Prevention of adhesions post-abdominal surgery: Assessing the safety and efficacy of Chitogel with Deferiprone in a rat model

Introduction

Adhesions are often considered to be an inevitable consequence of abdominal and pelvic surgery, jeopardizing the medium and long-term success of these procedures. Numerous strategies have been tested to reduce adhesion formation, however, to date, no surgical or medical therapeutic approaches have been successful in its prevention. This study demonstrates the safety and efficacy of Chitogel with Deferiprone and/or antibacterial Gallium Protoporphyrin in different concentrations in preventing adhesion formation after abdominal surgery.

Materials and methods

112 adult (8–10 week old) male Wistar albino rats were subjected to midline laparotomy and caecal abrasion, with 48 rats having an additional enterotomy and suturing. Kaolin (0.005g/ml) was applied to further accelerate adhesion formation. The abrasion model rats were randomized to receive saline, Chitogel, or Chitogel plus Deferiprone (5, 10 or 20 mM), together with Gallium Protoporphyrin (250μg/mL). The abrasion with enterotomy rats were randomised to receive saline, Chitogel or Chitogel with Deferiprone (1 or 5 mM). At day 21, rats were euthanised, and adhesions graded macroscopically and microscopically; the tensile strength of the repaired caecum was determined by an investigator blinded to the treatment groups.

Results

Chitogel with Deferiprone 5 mM significantly reduced adhesion formation (p<0.01) when pathologically assessed in a rat abrasion model. Chitogel with Deferiprone 5 mM and 1 mM also significantly reduced adhesions (p<0.05) after abrasion with enterotomy. Def-Chitogel 1mM treatment did not weaken the enterotomy site with treated sites having significantly better tensile strength compared to control saline treated enterotomy rats.

Conclusions

Chitogel with Deferiprone 1 mM constitutes an effective preventative anti-adhesion barrier after abdominal surgery in a rat model. Moreover, this therapeutic combination of agents is safe and does not weaken the healing of the sutured enterotomy site.

Peptide Chitosan/Dextran Core/Shell Vascularized 3D Constructs for Wound Healing

Three-dimensional (3D) bioprinting has emerged to create novel cell-based therapies for regenerative medicine applications. Vascularized networks within engineered constructs are required, and toward this end, we report a promising strategy using core-shell (c/s) extrusion 3D-bioprinting technology that employs biomimetic biomaterials to construct regenerative, prevascularized scaffolds for wound care. A custom-designed cell-responsive bioink consisting of a 13% (w/v) cell-laden gelatin methacryloyl (GelMA) shell surrounding a peptide-functionalized, succinylated chitosan (C)/dextran aldehyde (D) cell-laden core was successfully bioprinted resulting in organized microdesigns exhibiting excellent cell viability and subsequent vessel formation. Our templating strategy takes advantage of GelMA's intrinsic thermoreversible properties of low degree of acryloyl functionalization used in combination with a lightly, chemically cross-linked peptide-CD core to serve as temporal structural supports that stabilize during extrusion onto a cooled platform. Mechanical integrity was further strengthened layer-by-layer via GelMA UV photo-cross-linking. We report the first example of GelMA used in combination with a peptide-CD bioink to c/s 3D-bioprint regenerative, prevascularized constructs for wound care. Particular cell adhesion and proteolytic peptide-CD functionalized pair combinations, P15/MMP-2 and P15/cRGD, were found to significantly increase growth of human bone-marrow-derived mesenchymal stems cells (hBMSCs) and human umbilical vein endothelial cells (HUVECs). The constructs delivered two cell types: hBMSCs in the shell bioink and HUVECs within the core bioink. Cord-like, natural microvascularization was shown with endothelial cell marker expression as confirmed by immunofluorescence (IF) staining exhibiting tubelike structures. In addition, in vitro skin wound healing activity of the construct showed a ∼twofold rate of wound closure. Overall, c/s 3D-bioprinted, peptide-CD/GelMA constructs provided the appropriate microenvironment for in vitro stem and endothelial cell viability, delivery, and differentiation. We foresee these custom constructs as representing a fundamental step toward engineering larger scale regenerative, prevascularized tissues.

