**2.4 Silica (SiO2)**

Silica is a naturally occurring mineral that is commonly used as a support material for enzyme immobilization in biosensors [7, 8].

### **2.5 Graphene oxide (GO)**

GO is a form of graphene that has oxygen-containing functional groups on its surface. It is a promising material for biosensors due to its high surface area, biocompatibility, and ability to facilitate electron transfer reactions [9, 10].
