Protease-assisted soaking has received increasing attention in recent years. However, few reports have elaborated on the effect of bactericides, which are used to protect raw hides from microbial damage in the soaking process, on the performance of protease-assisted soaking. Here we investigate the effects of three bactericides, namely, 2-methyl-4-isothiazolin-3-one (MIT), sodium propyl 4-hydroxybenzoate (SPHB) and cetyl trimethyl ammonium bromide (CTAB), on the catalytic activity of protease. MIT and SPHB have little effect on the proteolytic activity, whilst CTAB has a negative effect. Fluorescence spectroscopy, synchronous fluorescence spectroscopy, molecular docking and molecular dynamics simulation were used to analyse the bactericide–protease interaction. The data reveal that MIT and SPHB are bound to the non-catalytic sites of protease, whilst CTAB affects the catalytic triad of protease. Furthermore, the protease and bactericides were used alone, simultaneously and sequentially in the soaking process, and their soaking performances were evaluated. The evaluation shows that the use of protease increases the microorganisms in the soaking float, and MIT exhibits the best bactericidal effect. The simultaneous use of protease and MIT effectively inhibits bacteria and scarcely affects the removal of unstructured proteins from hides and the attack on epidermis by protease. These findings contribute to a better understanding of the scientific use of protease with other auxiliaries in soaking.

Oral diseases have emerged as one of the leading public health challenges globally. Although the existing clinical modalities for restoration of dental tissue loss and craniomaxillofacial injuries can achieve satisfactory therapeutic results, they cannot fully restore the original complex anatomical structure and physiological function of the tissue. 3D printing of biological tissues has gained growing interest in the field of oral medicine with the ability to control the bioink component and printing structure for spatially heterogeneous repairing constructs, holding enormous promise for the precise treatment of oral disease. Particularly, collagen-based materials have been recognized as promising biogenic bioinks for the regeneration of several tissues with high cell-activating and biocompatible properties. In this review, we summarize 3D printing methods for collagen-based biomaterials and their mechanisms. Additionally, we highlight the animal sources of collagen and their characteristics, as well as the methods of collagen extraction. Furthermore, this review provides an overview of the 3D bioprinting technology for the regeneration of the pulpal nerve and blood vessels, cartilage, and periodontal tissue. We envision that this technique opens up immense opportunities over the conventional ones, with high replicability and customized function, which can ultimately promote effective oral tissue regeneration.

Antioxidant collagen hydrolysates refers to the peptides mixture with antioxidant properties identified from hydrolyzed collagen. Due to its specific structural, biological and physicochemical properties, collagen hydrolysates have been explored as a multifunctional antioxidant in the biomedical field. In this review, we summarize recent advances in antioxidant collagen hydrolysates development. Initially, the preparation process of antioxidant collagen hydrolysates is introduced, including the production and separation methods. Then the effects and the mechanisms of amino acid composition and collagen peptide structure on the antioxidant activity of collagen hydrolysates are reviewed. Finally, the applications of antioxidant collagen hydrolysates in biomedical domains are summarized, with critical discussions about the advantages, current limitations and challenges to be resolved in the future.

The utilization of chelation reaction between metals and tannins is a common tanning method in leather chemistry. Herein, a novel combination tanning mechanism inspired environmentally benign catalyst (CMBT-Fe⁰) was synthesized by immobilizing Fe nanoparticles onto bayberry tannin (BT) grafted chitosan microfibers (CM). The obtained catalyst featured a well-defined microfibrous structure, on which Fe⁰ nanoparticles were highly dispersed to exhibit exceptional catalytic activity for the degradation of tetracycline (TC). The catalytic activity of CMBT-Fe⁰ was 1.72 times higher than that of the commercial Fe⁰ nanoparticles without immobilization, with 95.03% of TC degraded within 90.0 min. The CMBT-Fe⁰ catalysts were recycled 6 times, with the removal rate of TC maintained at 82.56%. Furthermore, a possible mechanism responsible for the catalytic removal of TC was provided by analyzing the catalytic degradation products via liquid chromatography-mass spectrometry. Therefore, our investigation successfully developed efficient catalysts to address the concerned environmental issue of antibiotic pollution.

