Development of sustained-release antibacterial urinary biomaterials through using an antimicrobial as an organic modifier in polyurethane nanocomposites.

Urinary catheters are among the most frequently used medical devices in clinical practice. However, their use is associated with high rates of nosocomial infection. This study investigates the use of polyurethane nanocomposites (PUNCs) incorporating an antimicrobial agent, chlorhexidine diacetate (CHX), behaving as nanoparticle dispersant and model drug/active agent, as sustained-release antibacterial biomaterials in urinary devices. A range of PUNCs incorporating organically modified silicate (OMS) nanoparticles with CHX was fabricated using a solution-cast method. PUNCs with free CHX added into the bulk polymer were also made. Materials were assessed for antibacterial activity in an in vitro urinary tract (UT) model and release kinetics of CHX was studied. PUNCs demonstrated sustained antibacterial activity against Staphylococcus epidermidis in the UT model, reaching ~50 days infection-free in materials with 2 wt % free CHX loading. Drug-release profiles demonstrated that, compared with microcomposite and unfilled polyurethane, the initial burst effect was significantly reduced in PUNCs. Prolonged drug release was achieved through incorporation of OMS, hypothesized to be due to a combination of barrier properties created by the nanoinclusions and strong interactions between CHX and MMT within the PUNCs. Use of PUNCs for sustained drug release in long-term urinary applications shows promise in addressing catheter-related nosocomial infections.