Collagen-based materials in reproductive medicine and engineered reproductive tissues

Collagen, the main component of mammal skin, has been traditionally used in leather manufacturing for thousands of years due to its diverse physicochemical properties. Collagen is the most abundant protein in mammals and the main component of the extracellular matrix (ECM). The properties of collagen also make it an ideal building block for the engineering of materials for a range of biomedical applications. Reproductive medicine, especially human fertility preservation strategies and reproductive organ regeneration, has attracted significant attention in recent years as it is key in resolving the growing social concern over aging populations worldwide. Collagen-based biomaterials such as collagen hydrogels, decellularized ECM (dECM), and bioengineering techniques including collagen-based 3D bioprinting have facilitated the engineering of reproductive tissues. This review summarizes the recent progress in applying collagen-based biomaterials in reproductive. Furthermore, we discuss the prospects of collagen-based materials for engineering artificial reproductive tissues, hormone replacement therapy, and reproductive organ reconstruction, aiming to inspire new thoughts and advancements in engineered reproductive tissues research. Graphical abstract

Polycaprolactone strengthening keratin/bioactive glass composite scaffolds with double cross-linking networks for potential application in bone repair

In this study, we aimed at constructing polycaprolactone (PCL) reinforced keratin/bioactive glass composite scaffolds with a double cross-linking network structure for potential bone repair application. Thus, the PCL-keratin-BG composite scaffold was prepared by using keratin extracted from wool as main organic component and bioactive glass (BG) as main inorganic component, through both cross-linking systems, such as the thiol-ene click reaction between abundant sulfhydryl groups of keratin and the unsaturated double bond of 3-methacryloxy propyltrimethoxy silane (MPTS), and the amino-epoxy reaction between amino groups of keratin and the epoxy group in (3-glycidoxymethyl) methyldiethoxysilane (GPTMS) molecule, along with introduction of PCL as a reinforcing agent. The success of the thiol-ene reaction was verified by the FTIR and 1H-NMR analyses. And the structure of keratin-BG and PCL-keratin-BG composite scaffolds were studied and compared by the FTIR and XRD characterization, which indicated the successful preparation of the PCL-keratin-BG composite scaffold. In addition, the SEM observation, and contact angle and water absorption rate measurements demonstrated that the PCL-keratin-BG composite scaffold has interconnected porous structure, appropriate pore size and good hydrophilicity, which is helpful to cell adhesion, differentiation and proliferation. Importantly, compression experiments showed that, when compared with the keratin-BG composite scaffold, the PCL-keratin-BG composite scaffold increased greatly from 0.91 ± 0.06 MPa and 7.25 ± 1.7 MPa to 1.58 ± 0.21 MPa and 14.14 ± 1.95 MPa, respectively, which suggesting the strong reinforcement of polycaprolactone. In addition, the biomineralization experiment and MTT assay indicated that the PCL-keratin-BG scaffold has good mineralization ability and no-cytotoxicity, which can promote cell adhesion, proliferation and growth. Therefore, the results suggested that the PCL-keratin-BG composite scaffold has the potential as a candidate for application in bone regeneration field. Graphical Abstract

Toxicity evaluation of collagen hydrolysates from chrome shavings and their potential use in the preparation of amino acid fertilizer for crop growth

Resource utilization of chrome shavings (CS) has attracted a lot of attention from scientists and technologists in leather industry. Especially, the collagen hydrolysates extracted from CS are expected to find potential application values in agricultural field. However, there is no biotoxicity analysis of collagen hydrolysates from CS. Herein, the collagen hydrolysates with different molecular weights were produced from CS by three hydrolysis dechroming methods including alkaline hydrolysis, enzymatic hydrolysis and alkaline-enzymatic synergistic hydrolysis, and the optimal hydrolysis process of CS was designed and conducted. To evaluate their toxicity, the three collagen hydrolysates were formulated into a nutrient solution for zebrafish development. The obtained results indicated that the hydrolysates with low concentrations (less than 0.6 mg/mL) were safe and could promote the development for zebrafish embryos. Furthermore, the three collagen hydrolysates were utilized as organic nitrogen sources and formulated into amino acid water-soluble fertilizers (AAWSF) including alkaline type fertilizer (OH), enzymatic type fertilizer (M) and alkaline-enzymatic type fertilizer (OH–M) for the early soilless seeding cultivation of wheat, soybean and rapeseed. It is worth mentioning that the chromium contents in the prepared AAWSF were less than 10 mg/kg, which is far less than the limit value in the standard (China, 50 mg/kg). The growth and development of seedlings (germination rate, plant height, fresh weight of leaves, soluble sugar content and chlorophyll content) were investigated. The corresponding results showed that the growth of seedlings watered with AAWSF was better compared with the other treatments, and the OH–M fertilizer had the best promoting effect on the seedlings growth and development, followed by the M and OH fertilizers. The safe toxicity assessment of the collagen hydrolysates will expand their application scope, and the use of collagen hydrolysates extracted from CS for seedlings growth also provides an effective and reasonable way to deal with the chromium-containing leather solid waste, which is an effective way to realize its resource utilization. Graphical Abstract

