Enzyme-Activated Biomimetic Vesicles Confining Mineralization for Bone Maturation.

Inspired by the crucial role of matrix vesicles (MVs), a series of biomimetic vesicles (BVs) fabricated by calcium glycerophosphate (CaGP) modified polyurethane were designed to mediate the mineralization through in situ enzyme activation for bone therapy. In this study, alkaline phosphatase (ALP) was harbored in the porous BVs by adsorption (Ad-BVs) or entrapment (En-BVs). High encapsulation of ALP on En-BVs was effectively self-activating by calcium ions of CaGP-modified PU that specifically hydrolyzed the organophosphorus (CaGP) to inorganic phosphate, thus promoting the formation of the highly oriented bone-like apatite in vitro. Enzyme-catalyzed kinetics confirms the regulation of apatite crystallization by the synergistic action of self-activated ALP and the confined microcompartments of BVs. This leads to a supersaturated microenvironment, with the En-BVs group exhibiting inorganic phosphate (Pi) levels 4.19 times higher and Ca2+ levels 3.67 times higher than those of simulated body fluid (SBF). Of note, the En-BVs group exhibited excellent osteo-inducing differentiation of BMSCs in vitro and the highest maturity with reduced bone loss in rat femoral defect in vivo. This innovative strategy of biomimetic vesicles is expected to provide valuable insights into the enzyme-activated field of bone therapy.

Interaction-Based Perspective for Designing Polymer Biomaterial: A Strategic Approach to the Chitosan-Glycerophosphate System.

The conventional approach for developing any polymeric biomaterial is to follow protocols available in the literature and/or perform trial-and-error runs without a scientific basis. Here, we propose an analysis of a complex overlay of molecular interactions between drugs and polymers that provides a strategic pathway for biomaterial development. First, this work provides an innovative interaction-based method for developing an ocular formulation involving in situ gelling chitosan, gelatin, and glycerophosphate systems. A systematic interaction study is conducted based on the measurement of hydrodynamic radius, zeta potential, and viscosity with the sequential addition of formulation components. The increase in the hydrodynamic radius of the polymer with the addition of drugs can be interpreted as better diffusion of the drug inside the charged polymer chains and vice versa. Based on the knowledge of these interactions, a formulation has been designed that shows better drug release results with extended and sustained release compared to literature protocols, hence accentuating the importance of this study. An in-depth analysis of interactions can lead to a better understanding of the system. Second, we demonstrate the development of two dual-drug biomaterial systems, i.e., an in situ gelling and a liquid formulation at ocular surface temperature from the same polymers, which can be used as an ocular antiglaucoma formulation. Prior knowledge of the interactions between the drug polymers can be used to design a better formulation. The demonstrated application of this interaction-based protocol development can be extended universally to any biomaterial. This would provide a comprehensive idea about the properties and interactions of polymers and drugs, which can also serve as a base/starting point for a new formulation/biomaterial development.

A Thermoresponsive injectable drug delivery system of chitosan/ß-glycerophosphate with gellan gum/alginate microparticles.

The development of new Drug Delivery Systems (DDS) by incorporating microparticles within hydrogels can prolong the release rate of drugs and/or other bioactive agents. In this study, we combined gellan gum/alginate microparticles within a thermoresponsive chitosan (Ch) hydrogel with ß-Glycerophosphate (ß-GP), designing the system to be in the sol state at 21 °C and in the gel state at 37 °C to enable the injectability of the system. The system was in the sol state between 10 °C and 21 °C. Higher concentrations of ß-GP (0, 2, 3, 4, 5 w/v%) and microparticles (0, 2 and 5 w/v%) allowed a faster sol-gel transition with higher mechanical strength at 37 °C. However, the sol-gel transition was not instantaneous. The release profile of methylene blue (MB) from the microparticles was significantly affected by their incorporation in Ch/ß-GP hydrogels, only allowing the release of 60-70 % of MB for 6 days, while the microparticles alone released all the MB in 48 h. The proposed system did not present cytotoxicity to VERO cell lines as a preliminary assay, with the Ch/ß-GP/GG:Alg having >90 % of cellular viability. The proposed Ch/ß-GP system proved to have a delaying effect on drug release and biocompatible properties, being a promising future DDS.

