A comparative study of graphene–hydrogel hybrid bionanocomposites for biosensing

Abstract

Hydrogels have become increasingly popular as immobilization materials for cells, enzymes and proteins for biosensing applications. Enzymatic biosensors that utilize hydrogel as an encapsulant have shown improvements over other immobilization techniques such as cross linking and covalent bonding. However, to date there are no studies which directly compare multiple hydrogel-graphene nanocomposites using the same enzyme and test conditions. This study compares the performance of four different hydrogels used as protein encapsulants in a mediator-free biosensor based on graphene-nanometal-enzyme composites. Alcohol oxidase (AOx) was encapsulated in chitosan poly-N-isopropylacrylamide (PNIPAAM), silk fibroin or cellulose nanocrystals (CNC) hydrogels, and then spin coated onto a nanoplatinum-graphene modified electrode. The transduction mechanism for the biosensor was based on AOx-catalyzed oxidation of methanol to produce hydrogen peroxide. To isolate the effect(s) of stimulus response on biosensor behavior, all experiments were conducted at 25 °C and pH 7.10. Electroactive surface area (ESA), electrochemical impedance spectroscopy (EIS), sensitivity to methanol, response time, limit of detection, and shelf life were measured for each bionanocomposite. Chitosan and PNIPAAM had the highest sensitivity (0.46 ± 0.2 and 0.3 ± 0.1 μA mM(-1), respectively) and electroactive surface area (0.2 ± 0.06 and 0.2 ± 0.02 cm(2), respectively), as well as the fastest response time (4.3 ± 0.8 and 4.8 ± 1.1 s, respectively). Silk and CNC demonstrated lower sensitivity (0.09 ± 0.02 and 0.15 ± 0.03 μA mM(-1), respectively), lower electroactive surface area (0.12 ± 0.02 and 0.09 ± 0.03 cm(2), respectively), and longer response time (8.9 ± 2.1 and 6.3 ± 0.8 s, respectively). The high porosity of chitosan, PNIPAAM, and silk gels led to excellent transport, which was significantly better than CNC bionanocomposites. Electrochemical performance of CNC bionanocomposites were relatively poor, which may be linked to poor gel stability. The differences between the Chitosan/PNIPAAM group and the Silk/CNC group were statistically significant (p < 0.05) based on ANOVA. Each of these composites was within the range of other published devices in the literature, while some attributes were significantly improved (namely response time and shelf life). The main advantages of these hydrogel composites over other devices is that only one enzyme is required, all materials are non-toxic, the sensor does not require mediators/cofactors, and the shelf life and response time are significantly improved over other devices.

Bio-inspired patterned networks (BIPS) for development of wearable/disposable biosensors

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“…Apollonian gaskets optimize the positions of circles in the 2D domain from randomly placed circles, while minimizing distance between circles. The gasket in After printing the graphene ink, fractal nanoplatinum was deposited using pulsed sonoelectrodeposition ( [6], [22] to create a transducer layer as the working electrode and electrodes were biofunctionalized for measuring glucose (described below).…”

“…Patterned graphene ink electrodes were decorated with nanoplatinum based on [6], [22]. Nanoplatinum was deposited for 60 seconds in a solution of 0.72% chloroplatinic acid and 0.001% lead acetate at 10V in DI water at 20°C at a pulsed frequency of 900 mHz.…”

A Miniature Graphene-based Biosensor for Intracellular Glucose Measurements

“…Its remarkable properties have opened up a whole realm of applications [3,[8][9][10][11], amongst which biosensing has been capturing a huge interest [12][13][14]. This is mainly because of the great promise and performance owning to its tremendously large surface area to volume ratio as a dominating and favorable parameter for sensing applications [8,15,16].…”

Continuous release of bone morphogenetic protein-2 through nano-graphene oxide-based delivery influences the activation of the NF-&kappa;B signal transduction pathway

“…45,46 Most importantly, oxygen-containing groups on the surface of GO molecules may interact with hydroxyl groups of the BMP2 molecules through hydrogen bonding. 47,48 Third, the atomic layer framework of GO is of good mechanical strength, 49 which may provide mechanical support. At the molecular level, GO molecules are dispersed …”