Potential sensing of cyanide anion using fluorescent lysozyme gold-aryl bioconjugates

Cyanide anion sensing using gold-aryl nanoparticles bioconjugated with lysozyme is reported. The chemical dissolution of lysozyme capped gold nanoparticles (Lys-AuNPs) in the presence and absence of aryl shell was studied in cyanide (CN⁻) solutions. It was found that gold nanoparticles functionalized with an aryl shell exhibited different dissolution and luminescence behavior compared to gold nanoparticles without an aryl shell. Here, we show the fluorescence enhancement upon the interaction of Lys-AuNPs-COOH with CN⁻ as a function of CN⁻ ion concentration as linear with an excellent correlation coefficient R² value of 0.9906 in the range from 1 × 10^–3 mM to 1.2 × 10^–2 mM. This study furthermore argues that the emission enhancement that occurs on gold dissolution is contributed from the complex from gold cyanidation rather than lysozyme. The emission intensity was enhanced accompanied with a blueshift upon CN⁻ reaction with the gold core which originated from [Au(CN)₂]⁻ and characterized by CN⁻ stretching frequency at 2175 cm⁻¹ and 2126 cm⁻¹ using Raman spectroscopy. Fluorescence lifetime decay analysis showed a shortened lysozyme lifetime upon nanoparticles formation and a significant increase after gold dissolution with KCN indicating emission enhancement.