Impact of structural features of SBA-15 host particles on activity of immobilized glucose oxidase enzyme and sensitivity of a glucose sensor

Glucose oxidase (GOD) enzyme immobilized mesoporous silica particles (SBA-15) have been developed as an amperometric glucose sensor. SBA-15 particles with fibre, rod and cuboid morphologies of decreasing aspect ratio (12.1, 4.6 and 1.1), and increasing mesopore diameter (6.8, 6.8 and 11.4 nm), respectively, were synthesized, to understand the role of these structural parameters on enzyme activity and sensor performance. Microscopy and gas sorption experiments confirm that, as required, GOD (~7 nm size) immobilizes inside mesopores. Amongst all forms, cuboid SBA-15 showed the highest normalized absolute activity and reusability for at least six cycles. Thus, compared to rod SBA-15, an electrode with GOD immobilized-cuboid SBA-15 showed ten times higher sensitivity of 0.53 µA/cm 2 /mM, with a linearity range of 1.0–7.7 mM glucose and a short response time (<5 s). Hence, structural features of the host could be directly related to the sensor performance. Therefore, in general, SBA-15 hosts with a smaller particle aspect ratio and a larger internal mesopore diameter (like cuboid), together with appropriate enzyme loading density and presence of ferrocene as an electron mediator, can ensure a superior biosensor performance.