ZIF-8@GMP-Tb nanocomplex for ratiometric fluorescent detection of alkaline phosphatase activity

Lanthanide coordination polymers@CuO nanoparticles: Enhanced self-cascade nanoenzyme activity and ratiometric fluorescence assay of glutathione

Tandem enzyme can catalyze some cascade reactions with high efficiency, and some few tandem enzyme-like mimics have been discovered recently. Further improving the catalytic efficiency of tandem nanoenzymes with facile method may undoubtedly promote and broaden their applications in various fields. In this work, cupric oxide nanoparticles (CuO NPs) with dual-functional enzyme mimics were synthesized using the rapid deposition method in advance, which simultaneously combined with lanthanide infinite coordination polymers (Ln ICPs) during the self-assemble of Tb3+, guanine-5'-triphosphate (GTP) and auxiliary ligand terephthalic acid (TA). Excitingly, the obtained Tb-GTP/TA@CuO ICPs, not only displayed obviously enhanced tandem catalytic activity compared with pure CuO NPs, but also provided a versatile ratiometric platform for ultrahigh selective and sensitive detection of glutathione (GSH) under single-wavelength excitation. A good linear relationship between the ratio signal and the GSH concentration was spanning from 0.001 to 20 μM with an impressive detection limit of 0.50 nM. This study opens a new and universal avenue for preparing integrated multifunctional probes by coupling of nanoenzyme catalytic activity with superior luminescent Ln ICPs through facile method.

Research progress of organic fluorescent probes for lung cancer related biomarker detection and bioimaging application

As one of the major public health problems, cancers seriously threaten the human health. Among them, lung cancer is considered to be one of the most life-threatening malignancies. Therefore, developing early diagnosis technology and timely treatment for lung cancer is urgent. Recent research has witnessed that measuring changes of biomarkers expressed in lung cancer has practical significance. Meanwhile, we note that bioimaging with organic fluorescent probes plays an important role for its high sensitivity, real-time analysis and simplicity of operation. In the past years, kinds of organic fluorescent probes targeting lung cancer related biomarker have been developed. Herein, we summarize the research progress of organic fluorescent probes for the detection of lung cancer related biomarkers in this review, along with their design principle, luminescence mechanism and bioimaging application. Additionally, we put forward some challenges and future prospects from our perspective.

Dual-functional metal-organic frameworks-based hydrogel micromotor for uranium detection and removal

Self-propelled micro/nanomotors have attracted great attention for environmental remediation, however, their use for radioactive waste detection and removal has not been addressed. Engineered micromotors that are able to combine fast detection and highly adsorptive capability are promising tools for radioactive waste management but remain challenging. Herein, we design self-propelled micromotors based on zeolite imidazolate framework (ZIF-8)-hydrogel composites via inverse emulsion polymerization and show their potential for efficient uranium detection and removal. The incorporation of magnetic ferroferric oxide nanoparticles enables the magnetic recycling and actuation of the single micromotors as well as formation of swarms of worm-like or tank-treading structure. Benefited from the enhanced motion, the micromotors show fast and high-capacity uranium adsorption (747.3 mg g-1), as well as fast uranium detection based on fluorescence quenching. DFT calculation confirms the strong binding between carboxyl groups and uranyl ions. The combination of poly(acrylic acid-co-acrylamide) with ZIF-8 greatly enhances the fluorescence of the micromotor, facilitating the high-resolution fluorescence detection. A low detection limit of 250 ppb is reached by the micromotors. Such self-propelled micromotors provide a new strategy for the design of smart materials in remediation of radioactive wastewater.

A ternary nucleotide-lanthanide coordination nanoprobe for ratiometric fluorescence detection of ciprofloxacin

Ciprofloxacin (CIP) is a widely used broad-spectrum antibiotic and has been associated with various side effects, making its accurate detection crucial for patient safety, drug quality compliance, and environmental and food safety. This study presents the development of a ternary nucleotide-lanthanide coordination nanoprobe, GMP-Tb-BDC (GMP: guanosine 5'-monophosphate, BDC: 2-amino-1,4-benzenedicarboxylic acid), for the sensitive and ratiometric detection of CIP. The GMP-Tb-BDC nanoprobe was constructed by incorporating the blue-emissive ligand BDC into the Tb/GMP coordination polymers. Upon the addition of CIP, the fluorescence of terbium ion (Tb3+ ) was significantly enhanced due to the coordination and fluorescence sensitization properties of CIP, while the emission of the BDC ligand remained unchanged. The nanoprobe demonstrated good linearity in the concentration range of 0-10 μM CIP. By leveraging mobile phone software to analyze the color signals, rapid on-site analysis of CIP was achieved. Furthermore, the nanoprobe exhibited accurate analysis of CIP in actual drug and milk samples. This study showcases the potential of the GMP-Tb-BDC nanoprobe for practical applications in CIP detection.

