nA μM Research Articles

Electroenzymatic choline sensing at near the theoretical performance limit.

A high performance, electroenzymatic microsensor for choline based on choline oxidase (ChOx) immobilized on Pt coated with permselective polymer layers has been created that exhibits sensitivity approaching the theoretical performance limit. Sensor construction was guided by simulations performed with a detailed mathematical model. Implantable microsensors with an array of electroenzymatic sensing sites provide a means to record concentration changes of choline, an effective surrogate for acetylcholine due to its very rapid turnover in the brain, and other neurochemicals in vivo. However, electroenzymatic sensors generally have insufficient sensitivity and response time to monitor neurotransmitter signaling on the millisecond timescale with cellular-level spatial resolution. Model simulations suggested that choline sensor performance can be improved significantly by optimizing immobilized ChOx layer thickness and minimizing the thicknesses of permselective polymer coatings as well. Electroenzymatic choline sensors constructed with a ∼5 μm-thick crosslinked ChOx layer atop 200 nm-thick permselective films (poly(m-phenylenediamine) and Nafion) exhibited unprecedented sensitivity and response time of 660 ± 40 nA μM-1 cm-2 at 37 °C and 0.36 ± 0.05 s, respectively, while maintaining excellent selectivity. Such performance characteristics provide greater flexibility in the design of microelectrode array (MEA) probes with near cellular-scale sensing sites arranged in more dense arrays. Also, faster response times enable better resolution of transient acetylcholine signals and better correlation of these events with electrophysiological recordings so as to advance study of brain function.

A highly integrated sensing paper for wearable electrochemical sweat analysis

Wearable electrochemical sensors have attracted tremendous attention in recent years. Significant progress has been achieved, particularly in device integration. Most wearable devices are integrated on thin-film polymer, however, less attention is paid to the sweat flow at human-device interfaces, which is of great significance for continuous real-time analysis and long-term skin comfort. Here, we reported a low-cost, freestanding and disposable highly integrated sensing paper (HIS paper) for real-time analysis of sweat. By using a simple printing process, the HIS paper combining hydrophobic protecting wax, conducting electrodes, and the incorporated MXene/methylene blue (Ti3C2Tx/MB) active materials was assembled. In particular, the printed paper was folded into a multi-layer structure, in which a reasonable designed three-dimensional (3D) sweat diffusion path is established by connecting the hydrophilic regions of each layer, providing efficient pathways for the collection and diffusion of sweat along the vertical direction of the folded HIS paper. More importantly, the independent 3D position of three-electrode facilitates the decoration and fixation of enzymes, as well as the accessibility of electrolytes. In addition, a dual-channel electrochemical sensor that can simultaneously detect glucose and lactate with sensitivity of 2.4 nA μM−1 and 0.49 μA mM−1 respectively was produced based on the HIS paper. This HIS paper provides a miniaturized, low-cost and flexible solution for a range of biochemical platforms, including wearable bioelectronics.

Highly sensitive and selective acute myocardial infarction detection using aptamer‐tethered MoS 2 nanoflower and screen‐printed electrodes

Acute myocardial infarction (AMI) is one of the leading causes of death worldwide. Cardiac troponin I (cTn1) is a commonly used biomarker for the diagnosis of AMI. Although there are various detection methods for the rapid detection of cTn1 such as optical, electrochemical, and acoustic techniques, electrochemical aptasensing techniques are commonly used because of their ease of handling, portability, and compactness. In this study, an electrochemical cTn1 biosensor, MoS2 nanoflowers on screen-printed electrodes assisted by aptamer, was synthesized using hydrothermal technique. Field emission scanning electron microscopy revealed distinct 2D nanosheets and jagged flower-like 3D MoS2 nanoflower structure, with X-ray diffraction analysis revealing well-stacked MoS2 layers. Voltammetry aptasensing of cTn1 ranges from 10fM to 1nM, with a detection limit at 10fM and a sensitivity of 0.10nAµM-1 cm-2 . This is a ∼fivefold improvement in selectivity compared with the other proteins and human serum. This novel aptasensor retained 90% of its biosensing activity after 6 weeks with a 4.3% RSD and is a promising high-performance biosensor for detecting cTn1.

