Sustained Ocular Delivery of Bevacizumab Using Densomeres in Rabbits: Effects on Molecular Integrity and Bioactivity.

Purpose: To demonstrate that a single administration of an anti-angiogenic monoclonal antibody, when integrated into a novel biodegradable Densomere composed only of the active pharmaceutical ingredient and polymer, maintains molecular integrity, sustained release, and prolonged bioactivity in vitro and in vivo for up to 12 months. Methods: Bevacizumab, a high-molecular-weight antibody (140,000-150,000 Da) was incorporated at 5% loading into Densomere microparticle carriers (DMCs) for injection to observe in vitro release over time from an aqueous suspension. The molecular integrity of the released bevacizumab was assessed by enzyme-linked immunosorbent assay (ELISA) and size-exclusion chromatography-high-performance liquid chromatography (SEC-HPLC). Anti-angiogenic bioactivity in vivo was assessed using the rabbit corneal suture model for suppression of neovascular encroachment from the limbus following a single subconjunctival administration. Results: Continuous release of bevacizumab in vitro was observed in serial samples over a period of 12 months. ELISA and SEC-HPLC yielded profiles from aqueous supernatant samples indistinguishable from the reference bevacizumab. A single subconjunctival administration in rabbit eyes significantly suppressed corneal neovascularization in vivo compared to control eyes for 12 months. Conclusions: The Densomere carrier platform maintained the molecular integrity of bevacizumab with a prolonged release profile in vitro and demonstrated sustained in vivo drug delivery with continuous bioactivity in the rabbit cornea eye model for 12 months. Translational Relevance: The Densomere platform provides a significant opportunity for prolonged delivery of biologics in ocular and other tissues.

Combined Hydrogel and Mesenchymal Stem Cell Therapy for Moderate-Severity Disc Degeneration in Goats.

Intervertebral disc degeneration is a cascade of cellular, structural, and biomechanical changes that is strongly implicated as a cause of low-back pain. Current treatment strategies have poor long-term efficacy as they seek only to alleviate symptoms without preserving or restoring native tissue structure and function. The objective of this study was to evaluate the efficacy of a combined triple interpenetrating network hydrogel (comprising dextran, chitosan, and teleostean) and mesenchymal stem cell (MSC) therapy targeting moderate-severity disc degeneration in a clinically relevant goat model. Degeneration was induced in lumbar discs of 10 large frame goats by injection of chondroitinase ABC. After 12 weeks, degenerate discs were treated by injection of either hydrogel alone or hydrogel seeded with allogeneic, bone marrow-derived MSCs. Untreated healthy and degenerate discs served as controls, and animals were euthanized 2 weeks after treatment. Discs exhibited a significant loss of disc height 12 weeks after degeneration was induced. Two weeks after treatment, discs that received the combined hydrogel and MSC injection exhibited a significant, 10% improvement in disc height index, as well as improvements in histological condition. Discs that were treated with hydrogel alone exhibited reduced tumor necrosis factor-α expression in the nucleus pulposus (NP). Microcomputed tomography imaging revealed that the hydrogel remained localized to the central NP region of all treated discs after 2 weeks of unrestricted activity. These encouraging findings motivate further, longer term studies of therapeutic efficacy of hydrogel and MSC injections in this large animal model. Impact statement Low-back pain is the leading cause of disability worldwide, and degeneration of the intervertebral discs is considered to be one of the most common reasons for low-back pain. Current treatment strategies focus solely on alleviation of symptoms, and there is a critical need for new treatments that also restore disc structure and function. In this study, using a clinically relevant goat model of moderate-severity disc degeneration, we demonstrate that a combined interpenetrating network hydrogel and mesenchymal stem cell therapy provides acute improvements in disc height, histological condition, and local inflammation.

Translation of an injectable triple-interpenetrating-network hydrogel for intervertebral disc regeneration in a goat model.

