Bodily mechanisms for wound healing involve the extracellular matrix – a network of proteins and other molecules around cells. The extracellular matrix holds cells in place inside the tissue, helps cells communicate with each other and triggers wound repair mechanisms. Materials that mimic the extracellular matrix are best suited for dressing chronic wounds.
Hydrogels mimic the extracellular matrix, promoting cell adhesion, proliferation, and migration. Hydrogels are biocompatible and do not trigger any immune response. This makes them ideal for delivering drugs, especially bioactive peptides. However, hydrogels have low mechanical strength and flexibility. And they cannot release drugs for long durations.
Recently, researchers from the Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram worked out a solution to this problem. To treat chronic wounds, they developed a 3D bilayered hydrogel and nanofiber sponge incorporating bioactive peptides.
The researchers chose a chitosan-gelatin hydrogel as base for the sponge. Chitosan, a polysaccharide derived from chitin, is biocompatible, bioactive, and biodegradable. Gelatin exhibits excellent biocompatibility and promotes cell attachment and proliferation. The combination of chitosan and gelatin in hydrogels enhances properties such as degradation rate, porosity, cell attachment and proliferation.
Now the problem was to make the hydrogel stronger. The researchers decided to crosslink the hydrogel with a top layer of poly(L-lactic acid)−chitosan−poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nanofibers. Poly-L-lactic acid degrades into lactic acid, a naturally occurring metabolite in the body and is widely used in biomedical applications, particularly for the preparation of nanofibers. It has excellent mechanical strength, biocompatibility and a controllable degradation rate. It also promotes cell attachment, proliferation, and differentiation, facilitating tissue regeneration. Chitosan has intrinsic antimicrobial properties and helps control infections. It also has high porosity and surface area, facilitating cell adhesion, proliferation, and migration, promoting tissue regeneration.
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate), the other component of the top layer, is also a biodegradable copolymer. These polymers can be loaded with bioactive peptides.
The team synthesised two bioactive peptides, LLKKK18, a therapeutic agent for burn wounds, and Tylotoin, which kills microbes. To create LLKKK18 peptide-loaded nanofiber mats, The researchers optimised the electrospinning. They synthesised poly(lactic-co-glycolic acid) nanoparticles to encapsulate Tylotoin, facilitating controlled release and enhancing the therapeutic potential of the dressing.
Thus, they prepared a 3D bilayered hydrogel and nanofiber sponge dressing, with the porous and elastic hydrogel layer at the bottom and an antimicrobial peptide-functionalized nanofiber layer at the top.
To examine the structural characteristics of the 3D bilayered sponge, they calculated its porosity using liquid displacement to understand the sponge’s ability to retain moisture and facilitate cell migration. Using ImageJ software, they quantified the water absorption capacity of the sponge. Water retention tests confirmed the sponge’s effectiveness in absorbing excess wound exudate, vital for optimal healing conditions.
To assess the antibacterial activity of the sponge dressing and the LLKKK18 peptide, they used Staphylococcus aureus, a Gram-positive bacterium,and Pseudomonas aeruginosa, a Gram-negative bacterium. These bacterial strains are commonly found in infected wounds.
The Kirby-Bauer disc diffusion test showed large inhibition zones around the sponge discs demonstrating their effectiveness against bacterial growth.
Lastly, to test the effectiveness of the dressing, they made excisional skin wounds in diabetic mice and took biopsy samples from the wounds every week for three weeks. Histological analysis revealed that the 3D bilayered sponge promoted cell adhesion, migration, and the formation of blood vessels. The wounds showed thicker granulation tissue and faster formation of epithelial cells over the wound, compared to the wounds in control groups.
The presence of hair follicles and gland formation in treated wounds indicated effective skin regeneration and maturation.
The sponge exhibited a slow biodegradation rate, with approximately 40% degradation after 14 days and around 60% after 21 days. This means that the dressing need not be changed every day.
The 3D bilayered sponge demonstrated superior wound closure rates, indicating its potential for clinical applications in wound management.
Clinical trials using the dressing now remain to be done. Will pharma industries take up the challenge?
DOI: 10.1021/acsabm.4c00669
ACS Appl. Bio Mater., 7 (10), 6492–6505 (2024)
Reported by Atig Udham
Freelance writer, Goa
STEAMindiaReports 
Leave a comment