Quantitative Analysis of HIV-1 Protease Inhibitors in Cell Lysates Using MALDI-FTICR Mass Spectrometry

• Published in: Analytical chemistry (Washington) 2008-05, Vol.80 (10), p.3751-3756
• Main Authors: van Kampen, Jeroen J. A, Burgers, Peter C, de Groot, Ronald, Osterhaus, Albert D. M. E, Reedijk, Mariska L, Verschuren, Esther J, Gruters, Rob A, Luider, Theo M
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Cells, Cultured; Chemistry; Exact sciences and technology; HIV; HIV Protease Inhibitors - analysis; Human immunodeficiency virus; Human immunodeficiency virus 1; Mass spectrometry; Prescription drugs; Proteases; Proteins; Sensitivity and Specificity; Spectrometric and optical methods; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; Spectroscopy, Fourier Transform Infrared - methods
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac702072c

In this report we explore the use of MALDI-FTICR mass spectrometry for the quantitative analysis of five HIV-1 protease inhibitors in cell lysates. 2,5-Dihydroxybenzoic acid (DHB) was used as the matrix. From a quantitative perspective, DHB is usually a poor matrix due to its poor shot-to-shot and poor spot-to-spot reproducibilities. We found that the quantitative precisions improved significantly when DMSO (dimethylsulfoxide) was added to the matrix solution. For lopinavir and ritonavir, currently the most frequently prescribed HIV-1 protease inhibitors, the signal-to-noise ratios improved significantly when potassium iodide was added to the matrix solution. The mean quantitative precisions, expressed as % relative standard deviation, were 6.4% for saquinavir, 7.3% for lopinavir, 8.5% for ritonavir, 11.1% for indinavir, and 7.2% for nelfinavir. The mean quantitative accuracies, expressed as % deviation, were 4.5% for saquinavir, 6.0% for lopinavir, 5.9% for ritonavir, 6.6% for indinavir, and 8.0% for nelfinavir. The concentrations measured for the individual quality control samples were all within 85–117% of the theoretical concentrations. The lower limits of quantification in cell lysates were 4 fmol/µL for saquinavir, 16 fmol/µL for lopinavir, 31 fmol/µL for ritonavir, and 100 fmol/µL for indinavir and nelfinavir. The mean mass accuracies for the protease inhibitors were ⩽0.28 ppm using external calibration. Our results show that MALDI-FTICR mass spectrometry can be successfully used for precise, accurate, and selective quantitative analyses of HIV-1 protease inhibitors in cell lysates. In addition, the lower limits of quantification obtained allow clinical applications of the technique.