Highly redox-active organic molecular nanomaterials: Naphthalene and phenanthrene molecular species π-stacked MWCNT modified electrodes for oxygen-interference free H2O2 sensing in neutral pH

Electrochemical detection of Hydrogen peroxide in neutral pH is an important analytical problem that has been often worked out using horseradish peroxide (HRP) enzyme coupled with organic redox-active molecules as a transducer, and metallic systems in the form of metal nanoparticles and complexes chemically modified electrodes. Owing to non-amenable characteristic, direct electrochemical oxidation/reduction of H2O2 by redox-active organic molecules has been rarely described in the literature. Herein, we report naphthalene (NaP) and phenanthrene (PhenE) moieties immobilized MWCNT as advanced organic nanomaterial systems for enzyme-free, selective (dissolved oxygen, cysteine, citric acid, ascorbic acid, uric acid and glucose-interference free) and direct electrocatalytic reduction and sensing of H2O2 in neutral pH. These new organic-materials have been prepared by multiwall carbon nanotube (MWCNT) surface-bound electrochemical oxidation of NaP and PhenE at ~1.2 V vs Ag/AgCl in pH 2 KCl-HCl solution. The “as prepared” organic molecular materials showed a highly symmetrical voltammetric signal in cyclic voltammetric technique (peak-to-peak separation potential, ΔEp = 10 mV at scan rate = 10 mV s−1) and proton-coupled electron-transfer in characteristic. These new materials were characterized using several physicochemical techniques such as FTIR and Raman spectroscopes, transmission electron-microscope and electrochemical characterization (using radical quenching molecular system, 2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TEMPO)). From the collective experimental results, it has been revealed that cationic radical species like organic molecules are stabilized on the organic nanomaterial modified electrode surface (via strong π-π interaction) and showed the redox peak. Amperometric i-t responses of the modified electrodes showed a systematic variation in the H2O2 detection current signal with current linearity in a range of 25–300 μM. Calculated current sensitivities and regression coefficient values are 4.8 nA μM−1 and 0.9996 with NaP-Redox and 4.20 nA μM−1 and 0.9994 with PhenE-Redox systems, respectively.

Electrochemical Characterization and Bioelectrocatalytic H2O2 Sensing of Non‐Symbiotic Hexa‐Coordinated Sugar Beet Hemoglobins

AbstractThe biological role of non‐symbiotic plant hemoglobins (Hbs) is not well understood. It may involve sensing and signaling of reactive nitrogen and oxygen species–a property that can be used in electrochemical sensing. Here, we electrochemically studied two novel non‐symbiotic Beta vulgaris Hbs: BvHb1.2 and BvHb2 expressed in E. coli. At pH 7, we observed close potentials of their Fe2+/3+ hemes, −349 mV for BvHb1.2 and −345/−457 mV vs. Ag/AgCl for the “open” penta‐/“closed” hexa‐coordinated states of BvHb2. BvHbs bound and bioelectrocatalytically reduced O2 and H2O2 at potentials significantly exceeding their Fe2+/3+ heme potentials. BvHb2, with the onset of H2O2 reduction at 370 mV, enabled O2‐interference‐free 10 μM H2O2 detection at 0 mV, with a 87 nA μM−1 cm−2 sensitivity comparable to some peroxidases. The results underpin broad electrochemical applications of BvHbs in the electroanalysis of reactive species and in electrochemical biotransformations.

Fabrication and ex vivo evaluation of activated carbon–Pt microparticle based glutamate biosensor

As one of the most abundant neurotransmitters in the brain and the spinal cord, glutamate plays many important roles in the nervous system. Precise information about the level of glutamate in the extracellular space of living brain tissue may provide new insights on fundamental understanding of the role of glutamate in neurological disorders as well as neurophysiological phenomena. Electrochemical sensor has emerged as a promising solution that can satisfy the requirement for highly reliable and continuous monitoring method with good spatiotemporal resolution for characterization of extracellular glutamate concentration. Recently, we published a method to create a simple printable glutamate biosensor using platinum nanoparticles. In this work, we introduce an even simpler and lower cost conductive polymer composite using commercially available activated carbon with platinum microparticles to easily fabricate highly sensitive glutamate biosensor using direct ink writing method. The fabricated biosensors are functionality superior than previously reported with the sensitivity of 5.73 ± 0.078 nA μM−1 mm−2, detection limit of 0.03 μM, response time less than or equal to 1 s, and a linear range from 1 μM up to 925 μM. In this study, we utilize astrocyte cell culture to demonstrate our biosensor's ability to monitor glutamate uptake process. We also demonstrate direct measurement of glutamate release from optogenetic stimulation in mouse primary visual cortex (V1) brain slices.

Direct Growth of Bismuth Vanadate Thin Film Arrays on FTO via Galvanic Deposition Mediated by BiOI Nanosheets for Fabrication of Photoelectrochemical Non-Enzymatic Dopamine Sensing Platform

Development of a photoelectrochemical (PEC) sensor utilizing the energy of photon for the detection of bioanalytes is a challenging task. We hereby propose the easiest development of PEC sensor based on bismuth vanadate (BiVO4) photoanode on fluorine doped tin dioxide (FTO) electrode for sensing of bioanalytes. The fabrication of BiVO4/FTO electrode was performed by an extremely simple and energy efficient method called galvanic deposition. This was achieved in a two-step process viz. development of bismuth oxyiodide (BiOI) on FTO-glass electrode by galvanic deposition (BiOI/FTO) followed by moderate temperature annealing of BiOI/FTO in presence of Vanadyl (IV) acetyl acetonate to form the final electrode. The BiOI/FTO and BiVO4/FTO were thoroughly characterized by physicochemical and electrochemical means. The resultant structure revealed formation of a monoclinic scheelite BiVO4 (ms-BiVO4) structure which has the highest photocatalytic response compared to the other phases of BiVO4. One of the photoelectrochemical applications of ms-BiVO4 in the detection of bioanalyte was performed through the sensing of dopamine (DA). The BiVO4/FTO electrode exhibited high sensitivity (0.257 nA μM−1 cm−2), good linear range of concentration (102–106 μM) and a low limit of detection (0.154 μM) as a sensor for DA. The BiVO4/FTO electrode showed high reproducibility (RSD <4% under optimal condition), good stability, and high resistance against the polydopamine (PDA) fouling. The electrode was successfully demonstrated to perform the detection of DA including in real serum samples.

Electrocatalytic nanostructured ferric tannate as platform for enzyme conjugation: Electrochemical determination of phenolic compounds

A shell of nanostructured ferric tannates was spontaneously developed on the surface of naked maghemite nanoparticles (SAMNs, the core) by a simple wet reaction with tannic acid (TA). The as obtained core–shell nanomaterial (SAMN@TA) displays specific electrocatalytic and surface properties, which significantly differ from parent maghemite. Thanks to the known proclivity of TA to interact with proteins, SAMN@TA was proposed as a support for the direct immobilization of an enzyme. A ternary functional nanobioconjugate (SAMN@TA@TvL) was successfully self-assembled by incubating laccase from Trametes versicolor (TvL) and SAMN@TA. The SAMN@TA@TvL hybrid was kinetically characterized with respect to the native enzyme and applied for building an easy-to-use analytical device for the detection of polyphenols. The electrochemical biosensor allowed the determination of polyphenols by square wave voltammetry in mixed water-methanol solutions. The system sensitivity was 868.9 ± 1.9nA µM−1, the LOD was 81 nM and the linearity range was comprised between 100 nM and 10 µM. The proposed approach was successfully applied to detect phenolics in blueberry extracts as real samples. Results suggest that SAMN@TA could be a promising, low cost and versatile tool for the creation of nano-bio-conjugates aimed at the development of new electrochemical sensing platforms.

High-performance InGaAs FinFETs with raised source/drain extensions

In this letter we report on high-performance InGaAs FinFETs with optimized on-off trade-off. The InGaAs FinFETs are fabricated on silicon substrate using a CMOS-compatible replacement-metal-gate process. Excellent off-state performance is achieved by introducing source-drain spacers and doped extension regions. Extensions are fabricated using a digital etching process, a cycling etching technique that allows one to carefully control the position of the junction underneath the spacers. FinFETs with gate length of 13 nm show an on-current of 300 μA μm−1 at VDD = 0.5 V and fixed IOFF = 100 nA μm−1, the highest reported for ultra-scaled Si CMOS-compatible III–V FETs.

Amperometric sarcosine biosensor based on hollow magnetic Pt–Fe3O4@C nanospheres

Sarcosine is a recently identified biomarker for prostate cancer. However, the rapid detection methods for sarcosine are relatively lack because of the low concentration and the presence of complicated interfering substances in serum or urine. In this manuscript, hollow nanospheres of Fe3O4 was synthesized and used as carrier to disperse Pt (Pt) nanoparticles. In order to achieve excellent electron transfer ability, we use polyaniline to coat Pt–Fe3O4 nanoparticles, and pyrolyze the polyaniline to carbon (C). Thus, hollow magnetic Pt–Fe3O4@C nanocomposites with good electron transfer ability are formed. The Pt–Fe3O4@C nanocomposites have high catalytic activity and stability. The nanocomposites were immobilized on glassy carbon electrode (GCE) to construct a nonenzyme hydrogen peroxide (H2O2) sensor (Pt–Fe3O4@C/GCE). We further construct a sensitive sarcosine biosensor by immobilizing sarcosine oxidase (SOx) on the Pt–Fe3O4@C/GCE. The high catalytic activity and good biocompatibility of Pt–Fe3O4@C nanocomposites greatly retained the bioactivity of immobilized SOx, and the prepared sarcosine biosensor has good electrocatalytic performance towards sarcosine. It has a linear detection range between 0.5 and 60 μM with a limit of detection (LOD) of 0.43 μM (the signal to noise ratio is 3), and the sensitivity is 3.45 nA μM−1 (48.8 nA μM−1 cm−2), which has the potential to be used for rapid screening of prostate cancer.

Ultrasound‐Induced Wireless Energy Harvesting for Potential Retinal Electrical Stimulation Application

AbstractRetinal electrical stimulation for people with neurodegenerative diseases has shown to be feasible for direct excitation of neurons as a means of restoring vision. In this work, a new electrical stimulation strategy is proposed using ultrasound‐driven wireless energy harvesting technology to convert acoustic energy to electricity through the piezoelectric effect. The design, fabrication, and performance of a millimeter‐scale flexible ultrasound patch that utilizes an environment‐friendly lead‐free piezocomposite are described. A modified dice‐and‐fill technique is used to manufacture the microstructure of the piezocomposite and to generate improved electrical and acoustic properties. The as‐developed device can be attached on a complex surface and be driven by ultrasound to produce adjustable electrical outputs, reaching a maximum output power of 45 mW cm−2. Potential applications for charging energy storage devices and powering commercial electronics using the device are demonstrated. The considerable current signals (e.g., current &gt;72 µA and current density &gt;9.2 nA µm−2) that are higher than the average thresholds of retinal stimulation are also obtained in the ex vivo experiment of an implanted environment, showing great potential to be integrated on implanted biomedical devices for electrical stimulation application.

3D-Flower-Like Copper Sulfide Nanoflake-Decorated Carbon Nanofragments-Modified Glassy Carbon Electrodes for Simultaneous Electrocatalytic Sensing of Co-existing Hydroquinone and Catechol.

A copper sulfide nanoflakes-decorated carbon nanofragments-modified glassy carbon electrode (CuS-CNF/GCE) was fabricated for the electrocatalytic differentiation and determination of hydroquinone (HQ) and catechol (CC). The physicochemical properties of the CuS-CNF were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. The electrocatalytic determination of HQ and CC over the CuS-CNF/GCE was evaluated by cyclic voltammetry and differential pulse voltammetry. An excellent detection limit and sensitivity of the CuS-CNF/GCE are obtained (0.293 µM and 0.259 µM) with a sensitivity of 184 nA µM−1 cm−2 and 208 nA µM−1 cm−2 (S/N=3) for HQ and CC, respectively. In addition, the CuS-CNF/GCE shows a selective identification of HQ and CC over potential interfering metal ions (Zn2+, Na+, K+, NO3−, SO42−, Cl−) and organic compounds (ascorbic acid, glucose), and a satisfactory recovery is also obtained in the spiked water samples. These results suggest that the CuS-CNF/GCE can be used as an efficient electrochemical sensor for the simultaneous determination of co-existing environmental pollutants such as HQ and CC in water environments with high selectivity and acceptable reproducibility.

Dopamine Binding and Analysis in Undiluted Human Serum and Blood by the RNA-Aptamer Electrode.

Specific analysis of such neurotransmitters as dopamine by the aptamer electrodes in biological fluids is detrimentally affected by nonspecific adsorption of media, particularly pronounced at positive charges of the electrode surface at which dopamine oxidizes. Here, we show that dopamine analysis at the RNA-aptamer/cysteamine-modified electrodes is strongly inhibited in undiluted human serum and blood due to nonspecific interfacial adsorption of serum and blood components. We demonstrate that nonspecific adsorption of serum proteins (but not of blood components) could be minimized when analysis is performed in a flow and injections of serum samples are followed by washing steps in a phosphate buffer solution (PBS) carrier. Under those conditions, the dopamine-aptamer binding affinity in whole human serum of (1.9 ± 0.3) × 104 M-1 s-1 was comparable to the (3.7 ± 0.3) × 104 M-1 s-1 found in PBS, and the dopamine oxidation signal linearly depended on the dopamine concentration, providing a sensitivity of analysis of 73 ± 3 nA μM-1 cm-2 and a LOD of 114 ± 8 nM. The flow-injection apatmer-electrode system was used for direct analysis of basal levels of dopamine in undiluted human serum samples, without using any physical separators (membranes) or filtration procedures. The results suggest a simple strategy for combatting biosurface fouling, otherwise most pronounced at positive electrode potentials used for dopamine detection, and assist in designing more efficient antifouling strategies for biomedical applications.

Influence of Electrostatic Interactions Induced via a Nanocomposite Film onto a Glassy Carbon Electrode Used for Highly Selective and Sensitive Ascorbic Acid Detection

A study of the electroanalytical detection of ascorbic acid (AH2) using a glassy carbon electrode (GCE) modified with nanocomposite films constructed with multiwall carbon nanotubes (MWCNT) or functionalized with carboxylic groups (fMWCNT) and gold nanoparticles (AuNP) stabilized with poly(diallyldimethylammonium chloride) (PDDA) or poly(vinylbenzyltrimethylammonium chloride) (pVBA) is presented. A larger loading of AuNP was reached using the fMWCNT instead of the MWCNT, increasing the oxidation current of AH2. However, the modified GCE with the higher electro-analytical response, e.g. GCE/fMWCNT/AuNP@PDDA, also exhibited the adsorption of the analyte onto the electrode, a process that was completely eliminated by attaching a DNA-bioinspired polyanion (P16−) onto the electrode surface. Consequently, the GCE/fMWCNT/AuNP@PDDA/P16− was able to electro-oxidize AH2 thru a diffusion-controlled process, with a sensitivity of (64.6 ± 0.5) nA μM-1 and a detection limit of (75 ± 5) nM at pH 7. The electroanalytical response of the modified GCE was extremely stable over 70 reusing cycles or during several days under certain storage conditions. Additionally, accurate quantification of AH2 was obtained in the presence of interfering compounds or in real complex matrixes. These results indicate the relevance of specific interactions between the electroactive surface and the analyte to obtain better electroanalytical responses.

