Silk-based conductive materials for smart biointerfaces

Bio-Functionalized MXenes: Synthesis and Versatile Applications

MXenes exhibit remarkable properties, including high electrical conductivity, tunable surface chemistry, outstanding mechanical strength, and notable hydrophilicity. Recent advancements in bio-functionalization have further enhanced these intrinsic characteristics, unlocking unprecedented opportunities for MXenes across a wide spectrum of applications in both biomedical and environmental domains. This review provides an in-depth analysis of the synthesis strategies and functionalization techniques that improve MXenes' biocompatibility and expand their potential uses in cutting-edge applications, including implantable and wearable devices, drug delivery systems, cancer therapies, tissue engineering, and advanced sensing technologies. Moreover, the review explores the utility of bio-functionalized MXenes in areas such as corrosion protection, water purification, and food safety sensors, underscoring their versatility in addressing urgent global challenges. By conducting a critical evaluation of current research, this review not only highlights the immense potential of bio-functionalized MXenes but also identifies pivotal gaps in the literature, offering clear pathways for future exploration and innovation in this rapidly evolving field.

Functional Hydrogel Interfaces for Cartilage and Bone Regeneration

Effective treatment of bone diseases is quite tricky due to the unique nature of bone tissue and the complexity of the bone repair process. In combination with biological materials, cells and biological factors can provide a highly effective and safe treatment strategy for bone repair and regeneration, especially based on these multifunctional hydrogel interface materials. However, itis still a challenge to formulate hydrogel materials with fascinating properties (e.g., biological activity, controllable biodegradability, mechanical strength, excellent cell/tissue adhesion, and controllable release properties) for their clinical applications in complex bone repair processes. In this review, we will highlight recent advances in developing functional interface hydrogels. We then discuss the barriers to  producing of functional hydrogel materials without sacrificing their inherent properties, and potential applications in cartilage and bone repair are discussed. Multifunctional hydrogel interface materials can serve as a fundamental building block for bone tissue engineering.

Polymeric silk fibroin hydrogel as a conductive and multifunctional adhesive for durable skin and epidermal electronics

Silk fibroin (SF)-based hydrogels are promising multifunctional adhesive candidates for real-world applications in tissue engineering, implantable bioelectronics, artificial muscles, and artificial skin. However, developing conductive SF-based hydrogels that are suitable for the micro-physiological environment and maintain their physical and chemical properties over long periods of use remains challenging. Herein, we developed an ion-conductive SF hydrogel composed of glycidyl methacrylate silk fibroin (SilMA) and bioionic liquid choline acylate (ChoA) polymer chains, together with the modification of acrylated thymine (ThyA) and adenine (AdeA) functional groups. The resulting polymeric ion-conductive SF composite hydrogel demonstrated high bioactivity, strong adhesion strength, good mechanical compliance, and stretchability. The formed hydrogel network of ChoA chains can coordinate with the ionic strength in the micro-physiological environment while maintaining the adaptive coefficient of expansion and stable mechanical properties. These features help to form a stable ion-conducting channel for the hydrogel. Additionally, the hydrogel network modified with AdeA and ThyA, can provide a strong adhesion to the surface of a variety of substrates, including wet tissue through abundant hydrogen bonding. The biocompatible and ionic conductive SF composite hydrogels can be easily prepared and incorporated into flexible skin or epidermal sensing devices. Therefore, our polymeric SF-based hydrogel has great potential and wide application to be an important component of many flexible electronic devices for personalized healthcare.

Electroactive Biomaterials Regulate the Electrophysiological Microenvironment to Promote Bone and Cartilage Tissue Regeneration

The incidence of large bone and articular cartilage defects caused by traumatic injury is increasing worldwide; the tissue regeneration process for these injuries is lengthy due to limited self‐healing ability. Endogenous bioelectrical phenomenon has been well recognized to play an important role in bone and cartilage homeostasis and regeneration. Studies have reported that electrical stimulation (ES) can effectively regulate various biological processes and holds promise as an external intervention to enhance the synthesis of the extracellular matrix, thereby accelerating the process of bone and cartilage regeneration. Hence, electroactive biomaterials have been considered a biomimetic approach to ensure functional recovery by integrating various physiological signals, including electrical, biochemical, and mechanical signals. This review will discuss the role of endogenous bioelectricity in bone and cartilage tissue, as well as the effects of ES on cellular behaviors. Then, recent advances in electroactive materials and their applications in bone and cartilage tissue regeneration are systematically overviewed, with a focus on their advantages and disadvantages as tissue repair materials and performances in the modulation of cell fate. Finally, the significance of mimicking the electrophysiological microenvironment of target tissue is emphasized and future development challenges of electroactive biomaterials for bone and cartilage repair strategies are proposed.

