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BACKGROUND: Despite their routine use, surgical sutures are foreign bodies that induce a local immune reaction within adjacent tissue, the consequences of which include wound breakdown, “spitting,” and abscess formation. We have developed a novel pseudo-protein, poly(ester amide) (PEA) with the potential to modulate the immune response to implantable medical devices. We therefore hypothesized that PEA-coating would reduce the immune response to typically inflammatory suture materials in a standard in vivo model of tissue reactivity.
METHODS: 28 C57BL/6 mice underwent suture implantation in the bilateral gluteal muscles: PEA (polymer 8-Phe-4)-coated suture was implanted in the right gluteal muscle, and non-coated, control suture was implanted in the left. Silk suture was used in half of the mice, while plain-gut was used in the other half. Animals were sacrificed after 3, 7, 14 and 28 days and the bilateral gluteal muscles were harvested and processed for histology. Serial sections were taken along the axis of the suture track and stained with hematoxylin & eosin. The area of inflammation surrounding each suture was quantified and compared between groups. Data are given as mean±SEM.
RESULTS: PEA-coated silk and plain-gut sutures demonstrated lower mean areas of inflammation than their non-coated counterpoints at all time points. Furthermore, PEA-coated silk sutures resulted in significantly decreased mean areas of inflammation after 7 and 28 days compared with non-coated silk controls (686,897μm^2 ± 99,646μm^2 v. 2,095,447μm^2 ± 385,461μm^2, p<0.002 and 157,585μm^2 ± 25,422μm^2 v. 272,230μm^2 ± 40,156μm^2, p<0.03, respectively). PEA-coated plain-gut suture resulted in a similar significant decrease in local inflammation at 14 days (446,322 ± 359,359μm^2 v. 2,502,000μm^2 ± 462,461μm^2, p<0.005).
CONCLUSIONS: PEA-coating significantly decreases the immune response to plain-gut and silk sutures, materials typically associated with a robust inflammatory reaction. This reduction could potentially translate to a decrease in patient morbidity including a reduction in the rate of hypertrophic scarring and granuloma formation. Although further study following longer intervals of implantation are warranted prior to translation of this technology to the clinical realm, suture modification via PEA-coating may be an important means to improve the biocompatibility and inflammatory profile of next-generation sutures and minimize surgical site morbidity.