Aptamer technology for tracking cells’ status & function

Abstract

In fields such as cancer biology and regenerative medicine, obtaining information regarding cell bio-distribution,
tropism, status, and other cellular functions are highly desired. Understanding cancer behaviors including metastasis
is important for developing effective cancer treatments, while assessing the fate of therapeutic cells following
implantation is critical to validate the efficacy and efficiency of the therapy. For visualization purposes with medical
imaging modalities (e.g. magnetic resonance imaging), cells can be labeled with contrast agents (e.g. iron-oxide
nanoparticles), which allows their identification from the surrounding environment. Despite the success of revealing cell
biodistribution in vivo, most of the existing agents do not provide information about the status and functions of cells
following transplantation. The emergence of aptamers, single-stranded RNA or DNA oligonucleotides of 15 to 60 bases
in length, is a promising solution to address this need. When aptamers bind specifically to their cognate molecules, they
undergo conformational changes which can be transduced into a change of imaging contrast (e.g. optical, magnetic
resonance). Thus by monitoring this signal change, researchers can obtain information about the expression of the
target molecules (e.g. mRNA, surface markers, cell metabolites), which offer clues regarding cell status/function in
a non-invasive manner. In this review, we summarize recent efforts to utilize aptamers as biosensors for monitoring
the status and function of transplanted cells. We focus on cancer cell tracking for cancer study, stem cell tracking
for regenerative medicine, and immune cell (e.g. dendritic cells) tracking for immune therapy.