Degeneration of the intervertebral discs is a progressive cascade of cellular, compositional and structural changes that is frequently associated with low back pain. As the first signs of disc degeneration typically arise in the disc's central nucleus pulposus (NP), augmentation of the NP via hydrogel injection represents a promising strategy to treat early to mid-stage degeneration. The purpose of this study was to establish the translational feasibility of a triple interpenetrating network hydrogel composed of dextran, chitosan, and teleostean (DCT) for augmentation of the degenerative NP in a preclinical goat model. Ex vivo injection of the DCT hydrogel into degenerated goat lumbar motion segments restored range of motion and neutral zone modulus towards physiologic values. To facilitate non-invasive assessment of hydrogel delivery and distribution, zirconia nanoparticles were added to make the hydrogel radiopaque. Importantly, the addition of zirconia did not negatively impact viability or matrix producing capacity of goat mesenchymal stem cells or NP cells seeded within the hydrogel in vitro. In vivo studies demonstrated that the radiopaque DCT hydrogel was successfully delivered to degenerated goat lumbar intervertebral discs, where it was distributed throughout both the NP and annulus fibrosus, and that the hydrogel remained contained within the disc space for two weeks without evidence of extrusion. These results demonstrate the translational potential of this hydrogel for functional regeneration of degenerate intervertebral discs. STATEMENT OF SIGNIFICANCE: The results of this work demonstrate that a radiopaque hydrogel is capable of normalizing the mechanical function of the degenerative disc, is supportive of disc cell and mesenchymal stem cell viability and matrix production, and can be maintained in the disc space without extrusion following intradiscal delivery in a preclinical large animal model. These results support evaluation of this hydrogel as a minimally invasive disc therapeutic in long-term preclinical studies as a precursor to future clinical application in patients with disc degeneration and low back pain.

Evaluation of an In Situ Gelable and Injectable Hydrogel Treatment to Preserve Human Disc Mechanical Function Undergoing Physiologic Cyclic Loading Followed by Hydrated Recovery.

Despite the prevalence of disc degeneration and its contributions to low back problems, many current treatments are palliative only and ultimately fail. To address this, nucleus pulposus replacements are under development. Previous work on an injectable hydrogel nucleus pulposus replacement composed of n-carboxyethyl chitosan, oxidized dextran, and teleostean has shown that it has properties similar to native nucleus pulposus, can restore compressive range of motion in ovine discs, is biocompatible, and promotes cell proliferation. The objective of this study was to determine if the hydrogel implant will be contained and if it will restore mechanics in human discs undergoing physiologic cyclic compressive loading. Fourteen human lumbar spine segments were tested using physiologic cyclic compressive loading while intact, following nucleotomy, and again following treatment of injecting either phosphate buffered saline (PBS) (sham, n = 7) or hydrogel (implant, n = 7). In each compressive test, mechanical parameters were measured immediately before and after 10,000 cycles of compressive loading and following a period of hydrated recovery. The hydrogel implant was not ejected from the disc during 10,000 cycles of physiological compression testing and appeared undamaged when discs were bisected following all mechanical tests. For sham samples, creep during cyclic loading increased (+15%) from creep during nucleotomy testing, while for implant samples creep strain decreased (-3%) toward normal. There was no difference in compressive modulus or compressive strains between implant and sham samples. These findings demonstrate that the implant interdigitates with the nucleus pulposus, preventing its expulsion during 10,000 cycles of compressive loading and preserves disc creep within human L5-S1 discs. This and previous studies provide a solid foundation for continuing to evaluate the efficacy of the hydrogel implant.

In vitro characterization of a stem-cell-seeded triple-interpenetrating-network hydrogel for functional regeneration of the nucleus pulposus.

