Nitric Oxide-Releasing Polydimethylsiloxane Sponges with Tunable Porosity

The popularity of sponge materials has been steadily increasing, promoting extensive research into enhancing their properties for specific applications, such as effectively separating oil from water and promoting wound healing. In this study, polydimethylsiloxane (PDMS) sponges with tunable porosity were fabricated to investigate the influence of porosity on nitric oxide (NO) donor loading, NO release kinetics, and antibacterial efficacy. The fabrication process involved a straightforward method using sodium chloride (NaCl) crystals as templates to modulate the porosity of the sponge. The PDMS sponges with varying porosities were incorporated with the NO donor S-nitroso-N-acetylpenicillamine (SNAP), using tetrahydrofuran (THF) as the embedding solvent. The results demonstrated a direct correlation between porosity and SNAP loading, diffusibility, and NO release behavior. The pore characteristics of sponges were further characterized using scanning electron microscopy. The maximum SNAP loading capacity achieved was 23 wt %, enabling substantial NO release in 4 h under physiological conditions. Moreover, the SNAP-incorporated sponges demonstrated remarkable antibacterial efficacy, with enhanced porosity correlating with higher bactericidal activity. This included a 2.45- and 2.38-log reduction in viable adhered and planktonic Escherichia coli and a 2.65- and 5.04-log reduction in viable adhered and planktonic Staphylococcus aureus compared to unmodified control PDMS sponges. These findings highlight the distinct properties exhibited by PDMS sponges with different porosities, thereby emphasizing their potential for tailoring sponge materials for specific applications such as wound healing, tissue engineering, and drug delivery.