Removal of urea from urea-rich protein samples using metal ions in amicrofluidic device

Urea is commonly used to lyse cultured cells and solubilize proteins froma biological source. In this study, after extracting biomolecules using alysis buffer that included urea for an effective cleaning of protein from aurea-rich protein sample, a five-flow microfluidic desalting system wasapplied using the metal ions of Mn super(2+), Zn super(2+) and Fe super(3+), which haveurea affinity-capturing properties. This device effectively removed urea fromthe sample phase of the microfluidic channel via the diffusion, with adifference of the concentration from the sample flow to both sides of thebuffer flow, and an affinity of metal ions into the urea between the bufferphase and the affinity phase. The removal efficiency for the urea was 67, 64,and 63%, with concentrations of 50 mM Mn super(2+), 10 mM Zn super(2+), and 5 mMFe super(3+) metal ions in the affinity phase, respectively. In addition, proteinafter desalting with the microfluidic device was improved to more than 10% ofthe relative activity, with a significant improvement of the signal of massspectrum shown by MALDI-MS.