Aptamer-functionalized microtubules for continuous and selective concentration of target analytes.

We present a novel biomolecule sensing method that enables sensitive and selective detection of target analytes as well as simultaneous separation of non-target analytes by utilizing microtubules (MTs) as a molecular carrier and a nanoporous hydrogel membrane (NHM) as a size-based sieve on a microfluidic chip. We functionalized MTs with aptamers, using a streptavidin and biotin linkage, to provide numerous binding sites for specific target analytes. Target analytes captured by the functionalized MTs from a mixture of complex analytes were transported by electrophoresis (EP) and then sieved by the NHM while non-target analytes passed through the NHM because of the size difference between the analytes and nanopores. Subsequently, the concentration and separation of only target analytes was achieved in a continuous and simultaneous manner because of more rapid transportation of MTs by electric fields. In this study, we demonstrated that our method can be used to detect target analytes at femtomolar levels and enrich the initial concentration by 105-106-fold within 10 min in terms of fluorescent signals. We also demonstrated that the method is approximately 10-100 times more sensitive than conventional nanobead-based detection methods in the light of fluorescent signals. For unlabeled target analytes in a real sample, the method can provide a means to obtain well purified and concentrated target analytes in the form of pellets for off-chip detection and analysis. Thus, we believe that using aptamer-functionalized MTs in conjunction with an NHM in the presence of electric fields can be widely utilized to facilitate the detection, concentration, and separation of specific biomolecule analytes on a chip. [ABSTRACT FROM AUTHOR]