| With the intensive study of protein technology, the development of efficient and rapid separation technology has become an important issue in the field of bio-engineering technology. Filtration, centrifugation, extraction, dialysis as conventional protein separation methods lack of selectivity of biomolecules, while electrophoresis and column chromatography require a lot of complicated pretreatment, ultimately, lead to the decrease of recovery. The development of magnetic nanoparticles provides an alternative way to solve the above problems. Because of its small size, large surface area, high surface activity and fast response to the magnetic field, it has a great application potential in the separation and purification of biological samples. Through proper surface modification, magnetic nanoparticles can bind the target protein with high selectivity which plays a significant role in the separation of protein.Base on the fruit of those good works, in this thesis, we prepared two novel functional magnetic composite particles which are dye affinity magnetic composite particles and thermosensitive magnetic composite particles, respectively. The new functional composite materials are systematically studied as magnetic carriers in the adsorption of protein. The main research can be summarized as follows:1. Maghemite nanoparticles (MNPs) were prepared by chemical co-percipitation process. Subsequently, the maghemite nanoparticles were coated by chitosan (CS-MNPs). Finally, Reactive Red 120 chosen as a dye ligand immobilized onto the chitosan coated maghemite nanoparticles via nucleophilic reaction. The product was characterized by SEM, FTIR, XRD, TGA and VSM. The results show that the new dye affinity magnetic composite particle is around 3μm And its'saturation magnetization is up to 13.6 emu/g. Moreover, the new dye affinity magnetic composite particle has several functional groups, such as sulfonic acid group, hydroxyl group and N-H in secondary amine on its surface. Thus, the novel magnetic materials show a good superparamagnetism and may be applied to protein separation, enzyme immobilization and many other biochemical industries.2. In this thesis, the prepared dye affinity magnetic composite particle was first used as an adsorbent. And its'the adsorption properties were studied systemically using bromelain as model protein. Moreover, the adsorption properties of MNPs and CS-MNPs were also investigated. The optimum adsorptive conditions of the dye affinity magnetic composite particle were studied as well. The results show that maximum adsorption of bromelain by the dye affinity magnetic composite particle occurres at pH 8.5. Compared the adsorption capacities of MNPs, CS-MNPs and the prepared dye affinity magnetic composite particles, the results indicate that the prepared dye affinity magnetic composite particles are better adsorbent, and the surface-modified can enhance the bromelain adsorption. Additionally, desorption, generation and recycle experiments were investigated. The adsorption capacity of the prepared dye affinity magnetic composite particle remains almost constant after the eight recycle experiments. Additionally, the adsorption mechanism of bromelain by the dye affinity magnetic composite particles was first investigated. Different experimental approaches, such as the adsorption isotherms, kinetics and thermodynamics studied, have been performed to examine the adsorption mechanism of bromelain by the dye affinity magnetic composite particle. Besides the macroscopic adsorption mechanism studied, the adsorption mechanism of bromelain by the dye affinity magnetic composite particle was also investigated by Fourier transforms infrared spectrometer (FTIR) and Zeta potential. The results suggest that the adsorption mechanism involved in the adsorption process could be mainly ascribed to collaborations of hydrophobic interaction, hydrogen bond and electrostatic attraction.3. Silica coating of maghetite nanoparticles (SiO2-MNPs) was performed according to the Stober process with some modification. The prepared magnetic silica composite particles were then encapsulated with a new thermosensitive polymer material—poly(N-vinylcaprolactan) via dispersion polymerization. A novel thermosensitive magnetic composite particle was successfully developed. The product was characterized by SEM, FTIR, XRD, VSM, TGA and DSC. The results suggest that thermosensitive magnetic composite particle has the shape of standard sphere with regular morphology and the size of which is around 5μm. And its'saturation magnetizations is up to 9.82 emu/g. The content of poly(N-vinylcaprolactan) in the prepared thermosensitive magnetic composite particle is 6.63%. Though reacted with the magnetic silica composite particle, the poly(N-vinylcaprolactan) still has a significant response to the temperature and its LCST is 33.4℃, close to the physiological temperature.4. Simultaneously, the new thermosensitive magnetic composite particle was chosen as a magnetic adsorbent and its adsorption capacity for protein was well studied using Bovine Serum Albumin (BSA) as template in this dissertation. The effect of adsorption time, pH, ionic strength and initial BSA concentration on adsorption was studied in detail. And the effect of temperature on adsorption and desorption capacities was also investigated. The results indicate that the maximum adsorption amount of BSA (76.49 mg/g) was achieved at pH 5.0 for 3 h containing BSA 1.6 mg/mL, and the optimum adsorption temperature is 35℃. Adsorption equilibrium studies show that bromelain adsorption data follow the Freundlich model well. The present work predicts that the prepared thermosensitive magnetic composite particles will have wide-ranging applications in the enrichment and separation of valuable proteins and many other industrial processes.
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