A universal strategy for constructing high-performance silica-based AIE materials for biomedical application.

As an emerging fluorophore, aggregation-induced emission luminogens (AIEgens) have received widespread attention in recent years, but the inherent drawbacks of AIEgens, such as the poor water-solubility and insufficient fluorescence stability in complex environments, restrict their performance in practical applications. Herein, we report a universal strategy based on hydrophobic dendritic mesoporous silica (HMSN) that can integrate different AIE molecules to construct multi-color fluorescent AIE materials. Specifically, HMSN with central radial pores was used as a powerful carrier for direct loading AIE molecules and restricting their intramolecular motions. Due to the pore-domain restriction effect and hydrophobic interaction, the obtained silica-based AIE materials have bright fluorescence with a maximum quantum yield of 68.38%, high colloidal/fluorescence stability, and excellent biosafety. Further, these silica-based AIE materials can be conjugated with functional antibodies to obtain probes with different targetability. After integration with immunomagnetic beads, the prepared detection probes achieved the quantitative detection of cardiac troponin I with the limit of detection (LOD) of 0.508 ng/mL. Overall, the targeting probes stemming from silica-based AIE materials can not only achieve cell-specific imaging, but quantify the number of Jurkat cells (LOD = 270 cells/mL) to further determine the specific etiology of the disease.

Eu3+ functionalized metal-organic framework for selective monitoring of emerging environmental pollutants non-steroidal anti-inflammatory drugs.

Non-steroidal anti-inflammatory drugs (NSAIDs), as a new water pollutant emerging in recent years, has potential hazards to the environment. The difficult degradation characteristics of NSAIDs lead to long-term accumulation in the natural environment, which will inevitably cause incalculable damage to human health. In this work, for practical application considerations, MIL-53(Al) type MOF [Al(OH)(TDC)]‧1.5H2O‧0.7DMF (MIL-53-TDC, TDC = 2,5-thiophene dicarboxylic acid) with good water stability is selected as the sensing main body. The ligand TDC was chosen for two reasons: one is as an antenna ligand, which can sensitize Eu3+ ions to emit characteristic fluorescence; the other is as binding site that the sulfur atoms on the thiophene ring can introduce Eu3+ ions through coordination. Thus, Eu3+ functionalized MIL-53-TDC hybrid materials (Eu@MIL-53-TDC) were developed as a fluorescence sensor for the detection of two kinds of NSAIDs, S-ibuprofen (S-IBP) and diclofenac (DCF). The concentration range of S-IBP and DCF detected by the prepared sensors is 0.001-0.07 mM (LOD = 0.5 µM) and 0.0005-0.1 mM (LOD = 0.2 µM), respectively. Moreover, this sensor not only can achieve rapid (3 min) and sensitive analysis of these two NSAIDs but also has a satisfactory recovery for the detection of S-IBP and DCF in serum and tap water.

Terbium-based metal-organic frameworks through energy transfer modulation for visual logical sensing zinc and fluorine ions.

Zinc is the second most abundant trace element in the human central nervous system, which is closely related to various physiological activities in the human body. Fluoride ion is one of the most harmful elements in drinking water. Excessive intake of F- may cause dental fluorosis, renal failure, or DNA damage. Therefore, it is urgent to develop sensors with high sensitivity and selectivity for the detection of Zn2+ and F- ions at the same time. In this work, a series of mixed lanthanide metal-organic frameworks (Ln-MOFs) probes are synthesized using a simple method of in situ doping. The luminous color can be finely modulated by changing the molar ratio of Tb3+ and Eu3+ during synthesis. Benefiting from the unique energy transfer modulation mechanism, the probe has the continuous detection capability of zinc ions and fluoride ions. The detection of Zn2+ and F- in a real environment shows that the probe has a good practical application prospect. The as-designed sensor at 262 nm excitation can sequentially detect Zn2+ concentrations ranging from 10-8 to 10-3 M (LOD = 4.2 nM) and F- levels ranging from 10-5 to 10-3 M (LOD = 3.6 µM) with high selectivity. Based on different output signals, a simple Boolean logic gate device is constructed to realize intelligent visualization of Zn2+ and F- monitoring.

One step functional assembly of guanosine monophosphate and terbium ion on metal organic frameworks for determination of alkaline phosphatase activity.

