Non-faradaic electrochemical biosensor based on APTES-modified core-shell silica nanoparticles

Here, SiO₂ nanoparticles-based biosensors were developed for the non-faradaic EIS detection of human cytomegalovirus which is responsible for newborn babies' disability. Mesoporous SiO₂ nanoparticles were fabricated through sol-gel approach using anionic surfactant with an average size of 144 ± 18.6 nm. For biosensing, SiO₂ nanoparticles were drop casted on top of interdigitated gold electrodes on plastic substrate and functionalized with different concentrations of APTES (1, 2, 4 and 8 %). Then, UL83-antibodies were immobilized at the surface via glutaraldehyde. As APTES concentration increased, the sensitivity decreased from 13.99 to 10.78 nF/ln(ng/mL). However, the limit of detection improved from 6 to 2 ng/mL. Before biosensing, the coverage of APTES at the surface was characterized with XPS and faradaic EIS. Furthermore, the effect of APTES functionalization approach on the coverage of SiO₂ nanoparticles at the surface was investigated. APTES was introduced before and after drop casting SiO₂ nanoparticles. APTES functionalization after drop casting yielded better SiO₂ nanoparticles coverage on the surface which is essential for non-faradaic EIS biosensing. Uneven coverage would result in deteriorated biosensing performances, especially for non-faradaic biosensors which rely on interfacial capacitive changes upon bioreceptor/antigen interactions.