Nisin in medical dressings

I. Antimicrobial Characteristics and Mechanism of Nisin

Nisin (nisin) is a natural antimicrobial peptide produced by Lactococcus lactis, with core antimicrobial advantages including:

Targeted against Gram-positive bacteria: It disrupts bacterial cell membrane integrity and inhibits cell wall synthesis, exerting potent inhibition on pathogenic bacteria such as Staphylococcus aureus, Streptococcus, and Listeria. These bacteria are major pathogens causing medical dressing infections (e.g., S. aureus accounts for over 30% of postoperative wound infections).

Excellent biocompatibility: As a protein, Nisin can be degraded by human proteases, showing no cytotoxicity and low potential to induce bacterial drug resistance. This property surpasses traditional antibiotic antimicrobial agents (e.g., vancomycin), reducing risks of drug-resistant bacteria from long-term use.

II. Application Forms and Antimicrobial Performance Verification of Nisin in Medical Dressings

Dressing Matrix Binding Methods

Direct addition type: Nisin is mixed into dressing materials (e.g., sodium alginate, gelatin, polyurethane) to continuously release antimicrobial components via a sustained-release mechanism. For example, adding Nisin to sodium alginate-chitosan composite dressings yields an inhibition zone diameter of 15–20 mm against S. aureus in vitro, with antibacterial rates maintaining >90% within 72 hours.

Coating modification type: Nisin is immobilized on the dressing surface through electrospinning, cross-linking reactions, etc., forming an antimicrobial barrier. Studies show that polylactic acid (PLA) nanofiber membranes coated with Nisin exhibit >85% adhesion inhibition rate against Staphylococcus epidermidis, and only 30% Nisin is released within 7 days in simulated body fluids, achieving long-acting antisepsis.

Key Influencing Factors of Antimicrobial Performance

pH environment: Nisin shows optimal stability under acidic conditions (pH 4–6), and wound exudate typically has a pH of 5.5–7.0, close to its effective range. When pH exceeds 7.5, Nisin’s antimicrobial activity decreases by ~50%, making the pH buffering capacity of the dressing matrix a key optimization focus.

Synergistic effects with other components: Combining Nisin with silver ions, chitosan, etc., enhances antimicrobial effects through multiple mechanisms of "membrane disruption + metal ion toxicity + physical barrier". For instance, Nisin-nanosilver composite dressings improve bacterial clearance rate in infected wounds by 40% compared to single Nisin dressings in animal experiments.

III. Animal Experiments and Clinical Translation Progress

Animal Model Verification

In a rat skin defect model, collagen dressings containing Nisin reduce wound infection rate by 60%, shorten healing time by 3–5 days compared to the blank group, and histopathological observation shows promotion of granulation tissue formation and epithelialization.

For diabetic foot ulcer models, Nisin-hyaluronic acid dressings inhibit biofilm formation (a major cause of bacterial drug resistance), doubling the ulcer area reduction rate with no obvious inflammatory cell infiltration, confirming safety.

Clinical Application Challenges

Inadequate coverage of Gram-negative bacteria: Nisin has limited inhibition against Gram-negative bacteria like E. coli and Pseudomonas aeruginosa, requiring combination with other antimicrobial components (e.g., polyhexamethylene biguanide) to construct a broad-spectrum antimicrobial system.

Regulation of release kinetics: Rapid release may cause excessive early Nisin concentration and waste, while slow release may fail to control acute infections promptly. Current microencapsulation technology (e.g., PLGA nanoparticles) enables biphasic Nisin release: 30% rapid antibacterial release within the first 24 hours, followed by 70% sustained release over 7 days.

IV. Future Development Directions

Intelligent responsive dressings

Combining with pH-sensitive polymers (e.g., polyacrylic acid) accelerates Nisin release in the acidic environment of infected wounds for "on-demand antisepsis". Studies show that pH-responsive Nisin dressings release 3 times faster at pH 5.5 than at pH 7.4, better matching the microenvironmental needs of infected wounds.

Biofilm-targeted strategies

Modifying Nisin with membrane-targeting peptides (e.g., Aptamer) enhances its penetration into bacteria within biofilms. In vitro experiments show that targeted Nisin increases clearance rate of mature S. aureus biofilms from 40% to 75%.

Industrial cost control

Current Nisin fermentation production cost is ~2000–3000 CNY/kg. Genetic engineering to modify high-yield strains (e.g., recombinant Lactococcus lactis) and optimize purification processes are expected to reduce costs by 30%–50%, promoting its popularization in high-end medical dressings.

Conclusion

With characteristics of natural antisepsis, low toxicity, and low drug resistance potential, Nisin shows promise to replace traditional antibiotics in medical dressings. Despite current challenges like Gram-negative bacteria coverage and cost control, Nisin-based antimicrobial dressings are gradually moving from laboratories to clinics through material modification and biotechnological innovation, providing new solutions for precise care of infected wounds.