Search Results (130)

Developing appropriate methods for real-time in situ investigation of how drugs influence signaling pathways and related biomolecules holds enormous potential for helping to provide an understanding of how anticancer drugs exert their effects. Herein, we report a smart nanoprobe, PDA-MB (DOX)-Pep, constructed on the basis of polydopamine nanoparticles (PDA NPs) modified with a dense shell of molecular beacon (MB) with embedded doxorubicin (DOX) and peptide, which can respond specifically to miRNA-34a and Caspase-3 targets. Intracellular experiments demonstrated that, in comparison to the control nanoprobe PDA-MB-Pep, the smart nanoprobe could selectively respond to miRNA-34a, facilitating the release of the embedded DOX. The released DOX subsequently activated the p53 pathway, which further upregulated miRNA-34a expression, leading to additional DOX release. This initiated a cyclical process involving the probe’s response to miRNA-34a, DOX release, p53 activation, and miRNA-34a upregulation, ultimately enhancing cell apoptosis and increasing Caspase-3 expression. The designed smart nanoprobe offers a visual approach to explore how anticancer drugs influence signaling pathways and related molecules at the cellular level. Full article

Nanoquenchers with a single quenching cofactor exhibit limited fluorescence quenching efficiency. In this work, a metal–organic hybrid with dual quenching cofactors (Cu²⁺ and pyrroloquinoline quinone or PQQ) was prepared by metal-coordinated assembly and used as a nanoquencher for a protease assay with enhanced quenching efficiency. The peptide substrate with an oligohistidine (His₆) tag was labeled with a fluorophore. Caspase-3 was determined as a protease example. The substrate was attached onto the surface of the Cu-PQQ nanoquencher by a metal coordination interaction between the unsaturated Cu²⁺ on the nanoparticle surface and the His₆ tag in the peptide. The cleavage of the peptide substrate by enzymatic hydrolysis led to the release of a fluorophore-conjugated segment from the nanoquencher surface, thus turning on the fluorescence. The nanoprobe was used to determine caspase-3 with a linear range of 0.01–5 ng/mL and a detection limit of 7 pg/mL. Furthermore, the method was used to evaluate inhibition efficiency and monitor drug-induced cell apoptosis. In contrast to other means of peptide immobilization, such as physical adsorption and covalent coupling, the strategy based on the metal coordination interaction is simple and powerful, thereby achieving assays of caspase-3 activity in lysates with a satisfactory result. The work should be valuable for the design of nanoquenchers with multiple quenching cofactors and the development of novel biosensors. Full article

In this study, we developed a multifunctional graphene oxide (GO)-based nanoprobe co-loaded with antisense peptide nucleic acid (PNA) and the chemotherapeutic agent doxorubicin (DOX). The nanoplatform was strategically functionalized with folic acid ligands to enable folate receptor-mediated tumor targeting. Upon cellular internalization, the antisense PNA component selectively hybridized with human telomerase reverse transcriptase (hTERT) mRNA through sequence-specific recognition, inducing structural detachment from the GO surface. This displacement restored the fluorescence signal of previously quenched fluorophores conjugated to the PNA strand, thereby enabling the real-time in situ detection and quantitative fluorescence imaging of intracellular hTERT mRNA dynamics. The antisense PNA component effectively reduced the hTERT mRNA level and downregulated telomerase activity via an antisense gene regulation pathway, while the pH-responsive release of DOX induced potent cancer cell apoptosis through chemotherapeutic action. This combinatorial therapeutic strategy demonstrated enhanced anticancer efficacy compared to single-modality treatments, achieving a 60% apoptosis induction in HeLa cells through coordinated gene silencing and chemotherapy. This study establishes GO as a promising dual-drug nanocarrier platform for developing next-generation theranostic systems that integrate molecular diagnostics with multimodal cancer therapy. Full article

