Two-dimensional temperature-responsive chromatography using a poly(N-isopropylacrylamide) brush-modified stationary phase for effective therapeutic drug monitoring

Therapeutic drug monitoring (TDM) is an effective pharmacological approach for controlling drug concentration in a patient’s serum. Herein, a new two-dimensional chromatography system was developed using two poly(N-isopropylacrylamide) (PNIPAAm)-modified bead-packed columns for effective and safe drug monitoring. PNIPAAm-modified silica beads were prepared as packing materials using atom transfer radical polymerization of NIPAAm. The increase in the retention times of the drugs requiring TDM with increasing temperature, was attributed to enhanced hydrophobic interactions at elevated temperatures. The drugs and serum proteins were separated on the prepared column at 40 °C using an all-aqueous mobile phase. Differences in the hydrophobic interactions accounted for the elution of the serum proteins and drugs at short and long retention times, respectively, and a primary column was employed to separate the serum proteins and drugs. After eluting the serum proteins from the column, the drug was introduced into the secondary column, leading to a peak of its purified form and enabling determination of the drug concentration. Two-dimensional temperature-responsive chromatography can benefit TDM by allowing the drug concentration in the serum to be measured in all-aqueous mobile phases without sample preparation.