Potential use of LIAD time-of-flight mass spectrometry for the detection of biomolecules: An example of detecting nucleobases in DNA

Deoxyribonucleic acid (DNA) carries the genetic information necessary for the synthesis of RNA and proteins; it is a biological macromolecule essential for the development and proper functioning of living organisms and is composed of nucleobases, deoxyribose, and phosphate. The four nucleobases in DNA are adenine (AD), guanine (GU), thymine (TY), and cytosine (CY). Abnormal concentrations of these four nucleobases in an organism have a significant impact on disease diagnosis. Therefore, the qualitative and quantitative detection of these DNA nucleobases in organisms is helpful to diagnose certain diseases. In this work, we report the simultaneous determination of purine (AD, GU) and pyrimidine (TY, CY) nucleobases in DNA using laser-induced acoustic desorption (LIAD) with electron ionization (EI)/time-of-flight mass spectrometry (TOFMS). The purine (MW 120 Da) samples were used as model compounds to assess the sensitivity and quantitative performance of the instrument. Its limits of detection assessed using the LIAD/EI/MS method were similar to 0.5-1.2 pg under optimal conditions, and their calibration curves exhibited good linearity (R-2 = 0.98). The LIAD/TOFMS was successfully applied in the simultaneous detection of AD, GU, TY, and CY in real DNA samples. The advantage of this technique is simple, fast, and without complex pre-treatment processes. In addition, a quartz-enhanced LIAD (QE-LIAD) source was used to improve the signal strength. The desorption for complex biomolecules shows that the QE-LIAD is still a "gentle" desorption source.