In this paper, we present a simple solvothermal method to synthesize highly fluorescent metal-free elemental selenium quantum dots (SeQDs) using cost-effective bulk selenium powder. The SeQDs exhibit a small and uniform size, excellent aqueous dispersibility, a high photoluminescence quantum yield (PLQY) of 19.3% with stable fluorescence, and scalable production with a 7.2% yield. Owing to the inner filter effect (IFE), these SeQDs function as a highly effective nanoprobe for Cr(VI) detection, exhibiting exceptional sensitivity (detection limit: 145 nM) and selectivity over a wide linear range (5–105 μM), along with rapid response kinetics. Moreover, SeQDs show low cytotoxicity and efficient cellular uptake, enabling cell imaging and intracellular Cr(VI) monitoring. Significant fluorescence quenching in Cr(VI)-exposed cells confirms the potential of SeQDs as a viable fluorescent nanoprobe for Cr(VI) detection in complex cellular environments. This work thus not only establishes a simple method for the preparation of fluorescent SeQDs but also develops a promising fluorescent nanoprobe for cell imaging and Cr(VI) sensing. Full article

Fluorescence-based techniques have great potential in the field of bioimaging and could bring tremendous progress in microbiology and biomedicine. The most essential element in these techniques is fluorescent nanomaterials. The use of fluorescent nanoparticles as contrast agents for bioimaging is a large topic to cover. The purpose of this mini-review is to give the reader an overview of biocompatible and biodegradable fluorescent nanoparticles that are emerging nanomaterials for use in fluorescent bioimaging. In addition to the biocompatibility of these nanomaterials, biodegradability is considered a necessity for short-term sustainable bioimaging. Firstly, the main requirements for bioimaging are raised, and a few existing fluorescent nanoprobes are discussed. Secondly, a few inert biocompatible fluorescent nanomaterials for long-term bioimaging that have been, to some extent, demonstrated as fluorescent probes are reviewed. Finally, a few biocompatible and biodegradable nanomaterials for short-term bioimaging that are evolving for bioimaging applications are discussed. Together, these advancements signal a transformative leap toward sustainability and functionality in biomedical imaging. Full article

Gold nanoparticles (AuNPs) are highly attractive for applications in the field of biosensing, particularly for colorimetric nucleic acid detection. Their unique optical properties, which are highly sensitive to changes in their environment, make them ideal candidates for developing simple, rapid, and cost-effective assays. When functionalized with oligonucleotides (Au-nanoprobes), they can undergo aggregation or dispersion in the presence of complementary sequences, leading to distinct color changes that serve as a visual signal for detection. Aggregation-based assays offer significant advantages over other homogeneous assays, such as fluorescence-based methods, namely, label-free protocols, rapid interactions in homogeneous solutions, and detection by the naked eye or using low-cost instruments. Despite promising results, the application of Au-nanoprobe-based colorimetric assays in complex biological matrices faces several challenges. The most significant are related to the colloidal stability and oligonucleotide functionalization of the Au-nanoprobes but also to the mode of detection. The type of functionalization method, type of spacer, the oligo–AuNPs ratio, changes in pH, temperature, or ionic strength influence the Au-nanoprobe colloidal stability and thus the performance of the assay. This review elucidates characteristics of the Au-nanoprobes that are determined for colorimetric gold nanoparticles (AuNPs)-based nucleic acid detection, and how they influence the sensitivity and specificity of the colorimetric assay. These characteristics of the assay are fundamental to developing low-cost, robust biomedical sensors that perform effectively in biological fluids. Full article

Carbon dots (CDs) derived from mandarin peel biochar (MBC) at different pyrolysis temperatures (200, 400, 600, and 800 °C) have been synthesized and characterized. This high-value transformation of waste materials into fluorescent nanoprobes for environmental monitoring represents a step forward towards a circular economy. In this itinerary, CDs produced via one-pot hydrothermal synthesis were utilized for the detection of copper (II) ions. The study looked at the spectroscopic features of biochar-derived CDs. The selectivity of CDs obtained from biochar following carbonization at 400 °C (MBC400-CDs towards various heavy metal ions resulted in considerable fluorescence quenching with copper (II) ions, showcasing their potential as selective detectors. Transmission electron microscopic (TEM) analysis validated the MBC-CDs’ consistent spherical shape, with a particle size of <3 nm. The Plackett–Burman Design (PBD) was used to study three elements that influence the F₀/F ratio, with the best ratio obtained with a pH of 10, for 10 min, and an aqueous reaction medium. Cu (II) was detected over a dynamic range of 4.9–197.5 μM and limit of detection (LOD) of 0.01 μM. Validation testing proved the accuracy and precision for evaluating tap and mountain waters with great selectivity and no interference from coexisting metal ions. Full article

