CRISPR‐dCas9 systems that are precisely activated by cell‐specific information facilitate the development of smart sensors or therapeutic strategies. We report the development of an activatable dCas9 ...transcriptional circuit that enables sensing and silencing of mRNA in living cells using hybridization‐mediated structure switching for gRNA activation. The gRNA is designed with the spacer sequence blocked by a hairpin structure, and mRNA hybridization induces gRNA structure switching and activates the transcription of reporter RNA. An mRNA sensor developed using a light‐up RNA reporter shows high sensitivity and fast‐response imaging of survivin mRNA in cells under drug treatments and different cell lines. Furthermore, a feedback circuit is engineered by incorporating a small hairpin RNA in the reporter RNA, demonstrating a smart strategy for dynamic sensing and silencing of survivin with induced tumor cell apoptosis. This circuit illustrates a broadly applicable platform for the development of cell‐specific sensing and therapeutic strategies.
An activatable dCas9 transcriptional circuit is designed utilizing the strategy of hybridization‐mediated structure switching for gRNA activation. The designed circuit enables sensing and silencing of mRNA in living cells.
DNA nanowalkers moving progressively along a prescribed DNA track are useful tools in biosensing, molecular theranostics and biosynthesis. However, stochastic DNA nanowalkers that can perform in ...living cells have been largely unexplored. We report the development of a novel stochastic bipedal DNA walker that, for the first time, realizes direct intracellular base excision repair (BER) fluorescence activation imaging. In our design, the bipedal walker DNA was generated by BER-related human apurinic/apyrimidinic endonuclease 1 (APE1)-mediated cleavage of DNA sequences at an abasic site in the intracellular environment, and it autonomously travelled on spherical nucleic acid (SNA) surfaces
via
catalyzed hairpin assembly (CHA). Our nanomachine outperforms the conventional single leg-based DNA walker with an improved sensitivity, kinetics and walking steps. Moreover, in contrast to the single leg-based DNA walker, the bipedal DNA walker is capable of monitoring the fluorescence signal of reduced APE1 activity, thus indicating amplified intracellular imaging. This bipedal DNA-propelled DNA walker presents a simple and modular amplification mechanism for intracellular biomarkers of interest, providing an invaluable platform for low-abundance biomarker discovery leading to the accurate identification and effective treatment of cancers.
The developed DNA bipedal walker represents improved sensitivity, kinetics and walking steps for intracellular fluorescence imaging of base-excision repairing.
Blood glucose monitoring has attracted extensive attention because diabetes mellitus is a worldwide public health problem. Here, we reported an upconversion fluorescence detection method based on ...manganese dioxide (MnO2)-nanosheet-modified upconversion nanoparticles (UCNPs) for rapid, sensitive detection of glucose levels in human serum and whole blood. In this strategy, MnO2 nanosheets on the UCNP surface serve as a quencher. UCNP fluorescence can make a recovery by the addition of H2O2, which can reduce MnO2 to Mn2+, and the glucose can thus be monitored based on the enzymatic conversion of glucose by glucose oxidase to generate H2O2. Because of the nonautofluorescent assays offered by UCNPs, the developed method has been applied to monitor glucose levels in human serum and whole blood samples with satisfactory results. The proposed approach holds great potential for diabetes mellitus research and clinical diagnosis. Meanwhile, this nanosystem is also generalizable and can be easily expanded to the detection of various H2O2-involved analytes.
This review discusses the recent advances in both theories and analytical applications of multi-way calibrations based on various high-order analytical data. In the theory part, we focus on some ...aspects of multi-way calibration, such as multilinear models and their extensions, multi-way calibration algorithms with second-order or higher-order advantages, and other fundamental issues. According to different types of high-order instrument signals, recent applications of second-, third-, and fourth-order calibrations are then discussed, and their contributions to green analytical chemistry are highlighted.
•The theories and applications of multi-way calibration have been systematically introduced.•The theory part focused on multilinear models, algorithms and some fundamental issues.•Different high-order instrumental data acquisition procedures have been described.•Representative applications published from 2015 to 2020 have been reviewed.•The advantages and contributions of multi-way calibration methods have been emphasized.
DNAzymes, screened through in vitro selection, have shown great promise as molecular tools in the design of biosensors and nanodevices. The catalytic activities of DNAzymes depend specifically on ...cofactors and show multiple enzymatic turnover properties, which make DNAzymes both versatile recognition elements and outstanding signal amplifiers. Combining nanomaterials with unique optical, magnetic and electronic properties, DNAzymes may yield novel fluorescent, colorimetric, surface-enhanced Raman scattering (SERS), electrochemical and chemiluminescent biosensors. Moreover, some DNAzymes have been utilized as functional components to perform arithmetic operations or as "walkers" to move along DNA tracks. DNAzymes can also function as promising therapeutics, when designed to complement target mRNAs or viral RNAs, and consequently lead to down-regulation of protein expression. This feature article focuses on the most significant achievements in using DNAzymes as recognition elements and signal amplifiers for biosensors, and highlights the applications of DNAzymes in logic gates, DNA walkers and nanotherapeutics.
