Dense tissue-like collagen matrices formed in cell-free conditions.

A new protocol was developed to produce dense organized collagen matrices hierarchically ordered on a large scale. It consists of a two stage process: (1) the organization of a collagen solution and (2) the stabilization of the organizations by a sol-gel transition that leads to the formation of collagen fibrils. This new protocol relies on the continuous injection of an acid-soluble collagen solution into glass microchambers. It leads to extended concentration gradients of collagen, ranging from 5 to 1000 mg/ml. The self-organization of collagen solutions into a wide array of spatial organizations was investigated. The final matrices obtained by this procedure varied in concentration, structure and density. Changes in the liquid state of the samples were followed by polarized light microscopy, and the final stabilized gel states obtained after fibrillogenesis were analyzed by both light and electron microscopy. Typical organizations extended homogeneously by up to three centimetres in one direction and several hundreds of micrometers in other directions. Fibrillogenesis of collagen solutions of high and low concentrations led to fibrils spatially arranged as has been described in bone and derm, respectively. Moreover, a relationship was revealed between the collagen concentration and the aggregation of and rotational angles between lateral fibrils. These results constitute a strong base from which to further develop highly enriched collagen matrices that could lead to substitutes that mimic connective tissues. The matrices thus obtained may also be good candidates for the study of the three-dimensional migration of cells.

New lipid nanocapsules exhibit sustained release properties for amiodarone.

Amiodarone is widely used in heart diseases but also provokes severe adverse effects due to its accumulation in other tissues than the heart. In order to circumvent side effects colloidal drug carriers have been designed to deliver the drug specifically to the site of action. Many preparation methods have been described and most have been reported to involve a high initial drug loss when introduced in an aqueous environment. Lipid nanocapsules (LNC) were prepared by a new phase inversion procedure and characterized in terms of size, surface potential, encapsulation efficiency, and drug release pattern. The encapsulation rate was varying between 92 and 94%. LNC did not display a distinct initial burst effect while the drug release of amiodarone can be prolonged over a significant period. Acceptor phase interfaces such as liposomes or blank LNC were applied to the release medium to enable a drug release to larger extents. The release was triggered by the pH of the release medium showing a faster release for lower pH; t(50%) values vary from 25.6 h (pH 2) to 236.3 h (pH 7.4). Moreover, LNC were prepared of different sizes (24.7+/-2.0 to 102.5+/-0.9 nm) showing only slight influences on their drug release profiles. It was concluded that the LNC surface is able to retain amphiphilic drugs. Such properties could allow drug delivery to the site of action without high initial drug loss.

Hyperstructures, genome analysis and I-cells.

New concepts may prove necessary to profit from the avalanche of sequence data on the genome, transcriptome, proteome and interactome and to relate this information to cell physiology. Here, we focus on the concept of large activity-based structures, or hyperstructures, in which a variety of types of molecules are brought together to perform a function. We review the evidence for the existence of hyperstructures responsible for the initiation of DNA replication, the sequestration of newly replicated origins of replication, cell division and for metabolism. The processes responsible for hyperstructure formation include changes in enzyme affinities due to metabolite-induction, lipid-protein affinities, elevated local concentrations of proteins and their binding sites on DNA and RNA, and transertion. Experimental techniques exist that can be used to study hyperstructures and we review some of the ones less familiar to biologists. Finally, we speculate on how a variety of in silico approaches involving cellular automata and multi-agent systems could be combined to develop new concepts in the form of an Integrated cell (I-cell) which would undergo selection for growth and survival in a world of artificial microbiology.