Introduction of Flexible Cyanoacrylates in Sutureless Gastric Closure.

Background Clinical effectiveness and safety of biological and synthetic adhesives in digestive closures have been evaluated. Their use is becoming more prevalent, as rigidity and inflexibility are its more remarkable weaknesses. However, little is known about their role in gastric and anastomotic closures. Moreover, usefulness of novel flexible types of synthetic adhesives as n-butyl-cyanoacrylate has not been assessed yet. Materials and Methods One centimeter long gastrotomy was performed in 24 male Wistar rats, which were divided depending on the type of closure method employed: manual USP 5/0 silk interrupted suture versus sutureless closure with Histoacryl Flexible (n-butyl-cyanoacrylate with softener) or Histoacryl Double Component (n-butyl-cyanoacrylate with softener and hardener). Microscopic evaluation of the suture viability and integrity was performed, and adhesion formation during the cicatrization process were assessed. During an 8-week follow-up clinical and histopathological aspects as well as hematologic and inflammatory biomarkers were studied. Results No differences among groups where found in any of the clinical, analytical, or histopathological issues assessed except for a higher incidence rate of adhesions in the Histoacryl Double Component group when compared with hand-sewn suture group (P = .04). Our results support experimental studies in large mammals (pigs) for further study of sutureless hollow viscera closure.

Standard Biocompatibility Studies Do Not Predict All Effects of PVA/CMC Anti-Adhesive Gel in vivo.

PURPOSE: PVA/CMC (polyvinyl alcohol/carboxymethyl cellulose) hydrogel fulfills various physiochemical properties required for an adhesion barrier and has shown good anti-adhesion properties in previous in vivo studies. In this investigation, we assessed the in vitro and in vivo biocompatibility of PVA/CMC gel and compared this to the functionality and promotion of wound healing for two surgical indications. METHODS: Standardized ISO10993 in vitro and in vivo biocompatibility studies, comprising cytotoxicity, genotoxicity, acute systemic toxicity, delayed contact and maximization sensitization test, intracutaneous reactivity and local muscle implantation, were performed on PVA/CMC gel. In the functional studies, PVA/CMC gel was applied - on the one hand - to a rabbit abdominal wall model enforced with a polypropylene mesh for testing the anti-adhesion properties and - on the other hand - to an end- to-end anastomosis model that was selected for surveying potential influences of different dosages of PVA/CMC gel on anastomotic wound healing. RESULTS: The ISO10993 methods indicated generally good biocompatibility properties, such as the absence of cytotoxic and mutagenic effects as well as no signs of systemic toxicity and sensitization potentials. No irritation effects were observed after the intracutaneous injection of lipophilic PVA/CMC sesame oil extract. However, the injection of hydrophilic PVA/CMC physiologic saline extract induced slight irritation. Following rabbit muscle implantation of the PVA membrane for 2, 4, 12, 26 and 52 weeks, a slight irritant effect was observed at 12 weeks due to the peak of phagocytosis. In the functionality tests, PVA/CMC gel showed good anti-adhesive effects in the abdominal wall model enforced with the mesh, with significantly lower and less tense adhesions compared to the untreated control. However, moderate signs of inflammation, especially in the spleen were observed after the intra-abdominal implantation of 3.3 ml PVA/CMC gel per kg body weight. In the end-to-end anastomosis model, PVA/CMC gel had no influence on wound healing. For dosages of 1-6 ml gel per treatment, no signs of intestinal leaks were detected, and tensile strength was equal to that of the untreated control, but again more moderate signs of inflammation in the spleen were observed at a dosage >3 ml. CONCLUSION: Comparing the standardized ISO10993 methods, anti-adhesive PVA/CMC gel displays good biocompatibility. However, those methods do not seem to be sensitive enough because the rabbit abdominal wall and the end-to-end anastomosis models display more effects with respect to the dosage and routes of the intra-abdominal resorption of PVA/CMC gel - with the recommended <2 ml PVA/CMC gel per kg body weight as a secure dosage.

