Adsorption microchannel

Munson MS, Hasenbank MS, Fu E, Yager P (2004) Suppression of non-specific adsorption using sheath flow. Lab Chip 4 438 145 Munson MS, Hawkins KR, Hasenbank MS, Yager P (2005) Diffusion-based analysis in a sheath flow microchannel the sheath flow T-sensor. Lab Chip 5 856-862... 

In order to demonstrate the performance of this electrochemical microimmunoassay platform in terms of limits of detection and dynamic range, a series of ALP tests has been conducted in 100 nL polyimide microchips. To this end, anti-phosphatase antibodies have first been immobilised on the surface of the microchannels at a concentration of 10 pg/mL in a flow-through mode (4mL of anti-ALP solution pumped at 0.4 mL/min during 10 min) so as to saturate the microchannel surface by physical adsorption. Then, the surface was blocked with a 5% BSA in phosphate buffer in order to block the free sites remaining on the surface. Solutions of ALP at various concentrations (namely 0, 0.1, 1, 10 and 100 pM) were then injected and incubated during 9 min in the... 

In protein separations, adsorption of protein molecules to the channel wall is always a problem. For instance, adsorption of green fluorescent protein (GFP) to the walls of plastic polycarbonate microchannels is problematic [597]. To avoid protein adsorption, the microchannels normally need to be treated with coatings, such as (acryloylaminopropyl)trimethylammonium chloride (BCQ), [806,809,812] or methacrylocyloxyethylphosphorylcholine (MPC) [1032]. In... 

Adsorption processes can benefit from microchannel devices, because the apparent adsorption kinetics in conventional reactors are often much slower than intrinsic adsorption kinetics as a result of thermal and diffusional resistances. Microchannels provide short transfer distances for both mass and energy. 

In addition to electrophoresis-based collection of DNA in microchannels (see Section 7.7.3), adsorbents have been used to collect and purify DNA. In these cases, microchannels are generally used because of the small quantity of material requiring collection. Using solid phase extraction, sorbent particles of nano- and micro-silica and micro-sized octadecylsilica were immobilized using sol-gel chemistry to hU the microchannels of the microfluidic device [194]. DNA as well as several organic compoimds were evaluated for adsorption and desorption. They showed excellent adsorption, but poor recovery because they were difficult to extract. 

Fig. 7.15 Adsorption and desorption processes fora temperature swing adsorption (TSA) system. By using microchannel devices, the thermal mass is low and heat transfer is rapid, resulting in a small device [195].

MicroChannel electrophoretic devices are being developed to meet the need for better methods for protein separation and analysis. Interactions between analytes and the wall of the separation channel can reduce the efficiency of microchannel electrophoretic separations. These analyte-wall interactions are especially problematic for protein separations. Consequently, a large volume of the literature is focused on preventing protein adsorption on the walls of the microchannel by varying the microchannel material [238], by employing surfactants [239], or by modifying the microchannel surfaces [240]. 

Minimal adsorption to or nonspecific interaction with microchannel walls... 

Microchip substrate is open to a variety of materials. Silicon wafer is a good material to build up microstructures if fabrication facilities are available. Glass has good chemical and optical properties, and some polymers are cost effective for mass production. The surface treatment of the microchannel is critically important for all materials. This is because of the nonspecific adsorption of the analytes and antibodies to the channel wall that will result in considerable analytical error. It is very important to modify the surface with some blocking reagents or other materials to prevent protein adsorption before experiments. Therefore, we must choose a material of which, surface chemistry is well understood. 

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