Animal skin,as a natural polymer material with abundant sources,was used to make various leather items in early human society.Ancient books,archives,and other cultural relics made from them carry profound cultural value.Studying the internal structure of them can provide good theoretical support for the protection and inheritance of cultural relics^[1].For example,artifacts such as parchment and Chinese shadow puppets that have not been tanned with tanning agents are called untanned hide artifacts.This system combined traditional production methods and modern processing techniques to study the performance changes of untanned hide during the production process.

The research method for untanned hide referred to IDAP(Improved Damage Assesment of Parchment)^[2],and quantitative and qualitative measurement methods such as SEM and FTIR^[3] were used to measure the effects of different pretreatment methods and chemical reagents on material properties.

The treatment methods for the samples in this study include saponification or emulsification reactions for defatting the raw skin,and adding different depilatory reagents, including alkaline reagents such as sodium sulfide or gastric protease,to the pretreated samples.

The analysis of infrared spectra in the study can reveal the effects of different chemical reagents on the peak shift of untanned Pete's characteristic,and SEM scanning can observe the changes in its intrinsic fiber configuration.The wet heat shrinkage temperature and stress-strain curve reflect the changes in its mechanical properties.

There is growing interest on the utilization of animal by-products and wastes based on sustainability and recycling of natural biomaterials. Animal by-products and wastes mainly refer to skin, bones, and tendons that contain proteins and other macromolecules[1]. Animal raw hides represent a remarkable portion of the weight of sheep (11.0–11.7%), which are abundant sources of epithelial tissue that contains a high concentration of collagen[2]. As the primary ingredients to produce leather products, these raw materials undergo trimming to achieve uniform shapes before commencing the tanning process, which may generate considerable proteinaceous waste[3]. Reportedly, one ton of wet salted hides/skins yields approximately 200kg finished leather along with 350 kg non-tanned solid waste, 250 kg tanned solid waste, and 200 kg wastewater loss[4]. Hence, there remains a considerable of lamb trimming wastes of tannery for the collagen recycle. Plant-based enzymes including papain and bromelain have been utilized for extracting gelatin or collagen from un-tanned bovine trimming waste. Given the potential of ficin enzyme for collagen hydrolysis[5], harnessing this enzyme to extract collagen from discarded sheep trimming waste could be beneficial. In addition, with aided ultrasound, entangled collagen fibrils can be opened then separated, contributing to post-treatment with acids or enzymes as well as reduced extraction periods. 

Based on aided ultrasound technology, the aim of this research is to design a sustainable method for extracting collagen from untreated tannery trimming waste using ficin enzyme derived from ficin leaves. The structural and biochemical characteristics of the extracted collagen from this green method and conventional methods (acetic acid) will be fully discussed.

A simple and effective method for the extraction of collagen from untanned tannery trimming waste using acetic acid and ficin enzyme obtained from ficin leaves was developed in this study. Although acetic acid and ficin enzyme both are effective for the extraction of collagen but enzymatic hydrolysis can extract more collagen than the acid hydrolysis method. Collagen obtained from the enzymatic hydrolysis process maintained its predominant triple helix structure and had amorphousness which was confirmed by the FTIR and XRD analysis. However, the collagen obtained from enzymatic hydrolysis was thermally less stable compared to the collagen obtained by acid hydrolysis. Hence, it can be concluded that ficin enzyme- assisted hydrolysis method can aid in the implementation of circular economy approach in the leather industry by extracting collagen from the trimming waste in an environment-friendly way.
 

Tissue wounds afflict millions of individuals annually, giving rise to significant social and economic concerns. Previous investigations have demonstrated the remarkable potential of hydrogels in wound healing owing to their exceptional capabilities in absorbing wound exudate, moisturizing, facilitating oxygen permeation, and possessing a three-dimensional porous structure[1]. However, natural polymer-based hydrogel dressings for wounds often suffer from susceptibility to bacterial growth and subsequent infection, which represents a major obstacle impeding the wound healing process.
Photothermal therapy (PTT) is a strategy to achieve antibacterial effect through rapid hyperthermia produced by a photothermal agent under near-infrared (NIR) light radiation (700-1100 nm). Compared with conventional antibacterial methods, PTT offers distinct advantages including heightened sterilization potency, reduced treatment duration, and diminished risk of drug-resistant bacteria[2]. We previously synthesized stable tricomplex molecules (PA@Fe) assembled by protocatechualdehyde (PA) and ferric iron, which were subsequently embedded in a gelatin hydrogel (Gel-PA@Fe). The embedded PA@Fe served as a crosslinker to improve the mechanical and adhesive properties of hydrogels through coordination bonds and dynamic Schiff base bonds, meanwhile acting as a photothermal agent to convert NIR light into heart to kill bacteria effectively[3]. The hydrogel was endowed with exceptional hemostatic and antioxidant properties by grafting serotonin onto the gelatin molecular chain, resulting in the preparation of a composite hydrogel (GelS-PA@Fe). As a mediator of blood coagulation, serotonin can interact with catechol-containing PA and chemical hemostatic agents, thereby enhancing the adhesion of more blood cells to the hydrogel surface. The free radical scavenging rate of GelS-PA@Fe (80.49%) exhibited a 1.5-fold increase compared to that of the Gel-PA@Fe hydrogel, indicating enhanced efficacy in neutralizing free radicals. Importantly, the introduction of serotonin did not compromise the biocompatibility and photothermal antibacterial properties of the GelS-PA@Fe hydrogel. Our results indicated the great potential of GelS-PA@Fe hydrogel in promoting infected wound healing.