Rationally Designed Multivalent Aptamers Targeting Cell Surface for Biomedical Applications

Abstract

Specific interactions between ligands and receptors on cell surface play an important role in the cell biological process. Nucleic acid aptamers as commonly used ligands enable specific recognition and tight binding to membrane protein receptors for modulation of cell fate. Therefore, molecular probes with aptamers can be applied for cancer diagnosis and targeted therapy by targeting overexpression membrane proteins of cancer cells. However, because of their fast degradation and rapid glomerulus clearance in vivo, the applications of aptamers in physiological conditions remain challenged. Inspired by natural multivalent interactions, many approaches have been developed to construct multivalent aptamers to improve the performance of aptamers in complex matrices with higher binding affinity, more stability, and longer circulation time. In this review, we first introduce the aptamer generation from purified protein-based SELEX and whole cell-based SELEX for targeting the cell surface. We then highlight the approaches to fabricate multivalent aptamers and discuss their properties. By integrating different materials (including inorganic nanomaterials, diacyllipid, polymeric nanoparticles, and DNA nanostructures) as scaffolds with an interface modification technique, we have summarized four kinds of multivalent aptamers. After that, representative applications in biosensing and targeted therapy are illustrated to show the elevated performance of multivalent aptamers. In addition, we analyze the challenges and opportunities for the clinical practices of multivalent aptamers.

High‐Affinity Dimeric Aptamers Enable the Rapid Electrochemical Detection of Wild‐Type and B.1.1.7 SARS‐CoV‐2 in Unprocessed Saliva

“…The results indicate that the dimeric aptamer approach can produce aptamers with significantly enhanced affinity for the trimeric spike protein, presumably via bivalent recognition. [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ] Figure 1 B shows binding curves derived from dot‐blot assays using the full trimeric spike proteins of SARS‐CoV‐2 (representative dot blot assay results are provided in Figure S2). In comparison to the substantial affinity enhancement observed for the heterodimeric aptamer DSA1N5 (≈99‐fold; Table S2), the two homodimeric aptamers showed much reduced affinity enhancements relative to their monomeric counterparts (Table S2).…”

“…To derive a high‐affinity DNA aptamer, we took advantage of a well‐established strategy of engineering bivalent or multivalent aptamers through ligation of two or more monomers,[ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ] given the fact that the full spike protein is a homotrimeric protein and each SARS‐CoV‐2 virus expresses ≈30 spikes on its surface. [ 48 , 49 ] We hypothesized that generation of dimeric aptamers from the best members in the collection of the diverse monomeric S1 protein‐binding aptamers developed recently by our groups [38] may provide an aptamer with sufficient affinity to achieve this goal.…”

High sensitivity detection of tumor cells in biological samples using a multivalent aptamer strand displacement strategy

“…33 This can be explained by the special structure-switching properties of the proposed probe mediated strand displacement reactions when encountering the targets, and the synergistic effect of multiple ligands, thus rapidly producing a diagnostic signal on the cell surface and avoiding false signals in cell nuclei due to endocytosis. 34,35…”

High‐Affinity Dimeric Aptamers Enable the Rapid Electrochemical Detection of Wild‐Type and B.1.1.7 SARS‐CoV‐2 in Unprocessed Saliva

“…Ther esults indicate that the dimeric aptamer approach can produce aptamers with significantly enhanced affinity for the trimeric spike protein, presumably via bivalent recognition. [40][41][42][43][44][45][46][47] Figure 1B shows binding curves derived from dot-blot assays using the full trimeric spike proteins of SARS-CoV-2 (representative dot blot assay results are provided in Figure S2). In comparison to the substantial affinity enhancement observed for the heterodimeric aptamer DSA1N5 ( % 99-fold;T able S2), the two homodimeric aptamers showed much reduced affinity enhancements relative to their monomeric counterparts (Table S2).…”

“…To derive ah igh-affinity DNAa ptamer,w et ook advantage of aw ell-established strategy of engineering bivalent or multivalent aptamers through ligation of two or more monomers, [40][41][42][43][44][45][46][47] given the fact that the full spike protein is ahomotrimeric protein and each SARS-CoV-2 virus expresses % 30 spikes on its surface. [48,49] We hypothesized that generation of dimeric aptamers from the best members in the collection of the diverse monomeric S1 protein-binding aptamers developed recently by our groups [38] may provide an aptamer with sufficient affinity to achieve this goal.…”