A Bioinspired Polymer as Versatile Platform for the Design of Living Diatom Microrobots

Bio-based functional materials have attracted great interest due to their sustainability and versatility. The combination of extracellular, tailored matrices and living organisms (or their isolated components) has yielded functional materials with remarkable properties, and with use in a variety of applications, from sensing to catalysis [1]. Bio-inspired and biomimetic polymers hold great promise due to their chemical diversity and tuneability. Polydopamine (PDA) is a biocompatible and bio-inspired polymer, that can be easily synthetized via spontaneous oxidative polymerization of dopamine in water. Even though the structure of PDA has not been yet fully described, it exhibits interesting features like adhesive and entrapping properties and tuneable porosity [2]. PDA has been used in combination with living microorganisms, yielding biohybrids with enhanced capabilities, such as electrically conductive bacteria bioelectrodes [3], and highly resistant yeast pseudo-spores [4]. However, the coating of shelled microorganisms like diatoms, which bear biosilica exoskeletons, can afford more robust and stable biohybrids. By using their nanostructured shells as templates, a more homogeneous coating of PDA can be achieved, that can be even transmitted to a number of further generations [5]. The presence of specific chemical groups in PDA, like charged groups and aromatic rings, allows it to interact and trap specific compounds, such as polyaromatic or polychlorinated hydrocarbons [6]. This work aims to optimize the fabrication of a biocompatible PDA-based coating onto living diatoms, explore the decoration with additional functional elements (nanoparticles, enzymes, etc), and test their performance as biohybrid functional materials. The viability of diatom biohybrids coated with PDA has been evaluated through standardized tests; magnetic nanoparticles and oxidative enzymes have been incorporated into the PDA matrix (with the subsequent physico-chemical characterization); and their catalytic activity has been tested under repetitive tests of recycle and in long-term experiments, with promising results. We have designed a methodology that allows to generate PDA-embedded living diatoms with the ability to bear a heterogeneous mixture of functional elements. These biohybrid microrobots have potential applications in bioremediation and biomedicine.<br/><br/>[1] Ariga, K., “Biomimetic and Biological Nanoarchitectonics”, Int. J. Mol. Sci., 23(7), 3577 (2022).<br/>[2] Lo Presti, M., Rizzo, G., Farinola, G. M., Omenetto, F. G., “Bioinspired Biomaterial Composite for All-Water-Based High-Performance Adhesives”, Adv. Sci., 8, 2004786 (2021).<br/>[3] Labarile, R., Vona, D., Varsalona, M., Grattieri, M., Reggente, M., Comparelli, R., Farinola, G. M., Fischer, F., Boghossian, A. A., Trotta, M., “In vivo polydopamine coating of Rhodobacter sphaeroides for enhanced electron transfer”, Nano Res., 17(2), 875-881 (2024).<br/>[4] Yang, S. H., Kang, S. M., Lee, K. B., Chung, T. D., Lee, H.,Choi, I. S., “Mussel-inspired encapsulation and functionalization of individual yeast cells”, J. Am. Chem. Soc., 133(9), 2795–2797 (2011).<br/>[5] Vona, D., Cicco, S. R., Ragni, R., Vicente-Garcia, C., Leone, G., Giangregorio, M. M., Palumbo, F., Altamura, E., Farinola, G. M., “Polydopamine coating of living diatom microalgae”, Photochem. & Photobiol. Sci., 21, 949-958 (2022).<br/>[6] Vicente-Garcia, C., Losacco, V., Vona, D., Cicco, S. R., Altamura, E., Farinola, G. M., Ragni, R., "Straightforward and effective removal of phenolic compounds from water by Polydopamine coated Diatomaceous Earth," 2021 International Workshop on Metrology for the Sea; Learning to Measure Sea Health Parameters (MetroSea), Reggio Calabria, Italy, 27-31 (2021).