As a highly complex aqueous effluent, tannery wastewater from leather industry should be treated appropriately before discharging into the environment. Membrane technology has been shown to be a promising approach for tannery wastewater treatment as it may achieve “Zero Liquid Discharge (ZLD)”. This work, as the state-of-the-art, attempts to review the world-wide research trends of membrane technologies, the technical recapitulation and recent advances of such technology for tannery wastewater treatment. Generally, manufacture membrane, membrane-based integrated process, MBR, NF, UF and RO are the hotspots in this field. Details of different membrane technologies configured for tannery wastewater treatment, such as membrane materials, scale, membrane modules, operating conditions and removal efficiency of pollutants, are also summarized. It should be noted that membrane fouling is still a major challenge in the membrane technology during tannery wastewater treatment. Therefore, process coupling, either within diverse membrane technologies or between membrane and non-membrane technologies, is considered as a promising alternative to treat the leather tannery wastewater in the future.

The deodorizer distillate (DD) is a byproduct of vegetable oil processing industry and is rich in functional bioactive components. This study aimed to employ phosphorylation modification for DD to produce a new sustainable fatliquor. The bioactive ingredients in DD, namely fatty acids, sterols, and tocopherols, were determined by using HPLC and GLC. The results revealed that the DD sample contained a high percentage of unsaturated fatty acids (72.3%) and high levels of γ and δ-tocopherols (54.8% and 31.60%, respectively). Mechanical parameters (tensile strength, elongation at break, and tear strength) of leather were improved after being treated with the prepared fatliquor emulsion. Eventually, SEM showed that the texture of the fatliquored leather had been remarkably enhanced. Moreover, the fatliquored leather possessed effective antibacterial effect against the specified +ve, −ve bacteria, and Candida albicans microorganisms. The strength, fullness, soft handle, and elasticity of leather were all improved, and the grain of leather was protected from becoming loose after drying.

Collagen with a multi-hierarchical architecture exhibits powerful biological performance, thus being developed in biomedical applications as a processing building block. The isolated collagen after extraction from biological tissues can be processed into various forms such as fibrils, scaffolds, membranes, microspheres, hydrogels, and sponges for further use in specific applications. This review briefly discusses the multi-hierarchical structure, powerful biological performances, extraction, and processing approaches of collagen as a natural biomaterial. The processing of collagen including dissolution, self-assembly, cross-linking, and electrospinning, is discussed to show more feasibility for specific applications of collagen composite biomaterials. Further emphasis is directed towards the biomedical applications of drug and gene delivery, as well as tissue repair involving bone, cartilage, vascular, and corneal, along with wound healing. Additionally, there is a focus on the development of flexible sensors and electronic skins (e-skins). Furthermore, the potential challenges and perspectives for the development of collagen-based biomaterials are proposed. In short, collagen-based biomaterials are expected to facilitate sustainable development and the next generation of advanced biomaterial applications.

Flexible strain sensors are capable to detect external force induced strain change owing to their unique ability to convert deformation into electrical signals. Generally, micro/nano patterning of conductive layer in strain sensor is an effective method to improve its sensitivity, however the sophisticated manipulation process is limited only in laboratory scale. In this report, a simple and scalable fabrication strategy was used to create micro-cracking conductive layer as an alternative patterning method to achieve high performance of strain sensor. In details, the sensor was fabricated using leather as the substrate to filtrated acidified multi-walled carbon nanotubes (a-MWCNTs)/layered double hydroxides (LDHs) suspension. During stretching process, micro-cracking structure emerged on the percolated a-MWCNTs/LDHs layer, causing a rise up of resistance according to increasing strain and generated a detectable electrical signal. The prepared sensor had a large detecting range (60%), high sensitivity (GF of 7238.92 at strain 30–60%), fast response (tensile response time of 270 ms), good stability and repeatability. The sensor also inherited the advantages of leather, such as biodegradability and good air permeability, and the introduction of a-MWCNTs/LDHs further enhanced its fire retardancy properties. These features ensured the sensor as an eco-friendly, comfortable and safe electronic device for human motion detection.

