Fluorescence Sensing Using DNA Aptamers in Cancer Research and Clinical Diagnostics

Abstract

Among the various advantages of aptamers over antibodies, remarkable is their ability to tolerate a large number of chemical modifications within their backbone or at the termini without losing significant activity. Indeed, aptamers can be easily equipped with a wide variety of reporter groups or coupled to different carriers, nanoparticles, or other biomolecules, thus producing valuable molecular recognition tools effective for diagnostic and therapeutic purposes. This review reports an updated overview on fluorescent DNA aptamers, designed to recognize significant cancer biomarkers both in soluble or membrane-bound form. In many examples, the aptamer secondary structure switches induced by target recognition are suitably translated in a detectable fluorescent signal using either fluorescently-labelled or label-free aptamers. The fluorescence emission changes, producing an enhancement (“signal-on”) or a quenching (“signal-off”) effect, directly reflect the extent of the binding, thereby allowing for quantitative determination of the target in bioanalytical assays. Furthermore, several aptamers conjugated to fluorescent probes proved to be effective for applications in tumour diagnosis and intraoperative surgery, producing tumour-type specific, non-invasive in vivo imaging tools for cancer pre- and post-treatment assessment.

Novel RNA aptamers targeting gastrointestinal cancer biomarkers CEA, CA50 and CA72-4 with superior affinity and specificity

“…Furthermore, the potential applications of fluorescently-labelled aptamers are being widely studied and proven to be applicable on cancer therapy and diagnosis, such as intraoperative surgery and cancer-type specific in vivo non-invasive imaging [ 39 ]. In particular, a number of aptamers have been studied for their implications in specific recognition of cancer-related targets (e.g.…”

“…In particular, a number of aptamers have been studied for their implications in specific recognition of cancer-related targets (e.g. thrombin, platelet-derived growth factor (PDGF), angiogenin, mucin, vascular endothelial growth factor (VEGF) and etc) [ 39 ]. In addition, the internalization process by which aptamers are uptake into cells depends on the function of their targets and typically divided into clathrin-mediated endocytosis or micropinocytosis [ 40 ].…”

Aptamer-Conjugated Tb(III)-Doped Silica Nanoparticles for Luminescent Detection of Leukemia Cells

“…DMF, Ethanol, and TEOS were purified by distillation. The synthesis of p-sulfonatothiacalix [4]arene tetrasodium salt (TCAS) was carried out according to the procedure described in [23].…”

“…They are short single-stranded DNA or RNA sequences selected through a process called systematic evolution of ligands by exponential enrichment (SELEX) [2]. Aptamers show strong and specific binding to cancer targets [3,4], low immunogenicity, low batch-to-batch variability, and are inexpensive [5]. They can be conjugated with drugs for targeted drug delivery [6,7], with fluorescent nanoparticles for cell imaging [8], and with magnetic nanoparticles for magnetic hyperthermia [9].…”

“…Calix[n]arenes coordinate lanthanide ions through covalently attached functional groups acting as antennae, enhancing both the luminescence and magnetic relaxation properties of lanthanides [21]. Indeed, terbium (III) complexes with thiacalix [4]arenesulfonate (TCAS) have the most intensive luminescence among other lanthanide-sulfocalixarene complexes [22]. TCAS coordinates Tb(III) through sulfonate groups of the upper rim in acidic/weakly acidic media and by phenolate groups of the lower rim in neutral/weakly basic media [23].…”