Monitoring binding affinity between drug and α1-acid glycoprotein in real time by Venturi easy ambient sonic-spray ionization mass spectrometry

• V-EASI MS technique is applied to analyze drug–AGP binding affinity.
• The mechanism can realize real time online analysis.
• Binding rate is proposed to quantify the binding affinity.
• Binding rate of any time during the binding process can be calculated.

A new approach for monitoring the binding affinity between drugs and alpha 1-acid glycoprotein in real time was developed based on a combination of drug–protein reaction followed by Venturi easy ambient sonic-spray ionization mass spectrometry determination of the free drug concentrations. A known basic drug, propranolol was used to validate the new built method. Binding constant values calculated by venturi easy ambient sonic-spray ionization mass spectrometry was in good accordance with a traditional ultrafiltration combined with high performance liquid chromatography method. Then six types of basic drugs were used as the samples to conduct the real time analysis. Upon injection of alpha 1-acid glycoprotein to the drug mixture, the ion chromatograms were extracted to show the changes in the free drug concentrations in real time. By observing the drop-out of six types of drugs during the whole binding reaction, the binding affinities of different drugs were distinguished. A volume shift validating experiment and an injection delay correcting experiment were also performed to eliminate extraneous factors and verify the reliability of our experiment. Therefore, the features of Venturi easy ambient sonic-spray ionization mass spectrometry (V-EASI-MS) and the experimental results indicate that our technique is likely to become a powerful tool for monitoring drug–AGP binding affinity in real time.

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