Green Synthesis, Characterization and Antimicrobial Evaluation of Silver Nanoparticles for an Intracanal Dressing

Abstract Green chemistry has been applied in different areas due to the growing demands for renewable processes and one of them is nanotechnology. The aim of this study was to characterize a formulation containing silver nanoparticles (AgNPs) produced by a green synthesis and to evaluate its antimicrobial activity. The formulation will be used as an intracanal dressing exploiting the AgNPs’ antimicrobial properties, which are crucial to prevent infections and bacterial reinfections that can compromise endodontic treatments. In the green synthesis, silver nitrate was employed as the precursor salt, maltose as a reducing agent, and gelatin as a stabilizing agent. The formulation was prepared mixing 50 % of a liquid containing the AgNPs and 50 % of hydroxyethylcellulose gel at 1.5 % with proper evaluation of the process inherent parameters. Techniques such as molecular absorption spectrometry and dynamic light scattering were used in characterization step. The antimicrobial activity of the AgNPs against Escherichia coli ATCC 25922, Enterococcus faecalis NCTC 775, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and Streptococcus mutans ATCC 25175 was verified according to National Comittee for Clinical Laboratory Standards (NCCLS) by determining minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). The obtained results indicated the formulation containing AgNPs produced by a green synthesis was properly characterized by the selected techniques. Furthermore, the formulation assessment proved that it is suitable for the proposal as well as it has potential to be used as an intracanal dressing since presented antimicrobial activity against all bacterial strains evaluated.

摘要：随着可再生工艺的需求日益增长，绿色化学已被应用于多个领域，其中之一便是纳米技术。本研究旨在对绿色合成法制备的含银纳米颗粒（AgNPs）的制剂进行表征，并评估其抗菌活性。该制剂将被用作根管内封药，利用AgNPs的抗菌特性——这对于预防可损害牙髓治疗效果的感染及细菌再感染至关重要。在绿色合成步骤中，以硝酸银作为前驱体盐，麦芽糖作为还原剂，明胶作为稳定剂。本制剂通过如下方式制备：将50%的含AgNPs溶液与50%的1.5%羟乙基纤维素凝胶混合，并对工艺固有参数进行合理评估。表征环节采用了分子吸收光谱法与动态光散射等技术。本研究参照美国临床实验室标准化委员会（National Committee for Clinical Laboratory Standards, NCCLS）的标准，通过测定最低抑菌浓度（MIC）与最低杀菌浓度（MBC），验证了AgNPs对大肠埃希菌ATCC 25922、粪肠球菌NCTC 775、铜绿假单胞菌ATCC 27853、金黄色葡萄球菌ATCC 25923及变形链球菌ATCC 25175的抗菌活性。所得结果表明，采用所选技术可对绿色合成法制备的含AgNPs制剂进行有效表征。此外，制剂评估结果证实，该制剂符合既定研发目标，且由于其对所有受试菌株均展现出抗菌活性，具备用作根管内封药的潜力。