A-Part Gel, an adhesion prophylaxis for abdominal surgery: a randomized controlled phase I-II safety study [NCT00646412].

BACKGROUND: Intra-abdominal surgical intervention can cause the development of intra-peritoneal adhesions. To reduce this problem, different agents have been tested to minimize abdominal adhesions; however, the optimal adhesion prophylaxis has not been found so far. Therefore, the A-Part(®) Gel was developed as a barrier to diminish postsurgical adhesions; the aim of this randomized controlled study was a first evaluation of its safety and efficacy. METHODS: In this prospective, controlled, randomized, patient-blinded, monocenter phase I-II study, 62 patients received either the hydrogel A-Part-Gel(®) as an anti-adhesive barrier or were untreated after primary elective median laparotomy. Primary endpoint was the occurrence of peritonitis and/or wound healing impairment 28 ± 10 days postoperatively. As secondary endpoints anastomotic leakage until 28 days after surgery, adverse events and adhesions were assessed until 3 months postoperatively. RESULTS: A lower rate of wound healing impairment and/or peritonitis was observed in the A-Part Gel(®) group compared to the control group: (6.5 vs. 13.8 %). The difference between the two groups was -7.3%, 90 % confidence interval [-20.1, 5.4 %]. Both treatment groups showed similar frequency of anastomotic leakage but incidence of adverse events and serious adverse events were slightly lower in the A-Part Gel(®) group compared to the control. Adhesion rates were comparable in both groups. CONCLUSION: A-Part Gel(®) is safe as an adhesion prophylaxis after abdominal wall surgery but no reduction of postoperative peritoneal adhesion could be found in comparison to the control group. This may at least in part be due to the small sample size as well as to the incomplete coverage of the incision due to the used application. TRIAL REGISTRATION: NCT00646412.

PVA gel as a potential adhesion barrier: a safety study in a large animal model of intestinal surgery.

BACKGROUND: Intra-abdominal adhesions following surgery are a major source of morbidity and mortality including abdominal pain and small bowel obstruction. This study evaluated the safety of PVA gel (polyvinyl alcohol and carboxymethylated cellulose gel) on intestinal anastomoses and its potential effectiveness in preventing adhesions in a clinically relevant large animal model. METHODS: Experiments were performed in a pig model with median laparotomy and intestinal anastomosis following small bowel resection. The primary endpoint was the safety of PVA on small intestinal anastomoses. We also measured the incidence of postoperative adhesions in PVA vs. control groups: group A (eight pigs): stapled anastomosis with PVA gel compared to group B (eight pigs), which had no PVA gel; group C (eight pigs): hand-sewn anastomosis with PVA gel compared to group B (eight pigs), which had no anti-adhesive barrier. Animals were sacrificed 14 days after surgery and analyzed. RESULTS: All anastomoses had a patent lumen without any stenosis. No anastomoses leaked at an intraluminal pressure of 40 cmH2O. Thus, anastomoses healed very well in both groups, regardless of whether PVA was administered. PVA-treated animals, however, had significantly fewer adhesions in the area of stapled anastomoses. The hand-sewn PVA group also had weaker adhesions and trended towards fewer adhesions to adjacent organs. CONCLUSION: These results suggest that PVA gel does not jeopardize the integrity of intestinal anastomoses. However, larger trials are needed to investigate the potential of PVA gel to prevent adhesions in gastrointestinal surgery.

Long-term active antimicrobial coatings for surgical sutures based on silver nanoparticles and hyperbranched polylysine.