Biomass-based membranes have attracted increasing attentions due to their cheap and sustainable advantages. In this work, a novel thin-film composite (TFC) nanofiltration (NF) membrane was fabricated through a facial interfacial polymerization (IP) process by initiate the crosslinking reaction between collagen fibers (CFs) and tannic acid (TA). The increased TA concentrations endowed the TFC membrane with a higher crosslinking degree, a thicker active layer and a rougher top surface. At optimized condition with 0.60 mg TA decoration, the TFC-3 membrane exhibited a high water permeability of 23.49 L m⁻² h⁻¹ bar⁻¹ with high rejections above 98.0% for congo red, reactive blue 19, coomassie blue G-250, and methyl blue. Furthermore, the membrane preserved remarkable salt retentions (93.3% for Na₂SO₄, 83.4% for MgSO₄, 36.2% for MgCl₂, and 26.4% for NaCl) and satisfying operation stability. This facial fabrication method offered a new insight to employ biomass for molecular precise separation.

This study aimed to identify and classify the type of plants used for tanning historical leathers using cost-effective Fourier transform infrared (FTIR) spectroscopy. The investigation was carried out on five plants (oak bark, sumac, valonia, tara, and gallnut) and four historical leather samples from book bindings dating back to the Qajar period. Tannin extraction from both plants and leathers was performed using acetone–water solvent, and the samples were then subjected to FTIR spectroscopy. Pre-processing of the spectra included baseline correction, smoothing, and normalization. Principal component analysis (PCA) was used to identify the source of tannins based on FTIR results. FTIR was found to provide a good separation of condensed tannins from hydrolysable ones. However, PCA analysis allowed for the separation and identification of the type of plant used for tannin extraction. The examination of historical leather samples revealed that the primary classification based on the type of tannin is possible, but accurate identification faces challenges due to structural changes and degradation over time.

The skin plays a fundamental role in regulating the body’s internal balance and protecting against external traumas. A broad variety of environmental risk factors frequently result in acute skin wounds, whose inappropriate treatments would lead to chronic skin wounds that are difficult to heal. Traditional dressings have been widely used to repair chronic skin wounds, however their drawbacks such as insufficient hemostatic efficacy and non-moist environment have severely limited their clinical applications. As the principal component of skin, collagen has always been a research hotspot in the field of chronic skin wounds due to its advantages of low antigenicity, high biocompatibility and superior bioactivity. Collagen-based dressings have been increasingly developed to heal the chronic wounds during the past decades, arising from their capability in decreasing protein and electrolyte losses in wound exudate, preventing bacterial contamination, permitting less painful dressing changes, and improving the healing quality. This review overviews recent progress of collagen dressings for chronic skin wound healing. Various commonly used wound dressings for wound management have been first introduced. Collagen wound dressings have been categorized as films, sponges, hydrogels, nanofibers, and powders, and their efficacy has been compared. The critical functions of collagen dressings in wound healing, such as stopping bleeding, shortening inflammation, promoting angiogenesis, and stimulating tissue regeneration have been elaborated. The clinical applications of collagen dressings to repair different types of chronic wounds have been thoroughly summarized. A comprehensive list of commercialized collagen dressings has been updated, and an outlook of collagen dressings have been finally speculated.

With the efficient cross-linking abilities and the flexible regulation abilities to the performances of cross-linked products, the multi-functional aliphatic epoxides were once widely used to cross-link the collagen-based materials in the last century. In present work, the multi-functional epoxides were used to construct and cross-link collagen sponges for tissue engineering scaffolds, which was hoped to board the theoretical system of epoxides and explore their potentials for modern applications. The bi- to tetra-functional epoxides were used to cross-link collagen solutions and establish the gel-like precursors, then using freeze-drying to form the final sponges. The SEM observed that the sponges had shown regular porous structures with a wide range of pore sizes from 160 to 440 μm. The sponges had presented the resistance to enzymatic degradation, shape-remaining ability, and reversible compressibility in aqueous environments, which all could be regulated through the functionalities of epoxides. The regulation abilities of multi-functional epoxides on the performances of sponges had been mainly achieved through the cross-linking degrees that the higher functionality of epoxides would bring higher cross-linking degree. Such higher cross-linking degrees could enhance the elastic behaviors of gel-like precursors, and improve the compressive strengths and thermal stabilities of sponges. Nevertheless, the multi-functional epoxides had barely affected the safety of collagen sponges at the cellular level according to the results of CCK8 assay and the SEM and CLSM images of L929 fibroblasts cultured on the cross-sections of sponges.

