Impact of structural features of SBA-15 host particles on activity of immobilized glucose oxidase enzyme and sensitivity of a glucose sensor Anees Y. Khan • Santosh B. Noronha • Rajdip Bandyopadhyaya Ó Springer Science+Business Media New York 2015 Abstract 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 lA/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. Keywords Mesoporous silica  Glucose oxidase  Enzyme immobilization  Enzyme activity  Biosensor 1 Introduction Immobilized enzyme based biosensors are in demand, because they are highly selective to their targeted substrates. Activity of the immobilized enzyme determines performance of the biosensor [1]. Therefore, the focus is on materials which can immobilize a large quantity of enzyme, enhance activity of the immobilized enzyme and thereby, result in an improved biosensor performance. In this regard, several materials have been used as hosts for enzyme immobilization, which include carbon nanotubes [2], graphene [3], cellulose [4], conducting polymers [5], chitosan [6] etc. Recent breakthroughs in the synthesis of mesoporous silica, in terms of controlled mor- phology, particle size, and internal pore diameter have made them attractive hosts for enzyme immobilization. Both external particle aspect ratio and internal pore diameter of mesoporous silica particles have been varied to achieve higher enzyme loading [7][8][9][10]. These results show that, with a shorter particle and therefore (mesopore) length and a larger pore diameter, the higher internal surface area of pores can be made accessible to appropriately sized enzyme molecule, and enzyme loading can be increased. However, a higher enzyme loading may not always lead to a higher enzyme activity too [11]. Factors which prevent loss in activity of immobilized enzyme are: little or no change in conformation of the immobilized enzyme molecule, less aggregation of immobilized enzyme molecule and lower diffusional resistance to the substrate. In this regard, in liter- ature, pore diameter of the host has been varied to achieve enhanced activity of the immobilized enzyme. For example, when host pore diameter was similar to size of enzyme Electronic supplementary material The online version of this article (doi:10.1007/s10934-014-9905-5) contains supplementary material, which is available to authorized users. A. Y. Khan  S. B. Noronha (&)  R. Bandyopadhyaya (&) Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India e-mail: noronha@che.iitb.ac.in R. Bandyopadhyaya e-mail: rajdip@che.iitb.ac.in 123 J Porous Mater DOI 10.1007/s10934-014-9905-5