HydrophobinVmh2 is a small amphiphilic protein, which self-assembles on different surfaces and naturally interacts with glucose. Here, we report on the synthesis of a nanobiocomplex made of polyethylene glycol, Vmh2 and gold nanoparticles by a one-step process and on its ability to recognise glucose in an aqueous solution at 0.3–0.6–1.2 mg ml⁻¹ concentrations. Even though the Vmh2 proteins are intrinsically bonded to the gold core, effective glucose interaction monitoring was demonstrated by using dynamic light scattering, ultraviolet–visible, polarization-modulated infrared reflection–absorption and x-ray photoelectron spectroscopies. Experimental results highlighted an affinity constant of 7.3 ± 0.3 mg ml⁻¹ between the nanobiosystem and the sugar, and a detection sensitivity of 0.13 ± 0.06 a.u./mg ml⁻¹.

The thermophilic bacterium Thermus thermophilus HB27 encodes chromosomal arsenate reductase (TtArsC), the enzyme responsible for resistance to the harmful effects of arsenic. We report on adsorption of TtArsC onto gold nanoparticles for naked-eye monitoring of biomolecular interaction between the enzyme and arsenic species. Synthesis of hybrid biological–metallic nanoparticles has been characterized by transmission electron microscopy (TEM), ultraviolet-visible (UV–vis), dynamic light scattering (DLS) and phase modulated infrared reflection absorption (PM-IRRAS) spectroscopies. Molecular interactions have been monitored by UV–vis and Fourier transform-surface plasmon resonance (FT-SPR). Due to the nanoparticles’ aggregation on exposure to metal salts, pentavalent and trivalent arsenic solutions can be clearly distinguished by naked-eye assay, even at 85 μM concentration. Moreover, the assay shows partial selectivity against other heavy metals.