This study introduces a novel approach for transforming the cationic surfactant, cetyltrimethylammonium bromide (CTAB), into fluorescent carbon dots (CDs) capable of detecting cadmium ions at ultralow concentrations. The current approach involves preparing CDs through hydrothermal process at various pH levels. The CDs synthesized using pH 10, CTAB-CDs-10, exhibited the highest fluorescence quantum yield (QY), 14.22%. UV-Vis spectroscopy helped identify specific peaks between 210 and 300 nm, corresponding to the π–π* transitions of the aromatic C=C bonds. Transmission electron microscopic (TEM) analysis verified the uniform spherical morphology with a particle size < 2.45 nm. FT-IR analysis confirmed the presence of C=C stretching vibrations. The Box–Behnken (BB) Design was used to reconnoiter the influence of three variables on the response parameter: the F₀/F ratio. The best performance could be achieved at a pH of 9, after only 300 s, and a temperature of 50 °C. The developed CTAB-CDs-based nanoprobe showed an ON–OFF behavior when came in contact with cadmium (II) and demonstrated high sensitivity with a limit of detection as low as 0.06 µM (0.007 ppm) over a wide linear range of 2–103 µM. Validation tests confirmed the applicability of the CTAB-CDs-based nanoprobe for detecting cadmium (II) in tap and drinking waters with high accuracy and precision. Full article

A fluorescent probe based on ternary AgFeS₂ quantum dots has been prepared for the design of ternary chalcogenides. The nanoparticles are synthesized with oleylamine as a stabilizer at a low temperature (particle size in the range of 2 to 3 nm) and they exhibit an intense blue emission in aqueous media. As for their internal structure, each nanoparticle’s relative stoichiometric ratio (AgFe_1.01S_1.91) is very close to the theoretical value of 1:1:2. Their magnetic properties have been studied with a vibrating sample magnetometer and they have ferromagnetism between 4 K and 298 K (applied magnetic field ranging between −10,000 and 10,000 Oe). In the presence of iodide ions, the emission at 458 nm derived from AgFeS₂ QDs has been observed to give rise to fluorescence quenching. The detection system is based on a static quenching process and morphological change between iodide ions and AgFeS₂, which has a good linear range from 0 to 37.5 μmol/L, with a limit of detection of 0.99 μM. The nanoprobe responds within 30 s for the efficient detection of iodide. Such functional quantum dots will provide a powerful indicator in environmental and bio-sensing applications. Full article

Luminescent Ag nanoclusters (Ag NCs) are a promising probe material for sensing and bioimaging applications. However, the intrinsic obstacle of poor water stability and photostability greatly restrict their practical application in biological systems. Herein, we report the intracellular hypochlorite (ClO⁻) detection with amphiphilic copolymer-modified luminescent Ag NCs with good biocompatibility and photostability. The Ag NCs were synthesized by using chemically inert hydrophobic ligands and then modified with an amphiphilic (1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(poly(ethylene glycol))-2000]) (DSPE-PEG-2000) and sodium dodecyl sulfonate (SDS) for phase transfer. It was found that the approach of the removal of organic solvents during the phase transfer has remarkable influences on the properties of the Ag NCs, including their size, luminescence property, and aqueous stability. Furthermore, the silver core of Ag NCs could be oxidatively damaged by ClO⁻, thereby causing photoluminescence (PL) quenching. The ClO⁻-induced PL quenching was specific over the other common reactive oxygen species (ROS) as well as some common interferences. Finally, they have been successfully applied as a fluorescent nanoprobe for detecting exogenous and endogenous ClO⁻ in living cells. Full article

In this work, we demonstrated a novel, sensitive and effective fluorescent naringin (NRG) and naringenin (NRGe) detection method using polymethionine nanoparticles (PMNPs) as a fluorescent nanoprobe. The PMNPs were first synthesized by autopolymerization of methionine at 90 °C when trace copper ions existed. The as-prepared PMNPs were thoroughly characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), gel permeation chromatograph (GPC), nuclear magnetic resonance spectroscopy (NMR), transient and steady-state fluorescence and UV–Vis absorption spectroscopy. The quenching mechanism was attributed to the inner filter effect (IFE). Moreover, the developed assay was used successfully to detect NRG and NRGe in real samples of citrus fruits, illustrating that this detection method has great potential application in the field of citrus fruits analysis. Full article

