Golden Twists: pH-tuned chirality at the nanoscale for advanced nano-sensing

Abstract

Chiral gold nanoparticles (AuNPs) have emerged as versatile tools for biosensing because they can selectively interact with chiral biomolecules and convert these interactions into optical signals. Recently, we functionalized AuNPs with L- and D-cysteine, obtaining chiral AuNPs with long-term stability and pronounced optical activity. In this work, we further examine their applicability by evaluating the robustness of these colloidal solutions under conditions relevant to biosensing applications. In particular, their colloidal and optical stability were evaluated as a function of pH (pH=3, 7, 9) and temperature (25 °C and 37 °C). UV–visible spectroscopy indicates that the localized surface plasmon resonance remains essentially unaltered under all tested conditions, while revealing pH-modulated surface-related electronic features. Dynamic light scattering and ζ-potential measurements assessed colloidal stability over the entire pH and temperature range tested, up to 2 weeks. These results demonstrate the suitability of L- and D-cysteine–functionalized chiral AuNPs as stable and reliable biosensing platforms, and support their use in physiological environments and for further biofunctionalization strategies.