Incorporation of Silver Sulfadiazine into An Electrospun Composite of Polycaprolactone as An Antibacterial Scaffold for Wound Healing in Rats

Abstract

Objective: Fabrication of an antibiotic-loaded scaffold with controlled release properties for wound dressing is one of tissue engineering challenges. The aim of this study was to evaluate the wound-healing effectiveness of 500-μm thick polycaprolactone (PCL) nanofibrous mat containing silver sulfadiazine (SSD) as an antibacterial agent.

Materials and methods: In this experimental study, an electrospun membrane of PCL nanofibrous mat containing 0.3% weight SSD with 500 μm thickness, was prepared. Morphological and thermomechanical characteristics of nanofibers were evaluated. Drug content and drug release properties as well as the surface hydrophobicity of the nanofibrous membrane were determined. Antimicrobial properties and cellular viability of the scaffold were also examined. A full thickness wound of 400 mm² was created in rats, to evaluate the wound-healing effects of PCL/SSD blend in comparison with PCL and vaseline gas used as the control group.

Results: SSD at a concentration of 0.3% improved physicochemical properties of PCL. This concentration of SSD did not inhibit the attachment of human dermal fibroblasts (HDFs) to nanofibers in vitro, but showed antibacterial activity against Gram-positive Staphylococcus aureus (ST) and Gram-negative Pseudomonas aeruginosa (PS). Overall, results showed that SSD improves characteristics of PCL nanofibrous film and improves wound-healing process in one-week earlier compared to control.

Conclusion: Cytotoxicity of SSD in fabricated nanofibrous mat is a critical challenge in designing an effective wound dressing that neutralizes cellular toxicity and improves antimicrobial activity. The PCL/SSD nanofibrous membrane with 500- μm thickness and 0.3% (w/v) SSD showed applicable characteristics as a wound dressing and it accelerated wound healing process in vivo.

Keywords: Nanofibers; Polycaprolactone; Silver Sulfadiazine; Tissue Engineering; Wound Healing.

Fig.1

Solution and fiber characterization. A. Rheology test for PCL and PCL/SSD mats, B. Field emission electron microscopy (FE-SEM) for PCL/ SSD mat (scale bar: 2 µm), C. PCL mat (scale bar: 2 µm), D. Scanning electron microscopy imaging, and E. Energy dispersive spectra of PCL containing 0.3% SSD. PCL; Polycaprolactone, SSD; Silver sulfadiazine, CP; Centipoise, SR; Shear rate, and L 1, 2, 3; Size 1, 2, 3.

Fig.2

Physicochemical characterization. A. DSC thermogram for (a) PCL/ SSD nanofibrous mat, for (b) PCL nanofibrous mat, and (c) physical mixingof PCL and SSD, B. TGA results for PCL and PCL/SSD nanofibrous mat, and C. Mechanical behavior of the mats with and without SSD. DSC; Differentialscanning calorimetry, PCL; Polycaprolactone, SSD; Silver sulfadiazine, and TGA; Thermogravimetric analysis.

Fig.3

FTIR and contact angle for nanofibrous mat. A. FTIR for (a) SSD, (b) PCL, and (c) PCL/SSD nanofibrous mat are shown, B. Contact angle for PCL, and C. PCL/SSD are shown. FTIR; Fourier Transform Infrared spectroscopy analysis, SSD; Silver sulfadiazine, and PCL; Polycaprolac.

Fig.4

Drug release profile. A. In vitro SSD release from PCL/SSD nanofibrous mat, B. Antibacterial test for PCL/SSD, 1 and 3 are PCL mat containing SSD, and 2 and 4 are PCL mat. B. is Staphylococcus aureus and C. is Pseudomonas aeruginosa. MTT assay for PCL and PCL/SSD nanofibrous mat, D. Differences between two nanofibrous mat were not significant, E. Attachment of cells on PCL nanofibrous mat (scale bar: 50 µm), and F. PCL/SSD nanofibrous mat are shown (scale bar: 50 µm). SSD; Silver sulfadiazine, PCL; Polycaprolactone, and MTT; 3-(,-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.

Fig.5

Macroscopic observation. The process of wound closure during the healing time was evaluated for assessment of PCL and PCL/SSD nanofibrous mat. PCL; Polycaprolactone and SSD; Silver sulfadiazine.

Fig.6

Microscopic observation: histological evaluations of wounds treated with PCL, PCL/SSD and control, on days 14, 21, and 28 of the healing process are shown. A. H&E staining and B. Masson’s trichrome staining (scale bar: 50 µm).