Engineering cell adhesion: Poly-l-lysine-induced micro- and nanoscale surface modifications and their impact on...

Poly-l-lysine (PLL) is widely used to modify substrate surfaces and enhance cell adhesion. This study investigates the micro- and nanoscale surface modifications induced by PLL coatings and their impact on cell biochemistry and morphology. Using Raman and atomic force microscopy-infrared (AFM-IR) spectroscopy, we identified biochemical responses in cells adhering to PLL-coated calcium fluoride (CaF₂) substrates. Atomic force microscopy (AFM) revealed that prolonged PLL incubation increased surface roughness, significantly influencing cell morphology. Notably, minor changes in PLL incubation time and surface roughness led to a transition from spindle-like to more rounded and flattened cell shapes. The highest roughness (Ra = 4.46 nm) was observed after 30 min of incubation PLL, in comparison to the untreated CaF₂ surface (Ra = 2.26 nm), and correlated with increased levels of cytochrome C and phenylalanine-biomarkers associated with apoptosis. This suggests that extended PLL incubation may induce cytotoxic effects. Nanoscale analysis further demonstrated alterations in protein concentrations and secondary structures, even with minimal surface modifications. These findings provide insights into the relationship between PLL-induced surface modifications and cellular responses, emphasizing the importance of precise control over surface properties in biomaterial applications to optimize cell adhesion and viability.