Adhesive and biodegradable membranes made of sustainable catechol-functionalized marine collagen and chitosan

Mussel-inspired chitosan and its applications in the biomedical field

Chitosan (CS) has physicochemical properties including solubility, crystallinity, swellability, viscosity, and cohesion, along with biological properties like biocompatibility, biodegradation, antioxidant, antibacterial, and antitumor effects. However, these characteristics of CS are greatly affected by its degree of deacetylation, molecular weight, pH and other factors, which limits the application of CS in biomedicine. The modification of CS with catechol-containing substances inspired by mussels can not only improve these properties of CS, but also endow it with self-healing property, providing an environmentally friendly and sustainable way to promote the application of CS in biomedicine. In this paper, the properties of CS and its limitation in the biomedical filed are introduced in detail. Then, the modification methods and properties of substances with catechol groups inspired by mussels on CS are reviewed. Finally, the applications of modified CS in the biomedical field of wound healing, drug delivery, anticancer therapy, biosensor and 3D printing are further discussed. This review can provide valuable information for the design and exploitation of mussel-inspired CS in the biomedical field.

Antibacterial properties of photo-crosslinked chitosan/methacrylated hyaluronic acid nanoparticles loaded with bacitracin

The current treatments for wounds often fail to induce adequate healing, leaving wounds vulnerable to persistent infections and development of drug-resistant microbial biofilms. New natural-derived nanoparticles were studied to impair bacteria colonization and hinder the formation of biofilms in wounds. The nanoparticles were fabricated through polyelectrolyte complexation of chitosan (CS, polycation) and hyaluronic acid (HA, polyanion). UV-induced photo-crosslinking was used to enhance the stability of the nanoparticles. To achieve this, HA was methacrylated (HAMA, degree of modification of 20 %). Photo-crosslinked nanoparticles obtained from HAMA and CS had a diameter of 478 nm and a more homogeneous size distribution than nanoparticles assembled solely through complexation (742 nm). The nanoparticles were loaded with the antimicrobial agent bacitracin (BC), resulting in nanoparticles with a diameter of 332 nm. The encapsulation of BC was highly efficient (97 %). The BC-loaded nanoparticles showed significant antibacterial activity against gram-positive bacteria Staphylococcus aureus, Methicillin-resistant S. aureus and S. epidermidis. Photo-crosslinked HAMA/CS nanoparticles loaded with BC demonstrated inhibition of biofilm formation and a positive effect on the proliferation of mammalian cells (L929). These crosslinked nanoparticles have potential for the long-term treatment of wounds and controlled antibiotic delivery at the location of a lesion.

Bioadhesive Hyaluronic Acid-Based Hydrogels for Spinal Cord Injury

Spinal cord injuries (SCI) have devastating physical, psychological, and psychosocial consequences for patients. One challenge of nerve tissue repair is the lack of a natural extracellular matrix (ECM) that guides the regenerating axons. Hyaluronic acid (HA) is a major ECM component and plays a fundamental role in facilitating lesion healing. Herein, we developed HA-based adhesive hydrogels by modification of HA with dopamine, a mussel-inspired compound with excellent adhesive properties in an aqueous environment. The hydrogels were loaded with the anti-inflammatory drug ibuprofen and the response of neuronal cells (SH-SY5Y) was evaluated in terms of viability, morphology, and adhesion. The obtained results suggested that the developed materials can bridge lesion gaps, guide axonal growth, and simultaneously act as a vehicle for the delivery of bioactive compounds.

Mechanically tunable, antibacterial and bioactive mussel adhesive protein/hyaluronic acid coacervates as bioadhesives

In this work a bioadhesive was developed based on coacervates composed of recombinant mussel adhesive protein (MAP) and dopamine grafted hyaluronic acid (HA). Dopamine profoundly affected rheological attributes of the coacervates, leading to reduced rigidity, enhanced chain flexibility, more sol-like and fluid character and higher tolerance against structural collapse. The coacervates were rendered flowability, injectability, and adaptability, benefiting convenient delivery and making good contact with the skin to provide firm sealing for wounds of various shape and depth. It is the first time reported that MAP/HA coacervates are inherently antibacterial with 100 % growth inhibition against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli. The antibacterial capability was disclosed to be positively related to catechol content. To further enhance the coacervates bioactivity, a small bioactive peptide thymosin was added and was revealed to promote fibroblasts migration. The coacervates hold great potential as practical bioadhesives both from the perspective of rheological properties and biological activities.

