Fe(III)-MimochromeVI*a as a catalyst for the development of functional nanomaterials

The synergic integration between nanotechnology and biocatalysis grants with the possibility of engineering functional nanomaterials with interesting application in industrial and biotechnological fields. In this area, gold nanomaterials (AuNMs) provide a high enzyme loading, due to the large surface area-to-volume ratio, possess a versatile surface chemistry as well as tunable sizes and shapes. Anisotropic AuNMs, such as nanorods (AuNRs), are characterized by a plasmon-related optical response, dependent upon their aspect ratio, which is an intriguing feature in building optical devices and biosensors [1]. In this context, the conjugation of AuNMs with artificial miniaturized heme-proteins, known as Mimochromes (MCs), enables the construction of versatile nanomaterials. Indeed, recent studies on Fe(III)-MCs proved the successful anchoring of these artificial biocatalysts on gold nanosurfaces, such as nanoparticles, while retaining structural properties and catalytic potential [2]. Herein we report the behaviour of the synthetic mini-peroxidase Fe(III)- MimochromeVI*a (FeMC6*a) when conjugated to AuNRs, by focusing on the relationship between the gold nanomaterial shape and the enzyme structural/functional properties. The covalent attachment of FeMC6*a on AuNRs was carried out by click chemistry, using the strain-promoted azide-alkyne cycloaddition (SPAAC, Figure 1). The prepared nanoconjugate was thoroughly characterized by means of several analytical techniques (such as UV-Vis-NIR spectroscopy, transmission electron microscopy and circular dichroism). The catalytic properties of the resulting nanomaterial were evaluated using model oxidation reactions, which revealed that FeMC6*a-(PEG)4@AuNRs is catalytically active. All the results demonstrate that the artificial metalloprotein FeMC6*a can be firmly anchored on AuNRs, thus offering new opportunities for the development of innovative materials with applications in biosensing and biocatalysis. [1] L. Yang, Z. Zhou, J. Song, and X. Chen, Chem Soc Rev 48 (2019) 5140-76. [2] G. Zambrano, M. Chino, E. Renzi, R. Di Girolamo, O. Maglio, V. Pavone, A. Lombardi, and F. Nastri, Biotechnol. Appl. Biochem. 67 (2020) 549-62.