Construction Of New Type Magnetic Biosensor Based On MnO₂ Nanoassembly

Highly sensitive and reliable detection of low concentrations of targets in complex samples has become increasingly important in not only scientific research but also clinical diagnosis,which leads to the development of nanoparticles-mediated analytical methods.Among these nanoparticles-mediated analysis,magnetic nanoparticles-mediated magnetic relaxation switching sensing have drawn more and more attentions in biochemical analysis.In conventional magnetic relaxation switching,the magnetic nanoparticles-based probes are conjugated to the surface of targets,and the state of probe changes from dispersed to aggregated,resulting in the change of transverse relaxation time?T₂?of proton of surrounding water molecules.Nevertheless,current magnetic relaxation switching sensors for detection of trace targets in complex samples still suffer from limitations in terms of relatively low sensitivity and poor stability.To meet this challenge,we developed a longitudinal relaxation time?T₁?-based nanosensor by using Mn²⁺released from the reduction of a MnO₂ nanoassembly that can induce the change of T₁,and thus can greatly improve the sensitivity and overcome the“hook effect”of conventional magnetic relaxation switching sensors.Through the specific interaction between antigen and the antibody-functionalized MnO₂ nanoassembly,the T₁ signal of Mn²⁺released from the nanoassembly is quantitatively determined by the antigen,which allows for highly sensitive detection of targets.We employed this T₁ sensor for procalcitonin detection in both buffer and real serum samples.This T₁ sensor not only retains the advantage of conventional MRS but also greatly improves its sensitivity and stability,which broadens the applicability of magnetic biosensors and has great potential for applications in early diagnosis of disease biomarkers.However,this T₁ sensor currently is incapable of simultaneous determination of multiple targets in the same sample.In future work,we will try to combine the T₁-based assay with microfluidic technology to realize automatic and multiplex analysis.In addition,we will keep on studying the controllable assembly of MnO₂nano-assembly in depth.