Microblood analyzers for the sensitive and portable detection of clinically relevant cardiac markers.

摘要

Every year over 6 million patients present at hospitals with chest pains, and it is critically important to determine if AMI is the cause as quickly as possible. Conventional ELISA based tests take at least 2 hours and must be performed at a centralized location. A MEMS ELISA test has the potential to reduce these test times considerably, while performing the test cheaply and more reliably at the point of care. A MEMS PDMS device was designed along with a small, portable reader to output the results. This device carried out assays in 15 minutes with greatly increased sensitivity over conventional ELISA. The device achieved a detection range for a flow based assay of 1 pg/mL--5 ng/mL with excellent sensitivity. This device is much more sensitive than the clinically relevant cutoff level of 5 ng/mL above which AMI is considered to have occurred in the patient. Even shorter assay times can be used for less sensitive detection.; To further improve detection sensitivity, assay times and sample volume required, an improved blocking agent was developed, and was composed of Pierce protein-freeRTM blocker, 0.05% Tween 20RTM, 0.1% n-dodecyl-beta-D-maltoside, and 20 mM HEPES buffered saline. This new blocking solution was able to reduce noise from non-specific binding by ∼10 5 fold compared to ∼102 fold for a conventional blocker, BSA. This allowed a fluorescence assay to be performed on serum samples containing cFABP in PDMS devices with no need for dilution or processing to prevent interference from serum constituents. This assay achieved a sensitivity of 0.1 ng/mL with a detection range of 0.1--1000 ng/mL in 11 minutes.; A laminar tube flow with 1st order wall reaction model was used for the cFABP microdevice assay, which could predict assay behavior for a range of conditions. The pseudo-first order reaction rate was estimated at ∼1.5x10-6 m/s, and it was determined that a 40 mum wide channel operated in the desirable reaction rate limited regime, rather than the undesirable mass transfer limited regime of conventional heterogeneous immunoassays. The model also provided reasonable estimates of assay sensitivity (0.5 pg/mL--600 pg/mL depending on the assay parameters).