Micropatterning of bioactive self-assembling gels.

Microscale topographical features have been known to affect cell behavior. An important target in this area is to integrate top down techniques with bottom up self-assembly to create three-dimensional (3D) patterned bioactive mimics of extracellular matrices. We report a novel approach toward this goal and demonstrate its use to study the behavior of human mesenchymal stem cells (hMSCs).

Self-assembly of large and small molecules into hierarchically ordered sacs and membranes.

We report here the self-assembly of macroscopic sacs and membranes at the interface between two aqueous solutions, one containing a megadalton polymer and the other, small self-assembling molecules bearing opposite charge. The resulting structures have a highly ordered architecture in which nanofiber bundles align and reorient by nearly 90 degrees as the membrane grows. The formation of a diffusion barrier upon contact between the two liquids prevents their chaotic mixing.

Plasmid size influences chitosan nanoparticle mediated gene transfer to chondrocytes.

The objective of the present study was to prepare chitosan nanoparticles incorporating a relatively large plasmid encoding for osteogenic protein (OP)-1 and to determine the ability of these nanoparticles to transfect adult canine articular chondrocytes in vitro. The positive charge of chitosan acted to condense the relatively large negatively-charged OP-1 plasmid such that it could be incorporated into nanoparticles. Incorporation of the plasmid into the chitosan nanoparticles did not affect the structural integrity of the plasmid as demonstrated by gel electrophoresis.

Delivery of plasmid IGF-1 to chondrocytes via cationized gelatin nanoparticles.

The objective of the present study was to investigate the use of gelatin and cationized-gelatin nanoparticles for the nonviral delivery of the plasmid DNA encoding for insulin-like growth factor (IGF)-1 to adult canine articular chondrocytes in vitro; plasmid for enhanced green fluorescence protein (EGFP) was used as a marker gene. The spherical cationized gelatin nanoparticles were on average 172 nm in diameter, compared with the often ellipsoid-shaped unmodified (noncationized) gelatin particles that generally appeared to be 10 mum to greater than 20 mum in length. The zeta potential of the positively charged cationized gelatin nanoparticles containing the plasmid was around 20 mV compared with about 2 mV for the unmodified gelatin particles.

Genetically enhanced engineering of meniscus tissue using ex vivo delivery of transforming growth factor-beta 1 complementary deoxyribonucleic acid.

To investigate the use of a scaffold seeded with genetically modified meniscal cells or mesenchymal stem cells (MSCs) for the healing of meniscal lesions, primary meniscus cells and bone marrow-derived MSCs were isolated from bovine calves and transduced with first-generation adenoviral vectors encoding green fluorescent protein, luciferase, or transforming growth factor (TGF)-beta1 complementary deoxyribonucleic acid (cDNA). The genetically modified cells were seeded in type I collagen-glycosaminoglycan (GAG) matrices and transplanted into tears of the avascular zone of bovine menisci. After 3 weeks of in vitro culture, constructs and repair tissues were analyzed histologically, biochemically, and using reverse transcriptase polymerase chain reaction.