Safe and efficient capturing of volatile radioiodine is of extremely important significance in the treatment of spent fuel. Herein, the flake channels in gelatin-hydroxyapatite (HAP@Ge) cryogel with excellent flame retardant properties were constructed by immobilizing hydroxyapatite nanorods (HAP) on Gelatin (Ge) cryogel for enhancing the capturing of iodine. The immobilization of HAP nanorods enhanced thermal stability, provided low rates of dynamic heat transfer and dissipation, and remarkably improved the flame retardant and smoke suppression properties of the Ge cryogel, which can effectively prevent the occurrence of safety incidents caused by further thermal degradation or combustion of this cryogel. More importantly, it was effective in improving the rapid enrichment of iodine, resulting in a high adsorption capacity. The maximum adsorption capacity of HAP@Ge cryogel for iodine vapor reached 2693 mg/g at equilibrium. The high adsorption capacity for iodine was attributed to the multi-scale porous structure in HAP@Ge cryogel, which offered effective channels for iodine diffusion, whereas the numerous complex and irregular flakes provided sufficient number of active sites for iodine capture. The adsorption process was chemical in nature and involved the -PO₄ ³⁻, –OH, –C=O, and –NHR groups on HAP@Ge cryogel. Moreover, the complex porous structure of HAP@Ge cryogel enhanced the physical capturing of iodine. These advantages, such as low-cost raw material, simple preparation method, good flame retardancy, and excellent capturing performance for iodine indicated that HAP@Ge cryogel is a potential candidate for the removal of radioactive iodine in the exhaust gas stream of post-treatment plants.

Collagen-based biomaterials (CBB) are highly esteemed by researchers in materials science and biomedicine due to their extensive applications across various biomedical disciplines. In recent years, owing to advancements in developmental biology techniques, this superior biomaterial has seen increasing utilization in 3D in vitro tissue culture. Three-dimensional cell cultures, often referred to as organoids, have emerged in response to technological advancements in biomaterials and the growing need in the field of medical research. They serve as important models for simulating normal physiological activities in vivo, addressing limitations in experimental material sources, and resolving ethical issues. In this review, we discuss the material characteristics of CBBs commonly used for organoid culture, integrating aspects such as Matrigel and decellularized ECM as culture matrices. We also analyzed the development prospects and directions of various materials in the context of biology, clinical medicine, and particularly reproductive medicine. Currently, despite the FDA approval and clinical research incorporating numerous CBBs, existing challenges in multiple studies indicate a significant unmet need in the development of key tissue models for both medical research and clinical applications. In summary, CBBs are swiftly broadening their applicability in the realms of organoid nature and medical research, serving as a versatile and high-performing material for 3D in vitro tissue culture.

Compared with flavonoid glycosides, flavonoid aglycones are difficult to be separated since they have less hydroxyls. Collagen fiber (CF), a natural polymer, was once used as packing material for separation of kaempferol and quercetin (the typical flavonoid aglycones) after crosslinking by glutaraldehyde mainly based on hydrogen bonding and hydrophobic interaction in column length-diameter ratio of 60:1. Hydrophobic modification by grafting alkyl chains was then employed to enhance the hydrophobic interaction between CF and flavonoid aglycones, which can improve the separation efficiency and decrease column length-diameter ratio to 19:1. In order to further improve the adsorption capacity and separation efficiency, the strategy of simultaneously grafting hydrophobic alkyl chains (–CH₂–CH₂–) and alkali groups (–NH₂) was adopted in this work to enhance hydrophobic interaction, hydrogen bonding and electrostatic association to flavonoid aglycones at the same time through grafting polyethyleneimine (PEI). PEI modified CF (PEI-CF) maintained the fiber structure of CF, and had higher adsorption extent and rate to flavonoid aglycones through the enhanced synergetic effect of hydrophobic interaction, hydrogen bonding and electrostatic association. As a result, PEI-CF presented a satisfactory column separation efficiency for kaempferol and quercetin even the length-diameter ratio of column was decreased to 11:1, which was much better than previously developed glutaradehyde-crosslinked collagen fiber and isobutyl-grafted collagen fiber, as well as commonly used polyamide and Sephadex LH-20.

