Research Article www.acsami.org
Smart Antibacterial Surface Made by Photopolymerization Haitao Yang,† Guofeng Li,‡ Jeffrey W. Stansbury,§ Xiaoqun Zhu,† Xing Wang,*,‡ and Jun Nie*,† †
State Key Laboratory of Chemical Resource Engineering & Beijing Laboratory of Biomedical Materials and ‡College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, P. R. China § School of Dental Medicine, University of Colorado, Denver, Colorado 80045, United States
ABSTRACT: On the basis of the use of photopolymerization technology, a facile and reliable method for in situ preparation of silver nanoparticles (AgNPs) within PNIPAAm functional surfaces is presented as a means to achieve nonfouling, antibacterial films. The surface properties were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), water contact angle, and thermogravimetric analysis (TGA). The antibacterial and release properties of the surfaces were tested against E. coli: at 37 °C (above the LCST of PNIPAAm), the functional films facilitated the attachment of bacteria, which were then killed by the AgNPs. Changing temperature to 4 °C (below the LCST), swollen PNIPAAm chains led the release of dead bacteria. The results showed that AgNPs/PNIPAAm hybrid surfaces offer a “smart” antibacterial capability in response to the change of environmental temperature. KEYWORDS: photopolymerization, antimicrobial, poly(N-isopropylacrylamide), silver nanoparticles, Surface modification
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barrier and finally, shed the dead bacteria in order to maintain long-term biocidal activity. Smart or stimuli-responsive materials show rapid and reversible changes in their physicochemical properties in response to small changes in environmental conditions.15 Poly(N-isopropylacrylamide) (PNIPAAm) is one of the most studied and widely used environmentally sensitive polymers for controlling the wettability of surfaces.16 The temperaturetriggered change in hydrophilic character of PNIPAAmmodified surfaces results in a change in the adhesive interface that leads to the detachment of bacteria from such surfaces. Moreover, these materials can release not only newly attached bacteria but also fully developed biofilms.17−19 Yu et al. developed a hybrid surface which can bind, kill, and release bacteria in a controllable manner by using interferometric lithography (IL)- activators regenerated by electron transfer (AGET)- atom transfer radical polymerization (ATRP) technology to integrate lysozyme into thermally responsive nanopatterned PNIPAAm surfaces.20 This is a remarkable and significant work for solving such problems about biocontamination or biofouling. However, the production of this multifunctional material requires complex equipment and processes to produce nanopatterned PNIPAAm on surfaces.
INTRODUCTION The adhesion of bacteria to material surfaces (ensuing formation of biofilms) and the associated risk of biofouling is considered to contribute to be a variety of threats, including but not limited to public health, water purification, medical implants, textiles, biosensors, as well as in food packaging and food storage.1−6 Thus, the development of methods to prevent biocontamination on material surfaces have attracted much public attention over the past few decades. There are two different general approaches that have been adopted to avoid biofouling. The first is known as fouling-resistant coatings that resist the adhesion of biocontaminants, such as tethered poly(ethylene glycol) (PEG), zwitterions, glycopolymers and chiral borneol polymer.7−10 The other effective method involves incorporation of biocidal agents on material surfaces, such as antibiotics, nanoparticles, polycations, enzymes, and antimicrobial peptides.11−14 The surfaces with biocides can prevent biofilm formation by limiting microbial adhesion or killing microorganisms as they contact with the solid surfaces. Unfortunately, both of strategies are practical to prevent the formation of viable biofilms during only a short period. Especially for the latter strategy, the remaining dead bacteria killed by biocides still contaminate these surfaces and not only degrade continued biocidal activity of the surfaces but also provide nutrients for other colonizers. Therefore, an ideal antibacterial surface should prevent initial bacterial attachment, kill all bacteria that manage to overcome this antiadhesion © XXXX American Chemical Society
Received: July 28, 2016 Accepted: October 3, 2016
