Nanoscale surface electrical properties of UV-exposed poly(lactic acid) films enriched with quercetin and magnesium. A kelvin probe force microscopy study

• KPFM revealed different nanoscale electrostatic properties between amorphous and crystalline PLA films. • Magnesium raised capacitance gradients and surface conductivity, while quercetin lowered them, especially in amorphous PLA. • UV-C irradiation centralized V CPD distributions, suggesting surface activation and conductivity increase. • PLA/Qr/Mg biocomposites combine Qr and Mg electrical responses in both crystalline and amorphous phases. Electrostatic forces at the micro/nanoscale play a central role in interactions between cell and biomaterial surfaces. Modifying the electroactive properties of biomaterials can promote cell-proliferation, stimulate bone formation, and reduce bacterial adhesion. Kelvin Probe Force Microscopy (KPFM) is a technique to investigate localized electrostatic behaviour in biodegradable polymers like poly(lactic acid) (PLA). The electrical response of PLA can be tuned by conductive fillers like magnesium (Mg). Previous studies showed that additives such as quercetin (Qr) stabilise PLA by mitigating its rapid UV-induced degradation. This work analyses how UV-treatment affects the nano-electrical properties of PLA composites with different dopants and crystallinity levels, focusing on two KPFM parameters: surface potential and capacitance gradient. Amorphous PLA is more sensitive to modifications than crystalline PLA, especially in surface potential. Qr and Mg exert opposite influences: Qr shifts potential towards more negative values, whereas Mg induces values closer to zero. Capacitance gradient correlates with conductivity and increases when Mg is incorporated. UV exposure induces dopant- and crystallinity-dependency, generally narrowing values around the mean, which reflects stabilised surface potential and enhanced conductivity after photoactivation. The electrical changes may be decisive in biomedical applications where sterilization of the biocomposite by UV-light is a prerequisite for its use.