The Investigation of the Waveguiding Properties of Silk Fibroin from the Visible to Near-Infrared Spectrum

Biocompatible and Biodegradable Polymer Optical Fiber for Biomedical Application: A Review

This article discusses recent advances in biocompatible and biodegradable polymer optical fiber (POF) for medical applications. First, the POF material and its optical properties are summarized. Then, several common optical fiber fabrication methods are thoroughly discussed. Following that, clinical applications of biocompatible and biodegradable POFs are discussed, including optogenetics, biosensing, drug delivery, and neural recording. Following that, biomedical applications expanded the specific functionalization of the material or fiber design. Different research or clinical applications necessitate the use of different equipment to achieve the desired results. Finally, the difficulty of implanting flexible fiber varies with its flexibility. We present our article in a clear and logical manner that will be useful to researchers seeking a broad perspective on the proposed topic. Overall, the content provides a comprehensive overview of biocompatible and biodegradable POFs, including previous breakthroughs, as well as recent advancements. Biodegradable optical fibers have numerous applications, opening up new avenues in biomedicine.

Photoelectric Silk via Genetic Encoding and Bioassisted Plasmonics

Genetically encoded photoelectric silk that can convert photons to electrons (light to electricity) over a wide visible range in a self-power mode is reported. As silk is a versatile host material with electrical conductivity, biocompatibility, and processability, a photoelectric protein is genetically fused with silk by silkworm transgenesis. Specifically, mKate2, which is conventionally known as a far-red fluorescent protein, is used as a photoelectric protein. Characterization of the electrochemical and optical properties of mKate2 silk allows designing a photoelectric measurement system. A series of in situ photocurrent experiments support the sensitive and stable performance of photoelectric conversion. In addition, as a plasmonic nanomaterial with a broad spectral resonance, titanium nitride (TiN) nanoparticles are biologically hybridized into the silk glands, taking full advantage of the silkworms' open circulatory system as well as the absorption band of mKate2 silk. This biological hybridization via direct feeding of TiN nanoparticles further enhances the overall photoelectric conversion ability of mKate2 silk. It is envisioned that the biologically derived photoelectric protein, its ecofriendly scalable production by transgenic silkworms, and the bioassisted plasmonic hybridization can potentially broaden the biomaterial choices for developing next-generation biosensing, retina prosthesis, and neurostimulation applications.

Interplay between Light and Functionalized Silk Fibroin and Applications

Silkworm silk has been considered to be a luxurious textile for more than five thousand years. Native silk fibroin (SF) films have excellent (ca. 90%) optical transparency and exhibit fluorescence under UV light. The silk dyeing process is very important and difficult, and methods such as pigmentary coloration and structural coloration have been tested for coloring silk fabrics. To functionalize silk that exhibits fluorescence, the in vivo and in vitro assembly of functional compounds with SF and the resulting amplification of fluorescence emission are examined. Finally, we discuss the applications of SF materials in basic optical elements, light energy conversion devices, photochemical reactions, sensing, and imaging. This review is expected to provide insight into the interaction between light and silk and to inspire researchers to develop silk materials with a consideration of history, material properties, and future prospects.

Chemical Synthesis of Silk-Mimetic Polymers

Silk is a naturally occurring high-performance material that can surpass man-made polymers in toughness and strength. The remarkable mechanical properties of silk result from the primary sequence of silk fibroin, which bears semblance to a linear segmented copolymer with alternating rigid ("crystalline") and flexible ("amorphous") blocks. Silk-mimetic polymers are therefore of great emerging interest, as they can potentially exhibit the advantageous features of natural silk while possessing synthetic flexibility as well as non-natural compositions. This review describes the relationships between primary sequence and material properties in natural silk fibroin and furthermore discusses chemical approaches towards the synthesis of silk-mimetic polymers. In particular, step-growth polymerization, controlled radical polymerization, and copolymerization with naturally derived silk fibroin are presented as strategies for synthesizing silk-mimetic polymers with varying molecular weights and degrees of sequence control. Strategies for improving macromolecular solubility during polymerization are also highlighted. Lastly, the relationships between synthetic approach, supramolecular structure, and bulk material properties are explored in this review, with the aim of providing an informative perspective on the challenges facing chemical synthesis of silk-mimetic polymers with desirable properties.

Soft and Stretchable Polymeric Optical Waveguide-Based Sensors for Wearable and Biomedical Applications

The past decades have witnessed the rapid development in soft, stretchable, and biocompatible devices for applications in biomedical monitoring, personal healthcare, and human-machine interfaces. In particular, the design of soft devices in optics has attracted tremendous interests attributed to their distinct advantages such as inherent electrical safety, high stability in long-term operation, potential to be miniaturized, and free of electromagnetic interferences. As the alternatives to conventional rigid optical waveguides, considerable efforts have been made to develop light-guiding devices by using various transparent and elastic polymers, which offer desired physiomechanical properties and enable wearable/implantable applications in optical sensing, diagnostics, and therapy. Here, we review recent progress in soft and stretchable optical waveguides and sensors, including advanced structural design, fabrication strategies, and functionalities. Furthermore, the potential applications of those optical devices for various wearable and biomedical applications are discussed. It is expected that the newly emerged soft and stretchable optical technologies will provide a safe and reliable alternative to next-generation, smart wearables and healthcare devices.