Papers by Author: H.F. Hildebrand

Abstract: The advantages of local antibiotic administration - high local levels with low systemic toxicity - are nowadays recognized as an efficient way for anti-infection therapies consecutive to the orthopaedic implant surgery. Aimed at assessing the feasibility of using Hydroxyapatite as drugdelivery carrier in addition to its well-known bone reconstruction bioactivity, a pure HA ceramic with specific internal pore size and porosities was under our investigation. The antibiotic release and antibacterial effect were determined by UV spectrophotometry and disk agar diffusion assays after impregnation with different antibiotics and their release in different solvents. No differences were found after the ATB impregnation under normal pressure or under vacuum conditions. The influences of impregnation time on the duration of the ATB release and on the antibacterial efficiency were more evident for Vancomycin than for Ciprofloxacin and Gentamycin. In all cases, the ATBs penetrated micro-porous and meso-porous HA samples and showed significantly stronger and longer anti-bacterial effects than dense HA samples. The ATBs releases in PBS were relatively slower and the antibacterial effectiveness subsequently prolonged with respect to those in human plasma. All tested HA samples with or without ATB impregnation exhibited very good biocompatibility as shown by cell proliferation tests. It revealed a promising perspective for further improving the antibacterial efficiency by other surface functionalization methods for achieving a controllable drug delivery with antibiotic loaded HA.

Abstract: Calcium phosphate compounds, in particular HA and β-TCP, are the principal synthetic materials used for bone substitutes. To assess the feasibility for further grafting of drug delivery systems, a pure HA was elaborated with specific internal material porosities and then tested on its biological effectiveness. The cell viability tests with L132 cells confirmed the excellent cytocompatibility of HA and the graphite powder. MC3T3-E1 osteoblasts were grown on HA conditioned with culture medium and FCS for 2h. All HA samples produced a higher proliferation and vitality rates than the TCPS controls; the micro-porous HA inducing the highest cell growth near 150%. The macro/meso-porous HA is easily colonized by MC3T3-E1 osteoblasts As to the cell morphology, no significant differences are observed between control cells and those grown on the HA samples. Cytochemical staining of osteoblasts revealed a well developed cytoskeleton with strong stress fibres oriented in the cells in their longitudinal direction. Labelling of the focal adhesion contacts with anti-vinculin showed a less developed adhesion process in the cells on the different HA substrates, which may explain the above mentioned increase of proliferation.

Abstract: LASER Excimer irradiation can modify surface properties for biocompatibility improvement of a medical device. The PETs from 3 different origins were used in this study. The samples have been irradiated by excimer LASER with 10 different energies. The surface profile, the surface energy and the materials crystallinity have been assessed. Biological characterizations were made with human embryonic epithelial cells L132: proliferation, vitality, viability, adhesion with the p-NPP, and morphology. - The profile measurements allowed to establish the ablation threshold, which was 36 mJ/cm². The surface hydrophilic state increased reciprocally with the irradiation intensity. The gain is 13 %. The irradiated and non-irradiated product has identical cristallinity. PET was shown not to be toxic for L132 cells. Cell proliferation and cell vitality showed dose-dependant increases reciprocal to the irradiation energy (from 88 to 138% with respect to control). The correlation was highly significant (R² = 0,8). SEM micrographs show that the cells are better spread on the surface of irradiated PET than on untreated PET.

Abstract: PE is manufactured by Transysteme with the method of thermocompression of PE powder. This company irradiates PE by YAG LASER. We compared the physical behavior of both samples. The DSC reveals a high and similar crystallinity of PE, before and after YAG LASER treatment. Weattability between PE and Li-PE are similar at about 37 mJ/cm². The difference appears with respect to the surface profile and composition: the roughness is 0.20 µm for PE and 0.29µm for Li- PE. XPS reveals many traces of stripping agents on PE. YAG Laser produces a surface cleaning effect. Biological tests reveal a non-toxicity of the polyethylene powder, an improved proliferation and vitality of L132 cells on Li-PE with respect to untreated PE. We have a 4-fold improvement of proliferation and a 2-fold improvement of vitality on Li-PE with respect to PE. As to morphology and cell adhesion behavior, we have no differences between both samples. Thus the irradiation process of PE by YAG LASER improved the biological behaviors of this polymer due to changes in roughness and to surface cleaning.

Abstract: In order to improve the tissue integration and subsequently the long-term maintenance, the implant surface can be modified by mechanical, physical, chemical or biological functionalization. In this way, the surface becomes biologically active by further grafting of biomolecules. Two principal concepts are considered for materials functionalization. (i) The Drug Delivery Systems (DDS) where the bioactive molecules goes to the target. (ii) The grafting of the bioactive compounds on small strongly bound spacer molecules. In this system, the target goes to the bioactive molecules. These techniques provide promising outlooks for any polymeric or ceramic scaffold used in tissue engineering for the construction of whole artificial and functional organs.