Fluorescence detection platform of metal-organic frameworks for biomarkers

Sensitive and selective detection of biomarkers is crucial in the study and early diagnosis of diseases. With the continuous development of biosensing technologies, fluorescent biosensors based on metal-organic frameworks have attracted increasing attention in the field of biomarker detection due to the combination of the advantages of MOFs, such as high specific surface area, large porosity, and structure with tunable functionality and the technical simplicity, sensitivity and efficiency and good applicability of fluorescent detection techniques. Therefore, researchers must understand the fluorescence response mechanism of such fluorescent biosensors and their specific applications in this field. Of all biomarkers applicable to such sensors, the chemical essence of nucleic acids, proteins, amino acids, dopamine, and other small molecules account for about a quarter of the total number of studies. This review systematically elaborates on four fluorescence response mechanisms: metal-centered emission (MC), ligand-centered emission (LC), charge transfer (CT), and guest-induced luminescence change (GI), presenting their applications in the detection of nucleic acids, proteins, amino acids, dopamine, and other small molecule biomarkers. In addition, the current challenges of MOFs-based fluorescent biosensors are also discussed, and their further development prospects are concerned.

Brine available two-dimensional nano-architectonics of fluorescent probe based on phosphate doped ZIF-L for detection of Fe3

Herein, we propose a simple and effective strategy for designing a zeolitic imidazolate frameworks (ZIFs) fluorescent probe with a two-dimensional leaf-like structure. By doping ZIF-L with phosphate, we developed a fluorescent probe for iron (Fe3+) in systems with high salinity. The fluorescence of P-ZIF-L was quenched effectively with the presence of Fe3+. The physicochemical structure, surface morphology, selectivity, stability and composition of the probe were investigated. Under optimized conditions, the fluorescent probe had a detection limit of 0.5 μM. Furthermore, the results that the probe exhibited desirable salt-tolerance and was suitable for determination of Fe3+ in brine water samples with satisfactory results.

Detection of heavy metal ion in real samples with fiber based paper based on new rare earth cluster

Chromium (Cr) is an important material, but also one of the most toxic heavy metal pollutants, showing great threat to human health and ecological environment, thus, accurate and rapid detection of Cr³⁺ has far-reaching significance. In this work, based on the ligand of 2,3,4,5,6-pentafluorobenzoic acid (HPFBA) that does not contains oscillation effect group such as "CH, OH, and NH bond", three rare earth dinuclear cluster of Ln₂(PFBA)₆(phen)₂(H₂O)₂ (Ln = Tb³⁺1-Tb, Eu³⁺1-Eu, Gd³⁺1-Gd, phen = 1,10-phenanthroline) were obtained. 1-Tb shows excellent stability and luminescence properties. In depth investigation reveals that 1-Tb shows quick detection towards Cr³⁺ in water through luminescence "turn-off", with extremely short response time of 1.0 min, very low limit of detection (LOD) of 5.2 ppb and no interference from other ions. The LOD value is much lower than the total content of chromium for water in China (15 ppm, GB9078-1996). In the actual environment such as tap water, lake water, human, and serum, 1-Tb shows excellent detection and recovery rate for Cr³⁺. More interestingly, a fiber based paper of test paper that based on 1-Tb and ordinary filter paper was fabricated, which can probe Cr³⁺ by visible color changes to the naked eye under UV light.

In situ reaction-based ratiometric fluorescent assay for alkaline phosphatase activity and bioimaging

Alkaline phosphatase (ALP) is an important biomarker, it is of great significance to develop a sensitive and efficient analytical method for ALP. In this study, an in situ reaction based ratiometric fluorescence assay for ALP was proposed. l-ascorbic acid-2-phosphate (AA2P) was used as a substrate for ALP, and Cu²⁺/o-phenylenediamine (OPD) were involved in this system. Cu²⁺ can oxidize OPD to 2,3-diaminophenazine (OPDox) with an emission centered at 566 nm. The presence of ALP can catalyze the hydrolysis of AA2P to ascorbic acid (AA), which will inhibit the production of OPDox and reduce the corresponding fluorescence intensity, and AA will react with OPD to generate 3-(dihydroxyethyl)furan[3,4-b]quinoxalin-1-one (DFQ) with an emission peak at 447 nm. The fluorescence ratio of F447/F566 has a linear relationship with ALP activity. The proposed method is highly sensitive, finely selective, cost efficiency and easy to operate, it exhibits good linearity in the range of 0.5-22 and 22-40 mU·mL^-1, with a detection limit as low as 0.06 mU·mL^-1. The excellent applicability of this strategy in human serum samples and MCF-7 cells imaging suggests that this method has promising prospects for biomedical research.

