Raman spectra of CdSe/ZnS quantum dots bioconjugated to ovarian cancer antibodies

This paper presents the analysis of Raman scattering spectra of CdSe/ZnS QDs covered by the amine-derivatized polyethylene glycol (PEG) polymer with and without bioconjugation to bio-molecules: mouse ovarian cancer (OC 125) antibodies (mab). Commercial CdSe/ZnS QDs used in the study are characterized by the color emission with the maximum at 525 nm (2.36 eV) at 300K. Samples of CdSe/ZnS QDs (bio-conjugated and non-conjugated) in the form of an 5 mm-size spot were dried on a polished surface of crystalline Si substrate to ensure a low level of light scattering background. Raman scattering spectra of non-conjugated QDs can be presented as a superposition of Raman lines: 212.2, 222.5, 308.3, 440.3, 521.0, 618.0, 667.8 943.5, 986.7, cm^-1 related to the CdSe core and silicon substrate. The Raman lines 1003.9, 1317.8, 1452.9, 1656.8, 2870.4, 2931.8 and 3059.9 cm^-1 deal with the vibration of COH, CH and OH groups of polymer, which covered QDs, were detected additionally. It is revealed that the QD bio-conjugation to the OC 125 antibodies is accompanied with the changes in the intensity of all types of Raman lines: related to the CdSe core, silicon substrate and polymer groups. The explanation of bioconjugation effects has been proposed and discussed.