Two-Layered Biomimetic Flexible Self-Powered Electrical Stimulator for Promoting Wound Healing

The repair of wound damage has been a common problem in clinic for a long time. Inspired by the electroactive nature of tissues and the electrical stimulation of wounds in clinical practice, the next generation of wound therapy with self-powered electrical stimulator is expected to achieve the desired therapeutic effect. In this work, a two-layered self-powered electrical-stimulator-based wound dressing (SEWD) was designed through the on-demand integration of the bionic tree-like piezoelectric nanofiber and the adhesive hydrogel with biomimetic electrical activity. SEWD has good mechanical properties, adhesion properties, self-powered properties, high sensitivity, and biocompatibility. The interface between the two layers was well integrated and relatively independent. Herein, the piezoelectric nanofibers were prepared by P(VDF-TrFE) electrospinning, and the morphology of the nanofibers was controlled by adjusting the electrical conductivity of the electrospinning solution. Benefiting from its bionic dendritic structure, the prepared piezoelectric nanofibers had better mechanical properties and piezoelectric sensitivity than native P(VDF-TrFE) nanofibers, which can convert tiny forces into electrical signals as a power source for tissue repair. At the same time, the designed conductive adhesive hydrogel was inspired by the adhesive properties of natural mussels and the redox electron pairs formed by catechol and metal ions. It has bionic electrical activity matching with the tissue and can conduct the electrical signal generated by the piezoelectric effect to the wound site so as to facilitate the electrical stimulation treatment of tissue repair. In addition, in vitro and in vivo experiments demonstrated that SEWD converts mechanical energy into electricity to stimulate cell proliferation and wound healing. The proposed healing strategy for the effective treatment of skin injury was provided by developing self-powered wound dressing, which is of great significance to the rapid, safe, and effective promotion of wound healing.

Accelerating bone regeneration using poly(lactic-co-glycolic acid)/hydroxyapatite scaffolds containing duck feet-derived collagen

Collagen, with low antigenicity and excellent cell adhesion, is a biomaterial mainly used for regenerating bone, cartilage, and skin, owing to its biocompatibility and biodegradability. Results from a previous study confirmed that a scaffold mixed with duck feet-derived collagen (DC) and Poly(lactic-co-glycolic acid) (PLGA) reduced inflammatory reaction and increased bone regeneration. To develop an optimal bone substitute we included hydroxyapatite (HAp), a key osteoconductive material, in a DC and PLGA mixture. We fabricated 0, 10, 20, 40, 60, and 80 wt% DC/PLGA/HAp scaffolds and studied their potential for bone tissue engineering. Characteristic analysis of the scaffold and seeding of rabbit bone marrow mesenchymal stem cells (rBMSCs) on the scaffold were conducted to investigate cell proliferation, osteogenic differentiation, and bone formation. We confirmed that increasing DC concentration not only improved the compressive strength of the DC/PLGA/HAp scaffold but also cell proliferation and osteogenic differentiation. It was found through comparison with previous studies that including HAp in the scaffold also promotes osteogenic differentiation. Our study thus shows through in vivo results that the 80 wt% DC/PLGA/HAp scaffold promotes bone mineralization and collagen deposition while reducing the inflammatory response. Hence, 80 wt% DC/PLGA/HAp has excellent potential as a biomaterial for bone regeneration applications.

