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Electrochemical sensors based on antibody-antigen recognition events are commonly used for the rapid, label-free, and sensitive detection of various analytes. However, various parameters at the bioelectronic interface, i.e., before and after the probe (such as an antibody) assembly onto the electrode, have a dominant influence on the underlying detection performance of analytes (such as an antigen). In this work, we thoroughly investigate the dependence of the bioelectronic interface characteristics on parameters that have not been investigated in depth: the antibody density on the electrode’s surface and the antigen incubation time. For this important aim, we utilized the sensitive non-faradaic electrochemical impedance spectroscopy method. We showed that as the incubation time of the antigen-containing drop solution increased, a decrease was observed in both the solution resistance and the diffusional resistance with reflecting boundary elements, as well as the capacitive magnitude of a constant phase element, which decreased at a rate of 160 ± 30 kΩ/min, 800 ± 100 mΩ/min, and 520 ± 80 pF × s(α-1)/min, respectively. Using atomic force microscopy, we also showed that high antibody density led to thicker electrode coating than low antibody density, with root-mean-square roughness values of 2.2 ± 0.2 nm versus 1.28 ± 0.04 nm, respectively. Furthermore, we showed that as the antigen accumulated onto the electrode, the solution resistance increased for high antibody density and decreased for low antibody density. Finally, the antigen detection performance test yielded a better limit of detection for low antibody density than for high antibody density (0.26 μM vs 2.2 μM). Overall, we show here the importance of these two factors and how changing one parameter can drastically affect the desired outcome. Graphical abstract Electronic supplementary material The online version of this article (10.1007/s00216-020-02417-x) contains supplementary material, which is available to authorized users.

Olanzapine is a thienobenzodiazepine compound. It is one of the newer types of antipsychotic drugs used in the treatment of schizophrenia and other psychotic disorders. Several methods have been reported for analyzing olanzapine in its pure form or combined with other drugs and in biological fluids. These methods include high-performance liquid chromatography and liquid chromatography-tandem mass spectroscopy. Although many of the reported methods are accurate and sensitive, they require the use of sophisticated equipment, lack in situ analysis, and require expensive reagents. Moreover, several of these methods are cumbersome, require prolonged sample pretreatment, strict control of pH, and long reaction times. Here we present the development of a miniaturized electrochemical sensor that will enable minimally invasive, real-time, and in situ monitoring of olanzapine levels in microliter volumes of serum samples. For this purpose, we modified a microfabricated microelectrode with a platinum black film to increase the electrocatalytic activity of the microelectrode towards olanzapine oxidation; this improved the overall selectivity and sensitivity of the sensor. We observed in recorded voltammograms the anodic current dose response characteristics in microliter volumes of olanzapine-spiked serum samples that resulted in a limit of detection of 28.6 ± 1.3 nM and a sensitivity of 0.14 ± 0.02 µA/cm2 nM. Importantly, the platinum black-modified microelectrode exhibited a limit of detection that is below the clinical threshold (65–130 nM). Further miniaturizing and integrating such sensors into point-of-care devices provide real-time monitoring of olanzapine blood levels; this will enable treatment teams to receive feedback and administer adjustable olanzapine therapy.

Hydroxyurea, an oral medication with important clinical benefits in the treatment of sickle cell anemia, can be accurately determined in plasma with a transition metal dichalcogenide-based electrochemical sensor. We used a two-dimensional molybdenum sulfide material (MoS2) selectively electrodeposited on a polycrystalline gold electrode via tailored waveform polarization in the gold electrical double layer formation region. The electro-activity of the modified electrode depends on the electrical waveform parameters used to electro-deposit MoS2. The concomitant oxidation of the MoS2 material during its electrodeposition allows for the tuning of the sensor&rsquo, s specificity. Chemometrics, utilizing mathematical procedures such as principal component analysis and multivariable partial least square regression, were used to process the electrochemical data generated at the bare and the modified electrodes, thus allowing the hydroxyurea concentrations to be predicted in human plasma. A limit-of-detection of 22 nM and a sensitivity of 37 nA cm&minus, 2 &micro, M&minus, 1 were found to be suitable for pharmaceutical and clinical applications.