Biosensor for Monitoring Uric Acid in Wound and Its Proximity: A Potential Wound Diagnostic Tool

This work reports a bi-enzymatic biosensor for monitoring uric acid (UA) in biofluids extracted from wound, perilesional skin and healthy skin. The biosensor is composed of uricase (UOx) as a biocatalyst for UA oxidation, horseradish peroxidase (HRP) for electron transfer and a nanocomposite of multi-walled carbon nanotubes (MWCNTs) and Au nanoparticles (AuNPs) as the substrate. The bi-enzymatic approach provided a two-fold enhancement in current response, while the nanocomposite facilitated higher enzyme loading and fast electron transfer enabling a 2-fold increase in current response. The biosensor was able to measure UA levels in human wound exudate and in biofluids extracted from perilesional and healthy skin. The biosensor exhibited a lowest detectable concentration of 9.91 μM with a sensitivity of 2.5 nA μM−1. The UA levels in wound exudate and biofluid extract from perilesional skin were 3.7 and 1.2 times higher than in healthy skin. This result opened a potential way to use the biofluid in wound proximity as a biomarker for prolonged measurements, preventing electrode occlusion and sensor fouling by the wound debris. The electrode fouling studies demonstrated that the electrode with adsorbed wound exudate had 1.5 times reduction in current compared to electrode adsorbed with biofluid extract from perilesional skin.

Nanocomposite Bienzymatic Sensor for Monitoring Xanthine in Wound Diagnostics

This work reports a biosensor for monitoring xanthine for potential wound healing assessment. Active substrate of the biosensor has xanthine oxidase (XO) and horseradish peroxidase (HRP) physisorbed on a nanocomposite of multiwalled carbon nanotubes (MWCNT) decorated with gold nanoparticles (AuNP). The presence of HRP provided a two-fold increase in response to xanthine, and a three-fold increase in response to the nanocomposite. With a sensitivity of 155.71 nA μM−1 cm−2 the biosensor offers a detection limit of 1.3 μM, with linear response between 22 μM and 0.4 mM. Clinical sample analyses showed the feasibility of xanthine detection from biofluids in a lesion site due to diffusion of the analyte into surrounding biofluids. Higher concentrations by three-fold were observed from wound proximity, than away from injury, with an average recovery of 110%. Results show the feasibility of monitoring wound severity through longitudinal measurements of xanthine from injured vicinity.

Communication—Microfluidic Electrochemical Acetylcholine Detection in the Presence of Chlorpyrifos

An amperometric acetylcholine sensor was developed for use in a microfluidic system and characterized with chlorpyrifos and its metabolite, chlorpyrifos oxon. This enzymatic sensor was highly selective for acetylcholine, with a detection limit of 0.2 μM and sensitivity of 1.7 nA μM−1 from 1–150 μM. Though chlorpyrifos had no effect on sensor function, chlorpyrifos oxon significantly inhibited response across a range of concentrations (0.5–50 μM). Inhibition was reversed by 2-pyridine aldoxime methyl chloride. This platform can be used to both quantify acetylcholine in the presence of chlorpyrifos and as a biorecognition method for chlorpyrifos oxon.

