Bacterial biofilms play a key role in the pathogenesis of major oral diseases. Nanoparticles open new paths for drug delivery in complex structures such as biofilms. This study evaluated the antimicrobial effect of zein nanoparticles containing anacardic acid (AA) extracted from cashew shells of Anacardium occidentale on in vitro Streptococcus mutans biofilm formation and mature biofilms. The minimum inhibitory concentration (MIC), minimum bacterial concentration (MBC), and antibiofilm assays were performed. Streptococcus mutans UA159 biofilms were formed on saliva-coated hydroxyapatite disk for 5 days. To evaluate the preventive effect on biofilm formation, before contact with the inoculum, the disks were immersed once for 2 min in (1) hydroethanolic solution; (2) blank zein nanoparticles; (3) zein nanoparticles containing AA; and (4) 0.12% chlorhexidine gluconate. To determine the effect against mature biofilms, the disks containing 5-day preformed biofilms were further treated using the same procedure. The bacterial viability and dry weight were determined for both assays and used to compare the groups using ANOVA followed by Tukey's test (p < 0.05). Both MIC and MBC for AA-loaded zein nanoparticles were 0.36 μg/mL. Groups 3 and 4 were very effective in inhibiting S. mutans biofilm formation, as no colony-forming units were detected. In contrast, for mature biofilms, no difference in bacterial viability (p = 0.28) or dry weight (p = 0.09) was found between the treatments. Therefore, the AA-based nanoformulation presented very high inhibitory and bactericidal activities against planktonic S. mutans, and the results indicate a strong antiplaque effect. However, the formulation showed no antimicrobial effect on the established biofilm.

中文翻译：

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负载漆树酸的玉米醇溶蛋白纳米颗粒负载在变形链球菌生物膜上的抗菌作用

细菌生物膜在主要口腔疾病的发病机制中起着关键作用。纳米粒子为复杂结构（如生物膜）中的药物递送开辟了新途径。本研究评估了含有从漆树腰果壳中提取的漆树酸 (AA) 的玉米醇溶蛋白纳米颗粒对体外变形链球菌生物膜形成和成熟生物膜的抗菌作用。进行了最低抑菌浓度 (MIC)、最低细菌浓度 (MBC) 和抗生物膜测定。变形链球菌 UA159 生物膜在唾液涂层的羟基磷灰石盘上形成 5 天。为了评估对生物膜形成的预防效果，在与接种物接触之前，将圆盘在 (1) 乙醇溶液中浸泡 2 分钟；(2) 空白玉米蛋白纳米颗粒；(3) 含AA的玉米醇溶蛋白纳米粒；和 (4) 0。12% 葡萄糖酸氯己定。为了确定对成熟生物膜的影响，使用相同的程序进一步处理含有 5 天预制生物膜的圆盘。确定两种测定的细菌活力和干重，并使用 ANOVA 和 Tukey 检验 (p < 0.05) 来比较组。载有 AA 的玉米醇溶蛋白纳米颗粒的 MIC 和 MBC 均为 0.36 μg/mL。第 3 组和第 4 组在抑制变形链球菌生物膜形成方面非常有效，因为没有检测到集落形成单位。相比之下，对于成熟的生物膜，处理之间没有发现细菌生存力（p = 0.28）或干重（p = 0.09）的差异。因此，基于 AA 的纳米制剂对浮游变形链球菌表现出非常高的抑制和杀菌活性，结果表明具有很强的抗斑作用。然而，