Finite element analysis of meniscus contact mechanical behavior based on kinematic simulation of abnormal gait.

The meniscus plays a crucial role in the proper functioning of the knee joint, and when it becomes damaged, partial removal or replacement is necessary to restore proper function. Understanding the stress and deformation of the meniscus during various movements is essential for developing effective materials for meniscus repair. However, accurately estimating the contact mechanics of the knee joint can be challenging due to its complex shape and the dynamic changes it undergoes during movement. To address this issue, the open-source software SCONE can be used to establish a kinematics model that monitors the different states of the knee joint during human motion and obtains relevant gait kinematics data. To evaluate the stress and deformation of the meniscus during normal human movement, values of different states in the movement gait can be selected for finite element analysis (FEA) of the knee joint. This analysis enables researchers to assess changes in the meniscus. To evaluate meniscus damage, it is necessary to obtain changes in its mechanical behavior during abnormal movements. This information can serve as a reference for designing and optimizing the mechanical performance of materials used in meniscus repair and replacement.

Calibrating ultrasonic sensor measurements of crop canopy heights: a case study of maize and wheat.

Canopy height serves as an important dynamic indicator of crop growth in the decision-making process of field management. Compared with other commonly used canopy height measurement techniques, ultrasonic sensors are inexpensive and can be exposed in fields for long periods of time to obtain easy-to-process data. However, the acoustic wave characteristics and crop canopy structure affect the measurement accuracy. To improve the ultrasonic sensor measurement accuracy, a four-year (2018-2021) field experiment was conducted on maize and wheat, and a measurement platform was developed. A series of single-factor experiments were conducted to investigate the significant factors affecting measurements, including the observation angle (0-60°), observation height (0.5-2.5 m), observation period (8:00-18:00), platform moving speed with respect to the crop (0-2.0 m min-1), planting density (0.2-1 time of standard planting density), and growth stage (maize from three-leaf to harvest period and wheat from regreening to maturity period). The results indicated that both the observation angle and planting density significantly affected the results of ultrasonic measurements (p-value< 0.05), whereas the effects of other factors on measurement accuracy were negligible (p-value > 0.05). Moreover, a double-input factor calibration model was constructed to assess canopy height under different years by utilizing the normalized difference vegetation index and ultrasonic measurements. The model was developed by employing the least-squares method, and ultrasonic measurement accuracy was significantly improved when integrating the measured value of canopy heights and the normalized difference vegetation index (NDVI). The maize measurement accuracy had a root mean squared error (RMSE) ranging from 81.4 mm to 93.6 mm, while the wheat measurement accuracy had an RMSE from 37.1 mm to 47.2 mm. The research results effectively combine stable and low-cost commercial sensors with ground-based agricultural machinery platforms, enabling efficient and non-destructive acquisition of crop height information.

Fabrication of a modified bacterial cellulose with different alkyl chains and its prevention of abdominal adhesion.

Abdominal hernia mesh is a common product which is used for prevention of abdominal adhesion and repairing abdominal wall defect. Currently, designing and preparing a novel bio-mesh material with prevention of adhesion, promoting repair and good biocompatibility simultaneously remain a great bottleneck. In this study, a novel siloxane-modified bacterial cellulose (BC) was designed and fabricated by chemical vapor deposition silylation, then the effects of different alkyl chains length of siloxane on surface properties and cell behaviors were explored. The effect of preventing of abdominal adhesion and repairing abdominal wall defect in rats with the siloxane-modified BC was evaluated. As the grafted alkyl chains become longer, the surface of the siloxane-modified BC can be transformed from super hydrophilic to hydrophobic. In vivo results showed that BC-C16 had good long-term anti-adhesion effect, good tissue adaptability and histocompatibility, which is expected to be used as a new anti-adhesion hernia repair material in clinic.

Stimuli-responsive microcarriers and their application in tissue repair: A review of magnetic and electroactive microcarrier.

