Blood plasma contains an abundance of proteins, mostly albumins, globulins and fibrinogen at high concentration, up to 50 g/L. These proteins make the detection of small analytes in the plasma difficult, especially at low concentrations and therefore must be removed prior to some analysis such as LC-MS. Current methods for bulk removal of proteins call for the addition of precipitants in solution followed by centrifugation and withdrawal of the supernatant for further analysis while the protein cake is discarded. However, this process can take a significant amount of time and, crucially, leads to the dilution of the blood plasma, making the detection of low concentration analytes more difficult.<br/>Here, we implement a new strategy for bulk removal of proteins that uses hydrogels to sequester proteins. Using albumin in phosphate buffer saline solution as a model system, we show that albumin partition strongly into positively charged hydrogels. By absorbance measurement and confocal imaging, we quantify the partition coefficient of albumin in hydrogels with tunable properties and the timescale of this phenomenon. We provide evidence supporting that simple electrostatic interaction are not sufficient to explain the strong partitioning of albumin in charged hydrogels. We also use various types of fluorescent albumin to show that this partitioning is depending on the molecular details of this protein. We then optimize the timescale of the partitioning by changing the dimension of the hydrogels. Finally, we discuss practical implication of this result in blood sample analysis, drug delivery and the potential integration of such a technology on the widely used 96 well plate.

Bulk removal of proteins from plasma using hydrogels

ACS Spring 2022

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