Atomic-layer-deposition application for antibacterial coating of biomedical materials: surgical sutures

Suture-associated surgical site infection (SSI) causes bacterial pathogens to colonize on the suture surface that are highly resistant to antibiotic treatment. Conventional suture materials used in surgical practice are causing complications such as infection and chronic inflammation. Surgical suture materials with antibacterial coatings are widely used in surgical practice. However, all the widely used antibacterial agents are not permanent (limited lasting) due to their instability and release depending on environmental conditions (pH or temperature, for example). Therefore, more long-lasting (low-dose) and effective antibacterial function materials are required. In the present work, we proposed a new material and method of antibacterial coating the surgical sutures based on the atomic layer deposition (ALD) technique to enhance its antibacterial activity for treatment of the SSI. We have proposed applying a vanadium-doped TiO2 nanofilm (hybrid nanomaterial, TiVOx) with 27.5 nm thickness to enhance the antibacterial property of surgical sutures using the ALD technique. We have illustrated that a base coating of Al2O3 (seed layer) applied to the suture surface, which directly contacts the polypropylene (PP) suture, improves the adhesion of the deposited antibacterial material TiVOx. This provides a long-lasting antibacterial effect on the suture (a prolonged antibacterial effect of the coating material), i.e. increases the stability of the deposition (stable in water, air, in the human body, in different pH mediums, and at temperatures up to 70 degrees C). The sutures did not deteriorate after several wash cycles with sterilizing solvents. Also, the antibacterial agent (TiVOx) is nontoxic. The concentration of vanadium in the film is below the toxicity limits due to the low diffusivity of vanadium and high adhesion with the base coating material (Al2O3). Sutures coated with V-doped TiO2 were characterized using scanning electron microscopy images, and elemental analysis was performed using energy dispersive spectroscopy Spectroscopy. The antibacterial activity of TiVOx coated sutures against two types of microorganisms, E. coli and Proteus vulgaris (Pr. Vulgaris) was compared to that of noncoated sutures. The quantitative assessment of antibacterial activity of suture materials with and without ALD nanocoating TiVOx against E. coli and Pr. Vulgaris has been performed. No growth of bacteria around the suture material with antibacterial TiVOx ALD nanocoating throughout the entire observation period of 48 and 72 h was observed. However, after 48 h, the concentration of bacteria of the E. Coli around the suture material without ALD TiVOx nanocoating on nutrient agar was 5.5 +/- 0.3 Log CFU cm-3, and after 72 h it was 8.0 +/- 0.5 Log CFU cm-3. For Pr. Vilgaris, after 48 h, the concentration of bacteria around the suture material without ALD TiVOx nanocoating on nutrient agar was 2.1 +/- 0.1 Log CFU cm-3, while after 72 h it was 4.5 +/- 0.2 Log CFU cm-3. ALD-coated TiVOx on the PP sutures inhibited approximately 100% of biofilm formation. Also, the inhibition zones in the disc diffusion assay revealed that all the ALD TiVOx coating inhibited (100%) the growth of E. coli and Pr. Vulgaris, notably compared to the uncoated suture samples.