Collagen possesses high biocompatibility with all tissue and cell types in the body, enabling the creation of multifunctional composite materials for medical applications. In biomedical engineering, naturally-sourced collagen is often combined with diverse organic and inorganic bioactive components to eliminate defects and disorders in fields including orthopedics, dermatology, and more. At the same time, medical-related infection issues and the precise treatment needs of patients require collagen composite biomaterials to have antibacterial properties and customized structures. This paper reviews the antibacterial functionalization of collagen composite biomaterials in recent years, including the combination with inorganic or organic antibacterial agents, which is beneficial for preventing and controlling biological contamination in medical applications. Then, the existing problems and future development directions for the architecturalization of collagen composite materials with 3D printing were discussed, providing guidance for personalized customization of multifunctional materials to meet the specific needs of patients in the future.Graphical

The increasing global aging population has led to a continual rise in the prevalence of bone and joint diseases, posing challenges to both the quality of life for patients and healthcare resources. Type II collagen, a pivotal protein for sustaining joint function, has gained substantial attention in recent years. The oral administration of undenatured type II collagen (UC-II) has demonstrated noteworthy advancements in tackling bone and joint diseases. This article presents a comprehensive review of the structure and extraction methods of UC-II, discusses the relationship between UC-II and arthritis, and thoroughly examines its therapeutic role and potential mechanisms in the treatment process. In addition, future perspectives for clinical application of UC-II are discussed. It was found that the oral administration of UC-II, through induction of oral tolerance mechanisms, exhibits promise in alleviating joint inflammation and pain in patients with osteoarthritis (OA) and rheumatoid arthritis (RA). This method can significantly ameliorate joint inflammation and pain, with high patient acceptance and minimal side effects, demonstrating its potential as a well-tolerated treatment option for joint diseases.Graphical

Extensive studies demonstrate that macrophage response plays an important role in regulating angiogenesis via a paracrine way, which is crucial for skin wound repair. This study isolated and characterized nanosized exosomes from differently polarized macrophages (MΦ), including M0 (naïve), M1 (pro-inflammatory), and M2 (anti-inflammatory) macrophages, and further assessed their impacts on angiogenesis and skin regeneration. Our results indicated that compared to M0 and M1 counterparts, M2 macrophage-derived exosomes (M2-Exos) exhibited a pronounced ability to promote angiogenic ability of of human umbilical vein endothelial cells (HUVECs) by enhancing expression of angiogenic genes and proteins, increasing cell migration, and improving tubulogenesis. Bioinformatics analyses suggested that the distinct angiogenic potentials of three MΦ-Exos might be attributed to the differentially expressed angiogenesis-related miRNAs and their target genes such as Stat3, Smad 2, and Smad4. Moreover, these isolated MΦ-Exos were integrated with gelatine methacrylate (GelMA) hydrogels to achieve the sustained delivery at murine full-thickness cutaneous wound sites. In vivo results showed that Gel/M2-Exos significantly augmented angiogenesis, accelerated re-epithelialization, promoted collagen maturity, thereby promoting wound healing. In contrary, Gel/M1-Exos showed the opposite effects. Our findings provided compelling evidence that the polarization status of macrophages significantly affected angiogenesis and wound healing via the miRNA cargos of their derived exosomes. Moreover, this study opens a new avenue for developing nano-scale, cell-free exosome-based therapies in treating cutaneous wounds.Graphical abstract

Melamine resin (MR), traditionally synthesized using melamine and formaldehyde, is widely used in the leather industry. However, the emission of free formaldehyde poses a significant challenge for conventional MR. To address the issues of aldehyde in MR, extensive research has been conducted. This paper introduces a novel aldehyde-free MR (LTSL) retanning agent synthesized using cyanuric chloride, l-lysine, and sodium sulfanilate. The chemical structure of LTSL was analyzed via Fourier transform infrared spectroscopy, nuclear magnetic resonance, and X-ray photoelectron spectroscopy. The presence of amino, carboxyl, and sulfonic acid groups in LTSL enhanced its storability and imparted LTSL with an amphoteric character. The isoelectric point of LTSL was optimized to reach 4.37, and LTSL exhibited an appropriate size distribution with an average particle size of 254.17 nm and achieved high absorption rates of 87.77% and 95.84% for retanning and fatliquoring agents, respectively. Consequently, the thickness rate of LTSL reached up to 37%, with no detectable formaldehyde. Notably, LTSL also demonstrated excellent physical and mechanical properties, primarily attributed to the coordination and electrostatic interactions between the chrome-tanned collagen fiber and amino/carboxyl groups in LTSL. This research presents an innovative approach for developing an aldehyde-free MR retanning agent, significantly contributing to the sustainable development of leather manufacturing.Graphical

