Bi-Specific Aptamers on Nanostructured Substrates Fail to Capture Cancer Cells

Circulating tumor cells (CTCs) have become established indicators for cancer therapy and prognosis. To effectively and specifically sort CTCs, numerous techniques have been developed in the last few decades. Recently, aptamer grafted nanostructured substrates have shown ultrasensitivity and considerable specificity in isolation of CTCs. However, due to the limitation of existing nanofabrication methods, large-scale fabrication of homogeneous nanostructured substrates is non-trivial and impose high fabrication costs. On the other hand, the heterogeneity of CTCs in biomarker expression also makes their isolation quite challenging. In this research, homogenous nanostructured surface on borosilicate glass substrates with more than 80 cm(2) surface areas are successfully prepared at one time. Such area can process approximately 8 mL of blood. Bi-specific aptamers targeting epithelial cell adhesion molecule and prostate specific membrane antigen, respectively, are also tested. However, due to formation of hetero-dimers between two different aptamers originating from inherent annealing property of nucleic acids, bi-specific aptamers fail to efficiently capture cancer cells. This limitation reveals that multi-specific aptamers, when applied to cell isolation, must be analyzed to exclude any potential formation of hetero-dimers due to complementary sequence matching.