Multifunctional hydrogel as a sealant or wound dressing with high adhesiveness and excellent antibacterial activity is highly desirable in clinical applications. In this contribution, one-step synthetic hydrogel based on quaternized chitosan (QCS), tannic acid (TA), and ferric iron (Fe(III)) is developed for skin incision closure and Staphylococcus aureus (S. aureus)-infected wound healing. In this hydrogel system, the ionic bonds and hydrogen bonds between QCS and TA form the main backbone of hydrogel, the metal coordination bonds between TA and Fe(III) (catechol-Fe) endow hydrogel with excellent adhesiveness and (near-infrared light) NIR-responsive photothermal property, and these multiple dynamic physical crosslinks enable QCS/TA/Fe hydrogel with flexible self-healing ability and injectability. Moreover, QCS/TA/Fe hydrogel possesses superior antioxidant, anti-inflammatory, hemostasis, and biocompatibility. Also, it is safe for vital organs. The data from the mouse skin incision model and infected full-thickness skin wound model presented the high wound closure effectiveness and acceleration of the wound healing process by this multifunctional hydrogel, highlighting its great potential in wound management.

One-Step Synthesis of Multifunctional Chitosan Hydrogel for Full-Thickness Wound Closure and Healing.

Recently, research on double-network (DN) hydrogels with good biocompatibility and mechanical properties has been flourishing. The main research directions have aimed to enhance the poor mechanical properties of conventional hydrogels and to broaden their potential applications in various fields. This paper reviews the recent research progress in the preparation of DN hydrogels, including fully chemically cross-linked DN hydrogels, hybrid physically/chemically cross-linked DN hydrogels, and fully physically cross-linked DN hydrogels. These DN hydrogels have significant advantages in mechanical properties, structure, biocompatibility and so on. Focus is placed on the enhancement mechanisms and preparation of different DN hydrogels. Besides, we also discussed the applications of DN hydrogels in drug and biomolecular carriers, flexible sensors and actuators, tissue engineering, medical dressings, ions/pollutant removal, and supercapacitors (SCs). These research advances are rapidly breaking away from the current limitations of DN hydrogels and providing new ideas for their future development.

Research progress on double-network hydrogels

An electroactive scaffold integrated with noninvasive in vivo electrical-stimulation (ES) capability shows great promise in the repair and regeneration of damaged tissues. Developing high-performance piezoelectric biomaterials which can simultaneously serve as both a biodegradable tissue scaffold and controllable electrical stimulator remains a great challenge. Herein, we constructed a biodegradable high-performance 3D piezoelectric scaffold with ultrasound (US)-driven wireless ES capability, and demonstrated its successful application for the repair of spinal cord injuries in a rat model. The 3D multichannel piezoelectric scaffold was prepared by electrospinning of poly(lactic acid) (PLA) nanofibers incorporated with biodegradable high-performance piezoelectric potassium sodium niobate (K0.5Na0.5NbO3, KNN) nanowires. With programmed US irradiation as a remote mechanical stimulus, the on-demand in vivo ES with an adjustable timeline, duration, and strength can be delivered by the 3D piezoelectric scaffold. Under proper US excitation, the 3D tissue scaffolds made of the piezoelectric composite nanofibers can accelerate the recovery of motor functions and enhance the repair of spinal cord injury. The immunohistofluorescence investigation indicated that the 3D piezoelectric scaffolds combined with the US-driven in vivo ES promoted neural stem cell differentiation and endogenous angiogenesis in the lesion. This work highlights the potential application of a biodegradable high-performance piezoelectric scaffold providing US-driven on-demand electrical cues for regenerative medicine.

Wirelessly Powered Electrical-Stimulation Based on Biodegradable 3D Piezoelectric Scaffolds Promotes the Spinal Cord Injury Repair.