Proteases, such as trypsin, are essential for extracting collagen in various industrial applications. The potential applications of rare earth nanomaterials, specifically yttrium nanoparticles, have attracted significant interest across various fields due to their distinctive characteristics, including high dielectric constant and thermal stability. Biomineralization has emerged as a promising approach to synthesize protein-inorganic nanomaterials with hierarchical structures and desired functions. In the present investigation, a novel protease-templated biomineralization strategy was developed for synthesizing protease-(NH4)2Y3F11•H2O hybrid nanomaterials using a one-pot method under very mild conditions. For modifying the morphologies of (NH4)2Y3F11•H2O throughout biomineralization, protease has been demonstrated to be a highly promising biotemplate. Protease was utilized as a template for morphological control in the biomineralization procedure, which resulted in a gradual transformation of the initially formed (NH4)2Y3F11•H2O octahedral structures into uniform nanospheres. The applicability of this approach was supported by successfully utilizing various proteases to synthesize protease-(NH4)2Y3F11•H2O hybrid nanospheres. In addition to a strong and desirable luminescent signal, these hybrid nanospheres demonstrated extensive recycling because of their high enzymatic activity, stability and durability. The protease-mediated biomineralization approach offers an easy and robust approach to develop innovative protease-inorganic composites. Its moderate reaction conditions and simple operation render it a viable tool for developing stable and reusable enzyme reactors in various industrial applications.Graphical

Leather dyeing is a critical step in leather manufacturing, as it is responsible for providing leather products with an eye-catching visual aspect and adequate quality properties to meet customers' expectations. This step is becoming more and more challenging as the leather industry advances hand in hand with new environmentally friendly policies and regulations to achieve a safer and healthier planet by replacing the highly polluting Cr-based leather tanning technology with greener alternatives. As a result, achieving high-performance dyeing of organic chrome-free leather is one of the bottlenecks for the sustainable development of the leather industry. Herein, we propose a novel strategy to fabricate an isocyanate-based oligomeric dye (IBD) with high coloring capabilities (component content higher than 62.8%) based on toluene 2,4-diisocyanate and reactive red dye 180. This material has been tested for the dyeing of biomass-derived aldehyde (BDA)-tanned leather with excellent outcomes. The experimental results showed that the crust leather dyed with our novel IBD dyeing agent had higher color fastness and better fullness than the leather dyed with conventional anionic (CAD) or reactive red 180 (RRD-180) dyes. These excellent and promising results open new avenues in manufacturing high-performance organic Cr-free leather products and help to ensure the sustainable transition of the leather industry from Cr-based leather tanning to more sustainable alternatives, maintaining the final quality of the leather products.Graphical abstract

Biodegradability is a crucial indicator to evaluate the sustainability of leather. Herein, a rapid method for biodegradation test in an aqueous medium by measuring biochemical oxygen demand was used to determine the biodegradability of leather from different tanning methods, tanning conditions and process stages. In addition, the difference in biodegradability between leather and leather-like synthetic materials were investigated. Chrome-free tanned leather showed higher degree of biodegradation and faster biodegradation rate than chrome tanned leather. Among them, leathers tanned with biomass-based tanning agents were much easier to biodegrade because the crosslinking network of tanned leather constructed with biomass was more susceptible to microbial attack. The enhancement of tanning effects through changing tanning methods and conditions (such as tanning agent dosage, pH and temperature) resulted in the decline of leather biodegradability. Future development of novel chrome-free tanning technologies should balance between these two aspects. The biodegradability of leather from tanning to post-tanning to finishing showed a stepwise decrease because various chemicals were applied and bound to leather during processing. Even so, finished leather still possessed significantly higher biodegradability compared to leather-like PU and microfiber synthetic materials, demonstrating superior environmental sustainability of natural leather. The results are expected to provide support for the evaluation of the ecological properties of leather and green upgrade of the leather industry.Graphical abstract

