Light-Controlled Recruitable Hybridization Chain Reaction on Exosome Vehicles for Highly Sensitive MicroRNA Imaging in Living Cells

Simultaneous detection of multiple microRNAs based on fluorescence resonance energy transfer under a single excitation wavelength

MicroRNAs (miRNAs) play a key role in physiological processes, and their dysregulation is closely related to various human diseases. Simultaneous detection of multiple miRNAs is pivotal to cancer diagnosis at an early stage. However, most multicomponent analyses generally involve multiple excitation wavelengths, which are complicated and often challenging to simultaneously acquire multiple detection signals. In this study, a convenient and sensitive sensor was developed to simultaneously detection of multiple miRNAs under a single excitation wavelength through the fluorescence resonance energy transfer between the carbon dots (CDs)/quantum dots (QDs) and graphene oxide (GO). A hybridization chain reaction (HCR) was triggered by miRNA-141 and miRNA-21, resulting in the high sensitivity with a limit of detection (LOD) of 50 pM (3σ/k) for miRNA-141 and 60 pM (3σ/k) for miRNA-21. This simultaneous assay also showed excellent specificity discrimination against the mismatch. Furthermore, our proposed method successfully detected miRNA-21 and miRNA-141 in human serum samples at a same time, indicating its diagnostic potential in a clinical setting.

Intelligent near-infrared light-activatable DNA machine with DNA wire nano-scaffold-integrated fast domino-like driving amplification for high-performance imaging in live biological samples

While there is significant potential for DNA machine-built enzyme-free fluorescence biosensors in the imaging analysis of live biological samples, they persist certain shortcomings. These encompass a deficiency of signal enrichment within a singular interface, uncontrolled premature activation during bio-delivery, and a slow reaction rate due to free nucleic acid collisions. In this contribution, we are committed to resolving the above challenges. Firstly, a single-interface-integrated domino-like driving amplification is constructed. In this conception, a specific target acts as the domino promotor (namely the energy source), initiating a cascading chain reaction that grafts onto a singular interface. Next, an 808 nm near-infrared (NIR) light-excited up-converting luminescence-induced light-activatable biosensing technique is introduced. By locking the target-specific identification segment with a photo-cleavage connector, the up-converted ultraviolet emission can activate target binding in a completely controlled manner. Moreover, a fast reaction rate is achieved by confining nucleic acid collisions within the surface of a DNA wire nano-scaffold, leading to a substantial enhancement in local contact concentration (30.8-fold increase, alongside a 15 times elevation in rate). When a non-coding microRNA (miRNA-221) is positioned as the model low-abundance target for proof-of-concept validation, our intelligent DNA machine demonstrates ultra-high sensitivity (with a limit of detection down to 62.65 fM) and good specificity for this hepatic malignant tumor-associated biomarker in solution detection. Going further, it is worth highlighting that the biosensing system can be employed to carry out high-performance imaging analysis in live bio-samples (ranging from the cellular level to the nude mouse body), thereby propelling the field of DNA machines in disease diagnosis.

Light-activated CRISPR-Cas12a for amplified imaging of microRNA in cell cycle phases at single-cell levels

An ortho-nitrobenzyl phosphate ester-caged nucleic acid hairpin structure coupled to the CRISPR-Cas12a complex is introduced as a functional reaction module for the light-induced activation of the CRISPR-Cas12a (LAC12a) machinery toward the amplified fluorescence detection of microRNA-21 (miRNA-21). The LAC12a machinery is applied for the selective, in vitro sensing of miRNA-21 and for the intracellular imaging of miRNA-21 in different cell lines. The LAC12a system is used to image miRNA-21 in different cell cycle phases of MCF-7 cells. Moreover, the LAC12a machinery integrated in cells enables the two-photon laser confocal microscopy-assisted, light-stimulated spatiotemporal, selective activation of the CRISPR-Cas12a miRNA-21 imaging machinery at the single-cell level and the evaluation of relative expression levels of miRNA-21 at distinct cell cycle phases. The method is implemented to map the distribution of cell cycle phases in an array of single cells.

Dark-field imaging and fluorescence dual-mode detection of microRNA-21 in living cells by core-satellite plasmonic nanoprobes

The in situ precise quantification and simultaneous imaging of low abundance microRNAs (miRNAs) within living cells is critical for cancer diagnosis, yet it remains a significant challenge. Leveraging the excellent sensitivity and spatiotemporal resolution of dark-field microscopy (DFM) and fluorescence imaging, we have successfully devised a novel detection approach using dual-signal reporter probes (DSRPs). These probes allow for highly sensitive detection of miRNA-21 in living cells via toehold-mediated strand displacement cascades. The DSRPs were constructed by Au nanoparticles and Ag nanoclusters core-satellite nanostructures. After the recognition of miRNA-21, the strand displacement cascades were triggered, inducing the disassembly of the Au/Ag core-satellite nanostructure with apparent scattering intensity decrease and peak wavelength shifts. Additionally, the fluorescence of Ag clusters could be recovered and further enhanced when in close proximity to specific guanine-rich strands. The dual-signal response capability enables the accurate detection of miRNA-21 from 1 fM to 1 nM, with a limit of detection reached 0.75 fM. DFM and fluorescent imaging of living cells efficiently confirms the applicable detection of miRNA-21 in complex detection media. The biosensor based on DSRPs represents a promising nanoplatform for visual monitoring and imaging of biomolecules in living cells, even at the single particle level.

