Polylysine for skin regeneration: A review of recent advances and future perspectives

Activity and safety evaluation of natural preservatives

Synthetic preservatives are widely used in the food industry to control spoilage and growth of pathogenic microorganisms, inhibit lipid oxidation processes and extend the shelf life of food. However, synthetic preservatives have some side effects that can lead to poisoning, cancer and other degenerative diseases. With the improvement of living standards, people are developing safer natural preservatives to replace synthetic preservatives, including plant derived preservatives (polyphenols, essential oils, flavonoids), animal derived preservatives (lysozyme, antimicrobial peptide, chitosan) and microorganism derived preservatives (nisin, natamycin, ε-polylysine, phage). These natural preservatives exert antibacterial effects by disrupting microbial cell wall/membrane structures, interfering with DNA/RNA replication and transcription, and affecting protein synthesis and metabolism. This review summarizes the natural bioactive compounds (polyphenols, flavonoids and terpenoids, etc.) in these preservatives, their antioxidant and antibacterial activities, and safety evaluation in various products.

Regiocontrol of the Bulk Polymerization of Lysine Ethyl Ester by the Selection of Suitable Immobilized Enzyme Catalysts

The development of a green and facile method for the controlled synthesis of functional polypeptides is desired for sustainable material applications. In this study, the regioselective synthesis of poly(l-lysine) (polyLys) via enzyme-catalyzed aminolysis was achieved by bulk polymerization of l-lysine ethyl ester (Lys-OEt) using immobilized Candida antarctica lipase Novozym 435 (IM-lipase) or trypsin (IM-trypsin). Structural characterization of the obtained polyLys revealed that IM-lipase resulted solely in ε-linked amide bond formation, whereas IM-trypsin predominantly provided α-linked polyLys. Optimization of the conditions for the bulk polymerization using immobilized enzymes resulted in high monomer conversion and a high degree of polymerization, with excellent regioselectivity. Molecular docking simulations revealed different binding conformations of Lys-OEt to the catalytic pockets of lipase and trypsin, which putatively resulted in different amino moieties being used for amide bond formation. The immobilized enzymes were recovered and recycled for bulk polymerization, and the initial activity was maintained in the case of IM-trypsin. The obtained α- and ε-linked polyLys products exhibited different degradability against proteolysis, demonstrating the possibility of versatile applications as sustainable materials. This enzymatic regioregular control enabled the synthesis of well-defined polypeptide-based materials with a diverging structural variety.

A rapid interactive chitosan-based medium with antioxidant and pro-vascularization properties for infected burn wound healing

Large-pore hydrogels are better suited to meet the management needs of nutrient transportation and gas exchange between infected burn wounds and normal tissues. However, better construction strategies are required to balance the pore size and mechanical strength of hydrogels to construct a faster substance/gas interaction medium between tissues. Herein, we developed spongy large pore size hydrogel (CS-TA@Lys) with good mechanical properties using a simple ice crystal-assisted method based on chitosan (CS), incorporating tannic acid (TA) and ε-polylysine (Lys). A large-pore and mechanically robust hydrogel medium was constructed based on hydrogen bonding between CS molecules. On this basis, a pro-restorative functional platform with antioxidation and pro-vascularization was constructed using TA and Lys. In vitro experiments displayed that the CS-TA@Lys hydrogel possessed favorable mechanical properties and fast interaction performances. In addition, the CS-TA@Lys hydrogel possessed the capacity to remove intra/extracellular reactive oxygen species (ROS) and possessed antimicrobial and pro-angiogenic properties. In vivo experiments displayed that the CS-TA@Lys hydrogel inhibited wound inflammation and promoted wound vascularization. In addition, the CS-TA@Lys hydrogel showed the potential for rapid hemostasis. This study provides a potential functional wound dressing with rapid interaction properties for skin wound repair.

