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摘要
Cell isolation from biological samples is crucial in not only basic research, but also in clinical diagnostics. However, there are only a limited number of high-affinity ligands such as antibodies commercially available for cell isolation. An aptamer provides an alternative option as an affinitive ligand with satisfactory stability and low cost. Unfortunately, only aptamers for certain targets can be screened and modified to achieve high affinity and specificity. Rolling circle amplification (RCA) of a particular aptamer has been shown to improve its binding affinity to targets due to the tandem effect of producing long repeating aptamer sequences. However, the improved binding affinity of the amplified multivalent aptamer could only be achieved within a certain length and would decrease beyond a threshold amplification length or repeat number. Herein, we investigated the effect of nanostructural features of the multivalent aptamer produced by RCA on the cell enrichment efficiency for the first time. The RCA-amplified multivalent aptamer tended to intertwine into micro-scale coils, resulting in a decrease in effective binding sites and a lower enrichment efficiency (5.29%) of the target cells. In contrast, the multivalent aptamer could be stretched into nano-strands by heat-activation, exposing more effective binding sites, which could increase the cell enrichment efficiency to 86%. The stretched multivalent aptamer used as an ultra affinity agent provides a powerful tool for highly efficient cell capture and separation for personalized disease diagnosis and cell-based research.
