Low cost biosensor-based molecular differential diagnosis of α-thalassemia (Southeast Asia deletion)

Thalassemias are genetic hematologic diseases which the homozygous form of α-thalassemia can cause either death in utero or shortly after birth. It is necessary to accurately identify high-risk heterozygous couples. We developed a quartz crystal microbalance (QCM) to identify the abnormal gene causing the commonly found α-thalassemia1, [Southeast Asia (SEA) deletion]. This work is an improved method of our previous study by reducing both production cost and analysis time.

A silver electrode on the QCM surface was immobilized with a biotinylated probe. The α-globin gene fragment was amplified and hybridized with the probe. Hybridization was indicated by changes of quartz oscillation. Each drying step was improved by using an air pump for 30 min instead of the overnight air dry. The diagnostic potency of the silver QCM was evaluated using 70 suspected samples with microcytic hypochromic erythrocytes.

The silver QCM could clearly identify samples with abnormal α-globin genes, either homozygous or heterozygous, from normal samples. Thirteen out of 70 blood samples were identified as carrier of α-thalassemia1 (SEA deletion). Results were consistent with the standard agarose gel electrophoresis. Using silver instead of gold QCM could reduce the production expense 10-fold. An air pump drying the QCM surface could reduce the analysis time from 3 days to 4 h.

The silver thalassemic QCM was specific, sensitive, rapid, cheap and field applicable. It could be used as a one-step definite diagnosis of α-thalassemia1 (SEA deletion) with no need for the preliminary screening test.