A dual-core 3D DNA nanomachine based on DNAzyme positive feedback loop for highly sensitive MicroRNA imaging in living cells

A double 3D DNA walker nanomachine by DNAzyme self-driven positive feedback loop amplification for the detection of miRNA was constructed. This method uses two gold nanoparticles as the reaction core, and because of the spatial confinement effect the local concentration of the reactants increase the collision efficiency was greatly improved. Meanwhile, the introduction of positive feedback loop promotes the conversion efficiency. In presence of miRNA-21, a large amount of DNAzyme was released and hydrolyze the reporter probe, resulting the recovery of fluorescence signal. The linear range for miRNA-21 is 0.5-60 pmol/L, and the detection limit is 0.41 pmol/L (S/N = 3). This nanomachine has been successfully used for accurate detection of miRNA-21 expression levels in cell lysates. At the same time, it can enter cells for intracellular miRNA-21 fluorescence imaging, distinguishing tumor cells from normal cells. This combination of in vitro detection and imaging analysis of living cells can achieve the goal of jointly detecting cancer markers through multiple pathways, providing new ideas for early diagnosis and screening of diseases.

A two-layer circuit cascade-based DNA machine for highly sensitive miRNA imaging in living cells

Sensitive detection of microRNA (miRNA), one of the most promising biomarkers, plays crucial roles in cancer diagnosis. However, the low expression level of miRNA makes it extremely urgent to develop ultrasensitive and highly selective strategies for quantification of miRNA. Herein, a DNA machine is rationally constructed for amplified detection and imaging of low-abundance miRNA in living cells based on the toehold-mediated strand displacement reaction (TMSDR). The isothermal and enzyme-free DNA machine with low background leakage is fabricated by integrating two DNA circuits into a cascade system, in which the output of one circuit serves as the input of the other one. Once the DNA machine is transfected into breast cancer cells, the overexpressed miRNA-203 initiates the first-layer circuit through TMSDR, leading to the concentration variation of fuel strands, which further influences the assembly of hairpin DNA in the second-layer circuit and the occurrence of fluorescence resonance energy transfer (FRET) for fluorescence imaging. Benefiting from the cascade of the two-layer amplification reaction, the proposed DNA machine acquires a detection limit down to 4 fM for quantification of miR-203 and a 10 000-fold improvement in amplification efficiency over the single circuit. Therefore, the two-layer circuit cascade-based DNA machine provides an effective platform for amplified analysis of low-abundance miRNA with high sensitivity, which holds great promise in biomedical and clinical research.

Near-Infrared Light-Powered and DNA Nanocage-Confined Catalytic Hairpin Assembly Nanobiosensor with a Nucleic Acid Restriction Behavior and Reinforced Enzymatic Resistance for Robust Imaging Assay in Live Biosystems

While DNA amplifier-built nanobiosensors featuring a DNA polymerase-free catalytic hairpin assembly (CHA) reaction have shown promise in fluorescence imaging assays within live biosystems, challenges persist due to unsatisfactory precision stemming from premature activation, insufficient sensitivity arising from low reaction kinetics, and poor biostability caused by endonuclease degradation. In this research, we aim to tackle these issues. One aspect involves inserting an analyte-binding unit with a photoinduced cleavage bond to enable a light-powered notion. By utilizing 808 nm near-infrared (NIR) light-excited upconversion luminescence as the ultraviolet source, we achieve entirely a controllable sensing event during the biodelivery phase. Another aspect refers to confining the CHA reaction within the finite space of a DNA self-assembled nanocage. Besides the accelerated kinetics (up to 10-fold enhancement) resulting from the nucleic acid restriction behavior, the DNA nanocage further provides a 3D rigid skeleton to reinforce enzymatic resistance. After selecting a short noncoding microRNA (miRNA-21) as the modeled low-abundance sensing analyte, we have verified that the innovative NIR light-powered and DNA nanocage-confined CHA nanobiosensor possesses remarkably high sensitivity and specificity. More importantly, our sensing system demonstrates a robust imaging capability for this cancer-related universal biomarker in live cells and tumor-bearing mouse bodies, showcasing its potential applications in disease analysis.