Mimicking the Physicochemical Properties of the Cornea: A Low-Cost Approximation Using Highly Available Biopolymers

Corneal diseases represent a significant global health challenge, often resulting in blindness, for which penetrating keratoplasty is the clinical gold standard. However, in cases involving compromised ocular surfaces or graft failure, osteo-odonto keratoprosthesis (OOKP) emerges as a vital yet costly and complex alternative. Thus, there is an urgent need to introduce soft biomaterials that mimic the corneal tissue, considering its translation's physicochemical, biological, and economic costs. This study introduces a cross-linked mixture of economically viable biomaterials, including gelatin, chitosan, and poly-D-lysine, that mimic corneal properties. The physicochemical evaluation of certain mixtures, specifically gelatin, chitosan, and poly-D-lysine cross-linked with 0.10% glutaraldehyde, demonstrates that properties such as swelling, optical transmittance, and thermal degradation are comparable to those of native corneas. Additionally, constructs fabricated with poly-D-lysine exhibit good cytocompatibility with fibroblasts at 72 h. These findings suggest that low-cost biopolymers, particularly those incorporating poly-D-lysine, mimic specific corneal characteristics and have the potential to foster fibroblast survival. While further studies are required to reach a final corneal-mimicking solution, this study contributes to positioning low-cost reagents as possible alternatives to develop biomaterials with physicochemical properties like those of the human cornea.

Antibacterial, ROS scavenging and angiogenesis promotingϵ-Polylysine/gelatin based hydrogel containing CTLP to regulate macrophages for pressure ulcer healing

Pressure ulcers (PUs) have emerged as a substantial burden on individuals and society. The introduction of innovative dressings that facilitate the healing of pressure ulcer wounds represents a cost-effective alternative for treatment. In this study, the emphasis is on the preparation of Carthamus tinctorius L. polysaccharide (CTLP) as hydrogel microspheres (MPs), which are then encapsulated within a hydrogel matrix crosslinked with phenylboronic acid gelatin (Gelatin-PBA) andϵ-polylysine-grafted catechol (ϵ-PL-Cat) to enable sustained release for promoting pressure ulcer healing. The presented Gelatin-PBA/ϵ-PL-Cat (GPL)/CTLP-MPs hydrogel demonstrated outstanding self-healing properties. In addition,in vitroexperiments revealed that the hydrogel exhibited remarkable antibacterial activity, excellent biocompatibility. And it showed the capacity to promote vascular formation, effectively scavenge reactive oxygen species, and facilitate macrophage polarization from the M1 to M2 phenotype.In vivowound healing of mice PUs indicated that the prepared GPL/CTLP-MPs hydrogel effectively accelerated the formation of granulation tissue and facilitated the healing of the wounds. In summary,in vivoandin vitroexperiments consistently highlight the therapeutic potential of GPL/CTLP-MPs hydrogel in facilitating the healing process of PUs.

Effect of Spray-Type Alginate Hydrogel Dressing on Burn Wounds

Immediate burn wound care is a critical factor influencing the outcomes of burn treatment. In this study, we developed a spray-type alginate hydrogel dressing that promotes wound healing, reduces pain, and increases the convenience of use in a burn treatment emergency. We investigated the efficiency of newly developed spray-type alginate hydrogel dressing on the wound healing process. We investigated the efficacy of the alginate hydrogel dressing for wound healing in 30 Sprague Dawley rats. Four deep, round second-degree burn wounds (diameter, 1.5 cm) were created bilaterally on the dorsum of the rat's trunk; the rats were divided into four groups, in which different dressing materials were applied as follows: group A, gauze (control); group B, Mepilex™ (control); group C, 2.25% alginate hydrogel; and group D, 2.5% alginate hydrogel. The gross findings of each group were compared by tracing the remaining wound and performing visual and histological observations and biochemical analysis for proteins associated with wound healing at each time period. In burn wounds, groups C and D showed significantly higher contraction, epithelialization, and healing rates. Histologically, groups C and D showed an improved arrangement of collagen fibers and a thick epithelial layer 14 days after initial wound formation. Group C showed higher CD31, TGF-β, and fibronectin expression in Western blot analyses after day 14. This study suggests that the spray-type alginate hydrogel dressing is an effective material for initial burn wound care.