Novel polycaprolactone (PCL)-type I collagen core-shell electrospun nanofibers for wound healing applications

Type I collagen (Col_1) is one of the main proteins present in the skin extracellular matrix, serving as support for skin regeneration and maturation in its granulation stage. Electrospun materials have been intensively studied as the next generation of skin wound dressing mainly due to their high surface area and fibrous porosity. However, the electrospinning of collagen-based solutions causes degradation of its structure. In this work, a coaxial electrospinning process was proposed to overcome this limitation. The production of mats of polycaprolactone (PCL)-Col_1/PVA (collagen/poly(vinyl alcohol)) composed of core-shell nanofibers was investigated. PCL solution was used as the core solution, while Col_1/PVA was used as the shell solution. PVA was used to improve the processability of collagen, while PCL was employed to improve the mechanical properties and morphology of Col_1/PVA fibers. The morphology and the cytotoxicity of the fibers were highly dependent on the processing parameters. Defect-free core-shell nanofibers were obtained with a shell/core flow rates ratio = 4, flight distance of 12 cm, and an applied voltage of 16 kV. Using this strategy, the triple helix structure characteristic of the collagen molecule was preserved. Moreover, the common post-processing of solvent removal could be suppressed, simplifying the manufacturing processing of these biomaterials. The nanostructured mats showed no cytotoxicity, high liquid absorption, structural stability, hydrophilic character, and collagen release capacity, making them a potential novel dressing for skin damage regeneration, in special in the case of chronic wounds treatment, in which exogenous collagen delivery is necessary.

Mussel-Inspired Lego Approach for Controlling the Wettability of Surfaces with Colorless Coatings

The control of surface wettability with polyphenol coatings has been at the forefront of materials research since the late 1990s, when robust underwater adhesion was linked to the presence of L-DOPA-a catecholic amino acid-in unusually high amounts, in the sequences of several mussel foot proteins. Since then, several successful approaches have been reported, although a common undesired feature of most of them is the presence of a remnant color and/or the intrinsic difficulty in fine-tuning and controlling the hydrophobic character. We report here a new family of functional catechol-based coatings, grounded in the oxidative condensation of readily available pyrocatechol and thiol-capped functional moieties. The presence of at least two additional thiol groups in their structure allows for polymerization through the formation of disulfide bonds. The synthetic flexibility, together with its modular character, allowed us to: (I) develop coatings with applications exemplified by textiles for oil-spill water treatment; (II) develop multifunctional coatings, and (III) fine-tune the WCA for flat and textile surfaces. All of this was achieved with the application of colorless coatings.

Expression, characterization, and application potentiality evaluation of recombinant human-like collagen in Pichia pastoris

Collagen is a biofunctional protein that has been widely used in many fields, including but not limited to biomedical, cosmetics and skin care, food, and novel materials. Recombinant collagen has great potential as an alternative to collagen extracted from animals because it avoids the immune response, and the yield and properties are stable. However, challenges remain in the industrial application of recombinant collagen, including improving the expression yield, reducing the cost of purification for industry and expanding applications. In this study, a cloning and recombination method was used to heterologously express the recombinant human-like collagen (RHLC) in Pichia pastoris GS115 using the pPIC9k expression vector. The RHLC expression titre was 2.33 g/L via a 5-L fermenter, and the purification was completed within 48 h and was 98% pure. The characteristics of RHLC were investigated. Furthermore, potential applications for RHLC were explored, such as basal collagen sponge preparation, forming films with chitosan and production of collagen hydrolysed peptides. RHLC has various potential applications due to its triple helical structure, thermostability, good biocompatibility and film-forming ability.

Collagen-based hydrogels cross-linked via laccase - mediated system incorporated with Fe3+ for wound dressing

Pure fish skin collagen hydrogels as a wound dressing have lower thermodynamic stability than mammalian collagen and usually suffer from poor mechanical properties, weak degradation resistance and insufficient functionalities such as antioxidant and anti-inflammatory properties to meet clinical needs that limit its further application. Here, a silver carp skin collagen hydrogel is successfully constructed via the cross-linking of the laccase-protocatechuic aldehyde (LAC-PAL) and the structure of the hydrogel is further consolidated and strengthened by the interaction of PAL and Fe3+. In this collagen hydrogel system, Fe3+, acting as a second cross-linker, consolidates and enhances the stability of the hydrogel after LAC-PAL cross-linking. This cross-linking method improves the resistance to degradation with a reduction in its degradation rate from 89.45% to 38.66% and endows the hydrogel with antioxidant activity. The in vitro data show that the hydrogel promotes cell proliferation and adhesion exhibiting good biocompatibility. Animal experiments show that the hydrogel contributes to angiogenesis and improves inflammatory response in the early stages of wound healing, resulting in promoting wound healing. Altogether, this newly developed collagen hydrogel is expected to be applied in wound repair as a wound dressing.