Lipoteichoic acid composed of poly-glycerolphosphate containing l-lysine and involved in immunoglobulin A-inducing activity in Apilactobacillus genus.

Lipoteichoic acid (LTA) in the gram-positive bacterial cell wall acts as an immunomodulatory factor in host cells. The chemical structures vary among bacterial species and strains, and may be related to biological activities. In our previous work, much higher immunoglobulin A (IgA)-inducing activity was observed in cells of the Apilactobacillus genus (Apilactobacillus kosoi 10HT, Apilactobacillus apinorum JCM 30765T, and Apilactobacillus kunkeei JCM 16173T) than other lactic acid bacteria, and their LTA was responsible for the activity. In the present study, we elucidated the chemical structures of LTA from these Apilactobacillus strains to explore the structure-function relationship of the IgA-inducing activity. The 1H-nuclear magnetic resonance spectra suggested that their LTA structures were similar. All have a poly-glycerolphosphate main chain, which comprised 12 to 20 average number of the repeating units, with partial substitutions of glucose(α1-, glucosyl(α1-2)glucose(α1- (α-linked-kojibiose), and l-lysine at the C-2 hydroxy group of the glycerol residue. l-Lysine is a substituent never seen before in LTA, and is a probable characteristic of the Apilactobacillus genus. Removal of l-lysine residue from LTA by mild alkaline treatment decreased IgA induction in murine Peyer's patch experiments. The novel l-lysine residue in Apilactobacillus LTA plays a crucial role in the remarkably high IgA-inducing activity.

Preparation and Performance Evaluation of a Zinc Oxide-Graphene Oxideloaded Chitosan-Based Thermosensitive Gel.

This study aimed to develop and assess a chitosan biomedical antibacterial gel ZincOxide-GrapheneOxide/Chitosan/ß-Glycerophosphate (ZnO-GO/CS/ß-GP) loaded with nano-zinc oxide (ZnO) and graphene oxide (GO), known for its potent antibacterial properties, biocompatibility, and sustained drug release. ZnO nanoparticles (ZnO-NPs) were modified and integrated with GO sheets to create 1% and 3% ZnO-GO/CS/ß-GP thermo-sensitive hydrogels based on ZnO-GO to Chitosan (CS) mass ratio. Gelation time, pH, structural changes, and microscopic morphology were evaluated. The hydrogel's antibacterial efficacy against Porphyromonas gingivalis, biofilm biomass, and metabolic activity was examined alongside its impact (MC3T3-e1). The findings of this study revealed that both hydrogel formulations exhibited temperature sensitivity, maintaining a neutral pH. The ZnO-GO/CS/ß-GP formulation effectively inhibited P. gingivalis bacterial activity and biofilm formation, with a 3% ZnO-GO/CS/ß-GP antibacterial rate approaching 100%. MC3T3-e1 cells displayed good biocompatibility when cultured in the hydrogel extract.The ZnO-GO/CS/ß-GP thermo-sensitive hydrogel demonstrates favorable physical and chemical properties, effectively preventing P. gingivalis biofilm formation. It exhibits promising biocompatibility, suggesting its potential as an adjuvant therapy for managing and preventing peri-implantitis, subject to further clinical investigations.

Injectable and Thermosensitive Hydrogel with Platelet-Rich Plasma for Enhanced Biotherapy of Skin Wound Healing.

The rapid and effective healing of skin wounds resulted from severe injuries and full-layer skin defects remains a pressing clinical challenge in contemporary medical practice. The reduction of wound infection and rapid healing is helpful to rebuild and repair skin tissue. Here, a thermosensitive chitosan-based wound dressing hydrogel incorporating ß-glycerophosphate (GP), hydroxy propyl cellulose (HPC), graphene oxide (GO), and platelet-rich plasma (PRP) is developed, which exhibits the dual functions of antibacterial properties and repair promotion. GP and HPC enhance the mechanical properties through forming hydrogen bonding connection, while GO produces local heat under near-infrared light, leading to improved blood circulation and skin recovery. Notably, antibacterial properties against Pseudomonas aeruginosa, and control-release of growth factors from PRP are also achieved based on the system. In vitro experiments reveal its biocompatibility, and ability to promote cell proliferation and migration. Animal experiments demonstrate that the epithelial repair and collagen deposition can be promoted during skin wound healing in Sprague Dawley rats. Moreover, a reduction in wound inflammation levels and the improvement of wound microenvironment are observed, collectively fostering effective wound healing. Therefore, the composite hydrogel system incorporated with GO and PRP can be a promising dressing for the treatment of skin wounds.

