Advances in heart failure monitoring: Biosensors targeting molecular markers in peripheral bio-fluids.

Cardiovascular diseases (CVDs), especially chronic heart failure, threaten many patients' lives worldwide. Because of its slow course and complex causes, its clinical screening, diagnosis, and prognosis are essential challenges. Clinical biomarkers and biosensor technologies can rapidly screen and diagnose. Multiple types of biomarkers are employed for screening purposes, precise diagnosis, and treatment follow-up. This article provides an up-to-date overview of the biomarkers associated with the six main heart failure etiology pathways. Plasma natriuretic peptides (BNP and NT-proBNP) and cardiac troponins (cTnT, cTnl) are still analyzed as gold-standard markers for heart failure. Other complementary biomarkers include growth differentiation factor 15 (GDF-15), circulating Galactose Lectin 3 (Gal-3), soluble interleukin (sST2), C-reactive protein (CRP), and tumor necrosis factor-alpha (TNF-α). For these biomarkers, the electrochemical biosensors have exhibited sufficient sensitivity, detection limit, and specificity. This review systematically summarizes the latest molecular biomarkers and sensors for heart failure, which will provide comprehensive and cutting-edge authoritative scientific information for biomedical and electronic-sensing researchers in the field of heart failure, as well as patients. In addition, our proposed future outlook may provide new research ideas for researchers.

Advances in Electrochemical Biosensors Based on Nanomaterials for Protein Biomarker Detection in Saliva.

The focus on precise medicine enhances the need for timely diagnosis and frequent monitoring of chronic diseases. Moreover, the recent pandemic of severe acute respiratory syndrome coronavirus 2 poses a great demand for rapid detection and surveillance of viral infections. The detection of protein biomarkers and antigens in the saliva allows rapid identification of diseases or disease changes in scenarios where and when the test response at the point of care is mandated. While traditional methods of protein testing fail to provide the desired fast results, electrochemical biosensors based on nanomaterials hold perfect characteristics for the detection of biomarkers in point-of-care settings. The recent advances in electrochemical sensors for salivary protein detection are critically reviewed in this work, with emphasis on the role of nanomaterials to boost the biosensor analytical performance and increase the reliability of the test in human saliva samples. Furthermore, this work identifies the critical factors for further modernization of the nanomaterial-based electrochemical sensors, envisaging the development and implementation of next-generation sample-in-answer-out systems.

Electrochemical methods for detection of biomarkers of Chronic Obstructive Pulmonary Disease in serum and saliva.

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death nowadays, and its underdiagnosis is still a great challenge. More effective diagnosis method is in urgent need since the traditional spirometry has many limitations in the practical application. The electrochemical (EC) detection methods have their unique advantages of high accuracy, short response time and easy integration of the system. In this review, recent works on the EC methods for COPD biomarkers including interleukin 6 (IL-6), interleukin 8 (IL-8) and C-reactive protein (CRP) are summarized. Five types of EC methods are highlighted in this study, as enzyme-labelled immunosensors, nanoparticle-labelled immunosensors, capacitive or impedimetric immunosensors, magnetoimmunosensors, and field effect transistor (FET) immunosensors. To date, EC immunosensors have been exhibiting high analytical performance with a detection limit that can achieve several pg/mL or even lower. The simplicity of EC immunosensors makes them a perfect solution for a future point-of-care device to use in settings for COPD diagnosis and follow-up. Nevertheless, more efforts need to be paid on the simultaneous detection of multiple biomarkers, a demand for the clinical diagnosis, and processes of assay simplification towards achieving one-step detection.

A fluorimetric nitrite biosensor with polythienothiophene-fullerene thin film detectors for on-site water monitoring.

A novel fluorimetric sensor for highly sensitive nitrite detection on the site is presented in this study. The proposed on-chip approach comprises the use of integrated polymer photodetectors to detect light from fluorescence reactions with a diaminofluorescein probe. The detectors were prepared with a heterostructured nanofilm of polythieno[3,4-b]thiophene/benzodithiophene and (6,6)-phenyl-C71-butyric-acid methyl-ester as a photoactive layer. Prior to fluorimetric detection, the quality of the spin-coated photoactive layer was characterized via nano-morphology and current-density measurements. Nitrite assays were conducted on a poly(methyl methacrylate) microchannel chip, to which polythienothiophene-C71 based detectors were aligned. Results of signal-to-noise ratio determination have indicated a detection limit below 0.55 µM, lower than the 0.1 mg L-1 maximum limit of operation in recirculating aquaculture systems for farming Atlantic salmon Salmo salar. An increase of the nitrite concentration to toxic levels may therefore be possible to detect. The fluorimetric sensor exhibited good linearity over three orders of magnitude and acceptable detection reproducibility, which confirmed its analytical value. Further tests revealed great promise of the integrated biosensor device for detecting nitrite in aquaculture-relevant samples with high precision. The approach reported hereby may provide impetus to in situ analytical tools for monitoring water quality at aquaculture facilities, the food industries or water monitoring stations.