Since the abnormal changes of alkaline phosphatase (ALP) content may indicate the occurrence of some diseases, the detection of ALP activity is of great significance in human health monitoring. In this work, the luminescent probe (His@ZIF-8-Tb-GMP) was synthesized by self-assembly of guanosine monophosphate (GMP) and terbium ions with l-Histidine (His) functionalized zeolite imidazole framework ZIF-8 (His@ZIF-8) by one-step method. The abundant amino and carboxyl groups on His@ZIF-8 can be used to capture Tb3+ ions, which increases the load capacity of terbium ions and further enhances its luminescence signals. GMP is the antenna sensitizing ligand of terbium ion and the recognition unit of ALP detection. Dephosphorization of alkaline phosphatase prevents the energy transfer from GMP to terbium ion, which leads to the fluorescence quenching of the probe. Based on the above detection mechanism, a fluorescence sensing platform triggered by cutting off the energy transfer path was developed for the quantitative determination of ALP. Significantly, this sensor possesses ultra-sensitivity and high selectivity in the determination of alkaline phosphatase, whose detection limit is 0.0006 U/L. The successful application of the sensor in serum also shows that the sensor has a good practical application prospect.

Dye-functionalized metal-organic frameworks with the uniform dispersion of MnO2 nanosheets for visualized fluorescence detection of alanine aminotransferase.

The wide applications of metal-organic framework (MOF) luminescent materials in the field of optics have attracted the general attention of researchers. Therefore, the development of simple and multifunctional MOF light-emitting platforms have become a research hotspot. The composites (MnO2@ZIF-8-luminol) were prepared by an in situ synthesis method and room-temperature covalent reaction. The composites and o-phenylenediamine (OPD) constitute a dual emission sensor for detecting alanine aminotransferase (ALT). OPD can be oxidized by MnO2 to 2,3-diaminophenazine (DAP) with yellow fluorescence emission, which inhibits the blue emission of luminol through fluorescence resonance energy transfer (FRET). The presence of tiopronin (TP) will destroy the FRET process, extinguishing the yellow fluorescence emission and restoring the blue fluorescence emission. The special effect between ALT and TP will further reverse the changes in the two fluorescent signals. Moreover, in the detection process, when the blue and yellow fluorescence energies in the system are within a certain range, a new white light emission will be generated, which causes the sensing of ALT to present ternary visualization. In addition, a high-security anti-counterfeiting platform is constructed by using the prepared materials and agarose hydrogels. The anti-counterfeiting platform can encrypt information on demand according to the luminous characteristics of different materials. This study not only provides a typical case of ternary visualization sensing by MOF-based materials but also develops a possible method for the construction of a MOF-based hydrogel anti-counterfeiting platform.

Design of a ratiometric fluorescence sensor based on metal organic frameworks and Ru(bpy)32+-doped silica composites for 17ß-Estradiol detection.

17ß-Estradiol (E2), an important endocrine disrupting compound, could be quantitatively detected by fluorescence resonance energy transfer (FRET) aptasensor, designed in this paper. Metal organic frameworks have large specific surface area and easily modifiable groups, which are helpful for the construction of aptasensor. Specifically, streptavidin was immobilized on the synthesized MIL-53-NH2 by covalent bonding, and further linked with the biotin modified E2 aptamer (apt) through specific bonding between avidin and biotin to obtain the FRET donor probe (MIL-53-apt). Meanwhile, complementary DNA (cDNA) modified Ru(bpy)32+-doped silica nanoparticles (RuSiO2-cDNA) were prepared through covalent bonding. They acted as the FRET acceptor probe, since its absorption spectrum showed large overlap with the emission spectrum of MIL-53-apt. In the presence of E2, aptamer modified donor probes tended to bind with E2, owing to their higher selectivity and affinity. Therefore, the optimal distance between FRET pairs was broken, resulting in the fluorescence emission recovery of donor and the fluorescence emission of acceptor decreased. Under optimal conditions, this proposed aptasensor displayed sensitive detection of E2 ranging from 0.5 to 1000 nM with a detection limit of 0.2 nM. Furthermore, the sensor provides a promising method for rapid and sensitive detection of other small biological molecules.

Design and Biosensing of a Ratiometric Electrochemiluminescence Resonance Energy Transfer Aptasensor between a g-C3N4 Nanosheet and Ru@MOF for Amyloid-ß Protein.

