Bioresorbable film for the prevention of adhesion to the anterior spine after anterolateral discectomy

Rheological Characterization of Genipin-Based Crosslinking Pigment and O-Carboxymethyl Chitosan-Oxidized Hyaluronic Acid In Situ Formulable Hydrogels

The aim of this study was to develop a material capable of rapidly absorbing bodily fluids and forming a resilient, adhesive, viscoelastic hydrogel in situ to prevent post-surgical adhesions. This material was formulated using O-carboxymethyl chitosan (O-CMCS), oxidized hyaluronic acid (OHA), and a crosslinking pigment derived from genipin and glutamic acid (G/GluP). Both crosslinked (O-CMCS/OHA-G/GluP) and non-crosslinked hydrogels (O-CMCS/OHA) were evaluated using a HAAKE™ MARS™ rheometer for their potential as post-surgical barriers. A rheological analysis, including dynamic oscillatory measurements, revealed that the crosslinked hydrogels exhibited significantly higher elastic moduli (G'), indicating superior gel formation and mechanical stability compared to non-crosslinked hydrogels. The G/GluP crosslinker enhanced gel stability by increasing the separation between G' and G″ and achieving a lower loss tangent (tan δ < 1.0), indicating robustness under dynamic physiological conditions. The rapid hydration and gelation properties of the hydrogels underscore their effectiveness as physical barriers. Furthermore, the O-CMCS/OHA-G/GluP hydrogel demonstrated rapid self-healing and efficient application via spraying or spreading, with tissue adherence and viscoelasticity to facilitate movement between tissues and organs, effectively preventing adhesions. Additionally, the hydrogel proved to be both cost effective and scalable, highlighting its potential for clinical applications aimed at preventing post-surgical adhesions.

Polycaprolactone/Polylactic Acid Membrane Fails to Prevent Laminectomy-induced Sprouting of CGRP- and SP-immunopositive Nerve Fibres in the Dura mater lumbalis of Rats

BACKGROUND CONTEXT

Mechanisms and prevention of failed back surgery syndromes are rarely known in the clinical context. It has been shown that laminectomy induces outgrowth of putative nociceptive peptidergic afferents in the dura mater lumbalis of rats.

PURPOSE

We aimed to investigate whether the application of a polycaprolactone/polylactic acid membrane (Mesofol) after surgery inhibits sensory hyperinnervation.

MATERIALS/METHODS

Adult Lewis rats were assigned to three groups: Control (no manipulation), Laminectomy and Laminectomy + Mesofol. Six weeks post-surgery, the durae were removed, immunohistochemically stained for CGRP- and SP-positive afferents and their density quantified.

RESULTS

In controls, CGRP- and SP-positive neurons were predominantly found in ventral but rarely observed in dorsal parts of the dura. Following laminectomy, the density of afferents significantly increased ventrally, resulting in a dense network of nerve fibers. In dorsal regions, neuronal sprouting of was observed. Covering the dura with Mesofol after laminectomy had no impact on nerve fibre outgrowth.

CONCLUSION

Application of Mesofol neither prevents nor significantly diminishes the laminectomy-induced increase in the density of peptidergic afferents.

Unidirectional Nanopore Dehydration Induces an Anisotropic Polyvinyl Alcohol Hydrogel Membrane with Enhanced Mechanical Properties

As a biocompatible, degradable polymer material, polyvinyl alcohol (PVA) can have a wide range of applications in the biomedical field. PVA aqueous solutions at room temperature can be cast into very thin films with poor mechanical strength via water evaporation. Here, we describe a novel dehydration method, unidirectional nanopore dehydration (UND). The UND method was used to directly dehydrate a PVA aqueous solution to form a water-stable, anisotropic, and mechanically robust PVA hydrogel membrane (PVAHM), whose tensile strength, elongation at break, and swelling ratio reached values of up to ~2.95 MPa, ~350%, and ~350%, respectively. The film itself exhibited an oriented arrangement of porous network structures with an average pore size of ~1.0 μm. At 70 °C, the PVAHMs formed were even more mechanically robust, with a tensile strength and elongation at break of 10.5 MPa and 891%, almost 3.5 times and 2 times greater than the PVAHM prepared at 25 °C, respectively. The processing temperature affects the velocity at which the water molecules flow unidirectionally through the nanopores, and could, thus, alter the overall transformation of the PVA chains into a physically crosslinked 3D network. Therefore, the temperature setting during UND can control the mechanical properties of the hydrogel membrane to meet the requirements of various biomaterial applications. These results show that the UND can induce the ordered rearrangement of PVA molecular chains, forming a PVAHM with superior mechanical properties and exhibiting a greater number of stronger hydrogen bonds. Therefore, the novel dehydration mode not only induces the formation of a mechanically robust and anisotropic PVA hydrogel membrane with a porous network structure and an average pore size of ~1.0 μm, but also greatly enhances the mechanical properties by increasing the temperature. It may be applied for the processing of water-soluble polymers, including proteins, as novel functional materials.