Immunodetection of salivary biomarkers by an optical microfluidic biosensor with polyethylenimine-modified polythiophene-C70 organic photodetectors.

This work reports a novel optical microfluidic biosensor with highly sensitive organic photodetectors (OPDs) for absorbance-based detection of salivary protein biomarkers at the point of care. The compact and miniaturized biosensor has comprised OPDs made of polythiophene-C70 bulk heterojunction for the photoactive layer; whilst a calcium-free cathode interfacial layer, made of linear polyethylenimine, was incorporated to the photodetectors to enhance the low cost. The OPDs realized onto a glass chip were aligned to antibody-functionalized chambers of a poly(methyl methacrylate) microfluidic chip, in where immunogold-silver assays were conducted. The biosensor has detected IL-8, IL-1ß and MMP-8 protein in spiked saliva with high detection specificity and short analysis time exhibiting detection limits between 80pgmL-1 and 120pgmL-1. The result for IL-8 was below the clinical established cut-off of 600pgmL-1, which revealed the potential of the biosensor to early detection of oral cancer. The detection limit was also comparable to other previously reported immunosensors performed with bulky instrumentation or using inorganic photodetectors. The optical detection sensitivity of the polythiophene-C70 OPD was enhanced by optimizing the thickness of the photoactive layer and anode interfacial layer prior to the saliva immunoassays. Further, the biosensor was tested with unspiked human saliva samples, and the results of measuring IL-8 and IL-1ß were in statistical agreement with those provided by two commercial assays of ELISA. The optical microfluidic biosensor reported hereby offers an attractive and cost-effective tool to diagnostics or screening purposes at the point of care.

Blood pressure decrease in spontaneously hypertensive rats folowing renal denervation or dopamine ß-hydroxylase inhibition with etamicastat.

Overactivity of the sympathetic nervous system has an important role in the development and progression of arterial hypertension. Catheter-based renal nerve ablation for the treatment of drug-resistant hypertension has recently been developed. An alternative strategy for the modulation of sympathetic nerve function is to reduce the biosynthesis of noradrenaline (NA) by inhibiting dopamine ß-hydroxylase (DßH), the enzyme that catalyzes the conversion of dopamine (DA) to NA in the sympathetic nerves. Renal denervation (RDN) surgery was performed in spontaneously hypertensive rats (SHR) to evaluate the effect of RDN on the DA and NA levels and on blood pressure over a 28-day period. The selective peripheral DßH inhibitor etamicastat (30 mg kg (-1)day(-1)) was administered to another cohort of SHR. RDN and etamicastat treatment had no effect on the renal function, as assessed by measuring the water balance response, renal function and urinary electrolyte levels. RDN significantly decreased the systolic blood pressure (SBP) and the diastolic blood pressure (DBP). A gradual return of the SBP and the DBP to the high baseline levels was observed over time. Conversely, treatment with etamicastat resulted in a significant decrease in the SBP and the DBP at all time points. On the last day of the assessment, NA levels in renal tissue were significantly decreased in both RDN and etamicastat-treated groups. In contrast, the NA levels in the left ventricle were decreased only in the etamicastat-treated group. Thus, RDN produces transitory decreases in blood pressure, whereas prolonged downregulation of sympathetic drive with the DßH inhibitor etamicastat results in a sustained decrease in the SBP and the DBP.

Cardiovascular safety pharmacology profile of etamicastat, a novel peripheral selective dopamine-ß-hydroxylase inhibitor.

