Thermo-Magnetoresponsive Dual Function Nanoparticles: An Approach for Magnetic Entrapable-Releasable Chitosan

Magnetic polymeric nanoparticles can be used for selective binding in a magnetic field. However, as the magnetic nanoparticles (MAG) are stabilized with polymers, the separation of the MAG from the polymer chains after use is difficult. This work proposes a combination of a thermoresponsive polymer with MAG allows for the as-desired simple removal of MAG from the polymer chains. For this, chitosan (CS) was conjugated with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and antibody (Ab) together with the physisorbed MAG as a thermo-magneto dual functional material. The key synthesis steps are (i) radical polymerization of NIPAM in the presence of mercaptoacetic acid so that the PNIPAM obtained contains terminal carboxylic acid groups (PNIPAM-COOH), (ii) the CS-N-hydroxysuccinamide water-based system that allows conjugation of CS with PNIPAM-COOH in water at room temperature, and (iii) the weak interaction between MAG and the CS chain. As a model application, CS is conjugated with the antirecombinant Leptospirosis Ab (rLipL32) to allow the selective binding and collection of the target antigen under the dual functions. This is the first demonstration of a simple but effective solution for MAG exclusion from the target molecules and will be practical for diverse applications, such as diagnosis, sensors, filtration, etc.