Molecular Engineering of Aptamer Self-Assemblies Increases in Vivo Stability and Targeted Recognition

Abstract

Functionally modified aptamer conjugates are promising tools for targeted imaging or treatment of various diseases. However, broad applications of aptamer molecules are limited by their in vivo instability. To overcome this challenge, current strategies mostly rely on covalent chemical modification of aptamers, a complicated process that requires case-by-case sequence design, multiple-step synthesis, and purification. Herein, we report a covalent modification-free strategy to enhance the in vivo stability of aptamers. This strategy simply utilizes one-step molecular engineering of aptamers with gold nanoclusters (GNCs) to form GNCs@aptamer self-assemblies. Using Sgc8 as a representative aptamer, the resulting GNCs@Sgc8 assemblies enhance cancer-cell-specific binding and sequential internalization by a receptor-mediated endocytosis pathway. Importantly, the GNCs@aptamer self-assemblies resist nuclease degradation for as long as 48 h, compared to the degradation of aptamer alone at 3 h. In parallel, the tumor-targeted recognition and retention of GNCs@aptamer self-assemblies are dramatically enhanced, indicated by a 9-fold signal increase inside the tumor compared to the aptamer alone. This strategy is to avoid complicated chemical modification of aptamers and can be extended to all aptamers. Our work provides a simple, effective, and universal strategy for enhancing the in vivo stability of any aptamer or its conjugates, thus expanding their imaging and therapeutic applications.

Aptamers used for molecular imaging and theranostics - recent developments

“…Another strategy to overcome the poor plasma stability of aptamers was reported by Xia et al . who synthesized sgc8-targeted gold NP nanoclusters through simple electrostatic interaction 96 . To synthesize the nanoclusters, sgc8 was mixed with gold NPs in 14:1 ratio, which led to a particle size of 94 nm.…”

Fabrication of avidin-stabilized gold nanoclusters with dual emissions and their application in biosensing

“…When the size of a nanostructure is comparable to the Fermi wavelength of the conduction electrons, the electron energy level becomes discontinuous owing to the quantum size effect, which may give rise to size-dependent luminescence, resulting in properties that are much different from those of classical metallic nanoparticles [ 7 ]. Compared to traditional organic fluorophores and quantum dots, Au NCs are not easily photobleached and have low toxicity, so they have great potential for application in biosensing [ 8 , 9 ]. In the synthesis and development of Au NCs, ligands that encapsulate the gold core have gradually evolved from small molecules of sulfhydryl compounds [ 10 ] to large-molecule polymers [ 11 ], dendrimers [ 12 ], DNA [ 13 ], peptides [ 14 ], and proteins [ 15 ].…”

DNA Framework-Programmed Ligand Positioning to Modulate the Targeting Performance

“…To date, various approaches such as ligand–receptor interaction have been used to improve the targeting competence of nanomedicine for precise treatment, − including the optimization and enhancement of targeting ligands via functional modification , and multiple target recognition, but efforts focused on the optimization of ligand-modification patterns have not been totally surveyed. Since most nanomedicines such as liposomes, microsphere, or micelles were generally composed of uneven macromolecular structures with poor quality control, which made it hard to precisely manipulate their formation process to obtain an identical molecular weight (MW), uniform size, and programmable morphology .…”

“…To date, various approaches such as ligand−receptor interaction have been used to improve the targeting competence of nanomedicine for precise treatment, 12−19 including the optimization and enhancement of targeting ligands via functional modification 20,21 and multiple target recognition, 22 but efforts focused on the optimization of ligand-modification patterns have not been totally surveyed.…”