Polygalacturonic acid/Hyaluronic acid-based Materials for the Prevention of Postoperative Tissue Adhesion

• Main Authors: Hsiu-Hui Peng, 彭秀慧
• Other Authors: Yng-Jiin Wang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/13998182330536336189

博士 === 國立陽明大學 === 醫學工程研究所 === 100 === Tissue adhesion forms frequently between two injured structures following periotoneal surgery, and it may result in serious postsurgical complications such as pain, infertility, and fatal bowel obstruction. Physical barrier (or in combination with pharmacological active ingredient) is a common medical device used to prevent postsurgical adhesion. Physical barriers, as gel or film, are commonly crosslinked to obtain an insoluble structure. Unfortunately, cytotoxicity caused by the residual crosslinking agent is always a major concern for clinical use. In this study, polygalacturonic acid (PGA) and hyaluronic acid (HA) were modified and crosslinked via the formation of disulfide bond or Schiff base under a physiological condition to fabricate anti-adhesive medical devices. The physical preoperties, biocompatibility, and potential applications of these anti-adhesion hydrogel/film materials were investigated. For the disulfide-crosslinking system, PGA or HA was thiolated by coupling with cysteine using EDC/NHS as the activating agents. Approximately 752±77 mmoles and 337±72 mmoles of cysteine were conjugated per gram of PGA and HA, respectively. The three disulfide-crosslinked films developed (in the order of PGAcys , PHcys , HAcys) have water contents of 43%, 47%, and 72 % , and gel contents of 92%, 85%, and 81%, respectively. It appears that a less amount of cysteine was conjugated to HA with a lower crosslinking degree of the HAcys film as compared to PGAcys . The disulfide bond formation via redox reaction of the thiolated polymers can be demonstrated after the reduction of the films with 2-mercaptoethanol which renders the insoluble films water-soluble. This demonstrates the reversibility and importance of disulfide bond formation in stabilizing the film. To evaluate the feasibility of using PGA/HA films as drug carriers, an anti-inflammatory drug, Rosmarinic acid (RA), was loaded in all three films. The RA loaded was released with initial burst of ~ 80% within 15 minutes, followed by a steady zero order release of 0.38ng/min, 0.40ng/min, and 0.24ng/min for PGAcys , PHcys , and HAcys, respectively. This type of releasing behaviour is useful to ease the early inflammation for preventing postsurgical adhesion. Of the three films studied, PGAcys and PHcys films have stiffness suitable for surgical operation and therefore were chosen for further in vitro and in vivo studies. Results of the in vitro tests indicate that the PGAcys and PHcys films are not cytotoxic and exhibit anti-adhesive behaviour to L929 fibroblast cells. Results of the animal implant study show that PGAcys and PHcys films either with or without drug loading exhibit superior anti-adhesion property as compared with Seprafilm and the control groups. The RA-loaded films induce fewer white blood cells gathered around the wound site and also increase the antioxidant capacity in the peritoneum. Hydrogel crosslinked by Schiff base formation was also developed in this study. For this case, PGA was oxidized with sodium periodate to yield PGAALD of approximate 28% modification. In addition, HA was coupled with adipic dihydrazide (ADH) to obtain HAADH with about 56% of the repeating di-saccharide units modified. After mixing PGAALD and HAADH, the gelation process occurred within 1 min via Schiff base formation between aldehyde and amino groups. The physical properties of the PH (PGAALD-HAADH) hydrogel were compared with those of the HH (HAALD-HAADH) hydrogel. Results show that PH hydrogel has a lower water content (~95%), a lower swelling ratio (~18), a slower degradation rate, and about the same compressive modulus as compared with the HH hydrogel. Results of the in vitro tests show that PH hydrogel is cytotoxic and exhibits anti-adhesive behavior to L929 cells. Both PH and HH gels reduce the postsurgical adhesion by 50%. Histological results indicate that white blood cells were found near the PH hydrogel but they decreased in number with time. Besides, cells did not infiltrate into the bulk region of the PH hydrogel. Hence, PH gel seems to be a better choice to prevent the tissue adhesion in the long-term repair process. The PGA-based anti-adhesion gel and film developed in this study have superior anti-adhesion potency, and thus they both have great potential for future clinical applications.