Sustainable and invisible anti-counterfeiting inks based on waterborne polyurethane and upconversion nanoparticles for leather products

Counterfeit leather products infringe the intellectual property rights of the business, cause enormous economic loss, and negatively influence the business enthusiasm for innovation. However, traditional anti-counterfeiting materials for leather products suffer from complicated fabrication procedures, photobleaching, and high volatile organic compound (VOC) emissions. Here, a sustainable and invisible anti-counterfeiting ink composed of waterborne polyurethane and water-dispersible lanthanide-doped upconversion nanoparticles (UCNPs) featuring ease of preparation, high photostability, non-toxicity, low VOC emissions, and strong adhesion strength for leather products is designed and synthesized. After decorating on the surface of leather products, the obtained patterns are invisible under normal light conditions. Upon irradiation at 808 nm, the invisible patterns can be observed by naked eyes due to the visible light emitted by 808 nm excited UCNPs. Our approach described here opens a new pathway to realize the long-term, stable anti-counterfeiting function of leather products. Graphical Abstract

Sweet sorghum for phytoremediation and bioethanol production

As an energy crop, sweet sorghum (Sorghum bicolor (L.) Moench) receives increasing attention for phytoremediation and biofuels production due to its good stress tolerance and high biomass with low input requirements. Sweet sorghum possesses wide adaptability, which also has high tolerances to poor soil conditions and drought. Its rapid growth with the large storage of fermentable saccharides in the stalks offers considerable scope for bioethanol production. Additionally, sweet sorghum has heavy metal tolerance and the ability to remove cadmium (Cd) in particular. Therefore, sweet sorghum has great potential to build a sustainable phytoremediation system for Cd-polluted soil remediation and simultaneous ethanol production. To implement this strategy, further efforts are in demand for sweet sorghum in terms of screening superior varieties, improving phytoremediation capacity, and efficient bioethanol production. In this review, current research advances of sweet sorghum including agronomic requirements, phytoremediation of Cd pollution, bioethanol production, and breeding are discussed. Furthermore, crucial problems for future utilization of sweet sorghum stalks after phytoremediation are combed. Graphical Abstract

A deeper exploration of the relation between sulfonation degree and retanning performance of aromatic syntans

It is well-known that the sulfonation degree (DS) of aromatic syntan is an important factor affecting its retanning performances. But the quantitative relation between DS and syntan property and the influencing mechanism of DS on syntan property are not clarified. In this work, five phenolic formaldehyde syntans (PFSs) with the same polymerization degree but varying DS were prepared to investigate the effect of DS on the properties of syntan and crust leather. It was found that the absolute value of zeta potential and the particle size of PFS decreased with increasing DS in aqueous solution. Molecular dynamic simulation results proved that the DS of PFS was a major contributor to electrostatic interaction and hydrogen bonding in the PFS–water system and greatly affected the aggregation and dispersion of PFS in aqueous solution. The PFS with a low DS was prone to aggregate to large particles in aqueous solution because of low intermolecular electrostatic repulsion and less hydrogen bonds and therefore can be used to increase the thickness and tightness of leather. The PFS with a high DS presented a small particle size with more anionic groups in aqueous solution, thereby sharply decreasing the positive charge of leather surface and facilitating the penetration of the post-tanning agents into the leather. These results might be scientifically valid for rational molecular design of syntans and more productive use of syntans in leather making. Graphical Abstract

Evaluation and improvement of the oxidative stability of leather fatliquors

Fatliquor oxidation may give leather unpleasant odor, and excessive amounts of Cr(VI) and volatile organic compounds. The accurate evaluation and improvement of the oxidative stability of fatliquors are of great significance to high-quality leather manufacturing. We proposed a set of practical methods for evaluating the oxidative stability of fatliquors on the basis of oxidation induction time, change in iodine value (∆ IV), and change in acid value (∆ AV) under accelerated oxidation conditions (at 100 °C with 10 L/h of air). Oxidation induction time is a highly sensitive marker for quantifying the oxidative stability of fatliquors, and ∆ IV and ∆ AV that are low cost and easy to operate are useful in evaluating the oxidative stability of fatliquors when the oxidation induction time is less than 22 h. The number of double bonds in fatliquors is an important factor affecting oxidative stability. The sulfation modification of fatliquors that greatly reduces double bonds and the addition of antioxidants, especially butylated hydroxyanisole and butylated hydroxytoluene, markedly improve oxidative stability of fatliquors.

