Effect of a freeze-dried CMC/PLGA microsphere matrix of rhBMP-2 on bone healing

Abstract

The hypothesis of this research was that implants of poly(lactide-co-glycolide) (PLGA) microspheres loaded with bone morphogenetic protein-2 (rhBMP-2) and distributed in a freeze-dried carboxymethylcellulose (CMC) m atrix would produce more new bone than would matrix implants of non-protein-loaded microspheres or matrix implants of only CMC. To test this hypothesis it was necessary to fashion microsphereloaded CMC implants that were simple to insert, fit precisely into a defect, and would not elicit swelling. Microspheres were produced via a water-in-oil-in-water double-emulsion system and were loaded with rhBMP-2 by soaking them in a buffered solution of the protein at a concentration of 5.4 mg protein per gram of PLGA. Following recovery of the loaded microspheres by lyophilization, matrices for implantation were prepared by lyophilizing a suspension of the microspheres in 2% CMC in flat-bottom tissue culture plates. Similar matrices were made with 2% CMC and with 2% CMC containing blank microspheres. A full-thickness calvarial defect model in New Zealand white rabbits was used to assess bone growth. Implants fit the defect well, allowing for direct application. Six weeks postsurgery, defects were collected and processed for undecalcified histology. In vitro, 60% of the loaded rhBMP-2 released from devices or microspheres in 5 to 7 days, with the unembedded microspheres releasing faster than those embedded in CMC. In vivo, the rhBMP-2 microspheres greatly enhanced bone healing, whereas nonloaded PLGA microspheres in the CMC implants had little effect. The results showed that a lyophilized device of rhBMP-2/PLGA microspheres in CMC was an effective implantable protein-delivery system for use in bone repair.

Bone morphogenetic proteins in tissue engineering: the road from laboratory to clinic, part II (BMP delivery)

“…Periodontal regeneration in dogs (Chen et al, 2007b) acid in copolymer polylactic-co-glycolic acid (PLGA), biodegradation is controlled by changing the proportions of each of the two materials, since PLA degrades much more slowly than PGA. Microspheres of PLGA have since then been evaluated in diverse animal models, such as in rat calvarial bone defects (Kenley et al, 1994), rat femurs (Lee et al, 1994) and in calvarial defects in rabbits (Schrier et al, 2001), forming much more bone when BMPs were delivered via the PLGA particles. Interesting work has been developed by Ruhé and colleagues, using microspheres of PLGA in combination with Ca-P cement, as carriers for rhBMP-2 delivery (Ruhe et al, 2005).…”

Preparation of BMP-2 Containing Bovine Serum Albumin (BSA) Nanoparticles Stabilized by Polymer Coating

“…In vitro studies have shown the bioactivity of BMP-2 was maintained during encapsulation into such microparticles (250-430 µm), despite exposure to organic solvents (32). The PLGA particles were effective in stimulating bone formation in several animal models, such as in rat femurs (33), calvarial defects in rabbits (34), and ovine vertebral bodies (35). While some of these studies measured growth factor release, subsequent studies focused on controlling the BMP-2 release from the PLGA particles by embedding them in a calcium phosphate cement (36) or by surface-grafting heparin to the particles for BMP-2 binding (37).…”

Proteína Morfogenética Ósea y su Opción como Tratamiento de la Fisura Alveolar

“…Estudios han demostrado que la liberación de rhBMP-2 desde una MP de PLGA es afectada directamente por el peso molecular, la relación entre PLA y PGA, la naturaleza del grupo terminal y la cantidad de rhBMP-2 incorporada en la MP (Anderson et al,2012). En el año 2001 se comparó el uso de MP de PLGA con rhBMP-2 en una matriz de carbometil-celulosa y la misma matriz con MP sin rhBMP-2 (Schrier et al, 2001). En este trabajo, se estudió el efecto de ambos tipos de partículas en un modelo de defecto óseo en calota de conejo.…”