Classically, the need for highly sophisticated instruments with important economic costs has been a major limiting factor for clinical pathology laboratories, especially in developing countries. With the aim of making clinical pathology more accessible, a wide variety of free or economical technologies have been developed worldwide in the last few years. 3D printing and Arduino approaches can provide up to 94% economical savings in hardware and instrumentation in comparison to commercial alternatives. The vast selection of point-of-care-tests (POCT) currently available also limits the need for specific instruments or personnel, as they can be used almost anywhere and by anyone. Lastly, there are dozens of free and libre digital tools available in health informatics. This review provides an overview of the state-of-the-art on cost-effective alternatives with applications in routine clinical pathology laboratories. In this context, a variety of technologies including 3D printing and Arduino, lateral flow assays, plasmonic biosensors, and microfluidics, as well as laboratory information systems, are discussed. This review aims to serve as an introduction to different technologies that can make clinical pathology more accessible and, therefore, contribute to achieve universal health coverage.

Microfluidics is a highly useful platform for culturing, monitoring, and testing biological cells. The integration of electrodes into microfluidic channels extends the functionality, sensing, and testing capabilities of microfluidic systems. By employing an electrochemical impedance spectroscopy (EIS) technique, the non-invasive, label-free detection of the activities of cells in real-time can be achieved. To address the movement toward spatially resolving cells in cell culture, we developed a sensory system capable of electro-addressing cell location within a microfluidic channel. This simple system allows for real-time cell location, integrity monitoring (of barrier producing cells), and confluency sensing without the need for frequent optical evaluation—saving time. EIS results demonstrate that cells within microfluidic channels can be located between various pairs of electrodes at different positions along the length of the device. Impedance spectra clearly differentiates between empty, sparse, and confluent microfluidic channels. The system also senses the level of cell confluence between electrode pairs—allowing for the relative quantification of cells in different areas of the microfluidic channel. The system’s electrode layout can easily be incorporated into other devices. Namely, organ-on-a-chip devices, that require the monitoring of precise cell location and confluency levels for understanding tissue function, modeling diseases, and for testing therapeutics.

Dopamine functions as a neurotransmitter in the brain. The dysfunction of the dopaminergic system is the leading cause of numerous diseases such as Parkinson’s disease. Hence, it is important to find selective and sensitive detection methods for the early diagnosis of diseases related to the abnormal levels of dopamine. In this study, we show a new electrochemical sensing platform based on carbon nanotube (SWCNT) and a sheet of graphene (GRA). The novelty of our sensor is the coating of the substrates with chitosan-catechol (CC) by electrodeposition, enhancing the dopamine response by 70%. The dose-response for each set of electrodes (bare CNT, bare GRA, and coated CNT as well as coated GRA) was measured. Finally, the electrodes were tested in cerebrospinal fluid (artificial and human), for the detection of millimolar to nanomolar levels of dopamine. The electrodes exhibited high sensitivity (2.03mA mol·L-1, 1.45 mA mol·L-1, 0.0298 mA mol·L-1, and 0.0559 mA mol·L-1 for the modified CNT, bare CNT, modified GRA and bare GRA, respectively, for the oxidation of DA. The oxidation peak current was proportional to the concentration of DA in the range from 50×10-6 to 50x10-9 M (n= 6, r2 =0.98). The dopamine recovery in human CSF were, 49-78% and 65-65% with coated graphene and CNT electrodes, respectively. Our results indicate that the CC modified CNT electrodes achieved the best recovery, sensitivity, limit of detection, and selectivity compared to the uncoated CNT as well as the coated and uncoated graphene electrodes.

