Lysosome-targeted ratiometric fluorescent sensor for monitoring pH in living cells based on one-pot-synthesized carbon dots

Macrophage targeted graphene oxide nanosystem synergize antibiotic killing and host immune defense for Tuberculosis Therapy

Tuberculosis (TB), a deadly disease caused by Mycobacterium tuberculosis (Mtb) infection, remains one of the top killers among infectious diseases worldwide. How to increase targeting effects of current anti-TB chemotherapeutics and enhance anti-TB immunological responses remains a big challenge in TB and drug-resistant TB treatment. Here, mannose functionalized and polyetherimide protected graphene oxide system (GO-PEI-MAN) was designed for macrophage-targeted antibiotic (rifampicin) and autophagy inducer (carbamazepine) delivery to achieve more effective Mtb killings by combining targeted drug killing and host immunological clearance. GO-PEI-MAN system demonstrated selective uptake by in vitro macrophages and ex vivo macrophages from macaques. The endocytosed GO-PEI-MAN system would be transported into lysosomes, where the drug loaded Rif@Car@GO-PEI-MAN system would undergo accelerated drug release in acidic lysosomal conditions. Rif@Car@GO-PEI-MAN could significantly promote autophagy and apoptosis in Mtb infected macrophages, as well as induce anti-bacterial M1 polarization of Mtb infected macrophages to increase anti-bacterial IFN-γ and nitric oxide production. Collectively, Rif@Car@GO-PEI-MAN demonstrated effectively enhanced intracellular Mtb killing effects than rifampicin, carbamazepine or GO-PEI-MAN alone in Mtb infected macrophages, and could significantly reduce mycobacterial burdens in the lung of infected mice with alleviated pathology and inflammation without systemic toxicity. This macrophage targeted nanosystem synergizing increased drug killing efficiency and enhanced host immunological defense may be served as more effective therapeutics against TB and drug-resistant TB.

Tumor diagnosis using carbon-based quantum dots: Detection based on the hallmarks of cancer

Carbon-based quantum dots (CQDs) have been shown to have promising application value in tumor diagnosis. Their use, however, is severely hindered by the complicated nature of the nanostructures in the CQDs. Furthermore, it seems impossible to formulate the mechanisms involved using the inadequate theoretical frameworks that are currently available for CQDs. In this review, we re-consider the structure-property relationships of CQDs and summarize the current state of development of CQDs-based tumor diagnosis based on biological theories that are fully developed. The advantages and deficiencies of recent research on CQDs-based tumor diagnosis are thus explained in terms of the manifestation of nine essential changes in cell physiology. This review makes significant progress in addressing related problems encountered with other nanomaterials.

Wavelength-Tuneable Fluorescent Carbon Dots for Nucleic Acid Imaging

Nucleic acid is one of the most important substances in organisms, and its dynamic changes are closely related to physiological processes. Nucleic acid labeling is conducive to providing important information for the early diagnosis and treatment of pathophysiological processes. Here, we utilized the transfer mechanism between carbon sources and CDs to synthesize wavelength-adjustable N-CDs for the nucleic acid image. Along with the increased graphite nitrogen (from 10.6 to 30.1%) gradually by the precise design of the nitrogen structure in carbon sources (e.g., primary amines, secondary amines, tertiary amines, and liking graphite-nitrogen), the energy gap of CDs reduced, resulting in adjustable wavelength from visible to near-infrared range (from 461 nm/527 nm to 650 nm/676 nm). Furthermore, N-CDs exhibited a selective affinity for nucleic acids, especially RNA. Therefore, N-CDs support an efficient platform for real-time tracking of RNA dynamic changes in cells.