The goal of this study was to develop a long-term active antimicrobial coating for surgical sutures. To this end, two water-insoluble polymeric nanocontainers based on hyperbranched polylysine (HPL), hydrophobically modified by either using glycidyl hexadecyl ether, or a mixture of stearoyl/palmitoyl chloride, were synthesized. Highly stabilized silver nanoparticles (AgNPs, 2-5 nm in size) were generated by dissolving silver nitrate in the modified HPL solutions in toluene followed by reduction with L-ascorbic acid. Poly(glycolic acid)-based surgical sutures were dip-coated with the two different polymeric silver nanocomposites. The coated sutures showed high efficacies of more than 99.5% reduction of adhesion of living Staphylococcus aureus cells onto the surface compared to the uncoated specimen. Silver release experiments were performed on the HPL-AgNP modified sutures by washing them in phosphate buffered saline for a period of 30 days. These coatings showed a constant release of silver ions over more than 30 days. After this period of washing, the sutures retained their high efficacies against bacterial adhesion. Cytotoxicity tests using L929 mouse fibroblast cells showed that the materials are basically non-cytotoxic.

In vitro degradation and drug release of a biodegradable tissue adhesive based on functionalized 1,2-ethylene glycol bis(dilactic acid) and chitosan.

Biodegradability and adhesive-associated local drug release are important aspects of research in tissue adhesive development. Therefore, this study focuses on investigating the in vitro degradation and drug release of a tissue adhesive consisting of hexamethylene diisocyanate functionalized 1,2-ethylene glycol bis(dilactic acid) and chitosan chloride. To prevent infections, ciprofloxacin hydrochloride (CPX·HCl) was incorporated into the adhesive. The influence of CPX·HCl on the adhesive reaction and adhesive strength was analyzed by FTIR-ATR-spectroscopy and tensile tests. The CPX·HCl release was investigated by HPLC. The degradation-induced changes at 37 °C were evaluated by gravimetric/morphological analyzes and micro-computer tomography. The antibiotic potential of the CPX·HCl loaded adhesive was determined by agar diffusion tests. The degradation tests revealed a mass loss of about 78 % after 52 weeks. The adhesive reaction velocity and tensile strength were not influenced by CPX·HCl. Using a 2 mg/g CPX·HCl loaded adhesive an inhibition of all tested bacteria was observed.

In vivo knot scoring model for a multifilament suture.

BACKGROUND: A surgical knot is the key feature to assure appropriate wound support while combining tissue edges. Little evidence is available on the in vivo behavior of knots and the evaluation of knots in the living tissue. This study introduces a knot score model, which is defined by microscopic evaluation and the loop-holding capacity. MATERIALS: In a double-blinded and comparative study, 3 surgeons placed 10 intramuscular single-loop sutures in the longissimus muscle group of the dorsolumbar region at each side parallel to the vertrebral column. For accomplishing the study, 72 rabbits and 3 calibers of a test and control suture were used. On the fourth day, the knot safety was assessed by microscopical and mechanical analyses for scoring and classifying the knots of the different suture materials into the defined categories for loop-holding capacity. The statistical evaluation was performed using Hodges-Lehmann rank score. A Wilcoxon test was used to estabilish a significant difference between the suture types. RESULTS: When comparing Novosyn (Aesculap AG) with Vicryl (Johnson & Johnson Medical GmbH) a comparable knot safety was assessed based on a 95% confidence interval. CONCLUSIONS: The new method compares the knot safety between 2 braided multifilament sutures in the living tissue. Results were discussed and examined for statistical significance.

Development of a biodegradable tissue adhesive based on functionalized 1,2-ethylene glycol bis(dilactic acid). II.

