A biophotoelectrode based on boronic acid-modified Chlorella vulgaris cells integrated within a redox polymer

Green microalgae are gaining attention in the renewable energy field due to their ability to convert light into energy in biophotovoltaic (BPV) cells. The poor exogenous electron transfer kinetics of such microorganisms requires the use of redox mediators to improve the performance of related biodevices. Redox polymers are advantageous in the development of subcellular-based BPV devices by providing an improved electron transfer while simultaneously serving as immobilization matrix. However, these surface-confined redox mediators have been rarely used in microorganism-based BPVs. Since electron transfer relies on the proximity between cells and the redox centres at the polymer matrix, the development of molecularly tailored surfaces is of great significance to fabricate more efficient BPV cells. We propose a bioanode integrating Chlorella vulgaris embedded in an Os complex-modified redox polymer. Chlorella vulgaris cells are functionalized with 3-aminophenylboronic acid that exhibits high affinity to saccharides in the cell wall as a basis for an improved integration with the redox polymer. Maximum photocurrents of (5 ± 1) µA cm−2 are achieved. The developed bioanode is further coupled to a bilirubin oxidase-based biocathode for a proof-of-concept BPV cell. The obtained results encourage the optimization of electron-transfer pathways toward the development of advanced microalgae-based biophotovoltaic devices.Z. Herrero-Medina acknowledges the support by a Marti Franqu`es scholarship of the Department of Chemical Engineering of the URV (Ref: 2018PMF-PIPF-27) and thanks Julio C. Zuaznabar-Gardona (now at CreatSens Health S.L.) for inspiring discussions. Part of this work was funded by a collaboration project between URV and King Abdulaziz University (contract number: TT16008). P. Wang is grateful for the financial support by the China Scholarship Council (CSC). A. Lielpetere is part of a project that has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement N◦813006 (Implantsens)