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Bio-Inspired DNA Nanoswitches and Nanomachines: Applications in Biosensing and Drug Delivery
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Arnaud Desrosiers, Alexis Vallée-Bélisle
In the event that a specific input target of interest has no known DNA binding sequence, SELEX methods can be employed to identify nucleotide sequences that display high affinity for small organics [92], proteins [93,94] and even viruses [95] or whole bacteria [96] (mostly through surface proteins/sugars). Briefly, SELEX (short for systematic evolution of ligands by exponential enrichment) is a method developed in 1990 [37,97] in which specific nucleotide sequences (referred to as aptamer with typically 15–40 nucleotides) from random libraries are selected to bind specific targets with high affinity through several rounds of selection. This method was first developed for RNA selection but was then rapidly adapted to select DNA sequences [36]. In this method, one selection round typically consists in a simple binding experiment where DNA sequences bound to the target of interest are amplified and used for the next selection round.
An Overview of Ruthenium Complexes as a Potential Sensing Agent
Published in Ajay Kumar Mishra, Lallan Mishra, Ruthenium Chemistry, 2018
Goutam Kumar Patra, Anupam Ghorai
Seenivasan and co-workers recently reported a new, simple, label free sensor [Ru(dmbpy)(dcbpy)dppz)] complex (dmbpy; 4,40-dimethyl-2,20-bipyridine,dcbpy;4,40-dicorboxy-2,20-bipyridine, dppz; dipyridophenazine) (Fig. 3.24) intercalated aptamer based recognition of amyloid-β (Seenivasan et al., 2015). For the first time, they elucidate the application of the RNA aptamer–Ru(II) complex system for specific recognition of amyloid monomer and inhibit the oligomer/fibril formation. Aptamers are DNA or RNA molecules that can specifically bind to a wide range of targets from small molecules to whole cells that can be selected through an in vitro selection method known as systematic evolution of ligands by exponential enrichment (SELEX). Interestingly, afore mentioned Ru(II) complex shows weak luminescence intensity in the aqueous medium but it shows strong luminescence intensity in the presence of RNA aptamer.
Recent Advances with Targeted Liposomes for Drug Delivery
Published in Vladimir Torchilin, Handbook of Materials for Nanomedicine, 2020
Josimar O. Eloy, Raquel Petrilli, Fabíola Silva Garcia Praça, Marlus Chorilli
Systematic evolution of ligands by exponential enrichment (SELEX) is a well-established and efficient technology, able to produce oligonucleotides (DNA and RNA molecules), called aptamers, with high target affinity. Aptamers, also known as “chemical antibodies,” have many advantages, including stability, having high affinity and selectivity, besides presenting low immunogenicity (Darmostuk et al., 2014). Thus, aptamers are considered promising alternatives to antibodies and can be used for cancer detection and targeted drug delivery (Zhou et al., 2018).
Aptamer-based technology for radionuclide targeted imaging and therapy: a promising weapon against cancer
Published in Expert Review of Medical Devices, 2020
Luca Filippi, Oreste Bagni, Clara Nervi
Aptamers are constituted by single-strand artificial oligonucleotides sequences of DNA, RNA, or modified RNA. Their peculiar property is folding and forming three-dimensional structures, capable of interacting and specifically binding to target molecules, with an affinity in the nanomolar/sub-nanomolar range, similar to that of monoclonal antibodies (MoAb). It has to be highlighted that, respect to MoAbs, aptamers present several advantages: easier production and lower cost, lower immunogenicity, possibility of chemical synthesis and modification and, most interestingly, the property of refolding after denaturation, thus going back to the desired tridimensional (3D) configuration [2]. A wide range of aptamers can be generated through the evolutionary engineering method called systematic evolution of ligands by exponential enrichment (SELEX). However, aside SELEX, other approaches have been recently incorporated into the selection protocol to improve the efficiency of high-affinity aptamer-production [2,3].
Theranostic approaches in nuclear medicine: current status and future prospects
Published in Expert Review of Medical Devices, 2020
Luca Filippi, Agostino Chiaravalloti, Orazio Schillaci, Roberto Cianni, Oreste Bagni
Lastly, theranostic developments will trigger research for new biomarkers and probes. In this regard, the already mentioned EGFR represents a very interesting target for innovative theranostic approaches. In such a field, the new technology of aptamers has been introduced. Aptamers are single-stranded DNA/RNA oligonucleotides that can be obtained from the systematic evolution of ligands by exponential enrichment (SELEX) technology [96]. Aptamers are reported to be highly specific for the target and characterized by low immunogenicity. As specifically regards EGFR, it has recently developed a 18 F-labeled RNA aptamer which showed highly selective targeting ability in mouse tumor models expressing different levels of EGFR. Although this approach needs to be validated by further studies, it is reasonable to hypothesize that it will represent an expanding field of research for theranostics in the future [97].
Advances of engineered extracellular vesicles-based therapeutics strategy
Published in Science and Technology of Advanced Materials, 2022
Hiroaki Komuro, Shakhlo Aminova, Katherine Lauro, Masako Harada
Aptamers are single-stranded RNA or DNA molecules that bind specifically to target molecules by adopting a complex 3D structure. Target molecules of aptamers include a wide range of proteins, peptides, carbohydrates, lipids, and low molecular weight compounds. Due to their high binding affinity and specificity as well as antibodies, they have been used in various fields, such as therapeutics and diagnostics [268]. Aptamers are generated using a PCR-based in vitro selection strategy known as the systematic evolution of ligands by exponential enrichment (SELEX) method [269,270]. Aptamers have a shorter half-life in blood compared to antibodies, while antibodies are difficult to remove from the body, making it challenging to deal with any abnormalities that may occur after administration. The development of drugs to neutralize aptamers is also easier than for antibodies. Antibodies administered therapeutically are foreign to the body and often become antigens, resulting in the generation of anti-drug antibodies in the patient, which can limit treatment. Aptamers, however, are synthetic molecules that generally do not produce anti-drug antibodies and are considered to be safe. For example, Wan et al. used AS1411, a nucleolin targeting aptamer anchored to dendritic derived EVs and loaded with paclitaxel, a chemotherapeutic drug, to achieve targeted drug delivery in vivo and in vitro [135]. Similarly, Luo et al. conjugated a bone marrow stromal cell (BMSC) targeting aptamer to BMSC-derived EVs that allowed for the accumulation of the EVs in the bone of the mouse model, resulting in a targeted treatment option for osteoporosis and bone fractures as illustrated in vitro and in vivo [271]. Thus, aptamers have the potential to overcome some of the difficulties associated with using antibodies in targeted EV cargo delivery.