In body regions where damage and bleeding must be avoided, a substitute for mechanical tissue fixation by sutures or staplers is needed. Since tissue adhesives provide easy and fast handling they are a promising alternative. The present study reports the development and analysis of a tissue adhesive that consists of two adhesive components: hexamethylene diisocyanate (HDI) functionalized 1,2-ethylene glycol bis(dilactic acid) (ELA-NCO) and chitosan chloride. This composition was chosen based on preliminary studies on several chain elongation agents. The present study evaluates this adhesive system by IR-spectroscopy, tensile tests, and gel point measurements in comparison to fibrin glue. The system's in vitro biocompatibility was tested with mouse fibroblasts (L929) according to ISO 10993-5. Furthermore, an implantation study was performed in SPF-Wistar rats. The adhesive strength of manually applied mixtures or mixtures applied by double chamber syringes with a mixing extruder was determined to be significantly higher than that of fibrin glue on bovine muscle tissue at 37°C. Tensile strength increased further when exposure time of the adhesive was increased from 10 min to 48 h. The rheological gel point determination showed that the mixture of ELA-NCO/DMSO and chitosan chloride offers a time window large enough to readjust the fused joint during surgery, as opposed to fibrin glue. Additionally, the in vitro and in vivo biocompatibility studies of the adhesive system revealed no toxic effects on the surrounding tissue.

A hydrogel for adhesion prevention: characterization and efficacy study in a rabbit uterus model.

OBJECTIVE: Postoperative peritoneal adhesions following gynaecological surgery remain a clinically relevant problem. One approach to prevent adhesion formation is to apply physical barriers such as hydrogels. STUDY DESIGN: A physically crosslinked polyvinyl alcohol and carboxymethylcellulose (PVA/CMC) hydrogel (A-Part) was characterized in vitro. Three different traumatization methods were evaluated in a rabbit uterine study. To determine its anti-adhesion efficacy, the hydrogel was first tested in an in vivo pilot study and then in a larger trial to compare it with icodextrin 4% solution (Adept) and controls. RESULTS: Rheological measurements showed an increased elasticity of the hydrogel after freezing. In vivo experiments revealed a clear reduction in incidence, extent and severity of adhesions compared to the icodextrin 4% solution and the untreated control group. CONCLUSIONS: These results warrant further investigation of the PVA/CMC A-Part hydrogel in clinical trials focused on gynaecological procedures.

Efficacy of different hemostatic devices for severe liver bleeding: a randomized controlled animal study.

BACKGROUND: Correct hemostasis in liver surgery is hard to achieve because of the oozing bleeding. The aim of this study was to compare the potential benefits of a new compress to the 2 commercial hemostatic compresses. METHODS: Collagen- and cellulose-based hemostatics were investigated. A standardized resection was treated by applying different hemostatics in a randomized order, and bleeding times were measured. Macroscopic evaluation of the liver and tissue sampling for histological investigations were carried out after 21 days. RESULTS: The bleeding times of bovine collagen (BoCo), protein-coated equine collagen (PECo), and oxidized cellulose (OxCe) were 140 ± 88, 243 ± 140 (P = .005 vs BoCo), and 352 ± 70 s (P < .001 vs BoCo), respectively. Microscopic evaluation of the PECo presented fibrosis and significant inflammation in the implantation zone, whereas BoCo and OxCe caused only fibrosis in the wound area. CONCLUSION: BoCo showed significantly better hemostatic effect than PECo and OxCe.

A prospective, randomised, controlled, double-blind phase I-II clinical trial on the safety of A-Part Gel as adhesion prophylaxis after major abdominal surgery versus non-treated group.

BACKGROUND: Postoperative adhesions occur when fibrous strands of internal scar tissue bind anatomical structures to one another. The most common cause of intra-abdominal adhesions is previous intra-abdominal surgical intervention. Up to 74% of intestinal obstructions are caused by post surgical adhesions. Although a variety of methods and agents have been investigated to prevent post surgical adhesions, the problem of peritoneal adhesions remains largely unsolved. Materials serving as an adhesion barrier are much needed. METHODS/DESIGN: This is a prospective, randomised, controlled, patient blinded and observer blinded, single centre phase I-II trial, which evaluates the safety of A-Part Gel as an adhesion prophylaxis after major abdominal wall surgery, in comparison to an untreated control group. 60 patients undergoing an elective median laparotomy without prior abdominal surgery are randomly allocated into two groups of a 1:1- ratio. Safety parameter and primary endpoint of the study is the occurrence of wound healing impairment or peritonitis within 28 (+10) days after surgery. The frequency of anastomotic leakage within 28 days after operation, occurrence of adverse and serious adverse events during hospital stay up to 3 months and the rate of adhesions along the scar within 3 months are defined as secondary endpoints. After hospital discharge the investigator will examine the enrolled patients at 28 (+10) days and 3 months (+/-14 days) after surgery. DISCUSSION: This trial aims to assess, whether the intra-peritoneal application of A-Part Gel is safe and efficacious in the prevention of post-surgical adhesions after median laparotomy, in comparison to untreated controls.

