Chemical Decoration of Living Microalgae for Bioremediation

Many microorganisms produce specific protection structures, known as spores or cysts, exploited to increase their resistance to adverse environmental conditions. Scientists started to produce biomimetic materials inspired by these natural membranes, especially for industrial and biomedical applications.[1] Diatoms, for instance, are marine organisms able to uptake inorganic silicates from the ocean in order to build highly porous biosilica shells, called frustules, at mild environmental conditions. Diatoms shells, exploited for years for producing biohybrid materials for applications in photonics, optoelectronics and biomaterial science, can be chemically decorated via the common surface silanization reactions or the in vivo incorporation of functional organic molecules.[2] Our group has managed to obtain, via green processing, phosphorescent nanoparticles and fluorescent biosilica with specific optical features starting from simple feeding of diatoms with new synthesis fluorescent dyes [3-5]. We also produced 2D diatoms-based scaffolds for tissue engineering applications, after in vivo functionalization of living algae with pharmacological molecules like bisphosphonates, active towards osteogenic promotion and against osteo-resorption and bone degradation. [6-7] In this abstract we present biological data on the biocompatibility of a polydopamine-based artificial coating with diatom cells. Here living Thalassiosira weissflogii [8] cells were individually encapsulated with soft, artificial and easily functionalizable polydopamine layers with adhesive properties similar to feet proteins found in mussels. Polydopamine did not strongly interfere with diatom cells growth kinetics, and it can be exploited for entrapping detoxifying agents, like natural enzymes, and magnetic nanoparticles useful for living cells recovery after the decontamination process. These outcomes pave the way to the use of living diatom cells in the area of biomedicine, cellbased sensors and natural, and living devices for bioremediation. Polydopamine does not only confer certain sorption properties towards pollutants to surfaces [9], but it can encapsulate degrading functions, like catalytically active nanoparticles or enzymes, which bio-transform pollutants into small non toxic organic molecules.