The prevalence of cancer remains a major health issue globally. Current treatments, such as chemotherapy and radiation, often result in severe side effects due to their non-selective nature. As an alternative, targeted photodynamic therapy (PDT) has emerged as a promising solution due to its specificity and reduced systemic toxicity. However, challenges such as solubility and stability in biological media need to be addressed to enhance efficacy. This research aims to develop and assess a novel nanogel system for encapsulating two types of SiQDs—Acid-SiQDs and Acid-PEO-SiQDs—and to evaluate their efficacy in targeted photodynamic therapy against HeLa cells. The nanogels were synthesized using a copolymer matrix of Di(ethylene glycol) methyl ether methacrylate (DEGMA) and 2-Methacryloyloxyethyl phosphorylcholine (MPC) via reversible addition-fragmentation chain transfer (RAFT) polymer...