Effective wound healing on diabetic mice by adhesive antibacterial GNPs-lysine composited hydrogel

Current trends in wound care research focus on creating dressings for diverse wound types, aiming to effectively control the wound healing process. We proposed a wound dressing composed of oxidized hyaluronic acid and amine gelatin with embedded lysine-modified gelatin nanoparticles (HGel-GNPs-lysine). This dressing improves mechanical properties and reduces degradation rates. The storage modulus for HGel-GNPs-lysine was 3,800 Pa, exceeding that of HGel (1,750 Pa). The positively charged surface of GNPs-lysine effectively eliminated Escherichia coli and Staphylococcus aureus. In a diabetic mice model (C57BL/6), HGel-GNPs-lysine immobilized with basic-fibroblast growth factor promoted granulation tissue thickness and collagen density. Gene expression analysis indicated that HGel-GNPs-lysine reduced inflammation and enhanced angiogenesis. This study highlights that HGel-GNPs-lysine could offer alternative treatment strategies for regulating the inflammatory response at the injury site in wound dressing applications.

Recent Advances in Nanocarrier-based Approaches to Atopic Dermatitis and Emerging Trends in Drug Development and Design

Atopic dermatitis (AD), commonly known as Eczema, is a non-communicable skin condition that tends to become chronic. The deteriorating immunological abnormalities are marked by mild to severe erythema, severe itching, and recurrent eczematous lesions. Different pharmacological approaches are used to treat AD. The problem with commercial topical preparations lies in the limitation of skin atrophy, systemic side effects, and burning sensation that decreases patient compliance. The carrier-based system promises to eliminate these shortcomings; thus, a novel approach to treating AD is required. Liposomes, microemulsions, solid lipid nanoparticles (SLNs), nanoemulsions, etc., have been developed recently to address this ailment. Despite extensive research in the development method and various techniques, it has been challenging to demonstrate the commercial feasibility of these carrier- based systems, which illustrates a gap among the different research areas. Further, different soft wares and other tools have proliferated among biochemists as part of a cooperative approach to drug discovery. It is crucial in designing, developing, and analyzing processes in the pharmaceutical industry and is widely used to reduce costs, accelerate the development of biologically innovative active ingredients, and shorten the development time. This review sheds light on the compilation of extensive efforts to combat this disease, the product development processes, commercial products along with patents in this regard, numerous options for each step of computer-aided drug design, including in silico pharmacokinetics, pharmacodynamics, and toxicity screening or predictions that are important in finding the drug-like compounds.

Chitosan nanocomposite for tissue engineering and regenerative medicine: A review

Regenerative medicine and tissue engineering have emerged as a multidisciplinary promising field in the quest to address the limitations of traditional medical approaches. One of the key aspects of these fields is the development of such types of biomaterials that can mimic the extracellular matrix and provide a conducive environment for tissue regeneration. In this regard, chitosan has played a vital role which is a naturally derived linear bi-poly-aminosaccharide, and has gained significant attention due to its biocompatibility and unique properties. Chitosan possesses many unique physicochemical properties, making it a significant polysaccharide for different applications such as agriculture, nutraceutical, biomedical, food, nutraceutical, packaging, etc. as well as significant material for developing next-generation hydrogel and bio-scaffolds for regenerative medicinal applications. Moreover, chitosan can be easily modified to incorporate desirable properties, such as improved mechanical strength, enhanced biodegradability, and controlled release of bioactive molecules. Blending chitosan with other polymers or incorporating nanoparticles into its matrix further expands its potential in tissue engineering applications. This review summarizes the most recent studies of the last 10 years based on chitosan, blends, and nanocomposites and their application in bone tissue engineering, hard tissue engineering, dental implants, dental tissue engineering, dental fillers, and cartilage tissue engineering.

Stem-cell based soft tissue substitutes: Engineering of crosslinked polylysine-hyaluronic acid microspheres ladened with gingival mesenchymal stem cells for collagen tissue regeneration and angiogenesis

BACKGROUND

The aim of this study was to construct crosslinked polylysine-hyaluronic acid microspheres (pl-HAM) ladened with gingival mesenchymal stem cells (GMSCs) and explore its biologic behavior in soft tissue regeneration.

METHODS

The effects of the crosslinked pl-HAM on the biocompatibility and the recruitment of L-929 cells and GMSCs were detected in vitro. Moreover, the regeneration of subcutaneous collagen tissue, angiogenesis and the endogenous stem cells recruitment were investigated in vivo. We also detected the cell developing capability of pl-HAMs.