Effective Combination of Targeted Therapies with Sonodynamic Treatment for Use in Exploring Differences in Therapeutic Efficacy across Organelle Targets

Acoustic kinetic therapy systems that target specific organelles can improve the precision of a sonosensitizer, which is a perfect combination of targeted therapy and sonodynamic therapy (SDT) and plays an important role in current acoustic kinetic therapy. In this study, we loaded PpIX, a sonosensitizer, on targeted-functional carbon dots (CDs) via an amide reaction and then generated the mitochondria-targeted system (Mit-CDs-PpIX) and nucleus-targeted system (Nuc-CDs-PpIX), respectively, to deliver the sonosensitizer. Both systems exhibited minimal cytotoxicity in the absence of ultrasound stimulation. The efficacy of the targeted SDT systems was investigated using methylthiazol tetrazolium (MTT) assays, live/dead staining, flow cytometry, etc. Compared with the free PpIX and mitochondria-targeted system, the nucleus-targeted system is more potent in killing effect under ultrasound stimulation and induces apoptosis with higher intensity. To achieve the equal killing effect, the effective concentration of Nuc-CDs-PpIX is just one third of that of Mit-CDs-PpIX.

Recent advances in the design of intracellular pH sensing nanoprobes based on organic and inorganic materials

In the biological system, the intracellular pH (pHi) plays an important role in regulating diverse physiological activities, including enzymatic action, ion transport, cell proliferation, metabolism, and programmed cell death. The monitoring of pH inside living cells is also crucial for studying cellular events such as phagocytosis, endocytosis, and receptor-ligand internalization. Furthermore, some organelles, viz., endosomes and lysosomes, have intracompartmental pH, which is critical for maintaining the stability of protein structure and function. The dysfunction and abnormal pH regulation can result in terminal diseases such as cancer, Alzheimer, and so forth. Therefore, the accuracy of intracellular pH measurement is always the top priority and demands cutting-edge research and analysis. Such techniques, such as Raman spectroscopy and fluorescence imaging, preferably use nanotechnology due to their remarkable advantages, such as a non-invasive approach and providing accuracy, repeatability, and reproducibility. In the past decades, there have been numerous attempts to design and construct non-invasive organic and inorganic materials-based nanoprobes for pHi sensing. For Raman-based techniques, metal nanostructures such as Au/Ag/Cu nanoparticles are utilized to enhance the signal intensity. As for the fluorescence-based studies, the organic-based small molecules, such as dyes, show higher sensitivity toward pH. However, they possess several drawbacks, including high photobleaching rate, and autofluorescence background signals. To this end, there are alternative nanomaterials proposed, including semiconductor quantum dots (QDs), carbon QDs, upconversion nanoparticles, and so forth. Moreover, the fluorescence technique allows for ratiometric measurement of pHi, which as a result, offers a reliable calibration curve. This timely review will critically examine the current progression in the existing nanoprobes. In addition, based on our knowledge and available research findings, we provide a brief future outlook that may advance the state-of-the-art methodologies for pHi sensing.

Organic acid-induced triple fluorescent emission carbon quantum dots identification of distilled liquor

An acid-sensitive carbon dot fluorescence sensing array was investigated for the differentiated recognition of distilled spirits. Due to the electrostatic interactions between CDs and organic acids, organic acids affect the protonation and fluorescence properties of CDs, which in turn modify the CDs triple fluorescence emission. The regular linear variation of the fluorescence sensor was found under acidic conditions (3.0 < pH < 6.2). A comprehensive study of acids with selectivity, different concentrations (0.1 mM, 1 mM, 10 mM, 40 mM), different types (8 species) and mixed acids (formic acid and acetic acid), and good quantification capability for acetic acid (0.01-1 mM). Demonstrating good recognition ability of the sensor array for complex analyte. On this basis, the fluorescence sensor array was applied to the classification and recognition of liquors. LDA has realized the identification of 16 kinds of Baijiu and 21 kinds of distilled liquors with an accuracy of 100%.

Ratiometric Sensing of Intracellular pH Based on Dual Emissive Carbon Dots

Accurate monitoring of intracellular pH in living cells is critical for developing a better understanding of cellular activities. In the current study, label-free carbon dots (p-CDs), which were fabricated using a straightforward one-pot solvothermal treatment of p-phenylenediamine and urea, were employed to create a new ratiometric pH nanosensor. Under single-wavelength excitation (λ_ex = 500 nm), the p-CDs gave dual emission bands at 525 and 623 nm. The fluorescent intensity ratio (I₅₂₅/I₆₂₃) was linearly related to pH over the range 4.0 to 8.8 in buffer solutions, indicating that the ratiometric fluorescence nanoprobe may be useful for pH sensing. In pH measurements, the p-CDs also demonstrated outstanding selectivity, reversibility, and photostability. Owing to the advantages outlined above, the nanoprobe was used to monitor the pH of HeLa cells effectively. The label-free CD-based ratiometric nanoprobe features comparatively easy manufacturing and longer excitation and emission wavelengths than the majority of previously reported CD-based ratiometric pH sensors, which is ultimately beneficial for applications in biological imaging.

