ABSTRACT

In this work, we report an approach to fabricate graphite nanoplatelets/poly(lactic-co-glycolic acid) composite films via drop casting. We tested their frequency-based control of antifouling properties on Escherichia coli bacteria TG1 strain (E. coli TG1), in the safe range of 5 MHz < f < 15 MHz. Scanning electron microscopy (SEM) showed that the average thickness of the composite coatings was 3.5 µm. Raman spectroscopy verified that the structure of the graphene flakes was conserved in the final nanocomposite. Bactericidal assessment was performed by measuring the optical density at 600 nm and the colony forming units (CFU). Our findings showed improved bacteria inhibition when exposed to alternating current frequencies (ACF) at 10 and 15 MHz. At these frequencies, bacteria had also suffered important damage, which was observed by SEM. Culture dynamics after 12 h of the frequency treatments exhibits a significant difference, associated to cell damage observed on bacteria subjected to a specific frequency. The anti-biofilm properties of alternating current frequency (ACV) stimulated GrFs/PLGA thin films underline the importance of the fabrication of novel nanocomposites for biomedical applications where biofilm proliferation is undesirable.

Abbreviations: GrFs: graphite nanoplatelets; PLGA: poly(lactic-co-glycolic acid), E. Coli: Escherichia coli; CFU: colony forming units; PEF: Pulsed Electric Field; OD: optical density; ES: electric stimulation; BC: bacteria control; BVF: variable frequency (BVF) treatments; ACVF: alternating current with variable frequency; EPS: extracellular polymeric substances; DMF: N,N-dimethylformamide; THF: tetrahydrofuran; ACF: alternating current frequencies; SEM: Scanning Electron Microscopy; TEM: Transmission Electron Microscopy.

摘要

在这项工作中，我们报告了一种通过滴铸制备纳米石墨片/聚（乳酸-共-乙醇酸）复合膜的方法。我们在 5 MHz < f的安全范围内测试了他们对大肠杆菌TG1 菌株（大肠杆菌TG1）的防污性能的基于频率的控制< 15 兆赫。扫描电子显微镜 (SEM) 显示复合涂层的平均厚度为 3.5 µm。拉曼光谱证实石墨烯薄片的结构在最终的纳米复合材料中是保守的。通过测量 600 nm 处的光密度和菌落形成单位 (CFU) 进行杀菌评估。我们的研究结果表明，当暴露于 10 和 15 MHz 的交流频率 (ACF) 时，细菌抑制得到改善。在这些频率下，细菌也遭受了重要的损害，SEM 观察到了这一点。频率处理 12 小时后的培养动态表现出显着差异，这与在特定频率下观察到的细菌上观察到的细胞损伤有关。

缩写： GrFs：石墨纳米片；PLGA：聚（乳酸-乙醇酸共聚物），大肠杆菌：大肠杆菌；CFU：菌落形成单位；PEF：脉冲电场；OD：光密度；ES：电刺激；BC：细菌控制；BVF：变频 (BVF) 治疗；ACVF：变频交流电；EPS：胞外聚合物；DMF：N,N-二甲基甲酰胺；THF：四氢呋喃；ACF：交流电频率；SEM：扫描电子显微镜；TEM：透射电子显微镜。