Evaluation of the bioconjugation efficiency of different quantum dots as probes for immunostaining tumor-marker proteins.

The differing bioconjugation efficiencies of quantum dots (QDs) are a practical obstacle to their popularization. Differences in bioconjugation efficiency based on immunostaining the same targeted molecules using different batches of QDs need to be evaluated prior to their application. In this paper, a quantitative method for evaluating the efficiency of QDs in staining tissues has been developed based on Hadamard transform (HT) spectral imaging. Proliferating cell nuclear antigens (PCNA) in breast cancer tissues were labeled with bioconjugated QD bioprobes using a 454 nm laser as the light source for fluorescence spectral imaging. Four-dimensional (4D) spectral imaging analysis of PCNA in cell nuclei was carried out using HT spectral microscopy based on immunostaining with different batches of QDs. The fluorescence intensity distributions in the cell nuclei were collected from the 4D images. Based on the information obtained from microscopic spectra and 4D images, differences in the bioconjugation efficiency among different batches of QDs were evaluated. The results demonstrate that it is possible to maintain uniform bioconjugation efficiencies with different QD bioconjugation processes in order to obtain accurate and reliable results in biomedical analysis and cancer diagnosis.