Development of a biodegradable tissue adhesive based on functionalized 1,2-ethylene glycol bis(dilactic acid). I.

Tissue adhesives are a valuable alternative for mechanical tissue fixation by sutures or staples. Adhesives are desirable in body regions where damage and bleeding must be avoided. Tissue adhesives provide easy and fast handling. This study reports the development of a tissue adhesive based on 1,2-ethylene glycol bis(dilactic acid) (ELA) functionalized with hexamethylene diisocyanate (HDI) to produce isocyanate terminated ELA-NCO which was characterized by NMR and FTIR spectroscopy. ELA-NCO together with chain elongation agents forms an adhesive system suitable for tissue fixation. Several biodegradable polymers, such as hyaluronic acid, gelatin, chitosan acetate, and chitosan chloride were tested as chain elongation agents to obtain an adhesive system and studied on bovine muscle tissue to evaluate their adhesive strength and compared to fibrin glue. Tensile strength of glued joints was determined by a Zwick universal testing machine at ambient temperature. Mixtures of ELA-NCO and chitosan acetate or chloride, showed significantly higher adhesive strength than fibrin glue. Reaction between ELA-NCO and chitosan chloride produced polyurethane was traced by FTIR spectroscopy. NMR, FTIR, and rheological measurements demonstrated that ELA-NCO and chitosan chloride can be sterilized by gamma-rays or superheated water vapor without alterations, respectively. A mixture of ELA-NCO and chitosan chloride can be useful as medical tissue adhesive.

In-vivo studies on intraperitoneally administrated poly(vinyl alcohol).

The fate of poly(vinyl alcohol) (PVA, 195,000 g/mol) was studied in rabbits and nude mice after intraperitoneal (i.p.) administration. In-vivo fluorescence imaging using nude mice allowed for studies of tetramethylrhodamine labeled PVA distribution in the body and tracking the urinary excretion. The excreted PVA was studied in detail after collecting the urine of rabbits over a time period of 28 days. The PVA was separated from the urine by dialysis and analyzed by FTIR spectroscopy, (1)H-NMR spectroscopy, and size exclusion chromatography (SEC). Even after extensive dialysis, it was found that the excreted PVA showed a characteristic brownish color. The spectroscopic techniques revealed that this color was caused by the urine pigment (a metabolite of bilirubin) that could not be separated completely from the PVA. SEC showed unambiguously that the PVA with the very high molar mass had a glomerular permeability in the kidneys. Simultaneously, histological studies of the kidneys and the liver demonstrated that the tissues did not show any obvious damage.

Polyvinyl alcohol gel prevents adhesion re-formation after adhesiolysis in a rabbit model.

