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

Here, SiO nanoparticles-based biosensors were developed for the non-faradaic EIS detection of human cytomegalovirus which is responsible for newborn babies' disability. Mesoporous SiO nanoparticles were fabricated through sol-gel approach using anionic surfactant with an average size of 144 ± 18.6 nm. For biosensing, SiO 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 SiO nanoparticles at the surface was investigated. APTES was introduced before and after drop casting SiO nanoparticles. APTES functionalization after drop casting yielded better SiO 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.