Microcarrier applications have made great advances in tissue engineering in recent years, which can load cells, drugs, and bioactive factors. These microcarriers can be minimally injected into the defect to help reconstruct a good microenvironment for tissue repair. In order to achieve more ideal performance and face more complex tissue damage, an increasing amount of effort has been focused on microcarriers that can actively respond to external stimuli. These microcarriers have the functions of directional movement, targeted enrichment, material release control, and providing signals conducive to tissue repair. Given the high controllability and designability of magnetic and electroactive microcarriers, the research progress of these microcarriers is highlighted in this review. Their structure, function and applications, potential tissue repair mechanisms, and challenges are discussed. In summary, through the design with clinical translation ability, meaningful and comprehensive experimental characterization, and in-depth study and application of tissue repair mechanisms, stimuli-responsive microcarriers have great potential in tissue repair.

Decellularized laser micro-patterned osteochondral implants exhibit zonal recellularization and self-fixing for osteochondral regeneration in a goat model.

Background: Osteochondral regeneration has long been recognized as a complex and challenging project in the field of tissue engineering. In particular, reconstructing the osteochondral interface is crucial for determining the effectiveness of the repair. Although several artificial layered or gradient scaffolds have been developed recently to simulate the natural interface, the functions of this unique structure have still not been fully replicated. In this paper, we utilized laser micro-patterning technology (LMPT) to modify the natural osteochondral "plugs" for use as grafts and aimed to directly apply the functional interface unit to repair osteochondral defects in a goat model. Methods: For in vitro evaluations, the optimal combination of LMPT parameters was confirmed through mechanical testing, finite element analysis, and comparing decellularization efficiency. The structural and biological properties of the laser micro-patterned osteochondral implants (LMP-OI) were verified by measuring the permeability of the interface and assessing the recellularization processes. In the goat model for osteochondral regeneration, a conical frustum-shaped defect was specifically created in the weight-bearing area of femoral condyles using a customized trephine with a variable diameter. This unreported defect shape enabled the implant to properly self-fix as expected. Results: The micro-patterning with the suitable pore density and morphology increased the permeability of the LMP-OIs, accelerated decellularization, maintained mechanical stability, and provided two relative independent microenvironments for subsequent recellularization. The LMP-OIs with goat's autologous bone marrow stromal cells in the cartilage layer have securely integrated into the osteochondral defects. At 6 and 12 months after implantation, both imaging and histological assessments showed a significant improvement in the healing of the cartilage and subchondral bone. Conclusion: With the natural interface unit and zonal recellularization, the LMP-OI is an ideal scaffold to repair osteochondral defects especially in large animals. The translational potential of this article: These findings suggest that such a modified xenogeneic osteochondral implant could potentially be explored in clinical translation for treatment of osteochondral injuries. Furthermore, trimming a conical frustum shape to the defect region, especially for large-sized defects, may be an effective way to achieve self-fixing for the implant.

Injectable and in situ foaming shape-adaptive porous Bio-based polyurethane scaffold used for cartilage regeneration.

Irregular articular cartilage injury is a common type of joint trauma, often resulting from intense impacts and other factors that lead to irregularly shaped wounds, the limited regenerative capacity of cartilage and the mismatched shape of the scaffods have contributed to unsatisfactory therapeutic outcomes. While injectable materials are a traditional solution to adapt to irregular cartilage defects, they have limitations, and injectable materials often lack the porous microstructures favorable for the rapid proliferation of cartilage cells. In this study, an injectable porous polyurethane scaffold named PU-BDO-Gelatin-Foam (PUBGF) was prepared. After injection into cartilage defects, PUBGF forms in situ at the site of the defect and exhibits a dynamic microstructure during the initial two weeks. This dynamic microstructure endows the scaffold with the ability to retain substances within its interior, thereby enhancing its capacity to promote chondrogenesis. Furthermore, the chondral repair efficacy of PUBGF was validated by directly injecting it into rat articular cartilage injury sites. The injectable PUBGF scaffold demonstrates a superior potential for promoting the repair of cartilage defects when compared to traditional porous polyurethane scaffolds. The substance retention ability of this injectable porous scaffold makes it a promising option for clinical applications.

A dual dynamically cross-linked hydrogel promotes rheumatoid arthritis repair through ROS initiative regulation and microenvironment modulation-independent triptolide release.

