Surface Morphology Control and Amino Functionalization of Silicon Nanoparticles for Enhanced Antibody Immobilization

The large specific surface area of nanoparticles makes them an attractive platform for antibody immobilization in immunoassays, but the combined effects of their surface structuring and chemical functionalization on properties relevant to antibody immobilization have not yet been clarified. Here, porous and spiky silicon nanoparticles (SiNPs) were fabricated by metal-assisted chemical etching, and the relationships among specific surface area, amino functionalization, and the JT-95-related ELISA signal following BS3-mediated immobilization were investigated. The formation of the porous and spiky surface structures was confirmed by scanning electron microscopy, including quantitative image analysis, and nitrogen adsorption analysis revealed that the specific surface area increased from 62.3 m² g^-1 for pristine SiNPs to 111.8 and 142.2 m² g^-1 for porous and spiky SiNPs, respectively. Fourier transform infrared spectroscopy and the ninhydrin assay confirmed successful amino functionalization, and the ninhydrin response increased with increasing specific surface area. An enzyme-linked immunoassay further demonstrated that the JT-95-related ELISA signal was significantly higher for amino-functionalized porous and spiky SiNPs than for amino-functionalized pristine SiNPs (p < 0.01). Although the mean ELISA signal was higher for spiky SiNPs than for porous SiNPs, the difference was not statistically significant. Overall, these results strongly suggest an association among increased specific surface area, enhanced amino functionalization, and increased JT-95-related ELISA signal. These findings provide useful design guidelines for SiNP-based antibody immobilization platforms and their future application in immunoassays and biosensing.