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. 2024 May 24;10(6):363.
doi: 10.3390/gels10060363.

Antibacterial Silver Nanoparticle Containing Polydopamine Hydrogels That Enhance Re-Epithelization

Naphtali A O'Connor  1   2   3 , Abdulhaq Syed  1 , Ertan Kastrat  3 , Hai-Ping Cheng  3
Affiliations

Antibacterial Silver Nanoparticle Containing Polydopamine Hydrogels That Enhance Re-Epithelization

Naphtali A O'Connor et al. Gels. .

Abstract

A polydopamine polyelectrolyte hydrogel was developed by ionic crosslinking dextran sulfate with a copolymer of polyethyleneimine and polydopamine. Gelation was promoted by the slow hydrolysis of glucono-δ-lactone. Within this hydrogel, silver nanoparticles were generated in situ, ranging from 25 nm to 200 nm in size. The antibacterial activity of the hydrogel was proportional to the quantity of silver nanoparticles produced, increasing as the nanoparticle count rose. The hydrogels demonstrated broad-spectrum antibacterial efficacy at concentrations up to 108 cells/mL for P. aeruginosa, K. pneumoniae, E. coli and S. aureus, the four most prevalent bacterial pathogens in chronic septic wounds. In ex vivo studies on human skin, biocompatibility was enhanced by the presence of polydopamine. Dextran sulfate is a known irritant, but formulations with polydopamine showed improved cell viability and reduced levels of the inflammatory biomarkers IL-8 and IL-1α. Silver nanoparticles can inhibit cell migration, but an ex vivo human skin study showed significant re-epithelialization in wounds treated with hydrogels containing silver nanoparticles.

Keywords: antibacterial; ionic crosslinking; polydopamine; silver nanoparticle; wound healing.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Ionic crosslinking of dextran sulfate with polyethyleneimine.
Figure 2
Figure 2
Representative images for hydrogels and SEM images at 250× and 2500× magnification: (A–C) DexSulf-PEI, (D–F) DexSulf-PEI-PDA, (G–I) 2% AgNP-PDA, (J–L) 8% AgNP-PDA and (M–O) 64% AgNP-PDA.
Figure 3
Figure 3
SEM images with BEI detector: (A,B) 8% AgNP-PDA at 30,000× (magnified region highlighted) and 100,000×, (C,D) 64% AgNP-PDA at 10,000× and 100,000×.
Figure 4
Figure 4
Characterization of DexSulf-PEI, DexSulf-PEI-PDA, 2%, 8% and 64% AgNP-PDA hydrogels: (A) FTIR spectra. (B) Swelling ratios in deionized water (n = 3, Mean ± SD). (C) Averaged compressive stress vs. compressive strain curves (n = 3).
Figure 5
Figure 5
Antimicrobial studies with S. aureus. (A) DexSulf-PEI, DexSulf-PEI-PDA, 2%, 8% and 64% AgNP-PDA gels inoculated with 5 µL aliquots 108 cells/mL of S. aureus and incubated for 24 h. Arrow indicates bacterial growth. (B) Bacterial live/dead assay of DexSulf-PEI-PDA, 2% AgNP-PDA and 8% AgNP-PDA hydrogels. Positive control was agar-treated with antibiotic gentamicin and negative control was untreated agar. (C) S. aureus infected human skin explant studies with PBS, 2% AgNP-PDA and 8% AgNP-PDA hydrogels. Unwounded human skin explants were inoculated for 24 h followed by 24-h treatment (n = 3, Mean ± SD).
Figure 6
Figure 6
Biocompatibility studies on human skin explants with PBS (control), DexSulf-PEI, DexSulf-PEI-PDA, 2% AgNP-PDA and 8% AgNP-PDA hydrogels. (A) Cell viability over 72 h relative to PBS control. (B,C) ELISA after 24 h for interleukins IL-8 (left) and IL1-α (right). (n = 3, Mean ± SD). * indicates a significant difference from PBS treatment (p-value < 0.05).
Figure 7
Figure 7
Hematoxylin & Eosin (H&E) and Keratin-17 (K17) stained human skin explants after 7 days of treatment with hydrogels. (A,B) Day 0 of untreated wounded skin. (C,D) PBS. (E,F) 2% AgNP-PDA. (G,H) 8% AgNP-PDA. Dashes indicate wound edge.
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