High oxidative stress and inflammatory cell infiltration are major causes of the persistent bone erosion and difficult tissue regeneration in rheumatoid arthritis (RA). Triptolide (TPL) has become a highly anticipated anti-rheumatic drug due to its excellent immunomodulatory and anti-inflammatory effects. However, the sudden drug accumulation caused by the binding of "stimulus-response" and "drug release" in a general smart delivery system is difficult to meet the shortcoming of extreme toxicity and the demand for long-term administration of TPL. Herein, we developed a dual dynamically cross-linked hydrogel (SPT@TPL), which demonstrated sensitive RA microenvironment regulation and microenvironment modulation-independent TPL release for 30 days. The abundant borate ester/tea polyphenol units in SPT@TPL possessed the capability to respond and regulate high reactive oxygen species (ROS) levels on-demand. Meanwhile, based on its dense dual crosslinked structure as well as the spontaneous healing behavior of numerous intermolecular hydrogen bonds formed after the breakage of borate ester, TPL could remain stable and slowly release under high ROS environments of RA, which dramatically reduced the risk of TPL exerting toxicity while maximized its long-term efficacy. Through the dual effects of ROS regulation and TPL sustained-release, SPT@TPL alleviated oxidative stress and reprogrammed macrophages into M2 phenotype, showing marked inhibition of inflammation and optimal regeneration of articular cartilage in RA rat model. In conclusion, this hydrogel platform with both microenvironment initiative regulation and TPL long-term sustained release provides a potential scheme for rheumatoid arthritis.

Low-Temperature Extrusion of Waterborne Polyurethane-Polycaprolactone Composites for Multi-Material Bioprinting of Engineered Elastic Cartilage.

3D bioprinting of elastic cartilage tissues that are mechanically and structurally comparable to their native counterparts, while exhibiting favorable cellular behavior, is an unmet challenge. A practical solution for this problem is the multi-material bioprinting of thermoplastic polymers and cell-laden hydrogels using multiple nozzles. However, the processing of thermoplastic polymers requires high temperatures, which can damage hydrogel-encapsulated cells. In this study, the authors developed waterborne polyurethane (WPU)-polycaprolactone (PCL) composites to allow multi-material co-printing with cell-laden gelatin methacryloyl (GelMA) hydrogels. These composites can be extruded at low temperatures (50-60 °C) and high speeds, thereby reducing heat/shear damage to the printed hydrogel-capsulated cells. Furthermore, their hydrophilic nature improved the cell behavior in vitro. More importantly, the bioprinted structures exhibited good stiffness and viscoelasticity compared to native elastic cartilage. In summary, this study demonstrated low-temperature multi-material bioprinting of WPU-PCL-based constructs with good mechanical properties, degradation time-frames, and cell viability, showcasing their potential in elastic cartilage bio-fabrication and regeneration to serve broad biomedical applications in the future.

Occurrence and seasonal variation of Perkinsus sp. Infection in wild mollusk populations from coastal waters of Qingdao, northern China.

Perkinsosis has been recognized as one of the major threats to natural and farmed bivalve populations, many of which are of commercial as well as environmental significance. Three Perkinsus species have been identified in China, and the Manila clam (Ruditapes philippinarum) was the most frequently infected species in northern China. Although the occurrence and seasonal variation of Perkinsus spp. have previously been examined, the pathological characteristics of these infections in wild Manila clams and sympatric species in China have seldom been reported. In the present study, the prevalence and intensity of Perkinsus infection in wild populations of Manila clams and 10 sympatric species from three sites were investigated by Ray's fluid thioglycolate medium (RFTM) assay seasonally across a single year. Perkinsus infection was only identified in Manila clams, with a high prevalence (274/284 = 96.48 %) and low intensity (89.8 % with a Mackin value ≤ 2, suggesting generally low-intensity infections) throughout the year. Heavily infected clams were mainly identified in Tianheng in January, which displayed no macroscopic signs of disease. An overview of the whole visceral mass section showed that the trophozoites mostly aggregated in gills and connective tissue of the digestive tract, to a lesser extent in the mantle and foot, and even less frequently in adductor muscle and connective tissues of the gonad. PCR and ITS-5.8S rRNA sequencing of 93 representative RFTM-positive samples revealed a 99.69 to 100 % DNA sequence identity to Perkinsus olseni. Unexpectedly, significantly higher infection intensities were usually identified in January and April when the Condition Index (CI) was relatively high. We propose that factors associated with the anthropogenic harvesting pressure and irregular disturbances should be responsible for the uncommon seasonal infection dynamics of perkinsosis observed in the present study.

