This review is devoted to the most recent developments (2000–2005) of sol–gel materials at the interface with biology. In the context of bioencapsulation in mineral hosts, novel synthetic approaches have been designed, allowing the immobilization of numerous proteins, enzymes and immune molecules as well as poly-saccharides, phospholipids and nucleic acids. These efforts have led to the development of new biosensors and bioreactors. A similar trend was also observed for whole cell encapsulation, survival periods over several weeks now being achieved. This has opened the possibility of designing hybrid hosts for cell-based biosensing and bioproduction, ultimately allowing the development of artificial organs. Indeed, applications of sol–gel processes are not restricted to bioencapsulation, as demonstrated by recent progress in drug release systems and bioactive materials. Finally, the considerable efforts devoted to the biomimetic elaboration of mineral structures suggest that they might be the key for future development of improved sol–gel materials for bio-applications.

Common Anabaena, Calothrix, and Leptolyngbya cyanobacteria are shown to form Au, Ag, Pd, and Pt nanoparticles of well-controlled size. These nanoparticles are synthesized intra-cellularly, and naturally released in the culture medium, where they are stabilized by algal polysaccharides, allowing their easy recovery. The size of the recovered particles as well as the reaction yield is shown to depend on the cyanobacteria genus. Investigations of nanoparticle formation indicate that the intracellular nitrogenase enzyme is responsible for the metal reduction but that the cellular environment is involved in the colloid growth process.