Elsevier

Colloids and Surfaces B: Biointerfaces

Volume 148, 1 December 2016, Pages 511-517
Colloids and Surfaces B: Biointerfaces

Synthesis and characterization of biocompatible antimicrobial N-halamine-functionalized titanium dioxide core-shell nanoparticles

https://doi.org/10.1016/j.colsurfb.2016.09.030Get rights and content

Highlights

  • Core-shell nanoparticles based N-halamines were synthesized and characterized.

  • The chlorinated nanaoparticles possess excellent antibacterial efficacies against bacteria.

  • The existence of TiO2 significantly improved the UV light stability of the N-halamines.

  • The nanoparticles have good cytocompatibility to mammalian cells.

Abstract

As one of the most powerful biocides, N-halamine based antimicrobial materials have attracted much interest due to their non-toxicity, rechargeability, and rapid inactivation against a broad range of microorganisms. In this study, novel titanium dioxide-ADMH core-shell nanoparticles [TiO2@poly (ADMH-co-MMA) NPs] were prepared via miniemulsion polymerization using 3-allyl-5,5-dimethylhydantoin (ADMH) and methyl methacrylate (MMA) with nano-TiO2. The produced nanoparticles were characterized by FT-IR, TEM, TGA, and XPS. The UV stability of N-halamine nanoparticles has been improved with the addition of titanium dioxide. After chlorination treatment by sodium hypochlorite, biocidal efficacies of the chlorinated nanoparticles against S. aureus (ATCC 6538) and E. coli O157:H7 (ATCC 43895) were determined. The nanoparticles showed excellent antimicrobial properties against bacteria within brief contact time. In addition, in vitro cell cytocompatibility tests showed that the antibacterial nanoparticles had good biocompatibility.

Introduction

Recently, the threat of microorganisms on human health and safety has become a serious public concern. Antimicrobial modification of material surfaces to prevent the growth of harmful microbes has much significance for inhibiting the spread of microorganisms. Accordingly, the research of antimicrobial functional materials and antimicrobial agents is brought to attention. Antibacterial agents, including quaternary ammonium salts [1], [2], chitosan [3], [4], metal ions [5], [6] and N-halamines [7], [8] have been applied for the development of antibacterial materials widely. In particular, N-halamine compounds containing one or more nitrogen-halogen covalent bonds are of great importance due to their properties, such as against a broad spectrum of microorganisms, long-term stability, low toxicity, effective antibacterial ability, and regenerability. The antibacterial mechanism of N-halamine involves the direct transfer of oxidative halogen from N-halamine compounds to the microbial cell membrane, and the halogen has a strong tendency to participate in ionic reactions leading to destruction or inhibition of metabolic processes in microorganisms [9]. After deactivating microorganism, the N-halamine bond (Nsingle bondCl) is transformed to Nsingle bondH which can be recharged with chlorine in a bleaching solution [10].

Antimicrobial performance of N-halamine functionalized materials strongly depends on the contact surface area and contact time with bacteria [11], [12]. It is expected that antibacterial nano-structural materials with large activated surface area can provide enhanced efficacy compared with control samples. Some researches have introduced nanoparticles such as silica, carbon, iron oxide as substrates to gain the activated surfaces [13], [14]. However, some N-halamine compounds are limited in the practical application due to their poor UV stability of Nsingle bondCl bonds and N-halamine structures [15], [16], [17]. Recently, nano-titanium dioxide has attracted much attention and has been reported as a photocatalyst and UV shielding agent due to the advantages of non-toxicity, chemical stability, low-cost, super-hydrophilicity, biocompatibility, and UV-absorbing ability. Additionally, titanium dioxide has been applied on a wide range of application areas such as antibacterial coatings [18], [19], photocatalytic degradation of organic pollutions [20], [21], self-cleaning surface [22], and water and air purifier [23]. Li et al. [24], [25] have reported that titanium dioxide can dramatically improve the UV stability of N-halamine diols and N-halamine siloxanes, respectively. Nano-TiO2 can capture UV light with wavelengths less than 387.5 nm (i.e. UVA) and generate electrons and holes when they reach the oxygen and hydroxyl groups absorbed on the surfaces, which produces reactive oxygen species such as O2 and radical dotOH. These high reactive species can oxidize a variety of organic pollutants and inactivate microorganisms [26]. Herein, we presented regenerable antimicrobial N-halamine/TiO2 core-shell nanoparticles, and compared the UV stability of the prepared nanoparticles with the previous study [15], [16], [17].

In this study, a kind of N-halamine functionalized core-shell titanium dioxide nanoparticles was prepared via miniemulsion polymerization using 3-allyl-5,5-dimethylhydantoin (ADMH) and methyl methacrylate (MMA) as monomers. The procedure employed to synthesize TiO2@poly (ADMH-co-MMA)-Cl nanoparticles is showed in Fig. 1. The prepared nanoparticles were characterized by FT-IR, TEM, TGA and XPS. Antibacterial efficacies of the TiO2@poly (ADMH-co-MMA)-Cl nanoparticles against S. aureus (ATCC 6538) and E. coli O157:H7 (ATCC 43895) were evaluated. The UV stability and regenerability were also investigated after exposing to UV light for variable time. In addition, the biocompatibility of the prepared nanoparticles was assessed by in vitro cell cytocompatibility test.

Section snippets

Materials

Rutile nano-TiO2 was purchased from Hangzhou Wanjing New Material Co., Ltd, Zhejiang. 5,5-Dimethylhydantoin was obtained from Hebei Yaguang Fine Chemical Co., Ltd, Hebei. Allyl bromide was supplied by J&K Scientific Ltd, Shanghai. Methyl mathacrylate (MMA), potassium persulfate (PPS), ethanol, ethyl acetate and sodium hypochlorite were purchased from Sinopharm Chemical Reagent Co., Ltd, Shanghai. All reagents were used as received without further purification.

Characterizations

The structures and morphologies of

Characterization of TiO2@poly (ADMH-co-MMA) NPs

FTIR spectra of pure TiO2 and TiO2@poly (ADMH-co-MMA)-Cl NPs are shown in Fig. 2. The peaks at 2990 and 2948 cm−1 are attributed to the stretching vibration of Csingle bondH bond [28], [29], and the peak at 1145 cm−1 is ascribed to the Csingle bondOsingle bondC stretching vibration. The Csingle bondN stretching vibration appears at 1445 cm−1, and the peak at 1723 cm−1 is caused by the Cdouble bondO stretching vibration [11]. These results indicate that the core-shell nanoparticles exhibit characteristic bands of both MMA and ADMH, which confirms the

Conclusion

N-halamine functionalized titanium dioxide core-shell nanoparticles were successfully prepared via miniemulsion polymerization with titanium dioxide as the core structure and poly(ADMH-co-MMA) as the shell. The prepared nanoparticles were characterized by FT-IR, TEM, TGA and XPS. The as-synthesized nanoparticles with the average size of 144.5 nm have obvious core-shell structure with polymer shell thickness of about 10 nm. TiO2@poly(ADMH-co-MMA)-Cl NPs possess excellent antibacterial ability

Acknowledgements

Authors would like to thank the research funds from the Project for Jiangsu Scientific and Technological Innovation Team, the Science and Technology Department of Jiangsu Province of China (BY2014023-09), and the Scientific Research Foundation for Returned Overseas Chinese Scholars, Ministry of Education, China.

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