Preparation of dyed polymer microspheres by a physical-chemical dual-binding method and their application in lateral flow immunoassay.

Lateral flow immunoassay (LFIA) has shown great competitiveness in point-of-care testing due to its flexibility and simplicity. Dyed polymer microspheres are one of the most widely used marker particles for signal presentation as they are very convenient for visual interpretation, which is one of the most attractive features of LFIA. The color intensity, as the most critical factor, is directly related to the visual effect. In this work, a physical-chemical dual-binding strategy was proposed for the preparation of functionalized dyed microspheres. Bifunctional seed microspheres were synthesized by introducing 4-vinylbenzyl chloride (VBC) into the soap-free emulsion polymerization process, and the effective immobilization of dyes inside and on the surface of the polymer microspheres was achieved by covalent bonding and swelling methods. The microspheres were characterized by SEM, FT-IR spectroscopy and UV-vis spectroscopy. The results showed that the microspheres containing VBC were spherical with an average particle size of 300 nm. When the microspheres were prepared by adding 10 wt% VBC relative to the total monomer, the immobilization amount of 1-[[4-[(dimethylphenyl)azo]dimethyl phenyl]azo]-2-naphthol (Red-27) was increased to 180 mg g-1, which was 1.8 times that of the microspheres without VBC. The resulting nanomaterials were successfully used to establish a lateral flow immunoassay for the detection of COVID-19 virus N protein. The linear response concentration range was 2.64-87.84 COI, and the detection limit was 14.95 COI.

Fabrication of Yolk-Shell Fe3O4@NiSiO3/Ni Microspheres for Efficient Purification of Histidine-Rich Proteins.

Magnetic materials perform well in the purification of histidine-rich proteins (His-proteins). In this work, a facile fabrication of yolk-shell magnetic Fe3O4@NiSiO3/Ni microspheres for the efficient purification of His-proteins has been reported. Yolk-shell Fe3O4@NiSiO3 microspheres were prepared via hydrothermal reaction. Then Ni nanoparticles (NPs) were loaded on Fe3O4@NiSiO3 microspheres after the adsorption and in situ reduction of nickel acetylacetonate. The yolk-shell Fe3O4@NiSiO3/Ni microspheres had a hierarchical flower-like structure and large cavities. The size of the cavity depended on the reaction time. This indicated that the microspheres had a large specific surface area for loading of more Ni NPs, which was crucial to the high His-protein adsorption capacity of Fe3O4@NiSiO3/Ni microspheres. Fe3O4@NiSiO3/Ni microspheres had a high adsorption capacity for bovine hemoglobin (BHb, 2822 mg/g), which was better than the values of other His-protein adsorbents. Fe3O4@NiSiO3/Ni microspheres still had a high BHb separation efficiency after seven separation cycles, indicating its good reusability and stability. Therefore, the as-prepared bifunctional yolk-shell Fe3O4@NiSiO3/Ni microspheres exhibited great practical application value for His-protein purification.

Reshaping of pipette tip: A facile and practical strategy for sorbent packing-free solid phase extraction.

Pipette tip-based solid phase extraction (PT-SPE) has been proved to be an effective and user-friendly separation technique due to its miniaturized procedure and practical convenience. However, the vast majority of existing PT-SPE devices consist of a filter-sorbents-filter sandwich structure, which may suffer the unforeseen risk of sorbents leakage caused by the looseness of filters. More importantly, many high-capacity nanosorbents with particle size smaller than pore size of filters are unavailable. Thus, sorbent packing-free and sample low-consumption PT-SPE could be a more robust strategy for separation and detection, but such a possibility has not been explored yet. Herein we report a tubing reshaping strategy for facile fabrication of sorbent packing-free PT-SPE devices. Three types of reshaped PTs, namely stretched tube-like, self-crimping and filter in-built PTs, were fabricated via simple heating and stretching operations. The reshaped PTs exhibited flexible surface chemical post-modification. The SPE process was directly performed in reshaped PTs with an obviously enhanced extraction efficiency compared to once-shaping PTs while no need of packing sorbents. Extraction of nucleosides from human urine by boronic acid-functionalized reshaped PTs was demonstrated. Our findings technically renovate the structural composition of PT-SPE devices. As PTs are inexpensive and high-plasticity, the sorbent packing-free SPE scheme presented herein could find more promising applications and provides a new perspective for design and fabrication of novel sorbent packing-free SPE devices.