A dual-wavelength ratiometric electrochemiluminescence resonance energy transfer (ECL-RET) aptasensor based on the carbon nitride nanosheet (g-C3N4 NS) and metal-organic frameworks (Ru@MOFs) as energy donor-receptor pairs is first designed for the detection of the amyloid-ß (Aß) protein. The cathode ECL of g-C3N4 NS gradually decreased, whereas the anode ECL from Ru@MOF pyramidally enhanced along with the increasing concentration of Aß in a 0.1 M phosphate-buffered saline solution containing 0.1 M S2O82-. Additionally, it is worth noting that 2-amino terephthalic acid from MOF not only can load abundant amounts of luminophor Ru(bpy)32+ but also promote the conversion of more amounts of S2O82- that served as a coreactant accelerator into SO4•-, further enhancing the ECL signal of Ru@MOF. Besides, the ECL intensity from the g-C3N4 NS had a tremendous spectrum overlap with the UV-vis spectrum of Ru@MOF, demonstrating the high-efficiency ECL-RET from g-C3N4 NS to Ru@MOF. According to the ratio of ECL460nm/ECL620nm, the constructed aptasensor for the detection of Aß showed a wide linear range from 10-5 to 500 ng/mL and a low detection limit of 3.9 fg/mL (S/N = 3) with a correction coefficient of 0.9965. The obtained results certified that the dual-wavelength ratiometric ECL sensor could provide a reliable direction and have the potential for application in biosensing and clinical diagnosis fields.

Electroluminescent aptasensor based on RuSiO2 nanoparticles for detection cytochrome c using ferrocene as quenching probe.

A stable sandwiched electrochemiluminescence (ECL) aptasensor was originally constructed established upon Ru(bpy)32+-doped silica nanoparticles (RuSiO2 NPs) with ferrocene carboxylic acid-aptamer (Fc-aptamer) to quantitatively detect cytochrome c (Cyt C). Herein, RuSiO2 NPs and Fc-aptamer were respectively prepared through the microemulsion method and amide reaction to fabricate the ECL aptasensor. Furthermore, Fc-aptamer was used as quenching probe for quenching the ECL emission of RuSiO2 NPs. In detail, RuSiO2 NPs were primarily immobilized onto the electrodes by the film-forming function of chitosan. Subsequently, the aptamer was incubated onto the decorated GCE via crosslinking with glutaraldehyde (GA). After Cyt C was connected to the GCE via immunoreaction, Fc-aptamer was immobilized onto the modified electrodes owing to the specific recognition between antigens and aptamer. Ultimately, ECL signals markedly descended owing to the poor electricity conductivity of proteins and superior quenching effect of Fc-aptamer. Under optimum conditions, the designed ECL aptasensor indicated an accurate analysis for Cyt C in a rang of 0.001-100 nM with a detection limit of 0.48 pM (S/N = 3).

Electrochemiluminescence resonance energy transfer biosensor between the glucose functionalized MnO2 and g-C3N4 nanocomposites for ultrasensitive detection of concanavalin A.

An electrochemiluminescence (ECL) analytical platform was initially proposed based on the electrochemiluminescence resonance energy transfer (ECL-RET) mechanism for ultrasensitive detection of Concanavalin A (Con A). In this protocol, the glucose functionalized carboxylic g-C3N4 nanosheets (g-C3N4-COOH@Glu) and MnO2 nanoparticles covered carboxylic multi-wall carbon nanotubes (BSA@MnO2-MWCNTs-COOH@Glu) were synthesized and acted as ECL-RET electron donor and acceptor, respectively. Herein, glucose was served as the recognition element for binding Con A and MWCNTs was utilized as the carrier materials for loading MnO2. When the quenching probe BSA@MnO2-MWCNTs-COOH@Glu was incubated onto the modified electrodes via the specific carbohydrate-Con A interaction, the ECL signals of g-C3N4-COOH@Glu which used S2O82- as its coreactant have drastically declined. Under optimum conditions, this biosensor performed a sensitive detection of the Con A ranging from 1 × 10-5 to 1 × 104 ng/mL with a detection limit of 2.2 fg/mL (S/N = 3). Moreover, favorable analytical outcomes for detecion Con A in actual serum samples were obtained, exhibiting huge applications in clinical diagnosis of this assay.