A novel aggregation-induced emission fluorescent probe with large Stokes shift for sensitive detection of pH changes in live cells

The detection of intracellular pH is crucial for elucidating the pathological process of cancers, as well as for medical diagnostic applications. Here, we developed an aggregation-induced emission active pH-responsive fluorescent probe (TPE-DCP) for sensitively detecting cell pH changes. The probe shows obvious pH-sensing properties at ~615 nm, with a pKa value of 6.82 and a good linear pH response ranging from 8.5 to 4.5. TPE-DCP holds advantages such as excellent anti-interference performance, good photostability, and low cytotoxicity, and has been successfully used to image intracellular pH changes in cells.

Carbon quantum dots with blue/near infrared emissions for ratiometric fluorescent lornoxicam sensing and bio-imaging

An economical and eco-friendly hydrothermal method for the preparation of nitrogen-doped carbon quantum dots (N-CQDs) was studied with rambutan peel and lysine. The morphology, structure, and optical properties of N-CQDs were characterized by transmission electron microscopy, Fourier transform infrared spectrometry, X-ray powder diffractometer, X-ray photoelectron spectrometry, and UV spectrophotometry. The synthesized N-CQDs have excellent characteristics such as strong fluorescence, good dispersion, high stability, and excellent water solubility. The absolute fluorescence quantum yield is 1.02%, the average particle size is 1.63 nm, and the maximum excitation wavelength is 340 nm. The maximum emission wavelengths are 430 nm and 800 nm. As a quencher, lornoxicam (LNX) was used to quench the fluorescence of N-CQDs with the mechanism of inner filter effect. The fluorescence ratio of N-CQDs (F₄₃₀/F₈₀₀) shows a good linear relationship to the concentration of LNX. The linear range and the detection limit of LNX are 0.01‒100 and 0.003 μmol/L, respectively. An effective ratiometric fluorescence probe for the detection of LNX was constructed. The method has the advantages of low detection limit, high sensitivity, wide linear range, and can be applied to the determination of LNX in real samples. Moreover, according to the excitation-dependent fluorescence behavior, dual-wavelength emission, and biocompatibility of N-CQDs, it has been applied to cell imaging.

Zwitterion-Based Hydrogen Sulfide Nanomotors Induce Multiple Acidosis in Tumor Cells by Destroying Tumor Metabolic Symbiosis

Destruction of tumor metabolism symbiosis is an attractive cancer treatment method which targets tumor cells with little harm to normal cells. Yet, a single intervention strategy and poor penetration of the drug in tumor tissue result in limited effect. Herein, we propose a zero-waste zwitterion-based hydrogen sulfide (H2 S)-driven nanomotor based on the basic principle of reaction in human body. When loaded with monocarboxylic acid transporter inhibitor α-cyano-4-hydroxycinnamic acid (α-CHCA), the nanomotor can move in tumor microenvironment and induce multiple acidosis of tumor cells and inhibit tumor growth through the synergistic effect of motion effect, driving force H2 S and α-CHCA. Given the good biosafety of the substrate and driving gas of this kind of nanomotor, as well as the limited variety of nanomotors currently available to move in the tumor microenvironment, this kind of nanomotor may provide a competitive candidate for the active drug delivery system of cancer treatment.

Hg2+ detection, pH sensing and cell imaging based on bright blue-fluorescent N-doped carbon dots

A multifunctional sensing platform based on bright blue-fluorescent nitrogen-doped carbon dots (N-CDs) has been ingeniously designed for the sensitive determination of Hg²⁺ and pH.