Gaël Grimandi

A new injectable bone substitute combining poly(ε-caprolactone) microparticles with biphasic calcium phosphate granules

Previous studies have shown the e!ectiveness of an injectable bone substitute (IBS) composed of biphasic calcium phosphate in 2% hydroxypropyl methylcellulose gel (50/50 w/w). A therapeutic agent in the form of a drug can be added to the biomaterial by encapsulation into microparticles to protect the active agent, control its release and preserve the material rheological properties. Poly(-caprolactone) was used in this study because of its biocompatibility and resorbability, as tested in orthopaedic implants and surgical sutures. Particles (80}200m) were manufactured by a solvent evaporation}extraction process (1g of polymer, 11 } 15m l methylene chloride, with a stirring speed of 400}600 rpm) and introduced into the IBS in a 5}50% (V/V) range. Injectability was evaluated by texture analysis. With less than 45% of particles, the material had rheological properties similar to those of the reference IBS, whereas injectability decreased markedly with more than 45% of particles. A preliminary in vitro release study showed that this type of triphasic IBS could be e

From osteoarthritis treatments to future regenerative therapies for cartilage

cient for drug delivery systems with osteoconduction properties. 2001Published by Elsevier Science Ltd.

Vancomycin encapsulation in biodegradable poly(ε-caprolactone) microparticles for bone implantation. Influence of the formulation process on size, drug loading, in vitro release and cytocompatibility

Osteoarthritis (OA) is associated with cartilage degeneration and an accompanying inflammatory syndrome of the synovium in addition to alteration of the subchondral bone. The molecular and cellular events involved in OA have only partially been elucidated. This review provides a global view of the physiopathology of OA, as well as non-pharmacological and pharmacological treatments for the disorder. An update on surgical treatments and their indications is given with an orientation towards the management of OA and cartilage repair by cell-based regenerative therapies. These promising biological technologies will, potentially, play a major role in the treatment of cartilage-associated diseases.

Apatite as carrier for growth hormone: in vitro characterization of loading and release.

Vancomycin encapsulation in biodegradable poly(epsilon-caprolactone) microparticles (200 microm mean diameter) was most efficient with a simple emulsion technique that dispersed 122.5 mg/g of polymer. Scanning electron micrographs showed smooth or pitted particles. Dissolution studies were correlated with microparticle morphology, indicating higher release with pitted particles when vancomycin was encapsulated in a dissolved state. The cytocompatibility of these poly(epsilon-caprolactone) microparticles was demonstrated by a direct contact cytotoxic assay. This material can be considered as an efficient drug delivery system for bone implantation.

Injectable Bone Substitute using a hydrophilic polymer

Previous studies concerning bone drug delivery systems have provided little data about the amount of drug loaded, one of the essential factors for determining the dose/effect relationship. To investigate this factor, an adsorption method involving a therapeutic agent was tested in vitro on an apatitic calcium phosphate (AP). One milligram of human growth hormone (hGH) was deposited onto 0.1, 0.15, and 0.2 g of AP powder over a period of 24 h at 37 degrees C. The amount of hGH loaded was determined by subtracting the dose recovered from that applied on AP. The results show that 1 g of AP absorbed 9.48 mg of hGH. From 0.1 and 0.15 g of hGH-loaded AP, hGH was released in vitro for 2 and 3 weeks, respectively, with a 50% time release (T1/2) at 30 h and 72 h, respectively, for the two quantities. The amount of drug loaded and the determined release kinetics were compatible with the action pattern of hGH, indicating that hGH-loaded calcium phosphate supports are suitable for bone-growth promotion.

Identification of phenotypic discriminating markers for intervertebral disc cells and articular chondrocytes

We studied a new injectable biomaterial for bone and dental surgery consisting of a hydrophilic polymer as matrix and bioactive calcium phosphate (CaP) ceramics as fillers. This material is composed of complex fluids whose flow is determined by the laws of rheology. We investigated the macromolecular effects on this composite in a tube. The stability of the polymer and the mixture is essential to the production of a ready-to-use injectable biomaterial. These flow properties are necessary to obtain CaP bioactivity in a dental canal or bone defect during percutaneous surgery. Macromolecules provide spaces between CaP ceramic granules and facilitate the role of the biological agents of bone substitution.

