A competitive-type electrochemical immunosensor based on Ce-MOF@Au and MB-Au@Pt core-shell for nitrofuran metabolites residues detection.

A novel competitive-type electrochemical immunosensor based on square wave voltammetry (SWV) response was developed for the quantitative detection of 1-Aminohydantoin (AHD). To improve the conductivity of this immunosensor nanocomposites with good electrical conductivity were prepared as a signal amplification platform for the immunosensor by growing Au nanoparticles on the surface of Ce-based metal-organic framework (Ce-MOF). In addition, methylene blue (MB)-loaded Au@Pt and coating antigen (OVA-AHD) connected as a signal label. When the target was introduced, it competed with the coating antigen for the Ab, which led to a reduction in the number of signal probes bound to the Ab. The concentration of AHD can be determined by SWV detection of the MB signal loaded on the signal labels. Under optimal conditions, the wide linear range of 0.001-1000 µg /L and a low detection limit of 1.35 × 10-7 µg/L were achieved. Ultimately, the developed method displayed excellent specificity in practical applications, providing a promising probability to detect nitrofuran metabolites residues to guarantee food safety.

Antibody-directed metal-organic framework nanoparticles for targeted drug delivery.

Nanosized metal-organic frameworks (nMOFs) have shown great promise as high-capacity carriers for a variety of applications. For biomedicine, numerous nMOFs have been proposed that can transport virtually any molecular drug, can finely tune their payload release profile, etc. However, perspectives of their applications for the targeted drug delivery remain relatively unclear. So far, only a few works have reported specific cell targeting by nMOFs exclusively through small ligands such as folic acid or RGD peptides. Here we show feasibility of targeted drug delivery to specific cancer cells in vitro with nMOFs functionalized with such universal tool as an antibody. We demonstrate ca. 120 nm magnetic core/MOFs shell nanoagents loaded with doxorubicin/daunorubicin and coupled with an antibody though a hydrophilic carbohydrate interface. We show that carboxymethyl-dextran coating of nMOFs allows extensive loading of the drug molecules (up to 15.7 mg/g), offers their sustained release in physiological media and preserves antibody specificity. Reliable performance of the agents is illustrated with trastuzumab-guided selective targeting and killing of HER2/neu-positive breast cancer cells in vitro. The approach expands the scope of nMOF applications and can serve as a platform for the development of potent theranostic nanoagents. STATEMENT OF SIGNIFICANCE: The unique combination of exceptional drug capacity and controlled release, biodegradability and low toxicity makes nanosized metal-organic frameworks (nMOFs) nearly ideal drug vehicles for various biomedical applications. Unfortunately, the prospective of nMOF applications for the targeted drug delivery is still unclear since only a few examples have been reported for nMOF cell targeting, exclusively for small ligands. In this work, we fill the important gap and demonstrate nanoagent that can specifically kill target cancer cells via drug delivery based on recognition of HER2/neu cell surface receptors by such universal and specific tool as antibodies. The proposed approach is universal and can be adapted for specific biomedical tasks using antibodies of any specificity and nMOFs of a various composition.

A sensitive, colorimetric immunosensor based on Cu-MOFs and HRP for detection of dibutyl phthalate in environmental and food samples.

A sensitive and artful colorimetric immunosensor based on horseradish peroxidase (HRP) was designed by labelling metal-organic frameworks (Cu-MOFs) on the second antibody (Cu-MOFs@Ab2) as signal amplification for the detection of trace dibutyl phthalate (DBP). In this system, when Cu-MOFs@Ab2 was captured by antigen- primary antibody (Ab1) complex, tremendous Cu(II) will be released from Cu-MOFs in the presence of nitric acid (HNO3), and Cu(II) will be further reduced to Cu(I) after the addition of sodium ascorbate (SA), consequently, inhibiting the HRP to catalyse the colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxidized TMB (ox TMB). Under the optimized conditions, the limit of detection (LOD) was 1 µg L-1, which was almost 60 times lower than that using a conventional ELISA with the same antibody. In addition, our method showed good accuracy and reproducibility (recoveries of 87.73-103.4%; CV values of 1.46-5.95%) through a spike-recovery analysis. The proposed immunosensor indicated great potential for trace DBP determination from environmental and food samples.