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DOI: 10.1021/acsami.6b09343 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces Scheme 1. In Situ Synthesis of Silver Nanocomposite
Scheme 2. Strategy for Synthesis of Smart Polymer Surfaces by Photopolymerization to Provide for Bacterial Attachment and Detachment in Response to the Change in Environmental Temperature
three times from hexane and then dried under vacuum before use. Silver nitrate (AgNO3; AR), sodium chloride, sulfuric acid (98 wt %), hydrogen peroxide solution (30 wt %), ethanol, toluene and acetone were purchased from Beijing Chemical Works (China). 3-Methacryloxypropyltrimethoxysilane (MPS) was purchased from J&K Scientific Ltd. (Beijing, China). Trimethylolpropane triacrylate (TMPTA) was donated by Sartomer company. Beef extract, Tryptone soya agar and Peptone were purchased from Beijing Land Bridge Technology Co., Ltd. (China). All other reagents were used as received without further purification. Glass slides were purchased from Sail Brand (1 mm-1.2 mm thick; CAT. No. 701; China). Instruments and Measurements. UV(ultraviolet)-Light emitting diodes(LED) was purchased from Phoseon Technology (Firefly, Wavelength: 365 nm, USA). The irradiation intensity was measured by a UV-A Radiometer (Photoelectric Instrument Factory of Beijing Normal University). The chemical composition of the original and modified surfaces was determined by using an ESCALAB 250 X-ray Photo-Electron Spectrometer (XPS, ThermoFisher Scientific, USA). Fluorescence images of the bacteria attached to the surfaces were obtained by fluorescence microscope (IX71, Olympus, Japan). The fluorescent images were acquired on a confocal microscope (SP8, Leica, German). Contact angle measurements were performed on a Contact Angle System (OCA20, Data-physics instruments GmbH, German). The scanning electron microscopy (SEM) images were recorded using an Supra55 (ZEISS, German), and transmission electron microscopy (TEM) images were obtained from a JEM-3010 (JEOL, Japan). Thermogravimetric analyses (TGA) were carried out using a Q500 thermogravimetric analyzer (TA Instruments, USA). Glass Silanization Procedure (MPS-Glass). Glass slides were cut into pieces of about 1 × 1 cm, cleaned by sonication in ethanol, acetone, and ultrapure water for 5 min. The substrates were washed with ultrapure water, dried by nitrogen, then immersed into a freshly prepared Piranha solution (H2SO4/H2O2 = 7/3) for 2 h (Caution: Piranha solution is extremely caustic). The glass was rinsed with copious amounts of ultrapure water, dried in a stream of nitrogen and then immediately placed in a freshly prepared solution of 3-methacryloxypropyltrimethoxysilane (MPS) in anhydrous toluene (0.1 vol %).
Photopolymerization has been the basis of numerous conventional applications in coatings, adhesives, inks, printing plates as well as surface modification.21 For example, Yusuf Yagci et al. utilized photopolymerization method, in situ preparation of oil-based polymer-silver nanocomposites(NPs). Silver NPs were formed by the electron transfer reaction of photoinitiator during the process of polymerization.22 The reactions proceed rapidly at ambient conditions and are able to exhibit both temporal and spatial control.23 Recently, our group reported a facile method for modifying glass surfaces by a photopolymerization technique.24 In that work, PNIPAAm was chemically fixed to the surface of glass by covalent bonds, which enhanced bonding between the polymer and the glass substrate. Silver ions and silver nanoparticles (AgNPs) have been recognized as excellent antimicrobial agents because of their effective biocidal ability and biocompatibility to human cells.25,26 Thus, using pure AgNPs or AgNP/polymer hybrid materials as antibacterial agents has been reported numerous times, which indicates that these materials have a good capability for antibacterial activity.27,28 Here, we combine AgNPs with PNIPAAm on glass surfaces for “smart” antibacterial films by using a one-step photopolymerization method involving a photoinitiator that absorbs UV light (365 nm) to produce free radicals. On the one hand, free radicals can induce polymerization of NIPAAm, whereas on the other hand, the free radicals can also reduce silver ions to silver metal that then coalesce to form silver nanoparticles22,29−32 (Scheme.1). With this, we present a facile and reliable strategy to design surfaces that can attach, kill, and release bacteria in response to the change in environmental temperature (Scheme. 2).