Schizophrenia (SCZ) is a chronic mental disorder that affects 23 million people worldwide. Clozapine (CLZ) is the most effective antipsychotic medication for treatment-resistant SCZ patients. Despite the superior efficacy of CLZ, it is dramatically underutilized due to the unavailable objective tests to measure CLZ efficacy. Several redox biomarkers in the blood have been correlated to CLZ efficacy. Yet, existing analytical methods change the levels of the molecules, their redox state, and eventually destroy the sample. By bridging the analytical gap and profiling the redox biomarkers, rapid and accurate CLZ treatment efficacy monitoring can be provided. Our overall goal is to develop a novel intelligent electrochemical biosensor based on an array of microelectrodes for CLZ treatment efficacy analysis. Here, we present the fabrication of the microelectrodes array, modification of the array with diffusion-limiting films, and characterization of the film’s effect on the generated electrochemical activity. The novelty of the biosensor lies within an array of microelectrodes modified with the positively charged biopolymer chitosan generating a set of complex electrochemical signals that are analyzed by using intelligent chemometric models. To achieve our goal, we microfabricated an array of 24 gold microelectrodes (100-µm-diameter working and 1,500-µm-diameter counter electrodes) by using photolithography and thin film deposition techniques. We used a 1.2% chitosan solution and applied cathodic current to electrodeposit thin films of chitosan onto the microelectrodes. To fabricate chitosan films with similar thicknesses and different densities, we measured the relationship between the thickness of the electrodeposited film and the applied electrodeposition current for 90s and 180s durations. A similar wet chitosan thickness (57.6±0.8 µm) was successfully achieved with 510 nA for 90s and 950 nA for 180s durations. Moreover, different dry chitosan thicknesses were obtained for 90s (10.7±0.1 µm) and 180s (13.2±0.6 µm) durations. Therefore, we calculated the porosity of the electrodeposited films as the ratio between the thicknesses of the wet and the dry films (5.38±0.09 and 4.36±0.20 at 510 nA for 90s and 950 nA for 180s, respectively). Furthermore, we used cyclic voltammetry to characterize the permeability of the modified films by measuring the ratio of the electrochemical signals generated from differently charged redox molecules (negatively charged ferrocyanide, neutral ferrocene, and positively charged hexaammineruthenium) before and after the modification. Statistical T-test analysis of the resulted permeabilities revealed significant differences for the charged molecules (P=0.85% for ferrocyanide; P=4.57% for hexaammineruthenium), while no significant difference was observed for the neutral molecule ferrocene. By providing a new way to analyze molecular profiles in blood, we anticipate establishing a new detection scheme for CLZ treatment efficacy that will help to transform schizophrenia management.

Schizophrenia is a challenging mental health disorder [1]. While various antipsychotics have [...]

This work presents the development of an electrochemical microsystem for antipsychotic clozapine treatment monitoring in schizophrenia patients. In our previous work, we demonstrated clozapine detection directly in spiked whole blood samples of a healthy volunteer using a chitosan–carbon nanotube-modified microelectrode with external counter and reference electrodes. Here we present the miniaturization of our previous clozapine sensing approach and its clinical validation in real samples obtained from 10 schizophrenia patients. We observed a sensitivity of 0.02 ± 2.3 × 10-4 mA/cm2µM and 0.003 ± 2.6 × 10-4 mA/cm2µM and a limit of detection of 0.08 ± 9.2 × 10-4 µM and 0.45 ± 0.04 µM using chitosan–carbon nanotube-modified microelectrodes in a 20 µL volume of spiked capillary plasma and capillary whole blood. Following a calibration curve, which was obtained from spiked samples of patients prior to clozapine therapy administration, clozapine capillary plasma and whole blood levels were recovered from patients’ samples after treatment with clozapine. The developed electrochemical microsystem allows clozapine analysis in a microliter volume of finger-pricked whole blood samples of schizophrenia patients without using any pretreatment steps. By further miniaturization and integration of this sensor into a point-of-care testing device, schizophrenia treatment management can be improved.

In situ analysis of multiple biomarkers in the body provides better diagnosis and enables personalized health management. Since many of these biomarkers are redox-active, electrochemical sensors have shown promising analytical capabilities to measure multiple redox-active molecules. However, the analytical performance of electrochemical sensors rapidly decreases in the presence of multicomponent biofluids due to their limited ability to separate overlapping electrochemical signals generated by multiple molecules. Here we report a novel approach to use charged chitosan-modified electrodes to alter the diffusion of ascorbic acid, clozapine, L-homocysteine, and uric acid—test molecules with various molecular charges and molecular weights. Moreover, we present a complementary approach to use chemometrics to decipher the complex set of overlapping signals generated from a mixture of differentially charged redox molecules. The partial least square regression model predicted three out of four redox-active molecules with root mean square error, Pearson correlation coefficient, and R-squared values of 125 µM, 0.947, and 0.894; 51.8 µM, 0.877, and 0.753; 55.7 µM, 0.903, and 0.809, respectively. By further enhancing our understanding of the diffusion of redox-active molecules in chitosan, the in-situ separation of multiple molecules can be enabled, which will be used to establish guidelines for the effective separation of biomarkers.

