Analysis of double-stranded DNA by capillary electrophoresis using poly(ethylene oxide) in the presence of hexadecyltrimethylammonium bromide

Experimental and theoretical investigations of non-Newtonian electro-osmotic driven flow in rectangular microchannels

With the development of microfluidics, electro-osmotic (EO) driven flow has gained intense research interest as a result of its unique flow profile and the corresponding benefits in its application in the transportation of sensitive samples. Sensitive samples, such as DNA, are incapable of enduring strong flow shear induced by conventional hydrodynamic driven methods. EO driven flow is thus a niche area. However, even though there are a few research studies focusing on bio-fluidic samples related to EO driven flow, the majority of them are merely theoretical modeling without solid evidence from experiments due to the inherent complex rheological behavior of the bio-fluids. Challenges occur when the EO driven mechanism meets with complex rheology; vital questions such as can the zeta potential still be assumed to be constant when dealing with fluids with complex rheology? and "Does the shear thinning effect enhance electro-osmotic driven flow?" need to be answered. We conducted experiments using current monitoring and microscopy fluorescence methods, and developed a theoretical model by coupling a generalized Smoluchowski approach with the power-law constitutive model. We calculated the zeta potential and compared the experimental results with modeling to answer the questions. The results show a reduction of zeta potential in the presence of PEO aqueous solutions. A constant zeta potential is also indicated by varying the PEO concentration and the electric field strength.The shear thinning effect is also addressed via experimental data and theoretical calculations. The results show a promising enhancement of the EO driven velocity due to the shear thinning effect.

Electronic and vibrational spectra of novel Lanreotide peptide capped gold nanoparticles

Lanreotide, a somatostatin analogue peptide used for peptide receptor mediated therapy in metastatic neuroendocrine tumors, was used as capping agent of gold nanoparticles (GNPs) obtained by citrate reduction method. The displacement of the citrate groups from the GNPs surface by Lanreotide (LAN) molecules was evidenced by infrared and Raman spectra. The nanoparticles system, Au@LAN, was also characterized from HRTEM (High-Resolution Transmission Electron Microscopy) and Z-contrast images, UV-vis and EDS spectra. The stability on aging in water solution of the composite is discussed from the UV-vis spectra. The affinity constant of Au@LAN conjugate, calculated from Capillary Zone Electrophoresis data, was found to be 0.52. All the experimental evidence supports that the gold nanoparticles are effectively capped by the Lanreotide molecules through relatively strong covalent interactions. This result opens the possibility of combining the optical properties of gold nanoparticles and of Lanreotide molecule to form a bifunctional system for potential biomedical applications.

Contemporary sample stacking in CE

Sample stacking techniques remain an important tool for enhancement of the selectivity and sensitivity of analyses in contemporary CZE. This contribution reviews new knowledge on this topic published since 2006. It is organized according to the operational principles used, which include concentration adjustment, application of a pH step, MEKC and sweeping, and transient ITP. Techniques combining several of these principles and comparative studies are also included.

High-sensitive analysis of DNA fragments by capillary gel electrophoresis using transient isotachophoresis preconcentration and fluorescence detection

In this report aimed on further development of a high-sensitivity capillary gel electrophoresis (CGE) method for analysis of DNA fragments, we firstly explored online transient isotachophoresis (tITP) preconcentration combined with fluorescence detection (FD). The fluorescence signal (excitation: 488 nm; emission: 590 nm) was generated using the intercalating dye of ethidium bromide (EB). It was found when the leading electrolyte (LE) was injected behind the sample zone, such a special tITP mode has significant advantages to solve the bubble formation issue and to improve the analytical performance stability. Two standard DNA samples, a 50 bp DNA step ladder and the phiX174/HaeIII digest, were used to evaluate the qualitative and quantitative abilities of the tITP-FD approach. A highly diluted sample (10,000-fold in the water, e.g. the phiX174/HaeIII digest diluted from 500 microg/ml to the 50 ng/ml level) was enriched and detected; the LOD was down to 0.09 ng/ml for the 72 bp fragment, apparently improved more than 1000-fold in comparison with UV detection. Although the RSD of peak areas (n=3) was around 15.5% for the sample was electrokinetically injected, good linearity of peak area response showed that the proposed method is suitable for quantitative analysis.