Controlled-release of free bacteriophage nanoparticles from 3D-plotted hydrogel fibrous structure as potential antibacterial wound dressing

To combat the emergence of drug-resistant bacteria, a locally isolated bacteriophage (HZJ) targeting H5α Escherichia coli was used as an antibacterial agent to make wound dressing samples in this study. The phages were physically embedded within an alginate hydrogel sample so that they could later be released with their tails being free during the infection process, which preserves their lytic activity. The HZJ phage isolated in the study have a 20 min latent period and are stable between pH 6 and pH 9 and at temperatures below 45 °C. The addition of phage to an E. coli culture suppressed over 99% of bacterial growth in 2-h (p < 0.001). Phage-embedded hydrogel fibers were used to create porous wound dressing material using three-dimensional (3D) printing. The majority of phage lytic activity (85%–90%) was preserved after encapsulation. After they were embedded in samples, HZJ lysed 57% to 67% of bacteria (p < 0.001) within 2 h and the antibacterial effects lasted at least 24 h. The small amount of phage released in 2 h was able to quickly replicate and effectively lysed the majority of the bacterial hosts. Phage-embedded alginate samples released 10% of its incorporated phage particles in 24 h. The SEM micrographs show that, compared to phage-free samples, fewer E.coli cells were observed on phage-embedded samples 2 h after bacteria were exposed to the samples. The phage-embedded sample was not cytotoxic to L929 cells. The presence of HZJ in alginate hydrogel promoted cell growth (p < 0.01) and adhesion to the samples. Further, the existence of phage did not alter the tensile strength and modulus of samples (p > 0.05). An antibacterial dressing capable of slowly releasing lytic phages and effectively suppressing bacterial growth for up to 24 h was produced in this study. This model represents an attractive means to reduce use of antibiotics and other additives in conventional dressings.