In vivo monitoring of the neurotransmitter dopamine can potentially improve the diagnosis of neurological disorders and elucidate their underlying biochemical mechanisms. While electrochemical sensors can detect unlabeled dopamine molecules, their sensing performance is dramatically reduced by electrochemical currents generated by other, interfering molecules (e.g., uric acid) in the biological environment. To overcome this caveat, the surface of the sensor is often modified with electrocatalytic materials, which are encapsulated inside a polymeric film; however, the effect of the encapsulating film on the sensing performance of the electrode has not been systematically studied. This study characterizes the effect of loading carbon nanotubes (CNTs) onto a chitosan film on the electrochemical sensing performance of dopamine in the presence of uric acid. Higher CNT loading increases the diffusion and electron transfer rate coefficients of the sensor and, in the presence of uric acid, provides better sensitivity (3.00 µA L µmol−1 for 1.75% CNT loading, vs 0.01 µA L µmol−1 for 1% loading) but a poorer limit-of-detection (2.00 µmol L−1 vs 1.00, respectively), as reported here for the first time. These findings can help optimize the sensitivity and the limit-of-detection of electrochemical sensors in complex biofluids to enable an in vivo monitoring of dopamine and other redox-active molecules.

While clozapine (CLZ) is the most effective antipsychotic drug for schizophrenia treatment, it remains underused. In order to understand the barriers of frequent blood draws for white blood cell counts (WBCs) and clozapine levels, we developed a psychiatrist survey and began an integrative approach of designing a point-of-care device that could eventually have real-time monitoring with immediate results.We ascertained barriers related to CLZ management and the acceptance of possible solutions by sending an anonymous survey to physicians in psychiatric practice (n=860). In parallel, we tested CLZ sensing using a prototype point-of-care monitoring device.255 responses were included in the survey results. The two barriers receiving mean scores with the highest agreement as being a significant barrier were patient nonadherence to blood work and blood work's burden on the patient (out of 28). Among nine solutions, the ability to obtain lab results in the physician's office or pharmacy was top ranked (mean±sd Likert scale [4.0±1.0]). Physicians responded that a point-of-care device to measure blood levels and WBCs would improve care and increase CLZ use. Residents ranked point-of-care devices higher than older physicians (4.07±0.87 vs. 3.47±1.08, p0.0001). Also, the prototype device was able to detect CLZ reliably in 1.6, 8.2, and 16.3 μg/mL buffered solutions.Survey results demonstrate physicians' desire for point-of-care monitoring technology, particularly among younger prescribers. Prototype sensor results identify that CLZ can be detected and integrated for future device development. Future development will also include integration of WBCs for a complete detection device.

We investigate gold, TiN, and platinum in combination with a chitosan–catechol-based redox-cycling system (RCS) for electrochemical detection of the antipsychotic clozapine. We have previously demonstrated the RCS for detection of clozapine in serum, but challenges remain regarding low signal-to-noise ratios. This can be mitigated by selection of electrode materials with beneficial surface morphologies and/or compositions. We employ cyclic voltammetry to assess the redox current generated by clozapine, and differentiate solely surface-area-based effects from clozapine-specific ones using a standard redox couple. We find that nano- and microstructured platinum greatly amplifies the clozapine signal compared to gold (up to 1490-fold for platinum black). However, the material performs poorly in the presence of chloride ions, and RCS modification provides no further amplification. The RCS combined with atomic-layer-deposited (ALD) TiN, on the other hand, increases the signal by 7.54 times, versus 2.86 times for RCS on gold, with a 9.2-fold lower variability, indicating that the homogenous and chemically inert properties of ALD-TiN may make it an ideal electrode material. Keywords: Therapeutic drug monitoring, Clozapine, Redox cycling, Titanium nitride, Platinum black

