Nanostructured polyelectrolyte multilayer drug delivery systems for bone metastasis prevention.

Polyelectrolyte multilayers (PEM) are well established nanoarchitectures with numerous potential applications, in particular as biomaterial coatings. They may exhibit specific biological properties in terms of controlled cell activation or local drug delivery. Here, in a new approach for bone metastasis prevention, we employed poly-l-lysine covalently grafted with beta-cyclodextrin as a polycationic vector (PLL-CD) for the antitumor bisphosphonate drug risedronate (RIS). Molar ratio for maximum loading of the PLL-CD vector with RIS was determined by Raman microspectroscopy. The efficacy of RIS at inhibiting cancer cell invasion in vitro was strongly enhanced upon complexation, whatever PLL-CD:RIS complexes were in solution or embedded into PEM nanoarchitectures. Complexes in solution also clearly prevented cancer-induced bone metastasis in animals. Incorporation of the complexes into PEM nanoarchitectures covering bone implants appears of interest for in situ prevention of bone metastasis after ablation.

Comparative phenotypic analysis of articular chondrocytes cultured within type I or type II collagen scaffolds.

Among the existing repair strategies for cartilage injury, tissue engineering approach using biomaterials and chondrocytes offers hope for treatments. In this context, collagen-based biomaterials are good candidates as scaffolds for chondrocytes in cell transplantation procedures. These scaffolds are provided under different forms (gel or crosslinked sponge) made with either type I collagen or type I or type II atelocollagen molecules. The present study was undertaken to investigate how bovine articular chondrocytes sense and respond to differences in the structure and organization of these collagen scaffolds, over a 12-day culture period. When chondrocytes were seeded in the collagen scaffolds maintained in free-floating conditions, cells contracted gels to 40-60% and sponges to 15% of their original diameter. Real-time polymerase chain reaction analysis indicated that the chondrocyte phenotype, assessed notably by the ratio of COL2A1/COL1A2 mRNA and alpha10/alpha11 integrin subunit mRNA, was comparatively better sustained in type I collagen sponges when seeded at high cell density, also in type I atelocollagen gels. Besides, proteoglycan accumulation in the different scaffolds, as assessed by measuring the sulfated glycosaminoglycan content, was found be highest in type I collagen sponges seeded at high cell density. In addition, gene expression of matrix metalloproteinase-13 increased dramatically (up to 90-fold) in chondrocytes cultured in the different gels, whereas it remained stable in the sponges. Our data taken together reveal that type I collagen sponges seeded at high cell density represent a suitable material for tissue engineering of cartilage.

Bovine chondrocyte behaviour in three-dimensional type I collagen gel in terms of gel contraction, proliferation and gene expression.

This study evaluated the in vitro behaviour of bovine chondrocytes seeded in collagen gels, promising recently reported scaffolds for the treatment of full-thickness cartilage defects. To determine how chondrocytes respond to a collagen gel environment, 2 x 10(6) chondrocytes isolated from fetal, calf and adult bovine cartilage were seeded within type I collagen gels and grown for 12 days in both attached and floating (detached from the culture dish after polymerisation) conditions. Monolayer cultures were performed in parallel. All chondrocytes contracted floating gels to 55% of the initial size, by day 12. Contraction was dependent on initial cell density and inhibited by the presence of dihydrocytochalasin B as previously observed with fibroblasts. Gene expression was determined using conventional and real-time PCR. The chondrocyte phenotype was better maintained in floating gels compared to attached gels and monolayers. This was demonstrated by comparing the ratio of COL2A1/ COL1A2 mRNA and also of alpha10/alpha11 integrin mRNA. A strong up-regulation of MMP13 expression was measured at day 12 in floating gels. The composition of cartilage-like tissue obtained by growing chondrocytes in a collagen gel varied depending on the floating or attached conditions and initial cell density. It is thus important to consider these parameters when using this culture system in order to prepare a well-defined implant for cartilage repair.