Metal organic frameworks (MOFs) with their large surface area and numerous active sites have attracted significant research attention. Recently, the application of MOFs for the catalytic degradation of organic pollutants has provided effective solutions to address diverse environmental problems. In this review, the latest progress in MOF-based removal and degradation of organic pollutants is summarized according to the different roles of MOFs in the removal reaction systems, such as physical adsorbents, enzyme-immobilization carriers, nanozymes, catalysts for photocatalysis, photo-Fenton and sulfate radical based advanced oxidation processes (SR-AOPs). Finally, the opportunities and challenges of developing advanced MOFs for the removal of organic pollutants are discussed and anticipated.

The development of advanced sustainable biomedical materials with superior biosafety and bioactivity for clinical applications is highly desirable. In the present investigation, biomass-based nanoparticles (NPs) were assembled through the Mannich reaction between the plant polyphenols and the broad-spectrum antibiotic tigecycline (TG). The fabricated NPs with uniform size demonstrated excellent oxidative balance effects, pH-responsive release properties and antibacterial performances. Furthermore, the intracellular and in vivo studies confirmed that the NPs are capable of reducing oxidative damage to cells and significantly repairing tissue injury in mice with peritonitis. This work presents an effective method and idea for constructing biomass-based materials for the treatment of infection-induced diseases.

Bone regeneration for large, critical-sized bone defects remains a clinical challenge nowadays. Guided bone regeneration (GBR) is a promising technique for the repair of multiple bone defects, which is widely used in oral and maxillofacial bone defects but is still unsatisfied in the treatment of long bone defects. Here, we successfully fabricated a bilayer mineralized collagen/collagen (MC/Col)-GBR membrane with excellent osteoinductive and barrier function by coating the MC particles prepared via in situ biomimetic mineralization process on one side of a sheet-like pure collagen layer. The aim of the present study was to investigate the physicochemical properties and biological functions of the MC/Col film, and to further evaluate its bone regeneration efficiency in large bone defect repair. Fourier-transform infrared spectra and X-ray diffraction patterns confirmed the presence of both hydroxyapatite and collagen phase in the MC/Col film, as well as the chemical interaction between them. stereo microscope, scanning electron microscopy and atomic force microscope showed the uniform distribution of MC particles in the MC/Col film, resulting in a rougher surface compared to the pure Col film. The quantitative analysis of surface contact angle, light transmittance and tensile strength demonstrated that the MC/Col film have better hydrophilicity, mechanical properties, light-barrier properties, respectively. In vitro macrophage co-culture experiments showed that the MC/Col film can effectively inhibit macrophage proliferation and fusion, reducing fibrous capsule formation. In vivo bone repair assessment of a rabbit critical segmental radial defect proved that the MC/Col film performed better than other groups in promoting bone repair and regeneration due to their unique dual osteoinductive/barrier function. These findings provided evidence that MC/Col film has a great clinical potential for effective bone defect repair.

The oral and craniofacial region consists of various types of hard and soft tissues with the intricate organization. With the high prevalence of tissue defects in this specific region, it is highly desirable to enhance tissue regeneration through the development and use of engineered biomaterials. Collagen, the major component of tissue extracellular matrix, has come into the limelight in regenerative medicine. Although collagen has been widely used as an essential component in biomaterial engineering owing to its low immunogenicity, high biocompatibility, and convenient extraction procedures, there is a limited number of reviews on this specific clinic sector. The need for mechanical enhancement and functional engineering drives intensive efforts in collagen-based biomaterials concentrating on therapeutical outcomes and clinical translation in oral and craniofacial tissue regeneration. Herein, we highlighted the status quo of the design and applications of collagen-based biomaterials in oral and craniofacial tissue reconstruction. The discussion expanded on the inspiration from the leather tanning process on modifications of collagen-based biomaterials and the prospects of multi-tissue reconstruction in this particular dynamic microenvironment. The existing findings will lay a new foundation for the optimization of current collagen-based biomaterials for rebuilding oral and craniofacial tissues in the future.

Supramolecular peptides exhibit obvious similarities with collagen fibers in terms of self-assembly characteristics, nanofibrous structure, and responsiveness to external stimuli. Here, a series of supramolecular peptides were developed by altering the amino acid sequence, enabling the self-assembly of three types of 4-biphenylacetic acid (BPAA)-tripeptides into fibrous hydrogel through hydrogen bonding and π–π stacking under the influence of ion induction. Transmission electron and scanning electron microscopies revealed that the diameter of the fiber within nanofibrous hydrogels was ~ 10 and ~ 40 nm, respectively, which was similar with the self-assembled collagen fibers. For this reason, these hydrogels could be considered as a biomimetic extracellular substitute. Meanwhile, the gelation concentration induced by ions was even lower than 0.66 wt%, with an elastic modulus of ~ 0.27 kPa, corresponding to a water content of 99.34 wt%. In addition, the three supramolecular hydrogels were found to be good substrates for L929 cell adhesion and MC-3T3 cell proliferation. The overall results implied that BPAA-based hydrogels have a lucrative application potential as cell carriers.

