Dynamic Mass Transfer of Hemoglobin at the Aqueous/Ionic-Liquid
Interface Monitored with Liquid Core Optical Waveguide
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Abstract
Protein
transfer from aqueous medium into ionic liquid is an important
approach for the isolation of proteins of interest from complex biological
samples. We hereby report a solid-cladding/liquid-core/liquid-cladding
sandwich optical waveguide system for the purpose of monitoring the
dynamic mass-transfer behaviors of hemoglobin (Hb) at the aqueous/ionic
liquid interface. The optical waveguide system is fabricated by using
a hydrophobic IL (1,3-dibutylimidazolium hexafluorophosphate, BBimPF<sub>6</sub>) as the core, and protein solution as one of the cladding
layer. UV–vis spectra are recorded with a CCD spectrophotometer
via optical fibers. The recorded spectra suggest that the mass transfer
of Hb molecules between the aqueous and ionic liquid media involve
accumulation of Hb on the aqueous/IL interface followed by dynamic
extraction/transfer of Hb into the ionic liquid phase. A part of Hb
molecules remain at the interface even after the accomplishment of
the extraction/transfer process. Further investigations indicate that
the mass transfer of Hb from aqueous medium into the ionic liquid
phase is mainly driven by the coordination interaction between heme
group of Hb and the cationic moiety of ionic liquid, for example,
imidazolium cation in this particular case. In addition, hydrophobic
interactions also contribute to the transfer of Hb