Preparation of a poly(3'-azido-3'-deoxythymidine-co-propargyl methacrylate-co-pentaerythritol triacrylate) monolithic column by in situ polymerization and a click reaction for capillary liquid chromatography of small molecules and proteins.

Combining free radical polymerization with click chemistry via a copper-mediated azide/alkyne cycloaddition (CuAAC) reaction in a "one-pot" process, a facile approach was developed for the preparation of a poly(3'-azido-3'-deoxythymidine-co-propargyl methacrylate-co-pentaerythritol triacrylate) (AZT-co-PMA-co-PETA) monolithic column. The resulting poly(AZT-co-PMA-co-PETA) monolith showed a relatively homogeneous monolithic structure, good permeability and mechanical stability. Different ratios of monomers and porogens were used for optimizing the properties of a monolithic column. A series of alkylbenzenes, amides, anilines, and benzoic acids were used to evaluate the chromatographic properties of the polymer monolith in terms of hydrophobic, hydrophilic and cation-exchange interactions, and the results showed that the poly(AZT-co-PMA-co-PETA) monolith exhibited more flexible adjustment in chromatographic selectivity than that of the parent poly(PMA-co-PETA) and AZT-modified poly(PMA-co-PETA) monoliths. Column efficiencies for toluene, DMF, and formamide with 35,000-48,000 theoretical plates per m could be obtained at a linear velocity of 0.17 mm s(-1). The run-to-run, column-to-column, and batch-to-batch repeatabilities of the retention factors were less than 4.2%. In addition, the proposed monolith was also applied to efficient separation of sulfonamides, nucleobases and nucleosides, anesthetics and proteins for demonstrating its potential.

Structural analysis and allergenicity assessment of an enzymatically cross-linked bovine α-lactalbumin polymer.

Enzymatic cross-linking is frequently used in bio-processing of dairy products since it could change the physiochemical and functional characterization. In our study, bovine α-lactalbumin was cross-linked by polyphenol oxidase from Agaricus bisporus and the changes in the structure, digestibility and allergenicity of α-lactalbumin were explored after cross-linking, and the structural alterations of the polymers were analyzed by circular dichroism spectroscopy, ultraviolet absorption spectroscopy and fluorescence spectroscopy. The digestibility of cross-linked α-lactalbumin was evaluated by simulated digestion in vitro. After that, the allergenicity of α-lactalbumin polymers was evaluated by detection of the specific IgE binding ability using an animal model. The results showed that the secondary and tertiary structures of various α-lactalbumin polymers exhibited a significant variation compared with those of untreated α-lactalbumin, and the cross-linked α-lactalbumin was relatively less susceptible to digestion. Moreover, the allergenicity of cross-linked polymers decreased significantly. These results suggested that there was a direct correlation between a loss of an α-helix and IgE binding to α-lactalbumin, which indicated that enzymatic cross-linking might be an efficient approach to reduce the allergenicity of bovine α-lactalbumin.

Saw-Toothed Microstructure-Based Flexible Pressure Sensor as the Signal Readout for Point-of-Care Immunoassay.

A saw-toothed microstructure-based flexible pressure sensor was designed as the signal readout for point-of-care (POC) immunoassay of carcinoembryonic antigen (CEA). In this portable POC bioassay, the sandwich-type immunoreaction was first carried out to capture the target on a microplate, which simultaneously introduced the platinum nanoparticles (PtNPs). Upon adding hydrogen peroxide (H2O2), the pressure as the bridge between the molecular recognition event and detectable signal was increasing rapidly, resulting from the decomposition of H2O2 accelerated by PtNPs. Meanwhile, a flexible pressure sensor was fabricated with high sensitivity; the ability of the pressure response was dramatically improved by adopting the saw-toothed microstructure. By coupling with the pressure sensor, the pressure change could be monitored in real time to achieve the portable detection of CEA. Under the optimum conditions, the proposed pressure-based bioassay presented good sensing performance within 0.1-40 ng/mL at a detection limit of 87 pg/mL. The reproducibility, precision, and accuracy provided by the method were also studied and satisfied.

Ti3C2 MXene quantum dot-encapsulated liposomes for photothermal immunoassays using a portable near-infrared imaging camera on a smartphone.

