PubMed · 15468821
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M P Ginebra, C Aparicio, E Engel, M Navarro, F Javier Gil, J A Planell. 2004. Calcium phosphate bone substitutes.. https://pubmed.ncbi.nlm.nih.gov/15468821/
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Resorbable scaffolds for anterior cruciate ligament (ACL) reconstruction should provide temporary mechanical function then gradually breakdown while promoting matrix synthesis by local cells. Crosslinking influences collagen's mechanical properties, degradation rate, and interactions with cells. Our objective was to compare the effects of different crosslinkers on cellularity and mechanical properties during long-term (8 week) culture of collagen fiber scaffolds. Fibers were fabricated from an acid-insoluble dispersion of bovine dermal collagen and crosslinked with either ultraviolet irradiation (UV; a physical crosslinker) or 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC; a chemical crosslinker). Scaffolds consisted of 50 fibers bundled in parallel. Initial attachment of fibroblasts was similar on both scaffolds; however, from 1 to 8 weeks in culture, UV-crosslinked scaffolds had significantly more cells attached than EDC-crosslinked scaffolds. The initial breaking load (3.50 N) and stiffness (2.23 N/mm) of EDC-crosslinked scaffolds were significantly greater than those of UV-crosslinked scaffolds (2.32 N; 1.21 N/mm) and were unaffected by long-term fibroblast culture. In contrast, the load-bearing capacity of fibroblast-seeded UV-crosslinked scaffolds decreased 60% to 0.91 N after 8 weeks in culture. EDC-crosslinked scaffolds maintained strength and moderate cellularity; UV-crosslinked scaffolds, in contrast, were highly cellular, but had poor mechanical properties that decreased during culture. These in vitro results suggest that collagen fiber scaffolds crosslinked with EDC may be more suitable for ACL reconstruction than those crosslinked with UV.
The control of bleeding is a frequently encountered therapeutic problem, particularly during dental surgery. The most efficient substances used to resolve this problem are not risk-free because of their animal or human origins, so cellulosic materials are potentially of interest. The aim of this study was to develop a resorbable macroporous cellulosic material for use as a resorbable hemostatic agent in bone sites. The degradation and the cytocompatibility of the cellulosic material versus controls were evaluated and its behaviour in vivo was studied. An original process using calcium carbonate powder as inverse matrix was used to develop a macroporous material. In order to predegrade the cellulosic material for hemostatic use, oxidation was performed with periodate. A dialdehyde component unstable at physiological pH was thus obtained. The material was found to have cytotoxicity, biocompatibility, and resorption properties similar to control but its hemostatic power was higher.
A subretinal drug delivery system was developed to overcome the limitations of current treatments for retinal disease. A rod-shaped implant was made by embedding the corticosteroid triamcinolone acetonide within a biodegradable polycaprolactone polymer matrix. The implant was fabricated by homogeneously mixing the polymer and drug in solvent. The mixture was then dried, melted, and extruded, and the prepared solid form was drawn into a filament. The rods were mechanically sectioned to a length of 2 mm with a diameter of up to 320 microm. The rods were successfully implanted into the subretinal space of six rabbits. No complications were observed during the 4-week follow-up period. Initial observations of the implantation and elution characteristics revealed that polycaprolactone is well tolerated by the retinal tissue and that the implant can elute steroid for a period of at least 4 weeks without eliciting inflammatory response or complications. In vitro drug elution rates of different polymer to drug ratios and geometries into a balanced salt solution/bovine serum albumin (1%) solution showed an early rapid-release phase and late first-order phase. Histology and device retrieval after implantation revealed minimal encapsulation and good preservation of cellular morphology during the follow-up period and a more fibrous polymer microstructure of the implant.