Immobilization of Orange Carotenoid Protein on mesoporous silica SBA-15 for the development of photoactivable nanodevices

Abstract

The photoactive Orange Carotenoid Protein (OCP) is a protein involved in photo-protective responses in cyanobacteria. It induces the thermal dissipation of excess solar energy counteracting oxidative stress and photodamage. OCP consists of two structural domains sharing a non-covalently linked carotenoid as a cofactor. Blue light induces photoactivation of OCP and its colour changes from orange to red. In this work we have immobilized OCP on different kinds of raw and surface-functionalized SBA-15 mesoporous silica nanoparticles and structurally characterized the systems. SBA-15 matrices have demonstrated to be suitable supports for OCP, whose immobilization is strongly enhanced by the pre-photoactivation of the protein. OCP remains photoactive inside the mesoporous silica matrix, thereby producing photochromic nanoparticles. Under appropriate conditions OCP can also be released from SBA-15 nanoparticles. This work is a first step to understand the influence of matrix constraints and confinement on OCP photocycle. Furthermore, this study demonstrates that the OCP@SBA-15 system can be used as a photochromic material and as a possible optical device for nanoscale applications. Finally, this work is a first step towards the development of caroteno-protein and carotenoid release-strategies from silica matrix to be applied in the field of antioxidant drug delivery. • Orange Carotenoid Protein was efficiently adsorbed on SBA-15 up to 93 mg/g of solid material. • Orange Carotenoid Protein remains photoactive when immobilized. • Orange Carotenoid Protein immobilization was more efficient on SBA-15 functionalized with amino groups. • Orange Carotenoid Protein adsorption on SBA-15 was partially reversible upon change of pH and ionic strength. • The amount of immobilized Orange Carotenoid Protein was enhanced when the adsorption process takes place upon illumination.