Cu²⁺ has increasingly become a great threat to the natural environment and human health due to its abundant content and wide application in various industries. DL-Mercaptosuccinic acid and ZnS-modified Fe₃O₄ nanocomposites were designed, synthesized, and applied in the determination of Cu²⁺. The prepared nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopes (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), and thermogravimetric analyzer (TG). The magnetic fluorescent nanoprobe exhibited highly selective and sensitive fluorescence-quenching characteristics with Cu²⁺ ions. The fluorescence detection linear range was 0–400 μM, with the detection limit being 0.489 μM. In addition, the magnetic fluorescent nanoprobe exhibited a high adsorption and removal rate for Cu²⁺. It had been successfully applied to detect Cu²⁺ in real water samples with a satisfactory recovery rate. The magnetic fluorescent nanoprobe could simultaneously realize the functions of enrichment, quantitative detection, and separation, reduce the pollution of copper ions and probes, and establish an environment-friendly detection method. Consequently, the magnetic fluorescent nanoprobe offered a new pathway for the removal and detection of not only Cu²⁺ but also other heavy metal ions in water. Full article

Imaging methods by the means of optical sensors are applied in diverse scientific areas such as medical research and diagnostics, aerodynamics, environmental analysis, or marine research. After a general introduction to the field, this review is focused on works published between 2012 and 2022. The covered topics include planar sensors (optrodes), nanoprobes, and sensitive coatings. Advanced sensor materials combined with imaging technologies enable the visualization of parameters which exhibit no intrinsic color or fluorescence, such as oxygen, pH, CO₂, H₂O₂, Ca²⁺, or temperature. The progress on the development of multiple sensors and methods for referenced signal read out is also highlighted, as is the recent progress in device design and application formats using model systems in the lab or methods for measurements’ in the field. Full article

Glutathione (GSH) and nickel (II) cation have an indispensable role in various physiological processes, including preventing the oxidative damage of cells and acting as a cofactor for lipid metabolic enzymes. An imbalance in the physiological level of these species may cause serious health complications. Therefore, sensitive and selective fluorescent probes for the detection of GSH and nickel (II) are of great interest for clinical as well as environmental monitoring. Herein, vancomycin-conjugated gold nanoparticles (PEI-AuNP@Van) were prepared and employed for the detection of GSH and nickel (II) based on a turn-on-off mechanism. The as-synthesized PEI-AuNP@Van was ~7.5 nm in size; it exhibited a spherical shape with face-centered cubic lattice symmetry. As compared to vancomycin unconjugated gold nanoparticles, GSH led to the turn-on state of PEI-AuNP@Van, while Ni²⁺ acted as a fluorescence quencher (turn-off) without the aggregation of nanoparticles. These phenomena strongly justify the active role of vancomycin conjugation for the detection of GSH and Ni²⁺. The turn-on-off kinetics was linearly proportional over the concentration range between 0.05–0.8 µM and 0.05–6.4 μM. The detection limits were 205.9 and 90.5 nM for GSH and Ni²⁺, respectively; these results are excellent in comparison to previous reports. This study demonstrates the active role of vancomycin conjugation for sensing of GSH and Ni²⁺ along with PEI-AuNP@Van as a promising nanoprobe. Full article

As an important barrier between the cytoplasm and the microenvironment of the cell, the cell membrane is essential for the maintenance of normal cellular physiological activities. An abnormal cell membrane is a crucial symbol of body dysfunction and the occurrence of variant diseases; therefore, the visualization and monitoring of biomolecules associated with cell membranes and disease markers are of utmost importance in revealing the biological functions of cell membranes. Due to their biocompatibility, programmability, and modifiability, DNA nanomaterials have become increasingly popular in cell fluorescence imaging in recent years. In addition, DNA nanomaterials can be combined with the cell membrane in a specific manner to enable the real-time imaging of signal molecules on the cell membrane, allowing for the real-time monitoring of disease occurrence and progression. This article examines the recent application of DNA nanomaterials for fluorescence imaging on cell membranes. First, we present the conditions for imaging DNA nanomaterials in the cell membrane microenvironment, such as the ATP, pH, etc. Second, we summarize the imaging applications of cell membrane receptors and other molecules. Finally, some difficulties and challenges associated with DNA nanomaterials in the imaging of cell membranes are presented. Full article