Exploring fluorescent covalent organic frameworks for selective sensing of Fe^3＋

Covalent organic frameworks （COFs） have been widely applied in gas capture and separation, but the fluorescent property of COFs with large n-conjugated system tends to be underexplored. Here we report the fluorescent properties of several COFs including TaTa, DhaTab, TRITER- 1 and TzDa and the effect of metal ions of Na＋, Mg2＋, K＋, Ca2＋, Cu2＋, Zn2＋, Pb2＋, Ag＋, Cd2＋ and Fe3＋ on the fluorescence of these COFs. The results show that only Fe3＋ significantly quenched the fluorescence of the studied COFs. The possibility of the four COFs for selective sensing of Fe3＋ was demonstrated. The possible mechanism of the effect of Fe3＋ on the fluorescence of the COFs was based on the absorption competition quenching.

Self-quenched gold nanoclusters for turn-on fluorescence imaging of intracellular glutathione

Activatable fluorescence nanoprobes with only one kind of nanomaterial that can act as both the energy donor and acceptor simultaneously are scarce, but highly desirable for biosensing and bioimaging. In the present study, we reveal the preparation of self-quenched gold nanoclusters as a simple fluorescent turn-on probe for imaging intraceUular glutathione. The self-quenched gold nanoclusters are prepared via disulfide bond-induced aggregation of gold nanodusters. Compared with monodisperse gold nanoclusters, the developed self-quenched gold nanoclusters exhibit weak emission at 735 nm with a 40-nm red shift and much lower quantum yield （0.69%）. The prepared self-quenched gold nanodusters also possess good sensitivity and selectivity for glutathione detection, and are applicable for fluorescent turn-on imaging of intracellular glutathione.

A novel polymer-based nitrocellulose platform for implementing a multiplexed microfluidic paperbased enzyme-linked immunosorbent assay

Nitrocellose(NC)membranes,as porous paper-like substrates with high protein-binding capabilties,are very popular in the field of point-of-care immunoassays.However,generating robust hydrophobic structures in NC membranes to fabricate microfluidic paper-based analytical devices(μPADs)remains a great challenge.At present,the main method relies on an expensive wax printer In addition,NC membranes very easy to adhere during the printing process due to electrostatic adsorption.Herein,we developed a facile,fast and low-cost strategy to fabricateμPADs in NC membranes by screen-printing polyurethane acrylate(PUA)as a barrier material for defning flow channels and reaction zones.Moreover,hydrophobic barriers based on UV-curable PUA can resist various surfactant solutions and organic solvents that are generally used in immunoassays and biochemical reactions.To validate the feasibility of this PUA-based NC membrane for immunoassays in point-of-care testing(POCT),we further designed and assembled a rotational paperbased analytical device for implementing a multiplexed enzyme-linked immunosorbent assay(ELISA)in a simple manner.Using the proposed device under the optimal conditions,alpha fetoprotein(AFP)and carcinoembryonic antigen(CEA)could be identified,with limits of detection of 136 pg/mL and 174 pg/mL,respectively,which are below the threshold values of these two cancer biomarkers for clinical diagnosis.We believe that this reliable device provides a promising plaform for the diagnosis of disease based on ELISA or other related bioassays in limited setings or remote regions.

Porphyrinic metal-organic frameworks for biological applications

Porphyrins and their derivatives have been extensively applied in various fields owing to their photophysical and electrochemical properties.However,the drawbacks of self-aggregation and self-quenching in aqueous media limit their biological applications.Porphyrinic metal-organic frameworks(PMOFs)have attracted considerable attention because the introduction of porphyrins as organic linker into frameworks overcomes the limitations of free porphyrins.This review summarizes the strategies for the construction of PMOFs and their biological applications.The challenges and chances displayed by this class of emerging materials are also discussed.