An entropy-driven DNA nanomachine for microRNA detection using a personal glucose meter

New sensing methods using commercially available products: Based on PGM and PTS

In recent years, detection technology has made remarkable progress in the field of food safety, in vitro diagnosis, and environment monitoring under the impetus of trace substances detection requirements. However, in sharp contrast to the rapid development of detection technology, its marketization process is relatively lagging behind. One possible approach is to integrate novel sensing strategies with mature commercial devices, such as personal glucose meters (PGMs) and pregnancy test strips (PTS) to speed up their marketization process. In this review, we systematically summarized design principle, evolution, and application progress for the integration of novel sensing strategies with commercial devices PGMs and PTS. Meanwhile, key factors and difficulties for the integration novel sensing strategies with commercial devices were emphasized. More importantly, the future of prospects and remaining challenges were discussed.

Novel Multimode Assay Based on Asymmetrically Competitive CRISPR and Raman Barcode Spectra for Multiple Hepatocellular Carcinoma Biomarkers Detection

Commercial pregnancy test strips (PTS) possess the advantages of lower price, higher stability, and better repeatability and have been popularized to integrate with novel sensing strategies to detect other disease biomarkers, which accelerates the commercialization process of those novel sensing strategies. However, the current integration of novel sensing strategies into commercial PTS still faced the problems of insufficient quantification, low sensitivity, and lack of multiple detection capabilities. Hence, we proposed the concept of "visual classification recognition, spectral signal subdivision" for multiple hepatocellular carcinoma biomarkers (miRNA122 and miRNA233) detection with dual signals based on asymmetric competitive CRISPR (acCRISPR) and surface-enhanced Raman spectroscopy coupling with PTS, named the acCRISPR-PTS-SERS assay. In this assay, acCRISPR was used as a nonamplified cascaded signal amplification method to improve the sensitivity of detection. Two AuNPs-based core-shell Raman tags, each corresponding to different miRNA biomarkers, were used to achieve both visual recognition and spectral segmentation to enhance the quantification of PTS detection and the capability for multiple detection. Under the optimal conditions, the LOD for miRNA122 and miRNA223 were 10.36 and 4.65 fM, respectively. The sensitivity was enhanced by nearly 2 orders of magnitude. In the future, simultaneous hand-held detection for fingerprint barcodes of different cancers can be achieved with the assistance of a microfluidic chip and smartphone.

Enzyme-encapsulated metal-organic framework ZIF-8-mediated biosensor for ultrasensitive detection of urinary prostatic exosomal protein using a glucose meter

A highly sensitive and efficient home-use method is impressive and promising in the self-monitoring of chronic prostatitis (CP). Herein, we developed a glucose oxidase-zeolitic imidazolate framework-8-antibody composite (GOx@ZIF-8@Ab2) to achieve highly sensitive point-of-care testing (POCT) of urinary prostatic exosomal protein (PSEP) by combining it with a personal glucometer (PGM). The developed GOx@ZIF-8@Ab2 was prepared through a simple but effective biomineralization reaction and a strong binding affinity between Zn2+ and Fc region of the antibody. This bifunctional material GOx@ZIF-8@Ab2 could not only specifically recognize the PSEP via immunoreaction but also wrap a large number of GOx molecules. Following the sandwich immunoreaction, the prepared GOx@ZIF-8@Ab2 facilitated hydrolysis of glucose in a one-to-many fashion, amplifying the detection signal and greatly improving the sensitivity of PGM detection. In comparison to those of the conventional enzyme-linked immunosorbent assay (ELISA), the detection time of the developed technique was shortened to 45 minutes and its limit of detection (0.23 pg mL-1) was reduced by 4-5 orders of magnitude. This technique was successfully utilized for detecting PSEP in human urine samples with a recovery rate of 96-116%. Owing to its rapid, ultrasensitive, specific and portable features, the as-designed platform based on GOx@ZIF-8@Ab2 and the PGM device holds great promise as a home-use POCT platform for self-monitoring of CP and other chronic diseases.

Recent Developments in Personal Glucose Meters as Point-of-Care Testing Devices (2020-2024)

Point-of-care testing (POCT) is a contemporary diagnostic approach characterized by its user-friendly nature, cost efficiency, environmental compatibility, and lack of reliance on professional experts. Therefore, it is widely used in clinical diagnosis and other analytical testing fields to meet the demand for rapid and convenient testing. The application of POCT technology not only improves testing efficiency, but also brings convenience and benefits to the healthcare industry. The personal glucose meter (PGM) is a highly successful commercial POCT tool that has been widely used not only for glucose analysis, but also for non-glucose target detection. In this review, the recent advances from 2020 to 2024 in non-glucose target analysis for PGMs as POCT devices are summarized. The signal transduction strategies for non-glucose target analysis based on PGMs, including enzymatic transduction, nanocarrier transduction (enzyme or glucose), and glucose consumption transduction are briefly introduced. Meanwhile, the applications of PGMs in non-glucose target analysis are outlined, encompassing biomedical, environmental, and food analysis, along with other diverse applications. Finally, the prospects of and obstacles to employing PGMs as POCT tools for non-glucose target analysis are discussed.