Spider-capture-silk (SCS) can directionally capture and transport water from humid air relying on the unique geometrical structure. Although there have been adequate reports on the fabrication of artificial SCSs from petroleum-based materials, it remains a big challenge to innovate bio-based SCS mimicking fibers with high-performance fog collection ability and efficiency simultaneously. Herein, we report an eco-friendly and economical fiber system for water collection by coating gelatin on degummed silk. Compared to the previously reported fibers with the best fog collection ability (~ 13.10 μL), Gelatin on silk fiber 10 (GSF10) can collect larger water droplet (~ 16.70 μL in 330 s) with ~ 98% less mass. Meanwhile, the water collection efficiency of GSF10 demonstrates ~ 72% and ~ 48% enhancement to the existing best water collection polymer coated SCS fibers and spidroin eMaSp2 coated degummed silk respectively in terms of volume-to-TCL (vapor–liquid-solid three-phase contact line) index. The simultaneous function of superhydrophilicity, surface energy gradient, and ~ 65% water-induced volume swelling of the gelatin knots are the key factors in advancing the water collection performance. Abundant availability of feedstocks and ~ 75% improved space utilization guarantee the scalability and practical application of such bio-based fiber.

Enzymes have been widely used as alternatives to conventional chemicals in cleaner leather processes due to their advantages of meeting increasing environmental demands. Especially, enzymatic unhairing based on protease has been applied to leather-making for a long time, however, it still has the key problem of slow permeation in the animal hide, resulting in slow unhairing rate, poor hair removal effect, excessive proteolysis of hide collagen, and decreased leather quality. Aiming at the key problem of bio-unhairing technology, fluorescent labeling technique and confocal laser scanning microscopy were used to investigate the protease permeation behaviors into the animal hide based on well-prepared labeled proteases, as well as the quantitative analysis of the protease amount in different hide layers. The results show that the protease mainly permeates the bovine hide through transfollicular routes from the hair side, and although the intercellular-interfibrillar pathway also exists, it does not play an important role. Additionally, the protease permeation behaviors into the hide are greatly impacted by the charge states of the hide and protease proteins, depending on the isoelectric points (pI) of the proteins and solution pH values. When the solution pH is not between the pI values of the two proteins, the similarly charged protease can quickly and deeply penetrate the hide because of the electrostatic repulsion. The established mechanism provides a theoretical basis for developing an efficient enzymatic unhairing technology for leather-making, and this can also be applied to other processes involving the enzyme permeation into the hide or leather.

Renewable and low-cost biomass is an ideal sustainable alternative to petroleum-based resources, but producing biomass-based carbon electrode with high performances remains a challenge. Herein, we propose a facile self-assembly strategy to fabricate a biomass-derived N, S co-doping carbon electrode from lignosulfonate without any activation or template process. Taking advantage of the coordination between Fe ions and lignosulfonate, the resultant carbon exhibits a spherical structure with abundant graphitized nanosheets, leading to a high specific surface area with rational pore structure, which are beneficial to the electron/ion transport and storage. The high contents of doping N (8.47 wt%) and S (2.56 wt%) significantly boost the electrochemical performances. As a supercapacitor electrode, the carbon material displays high specific capacitance of 390 F g⁻¹, excellent cycling stability and high energy density of 14.7 W h kg⁻¹ at a power density of 450 W kg⁻¹. This study provides a potential strategy for synthesizing cost-effective heteroatom-doped carbon materials from biomass with abundant functional groups and heteroatom sources, such as chitosan, collagen, and gelatin.