BACKGROUND: Chronic pain, infertility, and bowel obstructions are possible consequences of abdominal adhesions, which can highly affect the patient's quality of life. Patients in whom adhesiolysis has been performed are at high risk for recurrence of adhesions. For that reason, the present study focused on the re-formation of adhesions after adhesiolysis and on the possibility of avoiding it by using the adhesion barrier polyvinyl alcohol (PVA)-gel. MATERIALS AND METHODS: A randomized controlled study was conducted to prove the effectiveness of PVA-gel in reducing postoperative adhesion re-formation after relaparotomy. Moreover, ultrasound was evaluated as a noninvasive technique to determine abdominal adhesion in a rabbit model. All animals underwent an initial laparotomy to cause adhesions and subsequent adhesiolysis in the relaparotomy. PVA-gel was placed onto a side wall defect in 12 animals. Another 12 rabbits served as a control group without PVA-gel being used. Ultrasound before final laparotomy was performed to predict the prevalence of adhesions. Macroscopic evaluation of adhesion formation and planimetry were used to determine the amount of adhesion. RESULTS: PVA-gel was found to reduce significantly the amount of adhesion formation after relaparotomy (P = 0.0001) in comparison with the control group. Here severe adhesion formation was found to develop. The positive-predictive value (100%) for adhesion evaluation using ultrasound is highly satisfying in the rabbit model. CONCLUSIONS: Adhesion re-formation after relaparotomy was found to decrease significantly through the use of PVA-gel. Ultrasound as a noninvasive technique of adhesion detection is a sufficient and reliable method for detecting adhesion formations.

The new adhesion prophylaxis membrane A-part--from in vitro testing to first in vivo results.

INTRODUCTION: Formation of postoperative intra-abdominal adhesions is a severe problem in surgery. Apart from standard surgical procedures, a variety of different substances is available to prevent adhesions, but no universal method has been developed so far. A membrane consisting of polyvinyl alcohol (PVA) and carboxymethylcellulose (CMC) has been demonstrated to be antiadhesive. Here, the in vitro testing and first in vivo results in a rabbit sidewall model are reported. MATERIALS AND METHODS: A-part membrane contains a PVA/CMC mixture in a thickness of 40 microm. The composition, dissolution, tensile strength, and elasticity were examined to characterize the membrane in vitro. Experiments in vivo were carried out using a 'rabbit sidewall model' in which a standardized peritoneal trauma was covered with a 5 x 6 cm A-part membrane. Adhesion formation in A-part-treated animals was compared with that in Adept (15 mL/kg body weight) and untreated controls. RESULTS: An 80/20 PVA/CMC mixture forms a stable, elastic, transparent membrane, which can easily be placed intraoperatively. The dissolution shows a half-life of about 2 weeks [day 15: (45.1 +/- 4.9)% SD], which affords good adhesion protection during the initial critical phase of adhesion formation. In wet conditions, the membrane follows abdominal movements without tearing (tensile strength 5.0 +/- 4.2 N/cm SD; elasticity 29.5%). In a rabbit sidewall model, A-part membrane significantly reduced adhesion development by (83.1 +/- 31.5)% SD compared with the control and the Adept group (p < 0.001). CONCLUSION: The properties of the A-part membrane suggest that it may be useful as an antiadhesive in surgery. A-part is effective in in vivo testing as determined in a rabbit sidewall model.

Polyvinyl alcohol gel prevents abdominal adhesion formation in a rabbit model.

OBJECTIVE: To evaluate the function and biocompatibility of the new adhesion barrier PVA gel (polyvinyl alcohol + carboxymethylated cellulose) in the prevention of postsurgical peritoneal adhesions in a rabbit sidewall model. To evaluate and compare the routinely used 4% icodextrin. DESIGN: A prospective randomized controlled study was designed to evaluate the effectiveness of PVA gel in reducing postoperative adhesion formation. SETTING: Clinical laboratory in Germany. ANIMAL(S): Eighty female albino rabbits (HM Small Russian; 2.4-3.6 kg). INTERVENTION(S): All animals underwent trauma of the abdominal sidewall at the clinical laboratory. The PVA gel was placed at the sidewall defect in 50 cases. In two further groups, 18 animals had no treatment (control group), and 12 animals were treated with 4% icodextrin. MAIN OUTCOME MEASURE(S): Biocompatibility, mechanical properties of PVA gel, adhesion development, and device handling were observed. RESULT(S): The PVA gel showed good biocompatibility, no side effects, and excellent adhesion prevention. Although 100% of the untreated control group as well as the animals treated with 4% icodextrin developed adhesion formation, only around 25% of those rabbits that were treated with PVA gel showed adhesions. CONCLUSION(S): These data show that PVA gel functions as an excellent adhesion barrier.