The Probiotic Bacillus hwajinpoensis Colonizes the Digestive System of Crassostrea gigas Larvae and Protects Them from Vibrio alginolyticus Infection.

The Pacific oyster Crassostrea gigas is one of the most important cultured marine species around the world. Production of Pacific oysters in China has depended primarily on hatchery produced seeds since 2016, with the successful introduction and development of triploid oysters. However, the seed supply of Pacific oysters is threatened by recurring mass mortality events in recent years. Vibriosis is the most commonly encountered disease associated with intensive oyster culture in hatcheries and nurseries. Vibrio alginolyticus and Bacillus hwajinpoensis were the two strains with pathogenic and probiotic effects, respectively, identified during the Pacific oyster larvae production. To monitor their colonization process in Pacific oyster larvae, green fluorescent protein (GFP) and red fluorescent protein (RFP) were labeled to the pathogenic V. alginolyticus and the probiotic B. hwajinpoensis stain, respectively. The pathogenic and probiotic effects of the two strains during the colonization process were then assessed. Stabile expression of GFP and RFP were observed in corresponding stains, and the capabilities of growth, biofilm formation and in vitro adhesion of GFP- and RFP- tagged stains were not significantly different from those of the wild-type strains. Usage of probiotics of 105 CFU/mL significantly inhibited the growth of pathogenic V. alginolyticus and reduced the mortality of D-sharped larvae. Both the pathogenic and probiotic strains employed a similar route to enter and colonize the oyster larvae, which indicates that competing with pathogens for binding and spreading sites were one of the mechanisms of B. hwajinpoensis to provide the probiotic effects to oyster larvae. In summary, employment of fluorescence-tagged pathogenic and probiotic strains simultaneously provides us with an excellent bioassay model to investigate the potential mechanisms of probiotics.

In Situ Polymerization of Methylene Blue on Bacterial Cellulose for Photodynamic/Photoelectricity Synergistic Inhibition of Bacterial Biofilm Formation.

In the context of long-term antimicrobial treatment, the emergence of bacterial resistance poses a significant challenge. Therefore, there is a pressing need to develop novel antimicrobial materials and methods that can effectively and safely combat microbial infections. This study focuses on the synthesis of bacterial cellulose-polymethylene blue (BC-PMB) with integrated photodynamic and photoelectric antimicrobial properties. The polymerization of methyl blue (MB) onto bacterial celluloses (BC) was achieved, and through comprehensive computational analyses using density functional theory (DFT) and molecular dynamics simulations, it was confirmed that this polymerization greatly enhanced the binding efficiency between methylene blue and BC. Additionally, polymethylene blue (PMB) exhibited superior photoexcitation efficiency and conductivity compared to its precursor. When BC-PMB was exposed to a 30 mW 660 nm light source for 30 min, the material demonstrated a remarkable antimicrobial efficacy of 93.99% against Escherichia coli and 98.58% against Staphylococcus aureus. Furthermore, the synergistic effect of photodynamic and photoelectric antimicrobial mechanisms exhibited long-term inhibitory capabilities against bacterial biofilms.

Chitosan/polydopamine/octacalcium phosphate composite microcarrier simulates natural bone components to induce osteogenic differentiation of stem cells.