Methods based on the photothermal effect (a common phenomenon in nature) have been widely applied in different fields; however, their application in bioanalysis has lagged behind. Herein, we designed a near-infrared (NIR) photothermal immunoassay for the qualitative or quantitative detection of prostate-specific antigen (PSA) using titanium carbide (Ti3C2) MXene quantum dot (QD)-encapsulated liposomes with high photothermal efficiency. This system involves a sandwich-type immunoreaction and photothermal measurements. Ti3C2 MXene QDs were utilized as innovative photothermal signal beacons and were encapsulated in liposomes for the labeling of the secondary antibody. The assay was carried out by coupling a low-cost microplate with a homemade 3D printed device. Under NIR-laser irradiation, the Ti3C2 MXene QDs converted the light energy into heat, and a shift in temperature corresponding with the analyte concentration was obtained on a handheld thermometer. Under optimal conditions, the Ti3C2 MXene QD-based photothermal immunoassay exhibited a dynamic linear range from 1.0 ng mL-1 to 50 ng mL-1 with a limit of detection of 0.4 ng mL-1 for PSA detection. Also, we constructed portable equipment using a portable near-infrared imaging camera to collect visual thermal data for the semi-quantitative analysis of the target PSA within 3 min. The specificity, reproducibility and accuracy of the photothermal immunoassay were acceptable. Importantly, our strategy opens new opportunities for protein point-of-care (POC) testing and biosecurity diagnostics.

Metal-organic framework-coated stainless steel fiber for solid-phase microextraction of polychlorinated biphenyls.

For solid phase microextraction (SPME), effective immobilization of sorbent on a stainless steel fiber surface is very essential. But, it still remains challenging because the chemical inertness of stainless steel fiber. In this work, chemical bonding method was introduced to fabricate a series of metal-organic frameworks (MOFs)-coated stainless steel fibers, and some representative MOFs (ZIF-90 (Zn), MOF-199 (Cu), MIL-101 (Cr), MOF-5 (Zn))-coated stainless steel fibers were successfully synthesized. Such strategy can noticeably increase the mechanical and chemical stability, and prolong the service lifetime due to it combine the advantages of stainless steel fiber and chemical bonding method. The stability of MOF-ZIF-90 (Zn)-coated stainless steel fibers which were preparated by different methods (chemical bonding method, adhesive method and deposition method) were studied, and results showed the chemical bonding method proved the best stability. Based on the ZIF-90 (Zn)-coated fiber, the SPME-GC-MS method was developed for detecting traces of polychlorinated biphenyls (PCBs) and satisfactory results were obtained. The linear ranges were 0.01-600 ng L-1 and the coefficient of determination was higher than 0.993. The limits of detection for the PCBs were 0.0013-0.053 ng L-1. The recoveries for the spiked PCBs in the Minjiang water, soil and vegetable oil samples were in the range of 85.9-105.8%. The extraction capacity of the ZIF-90 (Zn)-coated stainless steel fiber prepared by chemical bonding method did not show measurable change under different temperatures or organic solvents for up to 5 days.

Magnetic porous ß-cyclodextrin polymer for magnetic solid-phase extraction of microcystins from environmental water samples.

Microcystins (MCs) are cyclic heptapeptide toxins and tumor promoters produced by cyanobacteria, which threaten the health of humans. In this study, magnetic porous ß-cyclodextrin polymer (Fe3O4@SiO2@P-CDP) was synthesized and characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry, Fourier transform infrared spectrometry, X-ray diffraction, nitrogen adsorption porosimetry and vibrating sample magnetometer. The synthesized Fe3O4@SiO2@P-CDP particles were then used for magnetic solid-phase extraction (MSPE) of MCs from environmental water samples, and exhibited excellent extraction performance, especially for MC-RR. Coupled with high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS), a simple, efficient and sensitive method for determination of trace levels of MCs was established. After the optimization of conditions, wide linear ranges (2.0-1000pgmL-1), good linearity (r2≥0.9996) and acceptable repeatability (RSD≤9.4%, n=5) were obtained. The limits of detection (LODs, S/N=3) and limits of quantification (LOQs, S/N=10) for three MCs (MC-LR, MC-RR and MC-YR) were in the range of 1.0-2.0pgmL-1 and 2.0-5.0pgmL-1, respectively. Typical water samples were analyzed by the developed method, and trace levels of MC-LR and MC-RR were detected. The results demonstrate that the developed method has great potential for the determination of MCs in complicated matrix.