Endogenous Glutathione-Activated Nucleic Acid Molecular Circuitry for Cell-Specific MicroRNA Imaging

Sensitive and reliable microRNA imaging in living cells has significant implications for clinical diagnosis and monitoring. Catalytic DNA circuits have emerged as potent tools for tracking these intracellular biomarkers and probing the corresponding biochemical processes. However, their utility is hindered by the low resistance to external interference, leading to undesired off-site activation and consequent signal leakage. Therefore, achieving the endogenous control of the DNA circuit's activation is preferable to the reliable target analysis in living cells. In this study, we attempted to address this challenge by engineering a simple yet effective endogenous glutathione (GSH)-regulated hybridization chain reaction (HCR) circuit for acquiring high-contrast miRNA imaging. Initially, the HCR hairpin reactants were blocked by the engineered disulfide-integrated DNA duplex, thus effectively passivating their sensing function. And the precaged HCR hairpin was liberated by the cell-specific GSH molecule, thus initiating the HCR system for selectively amplified detection of microRNA-21 (miR-21). This approach prevented unwanted signal leakage before exposure into target cells, thus ensuring robust miR-21 imaging with high accuracy and reliability in specific tumor cells. Moreover, the endogenously responsive HCR circuit established a link between the small regulatory factors and miRNA, thereby enhancing the signal gain. In summary, the endogenously activatable DNA circuit represents a versatile toolbox for robust bioanalysis and exploration of potential signaling pathways in living cells.

Construction of Multiply Guaranteed DNA Sensors for Biological Sensing and Bioimaging Applications

Nucleic acids exhibit exceptional functionalities for both molecular recognition and catalysis, along with the capability of predictable assembly through strand displacement reactions. The inherent programmability and addressability of DNA probes enable their precise, on-demand assembly and accurate execution of hybridization, significantly enhancing target detection capabilities. Decades of research in DNA nanotechnology have led to advances in the structural design of functional DNA probes, resulting in increasingly sensitive and robust DNA sensors. Moreover, increasing attention has been devoted to enhancing the accuracy and sensitivity of DNA-based biosensors by integrating multiple sensing procedures. In this review, we summarize various strategies aimed at enhancing the accuracy of DNA sensors. These strategies involve multiple guarantee procedures, utilizing dual signal output mechanisms, and implementing sequential regulation methods. Our goal is to provide new insights into the development of more accurate DNA sensors, ultimately facilitating their widespread application in clinical diagnostics and assessment.

Programmably engineered stochastic RNA nanowalker for ultrasensitive miRNA detection

A programmably engineered stochastic RNA nanowalker powered by duplex-specific nuclease (DSN) is developed. By utilizing poly-adenine-based spherical nucleic acids (polyA-SNA) to accurately regulate the densities of DNA tracks, the nanowalker showcases its capability to identify miRNA-21, miRNA-486, and miRNA-155 with quick kinetics and attomolar sensitivity, positioning it as a promising option for cancer clinical surveillance.

Multiply Guaranteed Catalytic DNA Circuit for Cancer-Cell-Selective Imaging of miRNA and Robust Evaluation of Drug Resistance

Catalytic DNA circuits are desirable for sensitive bioimaging in living cells; yet, it remains a challenge to monitor these intricate signal communications because of the uncontrolled circuitry leakage and insufficient cell selectivity. Herein, a simple yet powerful DNA-repairing enzyme (APE1) activation strategy is introduced to achieve the site-specific exposure of a catalytic DNA circuit for realizing the selectively amplified imaging of intracellular microRNA and robust evaluation of the APE1-involved drug resistance. Specifically, the circuitry reactants are firmly blocked by the enzyme recognition/cleavage site to prevent undesirable off-site circuitry leakage. The caged DNA circuit has no target-sensing activity until its circuitry components are activated via the enzyme-mediated structural reconstitution and finally transduces the amplified fluorescence signal within the miRNA stimulation. The designed DNA circuit demonstrates an enhanced signal-to-background ratio of miRNA assay as compared with the conventional DNA circuit and enables the cancer-cell-selective imaging of miRNA. In addition, it shows robust sensing performance in visualizing the APE1-mediated chemoresistance in living cells, which is anticipated to achieve in-depth clinical diagnosis and chemotherapy research.

Two-mode sensing strategies based on tunable cobalt metal organic framework active sites to detect Hg2

Heavy metal pollution poses a major threat to human health, and developing a user-deliverable heavy metal detection strategy remains a major challenge. In this work, two-mode Hg2+ sensing platforms based on the tunable cobalt metal-organic framework (Co-MOF) active site strategy are constructed, including a colorimetric, and an electrochemical assay using a personal glucose meter (PGM) as the terminal device. Specifically, thymine (T), a single, adaptable nucleotide, is chosen to replace typical T-rich DNA aptamers. The catalytic sites of Co-MOF are tuned competitively by the specific binding of T-Hg2+-T, and different signal output platforms are developed based on the different enzyme-like activities of Co-MOF. DFT calculations are utilized to analyze the interaction mechanism between T and Co-MOF with defect structure. Notably, the two-mode sensing platforms exhibit outstanding detection performance, with LOD values as low as 0.5 nM (colorimetric) and 3.69 nM (PGM), respectively, superior to recently reported nanozyme-based Hg2+ sensors. In real samples of tap water and lake water, this approach demonstrates an effective recovery rate and outstanding selectivity. Surprisingly, the method is potentially versatile and, by exchanging out T-Hg2+-T, can also detect Ag+. This simple, portable, and user-friendly Hg2+ detection approach shows plenty of promise for application in the future.