Natural polymers and minerals can be combined to simulate natural bone for repairing bone defects. However, bone defects are often irregular and pose challenges for their repair. To overcome these challenges, we prepared Chitosan/Polydopamine/Octacalcium phosphate (CS/PDA/OCP) microcarriers that mimic bone composition and micro-size to adapt to different bone defect defects. CS/PDA microspheres were prepared by emulsion phase separation method and PDA in-situ polymerization. Finally, it was used to adsorb and immobilize OCP particles, resulting in the preparation of CS/PDA/OCP composite microcarriers. The microcarriers maintain an interconnected porous structure and appropriate porosity, which promotes cell adhesion, proliferation, and nutrient exchange. Subsequently, the protein adsorption capacity, simulated degradation, cell adhesion and proliferation capacity of the composite microcarriers were investigated. Additionally, their ability to simulate mineralization and induce osteogenic differentiation of BMSCs was characterized. The results demonstrated that the composite microcarrier had good biocompatibility and was conducive to cell adhesion and proliferation. Moreover, ALP and ARS staining revealed that the addition of OCP significantly enhanced the osteogenic differentiation of BMSCs. These results indicate that the composite microcarrier has promising prospects for bone repair applications.

The Effects of Dietary Protein Level on the Growth Performance, Body Composition, Intestinal Digestion and Microbiota of Litopenaeus vannamei Fed Chlorella sorokiniana as the Main Protein Source.

This study investigated the effect of dietary protein levels on Litopenaeus vannamei. Five isolipid diets with protein levels of 32%, 36%, 40%, 44% and 48% were prepared using C. sorokiniana as the main protein source. L. vannamei (initial body weight 0.83 ± 0.02 g) were fed these five diets for 8 weeks and referred to as the CHL32, CHL36, CHL40, CHL44 and CHL48 groups, respectively. When the feeding trial was finished, the growth performance, body composition, intestinal digestion and microbiota of L. vannamei were studied. The results showed that the maximum weight gain rate (WGR) of L. vannamei was in the CHL40 group while the lowest feed conversion ratio (FCR) was in the CHL48 group. According to the regression analysis using WGR as the evaluation index, the best growth performance of L. vannamei was obtained when the dietary protein level was 40.81%. The crude protein content of whole shrimp showed an increasing and then decreasing trend with increasing dietary protein levels. Furthermore, the L. vannamei muscle amino acid composition was relatively stable and, to some extent, independent of dietary protein levels. Trypsin, lipase and amylase (AMS) activity increased and then decreased with increasing dietary protein levels and, significantly, peaked in the CHL44 group. Analysis of the alpha diversity of the intestinal microbiota showed that the Chao1 index peaked in the CHL40 group and was significantly lower in the CHL48 group. Additionally, the relative abundance of pathogenic bacteria decreased significantly while the relative abundance of beneficial bacteria increased significantly in the intestine of L. vannamei as the dietary protein levels increased. The functional prediction of the intestinal microbiota revealed that dietary protein levels may influence the growth of L. vannamei by regulating various metabolic activities, and the highest WGR in the CHL40 group may have been related to the significant enrichment of nicotinate and nicotinamide metabolism and biotin metabolism functions. In summary, the optimal protein requirement for L. vannamei was around 40% when C. sorokiniana was used as the primary protein source. Too high or too low dietary protein levels could adversely affect shrimp body composition, intestinal digestion and microbiota.

Growth, immunity and transcriptome response to different stocking densities in Litopenaeus vannamei.

The effects of different stocking densities on Litopenaeus vannamei were investigated from the aspects of growth performance, immune response and transcriptome in this experiment. L. vannamei (initial body weight: 0.30 ± 0.02 g) were reared for 8 weeks at three stocking densities of 100 (LSD), 200 (MSD) and 300 (HSD) shrimp/m³, respectively. The results showed that the survival rate (SR), final body weight (FBW), weight gain rate (WGR), specific growth ratio (SGR) and protein efficiency ratio (PER) of L. vannamei significantly decreased, while the feed factor (FCR) significantly increased with the increase of stocking density. After Vibrio parahemolyticus infection, the SR of L. vannamei in the HSD group was significantly lower than that in the LSD and MSD groups. Increasing stocking density significantly increased the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lysozyme (LYS) while significantly decreased the activities of catalase (CAT) and phenol oxidase (PO) in the serum of L. vannamei. Similar changes of the gene expression as the activities of immune enzymes were found in the hemocytes. Pairwise comparison between the LSD, MSD and HSD group in the transcriptome analysis identified that there were 304, 1376 and 2083 differentially expressed genes (DEGs) in LSD vs MSD, MSD vs HSD and LSD vs HSD, respectively. Among them, most of the immune-related DEGs were down-regulated and metabolism-related DEGs were up-regulated with the increasing stocking density. In addition, KEGG enrichment pathway analysis revealed that several immune and metabolic related pathways including PI3K-Akt signaling pathway and AMPK signaling pathway were significantly enriched. Of these, the PI3K-Akt signaling pathway had the most DEGs and was also the most significantly enriched pathway. Furthermore, 16 DEGs (such as FOXO, PCK2 and CTSC, etc.) and partial immune enzyme activity (such as AST, CAT and PO, etc.) changes were closely correlated with the increase of stocking density when partial immune-related DEGs and immune-related enzymes were analyzed jointly. All these results indicated that changes in stocking density had a significant effect on the growth performance, immunity and transcriptome of L. vannamei.

