 μg mL−1 resulted in the ordered and dense arrangement of AuNPs on both sides of the nanofibers (Figure 2c,d). Increasing the SF concentration to 150 or 200 μg mL−1 led to AuNPs being sporadically distributed along the assembly of AuNPs/SF nanofibers (Figure 2e,f). Conversely, prolonging the incubation time would enable the SF to attract more AuNPs, resulting in more AuNPs on the SF (Figure S3). As PEI is a key reagent on the synthesis of metal nanoparticles,53−55 it was expected to also affect the density and size of AuNPs in AuNPs/SF nanofibers. PEI with a larger molecular weight (10 kDa) led to a lower density of AuNPs being assembled on the nanofibers (Figure S4A) than that with a smaller molecular weight (1800 Da). This may be because longer branches of PEI caused greater steric hindrance that kept AuNPs from getting close to each other on the nanofibers. In addition, PEI concentration determined the size of AuNPs, and larger-sized AuNPs were synthesized when the concentration was reduced (Figure S4B,C), indicating that PEI is effective in modifying AuNPs. 3.2. Photothermal Effect of the AuNPs/SF Nanofibers in Vitro. We selected the AuNPs/SF nanofibers in Figure 2d as photosensitizers for studying the photothermal effect in consideration of the assembly density of AuNPs and the stability of nanofibers in solution. The AuNPs/SF nanofibers maintained great stability in different solution systems as evidenced by good dispersion and unchanged ζ potential after storage for a long time (Figure S5). The monodispersed AuNPs showed a sharp, narrow absorption peak at around 520 nm (Figure S6), consistent with the previously reported results.56 We found that the AuNPs/SF nanofibers really resulted in broadening and red shift of the localized surface plasmon resonance band compared to the monodispersed AuNPs. In particular, the AuNPs/SF nanofibers significantly enhanced the optical absorption in the NIR window. We further investigated whether the AuNPs/SF nanofibers could improve the photothermal conversion ability by laser irradiation of the AuNP suspension and AuNPs/SF nanofiber suspension at 808 nm wavelength, respectively. After laser irradiation for 6 min, no temperature change was observed with the control (PBS buffer solution). However, the temperature of the AuNPs/SF nanofiber suspension finally reached nearly 55 °C, but the temperature of the monodispersed AuNPs only reached nearly 48 °C (Figure 3A). The photothermal conversion efficiency (η) of AuNPs/ SF nanofibers was calculated to be 38.42%, which was higher than that of AuNPs (28.81%) according to the temperature change (ΔT) profiles (Figure S7). This indicates that the AuNPs/SF nanofibers have a higher photothermal conversion efficiency than the monodispersed AuNPs, proving that SF is a suitable biotemplate for regulating the assembly of AuNPs into nanofibers that can improve the photothermal conversion efficiency of AuNPs. We further evaluated the photothermal efficiency of AuNPs/ SF nanofibers in vitro. The biosafety of AuNPs/SF nanofibers was first evaluated. The MCF-7 cells had a viability over 90% after being coincubated with AuNPs or AuNPs/SF nanofibers at various concentrations for 24 h (Figure S8), indicating that

Figure 3. In vitro photothermal therapy by AuNPs/SF nanofibers. (A) Temperature evaluation of AuNPs, AuNPs/SF nanofibers, and PBS with 808 nm laser irradiation. (B) Cell viability of MCF-7 cells treated with AuNPs or AuNPs/SF nanofibers after irradiation with an 808 nm laser for 6 min at a power density of 4 W cm−2. (C) Live/ Dead Cell Staining Kit stained images of MCF-7 cells treated with AuNPs or AuNPs/SF nanofibers.

