Developing microscopy based microfluidic SLS assay for on-chip hemoglobin estimation

Point-of-care (POC) biochemical assay is a highly important biochemical assay to estimate hemoglobin in the blood. High reagent volumes and complex-expensive optical setup requirements pose serious challenges when it comes to adopting conventional biochemical assays such as the Sodium Lauryl Sulfate (SLS) method into a POC device. Here, we report a modified SLS assay on a microfluidic platform, wherein the quantification is achieved using a simple microscopy-based imaging setup. Assay parameters, including SLS reagent-to-blood volume ratio, total reaction volume, the concentration of sodium dodecyl sulfate, and microfluidic chamber design, were optimized in order to achieve quantitation capability across a clinical range of hemoglobin using a path length suitable for the microfluidic platform. Besides quantitative correlation with a clinically accepted-validated standard method, the spectral absorption characteristics of the hemoglobin–SLS reagent mixture in the newly developed assay were compared with those of conventional SLS assays. The finalized chip design, including the reagent, cost 0.136 USD. The microfluidic chip in combination with an automated microscope was able to achieve a Pearson correlation of 0.99 in a validation study comparing the newly developed method and a commercially available hematology analyzer, with a turnaround time of 10 min, including incubation time. The clinical performance was ascertained, and the method achieved a sensitivity of 92.3% and a specificity of 53.8%. Overall, an automated microscopy-based biochemical assay was developed to estimate hemoglobin in whole-blood, using microfluidics technology, wherein the detector was a conventional camera associated with microscopy.