Etamicastat, a peripheral reversible dopamine-ß-hydroxylase inhibitor, blocked the hERG current amplitude with an IC50 value of 44.0µg/ml in HEK 293 cells. At 0.3 and 3µg/ml, etamicastat had no effects on the action potential (AP) in male dog Purkinje fibers. At 30µg/ml, etamicastat significantly affected resting membrane potential (+4%), AP amplitude (-4%), AP duration at 60% (-14%) and AP duration at 90% (+5%) repolarization, and AP triangulation (+79%). In the telemetered conscious male dog, etamicastat (up to 20mg/kg) had no effects on arterial blood pressure, heart rate and the PR interval. At 10 and 20mg/kg, the QTc interval was slightly prolonged (8-9% max, P<0.05). No arrhythmia or other changes in the morphology of the ECG were observed. The maximum observed plasma concentrations (Cmax) of etamicastat (i.e. 3h post-administration) were 1.4 and 3.7µg/ml at 10 and 20mg/kg, respectively. No deleterious effects, including ECG disturbance were observed in male and female dogs dosed by gavage with etamicastat (up to 20mg/kg/day) for 28 days. Mean plasma Cmax etamicastat levels ranged between 2.4 and 6.3µg/ml on Day 1 and Day 28 of treatment, respectively. It is concluded that the blockade of the delayed rectifier potassium channels by etamicastat together with the QTc interval prolongation observed in conscious dogs can be considered as modest with respect to the measured plasmatic concentrations. These findings suggest that etamicastat is not likely to prolong the QT interval at therapeutic doses (~0.2µg/ml).

Characterization of the interaction of the novel antihypertensive etamicastat with human dopamine-ß-hydroxylase: comparison with nepicastat.

The interaction of etamicastat, a novel peripherally acting dopamine-ß-hydroxylase (DBH) inhibitor, with the enzyme was studied using a classical kinetic approach and the pharmacodynamics effect of the compound upon administration to rats was also evaluated. SK-N-SH cell homogenates convert tyramine into octopamine with a Km value of 9 mM, and a Vmax of 1747 nmol/mg protein/h. The K(m) value for ascorbate was 3 mM. The inhibition of DBH by etamicastat and nepicastat, a known centrally acting DBH inhibitor, with IC50 values of 107 and 40 nM, respectively, was fully reversed by dilution. Non-linear fitting of the velocities, determined at various concentrations of substrate (tyramine) and co-substrate (ascorbic acid), and of etamicastat and nepicastat, indicated that the inhibition of DBH by both compounds follows a mixed-model inhibition mechanism, approaching competitive behavior with regards to the substrate tyramine, with K(i) values of 34 and 11 nM, respectively. Relatively to ascorbate, both compounds followed a mixed-model inhibition mechanism, approaching uncompetitive behavior. Oral administration of both compounds (at 30 mg/kg) inhibited adrenal DBH activity over time and significantly decreased noradrenaline levels in the heart. Nepicastat also decreased noradrenaline levels in the parietal cortex, but not etamicastat. Both compounds significantly decreased systolic and diastolic blood pressure in spontaneously hypertensive rats. In conclusion, etamicastat and nepicastat behave as multisubstrate DBH inhibitors, binding reversibly and preferentially to the reduced form of the enzyme, and simultaneously at the substrate and oxygen binding sites. Etamicastat, in contrast to nepicastat, offers the advantage of peripheral selectivity without central effects.

Targeting pharmacoresistant epilepsy and epileptogenesis with a dual-purpose antiepileptic drug.

In human epilepsy, pharmacoresistance to antiepileptic drug therapy is a major problem affecting a substantial fraction of patients. Many of the currently available antiepileptic drugs target voltage-gated sodium channels, leading to a rate-dependent suppression of neuronal discharge. A loss of use-dependent block has emerged as a potential cellular mechanism of pharmacoresistance for anticonvulsants acting on voltage-gated sodium channels. There is a need both for compounds that overcome this resistance mechanism and for novel drugs that inhibit the process of epileptogenesis. We show that eslicarbazepine acetate, a once-daily antiepileptic drug, may constitute a candidate compound that addresses both issues. Eslicarbazepine acetate is converted extensively to eslicarbazepine after oral administration. We have first tested using patch-clamp recording in human and rat hippocampal slices if eslicarbazepine, the major active metabolite of eslicarbazepine acetate, shows maintained activity in chronically epileptic tissue. We show that eslicarbazepine exhibits maintained use-dependent blocking effects both in human and experimental epilepsy with significant add-on effects to carbamazepine in human epilepsy. Second, we show that eslicarbazepine acetate also inhibits Cav3.2 T-type Ca(2+) channels, which have been shown to be key mediators of epileptogenesis. We then examined if transitory administration of eslicarbazepine acetate (once daily for 6 weeks, 150 mg/kg or 300 mg/kg) after induction of epilepsy in mice has an effect on the development of chronic seizures and neuropathological correlates of chronic epilepsy. We found that eslicarbazepine acetate exhibits strong antiepileptogenic effects in experimental epilepsy. EEG monitoring showed that transitory eslicarbazepine acetate treatment resulted in a significant decrease in seizure activity at the chronic state, 8 weeks after the end of treatment. Moreover, eslicarbazepine acetate treatment resulted in a significant decrease in mossy fibre sprouting into the inner molecular layer of pilocarpine-injected mice, as detected by Timm staining. In addition, epileptic animals treated with 150 mg/kg, but not those that received 300 mg/kg eslicarbazepine acetate showed an attenuated neuronal loss. These results indicate that eslicarbazepine potentially overcomes a cellular resistance mechanism to conventional antiepileptic drugs and at the same time constitutes a potent antiepileptogenic agent.

