This study aimed to synthesize and characterize chlorhexidine (CHX)-loaded poly-L-glycolic acid (PLGA) nanoparticles and to investigate the in vitro drug release in different pH conditions, antibacterial, cytotoxicity activity, and mechanical properties of CHX-loaded PLGA-modified Transbond XT adhesive at tooth-bracket interface. PLGA nanoparticles with and without CHX were synthesized using emulsion diffusion method and characterized for morphology and chemical structure using transmission electron microscopy and Raman analysis. CHX-loaded PLGA nanoparticles in Transbond XT orthodontic adhesive were prepared using two different concentrations of the nanoparticles (2.5 and 5 wt%) and characterized for degree of conversion (DC) using DC, antimicrobial MTT assay, and cytotoxicity testing. Bonded specimens were tested for shear bond strength (SBS) and adhesive remnant index (ARI) at the tooth-bracket interface. The synthesized PLGA nanoparticles averaged between 60 and 80 nm in size. After loading CHX inside PLGA nanoparticles, the morphology of the PLGA nanoparticles was changed considerably into irregular shaped structures. Bracket samples treated with 5 wt% CHX-loaded PLGA-modified adhesive demonstrated the least mean DC scores. A 5 wt% CHX-loaded PLGA-modified adhesive specimens showed more profound antibacterial activity against Streptococcus mutans. The least mean SBS values were exhibited by 5 wt% CHX-loaded PLGA-modified adhesive samples, while a statistically significant difference was observed in the mean ARI values among all study groups at all-time points (p = 0.018). A pH-sensitive CHX release response was observed when loaded in PLGA nanoparticles. The formulated drug-loaded nanocarrier exhibited remarkable physicochemical, spectral, and biological features.

中文翻译：

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用于稳定粘合剂正畸界面的 pH 接受性氯己定负载聚-L-乙醇酸平台递送方法

本研究旨在合成和表征负载氯己定 (CHX) 的聚-L-乙醇酸 (PLGA) 纳米颗粒，并在体外研究不同 pH 条件下的药物释放、抗菌、细胞毒性活性和载 CHX 的 PLGA 改性 Transbond XT 粘合剂在牙托界面的机械性能。使用乳液扩散法合成含有和不含 CHX 的 PLGA 纳米粒子，并使用透射电子显微镜和拉曼分析表征形态和化学结构。Transbond XT 正畸粘合剂中负载 CHX 的 PLGA 纳米颗粒使用两种不同浓度的纳米颗粒（2.5 和 5 重量％）制备，并使用 DC、抗菌 MTT 测定和细胞毒性测试表征转化程度 (DC)。在齿托界面处测试粘合试样的剪切粘合强度 (SBS) 和粘合剂残留指数 (ARI)。合成的 PLGA 纳米粒子的平均尺寸在 60 到 80 nm 之间。在 PLGA 纳米粒子中加载 CHX 后，PLGA 纳米粒子的形态显着改变为不规则形状的结构。用 5 wt% CHX 负载的 PLGA 改性粘合剂处理的支架样品表现出最低的平均 DC 分数。负载 5 wt% CHX 的 PLGA 改性粘合剂样品显示出更强大的抗菌活性变形链球菌。负载 5 wt% CHX 的 PLGA 改性粘合剂样品表现出最低的平均 SBS 值，而在所有时间点的所有研究组的平均 ARI 值中观察到统计学显着差异（p  = 0.018）。当加载到 PLGA 纳米颗粒中时，观察到 pH 敏感的 CHX 释放响应。配制的载药纳米载体表现出显着的物理化学、光谱和生物学特征。