Antipsychotic clozapine is the most effective medication currently available for schizophrenia. However, clozapine is dramatically underutilized due to its harsh side effects that are not effectively monitored. By continuously monitoring clozapine blood levels, such as use of an implantable glucometer, which has transformed diabetes management, the treatment can be optimized and side effects will be minimized. Currently, none of the methods for clozapine detection show the ability to repeatedly measure clozapine in whole blood without pretreatment steps. Here we propose using a microelectrode modified with reduced graphene oxide—a material that was used for repeatable measurements in implantable electrochemical devices. We present the successful direct electrodeposition of reduced-graphene oxide coating onto microelectrodes. Systematic characterization of the electrodeposition technique parameters (i.e., the technique scan rate and the number of cycles) revealed their effect on the electrochemical activity and the structural properties (the film thickness and roughness) of the films. The developed reduced–graphene oxide-modified microelectrode exhibited the feasibility to detect clozapine in microliters–volume-samples of whole blood with a limit-of-detection and a sensitivity of 0.64 ± 0.04 μM and 19.6 ± 1.3 μA/cm2μM, respectively. Moreover, the reduced graphene oxide-modified microelectrodes exhibited high repeatability (retaining 94.6% of the electrochemical signal after 10 repeats), reproducibility (3.6% relative standard deviation), and storage stability (retaining 89% of the electrochemical signal after 4 weeks). Finally, relative recovery studies of 0.5, 1, and 2 μM clozapine concentrations resulted in 108 ± 4.0%, 112 ± 3.5%, and 103 ± 2.2%, respectively. Future studies should investigate the microelectrode fouling mechanisms in whole blood and explore methods to overcome fouling.

This article is based upon COST Action CA16215 and supported by the ERDF , European-Union Project No.1.1.1.2/16/I/001., We demonstrate a low-cost standalone portable spectrophotometer for fast and reliable measurement execution. The data acquired can be both displayed via a dedicated smartphone application or a computer interface, allowing users either to gather and view data on the move or set up a continuous experiment. All design and software files are open-source and are intended for the device to be easily replicable and further customizable to suit specific applications. The assembled device can measure absorption in the wavelength range from 450 nm to 750 nm with a resolution of 15 nm and is housed in a 90 × 85 × 58 mm casing. Validation of the device was carried out by assessing wavelength accuracy, dynamic range and the signal-to-noise ratio of the system, followed by testing in three different applications where limit of quantification, limit of detection and relative standard deviations were determined. The results indicated better performance than low-cost spectrophotometers, on average being comparable to moderate to high-cost spectrophotometers., European Regional Development Fund 1.1.1.2/16/I/001; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART², https://www.sciencedirect.com/science/article/pii/S246806722030016X

A three-dimensional micro-supercapacitor has been developed using a novel bottom-up assembly method combining genetically modified Tobacco mosaic virus (TMV-1Cys), photolithographically defined micropillars and selective deposition of ruthenium oxide on multi-metallic microelectrodes. The three-dimensional microelectrodes consist of a titanium nitride current collector with two functionalized areas: (1) gold coating on the active electrode area promotes TMV-1Cys adhesion, and (2) sacrificial nickel pads dissolve in ruthenium tetroxide plating solution to produce ruthenium oxide on all electrically connected areas. The microfabricated electrodes are arranged in an interdigitated pattern, and the capacitance per electrode has been measured as high as 203 mF cm −2 with solid Nafion electrolyte. The process integration of bio-templated ruthenium oxide with microfabricated electrodes and solid electrolyte is an important advance towards the energy storage needs of mass produced self-sufficient micro-devices.

Clozapine is the most effective antipsychotic medication for schizophrenia, but it is underutilized because of the inability to effectively monitor its treatment efficacy and side effects. In this work, we demonstrate the first analytical micro-system for real-time monitoring of clozapine serum levels. An electrochemical lab-on-a-chip is developed and integrated with a catechol-chitosan redox cycling system. The microfabricated device incorporates 4 electrochemical reaction chambers with the capability of analyzing microliter-volume samples. Integration of the catechol-chitosan film amplifies the clozapine oxidative signal and improves the signal-to-noise ratio, which addresses sensitivity and selectivity challenges. Optimization of the redox cycling system fabrication parameters and analysis of various electrochemical techniques and data processing approaches is implemented to maximize clozapine detection performance. The device is tested with buffer samples containing clozapine and demonstrates a sensitivity of 54 μC mL cm−2 μg−1 and a limit-of-detection of 0.8 μg mL−1, a sensing performance similar to a counterpart macro-scale benchtop system. Importantly, the feasibility to differentiate between 0.33 μg mL−1 and 3.27 μg mL−1 clozapine concentrations in human serum without any preceding dilution or filtering procedures is demonstrated, a significant step towards utilizing point-of-care testing micro-systems for schizophrenia treatment management. With these micro-systems, we envision more effective and safe treatment that will enable fewer visits to the clinicians, decrease costs and patient burden.

