Bimetal MOFs catalyzed Fenton-like reaction for dual-mode detection of thiamphenicol.

In this work, we used a simple ultrasonic stripping method to synthesize a bimetal MOFs at room temperature as a nanoenzyme with peroxidase-like (POD-like) activity. Through bimetal MOFs catalytic Fenton-like competitive reaction, thiamphenicol can be quantitatively dual-mode detected by fluorescence and colorimetry. It realized the sensitive detection of thiamphenicol in water, and the limits of detection (LOD) were 0.030 nM and 0.031 nM, and the liner ranges were 0.1-150 nM and 0.1-100 nM, respectively. The methods were applied to river water, lake water and tap water samples, and with satisfactory recoveries between 97.67% and 105.54%.

Dual-reverse-signal ratiometric fluorescence method for malachite green detection based on multi-mechanism synergistic effect.

The proposition of ratiometric detection mode has demonstrated great superiority in improving analysis accuracy by forming self-calibration. Herein, the novel dual-reverse-signal ratiometric fluorescence detection for malachite green (MG) was first achieved based on synergistic effect of fluorescence resonance energy transfer (FRET) and inner filter effect (IFE). The ratiometric fluorescence probe (B-RCDs) was self-assembled via electrostatic attraction between blue-emission carbon dots (BCDs) and red-emission carbon dots (RCDs), followed with FRET effect from BCDs to RCDs and exhibited dual-emission at 450 nm and 627 nm. In the presence of MG, the IFE effect between MG and RCDs quenched the fluorescence at 627 nm and restored the fluorescence at 450 nm, sending out two reverse signals along with an obvious color change from pink to purple (302 nm UV lamp). This ratiometric method not only simplified the preparation process, but also improved the detection sensitivity, showing a low limit of detection (LOD) of 41.8 nM, which exhibited superiority than that of single-signal RCDs (157.3 nM). This method held a rapid response of 10 min and represented satisfactory recoveries (99.14%-109.08%) in real water samples, revealing it was a promising candidate in the fast, sensitive and practical detection of MG. Moreover, the design of synergistic effect supplied a new perspective for the development of ratiometric sensing in the future.

"Switch-Off-On" Detection of Fe3+ and F- Ions Based on Fluorescence Silicon Nanoparticles and Their Application to Food Samples.

An approach to the detection of F- ions in food samples was developed based on a "switch-off-on" fluorescence probe of silicon nanoparticles (SiNPs). The fluorescence of the synthetic SiNPs was gradually quenched in the presence of Fe3+ ion and slightly recovered with the addition of F- ion owing to the formation of a stable and colorless ferric fluoride. The fluorescence recovery exhibited a good linear relationship (R2 = 0.9992) as the concentration of F- ion increased from 0 to 100 µmol·L-1. The detection limit of the established method of F- ion was 0.05 µmol·L-1. The recovery experiments confirmed the accuracy and reliability of the proposed method. The ultraviolet-visible spectra, fluorescence decays, and zeta potentials evidenced the fluorescence quenching mechanism involving the electron transfer between the SiNPs and Fe3+ ion, while the fluorescence recovery resulted from the formation of ferric fluoride. Finally, SiNPs were successfully applied to detect F- ions in tap water, Antarctic krill, and Antarctic krill powder.

Bimetallic molecularly imprinted nanozyme: Dual-mode detection platform.

Molecularly imprinted polymer nanozyme (MIL-101(Co,Fe)@MIP) with bimetallic active sites and high-efficiency peroxidase-like (POD-like) activity were synthesized for the ratiometric fluorescence and colorimetric dual-mode detection of vanillin with high selectivity and sensitivity. Compared with the monometallic nanozyme, the POD-like activity of bimetallic nanozyme was greatly enhanced by changing the electronic structure and surface structure. Ratiometric fluorescence and colorimetric dual-mode detection of vanillin in aqueous solution was realized by vanillin entering specific imprinted cavities and blocking the molecular channels on the surface of MIL-101(Co,Fe)@MIP and the dual-mode visual detection was also realized. The limits of detection were as low as 104 nM and 198 nM, respectively. The method proposed in this paper was applied to the real samples of ice cream and candy. And the recoveries were between 93.3% and 105.5%, which also reached a satisfactory degree. The further detection of dexamethasone and prednisone, two drugs belonging to glucocorticoid, proved that the nanozyme analysis method based on MIL-101(Co,Fe)@MIP could be developed into a sensing platform.

HA targeted-biodegradable nanocomposites responsive to endogenous and exogenous stimulation for multimodal imaging and chemo-/photothermal therapy.

Multimodal imaging-guided accurate tumor-targeting and efficient synergistic therapy are of great importance for cancer therapy in vitro and in vivo. In this study, a biocompatible, tumor-targeted, on-demand chemo-/photothermal therapeutic nanoplatform (HIDSiGdNPs@PDA-HA) based on hollow mesoporous organic silica nanoparticles (HMONs) was used for bimodal imaging and multi-factor stepwise response for drug release and treatment. Targeted molecule hyaluronic acid (HA) promoted the endocytosis of HIDSiGdNPs@PDA-HA in HeLa cancer cells. The gatekeeper pH-/light-sensitive PDA coating was stimulated by the endogenous tumor acidic microenvironment and exogenous NIR laser to release doxorubicin (DOX). Thereafter, HMONs containing S-S bonds were reduced and degraded by endogenous glutathione (GSH), and the drug was further released rapidly to kill cancer cells. Importantly, the photothermal reagent indocyanine green (ICG) was always retained in the carrier, improving the effectiveness of photothermal therapy. The loaded Gd-doped silicon nanoparticles (SiGdNPs) combined with DOX and ICG led to multi-color fluorescence imaging in vitro and magnetic resonance imaging in vivo to realize targeted diagnosis and track drug distribution. The treatment results of tumor-bearing mice also proved the excellent synergistic therapy. It is believed that the multifunctional nanomaterials with dual mode imaging capability and targeted and controlled collaborative therapy would provide an alternative for accurate diagnosis and efficient treatment.

Preparation of glycan-oriented imprinted polymer coating Gd-doped silicon nanoparticles for targeting cancer Tn antigens and dual-modal cell imaging via boronate-affinity surface imprinting.

Early and accurate detection of breast cancer plays an important role in improving the survival rates of patients. In this work, we designed and synthesized the Gal-NAc-imprinted nanoparticles (GIPs) via boronate-affinity glycan-oriented surface imprinting strategy. Molecularly imprinted polymers (MIPs) were hybridized with fluorescent silicon nanoparticles (SiNPs) to target Tn antigens. However, the single fluorescent imaging mode is not conducive to obtaining accurate diagnosis, due to its poor tissue penetration. To resolve this obstacle, doping gadolinium (Gd) into SiNPs was adopted to emerge an extra significant magnetic resonance (MR) signal, achieving highly sensitive fluorescence imaging and magnetic resonance imaging (MRI) with high spatial resolution. GIPs had uniform particle size around 31.8 nm, and exhibited satisfactory fluorescence stability. The maximum adsorption capacity of GIPs was 1.15 µM/g with a high imprinting factor (IF) of 7.5. Confocal laser scanning microscope imaging revealed that the GIPs had excellent specific recognition ability with a low cytotoxicity. GIPs also showed an outstanding MR performance on cancer cells. Therefore, the synthesized nanoparticles had desirable performance in dual-model imaging to specifically target recognition cancer cells. It may have a tremendous potential in real biological samples.