Site-Specific Control of Distances between Gold Nanoparticles Using Phosphorothioate Anchors on DNA and a Short Bifunctional Molecular Fastener

MoS2-Based Sensor Array for Accurate Identification of Cancer Cells with Ensemble-Modified Aptamers

In this work, we present an array-based chemical nose sensor that utilizes a set of ensemble-modified aptamer (EMAmer) probes to sense subtle physicochemical changes on the cell surface for cancer cell identification. The EMAmer probes are engineered by domain-selective incorporation of different types and/or copies of positively charged functional groups into DNA scaffolds, and their differential interactions with cancer cells can be transduced through competitive adsorption of fluorophore-labeled EMAmer probes loaded on MoS2 nanosheets. We demonstrate that this MoS2-EMAmer-based sensor array enables rapid and effective discrimination among six types of cancer cells and their mixtures with a concentration of 104 cells within 60 min, achieving a 94.4% accuracy in identifying blinded unknown cell samples. The established MoS2-EMAmer sensing platform is anticipated to show significant promise in the advancement of cancer diagnostics.

Ensemble Modified Aptamer Based Pattern Recognition for Adaptive Target Identification

The difficulty of the molecular design and chemical synthesis of artificial sensing receptors restricts their diagnostic and proteomic applications. Herein, we report a concept of "ensemble modified aptamers" (EMAmers) that exploits the collective recognition abilities of a small set of protein-like side-chain-modified nucleic acid ligands for discriminative identification of molecular or cellular targets. Different types and numbers of hydrophobic functional groups were incorporated at designated positions on nucleic acid scaffolds to mimic amino acid side chains. We successfully assayed 18 EMAmer probes with differential binding affinities to seven proteins. We constructed an EMAmer-based chemical nose sensor and demonstrated its application in blinded unknown protein identification, giving a 92.9% accuracy. Additionally, the sensor is generalizable to the detection of blinded unknown bacterial and cellular samples, which enabled identification accuracies of 96.3% and 94.8%, respectively. This sensing platform offers a discriminative means for adaptive target identification and holds great potential for diverse applications.

Chemically modified nucleic acids and DNA intercalators as tools for nanoparticle assembly

The self-assembly of inorganic nanoparticles to larger structures is of great research interest as it allows the fabrication of novel materials with collective properties correlated to the nanoparticles' individual characteristics. Recently developed methods for controlling nanoparticle organisation have enabled the fabrication of a range of new materials. Amongst these, the assembly of nanoparticles using DNA has attracted significant attention due to the highly selective recognition between complementary DNA strands, DNA nanostructure versatility, and ease of DNA chemical modification. In this review we discuss the application of various chemical DNA modifications and molecular intercalators as tools for the manipulation of DNA-nanoparticle structures. In detail, we discuss how DNA modifications and small molecule intercalators have been employed in the chemical and photochemical DNA ligation in nanostructures; DNA rotaxanes and catenanes associated with reconfigurable nanoparticle assemblies; and DNA backbone modifications including locked nucleic acids, peptide nucleic acids and borane nucleic acids, which affect the stability of nanostructures in complex environments. We conclude by highlighting the importance of maximising the synergy between the communities of DNA chemistry and nanoparticle self-assembly with the aim to enrich the library of tools available for the manipulation of nanostructures.

Preparation, Functionalization, Modification, and Applications of Nanostructured Gold: A Critical Review

Gold nanoparticles (Au NPs) play a significant role in science and technology because of their unique size, shape, properties and broad range of potential applications. This review focuses on the various approaches employed for the synthesis, modification and functionalization of nanostructured Au. The potential catalytic applications and their enhancement upon modification of Au nanostructures have also been discussed in detail. The present analysis also offers brief summaries of the major Au nanomaterials synthetic procedures, such as hydrothermal, solvothermal, sol-gel, direct oxidation, chemical vapor deposition, sonochemical deposition, electrochemical deposition, microwave and laser pyrolysis. Among the various strategies used for improving the catalytic performance of nanostructured Au, the modification and functionalization of nanostructured Au produced better results. Therefore, various synthesis, modification and functionalization methods employed for better catalytic outcomes of nanostructured Au have been summarized in this review.

Cell-specific aptamers and their conjugation with nanomaterials for targeted drug delivery

INTRODUCTION

Aptamers are short, single-stranded DNA or RNA sequences that can fold into complex secondary and tertiary structures and bind to various target molecules with high affinity and specificity. These properties, as well as rapid tissue penetration and ease of chemical modification, make aptamers ideal recognition elements for in vivo targeted drug delivery and attractive molecules for use in disease diagnosis and therapy.

AREAS COVERED

The general properties of aptamers as well as advantages over their counterpart antibodies are briefly discussed. Next, aptamer selection by cell- systematic evolution of ligands by exponential enrichment is described in detail. Finally, the review summarizes recent progress in the field of targeted drug delivery based on aptamers and their conjugation to liposomes, micelles and other nanomaterials.

EXPERT OPINION

Advances in nanotechnology have led to new and improved nanomaterials for biomedical applications. Conjugation of nanoparticles (NPs) with aptamers exploits both technologies, making aptamer-NP conjugates ideal agents for drug delivery with proven therapeutic effects and the reduction of toxicity to normal tissue. The use of multivalent aptamer-conjugated nanomaterials represents one of the new directions for drug development in the future; as such, continuing studies of these multivalent aptamers and bioconjugates should result in important clinical applications in targeted drug delivery.

Tuning two-photon photoluminescence of gold nanoparticle aggregates with DNA and its application as turn-on photoluminescence probe for DNA sequence detection

Plasmon coupling between noble metal nanoparticles has been known to dramatically enhance linear and nonlinear optical properties of nearby chromophores and metal nanoparticles themselves. The interparticle distance is expected to have significant influence on the coupling strength. Here we have prepared DNA tuned Au nanoparticle assemblies with well controlled separation distances from 2.0 to 12.2 nm to investigate plasmon coupling strength and particle size effects on two-photon photoluminescence (TPPL) enhancement. TPPL intensities of these DNA coupled nanoassemblies were found to increase rapidly as the separation distance decreases. The largest TPPL enhancement factors of 115 and 265 were achieved at the shortest available separation distance of 2.0 nm for 21 and 41 nm Au NPs-dsDNA assemblies, respectively. We have further utilized DNA induced coupling of Au NPs and TPPL enhancement to develop a two-photon sensing scheme for detection of DNA sequences. This TPPL based method displayed high sensitivity with a limit of detection of 2.9 pM and excellent selectivity against ssDNA with mismatched bases. A single mismatch can be easily differentiated at room temperature. Taking the unique advantages of two-photon excitation, this method could be potentially further extended to DNA detection inside cells or even in vivo. These findings can provide important insight for fundamental understanding of plasmon-coupling enhanced TPPL and development of various two-photon excitation based applications.

Discovery of the DNA "genetic code" for abiological gold nanoparticle morphologies

DNA is in control: Different combinations of DNA nucleotides can control the shape and surface roughness of gold nanoparticles during their synthesis. These nanoparticles were synthesized in the presence of either homogenous oligonucleotides or mixed-base oligonucleotides using gold nanoprisms as seeds. The effect of the individual DNA bases and their combinations on shape control are shown in the figure.