The growing interest in valorizing industrial by-products has led researchers to focus on exploring different sources and optimizing collagen extraction conditions over the past decade. While bovine hide, cattle bones, pork, and pig skins remain the most abundant collagen sources, there is a growing trend in the industrial utilization of collagen from non-mammalian species. This review explores alternative marine collagen sources and summarizes emerging trends in collagen recovery from marine sources, with a particular focus on environmentally friendly methods. Additionally, this review covers the colloidal structure-forming properties of marine collagens, including foam, film, gel, and emulsion formation. It also highlights the potential and important applications of marine collagen in various food products. Based on the currently reported marine sources, collagens extracted from fish, jellyfish, and sea cucumbers were found to have the highest yield and mostly comprised type-I collagen, while crustaceans and mollusks yielded lower percentages of collagen. Traditional extraction techniques isolate collagen based on acetic acid and pepsin treatment, but they come with drawbacks such as being time-consuming, causing sample destruction, and using solvents. Conversely, marine collagen extracted using conventional methods assisted with ultrasonication resulted in higher yields and strengthened the triple-stranded helical structures. Recently, an increasing number of new applications have been found in the food industry for marine collagens, such as biodegradable film-forming materials, colloid stabilizers, foaming agents, and micro-encapsulating agents. Furthermore, collagen is a modern foodstuff and is extensively used in the beverage, dairy, and meat industries to increase the stability, consistency, and elasticity of products.Graphical abstract

Reduced graphene oxide (rGO) films suffer from low capacitance for inner unreduced oxygen functional groups, restacking of sheets and high contact resistance. Herein, carbon spheres derived from renewable xylan were added to graphene oxide with large sheet area to fabricate film by gelation and filtration, followed by in situ reduction for high-performance flexible supercapacitor. rGO film with transverse size about 13 μm showed a good specific capacitance of 967 mF/cm2 at a scanning rate of 5 mV/s and increased to 1786 mF/cm2 by in situ reducing its inner part, which generally remained oxidized due to outer hindering from hydrophobic graphene. Then, by hydrothermal carbonization of xylan and activation with KOH, activated carbon sphere (aXCS) was prepared, which had a diameter of 150–200 nm and a specific capacitance of 270 F/g. The aXCS acted as spacer and connector to avoid restacking of graphene sheets and decrease interlayer contact resistance, resulting 94% increase in capacitance performance from rGO film to aXCS/rGO film. Therefore, combined in situ reduction and enhancement through compositing aXCS, the final film (aXCS/rGO-AA) showed a boosted specific capacitance of 755 mF/cm2 at 1 mA/cm2 in double electrode system, power density of 22.5–2250 mW/cm2, and energy density of 11.88–25.2 mWh/cm2. Meanwhile, aXCS/rGO-AA had outstanding cycling stability that its specific capacitance maintained 108.7% after 10,000 cycles of charge–discharge, showing promising potential in wearable and portable electronics.Graphical abstract

Fish scales, considered as low-value by-products, contain peptides and hydroxyapatite that can be applied to produce peptide chelated calcium directly. This study developed a sustainable and one-pot fabrication method for the peptide-chelated calcium from fish scale hydrolysates (FSP-Ca). During pepsin hydrolysis, the releases of peptides (FSP), calcium, and phosphate from fish scales occurred simultaneously, and the chelation was also effectively performed. After a 6-h hydrolysis, the yield of FSP was 46.18%, and the dissolution rate of calcium was 49.53%. Under the optimal conditions (pH 7, chelation time of 25 min, and chelation temperature of 48 °C), a high chelation rate of 86.16% was obtained, with a calcium content of 81.8 mg/g. The results of UV absorption, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the successful chelation between FSP and calcium derived from fish scales. The –NH2, –COO–, N–H, C=O, C–H, and –OH groups in FSP participated in the formation of FSP-Ca.Graphical