Fixation of Polypropylene Mesh On the Rabbit Abdominal Wall Using Poly L-Lactic Acid (plla) Nanosheet

Keiichi FUJINO, MD PhD, Manabu KINOSHITA, MD PhD, Hidekazu YANO, MD, Akihiro SAITOH, Toshinori FUJIE, PhD, Kahoko NISHIKAWA, PhD, Keiichi IWAYA, MD PhD, Shinji TAKEOKA, PhD, Daizoh SAITOH, MD PhD, Yuji TANAKA, MD PhD. Department of General Medicine, National Defense Medical College

Introduction: Polypropylene mesh (PPM) used to repair abdominal wall hernias often induces dense adhesions to visceral surface when the PPM is directly touched to the viscera. We have recently developed a biocompatible poly L-lactic acid (PLLA) nanosheet. This nanosheet with a thickness less than 100 nm has a unique potential to tightly adhere to skin and/or organs. Furthermore, the PLLA nanosheet can prevent adhesions to opposing tissues. Purpose: We have investigated the anti-adhesive and fixative effect of nanosheet on a rabbit model of intraperitoneal positioning of PPM.
Material and methods: PLLA nanosheet was fabricated by a combination of spin-coating method and a peeling technique with Poly vinyl alcohol (PVA) as a supporting film (Adv. Mater. 2009; 21:1-5). Male New Zealand white rabbits were studied. After shaving the abdomen, a midline laparotomy of approximately 8 cm was performed under clean conditions (but not complete sterile). 1. To examine the adhesive property, PPM measuring 2 × 2 cm were placed intraperitoneally on a paremedian location and fixated to the abdominal wall with a 4-0 Nylon suture. Thereafter, the PPM was covered with Seprafilm^TM or nanosheet measuring 4 × 4 cm. Subject rabbits were sacrificed one month after PPM placement. The degree of PPM adhesion was evaluated according to a quantitative and qualitative scoring system, based on the published literature. Foreign-body reaction to mesh materials was also examined histologically. 2. Next, we examined the fixative property. PPM (2 × 2 cm) was placed and covered with Seprafilm or nanosheet measuring 4 × 4 cm without fixation by suture. One month later, fixation of PPM was evaluated.
Results: No complications were encountered during the experiments. 1. Regarding the adhesive property, nanosheet overlapping showed no adhesive lesion of PPM. In contrast, Seprafilm group showed a certain adhesion in several rabbits (66%). The adhesion score was significantly lower in the nanosheet group than that in the Seprafilm group (score: 0 vs. 2.3). Infiltration of inflammatory cells was also suppressed in the nanosheet group compared with the Seprafilm group. 2. Regarding the fixative property, PPM was not fixed using the Seprafilm. However, some of the PPM (33%) were fixed using the nanosheet (without suture).
Conclusion: We have succeeded in fabricating a free-standing biocompatible PLLA nanosheet by nanotechnology. Overlapping treatment of nanosheet may be an effective in adhesion prophylaxis of intraperitoneal PPM. It may also have a possible beneficial effect on additional fixation of PPM.