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EXPERIMENTAL SECTION
Materials. N-Isopropylacrylamide (NIPAAm) and 2,2-dimethoxy2-phenylacetophenone (DMPA) were purchased from Tokyo Chemical Industry Co., Ltd. NIPAAm monomer was recrystallized B
DOI: 10.1021/acsami.6b09343 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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ACS Applied Materials & Interfaces Table 1. Compositions of Starting Solutions sample
molar ratio (nAg:nNIPAAm)
NIPAAm (mol L−1)
DMPA (mol L−1)
TMPTA (mol L−1)
silver nitrate (mol L−1)
solvent (× 10−3L)a
PNIPAAm AgNPs/PNIPAAm1 AgNPs/PNIPAAm2 AgNPs/PNIPAAm3 AgNPs/PNIPAAm4 AgNPs/PNIPAAm5
0:1 0.007:1 0.033:1 0.066:1 0.133:1 0.199:1
5.89 5.89 5.89 5.89 5.89 5.89
0.05 0.05 0.05 0.05 0.05 0.05
0.02 0.02 0.02 0.02 0.02 0.02
0 0.04 0.20 0.39 0.78 1.18
1 1 1 1 1 1
a Note: Solvent, H2O:ethanol, 1:1 (v/v). The solution was degassed with nitrogen for 30 min before use. Subsequent identification of these AgNPs/ PNIPAAm formulations uses the 1−5 subscript designations.
Figure 1. (A) TEM image and (B) size-distribution histogram of prepared AgNPs/PNIPAAm3. (C) average size histograms of AgNPs/ PNIPAAm1−5.
Figure 2. (A) XPS survey spectra of the surface: glass, MPS-glass, PNIPAAm-glass, and AgNPs/PNIPAAm-glass. (B) High-resolution XPS spectra of C 1s. (C) High-resolution XPS spectra of O 1s. light at a radiation intensity of 40 mW/cm2 for 20 min. The PET film was then peeled off and the underlying, surface-bound polymer was washed thoroughly with ethanol to remove any unreacted monomer as well as ungrafted polymer. These polymer-modified films on the glass slides were then dried by nitrogen stream and stored in a capped centrifuge tube for later use.
After 24 h, the substrates were again washed with ethanol and ultrapure water followed by drying under a nitrogen flow. Preparation of Sliver Nanoparticles Embedded in Polymer films on Glass Substrates. Three drops of the solutions described in Table 1 were placed onto the MPS-modified glass with a 1 mL syringe. The surface of the liquid was covered by a PET film to avoid oxygen inhibition, as shown in Scheme 2. Each sample was irradiated by UV C
DOI: 10.1021/acsami.6b09343 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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ACS Applied Materials & Interfaces Antibacterial Experiments. The antibacterial properties of functional substrates were investigated by using a “zone of inhibition” test according to a previously reported procedure.33,34 Escherichia coli (E. coli) was incubated in fresh Luria−Bertani (LB) medium (beef extract 0.3 g, peptone 1 g, and NaCl 0.5 g were dissolved in 100 mL of deionized water, pH 7) at 37 °C with a shaking incubator overnight (speed, 255 rpm). The bacterial suspension was then diluted to 1 × 106 colony forming units (CFU/mL) by sterile normal saline for later usage. About 100 μL of E. coli suspension was dispersed uniformly on the surface of LB agar plates (LB broth with 2.0% agar). The samples (about 1 × 1 cm, sterilized under ultraviolet light) were gently placed on the top of the plate and incubated at 37 °C. After 24 h of incubation, bacterial colony growth was observed, and the zone of inhibition was measured to evaluate the antibacterial performance. For the bacterial release experiment, 10 μL of E. coli suspension was added to the surface of the samples and incubated at 37 °C for 1 h. After rinsing with 30 mL of normal saline, the samples were immersed in normal saline and shaken at 4 °C for 0.5 h (speed, 100 rpm). The samples were then rinsed again with 30 mL of normal saline (4 °C). The E. coli on the surface of the samples was immobilized with 2.5% glutaraldehyde at 4 °C for 2 h. Finally, the adherent bacterium was stained by propidium lodide (PI) solution and observed with a fluorescence microscopy.
