Poster O7 - Biodegradable films for the prevention of post-operative adhesions in laparoscopic surgeries

Introduction: Post-operative adhesions are defined as fibrous tissue that form between different organ surfaces as a consequence of trauma caused by surgeries which lead to a multitude of complications such as organ dysfunction, difficulties in reoperation etc. Preventing the formation of adhesions involves utilizing physical barriers that separate the injured tissues from the surrounding areas. However, most physical barriers have inconsistent efficacies and difficulties with the application process in some cases.

An alternative method of decreasing the formation of adhesions is through the use of minimally invasive or laparoscopic surgeries over open surgeries. Laparoscopies decrease the trauma that the body is subjected to during surgery, thereby potentially decreasing the occurrence of adhesions. Although studies have shown that minimally invasive surgeries have lower cases of adhesions-related readmissions, the overall percentage of patients being reoperated due to complications arising from adhesions is still high. Physical barriers could also be used in minimally invasive surgeries to further decrease the onset of adhesions yet there is an added difficulty in inserting these barriers owing to the small size of the openings made in these surgeries.

We have developed a film comprised of a blend of high and low molecular weight polymers that is flexible enough to be utilized in laparoscopic surgeries. The blend contains a hydrophobic biodegradable polymer that gives the film its mechanical properties and a hydrophilic polymer that, by creating a hydration layer, inhibits deposition of fibrin and other cells necessary for adhesion formation onto the surface.

Materials and

Methods: The films are comprised of a blend of high and low molecular weight (HMW and LMW) polymers. These films are cast using the solvent evaporation technique: the polymers are dissolved in ethyl acetate, and the solution is then cast onto a glass plate and dried at 25oC for 24 hours followed by vacuum drying at 50oC.

Tensile testing of the films was conducted on a DMA in tensile mode with a force ramp of 0.5 N/s. Water Contact Angle of the films was measured by placing a 10µL deionized water droplet onto the film surface and taking an image with a high definition camera. The images were then analysed in ImageJ and the contact angle was measured. In vitro mass loss experiments in PBS and in vivo mass loss experiments in mice were conducted to investigate the degradation behaviour of the films.

In vivo efficacy of the films was investigated in a mouse cecal ligation model with a negative control group and a treatment group, with n = 3 in each group. The mice were sacrificed after 7 days, and the severity of adhesions were scored on a scale of 0 (no adhesions) - 4 (dense adhesions).

Results, Conclusions, and Discussions: Any polymeric film that is used as a physical barrier for adhesions prevention must possess certain properties: it should be able to maintain its integrity throughout the wound healing period; it should be biodegradable, preventing the necessity of a reoperation to remove the barrier; it should be able to prevent the formation of adhesions.

Tensile properties of the film decrease with addition of LMW polymer, although the tensile strength is comparable to currently used commercial adhesion barriers. The tensile properties, combined with the fact that the film was intact at the site of application without any loss of structure post in vivo testing implies that the film can maintain its structure throughout the wound healing period. From the water contact angle testing, we see a decrease in the contact angle with the addition of the LMW polymer, implying that the film surface is hydrophilic. In vitro and in vivo mass loss experiments show ~10% and 15% mass loss respectively after 3 weeks, confirming that most of the polymer film is present at the site. Although the degradation is lower than expected, this is not detrimental in the long run since the polymer blend does not elicit an inflammatory response, which would be beneficial in scenarios where the film is required to be present for longer timepoints.

In vivo studies of the film’s adhesions prevention efficacy in mouse models show that the polymer blend film had significantly reduced adhesions forming in the peritoneal space. Additionally, the minimal adhesions formed in the mice with films were weak adhesions requiring very little force in separating them away from tissue. This implies that the films show promise as an adhesion prevention barrier.

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