Skin-Integrated Wearable Systems and Implantable Biosensors: A Comprehensive Review

Biosensors devices have attracted the attention of many researchers across the world. They have the capability to solve a large number of analytical problems and challenges. They are future ubiquitous devices for disease diagnosis, monitoring, treatment and health management. This review presents an overview of the biosensors field, highlighting the current research and development of bio-integrated and implanted biosensors. These devices are micro- and nano-fabricated, according to numerous techniques that are adapted in order to offer a suitable mechanical match of the biosensor to the surrounding tissue, and therefore decrease the body’s biological response. For this, most of the skin-integrated and implanted biosensors use a polymer layer as a versatile and flexible structural support, combined with a functional/active material, to generate, transmit and process the obtained signal. A few challenging issues of implantable biosensor devices, as well as strategies to overcome them, are also discussed in this review, including biological response, power supply, and data communication.

A Dual Network Hydrogel Sunscreen Based on Poly-γ-glutamic Acid/Tannic Acid Demonstrates Excellent Anti-UV, Self-Recovery, and Skin-Integration Capacities

Novel sunscreen products based on bioadhesive/gel systems that can prevent the skin penetration behaviors of UV filters have attracted increasing attention in recent years. However, integration is very difficult to achieve and control on the wet surface of the skin under sweaty/dynamic physiological conditions, resulting in functional failure. Herein, we demonstrated the fabrication of a novel dual-network hydrogel sunscreen (DNHS) based on poly-γ-glutamic acid (γ-PGA) and tannic acid (TA), which demonstrated prominent UV protection properties across broad UVA and UVB regions (360-275 nm). Due to a three-dimensional network microstructure and a highly hydrated nature that mimics the extracellular matrix of natural skin, DNHS can perfectly match the skin surface without irritation and sensitization. In addition, the intermolecular hydrogen bond interactions of γ-PGA and TA provide an important driving force for coacervation, which endows the DNHS with remarkable self-recovery properties (within 60 s). Moreover, due to the multiple interfacial interactions between γ-PGA/TA and the protein-rich skin tissue surfaces, DNHS simultaneously possesses excellent skin-integration and water-resistance capacities, and it can be readily removed on demand. Our results highlight the potential of the DNHS to be used in next-generation sunscreens by providing long-term and stable UV protection functions even under sweaty/dynamic physiological conditions.