only promotes the polymerization of NIPAAm monomer, but also serves as the reducing agent for the reduction of silver nitrate. The morphologies of the AgNPs in PNIPAAm were investigated by TEM imaging. As shown in Figure 1A, the AgNPs, which are embedded in the PNIPAAm film, are spherical and evenly distributed. A statistical analysis, which was conducted by measuring approximately 500 silver nanoparticles in the TEM images, reveals that the size distribution of the AgNPs is relatively narrow (ranges from 1 to 10 nm) and their average diameter is approximately 5.3 nm (Figure 1B). The AgNPs prepared with different concentrations of silver nitrate also show a uniformly spherical shape and similar size. These phenomena indicate that the AgNPs/PNIPAAm composite was synthesized successfully by this efficient and convenient onestep photopolymerization method. The AgNPs were uniform and size-controllable by the reduction associated with the photoinitiator. 1.2. X-ray Photoelectron Spectroscopy (XPS). X-ray photoelectron spectroscopy (XPS) was used to investigate the bonding and chemical environments of this functional surface coating. As shown in Figure 2A, the characteristic signals of elements (silicon, carbon and oxygen) are observed at the surfaces of the Glass and MPS-Glass samples. When PNIPAM is grafted on the surface of glass, the signal of nitrogen emerges and the signal of carbon is enhanced, while the signals of oxygen and silicon weaken. Compared with PNIPAAm-glass, AgNPs/PNIPAAm-glass is the only one that contains silver element (Figure 2A). To investigate the interactions between polymers and polymer-stabilized metal nanoparticles, we analyzed the composition of the carbon element and the oxygen element in AgNPs/PNIPAAm-glass. Figure 2B shows the highresolution XPS spectrum in the C 1s region of AgNPs/ PNIPAAm-glass. The C 1s region is composed of three bands located at 284.7 ± 0.3, 285.9 ± 0.3, and 287.6 ± 0.3 eV. These signals correspond respectively to the carbon atom in C−C and C−H bond, carbon atom in C−N of PNIPAM chains and carbon atom in N−CO.23 For the O 1s high-resolution XPS spectra, as shown in Figure 2C, the O 1s photoemission spectra were shifted to a higher energy and deconvoluted into two peaks. The lower peak at 531 ± 0.3 eV was attributed to the CO, which was not coordinated to the silver nanoparticles. The higher one at 531.6 ± 0.3 eV was attributed to the interaction between carbonyl oxygen atoms and silver nanoparticles35 (the confidence interval of the binding energies is 0.3 eV). Atomic percent of elements of these samples is exhibited in Table 2. Ranging from sample glass, MPS-Glass to PNIPAAm, the atomic percent of carbon and nitrogen increase, while the atomic percent of oxygen decrease. These results indicate that NIPAAm was successfully grafted on the surface of glass. Because PNIPAAm covered the underlying glass, the atomic percent of silicon decreases. For the samples of AgNPs/ PNIPAAm, the amount of AgNPs (which corresponds to the atomic percent of silver, Ag 3d5) increases with increasing concentrations of silver nitrate, whereas the atomic percent of carbon, oxygen and nitrogen remain the same (Table 2 AgNPs/ PNIPAAm1−5), demonstrating that the addition of silver nitrate does not affect the photopolymerization process of NIPAAm and the photoinitiator is able to reduce silver nitrate. These data indicate that this one-step method of photopolymerization is a facile, reliable, and effective method for in situ preparation of AgNPs/PNIPAAm composites.
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RESULTS AND DISCUSSION 1. Characterization of AgNPs/PNIPAAm Glass Surfaces. 1.1. Morphological Analysis (TEM). The AgNPs/ Table 2. XPS Survey Spectra of Samplesa
a
Data are atomic percent of each element (ND, not detected).
Figure 3. Water contact angles of surfaces at different temperature. Data are mean ± standard deviation (n = 8).
PNIPAAm composites were in situ fabricated through a onestep method of photopolymerization. The photoinitiator not D
DOI: 10.1021/acsami.6b09343 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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ACS Applied Materials & Interfaces
Figure 4. (A)Thermogravimetric curves and (B) derivative thermogravimetric curves of PNIPAAm and AgNPs/PNIPAAm1−5.
