Direct hemoglobin measurement on a centrifugal microfluidic platform for point-of-care diagnostics

We present a novel concept to determine relevant biochemical markers for applications in the field of emergency diagnostics. Our modular setup comprises a disposable polymer disk which hosts microfluidic structures and optical beam-guidance elements. The beam of a standard laser is guided by total internal reflection (TIR) at V-grooved retro reflectors which are monolithically integrated on a “lab-on-a-disk”. This way, the optical path length through the commonly flat detection cell and thus the sensitivity of colorimetric assays is massively enhanced compared to direct (perpendicular) beam incidence. The reusable analyzer compactly incorporates a standard drive to spin the disk, a dispensing unit, a low-cost laser, and a spectrophotometer serving as flexible detector for different assay formats. The competitive performance of the setup was proven by the rapid and accurate determination of the concentration of hemoglobin (Hb) in human whole blood. Outstanding features are a high degree of linearity (R2 = 0.993) between the optical signal and the Hb, a good reproducibility of CV = 2.9%, and a time-to-result of 100 s, only.