Intervertebral disc degeneration is implicated as a major cause of low-back pain. There is a pressing need for new regenerative therapies for disc degeneration that restore native tissue structure and mechanical function. To that end we investigated the therapeutic potential of an injectable, triple-interpenetrating-network hydrogel comprised of dextran, chitosan, and teleostean, for functional regeneration of the nucleus pulposus (NP) of the intervertebral disc in a series of biomechanical, cytotoxicity, and tissue engineering studies. Biomechanical properties were evaluated as a function of gelation time, with the hydrogel reaching ∼90% of steady-state aggregate modulus within 10 h. Hydrogel mechanical properties evaluated in confined and unconfined compression were comparable to native human NP properties. To confirm containment within the disc under physiological loading, toluidine-blue-labeled hydrogel was injected into human cadaveric spine segments after creation of a nucleotomy defect, and the segments were subjected to 10,000 cycles of loading. Gross analysis demonstrated no implant extrusion, and further, that the hydrogel interdigitated well with native NP. Constructs were next surface-seeded with NP cells and cultured for 14 days, confirming lack of hydrogel cytotoxicity, with the hydrogel maintaining NP cell viability and promoting proliferation. Next, to evaluate the potential of the hydrogel to support cell-mediated matrix production, constructs were seeded with mesenchymal stem cells (MSCs) and cultured under prochondrogenic conditions for up to 42 days. Importantly, the hydrogel maintained MSC viability and promoted proliferation, as evidenced by increasing DNA content with culture duration. MSCs differentiated along a chondrogenic lineage, evidenced by upregulation of aggrecan and collagen II mRNA, and increased GAG and collagen content, and mechanical properties with increasing culture duration. Collectively, these results establish the therapeutic potential of this novel hydrogel for functional regeneration of the NP. Future work will confirm the ability of this hydrogel to normalize the mechanical stability of cadaveric human motion segments, and advance the material toward human translation using preclinical large-animal models.

Preparation of hyaluronan-DNA matrices and films.

Natural carbohydrate is a class of underexplored polymers for gene delivery. The noninflammatory and nonimmunogenic properties of hyaluronan (hyaluronic acid, HA) are important in clinical situations. It has a role in wound repair and has great lubricating ability. Moreover, the presence of hyaluronidase in vivo enables any vehicle fabricated from HA to be degraded by enzyme-mediated erosion. When DNA is entrapped in a cross-linked HA vehicle, HA-DNA fragments are released on digestion by hyaluronidase. These fragments could serve both as microcarriers of DNA and its protective mechanism. This protocol describes preparation of water-insoluble HA-DNA matrices and films designed for clinical applications, and assays for verification of their bioactivities. Plasmid DNA (pDNA) encoding platelet-derived growth factor (PDGF) is coupled to the matrices that could be implanted into chronic wounds to accelerate their healing. pDNA encoding hyaluronan synthase 2 (HAS2) is coupled to the film that could initially serve as a physical barrier and subsequently a pDNA reservoir for sustaining HAS2 transfection. This would lead to continual HA production for preventing postsurgical adhesion.

A histopathologic basis for surgical debridement to promote healing of venous ulcers.

BACKGROUND: Pathologic analysis of deep tissue obtained during debridement of venous ulcers is often unnoticed in its importance. We previously reported pathologic findings on 139 patients with venous ulcers. The objective of this study was to correlate the pathologic findings in venous ulcers with wound healing to establish a negative margin for debridement. STUDY DESIGN: Consecutive patients with a lower extremity venous ulcer present for at least 4 weeks, presenting to a single wound healing center, were included. Wounds underwent aggressive surgical debridement beyond the subcutaneous level until judged to have a viable base. Specimens were scored based on cellularity, vascularity, collagen composition, inflammation, and dense fibrosis, with a highest possible score of 13. Healing was the primary outcome for analysis. RESULTS: Of the 26 patients who met inclusion criteria, only 50% of them (13 patients) with a total of 18 venous ulcers underwent surgical debridement available for pathologic analysis. Mean ulcer area was 34.7 cm(2) at initial presentation, and 89% of patients had a continuous positive healing curve as measured by decreasing wound area (from 34.7 cm(2) to 14.3 cm(2)). However, specimens with dense fibrosis, decreased cellularity, mature collagen, and pathology score less than 10 were predominantly nonhealing ulcers. CONCLUSIONS: Presence of dense fibrosis and high levels of mature collagen in deep tissue specimens are significant correlative factors in nonhealing of venous ulcers. We recommend deep debridement on all venous ulcers that are refractory to healing until the level of absence of dense fibrosis and mature collagen is reached to promote venous ulcer healing.

An injectable nucleus pulposus implant restores compressive range of motion in the ovine disc.