Stimuli-responsive probes for amplification-based imaging of miRNAs in living cells

MicroRNAs (miRNAs) have emerged as important biomarkers in biomedicine and bioimaging due to their roles in various physiological and pathological processes. Real-time and in situ monitoring of dynamic fluctuation of miRNAs in living cells is crucial for understanding these processes. However, current miRNA imaging probes still have some limitations, including the lack of effective amplification methods for low abundance miRNAs bioanalysis and uncontrollable activation, leading to background signals and potential false-positive results. Therefore, researchers have been integrating activatable devices with miRNA amplification techniques to design stimuli-responsive nanoprobes for "on-demand" and precise imaging of miRNAs in living cells. In this review, we summarize recent advances of stimuli-responsive probes for the amplification-based imaging of miRNAs in living cells and discuss the future challenges and opportunities in this field, aiming to provide valuable insights for accurate disease diagnosis and monitoring.

Construction of a self-sufficient DNA circuit for amplified detection of kanamycin

Improper use of kanamycin can lead to trace kanamycin residues in animal-derived foods, which can pose a potential threat to public health. Isothermal enzyme-free DNA circuits have provided a versatile toolbox for detecting kanamycin residues in complicated food samples, yet they are always limited by low amplification efficiency and intricate design. Herein, we present a simple-yet-robust nonenzymatic self-driven hybridization chain reaction (SHCR) amplifier for kanamycin determination with 5800-fold sensitivity over that of the conventional HCR circuit. The analyte kanamycin-activated SHCR circuitry can generate numerous new initiators to promote the reaction and improve the amplification efficiency, thus achieving an exponential signal gain. With precise target recognition and multilayer amplification capability, our self-sustainable SHCR aptasensor facilitated the highly sensitive and reliable analysis of kanamycin in buffer, milk, and honey samples, thus holding great potential for the amplified detection of trace contaminants in liquid food matrices.

Fluorescence-Enhanced Dual-Driven "OR-AND" DNA Logic Platform for Accurate Cell Subtype Identification

Developing an endogenous stimuli-responsive and ultrasensitive DNA sensing platform that contains a logic gate biocomputation for precise cell subtype identification holds great potential for disease diagnosis and prognostic estimation. Herein, a fluorescence-enhanced "OR-AND" DNA logic platform dual-driven by intracellular apurinic/apyrimidinic endonuclease 1 (APE 1) or a DNA strand anchored on membrane protein Mucin 1 (MUC 1) for sensitive and accurate cell subtype identification was rationally designed. The recognition toehold of the traditional activated probe (TP) was restrained by introducing a blocking sequence containing an APE 1 cleavable site (AP-site) that can be either cleaved by APE 1 or replaced by Mk-apt, ensuring the "OR-AND" gated molecular imaging for cell subtype identification. It is worth noting that this "OR-AND" gated design can effectively avoid the missing logical computation caused by membrane protein heterogeneous spatial distribution as a single input. In addition, a benefit from the excellent plasmon-enhanced fluorescence (PEF) ability of Au NSTs is that the detection limit can be decreased by nearly 165 times. Based on this, not only different kinds of MCF-7, HepG2, and L02 cells, but also different breast cancer cell subtypes, including malignant MCF-7, metastatic MDA-MB-231, and nontumorigenic MCF-10A cells, can be accurately identified by the proposed "OR-AND" gated DNA logic platform, indicating the prospect of this simple and universal design in accurate cancer screening.

Dual-Locked DNAzyme Platform for In Vitro and In Vivo Discrimination of Cancer Cells

Imaging of tumor-associated microRNAs (miRNAs) can provide abundant information for cancer diagnosis, whereas the occurrence of trace amounts of miRNAs in normal cells inevitably causes an undesired false-positive signal in the discrimination of cancer cells during miRNA imaging. In this study, we propose a dual-locked (D-locked) platform consisting of the enzyme/miRNA-D-locked DNAzyme sensor and the honeycomb MnO₂ nanosponge (hMNS) nanocarrier for highly specific cancer cell imaging. For a proof-of-concept demonstration, apurinic/apyrimidinic endonuclease 1 (APE1) and miR-21 were chosen as key models. The hMNS nanocarrier can efficiently release the D-locked DNAzyme sensor in living cells due to the decomposition of hMNS by glutathione, which can also supply Mn²⁺ for DNAzyme cleavage. Ascribing to the smart design of the D-locked DNAzyme sensor, the fluorescence signal can only be generated by the synergistic response of APE1 and miR-21 that are overexpressed in cancer cells. Compared with the miRNA single-locked DNAzyme sensor and the small-molecule (ATP)/miRNA D-locked DNAzyme sensor, the proposed enzyme (APE1)/miRNA D-locked DNAzyme sensor exhibited 2.6-fold and 2.4-fold higher discrimination ratio (F_cancer/F_normal) for cancer cell discrimination, respectively. Owing to the superior performance, the D-locked strategy can selectively generate a fluorescence signal in cancer cells, facilitating accurate discrimination of cancer both in vitro and in vivo. Furthermore, this D-locked platform is easily adaptable toward other target molecules by redesigning the DNA sequences. The outstanding performance and expansibility of this D-locked platform holds promising prospects for cancer diagnosis and related biomedical applications.