Matrix Effects-A Challenge Toward Automation of Molecular Analysis

Many components in biological matrices influence the result of an analysis, affecting assay sensitivity and reproducibility. Improved matrix management becomes critical as requirements for higher assay sensitivity and increased process throughput become more demanding. There are several robotic laboratory automation systems that are commercially available, which serve to minimize matrix interference by performing purification and extraction protocols. However, there is an unmet need of inline matrix effect reduction solutions to reduce the processing time and cost for automated sample preparation. In microfluidics, effective matrix management is essential for developing fully integrated systems capable of meeting these requirements. This review surveys current biological matrix management techniques for liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods and binding assays with a view toward building automatable processes. For some systems, simple sample-preparation methods, such as dilution and protein precipitation (PPT), are sufficient, whereas other systems require labor-intensive methods, such as liquid-liquid extraction (LLE) and solid-phase extraction (SPE). To achieve high throughput, PPT, LLE, and SPE have been adopted to 96-well-plate format. Online SPE has also been coupled with LC-MS/MS to automate sample preparation and analysis of urine, plasma, and serum matrices. However, offline processing of whole blood is still required to obtain plasma and serum. The ultimate goal of implementing sample preparation to reduce matrix effects within untreated sample is to achieve reproducibility and sensitivity required by the application; therefore, inline sample preparation integrated with molecular analysis will be highly significant for laboratory automation. Electrokinetic methods have the potential of handling whole-blood, urine, and saliva samples and can be incorporated into microfluidic systems for full automation. Optimization of analysis conditions and the use of appropriate standards have likewise assisted in reducing or correcting matrix effects and will also be discussed.