The quality and application of super-resolution fluorescence imaging greatly lie in the dyes' properties, including photostability, brightness, and Stokes shift. Here we report a synergistic strategy ...to simultaneously improve such properties of regular fluorophores. Introduction of quinoxaline motif with fine-tuned electron density to conventional rhodamines generates new dyes with vibration structure and inhibited twisted-intramolecular-charge-transfer (TICT) formation synchronously, thus increasing the brightness and photostability while enlarging Stokes shift. The new fluorophore YL578 exhibits around twofold greater brightness and Stokes shift than its parental fluorophore, Rhodamine B. Importantly, in Stimulated Emission Depletion (STED) microscopy, YL578 derived probe possesses a superior photostability and thus renders threefold more frames than carbopyronine based probes (CPY-Halo and 580CP-Halo), known as photostable fluorophores for STED imaging. Furthermore, the strategy is well generalized to offer a new class of bright and photostable fluorescent probes with long Stokes shift (up to 136 nm) for bioimaging and biosensing.
Two-dimensional graphitic carbon nitride nanosheets (CNNSs) with planar graphene-like structure have stimulated increasingly research interest in recent years due to their unique physicochemical ...properties. CNNSs possess superior stability, high fluorescence quantum yield, low-toxicity, excellent biocompatibility, unique electroluminescent and photoelectrochemical properties, which make them appropriate candidates for biosensing. In this review, we first introduce the preparation and unique properties of CNNSs, with emphasis on their superior properties for biosensing. Then, recent advances of CNNSs in photoelectrochemical biosensing, electrochemiluminescence biosensing and fluorescence biosensing are highlighted. An additional attention is paid to the marriage of CNNSs and nucleic acids, which exhibits great potentials in both biosensing and intracellular imaging. Finally, current challenges and opportunities of this 2D material are outlined. Inspired by the unique properties of CNNSs and their advantages in biological applications, we expect that more attention will be drawn to this promising 2D material and extensive applications can be found in bioanalysis and diseases diagnosis.
•Advance of two-dimensional graphitic carbon nitride nanosheets (CNNSs) was present.•The deep research on CNNSs offers valuable strategies for biosensing applications.•Properties of CNNSs and their applications in biosensing were discussed in detail.•Deficiencies and perspectives about the applications of CNNSs were summarized.
Aptamer-based sensors have emerged as a major platform for detecting small-molecular targets, because aptamers can be selected to bind these small molecules with higher affinity and selectivity than ...other receptors such as antibodies. However, portable, accurate, sensitive, and affordable detection of these targets remains a challenge. In this work, we developed an aptasensing platform incorporating magnetic beads and a DNAzyme for signal amplification, resulting in high sensitivity. The biosensing platform was constructed by conjugating a biotin-labeled aptamer probe of small-molecular targets such as toxins and a biotin-labeled substrate strand on magnetic beads, and the DNAzyme strand hybridized with the aptamer probe to block the substrate cleavage activity. The specific binding of the small-molecular target by the aptamer probe can replace the DNAzyme strand and then induce the hybridization between the DNAzyme strand and substrate strand, and the iterative signal amplification reaction of hydrolysis and cleavage of the substrate chain occurs in the presence of a metal ion cofactor. Using invertase to label the substrate strand, the detection of small molecules of the toxin is successfully transformed into the measurement of glucose, and the sensitive analysis of small molecules such as toxins can be realized by using the household portable glucose meter as a readout. This platform is shown to detect ochratoxin, a common toxin in food, with a linear detection range of 5 orders of magnitude, a low detection limit of 0.88 pg/mL, and good selectivity. The platform is easy to operate and can be used as a potential choice for quantitative analysis of small molecules, at home or under point-of-care settings. Moreover, by changing and designing the aptamer probe and the arm of DNAzyme strand, it can be used for the analysis of other analytes.
Many different metal ions are involved in various biological functions including metallomics and trafficking, and yet there are currently effective sensors for only a few metal ions, despite the ...first report of metal sensors for calcium more than 40 years ago. To expand upon the number of metal ions that can be probed in biological systems, we and other laboratories employ the in vitro selection method to obtain metal-specific DNAzymes with high specificity for a metal ion and then convert these DNAzymes into fluorescent sensors for these metal ions using a catalytic beacon approach. In this Forum Article, we summarize recent progress made in developing these DNAzyme sensors to probe metal ions in living cells and in vivo, including several challenges that we were able to overcome for this application, such as DNAzyme delivery, spatiotemporal control, and signal amplification. Furthermore, we have identified a key remaining challenge for the quantitative detection of metal ions in living cells and present a new design and the results of a Förster resonance energy transfer (FRET)-based DNAzyme sensor for the ratiometric quantification of Zn2+ in HeLa cells. By converting existing DNAzyme sensors into a ratiometric readout without compromising the fundamental catalytic function of the DNAzymes, this FRET-based ratiometric DNAzyme design can readily be applied to other DNAzyme sensors as a major advance in the field to develop much more quantitative metal-ion probes for biological systems.
Filamentous fungi are abundant resources of bioactive natural products. Here, 151 marine-derived fungi were collected from the north Yellow Sea and identified by an internal transcribed spacer (ITS) ...sequence. The crude extracts of all strains were evaluated for their antimicrobial activities and analyzed by HPLC fingerprint. Based on these, strain Penicillium oxalicum MEFC104 was selected for further investigation. Two new polyketide–amino acid hybrid compounds with feature structures of tetramic acid, oxopyrrolidine A and B, were isolated. Their planner structures were assigned by HRESIMS and 1D/2D NMR experiments. The absolute configurations were determined by modified Mosher’s method, J-based configuration analysis, and ECD calculations. Furthermore, the biosynthetic pathway was identified by bioinformatic analysis and gene-deletion experiments. This study established a link between oxopyrrolidines and the corresponding biosynthesis genes in P. oxalicum.
