School of Science, College of STEM, RMIT University, Melbourne, Victoria 3000, Australia.
School of Science, College of STEM, RMIT University, Melbourne, Victoria 3000, Australia.
J Colloid Interface Sci. 2022 Dec 15;628(Pt B):1049-1060. doi: 10.1016/j.jcis.2022.08.052. Epub 2022 Aug 18.
Titanium and its alloys are commonly used implant materials. Once inserted into the body, the interface of the biomaterials is the most likely site for the development of implant-associated infections. Imparting the titanium substrate with high-aspect-ratio nanostructures, which can be uniformly achieved using hydrothermal etching, enables a mechanical contact-killing (mechanoresponsive) mechanism of bacterial and fungal cells. Interaction between cells and the surface shows cellular inactivation via a physical mechanism meaning that careful engineering of the interface is needed to optimse the technology. This mechanism of action is only effective towards surface adsorbed microbes, thus any cells not directly in contact with the substrate will survive and limit the antimicrobial efficacy of the titanium nanostructures. Therefore, we propose that a dual-action mechanoresponsive and chemical-surface approach must be utilised to improve antimicrobial activity. The addition of antimicrobial silver nanoparticles will provide a secondary, chemical mechanism to escalate the microbial response in tandem with the physical puncture of the cells.
Hydrothermal etching is used as a facile method to impart variant nanostrucutres on the titanium substrate to increase the antimicrobial response. Increasing concentrations (0.25 M, 0.50 M, 1.0 M, 2.0 M) of sodium hydroxide etching solution were used to provide differing degrees of nanostructured morphology on the surface after 3 h of heating at 150 °C. This produced titanium nanospikes, nanoblades, and nanowires, respectively, as a function of etchant concentration. These substrates then provided an interface for the deposition of silver nanoparticles via a reduction pathway. Methicillin-resistant Staphylococcous aureus (MRSA) and Candida auris (C. auris) were used as model bacteria and fungi, respectively, to test the effectiveness of the nanostructured titanium with and without silver nanoparticles, and the bio-interactions at the interface.
The presence of nanostructure increased the bactericidal response of titanium against MRSA from ∼ 10 % on commercially pure titanium to a maximum of ∼ 60 % and increased the fungicidal response from ∼ 10 % to ∼ 70 % in C. auris. Introducing silver nanoparticles increased the microbiocidal response to ∼ 99 % towards both bacteria and fungi. Importantly, this study highlights that nanostructure alone is not sufficient to develop a highly antimicrobial titanium substrate. A dual-action, physical and chemical antimicrobial approach is better suited to produce highly effective antibacterial and antifungal surface technologies.
钛及其合金是常用的植入材料。一旦植入体内，生物材料的界面最有可能成为植入相关感染的发展部位。通过水热蚀刻均匀地赋予钛基体高纵横比纳米结构，可以实现细菌和真菌细胞的机械接触杀伤（机械响应）机制。细胞与表面的相互作用通过物理机制使细胞失活，这意味着需要仔细设计界面以优化该技术。这种作用机制仅对表面吸附的微生物有效，因此，任何未直接与基底接触的细胞都将存活，并限制钛纳米结构的抗菌效果。因此，我们提出必须利用双作用机械响应和化学表面方法来提高抗菌活性。添加抗菌银纳米粒子将提供第二种化学机制，与细胞的物理穿刺协同作用，从而增强微生物的反应。
水热蚀刻用作赋予钛基体变体纳米结构的简便方法，以提高抗菌响应。使用不同浓度（0.25 M、0.50 M、1.0 M、2.0 M）的氢氧化钠蚀刻溶液，在 150°C 加热 3 小时后，在表面上提供不同程度的纳米结构形态。这分别产生了钛纳米尖刺、纳米刀片和纳米线，作为蚀刻剂浓度的函数。然后，这些基底通过还原途径为银纳米粒子的沉积提供了界面。耐甲氧西林金黄色葡萄球菌（MRSA）和耳念珠菌（C. auris）分别用作模型细菌和真菌，以测试具有和不具有银纳米粒子的纳米结构钛的有效性，以及界面处的生物相互作用。
纳米结构的存在使钛对 MRSA 的杀菌反应从商用纯钛的约 10%增加到最大 60%，并使 C. auris 的杀菌反应从约 10%增加到约 70%。引入银纳米粒子使微生物杀灭反应增加到对细菌和真菌的约 99%。重要的是，本研究表明，仅纳米结构不足以开发出高度抗菌的钛基底。物理和化学抗菌的双重作用方法更适合开发高效的抗菌和抗真菌表面技术。
