Nanogram-scale real-time monitoring of bioorganic interfaces as mineralization platforms on titanium dioxide via quartz crystal microbalance

Bioorganic coatings on inorganic nanoparticles are widely investigated for their ability to promote biomimetic mineralization. However, direct quantitative comparisons of their real-time mineralization efficiency remain limited. In this study, we applied quartz crystal microbalance (QCM)-based analytical platform to monitor and compare the mineralization kinetics of zein- and polydopamine (PDA)-coated titanium dioxide (TiO₂) nanoparticles, with an average diameter of approximately 300 nm, under simulated physiological conditions. After immersion in simulated body fluid (SBF), both coating systems facilitated the formation of calcium phosphate layers with comparable crystallinity and chemical composition, as confirmed by FTIR, XRD, and XPS analyses. Despite the structural similarity of the resulting mineral layers, QCM measurements revealed that PDA-coated TiO₂ accumulated about 37 % greater mass accumulation than zein-coated TiO₂ within the same timeframe. This accelerated mineralization behavior indicates a higher coating efficiency on the PDA surface, likely due to its denser distribution of ion-binding functional groups. These results highlight the effectiveness of QCM in detecting meaningful differences in mineralization behavior at the nanogram scale, and support the use of PDA as a highly efficient interfacial platform for calcium phosphate formation during the mineralization process.