Variation in biosafety of kaolin nanoclay with its physicochemical aspects

Kaolin, a biocompatible and non-toxic mineral, had attracted increasing interest in biomedicine due to its versatility. While its potential in wound healing, drug delivery, and tissue engineering had been acknowledged, a comprehensive analysis of its physicochemical properties and biological activities remained limited. This study bridged this gap by analyzing kaolin from various sources and exploring their interactions with biological systems. The results demonstrated that kaolin samples from Jiangxi Shangyou (JS), Jiangxi Chongyi (JC), Jiangxi Nankang (JN), Fujian Longyan-Gaobaite (FG), Guangdong Maoming (GM), and Zhejiang Songyang (ZS) met basic biomedical standards, exhibiting good biocompatibility and biosafety. Among them, kaolin from JC, JN, and FG exhibited superior hemostatic properties, while those from JS, JN, FG, and ZS showed notable bacteriostatic activity. Additionally, kaolin from JN, FG, and ZS showed selective cytotoxic effects against cancer, though none demonstrated significant anti-inflammatory effects. The study also sought to find the influence relationship between physicochemical factors with kaolin`s biological activity. Water absorption, crystallinity index ( CI <sub>1</sub> ) values, and particle size might have affected cytotoxicity, with higher water absorption enhancing kaolin`s membrane adsorption and smaller particles having facilitated cell membrane penetration. Kaolin`s crystallinity might have impacted metal leaching, influencing cytotoxicity. For hemolysis, higher specific surface area, CI <sub>1</sub> values, and water absorption corresponded to stronger hemolytic activity. Coagulation performance might have been enhanced by higher kaolinite content, dehydroxylation, and crystallinity, which shortened coagulation times. Surface potential and dehydroxylation might have improved antibacterial activity by promoting kaolin`s adsorption to bacterial surfaces. No significant correlation was found between reactive oxygen species (ROS) intensity and physicochemical properties. This study provided a theoretical foundation for kaolin`s biomedical applications.