the nanoparticles were biocompatible. After laser irradiation for 6 min, the cell viability in the presence of the monodispersed AuNPs and the AuNPs/SF nanofibers (with a concentration of Au at 50 μg mL−1) was 70 and 50%, respectively (Figure 3B). When the Au concentration was increased and reached 100 μg mL−1, the cell viability of the monodispersed AuNPs decreased to 40%, but nearly 100% cells were dead in the group of AuNPs/SF nanofibers. When the Au concentration became even higher (150 μg mL−1), 10% of cells were still alive in the monodispersed AuNPs group. These data showed that AuNPs/SF nanofibers could destroy more MCF-7 cells than monodispersed AuNPs at the same concentration of Au. Additionally, fluorescence images were obtained to visualize the tumor cell death status (Figure 3C). By keeping the concentration of Au at 50 μg mL−1, no dead cells were observed in the monodispersed AuNP group, whereas over 50% of the cells were dead in the AuNPs/SF nanofiber group. When the Au concentration was increased to 100 μg mL−1, nearly 50% of cells were dead in the monodispersed AuNPs group, but no cells survived in the AuNPs/SF nanofiber group. Therefore, the results from both cell viability and AO/EB staining proved that AuNPs/SF nanofibers have a higher photothermal conversion efficiency and thus a higher efficiency of killing MCF-7 cells than monodispersed AuNPs at the same Au concentration. 3.3. Evaluation of the Photothermal Effect of AuNPs/ SF Nanofibers in Vivo. To further confirm that AuNPs/SF nanofibers could destruct tumors more efficiently by PTT than monodisperse AuNPs, NIR laser irradiation (808 nm wavelength) was applied to the tumors 30 min after intratumoral injection of AuNPs/SF nanofibers and AuNPs, respectively. The infrared thermal images showed that a faster temperature rise was observed in the tumors injected with AuNPs/SF nanofibers than in those injected with PBS or AuNPs (Figure D

DOI: 10.1021/acsami.8b21488 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

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ACS Applied Materials & Interfaces

Figure 4. In vivo photothermal therapy using assembled AuNPs/SF nanofibers. (A) Real-time recording of temperature change inside tumors during the laser irradiation by an infrared camera. (B) Photographs of a typical mouse in each group on day 1, day 7, and day 14 post-treatment. (C) Post-treatment tracking of relative tumor volume in different groups for 2 weeks. (D) Representative photographs of tumors of different groups after the tumors were taken out of mice. (E) Tumor weight of different groups on day 14 after the laser irradiation. (F) H&E-stained tumor images in different treatment groups.

tumors and even made the tumors nearly disappear finally (Figure 4C). On the contrary, injected PBS and AuNPs did not suppress the rapid tumor growth when the volume of tumors increased and reached a value several times that of the initial value. On the 14th day, the size of the tumors treated by the AuNPs/SF nanofibers was significantly reduced compared to that of the tumors treated by AuNPs or PBS (Figure 4D). The tumor weight was the lowest when the tumors were treated by AuNPs/SF nanofibers (Figure 4E). H&E staining showed fewer cells and shrinking cell nuclei in the tumor tissues, indicating that the tumor tissues were destroyed by AuNPs/SF nanofibers, whereas cell nuclei were normal in the tumor tissues injected with PBS or AuNPs (Figure 4F). The H&E staining suggested that tumors were more effectively destructed in the AuNPs/SF nanofiber group than the other

4A). Furthermore, the maximum tumor temperature in the AuNPs/SF nanofiber group could also reach 55 °C, consistent with the temperature measured in vitro. Then, we observed the appearance of tumors after photothermal treatment. As shown in Figure 4B, on the 1st day after laser irradiation, tumors injected with the AuNPs/SF nanofibers suffered the most serious burning but those injected with PBS and AuNPs suffered less burning. After 7 days of irradiation, the surface skin of tumors in all groups had already been scabbed. After 14 days of irradiation, the scarred area of the tumors injected with the AuNPs/SF nanofibers has been reduced notably and recovered to become flat. In contrast, the tumors in the other two groups both grew larger than before. We also recorded the change in the tumor volumes every other day. Injected AuNPs/SF nanofibers significantly inhibited the growth of E

DOI: 10.1021/acsami.8b21488 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

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ACS Applied Materials & Interfaces

Fundamental Research Funds for the Central Universities (2018XZZX001-11), State of Sericulture Industry Technology System (CARS-18-ZJ0501), and Zhejiang Provincial Science and Technology Plans (2016C02054-19). C.B.M. would also like to thank the financial support from the National Institutes of Health (EB021339) and Office of Basic Energy Sciences within the Department of Energy (DE-SC0016567).

groups. In addition, the stability of mice weight during photothermal treatment also confirmed the biosafety of AuNPs/SF nanofibers (Figure S9). Therefore, the in vivo experiments further demonstrated that the AuNPs/SF nanofibers had a higher photothermal therapy efficiency on tumors.