pH-activated DNA nanomachine for miRNA-21 imaging to accurately identify cancer cell

MicroRNA (miRNA) imaging has been employed to distinguish cancer cells from normal cells by exploiting the overexpression of miRNA in cancer. Inspired by the acidic extracellular tumor microenvironment, we designed a pH-activated DNA nanomachine to enable the specific detection of cancer cells using miRNA imaging. The DNA nanomachine was engineered by assembling two hairpins (Y1 and Y2) onto the surface of a ZIF-8 metal-organic framework (MOF), which decomposed under acidic conditions to release the adsorbed DNA hairpin molecules in situ. The released hairpins were captured by the target miRNA-21 and underwent catalytic hairpin assembly amplification between Y1 and Y2. The detection limit for miRNA assays using the DNA nanomachine was determined to be 27 pM, which is low enough for sensitive detection in living cells. Living cell imaging of miRNA-21 further corroborated the application of the DNA nanomachine in the identification of cancer cell.

Highly sensitive sensing device based on highly luminescent lanthanide nanocluster for biomarker in human urine and serum

The level of L-kynurenine (L-kyn) can reflect the health state of human body, and the determination of L-kyn can be used for the medical diagnosis of several cancers and neurological diseases. In this work, a series of air-, water-, and thermo-stable dinuclear lanthanide nanoclusters [Ln₂(2,5-DFBA)₆(phen)₂] (Tb 1, Eu 2, Gd 3, 2,5-DFBA = 2,5-difluorobenzoic acid, phen = 1,10-phenanthroline) are obtained by a facial method. 1 and 2 show very high luminescence quantum yields (QYs) of 71.7% and 81.8%, respectively. Interestingly, investigation reveals that 1 is a quick, highly sensitive and selective sensor for L-kyn in real samples of urine and serum. Furthermore, transmission electron microscope (TEM) results reveal that nanocluster 1 is stable in solution and can be uniform distributed on the base, suggesting it can be deposited on various supports to fabricate sensing devices. Thus, 1 is fabricated into a sensitive test paper for the eye-readable detection of L-kyn in real samples of human urine and serum. The limit of detection (LOD) as low as 0.3 μM, which is enough to rapidly determine L-kyn in human body liquor (usually 5 μM in healthy human body).

Target-induced inner-filter effect-based ratiometric sensing platform by fluorescence modulation of persistent luminescent nanoparticles and 2, 3-diaminophenazine

A ratiometric fluorescence sensing platform with smartphone was designed for highly sensitive detection of glutathione (GSH), ascorbic acid (AA), and alkaline phosphatase (ALP) activity by modulation the inner filter effect...

Sensitive ratiometric fluorescence probe based on chitosan carbon dots and calcein for Alkaline phosphatase detection and bioimaging in cancer cells

Alkaline phosphatase (ALP) is a commonly used marker in clinical practice, and this enzyme is a key indicator for diagnosing various diseases. In this study, we describe the development of a reliable and novel fluorescent assay for ALP detection based on chitosan carbon dots (C-CDs, peak emission, 412 nm) and calcein (peak emission, 512 nm). In the presence of Eu³⁺ (which binds calcein), the fluorescence intensity of calcein is quenched. Utilizing the ALP-triggered generation of phosphate ions (PO₄^3-) from the substrate p-nitrophenyl phosphate (pNPP), the Eu³⁺ ions bind PO₄^3- (which shows a higher affinity toward Eu³⁺ than calcein), and the fluorescence of calcein is recovered. As a consequence, C-CDs fluorescence is decreased by inner filter effect (IFE). Exploiting these changes in the fluorescence intensity ratio of C-CDs and calcein, we developed a high sensitivity, accurate, and easily synthesized ratiometric fluorescence probe. Our novel fluorescent bioassay demonstrates good linear relationship in the 0.09-0.8 mU mL^-1 range, with a low detection limit of 0.013 mU mL^-1. The excellent applicability of this novel assay in HepG2 cells and human serum samples demonstrates that our novel method has excellent biomedical research and disease diagnosis prospects.