S-layer protein-AuNP systems for the colorimetric detection of metal and metalloid ions in water

Abstract

Bacterial surface layer proteins (S-layer) possess unique binding properties for metal ions. By combining the binding capability of S-layer proteins with the optical properties of gold nanoparticles (AuNP), namely plasmonic resonance, a colorimetric detection system for metal and metalloid ions in water was developed. Eight Slayer proteins from different bacteria species were used for the functionalization of AuNP. The thus developed biohybrid systems, AuNP functionalized with S-layer proteins, were tested with different metal salt solutions, e.g. Indium(III)-chloride, Yttrium(III)-chloride or Nickel(II)-chloride, to determine their selective and sensitive binding to ionic analytes. All tested S-layer proteins displayed unique binding affinities for the different metal ions. For each S-layer and metal ion combination markedly different reaction patterns and differences in concentration range and absorption spectra were detected by UV/vis spectroscopy. In this way, the selective detection of tested metal ions was achieved by differentiated analysis of a colorimetric screening assay of these biohybrid systems. A highly selective and sensitive detection of yttrium ions down to a concentration of 1.67 × 10 −5 mol/l was achieved with S-layer protein SslA functionalized AuNP. The presented biohybrid systems can thus be used as a sensitive and fast sensor system for metal and metalloid ions in aqueous systems.

Controlled and Stable Patterning of Diverse Inorganic Nanocrystals on Crystalline Two-Dimensional Protein Arrays

“…Protein assemblies are promising scaffolds for the development of hierarchical nanomaterials as they can be engineered with angstrom precision and self-assemble into stable, complex architectures. ,− Covalent Au–thiol bonds have been successfully exploited to target AuNPs to Cys side chains, ,,, but the intrinsic reactivity and structure encoded within protein assemblies should allow for varied and orthogonal targeting strategies. , This richness of protein biochemistry has yet to be exploited to create materials with close and well-defined interactions between different classes of nanoparticles.…”