A novel polymeric ionic liquid, poly(3-n-dodecyl-1-vinylimidazolium) bromide (poly(C12vim)Br), is prepared via solution polymerization. The poly(C12vim)Br exhibits excellent adsorption performance toward hemoglobin in the presence of other protein species. It is shown that favorable adsorption of hemoglobin is achieved at pH 8.0, and the variation of ionic strength has virtually no effect on the adsorption of hemoglobin at a NaCl concentration up to 0.4 mol L−1. A maximum adsorption capacity of 205.4 mg g−1 is derived for hemoglobin. An adsorption efficiency of 93.8% is obtained by processing 80 μg mL−1 of hemoglobin in 1.0 mL of solution with 2 mg of poly(C12vim)Br, and afterwards the use of 1.0 mL of sodium dodecyl sulfate (SDS, 0.5%, m/v) provides a recovery of ca. 86.3%. It is indicated that the process of adsorption/desorption causes a slight conformational change for hemoglobin, while its structure remains predominantly α-helix. The poly(C12vim)Br has been used for the adsorption of hemoglobin from complex biological sample matrixes, e.g., human whole blood, and the favorable separation and purification performance is demonstrated by SDS-PAGE assays.

Polymeric ionic liquid (PIL), poly(1-vinyl-3-ethylimidazolium bromide) (P(ViEtIm+Br−)), modified reduced graphene oxide (rGO) nanosheets (PIL–rGO) are prepared during the reduction process using hydrazine hydrate. The as-prepared PIL–rGO is further self-assembled onto the surface of SiO2 nanoparticles through electrostatic interactions as demonstrated by TEM & SEM images. The obtained PIL–rGO@SiO2 nano-hybrid exhibits highly selective adsorption toward acidic protein, i.e., ovalbumin (Ova) as a model in the present case. The strong electrostatic attractions and π–π interactions between Ova and the nano-hybrid are the main driving forces for protein adsorption. An adsorption efficiency of ca. 95% is achieved for 150 mg L−1 Ova in a 4 mM B–R buffer at pH 5, along with an ultra-high adsorption capacity of ca. 917.4 mg g−1 as compared to those adsorbents for similar purposes. The adsorbed Ova could be effectively recovered from the surface of the nano-hybrid by using a 0.4% (w/v) SDS solution, giving rise to a recovery of ca. 70%. The practical applicability of the PIL–rGO@SiO2 nano-hybrid is demonstrated by selective isolation and removal of Ova from a complex biological sample matrix, i.e., chicken egg white.

A novel dual-ionic liquid (IL) microemulsion system is developed with IL 1-decyl-3-methylimidazolium bromide (DmimBr) as the surfactant and IL 1-butyl-3-methylimidazolium hexaflourophosphate (BmimPF6) as a substitute for organic solvent. The phase diagram of this dual-IL microemulsion system clearly shows the formation of a single phase within a wide range of BmimPF6 (1.76–98.3%, wt) and in the presence of an appropriate amount of DmimBr and water. The microemulsion is characterized by means of FT-IR spectra, dynamic light scattering and molecular probe. The dual-IL microemulsion system has been demonstrated to be effective for the extraction of proteins, and exhibited an obvious improvement in extraction efficiency for hemoglobin in comparison with pure BmimPF6. When 100 μL microemulsion is used to extract 100 μg mL−1 of proteins in an equal volume of sample solution, high selective extraction of hemoglobin (Hb) has been observed at pH 5. This might be attributed to the coordination interaction between the heme group of Hb and the imidazolium cationic moiety in the ionic liquids. Hb transferred into the microemulsion can be readily recovered by back extraction with Britton–Robinson buffer at pH 12, giving rise to a recovery of 55.6%. The dual-IL microemulsion system is practically applied to the isolation of Hb from human whole blood and the SDS-PAGE indicates that hemoglobin has been selectively isolated from human blood in the presence of co-existing protein species.

A hydrophilic ionic liquid (methylimidazolium chloride, NmimCl)-polyvinyl chloride ionomer (NmimCl-PVC) was prepared by immobilizing and confining N-methylimidazole onto PVC chains. The NmimCl-PVC ionomer exhibits a 4-fold enhancement on the fluorescence intensity with respect to that of NmimCl, attributing to the confinement of ionic liquid by the PVC chain. The fluorescence is excitation-dependent with a maximum at λem 430 nm when excited at 325 nm. In addition, the fluorescence intensity of NmimCl-PVC ionomer increases remarkably with the loading ratio of N-methylimidazole in the range of 4.3–15.1%. The fluorescence quantum yield and lifetime were derived to be 0.112/7.1 ns for the NmimCl-PVC ionomer and 0.063/8.8 ns for NmimCl. Furthermore, hemoglobin is selectively adsorbed by NmimCl-PVC and causes significant fluorescence quenching of the ionomer via dynamic quenching and energy transfer between NmimCl-PVC and hemoglobin. A solid surface fluorimetric procedure was developed for surface adsorption and preconcentration of hemoglobin followed by in situ detection. A linear dynamic range of 0.3–26.2 μg mg–1 is achieved with a detection limit of 0.1 μg mg–1. Regarding hemoglobin in aqueous solution, the linear range 5–300 μg mL–1 is achieved along with a detection limit of 2 μg mL–1.Keywords: fluorescence enhancement; hemoglobin; immobilization/confinement; ionic liquid;