Calcium carbonate Multifunctional Particles elaborated in supercritical CO2 medium. Application to controlled release of therapeutic proteins for tissue engineering – CALCOMED

Osteoporosis and degenerative arthropathies are in constant increase due to population ageing. The important sport practicing in modern societies leads also to articular traumatism with high prevalency. Thus, research in tissue engineering becomes one major axis at the international level. This kind of research trends to answer several important questions involving scientific, economical and societal aspects and implies the respect of new regulations in constant evolution. Solutions can be provided by recent advances in micro-nanomaterials and must combine skills acquired by physicists, chemists, and biologists. Our consortium is now able to achieve a multidisplinary approach to conceive intelligent biomaterials including therapeutic proteins issued from biotechnologies for tissue engineering of bone and cartilage. Even if biomaterials offer promising clinical solutions to reduce the surgery acts amount, clinician needs remain obvious because the developed systems do not yet entirely answer to the work specifications. Especially, their mechanical resistance and efficiency to regenerate the tissues must be improved. The objectives of our project are to combine already existing implantable synthetic extracellular matrixes with new drug delivery systems encapsulating growth factors. We plan to formulate calcium carbonate multifunctional particles (CMP), using an original process based on the use of carbon dioxide in supercritical conditions. CMP formulation, patented by INSERM, allows to design micro-nanoparticles with controlled size. It is based on the formation of a water in CO2 emulsion where aqueous droplets act as micro-nanoractors in which protein concentration can be precisely adjusted The protein is encapsulated during the process that permits to obtain high encapsulation yields (>70%) validated on lysozyme and insulin with maintained integrity and activity in vitro. The particles can also be functionalized with molecules such as bisphophonates known for their high affinity to mineral surfaces. Thus, we expect to modulate surface properties and solubility of CMP. Besides, these new functionalities open routes to chelate compounds having therapeutic or diagnostic properties (contrast agent for MRI or radionuclides). CMP technology will allow the encapsulation of growth factors (VEGF, TGF beta) for which preformulation is already validated by some implicated partners. Throughout the program, a systematic physico-chemical study in pressurized medium will permit to better understand the fundamentals of CMP formation. The impact of the particles on the mechanical properties of Calcium-Phosphate cements and biocompatible polymer-based hydrogels and their ability to release in a controlled way the active protein will be assessed. We aim to achieve an efficient recruitment of cells implicated in the process of bone and cartilage repairing. The last step of the study will validate a proof of concept in vivo on a rabbit model.