Sampling assembly, electrostatic

We also reported a concept for a sandwich immunoassay that is completely performed on-chip using streptavidin-coated beads as substrate [17]. The latter were electrostatically self-assembled on aminosilane micropattems at the bottom of a microfluidic channel. We used mouse IgG diluted in phosphate buffered saline (PBS) with 1% bovine serum albumin (BSA) solution as target antigen. The fluorescent sandwich immunocomplex was formed on the beads during the operation of the chip both in stop-flow and continuous flow modes. Target mouse IgG antigen could be detected down to a concentration of 15 ng/mL in stop-flow mode and 250 pg/mL in continuous flow mode, using only 1,300 nL of sample volume. 

A set of experiments was carried out to study the activity of PAH when it was coated on silicon and silica glass substrates. The substrates were prepared by alternate electrostatically self-assembled (ESA) adsorptions of polyacryUc acid (PAAcid) and PAH from their respective solutions to a substrate to form 10-11 bilayers. These substrates were dipped into TMOS solutions, removed after 5 min, washed with deionized water, and then dried. The samples were then scanned under SEM for silica formation on the substrates. There was no evidence for the controlled formation of silica on these substrates except for a few irregular shaped silica regions, which were small in number. However, when TMOS was added to a solution of a mixture of PAH and PAAcid, silica precipitation was observed. 

As a matter of fact, the CoTRPyP modified electrodes provide a considerable enhancement of the sulfite response and decrease of the overpotential, shifting the oxidation wave to the onset of the Ru(II/III) redox wave ( + 0.70 V vs saturated Ag/ AgClKci)- A similar behavior was observed for the electrostatically assembled CoTRPyP/ZnTPPS films (122, 251). The consistency of the FIA method using modified electrodes was quite good. In addition, the method can be easily scaled up to a large number of samples, in contrast to the tedious and time-consuming iodometric titration procedures. 

If the concentration of the amphiphilic polymer in the sample is above its CMC, there are two cases to consider the micellar solution is added to the DNA solution or the DNA solution is added to a micellar solution. In the first case, where the micellar solution of polycation is added to DNA, the micelles are immediately diluted in the DNA solution, which on one hand can mean that the polymer concentration is under its CMC and therefore that the polymer is only present as individual chains in solution (unimers), on the other hand, that there is concurrence between self-assembly of micelles versus electrostatic interactions with a large quantity of negatively charged material. In this case, the micelles are usually destabilized as soon as they reach the DNA solution (Scheme 11, case 1). 

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