Mental health disorders are complex and poorly understood but would benefit from real-time chemical analysis capable of assessing a patient's current status, personalizing a therapeutic action, and monitoring compliance. Here, an electrochemical sensor is reported for detecting the antipsychotic drug clozapine which is one of the most effective but under-utilized drugs for managing schizophrenia. This sensor employs a composite film of multiwalled carbon nanotubes (CNTs) embedded within a matrix of the aminopolysaccharide chitosan. Chitosan allows programmable assembly of the composite film at an electrode address while the CNTs confer electrocatalytic activities that displace interfering serum peaks from the voltage region where clozapine oxidation occurs. Using differential pulse voltammetry, high sensitivities (limit of detection 0.05 × 10–6m) are demonstrated for clozapine analysis in buffer. In serum, clozapine sensitivity is reduced by an order of magnitude but still sufficient for clinical analysis. Finally, the detection of clozapine from the serum of a schizophrenia patient is demonstrated without the need for serum pretreatment. In the long term, it is envisioned that the CNT-chitosan coated electrode could be integrated within a small array of other sensor types to enhance information-extraction to allow mental health disorders to be better managed and better understood.

Lab-on-a-chip (LOC) devices for electrochemical analysis of DNA hybridization events offer a technology for real-time and label-free assessment of biomarkers at the point-of-care. Here, we present a microfluidic LOC, with 3×3 arrayed electrochemical sensors for the analysis of DNA hybridization events. A new dual layer microfluidic valved manipulation system is integrated providing controlled and automated capabilities for high throughput analysis. This feature improves the repeatability, accuracy, and overall sensing performance ( Fig. 1 ). The electrochemical activity of the fabricated microfluidic device is validated and demonstrated repeatable and reversible Nernstian characteristics. System design required detailed analysis of energy storage and dissipation as our sensing modeling involves diffusion-related electrochemical impedance spectroscopy. The effect of DNA hybridization on the calculated charge transfer resistance and the diffusional resistance components is evaluated. We demonstrate a specific device with an average cross-reactivity value of 27.5%. The device yields semilogarithmic dose response and enables a theoretical detection limit of 1 nM of complementary ssDNA target. This limit is lower than our previously reported non-valved device by 74% due to on-chip valve integration providing controlled and accurate assay capabilities.

Clozapine (CLZ), a dibenzodiazepine, is demonstrated as the optimal antipsychotic for patients suffering from treatment-resistant schizophrenia. Like many other drugs, understanding the concentration of CLZ in a patient’s blood is critical for managing the patients’ symptoms, side effects, and overall treatment efficacy. To that end, various electrochemical techniques have been adapted due to their capabilities in concentration-dependent sensing. An open question associated with electrochemical CLZ monitoring is whether drug–protein complexes (i.e., CLZ bound to native blood proteins, such as serum albumin (SA) or alpha-1 acid-glycoprotein (AAG)) contribute to electrochemical redox signals. Here, we investigate CLZ-sensing performance using fundamental electrochemical methods with respect to the impact of protein binding. Specifically, we test the activity of bound and free fractions of a mixture of CLZ and either bovine SA or human AAG. Results suggest that bound complexes do not significantly contribute to the electrochemical signal for mixtures of CLZ with AAG or SA. Moreover, the fraction of CLZ bound to protein is relatively constant at 31% (AAG) and 73% (SA) in isolation with varying concentrations of CLZ. Thus, electrochemical sensing can enable direct monitoring of only the unbound CLZ, previously only accessible via equilibrium dialysis. The methods utilized in this work offer potential as a blueprint in developing electrochemical sensors for application to other redox-active medications with high protein binding more generally. This demonstrates that electrochemical sensing can be a new tool in accessing information not easily available previously, useful toward optimizing treatment regimens.

A microfluidic electrochemical lab-on-a-chip (LOC) device for DNA hybridization detection has been developed. The device comprises a 3 × 3 array of microelectrodes integrated with a dual layer microfluidic valved manipulation system that provides controlled and automated capabilities for high throughput analysis of microliter volume samples. The surface of the microelectrodes is functionalized with single-stranded DNA (ssDNA) probes which enable specific detection of complementary ssDNA targets. These targets are detected by a capacitive technique which measures dielectric variation at the microelectrode-electrolyte interface due to DNA hybridization events. A quantitative analysis of the hybridization events is carried out based on a sensing modeling that includes detailed analysis of energy storage and dissipation components. By calculating these components during hybridization events the device is able to demonstrate specific and dose response sensing characteristics. The developed microfluidic LOC for DNA hybridization detection offers a technology for real-time and label-free assessment of genetic markers outside of laboratory settings, such as at the point-of-care or in-field environmental monitoring.

