Adsorption and Separation of Trypsin Using Deep Eutectic Solvent-Functionalized Magnetic Polydopamine

Five deep eutectic solvent (DES)-functionalized magnetic polydopamine (MPDA) composites were designed and synthesized via an ultrasound-assisted method, and subsequently integrated with magnetic solid-phase adsorption (MSPA) for the efficient adsorption of trypsin. Among them, MPDA@[ChCl][EG], functionalized with a DES composed of choline chloride and ethylene glycol, exhibited the highest adsorption efficiency. The morphology, magnetic responsiveness, and functional group distribution of MPDA@[ChCl][EG] were characterized by transmission electron microscopy, vibrating sample magnetometry, and fourier-transform infrared spectroscopy. Single-factor optimization experiments were conducted to investigate the key parameters affecting trypsin adsorption. Under optimal conditions, MPDA@[ChCl][EG] achieved an adsorption capacity of 338.99 mg·g −1 for trypsin, with an equilibrium time of 60 min. The adsorption behavior was well described by the Langmuir isotherm and pseudo-second-order kinetic models, indicating monolayer chemisorption. Furthermore, MPDA@[ChCl][EG] was successfully applied to the adsorption and separation of trypsin from a complex biological sample (bovine pancreas crude extract). This strategy of constructing magnetic adsorbents using green DESs and MPDA offers new possibilities for protein adsorption under mild conditions.