Method for Detection of Thiol-containing Amino Acids Using Gold-Polystyrene Composites

This paper reports the preparation of PS-PEI-Au composite colloids via the utilization of a facile method involving poly(ethylenimine) (PEI). The PEI used in the reaction scheme served the role of a linker between Au and PS and additionally as a reducing agent in the conversion of Au ions to Au NPs. The PS-PEI-Au colloids thus prepared were characterized by scanning electron microscopy, UV-Vis and IR spectroscopy and cyclic voltammetry. The PS-PEI-Au composites were further used for the detection of the thiol-containing amino acids, cysteine and homocysteine, via Attenuated Total Reflection (ATR) spectroscopy. Experimental results revealed interfacial binding of the amino acids to the composites, and correlated with successive additions of the respective amino acids.