RESULTS

The crosslinked pl-HAMs appeared to be completely spherical-shaped particles and had good biocompatibility. L-929 cells and GMSCs grew around the pl-HAMs and increased gradually. Cell migration experiments showed that pl-HAMs combined with GMSCs could promote the migration of vascular endothelial cells significantly. Meanwhile, the green fluorescent protein-GMSCs in the pl-HAM group still remain in the soft tissue regeneration area 2 weeks after surgery. The results of in vivo studies showed that denser collagen deposition and more angiogenesis-related indicator CD31 expression in the pl-HAMs+ GMSCs + GeL group compared with the pl-HAMs + GeL group. Immunofluorescence showed that CD44, CD90, CD73 co-staining positive cells surrounded the microspheres in both pl-HAMs + GeL group and pl-HAM + GMSCs + GeL group.

CONCLUSIONS

The crosslinked pl-HAM ladened with GMSCs system could provide a suitable microenvironment for collagen tissue regeneration, angiogenesis and endogenous stem cells recruitment, which may be an alternative to autogenous soft tissue grafts for minimally invasive treatments for periodontal soft tissue defects in the future.

A Poly-D-lysine-Coated Coralline Matrix Promotes Hippocampal Neural Precursor Cells' Differentiation into GFAP-Positive Astrocytes

A major goal of regenerative medicine of the central nervous system is to accelerate the regeneration of nerve tissue, where astrocytes, despite their positive and negative roles, play a critical role. Thus, scaffolds capable of producing astrocytes from neural precursor cells (NPCs) are most desirable. Our study shows that NPCs are converted into reactive astrocytes upon cultivation on coralline-derived calcium carbonate coated with poly-D-lysine (PDL-CS). As shown via nuclei staining, the adhesion of neurospheres containing hundreds of hippocampal neural cells to PDL-CS resulted in disaggregation of the cell cluster as well as the radial migration of dozens of cells away from the neurosphere core. Migrating cells per neurosphere averaged 100 on PDL-CS, significantly higher than on uncoated CS (28), PDL-coated glass (65), or uncoated glass (20). After 3 days of culture on PDL-CS, cell migration plateaued and remained stable for four more days. In addition, NPCs expressing nestin underwent continuous morphological changes from round to spiky, extending and elongating their processes, resembling activated astrocytes. The extension of the process increased continuously during the maturation of the culture and doubled after 7 days compared to day 1, whereas bifurcation increased by twofold during the first 3 days before plateauing. In addition, nestin positive cells' shape, measured through the opposite circularity level correlation, decreased approximately twofold after three days, indicating spiky transformation. Moreover, nestin-positive cells co-expressing GFAP increased by 2.2 from day 1 to 7, reaching 40% of the NPC population on day 7. In this way, PDL-CS promotes NPC differentiation into reactive astrocytes, which could accelerate the repair of neural tissue.

4D Bioprinting via Molecular Network Contraction for Membranous Tissue Fabrication

Generation of thin membranous tissues (TMT), such as the cornea, epidermis, and periosteum, presents a difficult fabrication challenge in tissue engineering (TE). TMTs consist of several cell layers that are less than 100 µm in thickness per layer. While traditional methods provide the necessary resolution for TMT fabrication, they require significant handling and incorporation of several layers is limited. Extrusion bioprinting offers precise control over deposition of different biomaterials and cell populations within the same construct but lacks the resolution to generate biomimetic TMTs. For the first time, a 4D bioprinting strategy that allows for the generation of cell-laden TMTs is developed. Anionic gelatin methacrylate (GelMA) hydrogels are treated with cationic poly-l-lysine (PLL), which induces charge attraction, microscale network collapse, and macroscale hydrogel shrinking. The impact of shrinking on hydrogel properties, print resolution, and cell viability is presented. Additionally, this work suggests that a novel mechanism is occurring, where PLL exhibits a contractile force on GelMA and PLL molecular weight drives GelMA shrinking capabilities. Finally, it is shown that this phenomenon can occur while maintaining an encapsulated cell population. These findings address a critical barrier by generating macroscale tissue structures with their microscale TMT counterparts in the same print.

