Electrochemical detection of miRNAs

The recent progress made in the development of electrochemical methods for microRNA (miRNA) detection is presented. This progress is conceived to be largely due to the invention of novel assay methodologies and the use of various bioreagents and nanostructures. These enable a rigorous control over the sensing interface, provide enormous signal amplifications and single-base mismatch specificity. Femtomolar or even subfemtomolar detection limits were shown to be feasible by electrochemical assays. Thus electrochemical detection methodologies are of perspective for diagnostic miRNA detection

Reliable microspotting methodology for peptide-nucleic acid layers with high hybridization efficiency on gold SPR imaging chips

One-step direct immobilization of peptide-nucleic acid (PNA) probes onto gold surfaces through Au–S chemistry is critical in terms of generating self-assembled monolayers with high hybridization efficiency. We found that this problem is more severe if the immobilization is performed by contact microspotting to generate PNA arrays. Therefore, here we propose a novel microspotting-based immobilization method to generate PNA arrays with high hybridization efficiency on bare gold surface plasmon resonance imaging (SPRi) chips. The essence of the approach is to spot thiol labelled PNA strands prehybridized with a short complementary DNA strand instead of conventionally used single stranded PNA (ssPNA) probes. After immobilization the complementary DNA strands could be easily removed to activate the surface confined PNA probes. The incubation time and the type of spotting needle also have a marked influence on the hybridization efficiency of the PNA layers. However, we show that if all other conditions remain the same, PNA layers from prehybridized PNA probes exhibit superior hybridization efficiency than those from ssPNA probes

Nanoparticle displacement assay with electrochemical nanopore-based sensors

The proof of concept of a nanoparticle displacement assay that enables the use of large diameter nanopores for the detection of targets of smaller molecular dimensions is presented. We hypothesized that an inherent signal amplification should arise from the selective displacement of nanoparticles preloaded in a nanopore by a much smaller molecular target. The method is demonstrated using peptide nucleic acid (PNA)-functionalized gold nanopore arrays in which short DNA-modified gold nanoparticles are anchored by weak interaction. Complementary microRNAs are detected via the resistance change caused by competitive displacement of nanoparticles from the PNA-functionalized nanopores

A rational approach for generating cardiac troponin I selective Spiegelmers

We report the first protein selective Spiegelmers of diagnostic relevance by rational identification of a target epitope and reverse screening of Spiegelmer candidates following the selection procedure. Application of the presented approach resulted in isolation of cardiac troponin I selective Spiegelmers with low nanomolar dissociation constant and functionality in serum

The upgrade of the ALICE TPC with GEMs and continuous readout

The upgrade of the ALICE TPC will allow the experiment to cope with the high interaction rates foreseen for the forthcoming Run 3 and Run 4 at the CERN LHC. In this article, we describe the design of new readout chambers and front-end electronics, which are driven by the goals of the experiment. Gas Electron Multiplier (GEM) detectors arranged in stacks containing four GEMs each, and continuous readout electronics based on the SAMPA chip, an ALICE development, are replacing the previous elements. The construction of these new elements, together with their associated quality control procedures, is explained in detail. Finally, the readout chamber and front-end electronics cards replacement, together with the commissioning of the detector prior to installation in the experimental cavern, are presented. After a nine-year period of R&D, construction, and assembly, the upgrade of the TPC was completed in 2020.publishedVersio

Multivalent foldamer-based affinity assay for selective recognition of Aβ oligomers

Abstract Mimicking the molecular recognition functionality of antibodies is a great challenge. Foldamers are attractive candidates because of their relatively small size and designable interaction surface. This paper describes a sandwich type enzyme-linked immunoassay with a tetravalent β-peptide foldamer helix array as capture element and enzyme labeled tracer antibodies. The assay was found to be selective to β-amyloid oligomeric species with surface features transiently present in ongoing aggregation. In optimized conditions, with special emphasis on the foldamer immobilization, a detection limit of 5 pM was achieved with a linear range of 10–500 pM. These results suggest that protein mimetic foldamers can be useful tools in biosensors and affinity assays