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

Abstract

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.