Tuning the Optical Properties of Au Nanoclusters by Designed Proteins

Abstract

but also by the ligands coordinated to them, as reported in recent studies. [2] In this sense, the coordination of metal-NCs with biomolecules is an emerging area of research since this biomolecular capping can endow multiple capabilities to the NCs, including biocompatibility, stability in biological media, and biological functionality (e.g., binding and inhibitory functions) resulting in hybrid bionanomaterials with a plethora of potential applications. [3] In this context, it has been shown that the capping and stabilization of metal NCs with peptides and proteins affect the optical properties of the NCs and the interaction with living matter by means of specific biological interplay. [4] Taking into account the role of the stabilizing agents on the NCs properties, an extra level of tailoring can be achieved by exploiting protein engineering. Metal coordinating engineered proteins are strongly inspired by natural metalloproteins, whose metalbinding capabilities allow to perform multiple functions, such as storage and transport, [5,6] sensing, [7,8] or catalysis. [9,10] In this framework, designed repeat proteins emerged as an interesting option to display custom metal coordination sites. Repeat proteins can be used as building blocks due to their modularity, regular geometry, and small size; allowing the design of both simple, but also more complex supramolecular assemblies and multifunctional systems. [11][12][13][14] The possibility of adding tailored chemical Gold nanoclusters (AuNCs) are nanomaterials with interesting photoluminescent properties that can be endowed with biomolecular recognition and biocompatibility when stabilized with proteins. The interplay between the optical features of AuNCs and the function added by the protein makes them perfect candidates for generating hybrid protein-inorganic nanomaterials. Focusing on protein stabilized-AuNCs, hitherto most of the work has covered the use of natural proteins for in situ growth of AuNCs. However, the exploitation of design proteins for such endeavors enables fine-tuning of the photoluminescent assets of AuNCs. In this work, rational protein engineering of modular protein scaffolds is applied for capping of non-emissive, non-passivated naked AuNCs, resulting in a fast and easy method for the synthesis of customizable and emissive protein-AuNC nanomaterials. Tuning of the photoluminescent properties of the final hybrid module is obtained by appropriate choice of the coordination residues grafted on the same protein scaffold. The effects of ligands and coordination bonds are studied using time-resolved photo luminescence and X-ray absorbance spectroscopies, shedding light on the mechanisms behind the emerging properties of these hybrid materials. Moreover, the described versatile strategy opens new avenues for the synthesis of on-demand photoluminescent hybrids for a wide spectrum of optical applications.

Engineered Protein-Driven Synthesis of Tunable Iron Oxide Nanoparticles as T1 and T2 Magnetic Resonance Imaging Contrast Agents

“…To unravel the influence of the metal-coordinating residues on the magnetic and physicochemical properties of the resulting Prot-IONP, the resulting nanomaterials were compared with the ones obtained using previously designed metal-binding proteins based on histidines (C8-24His) or cysteines (C8-24Cys), and a wild-type CTPR protein containing several residues that can bind iron ions (lysines and aspartic and glutamic acids) (C8-Wt) (Figures B and S1). − …”

“…In particular, here, we report the engineering of an iron-binding protein (Figure A), which was designed based on peptides rich in acidic residues from natural coordination systems. The templating of IONPs was comparatively studied using three other CTPR proteins (Figure B) previously described by our group. − The purpose of this study was not only to develop a reproducible and straightforward method for the production of IONPs stabilized by designed proteins (Prot-IONP) but also to evaluate the influence of the nature and size of the metal-coordination sites in the physicochemical properties of the resulting Prot-IONP complexes (e.g, oxidation state and relaxivity). Moreover, thanks to the modular properties of the CTPR module, the tunability of the size of the resulting IONPs was also evaluated using proteins with different sizes.…”

Engineering Coinage Metal Nanoclusters for Electroluminescent Light-Emitting Diodes

“…The high PLQYs of MNCs as the emissive layer is crucial to achieving an excellent performance for devices of superior electroluminescent LEDs based on MNCs. After years of continuous research, several effective strategies have been developed to obtain highly luminescent MNCs, including ligand engineering, surface motif engineering, heterometal doping, and structural modulation [ 46 , 47 , 48 ]. In this section, methods to synthesize highly luminescent MNCs will be discussed, focusing on the luminescence enhancement mechanism.…”

Bright Green Light-Emitting Gold Nanoclusters Confined in Insulin as Selective Fluorescent Switch Probes for Sensing and Imaging of Copper Ions and Glutathione

“…Actually, the metal precursor, protecting ligand, and size of metal nanoclusters could affect their luminescence properties and structure . Thus, tuning the emission could change the property and also its operation that arises from construction.…”

“…Actually, the metal precursor, protecting ligand, and size of metal nanoclusters could affect their luminescence properties and structure. 22 Thus, tuning the emission could change the property and also its operation that arises from construction. On the other hand, based on the accepted Jellium model, the red emissive Au-NCs have more atoms than green emissive Au-NCs.…”