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A label-free fluorescence method based on self-assembled DNA nanopompom has been developed for miRNA-21 detection. In the presence of miRNA-21, three DNA hairpin probes with split G-quadruplex assemble the DNA nanopompom. Based on the isothermal toehold-mediated DNA strand displacement reaction, the target miRNA can be catalytically recycled and trigger three DNA hairpin probes to self-assemble the DNA nanopompom and release the G-quadruplex. The formation of the G-quadruplex increases the fluorescence emission intensity of thioflavin. For thioflavin-based miRNA-21 detection, the excitation and emission wavelengths are set to 425 nm and 490 nm, respectively. The limit of detection for miRNA-21 is 0.8 pM according to F/F0 = 0.0031 × CmiRNA-21 + 1.0382 (R2 = 0.9978). This sensing system provides a low-cost, effective, and convenient method for miRNA detection, which holds great potential in biochemical diagnosis and clinical practice.

Polypeptides play a vital role in physiological processes of life. The pharmacological and medical value of polypeptides has attracted the attention of researchers in recent years. Aptamers are short, single stranded DNA or RNA developed by an in vitro process called systematic evolution of ligands by exponential enrichment (SELEX). Owing to the high affinity and specificity to the target, aptamer is also called “chemical antibody” or “chemist's antibody”. To date, there are two main application aspects for polypeptides-targeted aptamers. First, aptamer can be used as specific binding elements based on their ability of recognition, which would be applied to polypeptides sensing or imaging. The other one is that aptamer can also be used as antagonists based on their ability of inhibiting, which can restrict the activity of polypeptides and block the downstream signaling pathways in vivo, thus can be used to treat the disease associated with polypeptides. In this review, we summarize a number of polypeptides-targeted aptamers and the related applications in vitro and in vivo. Current issues and development trends throughout the screening, characterizing and applying of polypeptides-targeted aptamers are also discussed.

Existing drug delivery systems were not suitable for killing cells in the circulatory system specifically. Herein, we developed a novel localized drug delivery strategy, in which the release of anticancer agents was specifically triggered by circulating tumor cells. Meanwhile, damage to non-target cells was avoided.

G-quadruplexes are guanine-rich nucleic acid sequences that can act as universal signal-transducers and generate colorimetric, fluorescence, and chemiluminescence signals when complexed with different ligands. Due to their merits including easy modification and low cost, it is of great importance to explore new G-quadruplexes with improved performance. Herein the properties of newly identified G-quadruplexes 9th-3-35 and 10th-2-40 were investigated in detail with UV-vis spectra, circular dichroism (CD) spectra and fluorescence spectra. The results indicated that 9th-3-35 and 10th-2-40 exhibited excellent peroxidase-like activity, as well as fluorescence enhancement of thioflavin T (ThT). Furthermore, the application of G-quadruplexes to DNA detection was performed on account of the ThT fluorescence enhancement, and the limit of detection was as low as 8 pM. This study implied that 9th-3-35 and 10th-2-40 are competitive candidates as signal-transducers in the design of bioassays.

We developed a simple label-free aptamer-based method for C-reactive protein (CRP) detection. In our previous work, we obtained a G-rich aptamer named 6th-62-40, which exhibited good affinity and specificity toward CRP. Herein, we demonstrated that 6th-62-40 could enhance the fluorescence of thioflavin T (ThT). In the absence of CRP, ThT bound to the G-rich aptamer and formed an aptamer/ThT complex, which showed high fluorescence. However, the fluorescence decreased due to the formation of an aptamer/CRP complex in the presence of CRP. The proposed method was a rapid strategy for CRP detection with a detection limit of 380 pM.

Long-term, in vivo, fluorescent cell tracking probes are useful for understanding complex cellular processes including tissue regeneration, communication, development, invasion, and cancer metastasis. A near-infrared fluorescent, water-soluble probe is particularly important for studying these biological events and processes. Herein, a lysosome specific, near-infrared Bodipy probe with increased fluorescent intensity in the acidic, lysosome environment is reported. This Bodipy probe is packaged in a nanoparticle using DSPE-PEG2000. The resulting nanoparticle is intravenously delivered to a tumor xenograft, where the fluorescent Bodipy becomes useful for non-invasive, long-term, in vivo fluorescent tumor imaging for periods greater than 36 days. These long-term, in vitro and in vitro tracking data indicate that the described Bodipy nanoparticles hold great potential for monitoring biological processes.

Pancreatic polypeptide (PP) is a specific biomarker of nonfunctional pancreatic neuroendocrine tumors (NF-pNETs). Clinical significance of PP inspires researchers to make great efforts in developing sensitive and specific sensors. However, there is no existing biosensor for detecting PP that combines facility and functionality. Addressing this challenge, a pair of aptamers which could be used to develop a sandwich assay for PP is reported. First, several high affinity aptamers are screened through graphene oxide-based SELEX, and appropriate dual-aptamers which could bind to different epitopes of PP are identified through fluorescence assays. Then the feasibility of the dual-aptamers for constructing the sandwich assay is validated via dynamic light scattering. This sandwich assay shows considerable sensitivity and specificity. The above results imply that the dual-aptamers have the potential toward developing novel sensors for PP in clinical samples.

The novel synthesis of a dual-modality, pentamethine cyanine (Cy5) fluorescent, 18F positron emission tomography (PET) imaging probe is reported. The probe shows a large extinction coefficient and large quantum yield in the biologically transparent, near-infrared window (650–900 nm) for in vivo fluorescent imaging. This fluorophore bears the isotope, 18F, giving a 18F-PET/near-infrared fluorescent (NIRF), bi-modal imaging probe, that combines the long-term stability of NIRF and the unlimited penetration depth of PET imaging. The bi-modal probe is labeled with 18F in a quick, one-step reaction, which is important in working with the rapid decay of 18F. The bi-modal probe bears a free carboxyl group, highlighting a PET/NIRF synthon that can be conjugated onto many advanced biomolecules for biomarker-specific in vivo dual-modal PET/NIR tumor imaging, confocal histology, and utility in multi-fluorophore, fluorescence-guided surgery. Its potential in vivo biocompatibility is explored in a quick proof-of-principal in vivo study. The dye is delivered to A549 xenograft flank-tumors to generate PET and NIRF signals at the tumor site. The tumor distribution is confirmed in ex vivo gamma counting and imaging. Pentamethine cyanine (Cy5) has the ability to preferentially accumulate in tumor xenografts. We substitute the PET/NIRF probe for Cy5, and explore this phenomenon.

DNA nanostrucures are promising materials for biomedical applications. Herein, we established a “sense-and-treat” localized drug delivery system based on a DNA nanodevice to specifically destroy circulating tumor cells (CTCs) by synergetic chemotherapy and photodynamic therapy. The DNA nanodevices could sense the existence of CTCs and treat CTCs with anticancer agents. Typically, the presence of target cell promoted the formation of hairpin structure of aptamer, and then the aptamer-accompanied DNA tetrahedron would release from the supporter. The chemotherapy drugs (doxorubicin, Dox) loaded in DNA tetrahedron would destroy the CTCs specifically. Moreover, the photosensitizer labeled on DNA tetrahedron would be activated by lights and generated toxic 1O2, once DNA nanodevices bound CTCs flow through the superficial capillary. Unlike the aptamer only labeled with photosensitizer, the DNA nanodevice showed the capability to promote cellular internalization of anticancer agents, increase drug loading capacit...