Development Of New Superparamagnetic Nanospheres With Low Nonspecific Protein Adsorption And High Sensitivity For Immunoassay

Superparamagnetic nanospheres are widely used in many areas, such as biology, medical science, food safety due to its unique superparamagnetism and properties of ultrafine particles. In order to enhance the detecting efficiency, sensitivity and reliability of the immunoassay in which magnetic nanospheres are applied, the surface of magnetic nanospheres is modified with nonfouling materials, that can reduce the interference of the protein adsorption, and lower detecting errors.In this work, the initiator and nonfouling material monomer (CBAA) were synthesized and the magnetic nanospheres were modified with polyCBAA via SI-ATRP(Surface-Initiated Atom Transfer Radical Polymerization). The protein adsorption of the modified and un-modified magnetic nanospheres was detected by enzyme-linked immunosorbent assay (ELISA). At last, both of the magnetic nanospheres with and without pCB AA brush were grafted anti-β-hCG antibody to detect hCG in PBS and50%fetal bovine serum (FBS). From this work, we obtained following results.1) The magnetic nanospheres with pCBAA brush have quite excellent nonfouling capability, the nonspecific protein adsorption is about5%of the un-modified magnetic nanospheres.2) The non-specific protein adsorption of the magnetic nanospheres is related to the thickness of the polyCBAA brush. By varying the reaction conditions, it is found that when the brush thickness approaches22.2±3.2nm, the value of the non-specific protein adsorption lower to4.53±0.9%of un-modified magnetic nanospheres.3) The immune magnetic nanospheres modified with pCBAA brush exhibit better detecting linearity and lower detecting errors than un-modified nanospheres in immunoassay, and excellent consistent response to antigen in PBS and50%fetal bovine serum (FBS), which is far less variable than the response of un-modified immune magnetic nanospheres.4) The immune magnetic nanospheres with polyCBAA brush still have good detecting linearity and sensitivity in50%fetal bovine serum (FBS) and low concentration of hCG. The detection limit by these immune nanospheres is one order of magnitude lower than by conventional ELISA.