Figure 5. Optical photographs of bacteriostatic zone of (a) MPS-Glass, (b) PNIPAAm, and (c−g) AgNPs/PNIPAAm1−5 after 24 h. E. coli grew in the culture plates. (a′−g′) Enlarged images of a−g after 120 h.
2. Thermoresponse of AgNPs/PNIPAAm Glass Surfaces. PNIPAAm is a temperature-responsive intelligent material that undergoes a reversible phase change from hydrophilic to hydrophobic at its lower critical solution temperature (LCST) transition.36−39 To prove that the AgNPs/PNIPAAm films possess this reversible performance, we performed water contact angle (WCA) testing to detect the surface wettability change of the AgNPs/PNIPAAm-glass as a function of temperature. As shown in Figure 3, WCA of the MPS-Glass surfaces barely changes, whereas PNIPAAm surfaces exhibited
temperature-responsiveness, and WCA changes from 82° at 37 °C to 56° at 4 °C. For AgNPs/PNIPAAm-Glass1, its WCA is consistent with that of PNIPAAm, which indicates that the AgNPs/PNIPAAm retains the property of temperatureresponsiveness. 3. Thermogravimetric Analyses. Thermal properties of the samples were investigated by thermogravimetric analysis (TGA), which was conducted under a nitrogen atmosphere (from 30 to 600 °C, 20 °C/min). The thermograms of pure PNIPAAm and AgNPs/PNIPAAm are shown in Figure 4. E
DOI: 10.1021/acsami.6b09343 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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(n = 8). The results indicated that AgNPs/PNIPAAm-glass surfaces exhibited performance as an antibacterial agent compared to glass or PNIPAAm-glass, the sizes of the zone of inhibition increased with the increase amount of Ag in the PNIPAAm. Compared with earlier reports,41 the zone of inhibition was not as big as classic AgNPs antibacterial agent. The most likely reason was that the AgNPs were embedded into PNIPAAm cross-link network and interacted with macromolecular chains, so AgNPs/PNIPAAm could only release silver ions very slowly into the environment as a controlled-release antibacterial agent. 4.2. Bacterial Attachment and Detachment. Previous studies reveal that bacterial adhesion on materials poses the risk of biocontaimination, even though the bacteria may have been killed.1−3 Therefore, we investigated the bacterial release capability of the AgNPs/PNIPAAm-Glass, as shown in Figure 6. After agitation with cold saline, there are still high amounts of bacteria attached on the control surfaces, whereas a significant number of bacterial are removed from the PNIPAAm and AgNPs/PNIPAAm surfaces, suggesting that PNIPAAm has good performance in terms of bacterial release. Interestingly, no matter before or after desorption, the amounts of bacterial cell attachment on the AgNPs/PNIPAAm surfaces are much lower than that on PNIPAAm surfaces (Figure 6B, C). The AgNPs clearly contribute to reduced bacterial adhesion. This result can be attributed to the following factors. First, E. coli cells are able to sense the AgNPs/PNIPAAm surface and avoid adhering on it, which is harmful for them. Second, nanostructured substrates can affect the metabolism of E. coli. The interaction between E. coli and the substrate becomes weak such that E. coli can easily escape from the substrate.42−44 Thus, these phenomena likely contribute to the strong fouling-resistant and self-cleaning capability of the AgNPs/PNIPAAm films.
Figure 6. Confocal microscope fluorescence graphs of E. coli on (A) glass, (B) PNIPAAm-glass, (C) AgNPs/PNIPAAm-Glass. (A′−C′) Confocal microscope fluorescence graphs of E. coli after immersion in normal saline and shaking at 4 °C for 0.5 h (speed, 100 rpm).
