DVB-cross-linked latex microspheres to uniformly host Eu(III) chelates with moderate swelling capacity for high performance quantitative LFIA strips.

Eu-complex-swollen polystyrene (PS) fluorescent microspheres have attracted considerable attention in the field of lateral flow immunoassay (LFIA) bio-detection. However, the excessive swelling and induced concentration quenching effect of Eu complexes often deteriorate their fluorescence intensity and fluorescence efficiency. To address this issue, herein, we synthesized Eu(TTA)3(TPPO)2 and introduced divinylbenzene (DVB) to fabricate three-dimensionally cross-linked PS-DVB-Eu microspheres in order to obtain a moderate swelling capacity of the Eu complexes without obvious fluorescence concentration quench. This cross-linked structure effectively promotes the homogeneous distribution of swollen Eu(TTA)3(TPPO)2 in PS-DVB-Eu microspheres. This thus resulted in improved fluorescence properties with a high internal quantum efficiency (IQE) of 52.36% and a lifetime of 539 μs. The fluorescence of the cross-linked PS-DVB-Eu microspheres was 3.85 times stronger than that of the non-crosslinked PS-Eu microspheres. The cross-linked structures also helped the PS-DVB-Eu microspheres maintain a relatively high zeta potential and a large surface carboxyl concentration. These merits support PS-DVB-Eu microspheres in obtaining an enhanced lateral flow immunoassay (LFIA) performance, including an LOD of 0.08 ng mL-1 and a CV value of less than 7.34% on detecting C-reactive protein (CRP). This demonstrates that cross-linked PS-DVB-Eu microspheres are promising materials for high performance LFIA point-of-care testing techniques.