Identification and Characterization of Infectious Pathogens Associated with Mass Mortalities of Pacific Oyster (Crassostrea gigas) Cultured in Northern China.

The Pacific oyster (Crassostrea gigas) aquaculture industry increased rapidly in China with the introduction and promotion of triploid oysters in recent years. Mass mortalities affecting different life stages of Pacific oysters emerged periodically in several important production areas of Northern China. During 2020 and 2021, we conducted a passive two-year investigation of infectious pathogens linked to mass mortality. Ostreid herpesvirus-1 (OsHV-1) was detected to be associated with mass mortalities of hatchery larvae, but not juveniles and adults in the open sea. Protozoan parasites, such as Marteilia spp., Perkinsus spp. and Bonamia spp. were not detected. Bacterial isolation and identification revealed that Vibrio natriegens and Vibrio alginolyticus were the most frequently (9 out of 13) identified two dominant bacteria associated with mass mortalities. Pseudoalteromonas spp. was identified as the dominant bacteria in three mortality events that occurred during the cold season. Further bacteriological analysis was conducted on two representative isolates of V. natriegens and V. alginolyticus, designated as CgA1-1 and CgA1-2. Multisequence analysis (MLSA) showed that CgA1-1 and CgA1-2 were closely related to each other and nested within the Harveyi clade. Bacteriological investigation revealed faster growth, and more remarkable haemolytic activity and siderophore production capacity at 25 °C than at 15 °C for both CgA1-1 and CgA1-2. The accumulative mortalities of experimental immersion infections were also higher at 25 °C (90% and 63.33%) than at 15 °C (43.33% and 33.33%) using both CgA1-1 and CgA1-2, respectively. Similar clinical and pathological features were identified in samples collected during both naturally and experimentally occurring mortalities, such as thin visceral mass, discolouration, and connective tissue and digestive tube lesions. The results presented here highlight the potential risk of OsHV-1 to hatchery production of larvae, and the pathogenic role of V. natriegens and V. alginolyticus during mass mortalities of all life stages of Pacific oysters in Northern China.

Ultrasonic/electrical dual stimulation response nanocomposite bioelectret for controlled precision drug release.

Electret materials have attracted extensive attention because of their permanent polarization and electrostatic effect. However, it is one of problem that needs to be solved in biological application to manipulate the change of surface charge of electret by external stimulation. In this work, a drug-loaded electret with flexibility and no cytotoxicity was prepared under relatively mild conditions. The electret can release the charge through stress change and ultrasonic stimulation, and the drug release can be accurately controlled with the help of ultrasonic and electric double stimulation response. Here, the dipoles like particles of carnauba wax nanoparticles (nCW) are fixed in the matrix based on the interpenetrating polymer network structure, and "frozen" oriented dipolar particles that are treated by thermal polarization and cooled at high field strength. Subsequently, the charge density of the prepared composite electret can reach 101.1 â€‹nC/m2 at the initial stage of polarization and 21.1 â€‹nC/m2 after 3 weeks. In addition, the stimulated change of electret surface charge flow under cyclic tensile stress and cyclic compressive stress can generate a current of 0.187 â€‹nA and 0.105 â€‹nA at most. The ultrasonic stimulation results show that when the ultrasonic emission power was 90% (Pmax â€‹= â€‹1200 â€‹W), the current of 0.472 â€‹nA can be generated. Finally, the drug release characteristics and biocompatibility of the nCW composite electret containing curcumin were tested. The results showed that it not only had the ability to accurately control the release by ultrasound, but also triggered the electrical effect of the material. The prepared drug loaded composite bioelectret provides a new way for the construction, design and testing of the bioelectret. Its ultrasonic and electrical double stimulation response can be accurately controlled and released as required, and it has broad application prospects.