Origin of critical nature and stability enhancement in collagen matrix based biomaterials: Comprehensive modification technologies

Collagen is the most abundant protein in animals and one of the most important extracellular matrices that chronically plays an important role in biomaterials. However, the major concern about native collagen is the lack of its thermal stability and weak resistance to proteolytic degradation. Currently, a series of modification technologies have been explored for critical nature and stability enhancement in collagen matrix-based biomaterials, and prosperously large-scale progress has been achieved. The establishment of covalent bonds among collagen noumenon has been verified assuringly to have pregnant influences on its physicochemical properties and biological properties, enlightening to discuss the disparate modification technologies on specific effects on the multihierarchical structures and pivotal performances of collagen. In this review, various existing modification methods were classified from a new perspective, scilicet whether to introduce exogenous substances, to reveal the basic scientific theories of collagen modification. Understanding the role of modification technologies in the enhancement of collagen performance is crucial for developing novel collagen-based biomaterials. Moreover, the different modification effects caused by the interaction sites between the modifier and collagen, and the structure-activity relationship between the structure of the modifier and the properties of collagen were reviewed.

Biodegradable Polymer Composites for Electrophysiological Signal Sensing

Electrophysiological signals are collected to characterize human health and applied in various fields, such as medicine, engineering, and pharmaceuticals. Studies of electrophysiological signals have focused on accurate signal acquisition, real-time monitoring, and signal interpretation. Furthermore, the development of electronic devices consisting of biodegradable and biocompatible materials has been attracting attention over the last decade. In this regard, this review presents a timely overview of electrophysiological signals collected with biodegradable polymer electrodes. Candidate polymers that can constitute biodegradable polymer electrodes are systemically classified by their essential properties for collecting electrophysiological signals. Moreover, electrophysiological signals, such as electrocardiograms, electromyograms, and electroencephalograms subdivided with human organs, are discussed. In addition, the evaluation of the biodegradability of various electrodes with an electrophysiology signal collection purpose is comprehensively revisited.

Tissue Adhesive, Self-Healing, Biocompatible, Hemostasis, and Antibacterial Properties of Fungal-Derived Carboxymethyl Chitosan-Polydopamine Hydrogels

In this work, fungal mushroom-derived carboxymethyl chitosan-polydopamine hydrogels (FCMCS-PDA) with multifunctionality (tissue adhesive, hemostasis, self-healing, and antibacterial properties) were developed for wound dressing applications. The hydrogel is obtained through dynamic Schiff base cross-linking and hydrogen bonds between FCMCS-PDA and covalently cross-linked polyacrylamide (PAM) networks. The FCMCS-PDA-PAM hydrogels have a good swelling ratio, biodegradable properties, excellent mechanical properties, and a highly interconnected porous structure with PDA microfibrils. Interestingly, the PDA microfibrils were formed along with FCMCS fibers in the hydrogel networks, which has a high impact on the biological performance of hydrogels. The maximum adhesion strength of the hydrogel to porcine skin was achieved at about 29.6 ± 2.9 kPa. The hydrogel had good self-healing and recoverable properties. The PDA-containing hydrogels show good antibacterial properties on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. Moreover, the adhesive hydrogels depicted good viability and attachment of skin fibroblasts and keratinocyte cells. Importantly, FCMCS and PDA combined resulted in fast blood coagulation within 60 s. Hence, the adhesive hydrogel with multifunctionality has excellent potential as a wound dressing material for infected wounds.