Determination of lysozyme at the nanogram level by a resonance light-scattering technique with functionalized CdTe nanoparticles.

Nanoparticles of cadmium telluride coated with mercaptoacetic acid were prepared in the water phase. Further, an assay of lysozyme with a sensitivity at the nanogram level is proposed. At pH 7.28, lysozyme with positive charges can interact with CdTe nanoparticles. The resonance light-scattering (RLS) signals of functionalized nano-CdTe were greatly enhanced by lysozyme in the region of 300-600 nm, characterized with peaks located at 367, 470 and 533 nm. A linear relationship could be established between the enhanced RLS intensity and the lysozyme concentration in the range of 0.06-4.0 microg mL-1. The limit of detection was 9.5 ng mL-1. The contents of lysozyme were determined with recoveries of 95.6-104.8% and RSD of 1.5-2.3%, respectively. This method is sensitive, rapid, accurate and simple, and provides a new and reliable means for the quantity determination of lysozyme.