The detection and analysis of circulating tumor cells (CTCs) from patients′ blood is important to assess tumor status; however, it remains a challenge. In the present study, we developed a programmable DNA-responsive microchip for the highly efficient capture and nondestructive release of CTCs via nucleic acid hybridization. Transparent and patternable substrates with hierarchical architectures were integrated into the microchip with herringbone grooves, resulting in greatly enhanced cell-surface interaction via herringbone micromixers, more binding sites, and better matched topographical interactions. In combination with a high-affinity aptamer, target cancer cells were specifically and efficiently captured on the chip. Captured cancer cells were gently released from the chip under physiological conditions using toehold-mediated strand displacement, without any destructive factors for cells or substrates. More importantly, aptamer-containing DNA sequences on the surface of the retrieved cancer cells could be further amplified by polymerase chain reaction (PCR), facilitating the detection of cell surface biomarkers and characterization of the CTCs. Furthermore, this system was extensively applied to the capture and release of CTCs from patients′ blood samples, demonstrating a promising high-performance platform for CTC enrichment, release, and characterization.

The identification of hydroxylmethyl- and formylpyrimidines in genomic DNA was a landmark event in epigenetics. Numerous laboratories in related fields are investigating the biology of these and other nucleic acid modifications. However, limitations in the ability to detect and synthesize appropriate modifications are an impediment. Herein, we explored a remarkable development in the selective detection of 5-formyluracil in both single-stranded and double-stranded DNA under mild conditions. The "switch-on" specificity towards 5-formyluracil enabled a high signal-to-noise ratio in qualitatively and quantitatively detecting materials containing 5-formyluracil, which is not affected by the presence of abasic sites and 5-formylcytosine, the modified cytosine counterpart of 5-formyluracil. In summary, the innoxiousness, convenience, and cost-efficiency of the 5-formyluracil phosphoramidite synthetic routine would promote the understanding of the epigenetic role of this natural thymidine modification.

The availability and reliability of strategies for molecular biosensing over a finely adjustable dynamic range is essential to enhance the understanding and control of vital biological process. To expand the versatility and utility of nucleic acidrelated enzymes, we demonstrated a rational approach to acquiring tunable, pH-dependent deoxyribozymes (DNAzymes) with catalytic activities and response sensitivities that can be tuned through a simple change in solution pH. To do this, we capitalized upon the pH dependence of Hoogsteen interactions and designed i-motif- and triplex-based DNAzymes that can be finely regulated with high precision over a physiologically relevant pH interval. The modified DNAzymes are dependent upon pH for efficient cleavage of substrates, and their catalytic performance can be tuned by regulating the sequence of inserted i-motif/triplex structures. The principle of tunable, pH-dependent DNAzymes provides the opportunity to engineer pH-controlled DNA-machinery devices with unprecedented sensitivity to pH changes. For example, we constructed a DNA-walker device, the stepping rate of which could be adjusted by simply modulating solution pH within an interval of 5.6 to 7.4, as well as a DNA tetrahedron that can be opened at pH 6.4 and kept closed at pH 7.4. The potential of this approach is not limited to serve as pH-dependent devices, but rather may be combined with other elements to expand their practical usefulness.

To solve the problem of high temperature or long reaction time in hydrothermal synthesis of carbon dots (CDs), a novel method based on the promoting carbonization by hydrochloric acid as catalysis was developed in present work. The acid catalyzed carbon dots (ACDs) were prepared facilely from tryptophan and phenylalanine at 200 ℃ for 2 h. In our findings, the acids could promote significantly the formation of the ACDs' carbon core, as a result of the accelerating of the carbonization due to the easy deoxidation. The ACDs showed an average size of 4.8 nm, and consisted of high carbon crystalline core and various surface groups. The ACDs exhibited good optical properties and pH-dependent photoluminescence (PL) intensities. Furthermore, the ACDs were safe and biocompatible. The experimental results demonstrated that such new ACDs were connected with DNA-aptamer by EDC/NHS reaction maintaining both the bright fluorescence and recognizing ability on the cancer cells, which so could be served as an effective PL sensing platform. The resultant DNA-aptamer with ACDs (DNA-ACDs) could stick to human breast cancer cells (MCF-7) specifically, and exhibited high sensitivity and selectivity, indicating the potential applications in the cancer cells targeted imaging fields.