4. CONCLUSIONS To improve the photothermal therapy efficiency of gold nanoparticles in the NIR window, this study successfully applied a biotemplate of self-assembled SF nanofibers to regulate the AuNP self-assembly. Driven by electrostatic attraction, AuNPs were assembled into nanofibers on the SF nanofiber templates. The morphology of the resultant AuNPs/ SF nanofibers was controlled by the concentration of SF and incubation time. The AuNPs/SF nanofibers exhibited a redshifted absorption band in the NIR window and could convert the absorbed light energy into heat, resulting in a higher temperature of AuNPs/SF nanofibers than monodispersed AuNPs under the same 808 nm NIR laser irradiation. The in vitro experiment proved that AuNPs/SF nanofibers could more effectively kill tumor cells. The in vivo test also showed that AuNPs/SF nanofibers inhibited tumor growth more effectively than AuNPs by PTT. This work suggested that AuNPs/SF nanofibers produced due to the biotemplated assembly of AuNPs are potential therapeutic agents in photothermal cancer therapy.

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(1) Svaasand, L.; Gomer, C.; Morinelli, E. On the Physical Rationale of Laser Induced Hyperthermia. Lasers Med. Sci. 1990, 5, 121−128. (2) Kennedy, L. C.; Bickford, L. R.; Lewinski, N. A.; Coughlin, A. J.; Hu, Y.; Day, E. S.; West, J. L.; Drezek, R. A. A New Era for Cancer Treatment: Gold-Nanoparticle-Mediated Thermal Therapies. Small 2011, 7, 169−183. (3) Huang, X.; El-Sayed, I. H.; Qian, W.; El-Sayed, M. A. Cancer Cell Imaging and Photothermal Therapy in the Near-Infrared Region by Using Gold Nanorods. J. Am. Chem. Soc. 2006, 128, 2115−2120. (4) Chen, J. Q.; Ning, C. Y.; Zhou, Z. N.; Yu, P.; Zhu, Y.; Tan, G. X.; Mao, C. B. Nanomaterials as Photothermal Therapeutic Agents. Prog. Mater. Sci. 2019, 99, 1−26. (5) Qu, X. W.; Qiu, P. H.; Zhu, Y.; Yang, M. Y.; Mao, C. B. Guiding Nanomaterials to Tumors for Breast Cancer Precision Medicine: from Tumor-targeting Small Molecule Discovery to Targeted Nanodrug Delivery. Npg Asia Mater. 2017, 9, No. e452. (6) Au, L.; Zheng, D.; Zhou, F.; Li, Z.-Y.; Li, X.; Xia, Y. A Quantitative Study on the Photothermal Effect of Immuno Gold Nanocages Targeted to Breast Cancer Cells. ACS Nano 2008, 2, 1645−1652. (7) Huang, X.; Neretina, S.; El-Sayed, M. A. Gold Nanorods: From Synthesis and Properties to Biological and Biomedical Applications. Adv. Mater. 2009, 21, 4880−4910. (8) Zhu, C. H.; Lu, Y.; Chen, J. F.; Yu, S. H. Photothermal Poly(Nisopropylacrylamide)/Fe3O4 Nanocomposite Hydrogel as a Movable Position Heating Source under Remote Control. Small 2014, 10, 2796−2800. (9) Shi, D. L.; Cho, H. S.; Chen, Y.; Xu, H.; Gu, H. C.; Lian, J.; Wang, W.; Liu, G. K.; Huth, C.; Wang, L. M.; Ewing, R. C.; Budko, S.; Pauletti, G. M.; Dong, Z. Y. Fluorescent Polystyrene−Fe3O4 Composite Nanospheres for In Vivo Imaging and Hyperthermia. Adv. Mater. 