Safety and Efficacy of Topical Chitogel- Deferiprone-Gallium Protoporphyrin in Sheep Model

Objectives: Increasing antimicrobial resistance has presented new challenges to the treatment of recalcitrant chronic rhinosinusitis fuelling a continuous search for novel antibiofilm agents. This study aimed to assess the safety and efficacy of Chitogel (Chitogel®, Wellington New Zealand) combined with novel antibiofilm agents Deferiprone and Gallium Protoporphyrin (CG-DG) as a topical treatment against S. aureus biofilms in vivo.

Methods: To assess safety, 8 sheep were divided into two groups of 7 day treatments (n = 8 sinuses per treatment); (1) Chitogel (CG) with twice daily saline flush, and (2) CG-DG gel with twice daily saline flush. Tissue morphology was analyzed using histology and scanning electron microscopy (SEM). To assess efficacy we used a S. aureus sheep sinusitis model. Fifteen sheep were divided into three groups of 7 day treatments (n = 10 sinuses per treatment); (1) twice daily saline flush (NT), (2) Chitogel (CG) with twice daily saline flush, and (3) CG-DG gel with twice daily saline flush. Biofilm biomass across all groups was compared using LIVE/DEAD BacLight stain and confocal scanning laser microscopy.

Results: Safety study showed no cilia denudation on scanning electron microscopy and no change in sinus mucosa histopathology when comparing CG-DG to CG treated sheep. COMSTAT2 assessment of biofilm biomass showed a significant reduction in CG-DG treated sheep compared to NT controls.

Conclusion: Results indicate that CG-DG is safe and effective against S. aureus biofilms in a sheep sinusitis model and could represent a viable treatment option in the clinical setting.

Chitosan Composites Synthesized Using Acetic Acid and Tetraethylorthosilicate Respond Differently to Methylene Blue Adsorption

The sol-gel and cross-linking processes have been used by researchers to synthesize silica-based nanostructures and optimize their size and morphology by changing either the material or the synthesis conditions. However, the influence of the silica nanostructures on the overall physicochemical and mechanistic properties of organic biopolymers such as chitosan has received limited attention. The present study used a one-step synthetic method to obtain chitosan composites to monitor the uptake and release of a basic cationic dye (methylene blue) at two different pH values. Firstly, the composites were synthesized and characterized by Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) to ascertain their chemical identity. Adsorption studies were conducted suing methylene blue and these studies revealed that Acetic Acid-Chitosan (AA-CHI), Tetraethylorthosilicate-Chitosan (TEOS-CHI), Acetic Acid-Tetraethylorthosilicate-Chitosan (AA-TEOS-CHI), and Acetic Acid-Chitosan-Tetraethylorthosilicate (AA-CHI-TEOS) had comparatively lower percentage adsorbances in acidic media after 40 h, with AA-CHI adsorbing most of the methylene blue dye. In contrast, these materials recorded higher percentage adsorbances of methylene blue in the basic media. The release profiles of these composites were fitted with an exponential model. The R-squared values obtained indicated that the AA-CHI at pH ~ 2.6 and AA-TEOS-CHI at pH ~ 7.2 of methylene blue had steady and consistent release profiles. The release mechanisms were analyzed using Korsmeyer-Peppas and Hixson-Crowell models. It was deduced that the release profiles of the majority of the synthesized chitosan beads were influenced by the conformational or surface area changes of the methylene blue. This was justified by the higher correlation coefficient or Pearson's R values (R ≥ 0.5) computed from the Hixson-Crowell model. The results from this study showed that two of the novel materials comprising acetic acid-chitosan and a combination of equimolar ratios of acetic acid-TEOS-chitosan could be useful pH-sensitive probes for various biomedical applications, whereas the other materials involving the two-step synthesis could be found useful in environmental remediation of toxic materials.

Polymer materials for prevention of postoperative adhesion

Postoperative adhesion (POA) is a common complication that often occurs after a variety of surgeries, such as plastic surgery, repair operations of abdominal, pelvic, and tendon, and so forth. Moreover, POA leads to chronic abdominal pain, secondary infertility in women, intestinal obstruction, and other severe complications, which significantly reduce the life quality of patients. In order to prevent the formation of POA, a number of strategies have been developed, among which an emerging method is physical barriers consisting of polymer materials. This review highlights the most commonly used natural and synthetic polymer materials in anti-adhesion physical barriers. The specific features of polymer materials are analyzed and compared, and the possible prospect is also predicted.