Effective protection against X-ray is the premise of utilizing the X-ray, thus it is critical to develop novel X-ray shielding materials with both low density and high X-ray attenuation efficiency. As the even distribution of high-Z element components is of great significance for increasing the attenuation efficiency of X-ray shielding materials, in this study, the microfiber membrane (MFM), a type of synthetic leather featuring hierarchical structure was chosen to provide large surface area for the dispersion of rare earth (RE) element. Meanwhile, plant polyphenol was utilized to achieve the stable loading and uniform dispersion of the Ce or Er into MFM. Benefiting from the assistance of polyphenol and hierarchical structure of MFM, the even dispersion of RE element was successfully realized. The resultant shielding materials displayed approximately 10% superior X-ray attenuation efficiency compared to that without polyphenol, and an averagely 9% increment in X-ray attenuation efficiency than that without hierarchical structure. Moreover, the obtained composite with a thickness of 2.8 mm displayed superior X-ray shielding performance compared to 0.25 mm lead sheet in 16–83 keV and retained an ultralow density of 1.4 g cm^–3. Our research results would shed new light on the manufacture of high-performance X-ray shielding materials with excellent X-ray shielding performance.

The production of high-valued organonitrogen chemicals, especially N-heterocycles, requires artificial N₂ fixation accompanied by the consumption of fossil resources. To avoid the use of these energy- and resource-intensive processes, we develop a sustainable strategy to convert nitrogen-rich animal biomass into N-heterocycles through a thermochemical conversion process (TCP) under atmospheric pressure. A high percentage of N-heterocycles (87.51%) were obtained after the TCP of bovine skin due to the abundance of nitrogen-containing amino acids (e.g., glycine, proline, and l-hydroxyproline). Animal biomass with more diverse amino acid composition (e.g., muscles) yielded higher concentrations of amines/amides and nitriles after TCP. In addition, by introducing catalysts (KOH for pyrrole and Al₂O₃ for cyclo-Gly–Pro) to TCP, the production quantities of pyrrole and cyclo-Gly–Pro increased to 30.79 mg g⁻¹ and 38.88 mg g⁻¹, respectively. This approach can be used to convert the significant animal biomass waste generated annually from animal culls into valued organonitrogen chemicals while circumventing NH₃-dependent and petrochemical-dependent synthesis routes.

This study developed an active and intelligent collagen-based packaging film with high strength for visually monitoring the freshness of fish. The results of scanning electron microscopy and atomic force microscopy showed that the film based on cross-linked collagen/delphinidin catalyzed by laccase exhibited a denser layer structure and a rougher surface. The dry and wet tensile strengths of the laccase-catalyzed collagen/delphinidin film (Col/Dp-LA film) increased by 41.74 MPa and 13.13 MPa in comparison with that of the pure collagen film, respectively. Moreover, the Col/Dp-LA film presented good antioxidant and barrier properties demonstrated by the results of free radical scavenging rate, light transmission rate, and water vapor permeability. The intelligent collagen-based film was obtained by incorporating Vaccinium oxycoccus pigment into the Col/Dp-LA film, which could change color under different pH values. When applied to the preservation of fish fillets, the film could release Dp to minimize oxidative rancidity and prolong the shelf life of the fish for 2 days. Meanwhile, the film showed visual color changes from purplish-red to greyish-blue after the fish spoilage. These results indicated that the collagen film treated with delphinidin, laccase, and Vaccinium oxycoccus pigment has potential application value in the field of active and intelligent food packaging.

Leather is one of the most popular products across globe and holds a significant place in the economy, while the pollution, associated to traditional leather industry, is far away on the “green chemistry” principles. In this sense, polyurethanes, which exhibit tunable chemical structures by selecting suitable precursors, can fit specific requirements, and the developments of green strategies make them important candidates for leather industry. This mini review briefly outlines the recent development of conventional (petrol-based) and sustainable polyurethanes in the leather industry, including their design and properties, in applications such as synthetic leather and surface-finishing (coatings/binders). Finally, outlooks of the future tendency, including more environmental-friendly strategies, bio-sourced/recycled materials and development of high-value multifunctional leather materials, are also here proposed.