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CONCLUSION In this work, AgNPs/PNIPAAm functional surfaces with strong fouling-resistant and self-cleaning capability were in situ prepared on glass by a one-step photopolymerization method. The polymerization reaction and the metal reduction reaction operated simultaneously with the catalysis of the photoinitiator. The obtained AgNPs had narrow size distribution (∼5 nm) and uniformly spherical shape, while the PNIPAAm inherited the property of temperature-responsiveness. In the synergy of AgNPs and PNIPAAm, the AgNPs/PNIPAAm functional surfaces achieved smart antibacterial activity that killed a large number of E. coli at 37 °C and released them at 4 °C. With the increase in the amount of Ag, AgNPs/PNIPAAm functional surfaces demonstrated progressively enhanced fouling-resistant and self-clean capability. Therefore, this study exhibited a facile and reliable strategy to design well-defined functional surfaces that could kill and release bacteria in a controllable manner. According to these results, it is anticipated that this functional surfaces can be used in various applications such as biofilms, biofouling or the “smart” coating of biomedical materials.
There is an initial weight loss at temperatures below 100 °C due to the loss of moisture and volatilization/decomposition of various chemicals including any residual solvent and unreacted monomer. The weight loss of the AgNPs/PNIPAAm samples at around 200 °C is probably the result of the decomposition of the thermally labile Ag2O, which breaks into Ag and O2 (at temperatures greater than 200 °C).40 The PNIPAAm decomposes after 330 °C and remains as carbon black at 600 °C (accounts for 2.4%, w/w). Compared with the PNIPAAm, Ag in the AgNPs/PNIPAAm is thermally stable at 600 °C. Thus, the content of Ag in the AgNPs/PNIPAAm can be calculated with this method. Overall, the test of TGA indicated that the AgNPs/PNIPAAm were thermally stable below 200 °C. 4. Antibacterial Section. 4.1. Antibacterial Activity. Aforementioned studies demonstrated that the composite of AgNPs/PNIPAAm was successfully grafted on the surface of glass and the PNIPAAm maintained its temperature-responsive behavior. The question then considered was whether the AgNPs in these composite films retained their antibacterial function. Thus, the antibacterial activity of the AgNPs/ PNIPAAm was investigated by using the method of “zone of inhibition”, which was described in detail of the experimental section. As shown in Figure 5, an inhibition in growth of E. coli was observed. The average diameter of the zone of inhibition for the sample of MPS-glass, PNIPAAm-Glass and AgNPs/ PNIPAAm1−5 is 0, 0, 5.7, 13.1, 20.2, 21.1, 24.2 mm, respectively
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. Phone: +86 01064421310 (J.N.). *E-mail:
[email protected] (X.W.). Author Contributions
H.Y. and G.L. contributed equally to this work. F
DOI: 10.1021/acsami.6b09343 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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ACS Applied Materials & Interfaces Notes
Binding Motifs Connected by Linkers To Inhibit Biofilm Formation. ACS Appl. Mater. Interfaces 2016, 8 (8), 5124−5136. (15) Liu, Z.; Wang, W.; Xie, R.; Ju, X.-J.; Chu, L.-Y. StimuliResponsive Smart Gating Membranes. Chem. Soc. Rev. 2016, 45 (3), 460−475. (16) Banerjee, I.; Pangule, R. C.; Kane, R. S. Antifouling Coatings: Recent Developments in the Design of Surfaces that Prevent Fouling by Proteins, Bacteria, and Marine Organisms. Adv. Mater. 