Glycopolypeptide hydrogels with adjustable enzyme-triggered degradation: A novel proteoglycans analogue to repair articular-cartilage defects

Proteoglycans (PGs), also known as a viscous lubricant, is the main component of the cartilage extracellular matrix (ECM). The loss of PGs is accompanied by the chronic degeneration of cartilage tissue, which is an irreversible degeneration process that eventually develops into osteoarthritis (OA). Unfortunately, there is still no substitute for PGs in clinical treatments. Herein, we propose a new PGs analogue. The Glycopolypeptide hydrogels in the experimental groups with different concentrations were prepared by Schiff base reaction (Gel-1, Gel-2, Gel-3, Gel-4, Gel-5 and Gel-6). They have good biocompatibility and adjustable enzyme-triggered degradability. The hydrogels have a loose and porous structure suitable for the proliferation, adhesion, and migration of chondrocytes, good anti-swelling, and reduce the reactive oxygen species (ROS) in chondrocytes. In vitro experiments confirmed that the glycopolypeptide hydrogels significantly promoted ECM deposition and up-regulated the expression of cartilage-specific genes, such as type-II collagen, aggrecan, and glycosaminoglycans (sGAG). In vivo, the New Zealand rabbit knee articular cartilage defect model was established and the hydrogels were implanted to repair it, the results showed good cartilage regeneration potential. It is worth noting that the Gel-3 group, with a pore size of 122 ​± ​12 ​μm, was particularly prominent in the above experiments, and provides a theoretical reference for the design of cartilage-tissue regeneration materials in the future.

In situ photo-crosslinking silk fibroin based hydrogel accelerates diabetic wound healing through antibacterial and antioxidant

Bacterial infection and excessive reactive oxygen species (ROS) in diabetic wounds lead to a prolonged inflammatory phase, and injuries are highly susceptible to developing into chronic wounds. Improving the poor microenvironment is vital to achieving effective diabetic wound healing. In this work, methacrylated silk fibroin (SFMA) was combined with ε-polylysine (EPL) and manganese dioxide nanoparticles (BMNPs) to form an SF@(EPL-BM) hydrogel with in situ forming, antibacterial and antioxidant properties. EPL imparted high antibacterial activity (>96 %) to the hydrogel. BMNPs and EPL showed good scavenging activity against a variety of free radicals. SF@(EPL-BM) hydrogel had low cytotoxicity and could alleviate H₂O₂-induced oxidative stress in L929 cells. In diabetic wounds infected with Staphylococcus aureus (S. aureus), the SF@(EPL-BM) hydrogel exhibited better antibacterial properties and reduced wound ROS levels more significantly than that of the control in vivo. In this process, the pro-inflammatory factor TNF-α was down-regulated, and the vascularization marker CD31 was up-regulated. H&E and Masson staining showed a rapid transition from the inflammatory to the proliferative phase of the wounds, with significant new tissue and collagen deposition. These results confirm that this multifunctional hydrogel dressing holds well potential for chronic wound healing.

Ion-Pair-Enhanced Double-Click Driven Cell Adhesion and Altered Expression of Related Genes

Bio-orthogonal ligations that crosslink living cells with a substrate or other cells require high stability and rapid kinetics to maintain the nature of target cells. In this study, we report water-soluble cyclooctadiyne (WS-CODY) derivatives that undergo an ion-pair enhanced double-click reaction. The cationic side chain of WS-CODY accelerated the kinetics on the azide-modified cell surface due to proximity effect. Cationic WS-CODY was able to crosslink azide-modified, poorly adherent human lung cancer PC-9 cells not only to azide-grafted glass substrates but also to other cells within 5-30 min. We discovered that cell-substrate crosslinking induced the ITGA5 gene expression, whereas cell-cell crosslinking induced the CTNNA1 gene, according to the adhesion partner. Ion-pair-enhanced WS-CODY can be applied to a wide range of cells with established azide modifications and is expected to provide a powerful tool to regulate cell-substrate and cell-cell interactions.

