Algae-silica systems as functional hybrid materials

Microalgal cells were entrapped within two different sol-gel silica matrices with the aim of carrying out viability studies and developing active phases for sensor development. The first sol-gel system, based on methacryloxypropyltrimethoxysilane (MAPTS) and tetramethoxysilane (TMOS) monomers, was able to entrap lyophilized Chlorella vulgaris and Anabaena sp. PCC7120, but its rather non-porous nature limited the algal viability to the surface and fractures of the resulting hybrid material. However, this sol-gel material prepared with Chlorella tissue successfully performed as an active phase in the development of sensors for heavy-metal ions (e.g. Pb²⁺, Cu²⁺ and Cd²⁺) in water solution. The second sol-gel system was obtained using methyltrimethoxysilane (MTMOS), phenyltrimethoxysilane (PhTMOS) and TMOS monomers. Here, entrapped algae appeared to weakly interact with the resulting matrix probably due to its high hydrophobicity and also very low porosity. In this context, SEM and AFM studies carried out with the Anabaena-sol-gel material showed that algae could be removed from the polymeric network leaving traces having the algae's peculiar three-dimensional shape. This opens the way to prepare imprinted materials using a soft lithographic approach, which could be potentially used as artificial receptors for electrochemical sensing of algae target species.