Thermogelling PLA-PEG-PLA used in development of post-surgical adhesion prevention

PolySciTech Division of Akina, Inc. (www.polyscitech.com) provides a wide array of biodegradable block copolymers. These include thermogelling PolyVivo AK100 Poly(DL-lactide)-b-Poly(ethylene glycol)-b-Poly(DL-lactide) (P(DL)LA-PEG-P(DL)LA

). Recently, researchers at Sichuan University investigated a similar polymer for its use in adhesion prevention. These thermogelling polymers are liquid at room temperature and then transition into a solid gel when the temperature is increased to 37C. This has many uses for applications such as depot drug delivery, vaccine delivery, and prevention of post-surgical adhesion. Post-surgical adhesion is a normal injury response of peritoneal surfaces during surgery which can cause significant morbidity, including bowel obstruction, female infertility, and chronic abdominal and pelvic pain (Diamond MP, Freeman ML. Clinical implications of postsurgical adhesions. Hum Reprod Update 2001; 7:567.) Nationally, about 5.7% of readmissions are due to adhesion with 3.8% requiring operation to fix the problem (Ellis H, Moran BJ, Thompson JN, et al. Adhesion-related hospital readmissions after abdominal and pelvic surgery: a retrospective cohort study. Lancet 1999; 353:1476.) so there is a great need to reduce these adhesions. The researchers found that P(DL)LA-PEG-P(DL)LA presented minimal cytotoxicity or hemolysis, due to its biocompatible nature. They also found that the thermogel polymer led to a significant post-operative adhesion in a rat sidewall defect bowel abrasion model. These results indicate the potential for use of these types of polymers to prevent surgical adhesion. Read more: Shi, K., Wang, Y.L., Qu, Y., Liao, J.F., Chu, B.Y., Zhang, H.P., Luo, F. and Qian, Z.Y., 2016. Synthesis, characterization, and application of reversible PDLLA-PEG-PDLLA copolymer thermogels in vitro and in vivo. Scientific reports, 6. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4707506/

“Abstract: In this study, a series of injectable thermoreversible and thermogelling PDLLA-PEG-PDLLA copolymers were developed and a systematic evaluation of the thermogelling system both in vitro and in vivo was performed. The aqueous PDLLA-PEG-PDLLA solutions above a critical gel concentration could transform into hydrogel spontaneously within 2 minutes around the body temperature in vitro or in vivo. Modulating the molecular weight, block length and polymer concentration could adjust the sol-gel transition behavior and the mechanical properties of the hydrogels. The gelation was thermally reversible due to the physical interaction of copolymer micelles and no crystallization formed during the gelation. Little cytotoxicity and hemolysis of this polymer was found, and the inflammatory response after injecting the hydrogel to small-animal was acceptable. In vitro and in vivo degradation experiments illustrated that the physical hydrogel could retain its integrity as long as several weeks and eventually be degraded by hydrolysis. A rat model of sidewall defect-bowel abrasion was employed, and a significant reduction of post-operative adhesion has been found in the group of PDLLA-PEG-PDLLA hydrogel-treated, compared with untreated control group and commercial hyaluronic acid (HA) anti-adhesion hydrogel group. As such, this PDLLA-PEG-PDLLA hydrogel might be a promising candidate of injectable biomaterial for medical applications.”