We studied the enzyme glucose oxidase (GOx) immobilization on silicon oxide surfaces. In particular, we optimized the immobilization protocol and verified that it fulfills both requirements of enzyme preservation (measured by enzymatic activity) and VLSI compatibility. The immobilization consists of four steps: oxide activation, silanization, linker molecule deposition and GOx immobilization. It is crucial to form an uniform linker layer on the sample surface in order to maximize the sites available for enzyme bonding and achieving the best enzyme deposition. In this study, utilizing glutaraldehyde as bifunctional reagent, we monitored its uniformity on the surface through X-ray Photoelectron Spectroscopy (XPS). Once optimized, the same protocol was used to anchor the enzyme in a porous silicon dioxide matrix. Gold labeled GOx molecules were monitored by electron diffraction X-ray (EDX) measurements coupled with scanning electron microscopy (SEM). The enzymatic activity was also monitored to confirm the goodness of the proposed immobilization method. Finally, the electrical characterization of MOS capacitors, showing a shift of about 1 V in the flat band voltage, demonstrated the possibility to use this approach for electrical detection.
Biosensors are a very useful tool to produce drugs or to monitor chemical species through their product of reaction. The sensor is fabricated bounding on its surface specific enzymes that can accomplish the synthesis function. We studied the possibility to fabricate Si-based micro-biosensors to detect glucose in water solutions using porous Si (PS) as surface to bound the specific enzyme. We ideated and fabricated a novel biosensor structure based on a PS membrane that can be used for glucose monitoring and for drug production, by properly choosing the enzyme to immobilize in the reactor. The fabrication details of the structure, having a suspended and auto-supporting PS membrane, through surface micromachining processes, ULSI compatible, are shown. Micro channels localised below the membrane will allow the buffer solution flow through the porous matrix. Moreover, in this work we acquired the know-how on the enzyme manipulation, bonding and detection on Si-based surfaces. The enzyme that accomplish the synthesis function is the glucose oxidase. We deposited it on different substrates: PS, bulk Si and on glass. On these samples photoluminescence, absorbance and optical microscopy measurements were performed.
Biosensors are a very useful tool to produce drugs or to monitor chemical species through their product of reaction. The sensor is fabricated bounding on its surface specific enzymes that can accomplish the synthesis function. We studied the possibility to fabricate Si-based micro-biosensors to detect glucose in water solutions. We used porous Si (PS) as surface to bound the glucose oxidase enzyme. We ideated an fabricated a novel biosensor structure based on a PS membrane that can be used for glucose monitoring and for drug production, by properly choosing the enzyme to immobilize in the reactor. The fabrication details of the structure, having a suspended and auto-supporting PS membrane, through surface micromachining processes, ULSI compatible, are shown. Micro channels localised below the membrane will allow the buffer solution flow through the porous matrix. Moreover, in this work we acquired the know-how on the enzyme manipulation, bonding and detection on Si-based surfaces. The glucose oxidase was deposited in PS, on bulk Si and on glass to perform photoluminescence, absorbance and optical microscopy measurements.
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