Formaldehyde (FA), as a reactive carbonyl species, is endogenously generated in various biological processes. Abnormal levels of FA could lead to various cellular dysfunction and pathological ...conditions. Here, we develop a new activatable fluorescent probe for highly selective visualization of FA in living cells. Our probe (Naph-1) is designed using a naphthalene derivative as the fluorophore and hydrazone as a recognition site for FA. Naph-1 is essentially nonemissive. After reacting with FA, the amine moiety is converted into a Schiff base with electron-withdrawing ability and the fluorescence is simultaneously turned on due to synergetic intramolecular charge transfer and favoured excited state intramolecular proton transfer effects. Naph-1 exhibits a large Stokes shift upon reaction with FA. Furthermore, it possesses high selectivity and superior sensitivity toward FA with an estimated limit of detection of 0.35 μM. Moreover, Naph-1 is also successfully applied to image both endogenous and exogenous formaldehyde in living cells. These features demonstrate that Naph-1 holds great potential in the detection and imaging of formaldehyde in biological systems.
A surface-enhanced Raman spectroscopy (SERS) based method was developed for the quantification of Cd2+ in rice. Gold nano-particles (AuNPs) modified with trimercaptotriazine served as a ratiometric ...SERS probe for the detection of Cd2+. A conical holed substrate was used to further enhance SERS signals, and hence to improve the sensitivity. A calibration model based on the spectral shape deformation quantitative theory was employed to mitigate the influence of variations in the number and distribution of “hot spots”. The proposed SERS method was applied to quantitative analysis of Cd2+ in three types of rice, and achieved satisfactory quantitative results with accuracy comparable to that of the reference method—inductively coupled plasma mass spectrometry. The limit of detection of the proposed method was estimated to be 8 μg kg−1. The proposed SERS method has the potential to become a fast screening method for the detection of Cd2+ in rice.
Filter‐based particle samples were simultaneously collected at 14 sites across 6 regions of China during the summer of 2012. These filters were analyzed for secondary organic aerosol (SOA) tracers ...from biogenic precursors (isoprene, monoterpenes, and β‐caryophyllene) and anthropogenic aromatics. The sum of all SOA tracers ranged from 29.9 to 371 ng m−3 with the majority from isoprene (123 ± 78.8 ng m−3), followed by monoterpenes (10.5 ± 6.64 ng m−3), β‐caryophyllene (5.07 ± 3.99 ng m−3), and aromatics (2.90 ± 1.52 ng m−3). The highest levels of biogenic SOA tracers were observed in East China, whereas the highest concentrations of the aromatic SOA tracer, 2,3‐dihydroxy‐4‐oxopentanoic acid (DHOPA), occurred in North China. All biogenic SOA tracers exhibited positive correlations with temperature, most likely resulting from enhanced biogenic volatile organic compounds (BVOCs) emissions and photochemistry in high‐temperature regions. Among the isoprene SOA tracers, the low‐NOx products 2‐methyltetrols were the largest by mass concentration. However, at certain urban sites, the contribution of the high‐NOx product 2‐methylglyceric acid was significantly higher, implying a greater influence of NOx on isoprene SOA formation in urban areas. For the monoterpene SOA tracers, the ratio of the first‐generation products (cis‐pinonic acid plus pinic acid) to the high‐generation product (3‐methyl‐1,2,3‐butanetricarboxylic acid) exhibited a negative correlation with the amount of high‐generation products, indicating that this ratio could serve as an indicator of the aging of monoterpene SOA. The ratio ranged from 0.89 to 21.0, with an average of 7.00 ± 6.02, among the observation sites, suggesting that monoterpene SOA was generally fresh over China during the summer. As a typical anthropogenic SOA tracer, DHOPA exhibited higher levels at urban sites than at remote sites. These SOA tracers were further used to attribute SOA origins via the SOA‐tracer method. The total concentrations of secondary organic carbon (SOC) and SOA were estimated to be in the range of 0.37 to 2.47 μgC m−3 and 0.81 to 5.44 µg m−3, respectively, with the highest levels observed in the eastern regions of China. Isoprene (46 ± 14%) and aromatics (27 ± 8%) were the two major contributors to SOC in every region. In North China, aromatics were the largest SOA contributor. Our ground‐based observations suggest that anthropogenic aromatics are important SOA precursors in China.
Key Points
BSOA tracers highest in East China; aromatics tracer highest in North ChinaSOA exhibits higher level in the eastern regions of ChinaIsoprene and aromatics are major precursors of SOA over China during summer
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