My first paper on microfluidic work has been published in Analitica Chimica Acta. This was the first project I worked on for my PhD work (actually the very first one didn't work. That was my advisor's crazy idea he wanted me to give a try. We abandoned that later on).
In this article, we have demonstrated a novel approach to enhancing the sensitivity of enzyme-linked immunosorbent assays (ELISA) through pre-concentration of the enzyme reaction product (resorufin/4- methylumbelliferone) in free solution.
Highly sensitive analytical techniques are required to estimate small amounts of disease markers (e.g., antibodies/antigens) in bodily fluids in order to detect the onset of dangerous diseases like cancers at their early stages. Here is the abstract of this paper.
The reported pre-concentration was accomplished by transporting the resorufin/4-methylumbelliferone molecules produced in the ELISA process towards a high ionic- strength buffer stream in a microfluidic channel while applying a voltage drop across this merging region. A sharp change in the electric field around the junction of the two liquid streams was observed to abruptly slow down the negatively charged resorufin/4-methylumbelliferone species leading to the reported pre- concentration effect based on the field amplified stacking (FAS) technique. It has been shown that the resulting enhancement in the detectability of the enzyme reaction product significantly improves the signal-to-noise ratio in the system thereby reducing the smallest detectable analyte concentration in the ELISA method. Applying the above-described approach, we were able to detect mouse anti-BSA and human TNF-a at concentrations nearly 60-fold smaller than that possible on commercial microwell plates. For the human TNF-a sample, this improvement in assay sensitivity corresponded to a limit of detec- tion (LOD) of 0.102 pg mL−1 using the FAS based microfluidic ELISA method as compared to 7.03 pg mL−1 obtained with the traditional microwell plate based approach. Moreover, because our ELISAs were per- formed in micrometer sized channels, they required sample volumes about two orders of magnitude smaller than that consumed in the latter case (1 uL versus 100 uL).