STUDY DESIGN: Investigation of injectable nucleus pulposus (NP) implant. OBJECTIVE: To assess the ability of a recently developed injectable hydrogel implant to restore nondegenerative disc mechanics through support of NP functional mechanics. SUMMARY OF BACKGROUND DATA: Although surgical intervention for low back pain is effective for some patients, treated discs undergo altered biomechanics and adjacent levels are at increased risk for accelerated degeneration. One potential treatment as an alternative to surgery for degenerated disc includes the percutaneous delivery of agents to support NP functional mechanics. The implants are delivered in a minimally invasive fashion, potentially on an outpatient basis, and do not preclude later surgical options. One of the challenges in designing such implants includes the need to match key NP mechanical behavior and mimic the role of native nondegenerate NP in spinal motion. METHODS: The oxidized hyaluronic acid gelatin implant material was prepared. In vitro mechanical testing was performed in mature ovine bone-disc-bone units in 3 stages: intact, discectomy, and implantation versus sham. Tested samples were cut axially for qualitative structural observations. RESULTS: Discectomy increased axial range of motion (ROM) significantly compared with intact. Hydrogel implantation reduced ROM 17% (P < 0.05) compared with discectomy and returned ROM to intact levels (ROM intact 0.71 mm, discectomy 0.87 mm, postimplantation 0.72 mm). Although ROM for the hydrogel implant group was statistically unchanged compared with the intact disc, ROM for sham discs, which received a discectomy and no implant, was significantly increased compared with intact. The compression and tension stiffness were decreased with discectomy and remained unchanged for both implant and sham groups as expected because the annulus fibrosus was not repaired. Gross morphology images confirmed no ejection of NP implant. CONCLUSION: An injectable implant that mimics nondegenerate NP has the potential to return motion segment ROM to normal subsequent to injury.

Rosiglitazone modulates the behaviors of diabetic host-derived fibroblasts in a carboxymethyllysine-modified collagen model.

Utilizing a three-dimensional in vitro glycated collagen model, we evaluated the therapeutic effects of a peroxisome proliferator-activated receptor-γ ligand, rosiglitazone, and its potential as a topical treatment of diabetic chronic wounds. Rosiglitazone induced fibroblast migration, α-smooth muscle actin production, and transformation into myofibroblasts in the presence of advanced glycation end products. Both transforming growth factor ß and peroxisome proliferator-activated receptor-γ expression were induced, while the receptor for advanced glycation end products was suppressed. Lastly, the reduced activities of matrix metalloproteinase-2 and matrix metalloproteinases-9 in the carboxymethyllysine-modified collagen matrices by rosiglitazone increases extracellular matrix deposition. Our findings identify rosiglitazone as a candidate for localized topical treatment of diabetic chronic wounds.

A multidisciplinary team approach to hydroxyurea-associated chronic wound with squamous cell carcinoma.

Hydroxyurea (HU) has been shown to induce a variety of cutaneous adverse reactions, including severe leg ulcers. This report shows a successful treatment of a HU-induced chronic wound associated with squamous cell carcinomas (SCC). A 62-year-old patient affected with polycythemia vera and treated with HU for 10 years, presented with a non healing ulcer on a left heel. The patient gave a history of suffering from the wound for over 2 years. Biopsy showed evidence of invasive SCC. The patient underwent Mohs surgery and a greater saphenous vein ablation for polycythemia vera-associated vascular complications. The wound consistently decreased in size following successive debridements and coverage with human skin equivalent. The wound healed completely after a 6-month period. A multidisciplinary team approach to the treatment proved to be effective resulting in healing of this multifactorial chronic ulcer.

The role of stem cells in the treatment of diabetic foot ulcers.

Diabetic foot ulcers (DFUs) are a significant and rapidly growing complication of diabetes and its effects on wound healing. Over half of diabetic patients who develop a single ulcer will subsequently develop another ulcer of which the majority will become chronic non-healing ulcers. One-third will progress to lower extremity amputation. Over the past decade, the outcomes for patients with DFUs ulcers have not improved, despite advances in wound care. Successful treatment of diabetic foot ulcers is hindered by the lack of targeted therapy that hones in on the healing processes dysregulated by diabetes. Stem cells are a promising treatment for DFUs as they are capable of targeting, as well as bypassing, the underlying abnormal healing mechanisms and deranged cell signaling in diabetic wounds and promote healing. This review will focus on existing stem cell technologies and their application in the treatment of DFUs.