An ultrasensitive electrochemiluminescence immunosensor based on platinum nickel nanocubes-L-cysteine-luminol nanocomposite.

An ultrasensitive electrochemiluminescence (ECL) immunosensor was initially developed for quantitative detection of carbohydrate antigen 15-3 (CA15-3) using platinum nickel nanocubes-L-cysteine-luminol nanocomposite (PtNi NCs-L-Cys-luminol) as signal probe. Herein, the PtNi NCs-L-Cys-luminol nanocomposite was modified on the glassy carbon electrode (GCE) surface via the film-forming properties of chitosan. Then, the CA15-3 antibody was attached to the modified electrode surface by amidating reaction to construct the ECL immunosensor. Experimental results showed that with the capturing of CA15-3 antigen molecules on the immunosensor, the ECL signal intensity observably decreased, indicating the quenching detection principle of electrochemiluminescence. Under optimal experimental conditions, the constructed ECL immunosensor displayed remarkable performance for CA15-3 detection ranging from 0.0005 U/mL to 500 U/mL, with a relatively low detection limit of 0.000167 U/mL (S/N = 3). It might be ascribed to the fact that the PtNi NCs could dramatically promote the decomposition of H2O2 to produce various active free radical, thereby the ECL responses of luminol were prominently magnified and its sensitivity was effectively increased. The immunosensor exemplified its advantages of easy fabrication, fast analysis, high sensitivity, good reproducibility and selectivity. Moreover, the recovery tests exhibited that the sensor can be used to sensitively detect CA15-3 in serum samples, suggesting potential application prospect in bioanalysis.

Electrochemiluminescence resonance energy transfer system between GNRs and Ru(bpy)32+: Application in magnetic aptasensor for ß-amyloid.

Electrochemiluminescent (ECL) assay has gradually drawn increasing interest in the biomedical analysis. This paper proposed a new methodology for ultrasensitive and facile detection of Alzheimer's disease marker ß-amyloid (Aß) by fabricating a sandwich-type ECL sensing platform. Herein, electrochemiluminescence resonance energy transfer (ECL-RET) was employed to determine Aß concentration, which can be attributed to the quenching effect from RET between Ru(bpy)32+ and gold nanorods (GNRs) acting as ECL-RET electron donor and acceptor, respectively. In this protocol, mesoporous carbon nanospheres were adopted to immobilize ECL reactant Ru(bpy)32+ and antibody via nafion to acquire the RET donor nanocomposites (MOCs/nafion/Ru(bpy)32+/antibody), which were tightly interconnected with epoxy group functionalized Fe3O4 nanoparticles. It is of vital importance that GNRs with exquisite rod shape were synthesized and exhibited a typical absorption peak at 650nm to quench ECL signal of Ru(bpy)32+ effectively. In addition, the ECL emission decreased linearly with the logarithm of Aß concentration in a wide linear range from 1.0 × 10-5 to 100ng/mL with a detection limit of 4.2 × 10-6ng/mL. Furthermore, distinctive and desirable properties were verified to declare the promise for being applicable to analyze the Aß content in real Alzheimer's cerebrospinal fluid samples with satisfactory results.

[Impact of canopy structural characteristics on inner air temperature and relative humidity of Koelreuteria paniculata community in summer].

To investigate the diurnal variation of the correlations between the cooling and humidifying effects and canopy structural characteristics of the Koelreuteria paniculata community, the measurements of air temperature, relative humidity, canopy density, leaf area index (LAI) and mean leaf angle (MLA) were performed on calm sunny summer days in the community in Beijing Olympic Forest Park, China. There were significant correlations between the canopy density, LAI and MLA, which affected the cooling and humidifying effects together. The cooling effect reached its maximum by 12:00, whereas the humidifying effect reached its peak at 10:00. Compared with the control open space site, the community appeared to lower the air temperature by 0.43 to 7.53 °C and to increase the relative humidity by 1%-22% during the daytime. However, the cooling and humidifying effects seem to be not effective during the night. The canopy density and LAI were better for determining the cooling and humidifying effects from 9:00 to 12:00. However, these effects were largely controlled only by the canopy density from 12:00 to 14:00 and were significantly correlated with the canopy density and LAI afterwards until 18:00.