Physico-Chemical Properties of CdTe/Glutathione Quantum Dots Obtained by Microwave Irradiation for Use in Monoclonal Antibody and Biomarker Testing

Abstract

In this report, we present the results on the physicochemical characterization of cadmium telluride quantum dots (QDs) stabilized with glutathione and prepared by optimizing the synthesis conditions. An excellent control of emissions and the composition of the nanocrystal surface for its potential application in monoclonal antibody and biomarker testing was achieved. Two samples (QDYellow, QDOrange, corresponding to their emission colors) were analyzed by dynamic light scattering (DLS), and their hydrodynamic sizes were 6.7 nm and 19.4 nm, respectively. Optical characterization by UV-vis absorbance spectroscopy showed excitonic peaks at 517 nm and 554 nm. Photoluminescence spectroscopy indicated that the samples have a maximum intensity emission at 570 and 606 nm, respectively, within the visible range from yellow to orange. Infrared spectroscopy showed vibrational modes corresponding to the functional groups OH-C-H, C-N, C=C, C-O, C-OH, and COOH, which allows for the formation of functionalized QDs for the manufacture of biomarkers. In addition, the hydrodynamic radius, zeta potential, and approximate molecular weight were determined by dynamic light scattering (DLS), electrophoretic light scattering (ELS), and static light scattering (SLS) techniques. Size dispersion and the structure of nanoparticles was obtained by Transmission Electron Microscopy (TEM) and by X-ray diffraction. In the same way, we calculated the concentration of Cd²⁺ ions expressed in mg/L by using the Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-OES). In addition to the characterization of the nanoparticles, the labeling of murine myeloid cells was carried out with both samples of quantum dots, where it was demonstrated that quantum dots can diffuse into these cells and connect mostly with the cell nucleus.

Keywords: cadmium telluride; glutathione; microwave; murine myeloid cells; quantum dots.

Figure 1

Average size distribution of QD samples. (a) Intensity distribution, (b) volume distribution.

Figure 2

HRTEM images and size distribution of (a) QDYellow sample, (b) QDOrange sample, (c) XRD patterns of both samples (ICSD-093942).

Figure 3

FT-IR spectra for CdTe/GSH-QDs.

Figure 4

Determination of the average zeta potential.

Figure 5

Absorbance spectrum of QDYellow (black line), of which the maximum excitonic peak is localized around 517 nm, and of QDOrange (red line), of which the maximum of the excitonic peak is localized around to 554 nm.

Figure 6

Normalized emission spectra corresponding to analyzed samples. For QDYellow, the maximum wavelength of emission was 570 nm, under an excitation wavelength of 472 nm. For QDOrange, the maximum wavelength of emission was 606 nm, under an excitation wavelength of 473 nm.

Figure 7

(a) Analytical signal for Cd²⁺, (b) calibration curve for Cd²⁺.

Figure 8

Micrographs of murine myeloid cells labeled with quantum dots. (a) Myeloid cells labeled with CdTe/GSH/Yellow with 40× green filter. (b) Myeloid cells labeled with CdTe/GSH/Orange with 40× red filter. (c) Myeloid cells labeled with DAPI 100×.