PURPOSE: The purpose of the study was to coat surgical sutures with a new quaternary ammonium silane (QAS) antimicrobial compound at two different application temperatures and then to evaluate the resulting structural, physical, mechanical, and biological properties.
STUDY DESIGN, SETTING, SAMPLE: In vitro and in vivo studies were conducted using male albino Wistar rats approved by the Joint Ethical Committee of IMU and Postgraduate Medical Institute, Lahore. Only suture samples, coated uniformly with verified presence of the compound and of adequate length were used. Samples which were not coated uniformly and with inadequate length or damaged were excluded.
PREDICTOR VARIABLE: Predictor variables were sutures with and without QAS coatings and different temperatures. Sutures were coated with QAS at 0.5 and 1.0% wt/vol using the dip coating technique and sutures with and without QAS coating were tested at 25 and 40 °C temperatures.
MAIN OUTCOME VARIABLE(S): Outcome variables of structural and physico-mechanical properties of QAS-coated and non-coated sutures were measured using Fourier transform infrared spectroscopy (for structural changes), confocal laser and scanning electron (for diameter changes), and tensile strength/modulus (for mechanical testing). Biologic outcome variables were tested (bacterial viability); macrophage cultures from Wistar rats were tested (M1/M2 polarization detecting IL-6 and IL-10). Macrophage cells were analyzed with CD80+ (M1) and CD163+ (M2). Chemotaxis index was calculated as a ratio of quantitative fluorescence of cells.
COVARIATES: Not applicable.
ANALYSES: Ordinal data among groups were compared using the Wilcoxon Mann-Whitney U test along with the comparison of histological analysis using the Wilcoxon Sign-rank test (P
Materials and methods: QOS collagen nanofibers were electrospun by incorporating various concentrations of QOS (0.1%-10% w/w) and were cross-linked in situ after exposure to ammonium carbonate. The QOS cross-linked scaffolds were characterized and their biological properties were evaluated in terms of their biocompatibility, cellular adhesion and metabolic activity for primary human dermal fibroblasts and human fetal osteoblasts.
Results and discussion: The study revealed that 1) QOS cross-linking increased the flexibility of otherwise rigid collagen nanofibers and improved the thermal stability; 2) QOS cross-linked mats displayed potent antibacterial activity and 3) the biocompatibility of the composite mats depended on the amount of QOS present in dope solution - at low QOS concentrations (0.1% w/w), the mats promoted mammalian cell proliferation and growth, whereas at higher QOS concentrations, cytotoxic effect was observed.
Conclusion: This study demonstrates that QOS cross-linked mats possess anti-infective properties and confer niches for cellular growth and proliferation, thus offering a useful approach, which is important for hard and soft tissue engineering and regenerative medicine.