In vitro influence of apatite-granule-specific area on human growth hormone loading and release

OBJECTIVE The present study was conducted to improve our knowledge of intervertebral disc (IVD) cell biology by comparing the phenotype of nucleus pulposus (NP) and annulus fibrosus (AF) cells with that of articular chondrocytes (ACs). METHODS Rabbit cells from NP and AF were isolated and their phenotype was compared with that of AC by real-time PCR analysis of type I (COL1A1), II (COL2A1) and V (COL5A1) collagens, aggrecan transcript (AGC1), matrix Gla protein (MGP) and Htra serine peptidase 1 (Htra1). RESULTS Transcript analysis indicated that despite certain similarities, IVD cells exhibit distinct COL2A1/COL1A1 and COL2A1/AGC1 ratios as compared with AC. The expression pattern of COL5A1, MGP and Htra1 makes it possible to define a phenotypic signature for NP and AF cells. CONCLUSIONS Our study shows that NP and AF cells exhibit a clearly distinguishable phenotype from that of AC. Type V collagen, MGP and HtrA1 could greatly help to discriminate among NP, AF and AC cells.

Dynamic compaction: a new process to compact therapeutic agent-loaded calcium phosphates.

Although calcium phosphate biomaterials often are used as drug delivery systems (DDS) at bone sites, the conditions affecting the loading of the therapeutic agent (TA) have not been well documented. A human growth hormone (hGH) adsorption method was used in this study to investigate the influence of the formulated apatite (AP)-specific area on loading and release. AP powders were formulated with a 200-500 microm granulometry and various specific areas. Two milligrams of hGH in solution were deposited for 24 h at 37 degrees C on 100 mg of AP with different specific areas. The amount of hGH loaded was determined by immunoradiometric assay (IRMA) and eluted stain bioassay (ESTA) using Nb2 lymphoma rat cells. Although loading was not greatly influenced by a specific area between 3 and 25 m2/g, dependency was noted for higher specific areas. Human GH release was measured by IRMA and ESTA over a 33-day period, with half-time release between 25 and 79 h. Comparison of IRMA and ESTA measurements for the hGH amounts loaded showed that hGH biologic activity was conserved. Results indicate that it is feasible to control the quantity of TA loading on AP by modifying specific areas for in vivo applications.

Assay of in vitro osteoclast activity on dentine, and synthetic calcium phosphate bone substitutes

The sintering stage in the classical process of preparing bone substitution materials prevents therapeutic agents from being loaded into calcium phosphate powder. However, dynamic compaction, a new process, requires no external heat, allowing the therapeutic agent to be incorporated into ceramics. This report presents the results of an in vitro study of therapeutic agents associated with calcium phosphate powder and involving this new process. A mixture of vancomycin lyophilized powder (0.15 g) and biphasic calcium phosphate (BCP) powder (1.85 g) was compacted. In addition, 2 ml of human growth hormone (1 mg ml-1) were associated with BCP powder by physical adsorption on bead surfaces before compaction. Detection by monoclonal antibodies and sodium dodecyl sulphate polyacrylamide gel electrophoresis demonstrated the structural integrity of the two therapeutic agents after consolidation. This new compaction process should be useful in developing ceramics that contain a therapeutic agent.

Effect of Sintering Process of HA/TCP Bioceramics on Microstructure, Dissolution, Cell Proliferation and Bone Ingrowth

Resorption of synthetic bone substitute materials is essential for the integration of these materials into the natural bone remodeling process. Osteoclast behavior in the presence of calcium phosphate bioceramics (CaPB) is partially understood, and a better understanding of the underlying mechanisms is expected to facilitate the development of new synthetic bone substitutes to improve bone regeneration. In the present study, our aim was to investigate osteoclastic resorption of various synthetic CaPB. We used neonatal total rabbit bone cells to generate osteoclasts. Osteoclast-generated resorption on dentine and multiple CaPB was investigated by quantifying the surface resorbed and measuring tartrate resistant acid phosphatase (TRAP) enzyme activity. In this study, we observed that osteoclastic cells responded in a different way to each substrate. Both dentine and CaPB were resorbed but the quantitative results for the surface resorbed and TRAP activity showed a specific response to each substrate and that increased mineral density seemed to inhibit osteoclast activity.