OBJECTIVE: ALA-PDT (5-aminolevulinic acid photodynamic therapy) is a central modality in the treatment of skin diseases. Increasing the bioavailability of ALA remains a critical issue. With this in mind, our study explores a novel route of ALA delivery by loading acrylic nanoparticles (ANPs). METHODS: ALA-ANPs were synthesized by emulsion polymerisation and characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). The effects of ALA-ANPs on HaCaT cell line were evaluated, including characteristics, morphological changes, protoporphyrin IX (PpIX) fluorescence kinetics, reactive oxygen species (ROS) levels, mitochondrial membrane potential and ki67 expression in these cells. RESULTS: The ANPs had uniform sizes, smooth surfaces and excellent light transmittance, with diameters of 150-200 nm. In contrast, the ALA - ANPs had uneven surfaces and poor light transmittance, with diameters of 220-250 nm. During 12 hours of co-incubation of HaCaT cells with ALA, the intracellular accumulation of PpIX increased over time. Notably, after 6 hours of incubation, PpIX levels induced by 1.81 mg/mL ALA-ANPs exceeded those induced by 1.0 mM ALA (). CCK-8 results showed a positive correlation between PDT-induced inhibition of HaCaT cell proliferation and ALA concentration when ALA concentration remained below 2.0 mM. Compared to the 1.0 mM ALA group, the 1.81 mg/mL ALA-ANPs group showed decreased mitochondrial membrane potential, ki67 immunofluorescence intensity and cell proliferation. In contrast, ROS levels were significantly increased in the 1.81 mg/mL ALA-ANPs group (p < 0.01). CONCLUSION: Loading ANPs provide improved stability and potency for ALA. The ALA-ANPs-PDT approach has superior inhibitory effects on HaCaT proliferation in vitro.