Optimization of thermoresponsive chitosan/ß-glycerophosphate hydrogels for injectable neural tissue engineering application.

Regeneration of neural tissue and recovery of lost functions following an accident or disease to the central nervous system remains a major challenge worldwide, with limited treatment options available. The main reason for the failure of conventional therapeutic techniques to regenerate neural tissue is the presence of blood-brain barrier separating nervous system from systemic circulation and the limited capacity of self-regeneration of the nervous system. Injectable hydrogels have shown great promise for neural tissue engineering given their suitability for minimally invasive in situ delivery and tunable mechanical and biological properties. Chitosan (CS)/ß-glycerophosphate (ß-GP) hydrogels have been extensively investigated and shown regenerative potential in a wide variety of tissues such as bone and cartilage tissue engineering. However, the potential of CS/ß-GP hydrogels has never been tested for injectable neural tissue engineering applications. In the present study, CS/ß-GP hydrogels, consisting of 0.5-2% CS and 2-3% ß-GP, were prepared and characterized to investigate their suitability for injectable neural tissue engineering applications. The resulting CS/ß-GP-hydrogels showed a varying range of properties depending on the CS/ß-GP blend ratio. In particular, the 0.5%:3% and 0.75%:3% CS/ß-GP hydrogels underwent rapid gelation (3 min and 5 min, respectively) at physiological temperature (37 °C) and pH (7.4). They also had suitable porosity, osmolality, swelling behavior and biodegradation for tissue engineering. The biocompatibility of hydrogels was determined in vitro using PC12 cells, an immortalized cell line with neuronal cell-like properties, revealing that these hydrogels supported cell growth and proliferation. In conclusion, the thermoresponsive 0.5%:3% and 0.75%:3% CS/ß-GP hydrogels had the greatest potential for neural tissue engineering.

Efficacy and safety of a thermosensitive hydrogel for endoscopic submucosal dissection: An in vivo swine study.

Injectable thermo-sensitive chitosan hydrogels have recently been developed for the use of submucosal fluids in endoscopic submucosal dissections (ESD). This study aimed to investigate the efficacy and safety of chitosan hydrogels during ESD. Submucosal fluids were administered as follows: 0.9% normal saline (NS), 0.4% hyaluronic acid (HA) and chitosan/ß-glycerophosphate (CS/GP) hydrogel. Each solution was administered twice into the stomach and colon of a pig, with a total of 72 ESD procedures performed on 12 pigs. The injected volume and procedure-related parameters were recorded and analyzed. ESDs that created ulcers after 7 days were histologically compared. All ESD specimens were resected en bloc. The total injected volumes during ESD of the stomach (NS, 16.09±3.27 vs. HA, 11.17±2.32 vs. CS/GP, 9.44±2.33; p<0.001) and colon (NS, 9.17±1.80 vs. HA, 6.67±1.50 vs. CS/GP, 6.75±1.57; p = 0.001) were significantly different. Hydrogel showed significant differences from normal saline in terms of fluid power (mm2/vol; NS, 35.70±9.00 vs. CS/GP 57.48±20.77; p = 0.001) and consumption rate (vol/min; NS, 2.59±0.86 vs. CS/GP, 1.62±0.65; p = 0.013) in the stomach. Histological examination revealed preserved muscularis propria, although the chitosan hydrogel resulted in a partial inflammatory response, with a hypertrophied submucosal layer. Chitosan hydrogel was found to be superior to normal saline, with an efficacy similar to that of hyaluronic acid. Nonetheless, long-term histological changes should be evaluated before clinical implementation.

