Erich K. Odermatt

Long-term active antimicrobial coatings for surgical sutures based on silver nanoparticles and hyperbranched polylysine

The goal of this study was to develop a long-term active antimicrobial coating for surgical sutures. To this end, two water-insoluble polymeric nanocontainers based on hyperbranched polylysine (HPL), hydrophobically modified by either using glycidyl hexadecyl ether, or a mixture of stearoyl/palmitoyl chloride, were synthesized. Highly stabilized silver nanoparticles (AgNPs, 2–5u2009nm in size) were generated by dissolving silver nitrate in the modified HPL solutions in toluene followed by reduction with L-ascorbic acid. Poly(glycolic acid)-based surgical sutures were dip-coated with the two different polymeric silver nanocomposites. The coated sutures showed high efficacies of more than 99.5% reduction of adhesion of living Staphylococcus aureus cells onto the surface compared to the uncoated specimen. Silver release experiments were performed on the HPL-AgNP modified sutures by washing them in phosphate buffered saline for a period of 30u2009days. These coatings showed a constant release of silver ions over more than 30u2009days. After this period of washing, the sutures retained their high efficacies against bacterial adhesion. Cytotoxicity tests using L929 mouse fibroblast cells showed that the materials are basically non-cytotoxic.

MonoMax Suture: A New Long-Term Absorbable Monofilament Suture Made from Poly-4-Hydroxybutyrate

A long-term absorbable monofilament suture was developed using poly-4-hydroxybutyrate (P4HB) made from a biosynthetically produced homopolymer of the natural metabolite 4-hydroxybutyrate. The suture, called MonoMax, has prolonged strength retention. At 12 weeks, a size 3-0 MonoMax suture retains approximately 50% of its initial tensile strength in vivo and is substantially degraded in one year with minimal tissue reaction. In contrast, PDS II monofilament suture (Ethicon, Inc., Somerville, NJ) has no residual strength in vivo after 12 weeks. In vivo, the MonoMax suture is hydrolyzed primarily by bulk hydrolysis, and is then degraded via the Krebs cycle. MonoMax is substantially more compliant than other monofilament sutures, and incorporates an element of elasticity. Its tensile modulus of 0.48u2009GPa is approximately one-third of the value of the PDS II fiber providing an exceptionally flexible and pliable fiber with excellent knot strength and security. These features are further enhanced by the fibers elasticity, which also improves knot security and may help prevent wound dehiscence. Because of its performance advantages, this suture may find clinical utility in applications where prolonged strength retention, and greater flexibility are required, particularly in procedures like abdominal wall closure where wound dehiscence is still a significant post-surgical complication.

In vivo knot scoring model for a multifilament suture.

Background A surgical knot is the key feature to assure appropriate wound support while combining tissue edges. Little evidence is available on the in vivo behavior of knots and the evaluation of knots in the living tissue. This study introduces a knot score model, which is defined by microscopic evaluation and the loop-holding capacity. Materials In a double-blinded and comparative study, 3 surgeons placed 10 intramuscular single-loop sutures in the longissimus muscle group of the dorsolumbar region at each side parallel to the vertrebral column. For accomplishing the study, 72 rabbits and 3 calibers of a test and control suture were used. On the fourth day, the knot safety was assessed by microscopical and mechanical analyses for scoring and classifying the knots of the different suture materials into the defined categories for loop-holding capacity. The statistical evaluation was performed using Hodges-Lehmann rank score. A Wilcoxon test was used to estabilish a significant difference between the suture types. Results When comparing Novosyn (Aesculap AG) with Vicryl (Johnson & Johnson Medical GmbH) a comparable knot safety was assessed based on a 95% confidence interval. Conclusions The new method compares the knot safety between 2 braided multifilament sutures in the living tissue. Results were discussed and examined for statistical significance.