(Nanowerk Spotlight) Every surgical procedure, from routine appendectomies to complex organ transplants, relies on a technology that has remained fundamentally unchanged for thousands of years: the surgical suture. These threads that bind wounds closed serve as a critical tool in healing but can also become a dangerous weakness in surgical recovery. When bacteria colonize sutures, they form resilient communities called biofilms that resist traditional antibiotics, leading to severe infections that affect millions of patients annually.
The medical community has waged a long battle against suture-related infections. Early solutions involved soaking sutures in antimicrobial compounds – an approach that proved temporary at best. The introduction of antibiotics in the mid-20th century offered new hope, but bacteria evolved resistance faster than new drugs could be developed. In the 1970s, researchers began incorporating antimicrobial agents directly into suture materials, leading to the development of triclosan-coated sutures that gained widespread use in the 2000s.
However, these coated sutures face fundamental limitations. Their effectiveness depends on gradually releasing antimicrobial compounds into surrounding tissue – an approach that inevitably fails as the protective coating depletes. Moreover, the released compounds can accumulate in body tissues, potentially promoting bacterial resistance and raising toxicity concerns. Silver nanoparticles emerged as a promising alternative but proved unstable in biological environments, breaking down before wounds could fully heal.
Recent advances in materials science have opened new possibilities for preventing bacterial colonization through surface engineering rather than chemical warfare. Atomic layer deposition (ALD), a technique developed for semiconductor manufacturing, allows materials to be built up one atomic layer at a time with unprecedented precision. This capability has enabled scientists to create surfaces that physically prevent bacteria from attaching or destroy them on contact, rather than relying on chemical release.
Scientists at Dagestan State University have now applied this atomic-scale engineering approach to create what may be the first permanent solution to suture-related infections. By precisely layering metal oxides onto conventional surgical sutures, they have developed a coating that actively destroys bacteria while remaining stable and biocompatible. Their results, published in Biomedical Materials (“Atomic-layer-deposition application for antibacterial coating of biomedical materials: surgical sutures”), demonstrate complete prevention of bacterial growth through a mechanism that, unlike current approaches, cannot be depleted or overcome through bacterial resistance.
Mechanism of antibacterial effect of ALD TiVOx antibacterial coating. (Image: Department of Physical Chemistry, Dagestan State University) (click on image to enlarge)
A coating less than 30 nanometers thick prevents bacteria from growing on surgical sutures by generating reactive oxygen radicals that destroy bacterial cells while remaining safe for human tissue. Unlike current antibacterial sutures that lose effectiveness as their protective layers dissolve, this coating maintains its antibacterial properties indefinitely.
The coating consists of two distinct layers deposited on commercial Ethicon PROLENE 2-0 polypropylene sutures. An aluminum oxide base is applied directly to the suture through 50 ALD cycles using trimethylaluminum and water. The outer antibacterial layer (TiVOx) forms through 250 ALD supercycles using titanium chloride, vanadium oxychloride and water under precise conditions: 85 °C temperature, 1.0 Torr pressure, and ultrapure nitrogen atmosphere.
Laboratory tests demonstrated the coating’s effectiveness against common infection-causing bacteria. When exposed to Escherichia coli and Proteus vulgaris at concentrations of 103 and 105 colony-forming units per milliliter, uncoated sutures showed substantial bacterial growth after 72 hours – reaching concentrations of 8.0 ± 0.5 Log CFU/cm3 for E. coli and 4.5 ± 0.2 Log CFU/cm3 for P. vulgaris. Coated sutures showed zero bacterial growth throughout the test period.
The coating’s effectiveness stems from vanadium doping, which enhances titanium dioxide’s photocatalytic properties by increasing charge carrier lifetimes and shifting its activity into visible light. Even at such a small concentration of doped vanadium (0.15 weight percent), the coating generates reactive oxygen species – including superoxide anions and hydroxyl radicals – that destroy bacterial cells on contact while remaining below toxic thresholds. The aluminum oxide base prevents metal ions from migrating into surrounding tissue, by creating improved adhesion between the suture surface and the TiVOx coating.
Surgical trials in rabbits confirmed the coating’s real-world performance. The researchers created 4.5-centimeter incisions and closed them with both coated and uncoated sutures, sterilized by ultrasonication in 70% ethanol followed by UV radiation. After eight days, wounds closed with coated sutures showed 93% healing with no signs of infection or inflammation. Incisions using uncoated sutures achieved only 48% healing and displayed significant inflammatory responses.
The coating remains stable through multiple sterilization cycles in water, air, and various pH environments up to 70 °C. Scanning electron microscopy and energy-dispersive X-ray analysis confirmed uniform coverage and consistent vanadium concentration throughout the coating. The atomic-scale deposition process prevents crack formation that could allow bacterial penetration.
This development demonstrates how precise material engineering can prevent surgical infections without relying on chemical release or pharmaceutical approaches. The coating’s success on surgical sutures establishes a foundation for applying similar atomic-scale coatings to other medical devices requiring permanent bacterial resistance.
Additional research will test the coating against more bacterial species in larger clinical trials. The atomic layer deposition process, while precise, can scale up for commercial production while maintaining quality through automated process monitoring.
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