Comprehensive evaluation of the nephrotoxicity of carbon quantum dots: Effects of the surface charge

Carbon quantum dots (CQDs) are garnering attention for their broad applications. This study offers a detailed evaluation of the biomedical safety and health risks of carbon quantum dots (CQDs) with different surface modifications, addressing a key gap in their safe application. It focuses on three CQD types: diammonium citrate-based (CQDs-A), spermidine trihydrochloride-based (CQDs-S), and a combination (CQDs-A/S), analyzing their physicochemical properties, cytotoxicity, oxidative stress, inflammatory responses, and nephrotoxicity. While all CQDs were under 10 nm, their biological impacts varied. Positively charged CQDs-S and CQDs-A/S showed significant cytotoxicity in HEK293 cells, inducing oxidative stress but not activating NLRP3 inflammasome, indicating a limited inflammatory response. Renal integrity remained unaffected, with stable zonula occludens 2 expression and unaltered renal markers. In vivo studies in BALB/c mice further supported the safety of CQDs, showing no organ damage or kidney pathology at high doses. The findings underscore the potential for safe biomedical use of CQDs, particularly when their retention time is minimized. This research makes a novel contribution by linking CQDs' surface charge to cytotoxic effects and oxidative stress, providing key insights into their safe use in biomedicine and filling a critical gap in nanoparticle toxicity studies.