Diatoms: A Natural Source of Nanostructured Silica for Drug Delivery
Diatoms, single-celled photosynthetic algae, are a great source of intricate natural porous silica materials. The whole diatom cell is confined within a 3-dimensional ordered nanopatterned silica cell wall, called a frustule. The unique features of diatom frustules, such as their large specific surface area, biocompatibility and non-toxicity due to the silica composition, easily modifiable surface, high mechanical resistance, and thermal stability, make them suitable for drug delivery applications. Moreover, the easy cultivation of diatoms in an artificial environment, the huge availability of diatom frustules as fossil material (diatomite) in several areas of the world and its peculiar properties further confirm the advantages of using diatom porous silica as an alternative to synthetic materials for biomedical applications. In this chapter, the possible use of diatoms as microfrustules or reduced to nanoparticles as drug vectors is described. The processing of diatom frustules for drug delivery carrier preparation, biocompatibility tests, surface chemical modifications, cellular uptake and capability to transport therapeutic molecules inside cells is also discussed.