Study on the antibacterial activity and biocompatibility of nano-silver/carbon nanotube composite coatings on airway stents prepared by micro-transfer printing

Common complications following endotracheal intubation or tracheostomy include tracheal stenosis and infection, which often exacerbate one another, complicating treatment. In this context, airway stents with stable antimicrobial properties and excellent biocompatibility emerge as an ideal therapeutic option. Silver nanoparticles (AgNPs) are renowned for their remarkable antibacterial and anti-inflammatory activities, making their incorporation into airway stent coatings a promising strategy for addressing stent-associated infections and granulation tissue proliferation. In preliminary research, a silicone airway stent coated with a Silver nanoparticles/Carbon nanotubes (AgNPs/CNTs) layer was successfully fabricated, and the present study was conducted to further evaluate its antimicrobial properties and tissue compatibility through systematic in vitro and in vivo experiments. In vitro experiments assessed its antimicrobial properties using the paper disc agar diffusion method and bacterial co-cultivation assay, with the bacteriostatic effect quantified through bacterial counting. For in vivo experiments, a New Zealand rabbit model was employed, wherein AgNPs/CNTs-coated airway stents were implanted alongside standard silicone stents. Tracheal lavage was performed at two and four weeks post-surgery, followed by colony counting. Additionally, histological evaluations were conducted to assess inflammation, granulation tissue proliferation, and collagen deposition, while confocal microscopy was used to observe and measure biofilm formation on the surface of the airway stents. The in vitro antimicrobial zone tests demonstrated that the AgNPs/CNTs coating effectively inhibited the growth of Staphylococcus aureus and Pseudomonas aeruginosa, with inhibition zones measuring 17.13 ± 1.21 mm and 13.55 ± 0.81 mm, respectively. In the bacterial co-cultivation assay, the AgNPs/CNTs group exhibited significantly fewer colony counts compared to the standard silicone group (P < 0.05). In vivo antimicrobial experiments revealed that the colony count in the AgNPs/CNTs-coated group was significantly lower than that of the standard silicone group at both the 2-week and 4-week time points (P < 0.05). Histological analysis under microscopy indicated that the AgNPs/CNTs group had significantly reduced granulation tissue thickness, inflammatory cell infiltration, and collagen deposition compared to the standard silicone group (P < 0.05). Furthermore, confocal microscopy measurements of biofilm formation revealed that the biofilm thickness on the surface of the AgNPs/CNTs-coated stents was 25.75 ± 5.93 μm, significantly lower than the 45.27 ± 12.84 μm observed on the standard silicone stents (P < 0.05). The AgNPs/CNTs-coated airway stent exhibited exceptional antimicrobial properties both in vitro and in vivo, effectively inhibiting bacterial growth, reducing bacterial colonization and biofilm formation within the airway, and significantly alleviating granulation tissue proliferation and collagen deposition. This, in turn, improved the airway microenvironment. This study provides a theoretical foundation for the clinical application of AgNPs/CNTs-coated airway stents.