Synthesis and Characterization of Copper Sulfide Nanorods as Photothermal Agent Embedded in PDMS for Antibacterial Catheter Application

Introduction: Bacterial biofilms attached to catheter surfaces can trigger urinary tract infections. Providing antibiotics with regular prescriptions is not sufficient to stop the replication of bacteria because of bacterial resistance to antibiotics. Enhanced doses of antibiotics trigger bacterial resistance and potentially cause toxicity in normal cells. Nanomaterials have emerged as a new approach to combat bacterial resistance through various mechanisms, such as generating reactive oxygen species (ROS), destroying membranes, and disrupting bacterial functions by binding to intracellular components. Coating nanomaterials on the surface of a catheter is an effective way to kill bacteria and prevent biofilm formation. However, the low selectivity of nanomaterials not only kills bacteria but is also toxic to normal cells. Another method is to directly embed nanoparticles in catheter-based materials, such as silicon, which could decrease toxicity and antibacterial activity. To overcome this challenge, CuS nanorods (NRs) with near-infrared (NIR) absorbance ability are used as antibacterial agents to kill bacteria through ion release, and the photothermal effect can be utilized as an antibacterial agent in PDMS to create a catheter model.
Aim: To develop a biocompatible, hydrophobic, and rapidly sterilizing antibacterial urinary catheter using CuS NRs embedded in polydimethylsiloxane (PDMS@CuS).
Methods: The photothermal agent CuS was prepared using a hydrothermal method. The XRD pattern and Raman, XPS, and UV-Vis spectra were used to obtain the structural and optical characteristics. SEM, TEM, and HR-TEM were used to characterize the morphology of CuS. An MTT assay was used to ensure that CuS was safe for normal cells. A urinary catheter model was created by embedding different amounts of CuS in PDMS, and the surface morphology, water contact angle, photothermal properties, and antibacterial performance were characterized. The biocompatibility of PDMS@CuS was assessed to ensure safe interactions between the material and normal cells.
Results: The hexagonal crystal structure of CuS was confirmed by XRD, XPS, EDX, and Raman spectroscopy. The nanorod shape of CuS was observed using SEM, TEM, and HR-TEM. The surface morphology and water contact angle of PDMS@CuS exhibited smooth surface roughness and hydrophobicity, with a deduced water contact angle value for increasing CuS NRs content. NIR irradiation of PDMS@CuS in 2 mL DI water for 10 min hit the thermal ablation with the highest temperature of 67.4 °C. Antibacterial performance, which was evaluated by observing the growth curve, agar plate assay, and bacterial morphology of gram-negative Escherichia coli (E. coli) and gram-positive Staphylococcus aureus (S. aureus), demonstrated that PDMS@CuS has good photothermal conversion efficiency and excellent antibacterial efficacy against both bacteria (> 99%). Furthermore, the biocompatibility test of PDMS@CuS demonstrated exceptional biocompatibility and anti-cell adhesion characteristics, although the highest content of CuS was 0.8 wt%.
Conclusion: The hydrothermal technique successfully synthesized CuS NRs with low cytotoxicity. The urinary catheter model, PDMS@CuS, had a smooth surface, hydrophobicity, and good photothermal conversion efficiency. NIR laser irradiation of PDMS@0.8% CuS for 10 min resulted in thermal ablation, demonstrating its appropriateness for a photothermal catheter with rapid sterilization. The antibacterial performance and biocompatibility tests showed that PDMS@0.8%CuS had excellent antibacterial activity, good biocompatibility, and anti-cell adhesion, indicating its potential as a photothermal antibacterial catheter for combating CAUTI.