Facile and scalable preparation of ZIF-67 decorated cotton fibers as recoverable and efficient adsorbents for removal of malachite green

Recently, metal–organic frameworks (MOFs) have received considerable attention as highly efficient adsorbents for dye wastewater remediation. However, the immobilization of MOFs on the substrate surfaces to fabricate easy recyclable adsorbents via a facile route is still a challenge. In this work, ZIF-67/cotton fibers as adsorbents for dye removal were prepared in a large-scale using a simple coordination replication method. The successful fabrication of the ZIF-67/cotton fibers was confirmed by FTIR, XRD, XPS, SEM and BET analysis, respectively. As expected, the as-prepared ZIF-67/cotton fibers exhibited high adsorption capacity of 3787 mg/g towards malachite green (MG). Meanwhile, the adsorption kinetics and isotherm obeyed the pseudo-second-order kinetics and Langmuir model, respectively. Moreover, its removal efficiency towards MG was not significantly influenced by the pH and ionic strength of aqueous solution. Most importantly, the ZIF-67/cotton fibers can remove MG from synthetic effluents, and it can be easily regenerated without filtration or centrifugation processes, with the regeneration efficiency remaining over 90% even after 10 cycles. Additionally, the ZIF-67/cotton fibers presented excellent antimicrobial performance against E. coli and S. aureus. Hence, the distinctive features of the as-prepared ZIF-67/cotton fibers make it promisingly applicable for the colored wastewater treatment.

Quantitative extraction of chromium VI and III from tanned leather: a comparative study of pretreatment methods

In this study, seven pretreatment methods for chromium speciation in tanned leather were evaluated: acidic mineralization, ethylenediaminetetraacetic acid (EDTA) extraction, diethylenetriaminepentaacetic acid (DTPA) extraction, alkaline extraction (NH4OH), ammonium nitrate extraction (NH4NO3), water extraction, and phosphate buffer extraction. Acidic mineralization permitted the decomposition of the organic matter and ensured the complete digestion of leathers, giving access to the total content of chromium in each sample using inductively coupled plasma-atomic emission spectrometry (ICP-AES). From all the extractant media tested, EDTA proved to be the most efficient, allowing the extraction of Cr(VI) and Cr(III) as a Cr(III)-EDTA complex, quantitatively. Method validation is presented for EDTA extraction and direct mineralization. For the EDTA extraction, method detection limit (MDL) and method quantification limit (MQL) for total Cr in leather were 3.4 ppb and 11.2 ppb (µg of total Cr per L of extraction solution), respectively. Due to the lack of leather certified reference materials (CRMs) for Cr(VI), accuracy was evaluated by spiking leather samples with a Cr(VI) solution. The spike recovery of EDTA microwave assisted extraction ranged from 91.0 to 108.6%. Interday precision was also evaluated and all variation coefficients were below 5%, for both mineralization and EDTA extraction. This article provides an efficient procedure to extract quantitatively chromium from leather, while maintaining the speciation, which can be further followed by ion chromatography-inductively coupled plasma-mass spectrometry (IC-ICP-MS).

Application of acidic protease in the pickling to simplify the pelt bating process

Traditionally, universally used pelt bating technologies rely on the application of trypsin, neutral and alkaline microbial proteases but suffer from complicated operation, limited bating efficiency and unsatisfactory leather performance. Therefore, devising a new pelt bating approach to achieve high bating efficiency and excellent leather performance has always been wished for by the leather industry. To pursue this goal, years of persistent research work enabled us to develop a novel approach for pelt bating by means of acidic proteases in pickling process. Initially, basic enzymatic characteristics and bating effectiveness of several typical acidic proteases in pelt pickling medium were investigated; then, the bating effectiveness through the quantitative characterization of protease activity of the optimal acidic protease was compared with that of the conventional bating enzyme. The results indicated that all of the selected acidic proteases had good salt-tolerance and exhibited optimum activity at pH 3.0–4.0. The novel pickling-bating method based on microbial origin acidic protease L80A led to an outstanding performance on pelt bating at the dosage of 150 U/mL of collagenolytic activity. The bating effectiveness of acidic protease L80A was comparable to and even better than that of trypsin BEM due to its moderate proteolytic ability. Moreover, the deep and even penetration of acidic protease in the pelt permitted it to produce soft, organoleptically stable and overall better quality crust leather than that of the conventional trypsin bating method. Additionally, pelt bating was performed along with the pickling process without extra inactivation and washing operation, making the bating operation more efficient, economical, and environment friendly. Results had made us to conclude that this cutting-edge acidic proteases based pickling-bating method could be the first step/ way forward to replace the decades-old traditional pelt bating technology.