2009, 21, 2170−2173. (10) Markovic, Z. M.; Harhaji, L. M.; Todorovic, B. M.; Kepic, D. P.; Arsikin, K. M.; Jovanovic, S. P.; Pantovic, A. C.; Dramicanin, M. D.; Trajkovic, V. S. In Vitro Comparison of the Photothermal Anticancer Activity of Graphene Nanoparticles and Carbon Nanotubes. Biomaterials 2011, 32, 1121−1129. (11) Wang, L.; Shi, J. J.; Zhang, H. L.; Li, H. X.; Gao, Y.; Wang, Z. Z.; Wang, H. H.; Li, L. L.; Zhang, C. F.; Chen, C. Q.; et al. Synergistic Anticancer effect of RNAi and Photothermal Therapy Mediated by Functionalized Single-Walled Carbon Nanotubes. Biomaterials 2013, 34, 262−274. (12) Yang, K.; Hu, L. L.; Ma, X. X.; Ye, S. Q.; Cheng, L.; Shi, X. Z.; Li, C. H.; Li, Y. G.; Liu, Z. Multimodal Imaging Guided Photothermal Therapy using Functionalized Graphene Nanosheets Anchored with Magnetic Nanoparticles. Adv. Mater. 2012, 24, 1868−1872. (13) Li, J. L.; Bao, H. C.; Hou, X. L.; Sun, L.; Wang, X. G.; Gu, M. Graphene Oxide Nanoparticles as a Nonbleaching Optical Probe for Two-Photon Luminescence Imaging and Cell Therapy. Angew. Chem., Int. Ed. 2012, 51, 1830−1834. (14) Chen, W. S.; Ouyang, J.; Liu, H.; Chen, M.; Zeng, K.; Sheng, J. P.; Liu, Z. J.; Han, Y. J.; Wang, L. Q.; Li, J.; Deng, L.; Liu, Y. N.; Guo, S. J. Black Phosphorus Nanosheet-Based Drug Delivery System for Synergistic Photodynamic/Photothermal/Chemotherapy of Cancer. Adv. Mater. 2017, 29, No. 1603864. (15) Loo, C.; Lowery, A.; Halas, N. J.; West, J. L.; Drezek, R. ImmunotargetedNanoshells for Integrated Cancer Imaging and Therapy. Nano Lett. 2005, 5, 709−711.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.8b21488. Figure 1: ζ Potential of SF at different pH values; Figure 2: characterization of AuNPs and AuNPs/SF nanofibers; Figure 3: TEM images of AuNPs/SF regulated at different incubation times; Figure 4: TEM images of AuNPs/SF regulated by PEI with varying concentrations and molecular weights; Figure 5: stability assessment of AuNPs/SF nanofibers; Figure 6: UV/vis absorption spectra of SF solution, monodispersed AuNP solution, and AuNPs/SF nanofiber solution; Figure 7: temperature change (ΔT) of AuNPs and AuNPs/SF nanofibers in response to an NIR laser; Figure 8: biocompatibility of AuNPs and AuNPs/SF nanofibers; Figure 9: weight change of mice in different groups during the period of photothermal therapy (PDF)

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REFERENCES

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (C.B.M). *E-mail: [email protected] (M.Y.). ORCID

Chuanbin Mao: 0000-0002-8142-3659 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We acknowledge the support from the National Natural Science Foundation of China (51673168, 81871499, and 31800807), Zhejiang Provincial Natural Science Foundation of China (LZ17C170002 and LZ16E030001), National Postdoctoral Science Foundation of China (2018M632483), F

DOI: 10.1021/acsami.8b21488 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

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ACS Applied Materials & Interfaces

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DOI: 10.1021/acsami.8b21488 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

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DOI: 10.1021/acsami.8b21488 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX