Circulating biomarkers are on the verge of becoming powerful diagnostic tools for various human diseases. However, the complex sample composition makes it difficult to detect biomarkers directly from blood at the bench or at the point-of-care. Blood cells are often a source of variability of the biomarker signal. While the interference of hemoglobin is a long known source of variability, the release of nucleic acids and other cellular components from hemocytes is a new concern for measurement and detection of circulating extracellular markers. Research into miniaturised blood plasma separation has been thriving in the last 10 years (2006-2016). Most point-of-care systems need microscale blood plasma separation, but developed solutions differ in complexity and sample volume range. But could blood plasma separation be avoided completely? This focused review weights the advantages and limits of miniaturised blood plasma separation and highlights the most interesting advances in direct capture as well as smart blood plasma separation.

The growing threat posed by antimicrobial resistance on the healthcare and economic well‐being of mankind is pushing the need to develop novel and improved diagnostic platforms for its rapid detection at point of care, facilitating better patient management strategies during antibiotic therapy. In this paper, we present the manufacturing and characterisation of a low‐cost carbon screen‐printed electrochemical sensor on a ceramic substrate. Using label‐free electrochemical impedance spectroscopy, the sensor is demonstrated for the detection of blaNDM, which is one of the main antimicrobial resistance factors in carbapenem‐resistant Enterobacteriaceae. The electrochemical performance of the newly fabricated sensor was initially investigated in relation to the function of its underlying composite materials, evaluating the choice of carbon and dielectric pastes by characterising properties like surface roughness, wetting and susceptibility of unspecific DNA binding. Subsequently, the sensor was used in an electrochemical impedance spectroscopy assay for the sensitive and specific detection of synthetic blaNDM targets achieving a detection limit of 200 nM. The sensor properties and performance demonstrated in this study proved the suitability of the new electrode materials and manufacturing for further point‐of‐care test development as an inexpensive and effective alternative to gold electrodes sensor.

Antibiotic resistance is now one of the biggest threats humankind is facing, as highlighted in a declaration by the General Assembly of the United Nations in 2016. In particular, the growing resistance rates of Gram-negative bacteria cause increasing concerns. The occurrence of the easily transferable, plasmid-encoded mcr-1 colistin resistance gene further worsened the situation, significantly enhancing the risk of the occurrence of pan-resistant bacteria. There is therefore a strong demand for new rapid molecular diagnostic tests for the detection of mcr-1 gene-associated colistin resistance. Electrochemical impedance spectroscopy (EIS) is a well-suited method for rapid antimicrobial resistance detection as it enables rapid, label-free target detection in a cost-efficient manner. Here, we describe the development of an EIS-based mcr-1 gene detection test, including the design of mcr-1-specific peptide nucleic acid probes and assay specificity optimization through temperature-controlled real-time kinetic EIS measurements. A new flow cell measurement setup enabled for the first time detailed real-time, kinetic temperature-controlled hybridization and dehybridization studies of EIS-based nucleic acid biosensors. The temperature-controlled EIS setup allowed single-nucleotide polymorphism discrimination. Target hybridization at 60 °C enhanced the perfect match/mismatch (PM/MM) discrimination ratio from 2.1 at room temperature to 3.4. A hybridization and washing temperature of 55 °C further increased the PM/MM discrimination ratio to 5.7 by diminishing the mismatch signal during the washing step while keeping the perfect match signal. This newly developed mcr-1 gene detection test enabled the direct, specific label, and amplification-free detection of mcr-1 gene harboring plasmids from Escherichia coli.