H-Bonding Supramolecular Hydrogels with Promising Mechanical Strength and Shape Memory Properties for Postoperative Antiadhesion Application

Development of a physical barrier with mechanical properties similar to human smooth muscle and an on-demand degradation profile is crucial for the clinical prevention of postoperative adhesion. Herein, a series of supramolecular hydrogels (PMI hydrogels) composed of poly(ethylene glycol) (PEG), methylenediphenyl 4, 4-diisocyanate (MDI), and imidazolidinyl urea (IU, hydrogen bonding reinforced factor) with biodegradability and high toughness are reported to serve as physical barriers for abdominal adhesion prevention. The tensile fracture strength and strain of the PMI hydrogels could be adjusted in the ranges of 0.6-2.3 MPa and 100-440%, respectively, and their Young's moduli (0.2-1.6 MPa) are close to that of human soft tissues like smooth muscle and skin tissue as well as they have outstanding shape memory properties. The PMI hydrogels show good cell and tissue biocompatibility, and the in vivo retention time is in accord with the needs for the postoperative antiadhesion physical barriers. Through an abdominal defect model on mice, this study shows that the PMI hydrogel can completely prevent tissue adhesion compared to the commercialized Seprafilm with high safety. Owing to the promising mechanical properties and good biocompatibility, the PMI hydrogels may be extended for various biomedical applications and the development of advanced flexible electronic devices.

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.

Adhesion Prevention after Laminectomy Using Silk-Polyethylene Glycol Hydrogels

Laminectomy is a common operation in spine surgery to reduce spinal cord and nerve pressure. However, scar tissues often form in the spinal canal and adhere to the dura surface, resulting in low back pain postsurgery. In the present study, biodegradable silk-polyethylene glycol (PEG) hydrogels are evaluated for adhesion prevention after laminectomies in New Zealand rabbits, with nondegradable expanded polytetrafluoroethylene (ePTFE) membranes and saline as controls. No significant difference among the three groups is observed within 2 weeks. Silk is fully degraded within 6 weeks, leaving a gap separating the scar tissue and the dura mater. Severe dural scar adhesion form in the saline control group after 8 weeks, while no or mild adhesion is observed in the ePTFE membrane and silk-PEG hydrogel samples. Human dermal fibroblasts (HS-865-SK cells) are cultured in the silk-PEG hydrogel extracts and on top of gel surfaces. Compared to the controls of tissue culture plate (no silk) and sonicated silk hydrogels (no PEG), the proliferation of fibroblasts in both conditions is significantly reduced initially but resumes after 120 h, suggesting the surface properties of the hydrogels and local, temporal release of PEG accounts for the adhesion prevention observed in vivo in this study.

Safety and effectiveness of a polyvinyl alcohol barrier in reducing risks of vascular tissue damage during anterior spinal revision surgery

STUDY DESIGN

This study was conducted as a controlled, prospective investigation to show the safety and efficacy of a polyvinyl alcohol (PVA) device in a sheep model.

OBJECTIVE

To evaluate the ability of a permanent PVA hydrogel barrier to reduce the risk of potential vessel damage during anterior vertebral revision surgery, to provide a nonadhesive barrier at the surgical site, and to create a surgical revision plane of dissection.

BACKGROUND

The development of scar tissue and adhesions presents a significant postoperative problem in spine surgery, where adhesion involvement of overlying structures can cause pain, neurovascular complications, and present a difficult surgical environment during revisions.

METHODS

The devices were implanted onto the ventral surface of exposed lumbar intervertebral discs using an anterolateral approach. One disc separated from the study site was also exposed to serve as a control. Three sheep each were then evaluated with an explant procedure at 30 and 90 days. Extensive sampling was undertaken to evaluate gross anatomic, micropathologic, and biochemical environments and properties of the device.

RESULTS

The structural properties and appearance of the device remained intact at both 30 and 90 days. The material remained flexible, hydrophilic, and soft, without visible resorption or decomposition. The material was well tolerated by the animal, with minimal histologic signs of inflammation or rejection. Tissue planes were easily able to be localized by the surgeon attempting to locate the prior surgical site at the time of resection.

CONCLUSIONS

The PVA vessel shield effectively protected the structures overlying the sheep spine during revision, providing a clear dissection plane for resection at repeat surgery. The overlying structures separated from the previous surgical site with no adhesion, and allowed safe separation of adjacent tissues without the use of sharp dissection.

Development of complete thoracic spinal cord transection model in rats for delayed transplantation of stem cells

STUDY DESIGN

In vivo study of a rat spinal cord injury model.

OBJECTIVES

To develop complete transection model of thoracic spinal cord using a polymer sheet and a microtube relevant for delayed transplantation of stem cells.

SUMMARY OF BACKGROUND DATA

Stem cell transplantation for the regeneration of spinal cord injuries has used animal models. However, current models suffer from inflammation and leakage, which lessens their usefulness in studying delayed stem cell transplantation.

METHODS

Thoracic spinal cord at T9 level of adult Sprague-Dawley rats was exposed and a 50:50 sheet of poly(D,L-lactic-coglycolic acid) was inserted, exposed spinal cord was completely transected, and collagen was filled between the gap between the proximal and distal stumps of transected spinal cord. A microtube was placed and fixed between the polymer surfaces facing each other. Behavior testing, magnetic resonance imaging, and myelography were performed to characterize the new complete transection with a gap formation and polymer insertion (GAP) model and to compare the GAP model with the control models. Human mesenchymal stem cells (hMSCs) were transplanted into 3 models and immunohistochemistry and western blot were performed.

RESULTS

The inserted poly(D,L-lactic-coglycolic acid) sheet was completely disappeared 10 weeks after operation, but the inserted microtube remained firmly fixed in its original position. Myelography of the GAP model showed no leakage of contrast medium around the injured spinal cord, whereas magnetic resonance imaging of the severe contusion and simple transection models showed some leakage of contrast medium. Immunohistochemistry and western blot after hMSCs transplantation indicated that transplanted hMSCs survived and migrated well in the GAP model, and the deposition of inflammatory cells in GAP model was less than a simple transection model or severe contusion model.

CONCLUSION

The developed GAP model is more relevant for delayed transplantation of stem cells for the study of regeneration of spinal cord injury of rats.