A fibroblast/macrophage co-culture model to evaluate the biocompatibility of an electrospun Dextran/PLGA scaffold and its potential to induce inflammatory responses.

Fibroblasts and macrophages are the two major types of cells responding to implanted biomaterials. They play crucial roles in inflammatory responses, host-material interactions and tissue remodeling. However, the synergistic interactions of these two cell types with biomaterials are not fully understood. In this investigation, an in vitro fibroblast/macrophage co-culture system was utilized to examine the biocompatibility and the potential to induce inflammatory responses of an electrospun Dextran/PLGA scaffold. The scaffold did not affect the morphologies, attachments, proliferations and viabilities of both the fibroblasts and macrophages, cultured separately or together. Moreover, it only activated a small subset of the macrophages implicating a low potential to induce either severe acute or chronic inflammatory response. Additionally, fibroblasts played a role in prolonging macrophage activation in the presence of the scaffolds. Using antibody arrays, IL-10, SDF-1, MIP-1 gamma and RANTES were found to be up-regulated when the cells were incubated with the scaffolds. The results of subdermal implantation of the Dextran/PLGA scaffolds confirmed its biocompatibility and low inflammatory potential.

Mesenchymal stem cell therapy and delivery systems in nonhealing wounds.

OBJECTIVE: The objective of the study was to inform wound care practitioners of mesenchymal stem cell application for nonhealing wounds. Recent advances in delivery systems are also discussed in order to highlight potential improvements toward clinical application of stem cell therapy for chronic wounds. DATA SOURCES: MEDLINE and PubMed Central were searched for scientific studies regarding the use of mesenchymal stem cells and delivery systems in wound healing. STUDY SELECTION: Preclinical studies using stem cells as therapeutic modality for chronic wounds were selected for this review. DATA EXTRACTION: Information on study design, sample size and characteristics, stem cell source, type of delivery systems, and rate and time of wound closure was abstracted. DATA SYNTHESIS: Application of mesenchymal stem cells improved wound healing in experimental and clinical settings. Advances in stem cell therapy and delivery vehicles offer promising alternatives to current limited therapeutic modalities for chronic wounds. CONCLUSIONS: Stem cell therapy has recently emerged as a promising therapeutic strategy for nonhealing wounds. Further research is needed to evaluate the relationship between the various delivery systems and stem cells in order to maximize their therapeutic effects. Development of novel delivery vehicles for stem cells can open new opportunities for more effective cell therapy of chronic wounds.

In situ gelable interpenetrating double network hydrogel formulated from binary components: thiolated chitosan and oxidized dextran.

In situ gelable interpenetrating double-network hydrogels composed of thiolated chitosan (Chitosan-NAC) and oxidized dextran (Odex), completely devoid of potentially cytotoxic small molecule cross-linkers and that do not require complex maneuvers or catalysis, have been formulated. The interpenetrating network structure is created by Schiff base formations and disulfide bond inter-cross-linkings through exploiting the disparity of their reaction times. Compared with the autogelable thiolated chitosan hydrogels that typically require a relatively long time span for gelation to occur, the Odex/Chitosan-NAC composition solidifies rapidly and forms a well-developed 3D network in a short time span. Compared with typical hydrogels derived from natural materials, the Odex/Chitosan-NAC hydrogels are mechanically strong and resist degradation. The cytotoxicity potential of the hydrogels was determined by an in vitro viability assay using fibroblast as a model cell, and the results reveal that the hydrogels are noncytotoxic. In parallel, in vivo results from subdermal implantation in mice models demonstrate that this hydrogel is not only highly resistant to degradation but also induces very mild tissue response.

Delivery of rosiglitazone from an injectable triple interpenetrating network hydrogel composed of naturally derived materials.

