off-line preconcentration (extraction, purification) using
aptamers on solid phase support (e.g., SPE column, magnetic beads
and nanoparticles (NPs)) [5–7] and microfluidic formats [8]. The
use of aptamer conjugated with magnetic modified adsorbents,
called magnetic solid-phase extraction (MSPE), has been a topic of
greatinterestto researchers [9]. By using nanosized adsorbents,the
extraction capacity and efficiency increases, because of the significantly
higher surface area-to-volume ratio. Moreover, Fe3O4 NPs
properties are feasible for sample extraction without any sample
centrifugation or filtration step. Another advantage of MNPs is the
capability of surface modification with various functional groups
leading to selective sample extraction [9,10]. In this work, we used
aldehyde modified Fe3O4 NPs conjugated with aptamer as MSPE
for the extraction of adenosine in human urine.