Aptamer-nanoparticle complexes as powerful diagnostic and therapeutic tools

Abstract

Correct diagnosis and successful therapy are extremely important to enjoy a healthy life when suffering from a disease. To achieve these aims, various cutting-edge technologies have been designed and fabricated to diagnose and treat specific diseases. Among these technologies, aptamer-nanomaterial hybrids have received considerable attention from scientists and doctors because they have numerous advantages over other methods, such as good biocompatibility, low immunogenicity and controllable selectivity. In particular, aptamers, oligonucleic acids or peptides that bind to a specific target molecule, are regarded as outstanding biomolecules. In this review, several screening techniques for aptamers, also called systematic evolution of ligands by exponential enrichment (SELEX) methods, are introduced, and diagnostic and therapeutic aptamer applications are also presented. Furthermore, we describe diverse aptamer-nanomaterial conjugate designs and their applications for diagnosis and therapy.

Figure 1

Applications of biomolecule–nanomaterial complexes.

Figure 2

The SELEX procedure. (a) A schematic illustration for general SELEX. It consists of four steps: incubation of target molecules with libraries, elution of bound libraries, amplification of the libraries and separation of the libraries for the next round. (b) A schematic illustration of cell-based SELEX. Negative selection is required for each round.

Figure 3

Various applications of aptamers for detection. (a) Electrochemical impedance spectroscopic detection for MUC1. This image was adapted from Chen et al. (b) Colorimetric detection. This image was adapted from Jeon et al. (c) Fluorescent detection. This image was adapted from Roncancio et al. Apt, aptamer; ATMND, 2-amino-5,6,7-trimethyl-1,8-naphthyridine; PDDA, poly(diallyldimethylammonium chloride); pLDH, Plasmodium lactate dehydrogenase; PoPD, poly(o-phenylenediamine); TEOS, tetraethyl orthosilicate; Thi, thionine.

Figure 4

Examples of antagonistic aptamers. (a) The ARC1779 aptamer. ARC1779 is conjugated to a 20-kDa PEG at the 5′-terminus (underline indicates 2′-O-methoxy nucleotides). (b) The NOX-A12 aptamer. iT, inverted deoxythymidine; ps, phosphorothioate linkage.

Figure 5

Diagnostic applications of biomolecule–nanomaterial complexes. (a) Three types of FRET-based detection using QDs: detection using quencher-modified oligonucleotides, detection using fluorophore-modified oligonucleotides and detection using intercalating dyes. This image was adapted from Zhou. (b) Detection platform for breast cancer using dual-aptamer-modified SiNPs. HER2(+) or MUC1(+) breast cancer cells are selectively separated using dual-aptamer-modified magnetic beads, and SiNP conjugates are incubated with the magnetic beads-cell complexes. Breast cancer cells are quantified based on fluorescence from dyes inside the SiNPs. This image was adapted from Jo et al. Ex, excitation.

Figure 6

Therapeutic applications of biomolecule–nanomaterial complexes. (a) PTT using dual-aptamer-modified AuNSs. Aptamer-AuNS agents selectively induce apoptosis by generating considerable heat (A10 aptamer for PSMA (+) cancer cells and DUP1 aptamer for PSMA (–) cells). This image was adapted from Jo et al. (b) Aptamer-modified drug-encapsulated liposome. This image was adapted from Kang et al. PEG, polyethylene glycol; TMR, tetramethylrhodamine.