Herein we introduce the first successful assay of biomolecule by in situ selective crystallization based quartz crystal microbalance (QCM). Selective crystallization of CaCO3 on QCM sensor surface was utilized as an efficient mass amplification strategy and enhanced the sensitivity of QCM significantly. High specificity is guaranteed by the cooperation of two functional groups: −N(CH3)3 and −COOH. Passivation of sensor surface is realized by self-assembly of −N(CH3)3, which effectively inhibited the nonspecific crystallization. The DNA target is detected through hybridization of probe DNA labeled with −COOH, which can effectively promot the in situ surface crystallization of CaCO3. The concentration of target DNA is reflected by the frequency shift of QCM which is directly induced by the surface crystallization. The selective crystallization based QCM platform is simple, straightforward, high sensitive, and high specific. We demonstrate the excellent LOD (2 aM DNA) and a linear range of 10aM to 1 nM for DNA. Detection of Ramos cells are also realized with a LOD of five cells and a linear range of 5–6000 cells.
The effective capture, release and reanalysis of circulating tumor cells (CTCs) are of great significance to acquire tumor information and promote the progress of tumor therapy. Particularly, the selective release of multiple types of CTCs is critical to further study; however, it is still a great challenge. To meet this challenge, we designed a smart DNAzyme probe-based platform. By combining multiple targeting aptamers and multiple metal ion responsive DNAzymes, efficient capture and selective release of multiple types CTCs were realized. Sgc8c aptamer integrated Cu2+-dependent DNAzyme and TD05 aptamer integrated Mg2+-dependent DNAzyme can capture CCRF-CEM cells and Ramos cells respectively on the substrate. With the addition of Cu2+ or Mg2+, CCRF-CEM cells or Ramos cells will be released from the substrate with specific selectivity. Furthermore, our platform has been successfully demonstrated in the whole blood sample. Therefore, our capture/release platform will benefit research on the molecular analysis of CTCs after release and has great potential for cancer diagnosis and individualized treatment.
Xueke Wu,Chenyuan Yan,Lixuan Mu,Yuan Wang,Guangwei She,Wensheng Shi
By assembling fluorophore-marked DNA stem-loops on the surface of gold nanobipyramids (AuNBPs) with an efficient photothermal conversion, we fabricated a multifunctional photothermal reagent (AuNBPs-mPEG/AA-TR). The sgc8 sequences that were embedded inside the DNA stem-loops can specifically target the PTK7, an overexpressed protein located on the surface of CCRF-CEM cells (human acute lymphoblastic leukemia T lymphocyte) to realize an active targeting function. Before the AuNBPs-mPEG/AA-TR bind to the PTK7 proteins, the DNA stem-loops are folded, and the fluorophore linked on the DNA stem-loop will be close to the AuNBPs. In this configuration, the fluorescence from the fluorophore is quenched by the AuNBPs. However, when the AuNBPs-mPEG/AA-TR bound to the PTK7 proteins through the sgc8 sequences, the DNA stem-loops can be opened partially to enable the fluorophore to be far away from the AuNBPs. As a result, the fluorescent signal will be activated. Therefore, the fluorescence can be used as a visual signal to reveal the binding between the AuNBPs-mPEG/AA-TR and CCRF-CEM cells (usually called activatable fluorescence labelling). While under irradiation of an 808 nm laser, the CCRF-CEM cells could be ablated through the photothermal therapy of the AuNBPs-mPEG/AA-TR with a high photothermal efficiency. Applying the AuNBPs-mPEG/AA-TR to Human B lymphoma cells (Ramos cells) and CCRF-CEM cells, we found that only the CCRF-CEM cells can be effectively targeted, actively fluorescently labeled, and readily ablated by the AuNBPs-mPEG/AA-TR. This work provides an alternative photothermal agent for the targeted therapy of tumors.
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