5 research outputs found
DNA-directed assembly of inorganic nanoparticles
No full textIn the last two decades, inorganic nanoparticles have become an active field of research due to their unique physical properties. The advancements in the control over size, shape and composition opened up many potential applications in a wide range of fields from optoelectronics to medicine. A lot of research focusses on the controlled assembly of nanoparticles into larger pre-defined structures. A very successful approach uses DNA-functionalised nanoparticles as building blocks, which are capable of self-assembly driven by the DNA design. Such nanoparticle assemblies can infer new optical properties like circular dichroism or make multi-functional materials for advanced applications.In this work, a novel tool for the ligation of nanoparticle assemblies with DNA is presented. The UV-responsive molecule 3-cyanovinyl carbazole was embedded in DNA strands as a crosslinker for the covalent linkage of dsDNA. The covalent bond significantly increases the stability of dsDNA even in unfavourable conditions allowing a wider range of applicability. Unlike with other crosslinking techniques, already formed interstrand bonds can be reversed with UV-B light as an external stimulus. The efficient application of 3-cyanovinyl carbazole in tetrahedral gold nanoparticle assemblies is demonstrated for the first time. In addition, limitations of the strain-promoted azide-alkyne click reaction in the same system are revealed.DNA-directed hetero-assemblies consisting of CdSe/ZnS quantum dots and upconversion nanoparticles are presented. The results suggest that energy transfer from excited upconversion nanoparticles to quantum dots occurs upon self-assembly with short oligonucleotides. This example shows the potential of using DNA-based assembly as a general technique for creating novel materials helping to gain a fundamental understanding about nanoparticle interactions.In addition, lead halide perovskite nanoparticles are introduced. A modified synthesis protocol is demonstrated, which significantly increases the processability of such nanoparticles
Gold nanoparticles and fluorescently-labelled DNA as a platform for biological sensing
No full textIn the past decade gold nanoparticle-nucleic acid conjugates became progressively important for biomedical applications. Fluorophores attached to nucleic acid-gold nanoparticle conjugates have opened up a new era of biological sensing. The most promising advancement in this field was the invention of the so-called ‘nano-flare’ systems. These systems are capable of detecting specific endocellular targets such as mRNAs, microRNAs or small molecules in real time. In this minireview, we discuss the current progress in the field of DNA-nanoparticles as sensors, their properties, stability, cellular uptake and cytotoxicity
Reversible ligation of programmed DNA-gold nanoparticle assemblies
No full textWe demonstrate a new method to reversibly cross-link DNA-nanoparticle dimers, trimers, and tetramers using light as an external stimulus. A DNA interstrand photo-cross-linking reaction is possible via ligation of a cyano-vinyl carbazole nucleoside with an opposite thymine when irradiated at 365 nm. This reaction results in nanoparticle assemblies that are not susceptible to DNA dehybridization conditions. The chemical bond between the two complementary DNA strands can be reversibly broken upon light irradiation at 312 nm. This is the first example of reversible ligation in DNA-nanoparticle assemblies using light and enables new developments in the field of programmed nanoparticle organization
Cells on hierarchically-structured platforms hosting functionalized nanoparticles
No full textIn this work, we report on a novel approach to develop hierarchically-structured cell culture platforms incorporating functionalized gold nanoparticles (AuNPs). In particular, the hierarchical substrates comprise primary pseudo-periodic arrays of silicon microcones combined with a secondary nanoscale pattern of homogenously deposited AuNPs terminated with bio-functional moieties. AuNPs with various functionalities (i.e. oligopeptides, small molecules and oligomers) were successfully attached onto the microstructures. Experiments with PC12 cells on the hierarchical substrates incorporating AuNPs carrying the RGD peptide showed an impressive growth and NGF-induced differentiation of the PC12 cells, compared to that on the NPs-free, bare, micropatterned substrates. The exploitation of the developed methodology for the binding of AuNPs as carriers of specific bio-functional moieties onto micropatterned culture substrates for cell biology studies is envisaged
Encapsulated enzymes with integrated fluorescence-control of enzymatic activity
No full textA fluorescence-based particle sensor for oxaloacetic acid is presented. In the presence of nicotinamide adenine dinucleotide as a cofactor, oxaloacetic acid is converted by malate dehydrogenase into l-malic acid. The progress of the reaction is monitored by sensing of proton consumption with an integrated pH sensor. The kinetics of this sensor are investigated on a single particle level. This work demonstrates the feasibility to detect analytes upon their enzymatic conversion into a product, which in turn can be sensed with a fluorophore responding to changes in the concentration of this product. Integration of enzymes and fluorophores into one carrier particle, as demonstrated here for the case of polyelectrolyte polymer capsules, allows the range of analytes that can be detected with fluorescence to be extended, as it enhances selectivity. This coupled system allows enzymatic activity, as well as the kinetics of malate dehydrogenase, to be monitored.</p