An in situ gelable and biodegradable triple-interpenetrating network (3XN) hydrogel, completely devoid of potentially cytotoxic extraneous small molecule crosslinkers, is formulated from partially oxidized dextran (Odex), teleostean and N-carboxyethyl chitosan (CEC). Both the rheological profile and mechanical strength of the 3XN hydrogel approximate the combined characteristics of the three individual hydrogels composed of the binary partial formulations (i.e., Odex/CEC, Odex/teleostean, and CEC/teleostean). The 3XN hydrogel is considerably more resistant to fibroblast-mediated degradation compared to each partial formulation in cell culture models; this is attributable to the interpenetrating triple-network structure. The presence of teleostean in the 3XN hydrogel imparts cell affinity, constituting an environment amenable to fibroblast growth. in vivo subdermal injection into mouse model shows that the 3XN hydrogel does not induce extensive inflammatory response nor is there any evidence of tissue necrosis, further confirming the non-cytotoxicity of the hydrogel and its degradation byproducts. Importantly, the capability of the 3XN hydrogel to serve as a sustained drug delivery vehicle is confirmed using rosiglitazone as a model drug. The presence of rosiglitazone profoundly changes the cell/tissue interactions with the subdermally injected 3XN hydrogel. Rosiglitazone suppresses both the inflammatory response and tissue repair in a dose-dependent manner and considerably moderated the hydrogel degradation.

The functional behavior of a macrophage/fibroblast co-culture model derived from normal and diabetic mice with a marine gelatin-oxidized alginate hydrogel.

Tissues/cells-mediated biodegradable material degradation is epitomized by the constantly changing tissues/cell-implant interface, implicating the constant adaptation of the tissues/cells. Macrophages and fibroblasts are multi-functional cells highly involved in the interactions; the two cell types modulates the behaviors of each other, but their combinatorial functional behavior in the presence of interactive bioactive wound dressings has not been adequately examined. The activity is further complicated by the implantation of biodegradable materials, such as hydrogels commonly utilized as wound dressings, in a pathological environment and this is exemplified by the macrophages with a diabetic pathology producing an alternative cytokine profile which is implicated in wound healing delay. In this study, an in situ gelable formable/conformable hydrogel formulated from modified alginate and marine gelatin was used as a model biodegradable interactive wound dressing to elucidate the combinatorial behavior of macrophages/fibroblasts derived from both normal and diabetic hosts. Cell proliferation, migration and distribution were first characterized; this was followed by simultaneous quantitative detection of 40 inflammatory cytokines and chemokines by a protein microarray. The results showed that the macrophages/fibroblasts co-culture promoted fibroblasts proliferation and migration in the presence of the hydrogel; moreover, the expressions of inflammatory cytokines and chemokines were altered when compared with the corresponding fibroblasts or macrophages monocultures. The inflammatory cytokines patterns between the normal and diabetic hosts were considerably different.

In situ gelable glycation-resistant hydrogels composed of gelatin and oxidized alginate.

An in situ gelable glycation-resistant hydrogel has been prepared from oxidized alginate (Oalg) and gelatin. Aminoguanidine, an effective inhibitor of the glycation reaction, was first encapsulated in gelatin microspheres followed by incorporation into the hydrogel. The gelation process was monitored rheologically, and the results showed that the AMG-loaded Oalg/gelatin system solidified quickly at body temperature. Moreover, the hydrogels were highly porous, and the AMG-loaded microspheres dispersed in the hydrogels remained intact. Hydrogels' AMG loadings did not appear to change their degradation behaviors. AMG could be released from the hydrogels in a sustainable manner for a relatively short duration. Incorporation of AMG into the hydrogels resulted in imparting a glycation-resistant capability. Lastly, long-term in vitro incubation of all hydrogel formulations with fibroblasts did not reveal any cytotoxic potential.

Embolization of a common carotid aneurysm with rhVEGF coupled to a pH-responsive chitosan in a rat model.

OBJECT: Treatment of cerebral aneurysms by endovascular deployment of liquid embolic agents has been proposed as an alternative strategy to conventional coiling, and new materials are being developed for embolization. In this study, the authors used a single-injection, biocompatible, biodegradable and pH-responsive acrylated chitosan (aCHN) with conjugated vascular endothelial growth factor (rhVEGF) in a rat aneurysm model. METHODS: The efficacy of the aCHN formulation with rhVEGF was tested using a common carotid artery occlusion model in rats, and the extent of embolization was evaluated using quantitative, qualitative, and histopathological techniques after 14 days of implantation. RESULTS: The mean occlusion was significantly greater for the rhVEGF/aCHN-treated group (96.8 +/- 3.0%) than for the group receiving aCHN (74.7 +/- 5.6%) (p < 0.01). Through qualitative evaluation, intimal and medial proliferation were significantly greater with rhVEGF/aCHN than with aCHN and controls (p < 0.001). Degradation of the aCHN filler was monitored in concert with the production of extracellular matrix components. Macrophages migrated in and proliferated inside the occluded carotid artery lumens were identified by histological and immunostainings. Results showed resorption of chitosan with concurrent development of collagen and elastin into the vessel lumen, suggesting clot maturation into fibrosis. CONCLUSIONS: Chitosan with a bioactive agent such as rhVEGF showed excellent results in occluding aneurysms in a rat model.

