Previous studies performed using polysaccharide-based matrices supplemented with hydroxyapatite (HA) particles showed their ability to form in subcutaneous and intramuscular sites a mineralized and osteoid tissue. Our objectives are to optimize the HA content in the matrix and to test the combination of HA with strontium (Sr-HA) to increase the matrix bioactivity. First, non-doped Sr-HA powders were combined to the matrix at three different ratios and were implanted subcutaneously for 2 and 4 weeks. Interestingly, matrices showed radiolucent properties before implantation. Quantitative analysis of micro-CT data evidenced a significant increase of mineralized tissue formed ectopically with time of implantation and allowed us to select the best ratio of HA to polysaccharides of 30% (w/w). Then, two Sr-substitution of 8% and 50% were incorporated in the HA powders (8Sr-HA and 50Sr-HA). Both Sr-HA were chemically characterized and dispersed in matrices. In vitro studies performed with human mesenchymal stem cells (MSCs) demonstrated the absence of cytotoxicity of the Sr-doped matrices whatever the amount of incorporated Sr. They also supported osteoblastic differentiation and activated the expression of one late osteoblastic marker involved in the mineralization process i.e. osteopontin. In vivo, subcutaneous implantation of these Sr-doped matrices induced osteoid tissue and blood vessels formation.

Bovine milk hydrophobic fraction of proteose-peptone was prepared by hydrophobic interaction fast protein liquid chromatography. This method has several advantages such as high rapidity, simple good reproducibility and less denaturation. The proteose-peptone was eluted from a TSK-Phenyl-5PW column with a 1 M-0 M ionic strength gradient of NaH 2 PO 4 , pH 6-8, using a 6 ml/min flow rate for 56 min. The quantity of protein injected was 62-5 mg; however, it could be increased up to 100 mg. The elution order was /J-CN-4P

Summary -The industrial strain Bifidobacterium animalis was used as assay organism to evaluate bifidobacterial growth-promoting activity of bovine milk proteose-peptone. This proved to be a better growth-promoting factor than bovine casein. The bifidogenic activity was found mainly in the proteose-peptone hydrophobie fraction containing component 3, although the glycan moiety was a weak growth-promoter. Proteose-peptone digests by various proteolytic enzymes caused great enhancement of B animalis growth, particularly the Pronase digest. Size-exclusion chromatography of digests showed that the more active peptides had a molecular mass distribution of 1000 to 5000 Da.

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