Using live cells to generate aptamers for cancer study.

Aptamers are ssDNA, RNA, or modified nucleic acids, usually consisting of short strands of oligonucleotides. Aptamers have the ability to bind specifically to a range of targets, from small organic molecules to proteins. However, by using cell-based aptamer selection, we have developed a strategy to identify the molecular signatures on the surface of targeted cells by exploiting the differences at the molecular level between any two given cell types.

Engineering a subcellular targetable, red-emitting, and ratiometric fluorescent probe for Ca2+ and its bioimaging applications.

A new, visible-light-excited and red-emitting fluorescent Ca(2+) probe, STDBT, was synthesized, which consists of 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid as a Ca(2+)-chelating moiety and two benzothiazolium hemicyanine dyes as fluorophores. The spectral profiles of its free and Ca(2+)-bound forms were studied. Upon addition of Ca(2+), the fluorescence spectra of STDBT displayed a significant enhancement (about 48-fold) in fluorescence intensity and a 20-nm blueshift (from 600 to 580 nm) in the emission spectrum.

A highly selective ratiometric fluorescent probe for 1,4-dithiothreitol (DTT) detection.

A highly selective ratiometric fluorescent probe, which contains an aminonaphthalimide fluorophore and a self-immolative spacer for 1,4-dithiothreitol (DTT) detection was designed and synthesized. The probe displays a 66 nm red-shift of fluorescence emission and the color changes from colorless to jade-green upon reaction with DTT. These properties are mechanistically ascribed to the strong reducing capability of DTT.

Nanoparticle-aptamer conjugates for cancer cell targeting and detection.

Aptamers are DNA or RNA oligonucleotide sequences that selectively bind to their target with high affinity and specificity. They are obtained using an iterative selection protocol called SELEX. Several small molecules and proteins have been used as targets.

A novel methotrexate delivery system based on chitosan-methotrexate covalently conjugated nanoparticles.

In this paper, a chitosan-methotrexate covalently conjugated nanoparticles (CS-MTX-TPP NPs) has been developed as a potential delivery system for methotrexate (MTX). MTX was first conjugated to CS by using glutaraldehyde as cross-linked agent, and followed by the process of ionic gelation between MTX-conjugated CS and sodium tripolyphosphate (TPP) to form CS-MTX-TPP NPs at mild reaction conditions. The hydrodynamic diameter of CS-MTX-TPP NPs and the encapsulation efficiency of MTX were affected by the weight ratio of MTX/CS.

DNA-based micelles: synthesis, micellar properties and size-dependent cell permeability.

Functional nanomaterials based on molecular self-assembly hold great promise for applications in biomedicine and biotechnology. However, their efficacy could be a problem and can be improved by precisely controlling the size, structure, and functions. This would require a molecular engineering design capable of producing monodispersed functional materials characterized by beneficial changes in size, shape, and chemical structure.

DNA aptamer-micelle as an efficient detection/delivery vehicle toward cancer cells.

We report the design of a self-assembled aptamer-micelle nanostructure that achieves selective and strong binding of otherwise low-affinity aptamers at physiological conditions. Specific recognition ability is directly built into the nanostructures. The attachment of a lipid tail onto the end of nucleic acid aptamers provides these unique nanostructures with an internalization pathway.

A liposome-based nanostructure for aptamer directed delivery.

A therapeutic aptamer conjugated liposome drug delivery system which delivered loaded drug to target cells with high specificity and excellent efficiency was prepared and characterized.

Nanoparticle-mediated IgE-receptor aggregation and signaling in RBL mast cells.

Complex cell behaviors are usually triggered by multivalent ligands that first bind to membrane receptors and then promote receptor clustering, thus altering intracellular signal transduction. While it is possible to produce such altered signal transduction by synthetic means, the development of chemically defined multivalent ligands of effectors is sometimes difficult and tedious. Specifically, the average spacing between two binding sites within an antibody and the average distance between receptors on the cell membrane are usually larger than most organic molecules.

Biosynthesis of size-controlled gold nanoparticles using fungus, Penicillium sp.

The unique optoelectronic and physicochemical properties of gold nanoparticles are significantly dependent on the particle size, shape and structure. In this paper, biosynthesis of size-controlled gold nanoparticles using fungus Penicillium sp. is reported.

Aptamer-nanoparticle strip biosensor for sensitive detection of cancer cells.

We report an aptamer-nanoparticle strip biosensor (ANSB) for the rapid, specific, sensitive, and low-cost detection of circulating cancer cells. Known for their high specificity and affinity, aptamers were first selected from live cells by the cell-SELEX (systematic evolution of ligands by exponential enrichment) process. When next combined with the unique optical properties of gold nanoparticles (Au-NPs), ANSBs were prepared on a lateral flow device.

Single-walled carbon nanotube as an effective quencher.

