Study On Optical Biosensor For Tumor Marker Based On Conjugated Polyelectrolyte

Conjugated polyelectrolytes have attracted much attention in chemical and biological sensorsdue to its unique optical properties. In this issue, several biosensors with high sensitivity, selectivityand stability are designed for the detection of tumor markers using conjugated polyelectrolytes assensing materials.. Firstly, a novel thronbim sensor is designed based on the FRET between PFEP and splitaptamer fragments. The thronbim induces a conjunction of two split aptamer fragments to formG-quadruplex, and the distance between the PFEP and dye increased due to protein’s large size,leading to a low FRET signal. In the absence of thronbim, DNA/PFEP complexes is formed viastrong electrostatic interactions, resulting in efficient FRET between two fluorophores. This methodis highly selective, simple, rapid, and with the detection limit of2nM in buffer systerm.Secondly, conjugated polyelectrolyte brushe (CPB) is introduced to optical detection of tumormarkers and a “turn-off” alpha-fetoprotein (AFP) sensor based on electronic/energy transfer (ET)is developed using the powerful target capture capabilities of CPB. When AFP antigen is added tothe ThNI solution, the fluorescence is quenched. However, when a control protein is added, thefluorescence spectra of ThNI doesn’t change. The limit of detection in buffer and mixed proteinsysterm is1nM and2nM, respectively.Thirdly, a “turn-on” solid AFP biosensor is designed based on conjugated polyelectrolyte andmagnetic nanoparticles. Ab-MNP acts as capture probe and FITC-anti-AFP act as signal probe. Inthe presence of AFP, the AFP binds with the signal probe and the capture probe, formingimmunomagnetic-beads. After magnetic separation and denaturation, solution with FITC-anti-AFPis collected and effective FRET occurs with the addition of PFEP. In contrast, in the absence of AFP,immunomagnetic beads doesn’t form, and solution after magnetic separation and denaturation iswithout FITC-anti-AFP, FRET does not occur with the addition of PFEP.Finally, a PSA sensor is established utilizing polyelectrolyte brush (PPE-B) as sensing materialsand fluorescein-labeled peptides as signal probe. The PPE-B with a large positive charges interactwith negative charged peptides by electrostatic interaction, which results in efficient FRET. In thepresence of PSA, the peptides are recognized and hydrolyzed by PSA, resulting in the increase ofdistance between PPE-B and peptides, then FRET efficiency decreases.