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Conductive polymers, owing to their tunable mechanical and electrochemical properties, are viable candidates to replace metallic components for the development of biosensors and bioelectronics. However, conducting fibers/wires fabricated from these intrinsically conductive and mechanically flexible polymers are typically produced without protective coatings for physiological environments. Providing sheathed conductive fibers/wires can open numerous opportunities for fully organic biodevices. In this work, we report on a facile method to fabricate core-sheath poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) PEDOT:PSS-silk fibroin conductive wires. The conductive wires are formed through a wet-spinning process, and then coated with an optically transparent, photocrosslinkable silk fibroin sheath for insulation and protection in a facile and scalable process. The sheathed fibers were evaluated for their mechanical and electrical characteristics and overall stability. These wires can serve as flexible connectors to an organic electrode biosensor. The entire, fully organic, biodegradable, and free-standing flexible biosensor demonstrated a high sensitivity and rapid response for the detection of ascorbic acid as a model analyte. The entire system can be proteolytically biodegraded in a few weeks. Such organic systems can therefore provide promising solutions to address challenges in transient devices and environmental sustainability. 

Mechanically flexible and conformable materials and integrated devices have found diverse applications in personalized healthcare as diagnostics and therapeutics, tissue engineering and regenerative medicine constructs, surgical tools, secure systems, and assistive technologies. In order to impart optimal mechanical properties to the (bio)materials used in these applications, various strategies have been explored—from composites to structural engineering. In recent years, geometric cuts inspired by the art of paper‐cutting, referred to as kirigami, have provided innovative opportunities for conferring precise mechanical properties via material removal. Kirigami‐based approaches have been used for device design in areas ranging from soft bioelectronics to energy storage. In this review, the principles of kirigami‐inspired engineering specifically for biomedical applications are discussed. Factors pertinent to their design, including cut geometry, materials, and fabrication, and the effect these parameters have on their properties and configurations are covered. Examples of kirigami designs in healthcare are presented, such as, various form factors of sensors (on skin, wearable), implantable devices, therapeutics, surgical procedures, and cellular scaffolds for regenerative medicine. Finally, the challenges and future scope for the successful translation of these biodesign concepts to broader deployment are discussed.

 

Chitin, one of the most abundant natural amino polysaccharides, is obtained primarily from the exoskeletons of crustaceans, crabs and shrimp. Chitin and its derivative chitosan have gained much attention in the field of biomedical research due to attractive properties such as biocompatibility, non-toxicity, biodegradability, low immunogenicity, and ease of availability. While work has been done on the use of chitin and chitosan as functional biomaterials by imparting specific properties, the potential of chitin as a biomaterial is somewhat limited owing to its intractable processing. In this work, we propose a facile reaction to modify the chitin chain with photoactive moieties for the realization of photocrosslinkable chitin. This chitin derivative is easily usable with a benign solvent formic acid to be able to form mechanically robust, optically transparent sheets. These films exhibit comparable tensile properties to that of native chitin and chitosan and better surface wettability. Most importantly, this material can be used to form precise, high resolution microarchitectures on both rigid and flexible substrates using a facile bench top photolithography technique. These flexible micropatterned 2D sheets of chitin were demonstrated as a dynamic cell culture substrate for the adhesion and proliferation of fibroblasts, wherein the chitin micropatterns act as a template for spatial guidance of cells. This chitin-based biopolymer can find diverse uses in tissue engineering as well as to form components for degradable bioelectronics.