Abstract Versatile strategies have been developed to construct electrospun fiber-based drug delivery systems for tissue regeneration and cancer therapy. We first introduce the construction of electrospun fiber scaffolds and their various structures, as well as various commonly used types of drugs. Then, we discuss some representative strategies for controlling drug delivery by electrospun fibers, with specific emphasis on the design of endogenous and external stimuli-responsive drug delivery systems. Afterwards, we summarize the recent progress on controlling drug delivery with electrospun fiber scaffolds for tissue engineering, including soft tissue engineering (such as skin, nerve, and cardiac repair) and hard tissue engineering (such as bone, cartilage, and musculoskeletal systems), as well as for cancer therapy. Furthermore, we provide future development directions and challenges facing the use of electrospun fibers for controlled drug delivery, aiming to provide insights and perspectives for the development of smart drug delivery platforms and improve clinical therapeutic effects in tissue regeneration and cancer therapy. Graphical abstract 

https://link.springer.com/content/pdf/10.1007/s42765-022-00198-9.pdf

Electrospun Fibers Control Drug Delivery for Tissue Regeneration and Cancer Therapy

Ultrasound-driven in vivo electrical stimulation based on biodegradable piezoelectric nanogenerators for enhancing and monitoring the nerve tissue repair

The long-segment peripheral nerve injury (PNI) represents a global medical challenge, leading to incomplete nerve tissue recovery and unsatisfactory functional reconstruction. However, the current electrical stimulation (ES) apparatuses fail perfect nerve repair due to their inability of the variable synchronous self-regulated function with physiological states. It is urgent to develop an implantable ES platform with physiologically adaptive function to provide instantaneous and nerve-preferred ES. Here, a physiologically self-regulated electrical signal is generated by integrating a novel tribo/piezoelectric hybrid nanogenerator with a nanoporous nerve guide conduit to construct a fully implantable neural electrical stimulation (FI-NES) system. The optimal neural ES parameters completely originate from the body itself and are highly self-responsive to different physiological states. The morphological evaluation, representative protein expression level, and functional reconstruction of the regenerated nerves are conducted to assess the PNI recovery process. Evidence shows that the recovery effect of 15 mm length nerve defects under the guidance of the FI-NES system is significantly close to the autograft. The designed FI-NES system provides an effective method for long-term accelerating the recovery of PNI in vivo and is also appropriate for other tissue injury or neurodegenerative diseases.

Physiologically Self-Regulated, Fully Implantable, Battery-Free System for Peripheral Nerve Restoration

Dual network (DN) hydrogels with excellent mechanical strength and controllable component adjustment characteristics have a broad application range in the field of biomedicine. However, the tissue adhesion, skin affinity, self-healing, and antibacterial properties of DN hydrogels are inadequate for their application as skin patches. In this work, we prepared dopamine/zinc oxide (DOPA/ZnO) doped poly(N-hydroxyethyl acrylamide) (p(HEAA))/agar DN hydrogels and combined them to obtain a bilayer hydrogel (two-layer gel) with moisturizing properties. Upon incorporating 0.86 wt% of dopamine (DOPA), the resultant DOPA/p(HEAA))/agar DN hydrogel (DOPA@DNG) exhibited high tensile strain (up to 1600%), excellent self-repair ability, and tissue adhesion. ZnO/p(HEAA))/agar DN hydrogel (ZnO NG) obtained by incorporating 2 w/v ZnO nanoparticles (ZnO NPs) achieved high tensile strength (1.2 MPa), good antibacterial ability, and low charge transfer resistance. Moreover, ZnO NG, which has a tight structure, was employed as a protective layer for the two-layer gel, which can effectively slow down the excessive evaporation of water to protect the DOPA@DNG stability as a skin patch. Evidence showed that the two-layer hydrogel has water retention. Water retention still remains at over 50% after keeping the hydrogel in air for 3 days. These properties mean the two-layer gel based on the DOPA/ZnO doped DN hydrogels could be used as a transdermal patch for numerous applications in drug delivery, wearable devices, and electronic skin.

Dopamine/zinc oxide doped poly(N-hydroxyethyl acrylamide)/agar dual network hydrogel with super self-healing, antibacterial and tissue adhesion functions designed for transdermal patch

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Physiologically Self-Regulated, Fully Implantable, Battery-Free System for Peripheral Nerve Restoration

Dopamine/zinc oxide doped poly(N-hydroxyethyl acrylamide)/agar dual network hydrogel with super self-healing, antibacterial and tissue adhesion functions designed for transdermal patch