Biosynthetic Mechanisms and Biological Significance of Glycerol Phosphate-Containing Glycan in Mammals.

Bacteria contain glycerol phosphate (GroP)-containing glycans, which are important constituents of cell-surface glycopolymers such as the teichoic acids of Gram-positive bacterial cell walls. These glycopolymers comprising GroP play crucial roles in bacterial physiology and virulence. Recently, the first identification of a GroP-containing glycan in mammals was reported as a variant form of O-mannosyl glycan on α-dystroglycan (α-DG). However, the biological significance of such GroP modification remains largely unknown. In this review, we provide an overview of this new discovery of GroP-containing glycan in mammals and then outline the recent progress in elucidating the biosynthetic mechanisms of GroP-containing glycans on α-DG. In addition, we discuss the potential biological role of GroP modification along with the challenges and prospects for further research. The progress in this newly identified glycan modification will provide insights into the phylogenetic implications of glycan.

Calcium glycerophosphate and fluoride affect the pH and inorganic composition of dual-species biofilms of Streptococcus mutans and Candida albicans.

OBJECTIVES: This study evaluated the influence of calcium glycerophosphate (CaGP), combined with or without fluoride (F), on the pH and concentrations of F, Ca, and P of dual-species biofilms of Streptococcus mutans and Candida albicans, with or without exposure to sucrose. METHODS: The biofilms (n = 9) received three treatments (72, 78, and 96 h after the start of their formation) at three CaGP concentrations (0.125, 0.25, or 0.5%), with or without F at 500 ppm (as NaF). Solutions containing 500 and 1100 ppm F and artificial saliva were also tested as controls. Biofilm pH was measured, and the concentrations of F, Ca, P, and CaGP were determined (solid and fluid phases). In a parallel experiment, after the third treatment, the treated biofilms were exposed to a sucrose solution, and the pH of the medium, F, Ca, P, and CaGP was determined. Data were subjected to two-way ANOVA, followed by Fisher's LSD test (p < 0.05). RESULTS: Treatment with CaGP and 500 ppm F led to the highest pH values and F and Ca concentrations in the biofilm biomass, both with and without sucrose exposure. CaGP without F led to higher Ca and P concentrations in the biofilm fluid. CONCLUSIONS: CaGP increased F, Ca, and P concentrations in the biofilm, and its presence promoted an increase in the pH of the medium, even after exposure to sucrose. CLINICAL SIGNIFICANCE: The present results elucidate the mechanism by which CaGP and F act on biofilms, further interfering with dental caries dynamics.

Instant hydrogelation encapsulates drugs onto implants intraoperatively against osteoarticular tuberculosis.

Osteoarticular Tuberculosis (TB) is a challenging issue because of its chronicity and recurrence. Many drug delivery systems (DDSs) have been developed for general chemotherapy. Herein, we take advantage of instant hydrogelation to in situ encapsulate drugs onto implants intraoperatively, optimizing the drug release profile against osteoarticular TB. First-line chemodrugs, i.e. rifampicin (RFP) and isoniazid (INH) are firstly loaded on tricalcium phosphate (TCP). Then, the encapsulating hydrogel is fabricated by dipping in chitosan (CS) and ß-glycerophosphate (ß-GP) solution and heating at 80 °C for 40 min. The hydrogel encapsulation inhibits explosive drug release initially, but maintains long-term drug release (INH, 158 days; RFP, 53 days) in vitro. Therefore, this technique could inhibit bone destruction and inflammation from TB effectively in vivo, better than our previous ex situ prepared DDSs. The encapsulating technology, i.e. instant hydrogelation of drug-loaded implants, shows potential for regulating the type and ratio of drugs, elastic and viscous modulus of the hydrogel according to the state of illness intraoperatively for optimal drug release.

Epitope Recognition of a Monoclonal Antibody Raised against a Synthetic Glycerol Phosphate Based Teichoic Acid.