The Emerging Role of Silk Fibroin for the Development of Novel Drug Delivery Systems

In order to reduce the toxicological impact on healthy cells and to improve the therapeutic response, many drug delivery systems have been fabricated and analysed, involving the use of different natural and synthetic materials at macro-, micro- and nanoscales. Among the natural materials which have demonstrated a huge potential for the development of effective drug delivery systems, silk fibroin has emerged for its excellent biological properties and for the possibility to be processed in a wide range of forms, which can be compliant with multiple active molecules and pharmaceutical ingredients for the treatment of various diseases. This review aims at presenting silk fibroin as an interesting biopolymer for applications in drug delivery systems, exploring the results obtained in recent works in terms of technological progress and effectiveness in vitro and in vivo.

Electrospun fiber-based immune engineering in regenerative medicine

Immune engineering, a burgeoning field within regenerative medicine, involves a spectrum of strategies to optimize the intricate interplay between tissue regenerative biomaterials and the host tissue. These strategies are applied across different types of biomaterials and various disease models, which encompasses finely modulating the immune response at the levels of immune cells and factors, aiming to mitigate adverse effects like fibrosis and persistent inflammation that may arise at the injury site and consequently promote tissue regeneration. With the continuous progress in electrospinning technology, the immunoregulatory capabilities of electrospun fibers have gained substantial attention over the years. Electrospun fibers, with their extracellular matrix-like characteristics, high surface-area-to-volume ratio, and reliable pharmaceutical compound capacity, have emerged as key players among tissue engineering materials. This review specifically focuses on the role of electrospun fiber-based immune engineering, emphasizing their unique design strategies. Notably, electrospinning actively engages in immune engineering by modulating immune responses through four essential strategies: (i) surface modification, (ii) drug loading, (iii) physicochemical parameters, and (iv) biological grafting. This review presents a comprehensive overview of the intricate mechanisms of the immune system in injured tissues while unveiling the key strategies adopted by electrospun fibers to orchestrate immune regulation. Furthermore, the review explores the current developmental trends and limitations concerning the immunoregulatory function of electrospun fibers, aiming to drive the advancements in electrospun fiber-based immune engineering to its full potential.

Electrogelated drug-embedded silk/gelatin/rGO degradable electrode for anti-inflammatory applications in brain-implant systems

Implantable electrodes have raised great interest over the last years with the increasing incidence of neurodegenerative disorders. For brain implant devices, some key factors resulting in the formation of glial scars, such as mechanical mismatch and acute injury-induced inflammation, should be considered for material design. Therefore, in this study, a new biocompatible flexible electrode (e-SgG) with arbitrary shapes on a positive electrode was developed via electrogelation by applying a direct electrical voltage on a silk fibroin/gelatin/reduced graphene oxide composite hydrogel. The implantable flexible e-SgG-2 film with 1.23% rGO content showed high Young's modulus (11-150 MPa), which was sufficient for penetration under dried conditions but subsequently became a biomimetic brain tissue with low Young's modulus (50-3200 kPa) after insertion in the brain. At the same time, an anti-inflammatory drug (DEX) incorporated into the e-SgG-2 film can be electrically stimulated to exhibit two-stage release to overcome tissue inflammation during cyclic voltammetry via degradation by applying an AC field. The results of cell response to the SF/gelatin/rGO/DEX composite film showed that the released DEX could interrupt astrocyte growth to reduce the inflammatory response but showed non-toxicity toward neurons, which demonstrated a great potential for the application of the biocompatible and degradable e-SgG-D electrodes in the improvement of nerve tissue repair.

Functional adhesive hydrogels for biological interfaces

Hydrogel adhesives are extensively employed in biological interfaces such as epidermal flexible electronics, tissue engineering, and implanted device. The development of functional hydrogel adhesives is a critical, yet challenging task since combining two or more attributes that seem incompatible into one adhesive hydrogel without sacrificing the hydrogel's pristine capabilities. In this Review, we highlight current developments in the fabrication of functional adhesive hydrogels, which are suitable for a variety of application scenarios, particularly those that occur underwater or on tissue/organ surface conditions. The design strategies for a multifunctional adhesive hydrogel with desirable properties including underwater adhesion, self-healing, good biocompatibility, electrical conductivity, and anti-swelling are discussed comprehensively. We then discuss the challenges faced by adhesive hydrogels, as well as their potential applications in biological interfaces. Adhesive hydrogels are the star building blocks of bio-interface materials for individualized healthcare and other bioengineering areas.