Over the past few years, single-walled carbon nanotubes (SWNTs) have been the focus of intense research motivated by their unique physical and chemical properties. This review specifically summarizes recent progress in the development of fluorescence biosensors that integrate the quenching property of SWNTs and the recognition property of functional nucleic acids. SWNTs are substantially different from organic quenchers, showing superior quenching efficiency for a variety of fluorophores, with low background and high signal-to-noise ratio, as well as other advantages derived from the nanomaterial itself.

An allosteric dual-DNAzyme unimolecular probe for colorimetric detection of copper(II).

An effective dual-DNAzyme-based unimolecular probe design employing intramolecular signal transduction is demonstrated. The probe is composed of three domains: a DNA-cleaving DNAzyme, a substrate, and an HRP-mimicking DNAzyme. When the probe meets its target, cleavage of the substrate by the DNA-cleaving DNAzyme activates the HRP-mimicking DNAzyme, producing a colorimetric signal.

Aptamers generated from cell-SELEX for molecular medicine: a chemical biology approach.

Molecular medicine is an emerging field focused on understanding the molecular basis of diseases and translating this information into strategies for diagnosis and therapy. This approach could lead to personalized medical treatments. Currently, our ability to understand human diseases at the molecular level is limited by the lack of molecular tools to identify and characterize the distinct molecular features of the disease state, especially for diseases such as cancer.

Aptamer-based microfluidic device for enrichment, sorting, and detection of multiple cancer cells.

The ability to diagnose cancer based on the detection of rare cancer cells in blood or other bodily fluids is a significant challenge. To address this challenge, we have developed a microfluidic device that can simultaneously sort, enrich, and then detect multiple types of cancer cells from a complex sample. The device, which is made from poly(dimethylsiloxane) (PDMS), implements cell-affinity chromatography based on the selective cell-capture of immobilized DNA-aptamers and yields a 135-fold enrichment of rare cells in a single run.

Recognition of subtype non-small cell lung cancer by DNA aptamers selected from living cells.

In this work, we have developed new aptamer probes for non-small cell lung cancer (NSCLC) by directing the aptamer selection process against the living cells of adenocarcinoma, the most common subtype of NSCLC. A panel of single-stranded DNA (ssDNA) aptamers were generated and evaluated for adenocarcinoma cell recognition. The aptamers bound to the adenocarcinoma cells with dissociation constants in the nanomolar range and the binding of the selected aptamers to the adenocarcinoma cells were significantly stronger than the other cancerous lung cells as well as other types of cancer cells.

Nucleic acid aptamers for biosensors and bio-analytical applications.

Oligonucleotides were once considered only functional as molecules for the storage of genetic information. However, the discovery of RNAzymes, and later, DNAzymes, unravelled the innate potential of oligonucleotides in many other biological applications. In the last two decades, these applications have been further expanded through the introduction of Systematic Evolution of Ligands by EXponential enrichment (SELEX) which has generated, by repeated rounds of in vitro selection, a type of molecular probe termed aptamers.

Nucleic acid conjugated nanomaterials for enhanced molecular recognition.

Nucleic acids, whether designed or selected in vitro, play important roles in biosensing, medical diagnostics, and therapy. Specifically, the conjugation of functional nucleic acid based probe molecules and nanomaterials has resulted in an unprecedented improvement in the field of molecular recognition. With their unique physical and chemical properties, nanomaterials facilitate the sensing process and amplify the signal of recognition events.

Using aptamer-conjugated fluorescence resonance energy transfer nanoparticles for multiplexed cancer cell monitoring.

To facilitate the selection of effective therapeutic pathways and improve clinical outcomes, sensitive and simultaneous diagnosis of multiple trace biomarkers or cancer cells from complex living samples is particularly critical in the early stages of tumor development. To achieve this, we have combined the selectivity and affinity of aptamers with the spectroscopic advantages of fluorescence resonance energy transfer (FRET) nanoparticles (NPs). This has produced an aptamer-conjugated FRET NP assay that performs simultaneous multiplexed monitoring of cancer cells with the desired degree of sensitivity and selectivity.

Single-DNA molecule nanomotor regulated by photons.

We report the design of a single-molecule nanomotor driven by photons. The nanomotor is a DNA hairpin-structured molecule incorporated with azobenzene moieties to facilitate reversible photocontrollable switching. Upon repeated UV-vis irradiation, this nanomotor displayed 40-50% open-close conversion efficiency.

Barbated Skullcup herb extract-mediated biosynthesis of gold nanoparticles and its primary application in electrochemistry.

The design, synthesis, characterization and application of biologically synthesized nanomaterials have become an important branch of nanotechnology. In this paper, we report the extracellular synthesis of gold nanoparticles using Barbated Skullcup (BS) herb (a dried whole plant of Scutellaria barbata D. Don) as the reducing agent.