Kinetically Doped Silica Sol–Gel Optical Biosensors: Expanding Potential Through Dip-Coating

Abstract

Kinetic doping has previously been shown to be an effective method of doping silica sol–gel thin films with an enzyme to construct biosensors. Until now, kinetic doping has only been applied to films produced through the spin-coating method. In this study, we present the use of dip-coating to produce thin films kinetically doped for biosensor development. In this way, kinetically doped biosensors may benefit from the increased range of substrate material shapes and sizes that may be easily coated through dip-coating but not spin-coating. The biosensors produced through dip-coating continue to show enhanced performance over more conventional enzyme loading methods with horseradish peroxidase and cytochrome C samples, showing an increase of 2400× and 1300× in enzyme concentration over that in their loading solutions, respectively. These correspond to enzyme concentrations of 5.37 and 10.57 mmol/L all while preserving a modest catalytic activity for the detection of hydrogen peroxide by horseradish peroxidase. This leads to a 77% and 88% increase in the total amount of horseradish peroxidase and cytochrome C, respectively, over that from coating the same glass coverslip via spin-coating methods.

Amine Functionalization of Silica Sol–Gel Thin Films via Kinetic Doping: A Novel, Green Approach

“…Dopants that do not disrupt film structure have been shown to have an optimal delay time of 5 min for drain coating. 34 This may be different for BPEI, as the extent of polycondensation of the silica network increases with the delay time. Due to its basic nature, BPEI may load better into a thin film that has different levels of condensation than dopants that are relatively neutral.…”

Enzyme Loading in Internally-Coated Capillary Tubes Via Kinetic Doping

“…Thin films were prepared by drain coating with a sol solution inside a centrifuge tube, based on the drain coated film preparation method of Crosley et al [33]. After aging for 20 h, the silica sol solution was transferred to a 50 mL round-bottom glass centrifuge tube, elevated by a jack stand.…”

“…The enclosure inherent in capillary tubes impeded this evaporation, slowing the formation of the films. Additionally, exposure to the sol vapors is known to negatively affect flat surface films, damaging the structural integrity of the film [33]. Instead of a continuous film, exposure to vapors resulted in sparse aggregates.…”

“…This results in enzymes that are entrapped in the silica matrix through an economical and widely accessible technique. Kinetic doping has been shown to exhibit a high dopant capacity, produce films with good retention of enzyme activity, and nearly instantaneous response time [33]. This could lead to an inexpensive manufacturing process for enzyme-coated glass capillary tubes that is low on both material and labor cost, which is significant for potential commercialization.…”

Reusable, Non-Invasive, and Ultrafast Radio Frequency Biosensor Based on Optimized Integrated Passive Device Fabrication Process for Quantitative Detection of Glucose Levels

“…Moreover, another key factor limiting the application of electrochemical sensors is the fact that the electrolytes need to be replenished on a regular basis, which significantly increase burden to subsequent costs [30][31][32]. With regard to optical biosensors, it needs a long settling time for detection and is highly susceptible to change the test results for ambient light [33][34][35][36][37][38][39][40][41]. Recently, a biosensor based on radio frequency (RF) techniques has attracted enormous attention and is regarded as a promising and competitive candidate for implementing third-generation glucose biosensors [42][43][44][45][46][47].…”