2011, 23 (6), 690−718. (17) Shivapooja, P.; Ista, L. K.; Canavan, H. E.; Lopez, G. P. ARGET−ATRP Synthesis and Characterization of PNIPAAm Brushes for Quantitative Cell Detachment Studies. Biointerphases 2012, 7 (1), 32. (18) Ista, L. K.; Mendez, S.; Lopez, G. P. Attachment and Detachment of Bacteria on Surfaces with Tunable and Switchable Wettability. Biofouling 2010, 26 (1), 111−118. (19) Ista, L. K.; Mendez, S.; Pérez-Luna, V. H.; López, G. P. Synthesis of Poly(N-isopropylacrylamide) on Initiator-Modified SelfAssembled Monolayers. Langmuir 2001, 17 (9), 2552−2555. (20) Yu, Q.; Ista, L. K.; Lopez, G. P. Nanopatterned Antimicrobial Enzymatic Surfaces Combining Biocidal and Fouling Release Properties. Nanoscale 2014, 6 (9), 4750−7. (21) Yagci, Y.; Jockusch, S.; Turro, N. J. Photoinitiated Polymerization: Advances, Challenges, and Opportunities. Macromolecules 2010, 43, 6245. (22) Eksik, O.; Tasdelen, M. A.; Erciyes, A. T.; Yagci, Y. In Situ Synthesis of Oil-Based Polymer/Silver Nanocomposites by Photoinduced Electron Transfer and Free Radical Polymerization Processes. Compos. Interfaces 2012, 17, 357. (23) Bowman, C. N.; Kloxin, C. J. Toward an Enhanced Understanding and Implementation of Photopolymerization Reactions. AIChE J. 2008, 54 (11), 2775−2795. (24) Dong, Y.; Zhu, X.; Shi, F.; Nie, J. Surface Photo-Anchored PNIPAM Crosslinked Membrane on Glass Substrate by Covalent Bonds. Appl. Surf. Sci. 2014, 307, 7−12. (25) Chernousova, S.; Epple, M. Silver as Antibacterial Agent: Ion, Nanoparticle, and Metal. Angew. Chem., Int. Ed. 2013, 52 (6), 1636− 1653. (26) Kim, J. S.; Kuk, E.; Yu, K. N.; Park, S. J.; Lee, H. J.; Kim, S. H.; Park, Y. H.; Hwang, C.; Kim, Y.; Lee, Y.; et al. Antimicrobial Effects of Silver Nanoparticles. Nanomedicine 2007, 3 (1), 95−101. (27) Yan, J.; Abdelgawad, A. M.; El-Naggar, M. E.; Rojas, O. J. Antibacterial Activity of Silver Nanoparticles Synthesized In-situ by Solution Spraying onto Cellulose. Carbohydr. Polym. 2016, 147, 500− 508. (28) Meng, M.; He, H.; Xiao, J.; Zhao, P.; Xie, J.; Lu, Z. Controllable in Situ Synthesis of Silver Nanoparticles on Multilayered Film-Coated Silk Fibers for Antibacterial Application. J. Colloid Interface Sci. 2016, 461, 369−375. (29) Sangermano, M.; Yagci, Y.; Rizza, G. In Situ Synthesis of SilverEpoxy Nanocomposites by Photoinduced Electron Transfer and Cationic Polymerization Processes. Macromolecules 2007, 40 (25), 8827−8829. (30) Fischer, H.; Baer, R.; Hany, R.; Verhoolen, I.; Walbiner, M. 2,2Dimethoxy-2-phenylacetophenone: Photochemistry and Free Radical Photofragmentation. J. Chem. Soc., Perkin Trans. 2 1990, 5, 787−798. (31) Baumann, H.; Timpe, H. J.; Zubarev, V. E.; Fok, N. V.; Mel’nikov, M. Y. Lichtinitiierte Polymer- und PolymerisationsReaktionen XXII: Untersuchungen zur Photolyse von PhotoInitiatoren mit Benzyliden-tert.-butylamin-n-oxid als Spin-trap. J. Photochem. 1985, 30 (4), 487−500. (32) Timpe, H. J. Photoinduced Electron Transfer Polymerization. Top. Curr. Chem. 1990, 156, 167−197. (33) Kong, H.; Jang, J. Antibacterial Properties of Novel Poly(methyl methacrylate) Nanofiber Containing Silver Nanoparticles. Langmuir 2008, 24 (5), 2051−2056. (34) Luo, L.; Li, G.; Luan, D.; Yuan, Q.; Wei, Y.; Wang, X. Antibacterial Adhesion of Borneol-Based Polymer via Surface Chiral
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This study was financially supported by the National Natural Science Foundation of China (51373015, 51573011, 51603007, 21574008) and Changzhou Sci&Tech Program (BY2014051). The authors also appreciate the support of the Beijing Laboratory of Biomedical Materials. The authors appreciate Dr. Jiaxian Liu (State Key Laboratory of Polymer Physics and Chemistry Institute of Chemistry, Chinese Academy of Sciences, Beijing, China) for help on a series of tests.
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DOI: 10.1021/acsami.6b09343 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