Novel macromolecular crosslinking hydrogel to reduce intra-abdominal adhesions.

BACKGROUND: The aim of this study was to compare the anti-adhesion efficacy of a biodegradable, in situ, macromolecular cross-linking hydrogel made from oxidized dextran/N-carboxyethyl chitosan (Odex/CEC) with a commercially available carboxymethylcellulose/modified hyaluronan barrier film (Seprafilm; Genzyme Corporation, Cambridge, MA) in a rat cecum abrasion model. METHODS: The rat model utilized a cecal abrasion and abdominal wall insult surgical protocol. The 2% Odex/CEC hydrogel treatment was applied by syringe to coat both the cecal and the abdominal wall insults, while other animals were treated with Seprafilm applied to the cecal injury only. Control animals did not receive any treatment. Animals were sacrificed after post operative day 21 and adhesion severity was quantitatively graded using a whole number scale from 0 - 3. Histological analysis was also performed for animals receiving Odex/CEC hydrogel treatment and no treatment (control). RESULTS: Mean adhesion score was 2.09+/-1.22 for control animals, 1.00+/-1.00 for 2% Odex/CEC hydrogel animals, and 1.25+/-1.22 for Seprafilm animals. Hydrogel treated animals showed significantly lower adhesion scores than control animals (P<0.05), while Seprafilm demonstrated a marginally lower adhesion score (P<0.1) compared with the controls. Histological analysis of an Odex/CEC treated rat showed tissue repair and small fragments of hydrogel inside both healed abdominal and cecal surfaces. CONCLUSIONS: Both Seprafilm and the 2% Odex/CEC hydrogel showed a significantly decreased adhesion score compared with the control. However, the hydrogel, compared with Seprafilm, offers ease of application and ability to conform to complex tissue geometries that could provide surgeons with another prophylactic treatment to prevent abdominal adhesions.

Noninvasive and high-resolution optical monitoring of healing of diabetic dermal excisional wounds implanted with biodegradable in situ gelable hydrogels.

Closure of diabetic dermal chronic wounds remains a clinical challenge. Implant-assisted healing is emerging as a potential class of therapy for dermal wound closure; this advancement has not been paralleled by the development in complementary diagnostic techniques to objectively monitor the wound-healing process in conjunction with assessing/monitoring of implant efficacy. Biopsies provide the most objective morphological assessments of wound healing; however, they not only perpetuate the wound presence but also increase the risk of infection. A noninvasive and high-resolution imaging technique is highly desirable to provide objective longitudinal diagnosis of implant-assisted wound healing. We investigated the feasibility of deploying optical coherence tomography (OCT) for noninvasive monitoring of the healing of full-thickness excisional dermal wounds implanted with a novel in situ gelable hydrogel composed of N-carboxyethyl chitosan, oxidized dextran, and hyaluronan, in both normal and db/db mice. The results showed that OCT was able to differentiate the morphological differences (e.g., thickness of dermis) between normal and diabetic mice as validated by their corresponding histological evaluations (p < 0.05). OCT could detect essential morphological changes during wound healing, including re-epithelization, inflammatory response, and granulation tissue formation as well as impaired wound repair in diabetic mice. Importantly, by tracking specific morphological changes in hydrogel-assisted wound healing (e.g., implants' degradation and resorption, cell-mediated hydrogel degradation, and accelerated re-epithelization), OCT could also be deployed to monitor and evaluate the transformation of implanted biomaterials, thus holding the promise for noninvasive and objective monitoring of wound healing longitudinally and for objective efficacy assessment of implantable therapeutics in tissue engineering.