Cancer Cell Targeting Using Multiple Aptamers Conjugated on Nanorods

Abstract

Molecular recognition toward specific cells is a key issue for effective disease, such as cancer, diagnosis and therapy. Although many molecular probes such as aptamers and antibodies can recognize the unique molecular signatures of cancer cells, some of these probes only have relatively weak binding affinities. This results in poor signaling and hinders cell targeting. Here, we use Au-Ag nanorods (NRs) as a nanoplatform for multivalent binding by multiple aptamers on the rod to increase both the signal and binding strengths of these aptamers in cancer cell recognition. Up to 80 fluorophore-labeled aptamers can be attached on a 12 nm x 56 nm NR, resulting in a much stronger fluorescence signal than that of an individual dye-labeled aptamer probe. The molecular assembly of aptamers on the NR surfaces also significantly improves the binding affinity with cancer cells through simultaneous multivalent interactions with the cell membrane receptors. This leads to an affinity at least 26-fold higher than the intrinsic affinity of the original aptamer probes. As determined by flow cytometric measurements, an enhancement in fluorescence signal in excess of 300-fold is obtained for the NR-aptamer-labeled cells compared with those labeled by individual aptamer probes. Therefore, the molecular assembly of aptamers clearly shows potential applications for the elucidation of cells with low density of binding sites, or with relatively weak binding probes, and can thus greatly improve our ability to perform cellular imaging and targeting. This is an excellent example of using nanomaterials to develop advanced molecular binders with greatly improved properties for cellular studies.

Targeted Nanoparticles for Cancer Therapy

“…A large number of aptamers have been raised against cancer-associated antigens such us AS1411 aptamer for targeting nucleolin protein, which is highly expressed in the membrane of cancer cells [48][49], aptamers CPG 7909 and IMO 2055, that target Toll-like receptor 9 (TLR9), which is expressed by certain immune cells, TD05 aptamer, which was selected for the Burkitt's lymphoma Ramos cell line [47], Sgc8c aptamer which targets leukemia biomarker protein tyrosine kinase-7 (PTK7) [46,50] and can recognize target leukemia cells, DNA aptamers to leukemic lymphoid (CEM) cells [46], and fruoropyrimidine RNA aptamers which target Prostate-specific membrane antigen (PSMA) [51] for targeting prostate cancer. And also another aptamers against antigens such as pigpen [52] for targeting the tumor microvasculature, or mucin 1 (MUC1) [53] for targeting various epithelial neoplasms that upregulate MUC1, whose expression has been associated with carcinomas.…”

“…Thus, Au-Ag NRs have been conjugated with multiple anti-PTK7 aptamers, such as scg8 aptamer, for targeted cancer photothermal therapy [48,55]. By using Au-Ag NRs that can be conjugated around 80 aptamers, 26 times higher binding affinity was obtained compared to individual aptamer strands [48].…”

“…Thus, Au-Ag NRs have been conjugated with multiple anti-PTK7 aptamers, such as scg8 aptamer, for targeted cancer photothermal therapy [48,55]. By using Au-Ag NRs that can be conjugated around 80 aptamers, 26 times higher binding affinity was obtained compared to individual aptamer strands [48]. By functionalizing the surface of Au NPs with an RNA aptamer that binds to PSMA, NP-aptamer conjugates were used for targeted molecular computed tomography imaging and treatment of prostate cancer [56].Yin et al reported a one-step method for the synthesis of DNA-aptamer templated fluorescent silver nanoclusters (AgNCs) [57].…”

Aptamer-Nanoparticle Bioconjugates for Drug Delivery

“…For example, gold-silver nanorods were used as a platform for multiple aptamer immobilization. Up to 80 aptamers could be attached to rods for obtaining 26-fold higher affinity and 300-fold higher fluorescence (Huang et al, 2008). Fig.…”

Electrochemical and Electrochemiluminescence Determination of Cancer Cells Based on Aptamers and Magnetic Beads

“…As determined by flow cytometric measurements, an enhancement in fluorescence signal in excess of 300-fold is obtained for the NR-aptamer-labeled cells compared with those labeled by individual aptamer probes. [27,28] They also constructed a cellular model and applied this aptamer-receptor interaction to estimate receptor densities and distributions on the cell surface. [29] The cellular internalization of one of the selected aptamers, sgc8, which binds human protein tyrosine kinase-7 on cell surfaces was also studied.…”