Cell-targeting Aptamers Research Articles

Cell-targeting aptamers act as intracellular delivery vehicles.

Aptamers are single-stranded nucleic acids or peptides identified from a randomized combinatorial library through specific interaction with the target of interest. Targets can be of any size, from small molecules to whole cells, attesting to the versatility of aptamers for binding a wide range of targets. Aptamers show drug properties that are analogous to antibodies, with high specificity and affinity to their target molecules. Aptamers can penetrate disease-causing microbial and mammalian cells. Generated aptamers that target surface biomarkers act as cell-targeting agents and intracellular delivery vehicles. Within this context, the "cell-internalizing aptamers" are widely investigated via the process of cell uptake with selective binding during in vivo systematic evolution of ligands by exponential enrichment (SELEX) or by cell-internalization SELEX, which targets cell surface antigens to be receptors. These internalizing aptamers are highly preferable for the localization and functional analyses of multiple targets. In this overview, we discuss the ways by which internalizing aptamers are generated and their successful applications. Furthermore, theranostic approaches featuring cell-internalized aptamers are discussed with the purpose of analyzing and diagnosing disease-causing pathogens.

Cell-Capture and Release Platform Based on Peptide-Aptamer-Modified Nanowires.

Nanowires have attracted much attention due to their potential bioapplications, such as delivery of drugs or sensing devices. Here we report the development of a unique cell-capture and release platform based on nanowires. The combination of nanowires, surface-binding peptides, and cell-targeting aptamers leads to specific and efficient capture of cancer cells. Moreover, the binding processes are reversible, which is not only useful for downstream analysis but also for reusability of the substrate. Our work provides a new method in the design of the cell-capture and release platform, which may open up new opportunities of developing cell-separation and diagnosis systems based on cell-capture techniques.

Generating Cell Targeting Aptamers for Nanotheranostics Using Cell-SELEX.

Detecting and understanding changes in cell conditions on the molecular level is of great importance for the accurate diagnosis and timely therapy of diseases. Cell-based SELEX (Systematic Evolution of Ligands by EXponential enrichment), a foundational technology used to generate highly-specific, cell-targeting aptamers, has been increasingly employed in studies of molecular medicine, including biomarker discovery and early diagnosis/targeting therapy of cancer. In this review, we begin with a mechanical description of the cell-SELEX process, covering aptamer selection, identification and identification, and aptamer characterization; following this introduction is a comprehensive discussion of the potential for aptamers as targeting moieties in the construction of various nanotheranostics. Challenges and prospects for cell-SELEX and aptamer-based nanotheranostic are also discussed.

Cell membrane capsules as biomimetic drug carriers

Event Abstract Back to Event Cell membrane capsules as biomimetic drug carriers Lijie Han1, Yuanhong Zhang1 and Zhengwei Mao1 1 Zhejiang University, Department of Polymer Science and Engieering, China Introduction: Systemic administration of chemotherapeutic agents results in indiscriminate drug distribution and severe toxicity. Until now, encapsulation and targeting of drugs have typically relied on synthetic vehicles, which cannot minimize clearance by the renal system and may also increase the risk of chemical side effects. Cell membrane capsules (CMCs) provide a generic and far more natural approach to the challenges of drug encapsulation and delivery in vivo[1],[2]. Results and Discussion: Here aptamer AS1411, which can recognize and bind over-expressed nucleolin on cancer cell membrane, was chemically conjugated onto CMCs. As a result, AS1411 modified CMCs showed enhanced ingestion in certain cancer cells in vitro and accumulation in mouse cancer xenografts in vivo. Chemotherapeutics and contrast agents with therapeutically significant concentrations can be packaged into CMCs by reversible permeating their plasma membranes. The systematic administration of cancer targeting CMCs loaded with doxorubicin hydrochloride can significantly inhibit tumor growth in mouse xenografts, with significantly reduced toxicity compare to free drug. These findings suggest that cancer targeting CMCs may have considerable benefits in drug delivery and cancer treatment. Conclusion: In this study, biocompatible cell membrane capsules were prepared from human endothelial cells with preserved membrane structure and functions. Cancer cell targeting aptamer AS1411 was conjugated onto the CMCs, resulted in enhanced ingestion of CMCs in certain cancer cells and accumulation of CMCs in mouse tumor xenografts. Chemotherapeutics and contrast agents can be packaged into the CMCs by reversible permeating their plasma membranes. The systematic administration of cancer targeting CMCs loaded with doxorubicin can inhibit tumor growth in mouse xenografts, with significantly reduced toxicity compare to free drug. These findings suggest that targeting CMCs may have considerable benefits in drug delivery and cancer treatment. Natural Science Foundation of China (51120135001); Key Science Technology Innovation Team of Zhejiang Province (2013TD02)

Multiple functional nanoprobe for contrast-enhanced bimodal cellular imaging and targeted therapy.

