Mécanismes de floculation de latex coeur-écorce par des copolymères cationiques

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Calcium Phosphate-Loaded Strips, Plugs and Putties: Physico-Chemical Properties for Osteopromotion and Ease of Surgery

The present study focuses on the physico-chemical and structural properties of composite scaffolds composed of biopolymer matrices (collagen or polysaccharide) loaded with calcium phosphate granules. A systematic three-dimensional analysis method was used to quantitatively characterize a series of plugs, strips and putties in terms of percentage of inorganic filler particles, size of the loaded granules, and spatial homogeneity of the calcium phosphate granules distribution. It appears clearly that each biomaterial currently available on the market offers specific properties. As a consequence, surgeons have to choose the medical device that best suits their needs depending on the clinical constraints but also should be aware of the mineral properties which remains key to bone reconstruction.</jats:p

Comparative Critical Study of Commercial Calcium Phosphate Bone Substitutes in Terms of Physic-Chemical Properties

Physico-chemical characteristics impact directly or indirectly the bioactive properties of biomaterials, it is then essential to correlate it with their effect in vivo. A panel of biomaterials available on the market, based on Hydroxyapatite (HA) and Tricalcium phosphate (β-TCP) is studied in terms of surface area, hydrophilicity, porosity, zeta potential, crystalline phases and density. This study highlights the dispersity of commercial calcium phosphates (CaP) properties, and demonstrates how the quality criteria required for such bone substitute based on biomimicry concept, whose pores distribution is certainly the more relevant, are often incompletely or not respected according to literature.</jats:p

Hollow Shells Development and Characterization for Cells Carrying Purpose

Bioceramics draw attention in bone tissue engineering field since their biomimetic properties regarding bone attribute. In this context, a concept of smart bioceramics granules made of Hydroxyapatite have been set up, enhancing surface area available to body fluids containing proteins and cell adhesion for bone forming respectively thanks to microporosities and macropore concavities. New “hollow shell” granules were developed and assessed by physico-chemical characterizations, in-vitro experiments and in-vivo implantation in comparison with classical round granules. This new original galenic formulation showed promising potential in cell carrying and osteoconduction matter.</jats:p

Composite Bioceramics/Polymer Electrospun Scaffolds for Regenerative Medicine

The main goal of this study was to succeed in the relevant association of well-known osteoconductive biphasic calcium phosphate (BCP) made of Hydroxyapatite (20% HA) and β-Tricalcium Phosphate (80% β-TCP) crystallographic phases and resorbable poly (L-lactide-co-D,L-lactide)(PLDLLA) 3D matrices synthesized by electrospinning. Two types of mineral particles were obtained, BCP new hollow granules, and classical BCP particles. It appeared that hollow shells/PLDLLA composite 3D matrices allowed higher cell adhesionin vitro,thanks to internal concavities and are promising scaffolds in terms of cell carrying.</jats:p

Photochemical dehydration of acetamide in a cryogenic matrix

International audienceVacuum ultraviolet (VUV) irradiation of acetamide has been monitored by Fourier transform infrared spectroscopy in argon matrix at 10 K. Several primary photoproducts, including HNCO : CH4 and CO : CH3NH2 molecular complexes, and acetimidic acid, which is reported for the first time, were characterized. The acetimidic acid identification was based on comparison between the experimental and theoretical (B3LYP) infrared spectra. Acetimidic acid is found in argon matrix in the (s-Z)-(E) and (s-Z)-(Z) configurations. It is also an intermediate in the VUV decomposition process, its dehydration leads to the formation of CH3CN : H2O molecular complex. The assignment of the complex was achieved by co-depositing the pairs of respective species and by ab initio calculation

Bioactivity of Biphasic Calcium Phosphate Granules, the Control of a Needle-Like Apatite Layer Formation for Further Medical Device Developments

International audienceBiphasic calcium phosphate (BCP) bioceramics (hydroxyapatite/tricalcium phosphate, or HA/TCP) for tissue engineering and drug delivery systems is a unique know-how. A mechanical mixture of HA and TCP does not lead to such bioactive ceramics. The wet elaboration conditions of calcium-deficient apatite (CDA) or CDHA, followed by sintering, converts it into TCP and HA. The dissolution precipitation of nano-sized needle-like crystals at the surface of BCP occurs on time at body temperature. Combining several technics of characterization [scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy (EDX), Brunauer-Emmett-Teller method (BET), chemical analysis, x-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR)], we demonstrated an evolution on time of the HA/β-TCP. The current paper describes the crystallographic evolution of initial β-TCP rhombohedral crystallographic structure to microsized needle-like layer corresponding to apatitic TCP form. This phenomenon leads to an increase of the HA/TCP ratio, since hexagonal apatitic TCP is similar to hexagonal HA. However, the Ca/P ratio (reflecting the chemical composition HA/TCP) remains unchanged. Thus, the high reactivity of BCP involves dynamic evolution from rhombohedral to hexagonal structure, but not a chemical change. The dynamic process is reversible by calcination. These events are absolutely necessary for smart scaffolds in bone regeneration and orthobiology

Preclinical and Clinical Cases of New Absorbable Composite Interference Screws in Osteoarticular Surgery

The objective of this study deals with preclinical and clinical cases of absorbable composite interference screws of next generation in osteoarticular surgery. These implants are made of resorbable polymers PLA either amorphous or semi-cristalline, associated with granules of microporous biphasic calcium phosphate ceramic. A preclinical study was performed on goats in femoral and tibial epiphysis during 4 and 6 months. Histological and histomorphometric results were obtained by micro CT, light and scanning electron microscopy. The comparative statistical in vivo study of the kinetics of resorption and bone regeneration have shown the superiority of the composite compared to control (polymer alone). Thus the presence of Biphasic Calcium Phosphate granules in the composite has a major role for bone regeneration at the expense of the implant (buffering effect and properties of osteoconduction). An observational and functional study involving 10 patients, with a follow-up from 17 to 33 months (mean 25.7), was performed. Data were analyzed according to Good Clinical Practice and International Conference on Harmonisation. Clinical observations have revealed no complications and no serious event was reported; quantitative functional indices confirm the good observational results. The clinical study supports the functionality and performance of this new composite with properties of osteoconduction related to the osteogenicity of microporous biphasic calcium phosphate granules in the field of knee ligament fixation.</jats:p