Bacterial biofilms are microbial communities in which bacterial cells in sessile state are mechanically and chemically protected against foreign agents, thus enhancing antibiotic resistance. The delivery of active compounds to the inside of biofilms is often hindered due to the existence of the biofilm extracellular polymeric substances (EPS) and to the poor solubility of drugs and antibiotics. A possible strategy to overcome the EPS barrier is the incorporation of antimicrobial agents into a nanocarrier, able to penetrate the matrix and deliver the active substance to the cells. Here, we report the synthesis of antimicrobial curcumin-conjugated silica nanoparticles (curc-NPs) as a possibility for dealing with these issues. Curcumin is a known antimicrobial agent and to overcome its low solubility in water it was grafted onto the surface of silica nanoparticles, the latter functioning as nanocarrier for curcumin into the biofilm. Curc-NPs were able to impede the formation of model P. putida biofilms up to 50% and disrupt mature biofilms up to 54% at 2.5 mg mL⁻¹. Cell viability of sessile cells in both cases was also considerably affected, which is not observed for curcumin delivered as a free compound at the same concentration. Furthermore, proteomics of extracted EPS matrix of biofilms grown in the presence of free curcumin and curc-NPs revealed differences in the expression of key proteins related to cell detoxification and energy production. Therefore, curc-NPs are presented here as an alternative for curcumin delivery that can be exploited not only to other bacterial strains but also to further biological applications.

中文翻译：

---

通过二氧化硅表面改性提高姜黄素的溶解度和抗生物膜活性

细菌生物膜是微生物群落，其中处于固着状态的细菌细胞受到机械和化学保护而免受外来物质的侵害，从而增强了抗生素耐药性。由于生物膜胞外聚合物 (EPS) 的存在以及药物和抗生素的溶解度差，活性化合物向生物膜内部的传递常常受到阻碍。克服 EPS 屏障的一种可能策略是将抗菌剂掺入纳米载体中，能够穿透基质并将活性物质输送到细胞中。在这里，我们报告了抗菌姜黄素共轭二氧化硅纳米粒子 (curc-NPs) 的合成，作为解决这些问题的一种可能性。姜黄素是一种已知的抗菌剂，为了克服其在水中的低溶解度，它被接枝到二氧化硅纳米粒子的表面，后者作为姜黄素进入生物膜的纳米载体。Curc-NPs能够阻碍模型的形成^{在 2.5 mg mL -1}下，恶臭假单胞菌生物膜高达 50%，成熟生物膜破坏高达 54% 。在这两种情况下，固着细胞的细胞活力也受到很大影响，这对于以相同浓度作为游离化合物递送的姜黄素没有观察到。此外，在游离姜黄素和 curc-NPs 存在下生长的生物膜提取的 EPS 基质的蛋白质组学揭示了与细胞解毒和能量产生相关的关键蛋白质表达的差异。因此，curc-NPs 在这里作为姜黄素递送的替代品提出，不仅可以用于其他细菌菌株，还可以用于进一步的生物学应用。