Spectrophotometric study of the interaction of active pharmaceutical ingredients with colloidal silver nanoparticles capped by sulfonato-calix[6]arene derivatives

Three sulfonato-calix[6]arene derivatives, namely para-sulfonato-calix[6]arene, calix[6]arene-O-propyl-3-sulphonate and para-sulfonato-calix[6]arene-O-propyl-3-sulphonate have been used as capping agents for silver nanoparticles. The sulfonato-calix[6]arene derivatives were demonstrated to stabilise the nanoparticles, and to act as ligands for molecular recognition at the surface of the nanoparticles. The nanoparticles were characterised by UV-visible spectroscopy, dynamic light scattering, zeta potential and scanning electron microscopy. The localised surface plasmon resonance of the nanoparticles was shown to be highly sensitive to the local environment, and was used to evaluate molecular interactions with four active pharmaceutical ingredients: streptomycin, gentamycin, D-penicillamine and chloramphenicol. Changes in spectral intensity and wavelength have shown that the interactions are dependent on both the nature of the active pharmaceutical ingredient and that of the calix[6]arene receptor.