Self‐Assembled Aptamer‐Based Drug Carriers for Bispecific Cytotoxicity to Cancer Cells

Abstract

Monovalent aptamers can deliver drugs to target cells by specific recognition. However, different cancer subtypes are distinguished by heterogeneous biomarkers, and one single aptamer was unable to recognize all clinical samples from different patients with even the same type of cancers. To address heterogeneity among cancer subtypes for targeted drug delivery, as a model, we developed a drug carrier with broader recognition range of cancer subtypes. This carrier (SD) was self-assembled from two modified monovalent aptamers. It showed bi-specific recognition abilities to target cells in cell mixtures, thus broadening the recognition capabilities of its parent aptamers. The self-assembly of SD simultaneously formed multiple drug loading sites for anticancer drug Doxorubicin (Dox). The Dox-loaded SD (SD-Dox) also showed bi-specific abilities of target cell binding and drug delivery. Most importantly, SD-Dox induced bi-specific cytotoxicity in target cells in cell mixtures. Therefore, by broadening the otherwise limited recognition capabilities of monovalent aptamers, bi-specific aptamer-based drug carriers would facilitate aptamer applications for clinically heterogeneous cancer subtypes which respond to the same cancer therapy.

Self-assembled, aptamer-tethered DNA nanotrains for targeted transport of molecular drugs in cancer theranostics

“…Several widely-used anthracycline anticancer drugs, including doxorubicin (Dox), daunorubicin (DNR), and epirubicin (EPR), were used as drug cargo models. Because it is well known that these drugs can preferentially intercalate into double-stranded 5′-GC-3′ or 5′-CG-3′, resulting in the quenching of drug fluorescence (fluorescence "OFF") (20,27,36), M1 and M2 were designed such that all their sequences would form drug intercalation sites (ACG/CGT) in nanotrains, with each pair of M1 and M2 contributing an average of 16 sites. Consequently, each individual nanotrain needs only one aptamer locomotive for targeting, whereas all of the remaining dsDNA "boxcars," as characterized above, are used to carry a high payload of drugs, thus reducing the amount of DNA otherwise required to transport a specific amount of drugs.…”

Nuclease-resistant synthetic drug-DNA adducts: programmable drug-DNA conjugation for targeted anticancer drug delivery

“…A bispecific aptameric nanocarrier, assembled by hybridization of the two toeholds extending from aptamers sgc8 and KK1B10, 15 was used as a model (Supplementary Figure S5A). The monomers sgc8-hyb and KK1B10-hyb were first used to prepare DDAs with Dox, and the resultant two DDAs were mixed to allow hybridization.…”

“…Passive targeting exploits the leaky blood vasculature and poor lymphatic drainage in tumors that allow nanocarriers, such as polymer nanoparticles, 3 liposomes, 7 gold nanoparticles 8 and nucleic acid nanostructures, [9][10][11][12][13][14][15][16][17] to access and accumulate in the tumor by the enhanced permeability and retention effect. 3 DNA, the genetic carrier in nature, has been exploited as both synthetic targeting elements (for example, aptamers, CpG DNA), [18][19][20][21] and nanocarriers [9][10][11][12][13][14][15][16][17] for both active and passive targeted drug delivery, owing to such features as ease of reproducible synthesis and modification, biodegradability, sequence programmability, structure predictability of the resultant DNA drug carriers and intrinsic targeting or therapeutic functionalities. DNA aptamers, screened by Systematic Evolution of Ligands by EXponential enrichment, 22,23 are excellent candidates as targeting elements.…”

“…These remarkable features have allowed DNA to be developed into targeted drug delivery systems, in which drugs are conjugated with DNA both noncovalently 15,[17][18][19] (for example, intercalation of anthracycline drugs into double-stranded DNA-CG sites 15,18,19 and photosensitizer TMPyp4 into G-quadruplexes) and covalently. 30,31 However, noncovalent conjugation typically requires specific DNA sequences or modification with additional sequences for drug conjugation; yet current solid-phase DNA synthesis technology can only synthesize DNA of limited lengths.…”

Aptamers-Guided DNA Nanomedicine for Cancer Theranostics

“…Chemotherapeutic drugs were loaded on these nanotrains, with several widely used anthracycline anticancer drugs, including Doxorubicin (Dox), Daunorubicin (DNR), and Epirubicin (EPR), as drug cargo models. Since it is well known that these drugs can preferentially intercalate into doublestranded 5′-GC-3′ or 5′-CG-3′, resulting in the quenching of drug fluorescence [104,106,110], M1 and M2 were designed such that all their sequences would form drug intercalation sites (ACG/CGT) in nanotrains. Sgc8-NTr-Dox complexes showed negligible drug diffusion from sgc8-NTrs, indicating the high stability of sgc8-NTr-Dox complexes.…”