Molecular subtyping of cancer can greatly help to understand the development of disease and predict tumor behavior. Exploring detection methods for precise subtyping is appealing to prognosis and ...personalized therapy. During the past decades, DNA‐based biosensors have exhibited great potential in cancer diagnosis due to their structural programmability and functional diversity. Despite the encouraging progress that has been made, there remains an issue in improving the accuracy and sensitivity of cancer subtyping due to the complex process of disease, especially in preclinical or clinical applications. To accelerate the development of DNA sensors in the identification of cancer subtypes, in this review, we summarized their advances in molecular subtyping by analyzing the heterogeneity in categories and levels of biomarkers between cancer subtypes. The strategies toward genomic and proteomic heterogeneity in cells or on the cell surface, as well as the cancer excretions including extracellular vesicles (EVs) and microRNA (miRNAs) in serum, are summarized. Current challenges and the opportunities of DNA‐based sensors in this field are also discussed.
Molecular subtyping of cancer is crucial for understanding the development of disease and predicting tumor behavior. This review focuses on the advanced strategies of molecular subtyping using DNA‐based biosensors for the identification of cancer subtypes based on different biomarkers, including cells, extracellular vesicles (EVs), and microRNAs (miRNAs) in serum.
Nucleic acid biosensors, integrated with functional nucleic acids, have drawn extensive attention for diverse biomedical applications. In particular, many nucleic acid probes have been developed for ...biosensing and imaging of tumor‐associated species, including pH, small molecules, RNAs, metal ions, proteins, and cells. Despite the progress made, these sensors are mainly performed at the level of test tube assays or live cells for disease diagnosis and pathological studies. In recent years, increasing research works are pushing the limit of nucleic acid sensors in preclinical applications and imaging‐guided therapy. However, the applicability of current nucleic acid sensors in vivo is largely hindered by the complexity of living animals. Herein, we review recent advances in the design and applications of nucleic acid biosensors in vivo, in which the key factors for the fabrication of eligible sensors are highlighted. Additionally, given the inherent shortcomings of nucleic acid, we will also describe the challenges of the current in vivo nucleic acid biosensors and some new strategies that may significantly accelerate the development of biosensors.
Recent years have witnessed the increasing research works of nucleic acid sensors in vivo, however, which is still hindered by the complexity of living animals. Therefore, we review recent advances in the design and applications of nucleic acid biosensors in vivo to accelerate their development of the sensors.
While fluorescent sensors have been developed for monitoring metal ions in health and diseases, they are limited by the requirement of an excitation light source that can lead to photobleaching and a ...high autofluorescence background. To address these issues, bioluminescence resonance energy transfer (BRET)-based protein or small molecule sensors have been developed; however, most of them are not highly selective nor generalizable to different metal ions. Taking advantage of the high selectivity and generalizability of DNAzymes, we report herein DNAzyme-based ratiometric sensors for Zn2+ based on BRET. The 8-17 DNAzyme was labeled with luciferase and Cy3. The proximity between luciferase and Cy3 permitted BRET when coelenterazine, the substrate for luciferase, was introduced. Adding samples containing Zn2+ resulted in a cleavage of the substrate strand, causing dehybridization of the DNAzyme construct, thus increasing the distance between Cy3 and luciferase and changing the BRET signals. Using these sensors, we detected Zn2+ in serum samples and achieved Zn2+ detection with a smartphone camera. Moreover, since the BRET pair is not the component that determines the selectivity of the sensors, this sensing platform has the potential to be adapted for the detection of other metal ions with other metal-dependent DNAzymes.
In situ monitoring of the location and transportation of bioactive molecules is essential for deciphering diverse biological events in the field of biomedicine. In addition, obtaining the in situ ...information of lesions will provide a clear perspective for surgeons to perform precise resection in clinical surgery. Notably, delivering drugs or operating photodynamic therapy/photothermal therapy in situ by labeling the lesion regions of interest can improve treatment and reduce side effects in vivo . In various advanced imaging and therapy modalities, optical theranostic agents based on organic small molecules can be conveniently modified as needed and can be easily internalized into cells/lesions in a non-invasive manner, which are prerequisites for in situ bioimaging and precision treatment. In this tutorial review, we first summarize the in situ molecular immobilization strategies to retain small-molecule agents inside cells/lesions to prevent their diffusion in living organisms. Emphasis will be focused on introducing the application of these strategies for in situ imaging of biomolecules and precision treatment, particularly pertaining to why targeting therapy in situ is required.
Ligand-functionalized plasmonic nanoparticles have been widely used for targeted imaging in living systems. However, ligand presentation and encoding on the nanoparticle’s surface in a ...stoichiometrically controllable manner remains a great challenge. Herein, we propose a method to construct ligand-engineered plasmonic nanoprobes by using nanoparticle encapsulation with topological DNA tetrahedrons, which enables the programmed ligand loading for precise regulation of targeting efficiency of nanoprobes in biorelated applications. With this method, we demonstrated the preparation of functionalized plasmonic nanoprobes by programmed loading of RGD peptides and aptamers onto the DNA tetrahedron encapsulated gold nanoparticles with controllable stoichiometric ratios. The cell imaging and particle counting assays suggested that the targeting efficiency of the nanoprobes could be readily modulated by tailoring the number and stoichiometric ratios of the loaded ligands, respectively. It can be anticipated that this robust strategy could provide new opportunities for the construction of efficacious nanoprobes and delivery systems for versatile bioapplications.
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