Glycerol phosphate (GroP)-based teichoic acids (TAs) are antigenic cell-wall components found in both enterococcus and staphylococcus species. Their immunogenicity has been explored using both native and synthetic structures, but no details have yet been reported on the structural basis of their interaction with antibodies. This work represents the first case study in which a monoclonal antibody, generated against a synthetic TA, was developed and employed for molecular-level binding analysis using TA microarrays, ELISA, SPR-analyses, and STD-NMR spectroscopy. Our findings show that the number and the chirality of the GroP residues are crucial for interaction and that the sugar appendage contributes to the presentation of the backbone to the binding site of the antibody.

Chitosan thermosensitive hydrogels based on lyophilizate powders demonstrate significant potential for clinical use in endoscopic submucosal dissection procedures.

The goal of this study was to develop intraoperative biomaterials for use in endoscopic submucosal dissection (ESD) procedures that are stable during storage, easy to use, and effective in clinical practice. Therefore, injectable thermosensitive hydrogels were developed based on lactobionic acid-modified chitosan/chitosan/ß-glycerophosphate (CSLA/CS/GP) hydrogel lyophilizate powders, and their properties were compared with original hydrogels that had not been freeze-dried. The results indicated that the lyophilizate powders retained their thermosensitive properties, and gels could be formed within 5 min at 37 °C. Compared to the original hydrogels, the injectability of the hydrogels derived from lyophilizate powders increased significantly. These novel materials maintained their original porous network lamellar structure but exhibited improved mechanical strength and tissue adhesion. Their application with L929 and GES-1 cells revealed that the lyophilizate powder hydrogels demonstrated good cytocompatibility and clearly protected the cells in an acidic environment. The results of submucosal injection experiments involving porcine stomach tissue indicated that the heights of the cushions created by CSLA/CS/GP lyophilizate powder hydrogels lasted longer than those generated with normal saline. The thermosensitive hydrogels based on lyophilizate powders may contribute to practical clinical applications involving ESD, and may also have potential value for other applications in the digestive tract.

Physicochemical and Antimicrobial Properties of Thermosensitive Chitosan Hydrogel Loaded with Fosfomycin.

Thermosensitive chitosan hydrogels-renewable, biocompatible materials-have many applications as injectable biomaterials for localized drug delivery in the treatment of a variety of diseases. To combat infections such as Staphylococcus aureus osteomyelitis, localized antibiotic delivery would allow for higher doses at the site of infection without the risks associated with traditional antibiotic regimens. Fosfomycin, a small antibiotic in its own class, was loaded into a chitosan hydrogel system with varied beta-glycerol phosphate (ß-GP) and fosfomycin (FOS) concentrations. The purpose of this study was to elucidate the interactions between FOS and chitosan hydrogel. The Kirby Bauer assay revealed an unexpected concentration-dependent inhibition of S. aureus, with reduced efficacy at the high FOS concentration but only at the low ß-GP concentration. No effect of FOS concentration was observed for the planktonic assay. Rheological testing revealed that increasing ß-GP concentration increased the storage modulus while decreasing gelation temperature. NMR showed that FOS was removed from the liquid portion of the hydrogel by reaction over 12 h. SEM and FTIR confirmed gels degraded and released organophosphates over 5 days. This work provides insight into the physicochemical interactions between fosfomycin and chitosan hydrogel systems and informs selection of biomaterial components for improving infection treatment.

Influence of Glycerophosphate Salt Solubility on the Gelation Mechanism of Colloidal Chitosan Systems.

Recently, thermosensitive chitosan systems have attracted the interest of many researchers due to their growing application potential. Nevertheless, the mechanism of the sol-gel phase transition is still being discussed, and the glycerophosphate salt role is ambiguous. The aim of the work is to analyze the possibility of the exclusive use of a non-sodium glycerophosphate salt and to determine its impact on the gelation conditions determined by rheological and turbidimetric measurements as well as the stability of the systems by measuring changes in the Zeta potential value. It was found that ensuring the same proportions of glycerophosphate ions differing in cation to amino groups present in chitosan chains, leads to obtaining systems significantly different in viscoelastic properties and phase transition conditions. It was clearly shown that the systems with the calcium glycerophosphate, the insoluble form of which may constitute additional aggregation nuclei, undergo the gelation the fastest. The use of magnesium glycerophosphate salt delays the gelation due to the heat-induced dissolution of the salt. Thus, it was unequivocally demonstrated that the formulation of the gelation mechanism of thermosensitive chitosan systems based solely on the concentration of glycerophosphate without discussing its type is incorrect.

