"Smart tattoo" glucose biosensors and effect of coencapsulated anti-inflammatory agents

Background

Minimally invasive glucose biosensors with increased functional longevity form one of the most promising techniques for continuous glucose monitoring. In the present study, we developed a novel nanoengineered microsphere formulation comprising alginate microsphere glucose sensors and anti-inflammatory-drug-loaded alginate microspheres.

Methods

The formulation was prepared and characterized for size, shape, in vitro drug release, biocompatibility, and in vivo acceptability. Glucose oxidase (GOx)- and Apo-GOx-based glucose sensors were prepared and characterized. Sensing was performed both in distilled water and simulated interstitial body fluid. Layer-by-layer self-assembly techniques were used for preventing drug and sensing chemistry release. Finally, in vivo studies, involving histopathologic examination of subcutaneous tissue surrounding the implanted sensors using Sprague–Dawley rats, were performed to test the suppression of inflammation and fibrosis associated with glucose sensor implantation.

Results

The drug formulation showed 100% drug release with in 30 days with zero-order release kinetics. The GOx-based sensors showed good enzyme retention and enzyme activity over a period of 1 month. Apo-GOx-based visible and near-infrared sensors showed good sensitivity and analytical response range of 0–50 mM glucose, with linear range up to 12 mM glucose concentration. In vitro cell line studies proved biocompatibility of the material used. Finally, both anti-inflammatory drugs were successful in controlling the implant–tissue interface by suppressing inflammation at the implant site.

Conclusion

The incorporation of anti-inflammatory drug with glucose biosensors shows promise in improving sensor biocompatibility, thereby suggesting potential application of alginate microspheres as “smart tattoo” glucose sensors with increased functional longevity.