Synthesis, characterization, and photodynamic therapeutic evaluation of manganese- and copper-doped Zn₃(PO₄)₂ nanosheets as photosensitizers for hela cell phototoxicity

Abstract

Nanoparticle‑based photosensitizers have emerged as efficient agents for photodynamic therapy (PDT). Here, pure, Mn‑doped, and Cu‑doped Zn₃(PO₄)₂ nanosheets were synthesized for the first time via a controllable co‑precipitation route, enabling precise control over morphology and thickness. Structural and compositional analyses (XRD, SEM, EDS) verified crystalline phase formation and dopant incorporation, while DLS and zeta potential confirmed uniform size distribution and colloidal stability. The optical properties were systematically investigated using UV–Vis absorption and photoluminescence (PL) spectroscopy. Mn²⁺ doping induced enhanced visible‑light absorption and characteristic emission features, indicating long‑lived excited states favorable for photodynamic activity, whereas Cu²⁺ doping introduced non radiative recombination centers. The photodynamic performance was evaluated through methylene blue photobleaching and anthracene oxidation under red‑light irradiation, confirming generation of efficient reactive oxygen species and pre dominantly Type )II( PDT behavior. In vitro cytotoxicity and photodynamic efficiency were assessed using MTT assays on HeLa cells. Cytotoxicity tests on HeLa cells under red LED illumination showed negligible dark toxicity but marked phototoxicity for Mn‑doped nanosheets, correlating structural doping effects with biological performance. This work intro duces co‑precipitation as a new synthesis route for Zn₃(PO₄)₂‑based nanosheets and establishes their dopant‑dependent optical and therapeutic potential for PDT applications.