An adhesive bone marrow scaffold and bone morphogenetic-2 protein carrier for cartilage tissue engineering.

A chondroitin sulfate-bone marrow (CS-BM) adhesive hydrogel was used to localize rhBMP-2 to enhance articular cartilage tissue formation. Chondrocyte pellet culture revealed that 0.1 and 1 µg/mL of rhBMP-2 enhanced sulfated-GAG content. rhBMP-2 localization within the hydrogels was investigated, and it was found that BM, CS-NHS, and rhBMP-2 levels and time affected rhBMP-2 retention. Retention was modulated from 82 to 99% over a 3-week period for the material formulations investigated. To evaluate carrier efficacy, rhBMP-2 and bovine articular chondrocytes were encapsulated within CS-BM, and biochemical evaluation revealed significant increases in total collagen production with rhBMP-2. Histological analysis revealed more robust tissue formation and greater type-II collagen production with encapsulated rhBMP-2. Subsequently, a subcutaneous culture of hydrogels revealed increased total collagen, type-II to type-I collagen ratio, and sulfated GAG in samples carrying rhBMP-2. These findings indicate the development of a multifunctional system capable of localizing rhBMP-2 to enhance repair tissue quality.

Application of a collagen-based membrane and chondroitin sulfate-based hydrogel adhesive for the potential repair of severe ocular surface injuries.

This study was performed to evaluate the potential of a chondroitin sulfate-polyethylene glycol (CS-PEG) adhesive and collagen-based membrane (collagen vitrigel, CV) combination as a method to treat penetrating ocular injuries on the battlefield and to improve this method with two technologies: an antibiotic releasing CS-PEG adhesive and a corneal shaped CV. Burst testing using porcine cadaveric eyes, high-performance liquid chromatography, the Kirby-Bauer bacterial inhibition test, and CV implantations on the live and cadaveric rabbit eyes were performed. The ocular burst test showed CS-PEG adhesive could successfully repair 5-mm to 6-mm length wounds in the corneal and corneoscleral regions but would require CS-PEG + CV to treat larger wounds similar to those seen on the battlefield. In addition, high performance liquid chromatography and the Kirby-Bauer bacterial inhibition test presented evidence suggesting the vancomycin incorporated CS-PEG could inhibit Staphylococcus infection for 9 days. Furthermore, the curved CV showed an advantage by matching the corneal contour without any wrinkle formation. Although this pilot study showed a limited range of possible applications, we demonstrated that the combination of CS-PEG adhesive + CV is a promising method and the 2 technologies improve their applicability to the special demands of the battlefield.

Bonding and fusion of meniscus fibrocartilage using a novel chondroitin sulfate bone marrow tissue adhesive.

The weak intrinsic meniscus healing response and technical challenges associated with meniscus repair contribute to a high rate of repair failures and meniscectomies. Given this limited healing response, the development of biologically active adjuncts to meniscal repair may hold the key to improving meniscal repair success rates. This study demonstrates the development of a bone marrow (BM) adhesive that binds, stabilizes, and stimulates fusion at the interface of meniscus tissues. Hydrogels containing several chondroitin sulfate (CS) adhesive levels (30, 50, and 70 mg/mL) and BM levels (30%, 50%, and 70%) were formed to investigate the effects of these components on hydrogel mechanics, bovine meniscal fibrochondrocyte viability, proliferation, matrix production, and migration ability in vitro. The BM content positively and significantly affected fibrochondrocyte viability, proliferation, and migration, while the CS content positively and significantly affected adhesive strength (ranged from 60±17 kPa to 335±88 kPa) and matrix production. Selected material formulations were translated to a subcutaneous model of meniscal fusion using adhered bovine meniscus explants implanted in athymic rats and evaluated over a 3-month time course. Fusion of adhered meniscus occurred in only the material containing the highest BM content. The technology can serve to mechanically stabilize the tissue repair interface and stimulate tissue regeneration across the injury site.

An orthopedic tissue adhesive for targeted delivery of intraoperative biologics.