Many one-photon fluorescence-based theranostic nanosystems have been developed for simultaneous therapeutic intervention/monitoring for various types of cancers. However, for early diagnosis of cancer, two-photon fluorescence microscopy (TPFM) can realize deep-tissue imaging with higher spatial resolution. In this study, we first report a multiple functional nanoprobe for contrast-enhanced bimodal cellular imaging and targeted therapy. Components of the nanoprobe include (1) two-photon dye-doped mesoporous silica nanoparticles (TPD-MSNs); (2) MnO2 nanosheets that act as a (i) gatekeeper for TPD-MSNs, (ii) quencher for TP fluorescence, and (iii) contrast agent for MRI; (3) cancer cell-targeting aptamers. Guided by aptamers, TPD-MSNs are rapidly internalized into the target cells. Next, intracellular glutathione reduces MnO2 to Mn(2+) ions, resulting in contrast-enhanced TP fluorescence and magnetic resonance signal for cellular imaging. Meanwhile, preloaded doxorubicin and Chlorin e6 are released for chemotherapy and photodynamic therapy, respectively, with a synergistic effect and significantly enhanced therapeutic efficacy.

Synthetic aptamer-polymer hybrid constructs for programmed drug delivery into specific target cells.

Viruses have evolved specialized mechanisms to efficiently transport nucleic acids and other biomolecules into specific host cells. They achieve this by performing a coordinated series of complex functions, resulting in delivery that is far more efficient than existing synthetic delivery mechanisms. Inspired by these natural systems, we describe a process for synthesizing chemically defined molecular constructs that likewise achieve targeted delivery through a series of coordinated functions. We employ an efficient “click chemistry” technique to synthesize aptamer-polymer hybrids (APHs), coupling cell-targeting aptamers to block copolymers that secure a therapeutic payload in an inactive state. Upon recognizing the targeted cell-surface marker, the APH enters the host cell via endocytosis, at which point the payload is triggered to be released into the cytoplasm. After visualizing this process with coumarin dye, we demonstrate targeted killing of tumor cells with doxorubicin. Importantly, this process can be generalized to yield APHs that specifically target different surface markers.

A dual functional fluorescent probe for glioma imaging mediated by Blood-brain barrier penetration and glioma cell targeting

Glioma is a huge threat for human being because it was hard to be completely removed owing to both the infiltrating growth of glioma cells and integrity of blood brain barrier. Thus effectively imaging the glioma cells may pave a way for surgical removing of glioma. In this study, a fluorescent probe, Cy3, was anchored onto the terminal of AS1411, a glioma cell targeting aptamer, and then TGN, a BBB targeting peptide, was conjugated with Cy3-AS1411 through a PEG linker. The production, named AsT, was characterized by gel electrophoresis, 1H NMR and FTIR. In vitro cellular uptake and glioma spheroid uptake demonstrated the AsT could not only be uptaken by both glioma and endothelial cells, but also penetrate through endothelial cell monolayer and uptake by glioma spheroids. In vivo, AsT could effectively target to glioma with high intensity. In conclusion, AsT could be used as an effective glioma imaging probe.

Targeted and ultrasound-triggered drug delivery using liposomes co-modified with cancer cell-targeting aptamers and a thermosensitive polymer

In this study, we demonstrated the feasibility of targeted and ultrasound-triggered drug delivery using liposomes co-modified with single stranded DNA aptamers that recognized platelet-derived growth factor receptors (PDGFRs) as targeting ligands for breast cancer cells and poly(NIPMAM-co-NIPAM) as the thermosensitive polymer (TSP) to sensitize these liposomes to high temperature. TSP-modified liposomes (TSP liposomes) released encapsulated calcein under 1MHz ultrasound irradiation for 30s at 0.5W/cm2 as well as the case under incubation for 5min at 42°C. Ultrasound-triggered calcein release from TSP liposomes was due to an increased local temperature, resulting from cavitation bubble collapse induced by ultrasound, and not due to an increase in the bulk medium temperature. Liposomes modified with PDGFR aptamers (APT liposomes) bound to MDA-MB-231 human breast cancer cells through PDGFR aptamers; however, they did not bind to primary human mammary epithelial cells (HMECs). The binding of APT liposomes was greatest for MDA-MB-231 cells, followed by MCF-7, WiDr, and HepG2 cancer cells. In a cell injury assay using doxorubicin (DOX)-loaded APT/TSP liposomes and ultrasound irradiation, cell viability of MDA-MB-231 at 24h after ultrasound irradiation (1MHz for 30s at 0.5W/cm2) with DOX-loaded APT/TSP liposomes was 60%, which was lower than that with ultrasound irradiation and DOX-loaded TSP liposomes or with DOX-loaded APT/TSP liposomes alone.

Targeted Cell–Cell Interactions by DNA Nanoscaffold‐Templated Multivalent Bispecific Aptamers

Cell-cell interactions are essential for multicellular organisms, playing important roles in their development, function, and immunity. Herein a bottom-up strategy to construct self-assembled DNA nanostructures is reported, consisting of multivalent, bispecific, cell-targeting aptamers to specifically induce cell-cell interactions. Various DNA nanoscaffolds are rationally designed to assemble aptamers with different valencies and flexibilities, and their cellular binding capabilities are tested. Multivalent aptamers, assembled on more rigid scaffolds, display higher binding activities. Further, multivalent bispecific aptamer fusion molecules are constructed based on this configuration, and successfully link two types of cells. Using cell-targeting aptamers, the presented strategy eliminates the need to chemically modify cell surfaces and offers excellent cell specificity, binding efficiency, and stability. This proof-of-concept study establishes that multivalent bispecific aptamers linked on DNA-nanoscaffolds can mediate cellular engagement, which could lead to their use in directing or guiding cell-cell interactions in many biological events.