RESUMO
This paper introduces a two-step cascade enrichment method for isolating nucleated red blood cells (NRBCs) in maternal blood. The two-step enrichment platform consists of a positive enrichment process based on a red blood cell (RBC) hyperaggregation method and a negative enrichment process using microfluidic technology. An analytical evaluation using blood samples from patients with leukemia showed that the while blood cell (WBC) depletion and NRBC loss rates of the positive enrichment process were 93.98 % and 6.02 %, respectively. Through the two-step cascade enrichment method, 1-396 NRBCs and only 0-6 WBCs were isolated from 1 mL of 18 maternal blood samples. Experimental results also showed that the WBC depletion rate of the proposed two-step method was more than 625,000-fold, and the purity of enriched NRBCs ranged from 20 % to 100 %. Furthermore, SRY (the sex-determining region of the Y chromosome) genes were detected in enriched NRBCs, thereby demonstrating that enriched NRBCs contain fetus-derived NRBCs.