Synthesis and characterization of biocompatible antimicrobial N-halamine-functionalized titanium dioxide core-shell nanoparticles
Graphical abstract
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 (NCl) is transformed to NH 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 NCl 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 OH. 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 CH bond [28], [29], and the peak at 1145 cm−1 is ascribed to the COC stretching vibration. The CN stretching vibration appears at 1445 cm−1, and the peak at 1723 cm−1 is caused by the CO 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.
References (40)
- et al.
Ineffectiveness of a quaternary ammonium salt and povidone-iodine for the inactivation of Ascaris suum eggs
Am. J. Infect. Control
(2013) - et al.
Antimicrobial N-halamine modified chitosan films
Carbohydr. Polym.
(2013) - et al.
Silica-silver core-shell particles for antibacterial textile application
Colloids Surf. B: Biointerfaces
(2011) - et al.
Novel N-halamine silanes
Coll. Surf. A
(2009) - et al.
N-halamine/quat siloxane copolymers for use in biocidal coatings
Biomaterials
(2006) - et al.
N-halamine-decorated polystyrene nanoparticles based on 5-allylbarbituric acid: from controllable fabrication to bactericidal evaluation
J. Colloid Interface Sci.
(2014) - et al.
Preparation of magnetically separable N-halamine nanocomposites for the improved antibacterial application
J. Colloid Interface Sci.
(2011) - et al.
Photocatalytic activity and biodegradation of polyhydroxybutyrate films containing titanium dioxide
Polym. Degrad. Stab.
(2006) - et al.
A review on the application of inorganic nano-structured materials in the modification of textiles: focus on anti-microbial properties
Colloids Surf. B: Biointerfaces
(2010) - et al.
Bactericidal evaluation of N-halamine-functionalized silica nanoparticles based on barbituric acid
Colloids Surf. B: Biointerfaces
(2014)