Blood pressure-decreasing effect of etamicastat alone and in combination with antihypertensive drugs in the spontaneously hypertensive rat.

Hyperactivation of the sympathetic nervous system has an important role in the development and progression of arterial hypertension. This study evaluated the efficacy of etamicastat, a dopamine-ß-hydroxylase (DßH) inhibitor, in controlling high blood pressure in the spontaneously hypertensive rat (SHR), either alone or in combination with other classes of antihypertensives. SHRs were administered with etamicastat by gavage, and its pharmacodynamic and pharmacokinetic properties were evaluated. Etamicastat induced a time-dependent decrease in noradrenaline-to-dopamine ratios in the heart and kidney, and had no effect on catecholamine levels in the frontal cortex of SHRs. Cardiovascular pharmacodynamic effects following administration of etamicastat alone or in combination with other classes of antihypertensive drugs were assessed by telemetry. Etamicastat was evaluated in combination with captopril, losartan, hydrochlorothiazide, metoprolol, prazosin and/or diltiazem. Etamicastat monotherapy induced a dose-dependent reduction in blood pressure without reflex tachycardia. Combination therapy amplified the antihypertensive effects of all tested drugs. In conclusion, inhibition of peripheral DßH with etamicastat, as a monotherapy or combination therapy, may constitute a valid alternative treatment for high blood pressure.

Recent developments in optical detection technologies in lab-on-a-chip devices for biosensing applications.

The field of microfluidics has yet to develop practical devices that provide real clinical value. One of the main reasons for this is the difficulty in realizing low-cost, sensitive, reproducible, and portable analyte detection microfluidic systems. Previous research has addressed two main approaches for the detection technologies in lab-on-a-chip devices: (a) study of the compatibility of conventional instrumentation with microfluidic structures, and (b) integration of innovative sensors contained within the microfluidic system. Despite the recent advances in electrochemical and mechanical based sensors, their drawbacks pose important challenges to their application in disposable microfluidic devices. Instead, optical detection remains an attractive solution for lab-on-a-chip devices, because of the ubiquity of the optical methods in the laboratory. Besides, robust and cost-effective devices for use in the field can be realized by integrating proper optical detection technologies on chips. This review examines the recent developments in detection technologies applied to microfluidic biosensors, especially addressing several optical methods, including fluorescence, chemiluminescence, absorbance and surface plasmon resonance.

A cascade-like silicon filter for improved recovery of oocysts from environmental waters.

Standard filtration methods have been characterized by poor recoveries when processing large-volume samples of environmental water. A method to pre-remove particulates present in turbid waters would be necessary to enhance recovery of protozoan oocysts. Particulate separation can be achieved by the proposed multiplex particle refining (MPR) system. This system employs multiple counter-flow microfiltration units that are arranged into a cascade-like structure. By use of this design, the target oocysts are pre-concentrated from environmental waters. The performance of the MPR system was investigated using 10-L deionized water and surface water spiked with 100 Cryptosporidium parvum oocysts. A recovery rate of around 85% was obtained for spiked river water. The water samples were processed using high flow rate and a simple filtration protocol. Further experiments were conducted using the MPR as a pre-filter for five commercially available filters. The recovery rates were two- to threefold higher employing the pre-filter than using the filters alone. The merit of the refining system to use different numbers of counter-flow units led to superior oocyst recovery rate for the Filta-Max and Envirochek HV filters, which are approved by the US Environmental Protection Agency. This work demonstrates a feasible tool for improved filtration performance in environmental waters.

Ultrasensitive opto-microfluidic immunosensor integrating gold nanoparticle-enhanced chemiluminescence and highly stable organic photodetector.

