Nanoliter sample, assay

Bioluminescence-based analytical assays were used to measure various analytes in nanoliter sample volumes. Nanoliter volumes of multiple bioluminescent analytical assays were deposited in an array format and lyophilized. ATP-firefly luciferase (FFL) and NADH-bacterial luciferase (BL) platform reactions were compared. We achieved parallel sample delivery via sample-hydrated membranes. A CCD camera measured the luminescent kinetics for each assay. These miniaturized assays and instruments can he prepared as micro-analytical systems to operate in point-of-care (POC) diagnostic devices. 

Chromatographic methods also introduce a high level of uncertainty in qualitative and quantitative analysis, especially when low concentration levels are involved (e.g., CGC used for nanoliter samples of inorganic ions assay, with a limit of detection on the order of 10"9 mol/1, has an RSD larger than 5.0% 308). Because of the impossibility of having an ideal standard or RM for the analysis of most samples, the uncertainty of the qualitative analysis or peaks identification is high in chromatography.309... 

Several features of capillary electrophoresis are particularly interesting for forensic scientists, namely high separation efficiency, sensitivity, and small amount of samples (nanoliters) and solvents (a few milliliters per day). Regarding different operational modes, all of them are applied, although to a different extent, depending on the type of compounds to be assayed. 

As the analytes to be assayed are nearly always present in minute amounts, preconcentration steps are almost always necessary. The techniques used for this purpose have been mostly adopted from analytical procedures using gas or liquid chromatography as the separation step [5]. This fact is emphasized here because the appropriate adjustment of the sample preparation is necessary because the original procedures do not respect the fact that the sample volume injected into a CE system represents a few nanoliters only and requires a relatively high concentration of analytes assayed. However, in selected types of analysis, direct sample application is also possible (for a review, see Ref. 3). 

The ability to miniaturize assays to the sub-microliter level is largely dependent on the precision of liquid-handling systems. Modern pipetting and dispensing systems- enable components to be reproducibly added in volumes in the nanoliter range to thousands of samples per plate. The EVOscreen system includes a specially designed M2N unit which is able to reformat samples stored in any conventional format, such as 96-well plates, to... 

The strengths of the platform are the very small liquid volumes in the nanoliter range that can be handled with high precision, and the freedom to program the droplet movement. This cuts down sample and reagent consumption and allows a maximum of flexibility for the implementation of different assay... 

The aim of HTS and UHTS is cost-effectiveness and speed of compound scanning. Hence, the robotics system not only has to deliver fast and accurate liquid samples into the wells, it has to be miniaturized to conserve the volumes required of the valuable samples and expensive assay reagents. For the 1536 wells, the liquids being dispensed are in the nanoliter (10-9 L) to picoliter (Kh12 L) range. The ink jet technology provided the technological basis for liquid dispensation in HTS. 

The sample aliquot is precisely selected (see Figure lA), usually by means of either a loop-based or a time-based injection device. Typical sample volumes are 5-500 pi, although volumes in the nanoliter range can be handled in microfluidic systems. Volume-limited samples such as biological fluids are therefore easily analyzed m vivo assays are efficiently performed and operations such as dialysis, gas diffusion, and ion exchange are efficiently accomplished in-line. Reagent consumption is also low, typically 0.5-2.5 ml min per channel, thus... 

---