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Abstract: Background: Recently, some research results showed that the circulating DNA in serum or plasma had potential for the molecular diagnosis and prognosis of certain cancers. Several methods have been employed for the quantification of circulating DNA. However, the circulating DNA levels obtained by various methods exhibited considerable differences. Additionally, these methods were labor-extensive and time-consuming, and not suitable for the quantification of circulating DNA in numerous samples due to the use of commercial DNA extraction kits for the purification of circulating DNA. We presented a new method for the quantification of circulating DNA in sera by capillary zone electrophoresis (CZE) with laser-induced fluorescence detection (LIF). Methods: In the present work, we want to make comparison between CZE-LIF assay and real time PCR for the quantification of circulating DNA levels. Linearity, intra and inter variability of two methods were evaluated. Results: The intra and inter variability of circulating DNA quantification by real-time PCR were 7.3% and 14.92%, respectively. In CZE assay the intra and inter variability were 4.19% and 6.91%, respectively. The R.S.D. values of the same coated capillary and different coated capillaries were 5.14% and 9.02%, respectively. Our data showed that the circulating DNA levels obtained by two methods had a good correlation. Moreover, we further confirmed that blood samples collection, serum preparation and other treatment procedures had a significant impact on the DNA levels in sera. Conclusion: Our data further illustrated that CZE-LIF is a simple, rapid and sensitive method for the quantification of circulating DNA in human sera, and well suitable for the analysis of a large number of samples in clinical diagnosis. [Copyright &y& Elsevier]

Abstract: In this paper, we present a universal, highly efficient and sensitive method for the characterization of quantum dot (QD) bioconjugates based on capillary electrophoresis with laser-induced fluorescent (LIF) detection. We first prepared CdTe QDs in aqueous phase by a chemical route with mercaptopropionic acid as a ligand, and then were coupled to certain proteins using bifunctional linkage reagent or electrostatic attraction. The QD bioconjugates were characterized by capillary electrophoresis with LIF detection. We found that QD bioconjugates were efficiently separated with free QDs by the optimization of buffer pH. Furthermore, we found that ultrafiltration was an effective and simple approach to purify QD conjugates with bovine serum albumin (BSA). Due to their broad absorption spectra and size dependent emission wavelength tunability, QDs can be excited to emit different colour fluorescence using a single wavelength laser source, and therefore, we believe that CE with LIF detection will become a universal and efficient tool for the characterization of QD bioconjugates. [Copyright &y& Elsevier]