Magnetic nanoparticles (MNPs) conjugated with aptamer was developed for the selective extraction of
adenosine in urine samples followed by electrospray ionization–ion mobility spectrometry (ESI–IMS).
The ion mobility spectrum of adenosine showed two peaks at low concentrations and two more peaks
related to dimer of adenosine at high concentrations. However, the ion mobility spectrum of eluent
at low concentration showed only the peaks related to dimer of adenosine. In other words, aptamer
captured two adenosine molecules between the top G-quartet and the two short stems, where they
bonded to each other.