MoS2 based ultra-low-cost, flexible, non-enzymatic and non-invasive electrochemical sensor for highly selective detection of Uric acid in human urine samples

While all reports on electrochemical uric acid (UA) sensors are on rigid electrodes and based on either complex fabrication procedures or multiple steps based synthesis techniques, this paper is the first demonstration of a single step hydrothermally grown MoS2 on aluminium foil (Al) based flexible electrochemical sensor for non-enzymatic detection of UA. FESEM images revealed MoS2 micro-flower like structure comprising of interlaced nanosheets while chemical characterization data confirmed the successful growth of few layered (>4 layers) MoS2 on Al foil. The as-fabricated flexible sensor exhibited a limit of detection of 1.169 μM, a response time of <3 s, excellent reproducibility, selectivity towards UA over glucose, ascorbic acid and urea with a sensitivity of 98.3 ± 1 nA μM−1 (R2 = 0.999) in the dynamic range of 10–400 μM. This enhanced sensing ability can be attributed to high surface area of MoS2, more numbers of active sites resulting from large numbers of defects and edges and higher proportion of metallic 1 T phase than semiconducting 2H phase. The proposed sensor was also successfully evaluated for the detection of UA in a non-invasive sample like human urine and the data corroborates well with the UA concentration obtained from conventional biochemical tests performed in clinical laboratory. This highly sensitive, ultra-low-cost MoS2 based flexible electrochemical sensor paves way for the development of affordable lab on chip devices for a wide range of bioanalytical applications.

Telocinobufagin and Marinobufagin Produce Different Effects in LLC-PK1 Cells: A Case of Functional Selectivity of Bufadienolides.

Bufadienolides are cardiotonic steroids (CTS) identified in mammals. Besides Na+/K+-ATPase inhibition, they activate signal transduction via protein–protein interactions. Diversity of endogenous bufadienolides and mechanisms of action may indicate the presence of functional selectivity and unique cellular outcomes. We evaluated whether the bufadienolides telocinobufagin and marinobufagin induce changes in proliferation or viability of pig kidney (LLC-PK1) cells and the mechanisms involved in these changes. In some experiments, ouabain was used as a positive control. CTS exhibited an inhibitory IC50 of 0.20 (telocinobufagin), 0.14 (ouabain), and 3.40 μM (marinobufagin) for pig kidney Na+/K+-ATPase activity and concentrations that barely inhibited it were tested in LLC-PK1 cells. CTS induced rapid ERK1/2 phosphorylation, but corresponding proliferative response was observed for marinobufagin and ouabain instead of telocinobufagin. Telocinobufagin increased Bax:Bcl-2 expression ratio, sub-G0 cell cycle phase and pyknotic nuclei, indicating apoptosis. Src and MEK1/2 inhibitors blunted marinobufagin but not telocinobufagin effect, which was also not mediated by p38, JNK1/2, and PI3K. However, BIO, a GSK-3β inhibitor, reduced proliferation and, as telocinobufagin, phosphorylated GSK-3β at inhibitory Ser9. Combination of both drugs resulted in synergistic antiproliferative effect. Wnt reporter activity assay showed that telocinobufagin impaired Wnt/β-catenin pathway by acting upstream to β-catenin stabilization. Our findings support that mammalian endogenous bufadienolides may exhibit functional selectivity.

Micro additive manufacturing of glucose biosensors: A feasibility study

Flexible electrochemical sensors for measurement and quantification of biomarkers are attracting a great deal of attention in non-invasive medical applications, due to their high mechanical compatibility and conformability with the human body. Realization of the full potential of such novel systems relies heavily on their effective manufacturing. Particularly, there is a need for manufacturing techniques that can realize complex designs, consisting of multiple functional materials which are required for sensor functionality. Among emerging additive manufacturing techniques, Direct-Ink-Writing (DIW), where polymer nanocomposite inks are dispensed through nozzles and deposited with high spatial control, carries a great potential to address this need. Here, we introduce a 3D printed flexible electrochemical biosensor for glucose detection. We show that our biosensor works linearly in glucose solution with a concentration range between 100 and 1000 μM. The sensitivity of glucose biosensor is estimated to be 17.5 nA μM−1, and the calculated value of the detection limit (S/N = 3) is 6.9 μM. The demonstrated electrochemical performance and surface properties of the printed sensors show the promising advantages of using this technique over the conventional screen printing method. These advantages include higher sensitivity and specificity and, reduced material consumption.