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

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.

Ischemic preconditioning protects against ischemic brain injury.

In this study, we hypothesized that an increase in integrin αvß3 and its co-activator vascular endothelial growth factor play important neuroprotective roles in ischemic injury. We performed ischemic preconditioning with bilateral common carotid artery occlusion for 5 minutes in C57BL/6J mice. This was followed by ischemic injury with bilateral common carotid artery occlusion for 30 minutes. The time interval between ischemic preconditioning and lethal ischemia was 48 hours. Histopathological analysis showed that ischemic preconditioning substantially diminished damage to neurons in the hippocampus 7 days after ischemia. Evans Blue dye assay showed that ischemic preconditioning reduced damage to the blood-brain barrier 24 hours after ischemia. This demonstrates the neuroprotective effect of ischemic preconditioning. Western blot assay revealed a significant reduction in protein levels of integrin αvß3, vascular endothelial growth factor and its receptor in mice given ischemic preconditioning compared with mice not given ischemic preconditioning 24 hours after ischemia. These findings suggest that the neuroprotective effect of ischemic preconditioning is associated with lower integrin αvß3 and vascular endothelial growth factor levels in the brain following ischemia.