The expensive fabrication of current opto-microfluidic sensors is a barrier to the successful adoption of these devices in point-of-care testing. This work reports a simple inexpensive opto-microfluidic device incorporating a poly(dimethylsiloxane)-glass hybrid microfluidic chip modified with gold nanoparticles and a high-detectivity, high-stability organic photodetector. The enhancing effect of the gold nanoparticles on horseradish peroxidase-luminol-H2O2 chemiluminescence was exploited in rapid single-analyte immunoassays. The limit of detection for 17-ß estradiol was 2.5 pg/ml, which is ∼200 times more sensitive than previously reported chemiluminescent immunosensors employing other organic photodetectors. Detection was also demonstrated in complex media, including natural water and blood serum.

Microfluidic biosensor array with integrated poly(2,7-carbazole)/fullerene-based photodiodes for rapid multiplexed detection of pathogens.

A multiplexed microfluidic biosensor made of poly(methylmethacrylate) (PMMA) was integrated into an array of organic blend heterojunction photodiodes (OPDs) for chemiluminescent detection of pathogens. Waterborne Escherichia coli O157:H7, Campylobacter jejuni and adenovirus were targeted in the PMMA chip, and detection of captured pathogens was conducted by poly(2,7-carbazole)/fullerene OPDs which showed a responsivity over 0.20 A/W at 425 nm. The limits of chemiluminescent detection were 5 × 10(5) cells/mL for E. coli, 1 × 10(5) cells/mL for C. jejuni, and 1 × 10(-8) mg/mL for adenovirus. Parallel analysis for all three analytes in less than 35 min was demonstrated. Further recovery tests illustrated the potential of the integrated biosensor for detecting bacteria in real water samples.

Integrated optical microfluidic biosensor using a polycarbazole photodetector for point-of-care detection of hormonal compounds.

A picogram-sensitive optical microfluidic biosensor using an integrated polycarbazole photodiode is developed. The photodetector is mainly composed of the blend heterojunction of poly [N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C71-butyric acid methyl ester (PC70BM) and the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as the hole transport layer. Analyte detection is accomplished via a chemiluminescent immunoassay performed in a poly(dimethylsiloxane)-gold-glass hybrid microchip, on which antibodies were immobilized and chemiluminescent horseradish peroxidase-luminol-peroxide reactions were generated. Enhanced sensor response to the chemiluminescent light is achieved by optimizing the thickness of PCDTBT: PC70BM and PEDOT:PSS. Using the optimized polycarbazole photodiode for detecting the human thyroid-stimulating hormone as the model target, the integrated biosensor demonstrates an excellent linearity in the range of 0.03 to 10 ng/ml with an analytical sensitivity of 68 pg/ml. The sensor response shows high specificity and reproducibility. Hormone detection in clinical samples is further demonstrated and compared with a commercial enzyme-linked immunosorbent assay. The integrated device reported here has potential to detect other hormonal compounds or protein targets. Moreover, the presented concept enables the development of miniaturized, low-cost but highly sensitive optical microfluidic biosensors based on integrated polymer photodetectors with high potential for point-of-care diagnostics.

Recovery of Cryptosporidium and Giardia organisms from surface water by counter-flow refining microfiltration.

As waterborne parasitic cryptosporidiosis and giardiasis outbreaks continue globally, monitoring of Cryptosporidium parvum and Giardia lamblia in surface water continues to be challenging. Lack of non-clogging and high-efficiency methods for recovery of C. parvum oocysts and G. lamblia cysts in environmental water strongly limits the sensitivity of detection methods for these protozoan organisms. In this work, the Counter-Flow Micro-Refinery (CFMR) system was developed by employing the novel counter-flow microfiltration principle to enrich (oo)cysts for subsequent analytical purposes. The CFMR system was constructed with multiple counter-flow concentration units that were arranged into two refining levels. By use of different numbers of units, the CFMR offered an adjustable concentration ratio allowing the concentration of 10 L and 100 L to hundreds of mL with no recirculation processing. With spiked samples, recovery of 81.3% oocysts and 86.2% cysts at a variance of < 7% was achieved for concentrations as low as 0.5-100 organisms L(-1). The recovery efficiency showed consistent for a wide range of water turbidities as well as different sample volumes. No significant clogging has been observed in the experiments. Moreover, the refining filter was able to enrich and separate oocysts and cysts in water, simultaneously. This work verifies a feasible solution for recovering C. parvum oocysts and G. lamblia cysts in large-volume surface waters. The refining system has potential to be a high-efficiency monitoring tool when combined with proper analytical detection methods.

WITHDRAWN: Multiplex particle refining system to enhance Cryptosporidium recovery for surface water filtration methods.

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.org/doi:10.1016/j.mimet.2012.12.009. The duplicate article has therefore been withdrawn.