Orange Carotenoid Protein in Mesoporous Silica: A New System towards the Development of Colorimetric and Fluorescent Sensors for pH and Temperature

Silvia Leccese; Andrea Calcinoni; Adjélé Wilson; Diana Kirilovsky; Donatella Carbonera; Thomas Onfroy; Claude Jolivalt; Alberto Mezzetti

doi:10.3390/mi14101871

Orange Carotenoid Protein in Mesoporous Silica: A New System towards the Development of Colorimetric and Fluorescent Sensors for pH and Temperature

Micromachines (Basel). 2023 Sep 29;14(10):1871. doi: 10.3390/mi14101871.

Authors

Silvia Leccese¹, Andrea Calcinoni^{1

2}, Adjélé Wilson³, Diana Kirilovsky³, Donatella Carbonera², Thomas Onfroy¹, Claude Jolivalt¹, Alberto Mezzetti¹

Affiliations

¹ Sorbonne Université, CNRS, Laboratoire de Réactivité de Surface (LRS), 4 Place Jussieu, 75005 Paris, France.
² Department of Chemical Sciences, University of Padova, 35131 Padova, Italy.
³ Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Saclay, CEDEX, 91198 Gif-sur-Yvette, France.

Abstract

Orange carotenoid protein (OCP) is a photochromic carotenoprotein involved in the photoprotection of cyanobacteria. It is activated by blue-green light to a red form OCP^R capable of dissipating the excess of energy of the cyanobacterial photosynthetic light-harvesting systems. Activation to OCP^R can also be achieved in the dark. In the present work, activation by pH changes of two different OCPs-containing echinenone or canthaxanthin as carotenoids-is investigated in different conditions. A particular emphasis is put on OCP encapsulated in SBA-15 mesoporous silica nanoparticles. It is known that in these hybrid systems, under appropriate conditions, OCP remains photoactive. Here, we show that when immobilised in SBA-15, the OCP visible spectrum is sensitive to pH changes, but such a colorimetric response is very different from the one observed for OCP in solution. In both cases (SBA-15 matrices and solutions), pH-induced colour changes are related either by orange-to-red OCP activation, or by carotenoid loss from the denatured protein. Of particular interest is the response of OCP in SBA-15 matrices, where a sudden change in the Vis absorption spectrum and in colour is observed for pH changing from 2 to 3 (in the case of canthaxanthin-binding OCP in SBA-15: λ_MAX shifts from 454 to 508 nm) and for pH changing from 3 to 4 (in the case of echinenone-binding OCP in SBA-15: λ_MAX shifts from 445 to 505 nm). The effect of temperature on OCP absorption spectrum and colour (in SBA-15 matrices) has also been investigated and found to be highly dependent on the properties of the used mesoporous silica matrix. Finally, we also show that simultaneous encapsulation in selected surface-functionalised SBA-15 nanoparticles of appropriate fluorophores makes it possible to develop OCP-based pH-sensitive fluorescent systems. This work therefore represents a proof of principle that OCP immobilised in mesoporous silica is a promising system in the development of colorimetric and fluorometric pH and temperature sensors.

Keywords: carotenoids; mesoporous silica nanoparticles; optical sensors.

Grants and funding

This research was funded by fellowships to S.L. (Doctoral School of Physics and Chemistry of Materials, Sorbonne Université, France, PhD fellowship) and A.C. (Erasmus+ program, European Union and DIM “Respore”, Île-de France region, France).