Self-Assembled Microfiber-Like Biohydrogel for Ultrasensitive Whole-Cell Electrochemical Biosensing in Microdroplets

Abstract

A novel microfiber-like biohydrogel was fabricated by a facile approach relying on electroactive bacteria-induced graphene oxide reduction and confined self-assembly in a capillary tube. The microfiber-like biohydrogel (d = ∼1 mm) embedded high-density living cells and activated efficient electron exchange between cells and the conductive graphene network. Further, a miniature whole-cell electrochemical biosensing system was developed and applied for fumarate detection under −0.6 V (vs Ag/AgCl) applied potential. Taking advantage of its small size, high local cell density, and excellent electron exchange, this microfiber-like biohydrogel-based sensing system reached a linear calibration curve (R2 = 0.999) ranging from 1 nM to 10 mM. The limit of detection obtained was 0.60 nM, which was over 1300 times lower than a traditional biosensor for fumarate detection in 0.2 μL microdroplets. This work opened a new dimension for miniature whole-cell electrochemical sensing system design, which provided the possibility for bioelectrochemical detection in small volumes or three-dimensional local detection at high spatial resolutions.

Graphene‐Based Engineered Living Materials

“…[35] The increase of the local cell density with embedding the microorganism on the basal plane of rGO nanosheets leads to an improvement in the electron exchange efficiency and as a result, the high sensitivity. [35] Reduced graphene oxide (rGO) nanosheets can be incorporated into the bacterial cellulose (BC) hydrogels using this biosynthesis protocol to fabricate BC/rGO nanocomposites. [36] Culturing Komagataeibacter xylinus (K. xylinus) in a Hestrin-Schramm (HS) medium containing low concentrations of rGO nanosheets (< 1 wt.%) can lead to the fabrication of electrically conductive hydrogels.…”

“…electrochemical sensing. [35] High-resolution sensing that can be provided with such a system can make the idea of fast point-of-care sensing. [35] Graphene-based hydrogels can also be used as conductive scaffolds for the development of living hydrogels with cells encapsulated in the porous structure of the hydrogel.…”

“…When a low concentration of Shewanella oneidensis (1 mL solution with the OD600 of 8) is mixed with a low concentration of GO (1 mL solution with a concentration of 2 mg mL −1 ) and the mixture solution is injected into a capillary tube, the bioreduction of GO by the microorganism results in the formation of biohydrogel sensors that can present high molecular‐level sensing properties. [ 35 ] The fabricated microfiber‐like whole‐cell electrochemical biosensor can present a linear calibration curve ranging from 1 nM to 10 mM with a sensing limit of 0.60 nM. [ 35 ] The increase of the local cell density with embedding the microorganism on the basal plane of rGO nanosheets leads to an improvement in the electron exchange efficiency and as a result, the high sensitivity.…”

“…[ 35 ] The increase of the local cell density with embedding the microorganism on the basal plane of rGO nanosheets leads to an improvement in the electron exchange efficiency and as a result, the high sensitivity. [ 35 ]…”

“…Moreover, electroactive bacteria‐induced reduction of GO nanosheets can also lead to the formation of microfiber‐like biohydrogels applicable in miniature whole‐cell electrochemical sensing. [ 35 ] High‐resolution sensing that can be provided with such a system can make the idea of fast point‐of‐care sensing. [ 35 ]…”