Controllable Production of Natural Silk Nanofibrils for Reinforcing Silk-Based Orthopedic Screws.

As a natural high-performance material with a unique hierarchical structure, silk is endowed with superior mechanical properties. However, the current approaches towards producing regenerated silk fibroin (SF) for the preparation of biomedical devices fail to fully exploit the mechanical potential of native silk materials. In this study, using a top-down approach, we exfoliated natural silk fibers into silk nanofibrils (SNFs), through the disintegration of interfibrillar binding forces. The as-prepared SNFs were employed to reinforce the regenerated SF solution to fabricate orthopedic screws with outstanding mechanical properties (compression modulus > 1.1 GPa in a hydrated state). Remarkably, these screws exhibited tunable biodegradation and high cytocompatibility. After 28 days of degradation in protease XIV solution, the weight loss of the screw was ~20% of the original weight. The screws offered a favorable microenvironment to human bone marrow mesenchymal stem cell growth and spread as determined by live/dead staining, F-action staining, and Alamar blue staining. The synergy between native structural components (SNFs) and regenerated SF solutions to form bionanocomposites provides a promising design strategy for the fabrication of biomedical devices with improved performance.

Bioactive polymer-enabled conformal neural interface and its application strategies.

Neural interface is a powerful tool to control the varying neuron activities in the brain, where the performance can directly affect the quality of recording neural signals and the reliability of in vivo connection between the brain and external equipment. Recent advances in bioelectronic innovation have provided promising pathways to fabricate flexible electrodes by integrating electrodes on bioactive polymer substrates. These bioactive polymer-based electrodes can enable the conformal contact with irregular tissue and result in low inflammation when compared to conventional rigid inorganic electrodes. In this review, we focus on the use of silk fibroin and cellulose biopolymers as well as certain synthetic polymers to offer the desired flexibility for constructing electrode substrates for a conformal neural interface. First, the development of a neural interface is reviewed, and the signal recording methods and tissue response features of the implanted electrodes are discussed in terms of biocompatibility and flexibility of corresponding neural interfaces. Following this, the material selection, structure design and integration of conformal neural interfaces accompanied by their effective applications are described. Finally, we offer our perspectives on the evolution of desired bioactive polymer-enabled neural interfaces, regarding the biocompatibility, electrical properties and mechanical softness.

Natural Silk Nanofibril Aerogels with Distinctive Filtration Capacity and Heat-Retention Performance.

Nanofibrous aerogels have been extensively developed as multifunctional substrates in a wide range of fields. Natural silk nanofibrils (SNFs) are an appealing biopolymer due to their natural abundance, mechanical toughness, biodegradability, and excellent biocompatibility. However, fabricating 3D SNF materials with mechanical flexibility remains a challenge. Herein, SNF-based aerogels with controlled structures and well mechanical resilience were prepared. SNFs were extracted from silkworm silks by mechanical disintegration based on an all-aqueous system. The nanofibrils network and hierarchical cellular structure of the aerogels were tuned by the assembly of SNFs and foreign poly(vinyl alcohol) (PVA). The SNF aerogels exhibited an ultralow density (as low as 2.0 mg·cm-3) and well mechanical properties with a structure allowing for large deformations. These SNF aerogels demonstrated a reversible compression and stress retention after 100 cycles of compression. Furthermore, the resulting aerogels were used for air filtration and showed efficient filtration performance with a high dust-holding capacity and low resistance. Moreover, an extremely low thermal conductivity of 0.028 W·(m·K)-1 was achieved by the aerogel, showing its potential for use in heat-retention applications. This study provides a useful strategy for exploring the use of natural silks in 3D aerogels and offers options for developing filtration materials and ultralight heat-retention materials.