Tracking the urinary excretion of high molar mass poly(vinyl alcohol).

The fate of poly(vinyl alcohol) (PVA) of weight average molar mass of 125,000 g/mol after administration into the peritoneum of rabbits has bean studied by various methods. PVA was spin-labeled with a nitroxide radical and then detected in urine using electron spin resonance (ESR) spectroscopy. Furthermore, unlabeled polymer was also administered to rabbits, then the urine was collected, dialyzed, precipitated, and the excretion of PVA was confirmed by size exclusion chromatography (SEC), FTIR spectroscopy, and (1)H NMR spectroscopy. ESR and SEC results show that, despite its relatively high molar mass, PVA is excreted through the kidneys without significant molar mass changes. Nevertheless, NMR and FTIR spectra show slight differences between the excreted and neat PVA. Possible causes of these discrepancies are discussed.

A-part gel-an efficient adhesion prevention barrier.

Two different poly(vinyl alcohol)-based gels (A-Part Gel) were compared and evaluated as possible adhesion prophylaxis gels. The gels were implanted to act as a physical barrier-and thus to prevent adhesions-in a rabbit sidewall model. The absorption time of any adhesion barrier is a critical parameter, since the wounded tissue needs to be covered during the healing process. Crosslinking by freeze-thawing helped to prolong the absorption time of the gels. To better understand the in vivo absorption, the gels were investigated in various physical in vitro methods such as decay measurements and experiments performed in a Soxhlet extraction thimble. The in vivo applicability of the gels by surgeons was judged in squeezing force measurements. The ability to cover the wounded area securely was measured with simple spreading experiments. Both gels could be squeezed out of the syringes easily and showed a homogenous spreading behavior. Comparing the two gels, the results of the in vitro absorption experiments were contradictive. Further, in vivo tests with correlations to the proposed in vitro measurements will reveal the correct interpretation. Nevertheless, the results in a pilot rabbit sidewall model were excellent for both A-Part gels, but only one gel was chosen for extended studies, showing only 20% adhesions when compared with the control group showing 100% strong adhesion formations. These data will be evaluated in other studies, and the use of an A-Part PVA-CMC gel for adhesion prevention has to be supported in clinical studies.

Poly(vinyl alcohol) membranes for adhesion prevention.

The abnormal joining of anatomic structures after abdominal and pelvic surgery can lead to such major complications as bowel obstruction or infertility. Poly(vinyl alcohol) (PVA) membranes and hydrogels were placed over the injured tissue to act as a physical barrier and prevent such adhesions from occurring in a rabbit sidewall model. The membranes were sutured into place to prevent their slipping or curling on the moist tissue. Various in vitro experiments (including testing for swelling and mechanical strength) were conducted in order to better understand the behavior of these membranes in the wound. The results showed that both the PVA membranes and PVA hydrogels significantly reduced the number and severity of adhesions in the rabbit sidewall model, and even indicated a distinct improvement over SEPRAFILM as antiadhesion barriers. Contact-angle measurements were taken in order to evaluate the surface properties of the membranes and hydrogels. Three approaches were taken to render the membranes more bioadhesive, and forego the need for future additional suturing: imprinting a texture onto the membrane, coating the membrane with carboxy methyl cellulose (CMC), and producing bi-layered, porous PVA membranes through a process of lyophilization. Though the surface of the PVA hydrogels is more hydrophilic than the surface of the PVA membranes, neither would adhere untreated to moist tissue. However, all three approaches aimed at improving their bioadhesion yielded excellent results and demonstrated that PVA could indeed be considered a viable method of adhesion prevention.