Biomedical materials for wound dressing: recent advances and applications

Wound healing is vital to maintain the physiological functions of the skin. The most common treatment is the use of a dressing to cover the wound and reduce infection risk and the rate of secondary injuries. Modern wound dressings have been the top priority choice for healing various types of wounds owing to their outstanding biocompatibility and biodegradability. In addition, they also maintain temperature and a moist environment, aid in pain relief, and improve hypoxic environments to stimulate wound healing. Due to the different types of wounds, as well as the variety of advanced wound dressing products, this review will provide information on the clinical characteristics of the wound, the properties of common modern dressings, and the in vitro, in vivo as well as the clinical trials on their effectiveness. The most popular types commonly used in producing modern dressings are hydrogels, hydrocolloids, alginates, foams, and films. In addition, the review also presents the polymer materials for dressing applications as well as the trend of developing these current modern dressings to maximize their function and create ideal dressings. The last is the discussion about dressing selection in wound treatment and an estimate of the current development tendency of new materials for wound healing dressings.

ε-Poly-l-lysine-modified natural silk fiber membrane wound dressings with improved antimicrobial properties

Many complex diseases, such as bacterial infections, frequently accompany cutaneous wound healing, adding to the difficulty of clinical wound management. Consequently, in addition to displaying strong biocompatibility and actively promoting wound healing, an optimal wound dressing should also possess antimicrobial qualities to address issues with bacterial infection. This paper developed natural silk fiber (SF) membranes (also known as a flat silk cocoon (FSC)) with antimicrobial properties as a dressing for skin wounds. By changing the spinning tools and environment of silkworm larvae, a novel natural SF membrane with a cocoon structure and controllable size was prepared. The functional SF membranes were obtained via a hot press process and grafted with ε-Poly-l-lysine (EPL). The results showed that the SF membrane dressing was adjustable in size with a similar structure to the extracellular matrix (ECM), displaying inherent mechanical properties, excellent antimicrobial qualities, and biocompatibility. In vivo experiments using a full-thickness skin defect model indicated that EPL-modified SF membranes significantly promoted the rate of wound healing, exhibiting thicker granulation tissue and higher collagen disposition than commercial dressings (Tegaderm™ film). Therefore, the excellent mechanical qualities and cytocompatibility of the antimicrobial EPL-modified SF membranes substantially promote their potential application as a chronic wound dressing.

Polyurethane based hybrid ciprofloxacin-releasing wound dressings designed for skin engineering purpose

PURPOSE

Even in the 21st century, chronic wounds still pose a major challenge due to potentially inappropriate treatment options, so the latest wound dressings are hybrid systems that enable clinical management, such as a hybrid of hydrogels, antibiotics and polymers. These wound dressings are mainly used for chronic and complex wounds, which can easily be infected by bacteria.

MATERIALS AND METHODS

Six Composite Porous Matrices (CPMs) based on polyurethane (PUR) in alliance with polylactide (PLAs) and poly(vinyl alcohol) (PVA) were prepared and analyzed using optical microscopy. Three different types of hydrogels and their Ciprofloxacin (Cipro) modified variants' ratios were prepared and analyzed using FTIR, SEM and EDX techniques. Six Hybrid Cipro-Releasing Hydrogel Wound Dressings (H-CRWDs) were also prepared and underwent short-term degradation, Cipro release, microbiology and cell viability measurements.

RESULTS

Average porosity of CPMs was in the range of 69-81%. The pore size of the obtained CPMs was optimal for skin regeneration. Short-term degradation studies revealed degradability in physiological conditions regardless of sample type. A meaningful release was also observed even in short time (21.76 ​± ​0.64 ​μg/mL after 15 ​min). Microbiological tests showed visible inhibition zones. Cell viability tests proved that the obtained H-CRWDs were biocompatible (over 85% of cells).

CONCLUSIONS

A promising hybrid wound dressing was labeled. Simple and cost-effective methods were used to obtain microbiologically active and biocompatible dressings. The results were of importance for the design and development of acceptable solutions in the management of chronic wounds of high potential for infection.

An antibacterial ε-poly-L-lysine-derived bioink for 3D bioprinting applications

Limited bioinks have hindered applying 3D bioprinting to tissue engineering, and bacterial infection is a serious threat to these applications. Aiming to solve this problem, a novel ε-poly-L-lysine (EPL) derived...