Although multivalent cation batteries based on magnesium, calcium or aluminium are technologically attractive, the metal anode still represents a challenge. It is now demonstrated that significant quantities of calcium can be plated and stripped at room temperature with low polarization. There is considerable interest in multivalent cation batteries, such as those based on magnesium, calcium or aluminium1,2,3,4,5,6,7,8,9,10,11. Most attention has focused on magnesium. In all cases the metal anode represents a significant challenge. Recent work has shown that calcium can be plated and stripped, but only at elevated temperatures, 75 to 100 °C, with small capacities, typically 0.165 mAh cm−2, and accompanied by significant side reactions7. Here we demonstrate that calcium can be plated and stripped at room temperature with capacities of 1 mAh cm−2 at a rate of 1 mA cm−2, with low polarization (∼100 mV) and in excess of 50 cycles. The dominant product is calcium, accompanied by a small amount of CaH2 that forms by reaction between the deposited calcium and the electrolyte, Ca(BH4)2 in tetrahydrofuran (THF). This occurs in preference to the reactions which take place in most electrolyte solutions forming CaCO3, Ca(OH)2 and calcium alkoxides, and normally terminate the electrochemistry. The CaH2 protects the calcium metal at open circuit. Although this work does not solve all the problems of calcium as an anode in calcium-ion batteries, it does demonstrate that significant quantities of calcium can be plated and stripped at room temperature with low polarization.

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Plating and stripping calcium in an organic electrolyte

There is intense interest in quantifying the levels of microRNA because of its importance as a blood-borne biomarker. The challenge has been to develop methods that can monitor microRNA expression both over broad concentration ranges and in ultralow amounts directly in a patient’s blood. Here, we show that, through electric-field-induced reconfiguration of a network of gold-coated magnetic nanoparticles modified by probe DNA (DNA–Au@MNPs), it is possible to create a highly sensitive sensor for direct analysis of nucleic acids in samples as complex as whole blood. The sensor is the first to be able to detect concentrations of microRNA from 10 aM to 1 nM in unprocessed blood samples. It can distinguish small variations in microRNA concentrations in blood samples of mice with growing tumours. The ultrasensitive and direct detection of microRNA using an electrically reconfigurable DNA–Au@MNPs network makes the reported device a promising tool for cancer diagnostics. An ultrasensitive miRNA sensor based on gold-coated magnetic nanoparticles modified with redox-labelled probe DNA is capable of detecting miRNA at a concentration of 10 aM to 1 nM in unprocessed blood, and following tumour-induced variation in miRNA levels.

Nucleic acid hybridization on an electrically reconfigurable network of gold-coated magnetic nanoparticles enables microRNA detection in blood

Rising progesterone (P4) levels in humans due to its overconsumption through hormonal therapy, food products, or drinking water can lead to many negative health effects. Thus, the simple and accurate assessment of P4 in both environmental and clinical samples is highly important to protect public health. In this work, we present the selection, identification, and characterization of ssDNA aptamers with high binding affinity to P4. The aptamers were selected in vitro from a single-stranded DNA library of 1.8 × 1015 oligonucleotides showing dissociation constants (KD) in the low nanomolar range. The dissociation constant of the best aptamer, designated as P4G13, was estimated to be 17 nM by electrochemical impedance spectroscopy (EIS) as well as fluorometric assay. Moreover, the aptamer P4G13 did not show cross-reactivity to analogues similar to progesterone such as 17β-estradiol (E2) and norethisterone (NET). An impedimetric aptasensor for progesterone was then fabricated based on the conformational change...

Aptamer-Based Label-Free Impedimetric Biosensor for Detection of Progesterone

Straight long-range surface plasmon waveguides are demonstrated as biosensors for the detection of cells, proteins and changes in the bulk refractive index of solutions. The sensors consist of 5 μm wide 22 nm thick Au stripes embedded in polymer (CYTOPTM) with microfluidic channels etched into the top cladding. Bulk sensing is demonstrated by sequentially injecting six solutions of different refractive indices in 2 × 10−3 RIU increments; such index steps were detected with a signal-to-noise ratio of ~1000. Selective capture of cells is demonstrated using Au waveguides functionalized with antibodies against blood group A, and red blood cells of group A and O in buffer as positive and negative analyte. Bovine serum albumin in buffer was used to demonstrate protein sensing. A monolayer of bovine serum albumin physisorbed on a carboxyl-terminated self-assembled monolayer on Au was detected with a signal-to-noise ratio of ~300. Overall, the biosensor demonstrated a good capability for detecting bulk changes in solution and for sensing analyte over a very wide range of mass (from cells to proteins). The biosensors are compact, inexpensive to fabricate, and may find use over a wide range of cost-sensitive sensing and detection applications.

Biosensing using straight long-range surface plasmon waveguides

Development of an efficient sensing platform capable of continual monitoring of biomarkers is needed to assess the functionality of the in vitro organoids and to evaluate their biological responses toward pharmaceutical compounds or chemical species over extended periods of time. Here, a novel label-free microfluidic electrochemical (EC) biosensor with a unique built-in on-chip regeneration capability for continual measurement of cell-secreted soluble biomarkers from an organoid culture in a fully automated manner without attenuating the sensor sensitivity is reported. The microfluidic EC biosensors are integrated with a human liver-on-a-chip platform for continual monitoring of the metabolic activity of the organoids by measuring the levels of secreted biomarkers for up to 7 d, where the metabolic activity of the organoids is altered by a systemically applied drug. The variations in the biomarker levels are successfully measured by the microfluidic regenerative EC biosensors and agree well with cellular viability and enzyme-linked immunosorbent assay analyses, validating the accuracy of the unique sensing platform. It is believed that this versatile and robust microfluidic EC biosensor that is capable of automated and continual detection of soluble biomarkers will find widespread use for long-term monitoring of human organoids during drug toxicity studies or efficacy assessments of in vitro platforms.

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Label-Free and Regenerative Electrochemical Microfluidic Biosensors for Continual Monitoring of Cell Secretomes.

https://www.researchgate.net/file.PostFileLoader.html?id=55c2f19860614bf8408b45d5&assetKey=AS%3A273670520410114%401442259544828

Noriyuki Masuda

Papers

Gold cleaning methods for electrochemical detection applications