Enhanced Production of Photosynthetic Pigments and Various Metabolites and Lipids in the Cyanobacteria Synechocystis sp. PCC 7338 Culture in the Presence of Exogenous Glucose.

Synechocystis strains are cyanobacteria that can produce useful biomaterials for biofuel and pharmaceutical resources. In this study, the effects of exogenous glucose (5-mM) on cell growth, photosynthetic pigments, metabolites, and lipids in Synechocystis sp. PCC 7338 (referred to as Synechocystis 7338) were investigated. Exogenous glucose increased cell growth on days 9 and 18. The highest production (mg/L) of chlorophyll a (34.66), phycocyanin (84.94), allophycocyanin (34.28), and phycoerythrin (6.90) was observed on day 18 in Synechocystis 7338 culture under 5-mM glucose. Alterations in metabolic and lipidomic profiles under 5-mM glucose were investigated using gas chromatography-mass spectrometry (MS) and nanoelectrospray ionization-MS. The highest production (relative intensity/L) of aspartic acid, glutamic acid, glycerol-3-phosphate, linolenic acid, monogalactosyldiacylglycerol (MGDG) 16:0/18:1, MGDG 16:0/20:2, MGDG 18:1/18:2, neophytadiene, oleic acid, phosphatidylglycerol (PG) 16:0/16:0, and PG 16:0/17:2 was achieved on day 9. The highest production of pyroglutamic acid and sucrose was observed on day 18. We suggest that the addition of exogenous glucose to Synechocystis 7338 culture could be an efficient strategy for improving growth of cells and production of photosynthetic pigments, metabolites, and intact lipid species for industrial applications.

Effect of dexamethasone as osteogenic supplementation in in vitro osteogenic differentiation of stem cells from human exfoliated deciduous teeth.

In in vitro culture systems, dexamethasone (DEX) has been applied with ascorbic acid (ASC) and ß-glycerophosphate (ßGLY) as culture media supplementation to induce osteogenic differentiation of mesenchymal stem cells. However, there are some inconsistencies regarding the role of DEX as osteogenic media supplementation. Therefore, this study verified the influence of DEX culture media supplementation on the osteogenic differentiation, especially the capacity to mineralize the extracellular matrix of stem cells from human exfoliated deciduous teeth (SHED). Five groups were established: G1-SHED + Dulbecco's Modified Eagles' Medium (DMEM) + fetal bovine serum (FBS); G2-SHED + DMEM + FBS + DEX; G3-SHED + DMEM + FBS + ASC + ßGLY; G4-SHED + DMEM + FBS + ASC + ßGLY + DEX; G5-MC3T3-E1 + α Minimal Essential Medium (MEM) + FBS + ASC + ßGLY. DNA content, alkaline phosphatase (ALP) activity, free calcium quantification in the extracellular medium, and extracellular matrix mineralization quantification through staining with von Kossa, alizarin red, and tetracycline were performed on days 7 and 21. Osteogenic media supplemented with ASC and ß-GLY demonstrated similar effects on SHED in the presence or absence of DEX for DNA content (day 21) and capacity to mineralize the extracellular matrix according to alizarin red and tetracycline quantifications (day 21). In addition, the presence of DEX in the osteogenic medium promoted less ALP activity (day 7) and extracellular matrix mineralization according to the von Kossa assay (day 21), and more free calcium quantification at extracellular medium (day 21). In summary, the presence of DEX in the osteogenic media supplementation did not interfere with SHED commitment into mineral matrix depositor cells. We suggest that DEX may be omitted from culture media supplementation for SHED osteogenic differentiation in vitro studies.

Exploration of key residues and conformational change of anti-terminator protein GlpP for ligand and RNA binding.