Tissue adhesives can bind together damaged tissues and serve as tools to deliver and localize therapeutics to facilitate regeneration. One emerging therapeutic trend in orthopedics is the use of intraoperative biologics (IOB), such as bone marrow (BM) and platelet-rich plasma (PRP), to stimulate healing. Here, we introduce the application of the biomaterial chondroitin sulfate succinimidyl succinate (CS-NHS) to deliver IOB in a hydrogel adhesive. We demonstrate the biomaterial's ability to bind various tissue types and its cellular biocompatibility with encapsulated human mesenchymal stem cells (hMSCs). Further, we examine in detail the CS-NHS adhesive combined with BM aspirate for use in bone applications. hMSCs were encapsulated in CS-BM and cultured for 5 weeks in osteogenic medium. Quantitative RT-PCR demonstrated osteogenesis via upregulation of the osteogenic transcription factor Runx2 and bone markers alkaline phosphatase and osteocalcin. Significant deposition of calcium and osteocalcin was detected using biochemical, histological, and immunohistochemical techniques. Shear testing demonstrated that the CS-BM adhesive exhibited an adhesive strength approximately an order of magnitude stronger than fibrin glue and approaching that of a cyanoacrylate adhesive. These results indicate that CS-NHS is a promising delivery tool for IOB in orthopedic applications requiring a strong, degradable, and biocompatible adhesive that supports bone growth.

A versatile pH sensitive chondroitin sulfate-PEG tissue adhesive and hydrogel.

We developed a chondroitin sulfate-polyethylene glycol (CS-PEG) adhesive hydrogel with numerous potential biomedical applications. The carboxyl groups on chondroitin sulfate (CS) chains were functionalized with N-hydroxysuccinimide (NHS) to yield chondroitin sulfate succinimidyl succinate (CS-NHS). Following purification, the CS-NHS molecule can react with primary amines to form amide bonds. Hence, using six arm polyethylene glycol amine PEG-(NH2)6 as a crosslinker we formed a hydrogel which was covalently bound to proteins in tissue via amide bonds. By varying the initial pH of the precursor solutions, the hydrogel stiffness, swelling properties, and kinetics of gelation could be controlled. The sealing/adhesive strength could also be modified by varying the damping and storage modulus properties of the material. The adhesive strength of the material with cartilage tissue was shown to be ten times higher than that of fibrin glue. Cells encapsulated or in direct contact with the material remained viable and metabolically active. Furthermore, CS-PEG material produced minimal inflammatory response when implanted subcutaneously in a rat model and enzymatic degradation was demonstrated in vitro. This work establishes an adhesive hydrogel derived from biological and synthetic components with potential application in wound healing and regenerative medicine.

Synthesis and characterization of a chondroitin sulfate-polyethylene glycol corneal adhesive.

PURPOSE: To describe the synthesis of a chondroitin sulfate-polyethylene glycol (CS-PEG) adhesive and characterize its physical and biological properties in vitro and in vivo. SETTING: Johns Hopkins University and a research facility, Baltimore, Maryland, USA. METHODS: Metabolic activity (WST-1 reagent) was used to evaluate the cytocompatibility of the adhesive with rabbit primary epithelial, stromal, and endothelial cells. Full-thickness corneal incisions (3.0 mm) in ex vivo porcine eyes were sealed with the adhesive, and burst pressure was evaluated to determine the effectiveness of the material in maintaining intraocular pressure (IOP). Finally, a partial-thickness incision was made in a swine cornea and then sealed using the adhesive. Two weeks postoperatively, both eyes were enucleated and examined grossly and histologically. RESULTS: In vitro results showed cytocompatibility of the tissue adhesive with corneal cells and an ability to seal full-thickness corneal incisions exposed to IOPs of 200 mm Hg and higher. Histological evidence from in vivo data confirmed that the CS-PEG material is biodegradable, induces minimal inflammatory response, resists epithelial cell ingrowth, and does not induce scar formation. CONCLUSIONS: The new adhesive was effective in restoring IOP and withstanding pressures greater than 200 mm Hg after being applied to a full-thickness corneal incision. The adhesive material was biocompatible with the 3 types of cells found in corneal tissue. When the adhesive was implanted in a live swine model, no adverse side effects were observed.

Multifunctional chondroitin sulphate for cartilage tissue-biomaterial integration.

A biologically active, high-strength tissue adhesive is needed for numerous medical applications in tissue engineering and regenerative medicine. Integration of biomaterials or implants with surrounding native tissue is crucial for both immediate functionality and long-term performance of the tissue. Here, we use the biopolymer chondroitin sulphate (CS), one of the major components of cartilage extracellular matrix, to develop a novel bioadhesive that is readily applied and acts quickly. CS was chemically functionalized with methacrylate and aldehyde groups on the polysaccharide backbone to chemically bridge biomaterials and tissue proteins via a twofold covalent link. Three-dimensional hydrogels (with and without cells) bonded to articular cartilage defects. In in vitro and in vivo functional studies this approach led to mechanical stability of the hydrogel and tissue repair in cartilage defects.