Microfiber polarization modulation in response to protein induced self-assembly of functionalized magnetic nanoparticles

The response of microfiber polarization modulation (PM) to protein induced self-assembly of functionalized magnetic nanoparticles is tested. Microfiber is directly immersed in the magnetic fluid (MF) which contains carboxylated magnetic nanoparticles (CMNPs), without the modification of the microfiber surface. Self-assembly of CMNPs is induced after adding bovine serum albumin (BSA) into the MF. The relaxation time of the microfiber PM is prolonged, when an external magnetic field is applied or removed for a given period of time. The maximum polarization degree pmax and the difference Δp between the maximum and minimum polarization degree all decrease with the increase in the BSA concentration. The BSA concentration can be acquired based on the detection of pmax and Δp. Similarly, if specific molecular probes are prepared on the CMNPs to couple with the target proteins, new kinds of label free fiber biosensors can be expected. It can not only simplify the operation of microfiber but also reduce the cost of the signal analysis system.