Anti-terminator protein GlpP regulates gene expression of glycerol uptake operon at post-transcriptional level in a number of bacteria. By now, the molecular dynamics details of ligand and RNA binding by GlpP are still obscure. In this study, we employed the molecular dynamic (MD) simulation and constructed a functional verification platform of GlpP to resolve these puzzles. By combining molecular docking, MD simulation and alanine scanning mutagenesis, a ligand binding pocket consisting of R14, R104 and R157 was identified. Among these residues with positive charge, R14 was dominant for binding glycerol-3-phosphate (G3P). Moreover, the "parallel to crossed" conformational change of the predicted RNA binding region was observed in MD simulation. In this process, the interaction between R104 and E129 was crucial to trigger the conformational change. To further verify this speculation, three ligand independent mutants were obtained by error-prone PCR. The MD simulation indicated that the conformational change happened in all the three mutants, confirming the "parallel to crossed" conformational change endowed GlpP the activity of binding RNA. In recent years, as a potable biological part, anti-terminator was more and more widely used to regulate gene expression in metabolic engineering and synthetic biology. The work in this study deepened our understanding to the typical anti-terminator GlpP, contributing to the further engineering and application of this type of regulator.

Hidden complexity in membrane permeabilization behavior of antimicrobial polycations.

A promising alternative to classical antibiotics are antimicrobial peptides and their synthetic mimics (smAMPs) that supposedly act directly on membranes. For a more successful design of smAMPs, we need to know how the type of interaction with the membrane determines the type of membrane perturbation. How this, in turn, transfers into selectivity and microbial killing activity is largely unknown. Here, we characterize the action of two smAMPs: MM:CO (a copolymer of hydrophobic cyclooctyl subunits and charged ß-monomethyl-α-aminomethyl subunits) and the highly charged poly-NM (a homopolymer of α-aminomethyl subunits). By thorough characterization of vesicle leakage experiments, we elucidate complex membrane perturbation behavior in zwitterionic or negatively charged vesicles. Vesicle leakage data does not entirely agree with the growth inhibition of microbes. Our ensemble of advanced membrane permeabilization approaches clarifies these discrepancies. Long cumulative leakage kinetics show that the two smAMPs act either by transient leakage or by rare stochastic leakage events that occur at charge neutralization in the sample. We determine the strengths of individual leakage events induced by the smAMPs in membranes of various compositions. These strengths indicate changes in leakage mechanism over time and concentration range. Thus, our sophisticated analysis of vesicle leakage experiments reveals a fine-tuned flexibility in membrane permeabilization mechanisms. These details are indispensable in judging and designing membrane-active compounds.

Catechol functionalized chitosan/active peptide microsphere hydrogel for skin wound healing.

Chitosan-based thermosensitive hydrogels have been widely used in drug delivery and tissue engineering, but their poor bioactivity has limited their further applications. Integral active oyster peptide microspheres (OPM) with an average particle diameter of 3.9 µm were prepared with high encapsulation efficiency (72.8%) and loading capacity (11.9%), exhibiting desirable sustained release effects. Using catechol functionalized chitosan (CS-C) as the polymeric matrix, OPM as the filler, and ß-sodium glycerophosphate (ß-GP) as a thermal sensitizer, the thermosensitive hydrogel CS-C/OPM/ß-GP was prepared. Besides, the application of the hydrogel on wound healing was studied, and its biosafety was evaluated. The results of cell migration in vitro showed that the cell migration rate of CS-C/OPM/ß-GP reached 97.47 ± 5.41% within 48 h, indicating that the hydrogel accelerated the migration of L929 cells. As demonstrated in the mouse skin wound experiment, CS-C/OPM/ß-GP hydrogel not only inhibited the aggregation of diversified inflammatory cells and accelerated the generation of collagen fibers and new blood vessels of the wound, but also enhanced the synthesis of total protein (TP) in granulation tissue, and up-regulated the expression of Ki-67 and VEGF in the injury, thereby achieving fast wound healing. Safety evaluation results showed that CS-C/OPM/ß-GP hydrogel was not cytotoxic to L929 cells, and the hemolysis ratio was less than 5% within 1 mg/mL. In conclusion, CS-C/OPM/ß-GP hydrogel is expected as a promising medical dressing for wound healing.