The controlled degradation of bacterial cellulose in simulated physiological environment by immobilization and release of cellulase.

Bacterial cellulose (BC) has good network structure, biocompatibility, and excellent mechanical properties, and is widely used in the field of biomaterials. The controllable degradation of BC can further broaden its application. Oxidative modification and cellulases may endow BC with degradability, but these methods inevitably lead to the obvious reduction of its initial mechanical properties and uncontrolled degradation. In this paper, the controllable degradation of BC was realized for the first time by using a new controlled release structure that combines the immobilization and release of cellulase. The immobilized enzyme has higher stability and is gradually released in the simulated physiological environment, and its load can control the hydrolysis rate of BC well. Furthermore, the BC-based membrane prepared by this method retains the favorable physicochemical performance of the original BC, including flexibility and great biocompatibility, and holds good application prospects in drug control release or tissue repair.

Fabrication of Cu2+-loaded phase-transited lysozyme nanofilm on bacterial cellulose: Antibacterial, anti-inflammatory, and pro-angiogenesis for bacteria-infected wound healing.

Bacterial overgrowth in injured wounds causes wound infection and excessive inflammation, leading to delayed wound healing. Successful treatment of delayed infected wound healing demands dressings, which can inhibit bacterial growth and inflammation and simultaneously induce vascularization, collagen deposition, and re-epithelialization of wounds. In this study, bacterial cellulose (BC) deposited with Cu2+-loaded phase-transited lysozyme (PTL) nanofilm (BC/PTL/Cu) was prepared for healing infected wounds. The results confirm that PTL were successfully self-assembled on BC matrix, and Cu2+ were loaded into PTL through electrostatic coordination. The tensile strength and the elongation at break of the membranes were not significantly changed after modification with PTL and Cu2+. Compared with BC, the surface roughness of BC/PTL/Cu significantly increased while the hydrophilicity decreased. Moreover, BC/PTL/Cu displayed slower release rate of Cu2+ compared with BC directly loaded with Cu2+. BC/PTL/Cu exhibited good antibacterial activity against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, and Pseudomonas aeruginosa. By controlling copper concentration, BC/PTL/Cu were not cytotoxic to mouse fibroblast cell line L929. In vivo, BC/PTL/Cu accelerated wound healing and promoted re-epithelialization, collagen deposition, and angiogenesis while inhibiting inflammation of the infected full-thickness skin wounds of rats. Collectively, these results demonstrate that BC/PTL/Cu composites are promising dressings for healing infected wounds.

Injectable self-assembled dual-crosslinked alginate/recombinant collagen-based hydrogel for endometrium regeneration.

The disadvantages of mainstream therapies for endometrial injury are difficult to resolve, herein, we suggest an omnibearing improvement strategy by introducing an injectable multifunctional self-assembled dual-crosslinked sodium alginate/recombinant collagen hydrogel. The hydrogel possessed a reversible and dynamic double network based on dynamic covalent bonds and ionic interactions, which also contributed to excellent capability in viscosity and injectability. Moreover, it was also biodegradable with a suitable speed, giving off active ingredients during the degradation process and eventually disappearing completely. In vitro tests exhibited that the hydrogel was biocompatible and able to enhance endometrial stromal cells viability. These features synergistically promoted cell multiplication and maintenance of endometrial hormone homeostasis, which accelerated endometrial matrix regeneration and structural reconstruction after severe injury in vivo. Furthermore, we explored the interrelation between the hydrogel characteristics, endometrial structure, and postoperative uterine recovery, which would benefit deep research on regulation of uterine repair mechanism and optimization of hydrogel materials. The injectable hydrogel could achieve favourable therapeutic efficacy without the need of exogenous hormones or cells, which would be of clinical value in endometrium regeneration.