Point-of-Care Testing for the Detection of MicroRNAs: Towards Liquid Biopsy on a Chip

Point-of-care (PoC) testing is revolutionizing the healthcare sector improving patient care in daily hospital practice and allowing reaching even remote geographical areas. In the frame of cancer management, the design and validation of PoC enabling the non-invasive, rapid detection of cancer markers is urgently required to implement liquid biopsy in clinical practice. Therefore, focusing on stable blood-based markers with high-specificity, such as microRNAs, is of crucial importance. In this work, we highlight the potential impact of circulating microRNAs detection on cancer management and the crucial role of PoC testing devices, especially for low-income countries. A detailed discussion about the challenges that should be faced to promote the technological transfer and clinical use of these tools has been added, to provide the readers with a complete overview of potentialities and current limitations.

Robust nontarget DNA-triggered catalytic hairpin assembly amplification strategy for the improved sensing of microRNA in complex biological matrices

A simple but robust fluorescence strategy based on a nontarget DNA-triggered catalytic hairpin assembly (CHA) was constructed to probe microRNA-21 (miR-21). A short ssDNA rather than degradable target miRNA was employed as an initiator. Two molecular beacons needed to assist the CHA process were simplified to avoid unfavorable nonspecific interactions. In the presence of the target, the initiator was released from a partially duplex and triggered the cyclic CHA reaction, resulting in a significantly amplified optical readout. A wide linear range from 0.1 pM to 1000 pM for the sensing of miR-21 in buffer was achieved with a low detection limit of 0.76 pM. Fortunately, this strategy demonstrated an obviously improved performance for miR-21 detection in diluted serum. The fluorescence signals were enhanced remarkably and the sensitivity was further improved to 0.12 pM in 10% serum. The stability for miR-21 quantification and the capability for the analysis of single nucleotide polymorphisms (SNPs) were also improved greatly. More importantly, the biosensor could be applied to image miR-21 in different living tumor cells with high resolution, illustrating its promising potential for the assay of miRNAs in various complex situations for early-stage disease diagnosis and biological studies in cells.

3D DNAzyme walker based electrochemical biosensor for attomolar level microRNA-155 detection

Herein, an ultrasensitive electrochemical biosensor for microRNA-155 (miR-155) detection based on the powerful catalytic and continuous walking signal amplification capability of 3D DNAzyme walker and the gold nanoparticles/graphene aerogels carbon fiber paper-based (AuNPs/GAs/CFP) flexible sensing electrode with excellent electrochemical performance was successfully constructed. In a proof-of-concept experiment, in the presence of miR-155, the DNAzyme strands anchored on the streptavidin-modified magnetic beads (MBs) silenced by locked strands can be activated, thus generating the walking arm of the 3D DNAzyme walker. Meanwhile, the substrate strands modified with Fe-MOF-NH2 nanoparticles were evenly distributed on the surface of MBs and served as tracks of the 3D DNAzyme walker. Once the DNAzyme strand was activated, the catalytic site in the substrate strand can be cleaved in the presence of Mn2+, and a large number of stumps modified with Fe-MOF-NH2 nanoparticles (output@Fe-MOF-NH2) will be generated during the continuous and efficient walking cleavage of the DNAzyme walker, driving the recognition-catalysis-release cycle process for signal amplification. Immediately afterwards, the signal was read out through the base complementary pairing of capture probe (PS) immobilized on the surface of the paper-based flexible sensing electrode AuNPs/GAs/CFP and signal probes output@Fe-MOF-NH2, thus achieving the quantitative detection of miR-155. Under optimal experimental conditions, the designed 3D DNAzyme walker-based biosensor exhibited a relatively lower limit of detection (LOD) of 56.23 aM, with a linear range of 100 aM to 100 nM. Overall, the proposed 3D DNAzyme walker biosensor exhibited good interference and reproducibility, demonstrating a promising future in the field of clinical disease diagnosis.

Integration of Isothermal Enzyme-Free Nucleic Acid Circuits for High-Performance Biosensing Applications

The isothermal enzyme-free nucleic acid amplification method plays an indispensable role in biosensing by virtue of its simple, robust, and highly efficient properties without the assistance of temperature cycling or/and enzymatic biocatalysis. Up to now, enzyme-free nucleic acid amplification has been extensively utilized for biological assays and has achieved the highly sensitive detection of various biological targets, including DNAs, RNAs, small molecules, proteins, and even cells. In this Review, the mechanisms of entropy-driven reaction, hybridization chain reaction, catalytic hairpin assembly and DNAzyme are concisely described and their recent application as biosensors is comprehensively summarized. Furthermore, the current problems and the developments of these DNA circuits are also discussed.