STATEMENT OF SIGNIFICANCE

Postoperative adhesion (POA) is a serious complication accompanied with various surgeries. Polymer material-based physical barriers have attracted a large amount of attention in POA prevention. The polymer barriers can effectively avoid the formation of fibrous tissues among normal organs by reducing the interconnection of injured tissues. In this review, specific features of the natural and synthetic polymer materials for application in POA prevention were presented, and the possible prospects were predicted. All in all, our work can provide inspiration for researchers to choose proper polymer materials for preclinical and even clinical anti-adhesion studies.

In situ cross-linking carbodiimide-modified chitosan hydrogel for postoperative adhesion prevention in a rat model

BACKGROUND

Postoperative intra-abdominal adhesion often causes many complications. Chitosan fluid has been used in clinic to prevent intra-abdominal adhesion. However, fluid can be easily diluted and cannot stay on the wound site. As hydrogel is able to form stable physical barrier to separate injured tissues, we developed a chitosan hydrogel for better prevention of intra-abdominal adhesion in this study.

METHODS

We synthesized a carbodiimide-derivatized chitosan gelatin (cd-CS-gelatin) hydrogel and investigated its rheological properties. A rat model was used to compare the anti-adhesion effect of chitosan hydrogel and fluid. The wounds were created with damage of the underlying muscle of the abdominal wall and the serosal layer of the cecum. They were coated with chitosan fluid or cd-CS-gelatin hydrogel. At day 14 after surgery, the animals were euthanized and intra-abdominal adhesion was assessed.

RESULTS

The cd-CS-gelatin hydrogel solidified within 3min after the mixing of the reagents. The cecum-abdomen adhesion occurred in all rats without anti-adhesion treatment. The application of cd-CS-gelatin significantly reduced the adhesion rate from 100% to 50%, compared the chitosan fluid only to 88%. The decrease of adhesion breaking strength also manifested that cd-CS-gelatin was more effective than chitosan fluid to reduce postsurgical intra-abdominal adhesion formation.

CONCLUSIONS

Chitosan hydrogel is more effective than chitosan fluid to prevent postoperative cecum-abdomen adhesion. It indicates that hydrogel could be a more promising state than liquid to prevent postoperative intra-abdominal adhesion.

Biodegradable liposome-encapsulated hydrogels for biomedical applications: a marriage of convenience

Liposome-encapsulated hydrogels have emerged as an attractive strategy for medical and pharmaceutical applications.

Reducing the Oxidation Level of Dextran Aldehyde in a Chitosan/Dextran-Based Surgical Hydrogel Increases Biocompatibility and Decreases Antimicrobial Efficacy

A highly oxidized form of a chitosan/dextran-based hydrogel (CD-100) containing 80% oxidized dextran aldehyde (DA-100) was developed as a post-operative aid, and found to significantly prevent adhesion formation in endoscopic sinus surgery (ESS). However, the CD-100 hydrogel showed moderate in vitro cytotoxicity to mammalian cell lines, with the DA-100 found to be the cytotoxic component. In order to extend the use of the hydrogel to abdominal surgeries, reformulation using a lower oxidized DA (DA-25) was pursued. The aim of the present study was to compare the antimicrobial efficacy, in vitro biocompatibility and wound healing capacity of the highly oxidized CD-100 hydrogel with the CD-25 hydrogel. Antimicrobial studies were performed against a range of clinically relevant abdominal microorganisms using the micro-broth dilution method. Biocompatibility testing using human dermal fibroblasts was assessed via a tetrazolium reduction assay (MTT) and a wound healing model. In contrast to the original DA-100 formulation, DA-25 was found to be non-cytotoxic, and showed no overall impairment of cell migration, with wound closure occurring at 72 h. However, the lower oxidation level negatively affected the antimicrobial efficacy of the hydrogel (CD-25). Although the CD-25 hydrogel's antimicrobial efficacy and anti-fibroblast activity is decreased when compared to the original CD-100 hydrogel formulation, previous in vivo studies show that the CD-25 hydrogel remains an effective, biocompatible barrier agent in the prevention of postoperative adhesions.