The use of natural polysaccharide crosslinkers for decellularized matrices is an effective approach to prepare cardiovascular substitute materials. In this research, NaIO₄ was applied to oxidize konjac glucomannan to prepare the polysaccharide crosslinker oxidized konjac glucomannan (OKGM). The as-prepared crosslinker was then used to stabilize collagen-rich decellularized porcine peritoneum (DPP) to construct a cardiovascular substitute material (OKGM-fixed DPP). The results demonstrated that compared with GA-fixed DPP and GNP-fixed DPP, 3.75% OKGM [1:1.5 (KGM: NaIO₄)]-fixed DPP demonstrated suitable mechanical properties, as well as good hemocompatibility, excellent anti-calcification capability, and anti-enzymolysis in vitro. Furthermore, 3.75% OKGM [1:1.5 (KGM: NaIO₄)]-fixed DPP was suitable for vascular endothelial cell adhesion and rapid proliferation, and a single layer of endothelial cells was formed on the fifth day of culture. The in vivo experimental results also showed excellent histocompatibility. The current results demonstrted that OKGM was a novel polysaccharide cross-linking reagent for crosslinking natural tissues featured with rich collagen content, and 3.75% OKGM [1:1.5 (KGM: NaIO₄)]-fixed DPP was a potential cardiovascular substitute material.

The construction of biomass-based conductive hydrogel e-skins with high mechanical properties is the research hotspot and difficulty in the field of biomass materials. Traditional collagen-based conductive hydrogels, constructed by the typical “bottom–up” strategy, normally have the incompatible problem between high mechanical property and high collagen content, and the extraction of collagen is often necessary. To solve these problems, inspired by the high mechanical properties and high collagen content of animal skins, this work proposed a “top–down” construction strategy, in which the extraction of collagen was unnecessary and the skin collagen skeleton (SCS) with the 3D network structure woven by natural collagen fibers in goatskin was preserved and used as the basic framework of hydrogel. Following a four-step route, namely, pretreatment → soaking in AgNPs (silver nanoparticles) solution → soaking in the mixed solution containing HEA (2-hydroxyethyl methacrylate) and AlCl₃ → polymerization, this work successfully achieved the fabrication of a new skin-based conductive hydrogel e-skin with high mechanical properties (tensile strength of 2.97 MPa, toughness of 6.23 MJ·m⁻³ and breaking elongation of 428%) by using goatskin as raw material. The developed skin hydrogel (called PH@Ag) possessed a unique structure with the collagen fibers encapsulated by PHEA, and exhibited satisfactory adhesion, considerable antibacterial property, cytocompatibility, conductivity (3.06 S·m⁻¹) and sensing sensitivity (the maximum gauge factor of 5.51). The PH@Ag e-skin could serve as strain sensors to accurately monitor and recognize all kinds of human motions such as swallowing, frowning, walking, and so on, and thus is anticipated to have considerable application prospect in many fields including flexible wearable electronic devices, health and motion monitoring.

Hide and skin are complex tissue where the most abundant component is collagen. Matrix metalloproteinases and bacterial collagenases are two kinds of collagenases that can cleave the triple-helical domain of native fibrillar collagens. In this paper, the family members and domain composition of matrix metalloproteinases and bacterial collagenases are summarized. The catalytic mechanism of collagen hydrolysis by collagenases is described, and the methods adopted to date for investigating and regulating collagenases and their inhibitors are reviewed. Furthermore, the applications of collagenases and their inhibitors in biomedicine, food processing and the enzymatic unhairing process in the leather-making industry are presented.

In the present work, a comparative study of analytical methods for the simultaneous and quantitative determination of trivalent and hexavalent chromium is presented. For the analysis by ion chromatography-inductively coupled plasma-mass spectrometry, two different columns were tested, as well as different mobile phases and different pH of the samples. The optimized analytical method permitted the separation of Cr(III) and Cr(VI) using 75 mmol/L NH₄NO₃ pH 3 as chromatographic eluent. The method was validated and applied to real samples, allowing the determination of both species simultaneously, even when there is a huge difference of concentration between Cr(III) and Cr(VI). Limit of detection and limit of quantification for Cr(III) were found to be 0.016 and 0.054 $\upmu$g/L (0.3 and 1.1 $\upmu$g/kg), respectively, and for Cr(VI) 0.13 and 0.43 $\upmu$g/L (7 and 22 $\upmu$g/kg), respectively. Possible species interconversions were monitored through the use of chromium isotopic standards, which confirmed that the optimized methodology preserves chromium speciation during extraction and analysis. Fourier-transform ion cyclotron resonance-mass spectrometry permitted the structure elucidation of the complex formed during ethylenediaminetetraacetic acid extraction.