A microfluidic electrochemical lab-on-a-chip (LOC) device for DNA hybridization detection has been developed. The device comprises a 3 × 3 array of microelectrodes integrated with a dual layer microfluidic valved manipulation system that provides controlled and automated capabilities for high throughput analysis of microliter volume samples. The surface of the microelectrodes is functionalized with single-stranded DNA (ssDNA) probes which enable specific detection of complementary ssDNA targets. These targets are detected by a capacitive technique which measures dielectric variation at the microelectrode-electrolyte interface due to DNA hybridization events. A quantitative analysis of the hybridization events is carried out based on a sensing modeling that includes detailed analysis of energy storage and dissipation components. By calculating these components during hybridization events the device is able to demonstrate specific and dose response sensing characteristics. The developed microfluidic LOC for DNA hybridization detection offers a technology for real-time and label-free assessment of genetic markers outside of laboratory settings, such as at the point-of-care or in-field environmental monitoring.

Individually, advances in microelectronics and biology transformed the way we live our lives. However, there remain few examples in which biology and electronics have been interfaced to create synergistic capabilities. We believe there are two major challenges to the integration of biological components into microelectronic systems: (i) assembly of the biological components at an electrode address, and (ii) communication between the assembled biological components and the underlying electrode. Chitosan possesses a unique combination of properties to meet these challenges and serve as an effective bio-device interface material. For assembly, chitosan’s pH-responsive film-forming properties allow it to “recognize” electrode-imposed signals and respond by self-assembling as a stable hydrogel film through a cathodic electrodeposition mechanism. A separate anodic electrodeposition mechanism was recently reported and this also allows chitosan hydrogel films to be assembled at an electrode address. Protein-based biofunctionality can be conferred to electrodeposited films through a variety of physical, chemical and biological methods. For communication, we are investigating redox-active catechol-modified chitosan films as an interface to bridge redox-based communication between biology and an electrode. Despite significant progress over the last decade, many questions still remain which warrants even deeper study of chitosan’s structure, properties, and functions.

This work presents a thorough electrochemical and reliability analysis of a sensing scheme for the antipsychotic clozapine. We have previously demonstrated a novel detection approach for this redox-active drug, highly effective in schizophrenia treatment, based on a catechol-modified chitosan film. The biomaterial film enables amplification of the oxidative current generated by clozapine through redox cycling. Here, we study critical electrochemical and material aspects of the redox cycling system to overcome barriers in point-of-care monitoring in complex biological samples. Specifically, we explore the electrochemical parameter space, showing that enhanced sensing performance depends on the presence of a reducing mediator as well as the electrochemical technique applied. These factors account for up to 1.75-fold and 2.47-fold signal enhancement, respectively. Looking at potential interferents, we illustrate that the redox cycling system allows for differentiation between selected redox-active species, clozapine's structurally largely analogous metabolite norclozapine as well as the representative catecholamine dopamine. Furthermore, we investigate material stability and fouling with reuse as well as storage. We find no evidence of film fouling due to clozapine; slow overall biomaterial degradation with successive use accounts for a 2.2% absolute signal loss and can be controlled for. Storage of the redox cycling system appears feasible over weeks when kept in solution with only 0.26%/day clozapine signal degradation, while ambient air exposure of three or more days reduces performance by 58%. This study not only advances our understanding of the catechol-modified chitosan system, but also further establishes the viability of applying it toward sensing clozapine in a clinical setting. Such point-of-care monitoring will allow for broader use of clozapine by increasing convenience to patients as well as medical professionals, thus improving the lives of people affected by schizophrenia through personalized medicine.

Microelectronic devices that contain biological components are typically used to interrogate biology rather than control biological function. Patterned assemblies of proteins and cells have, however, been used for in vitro metabolic engineering, where coordinated biochemical pathways allow cell metabolism to be characterized and potentially controlled on a chip. Such devices form part of technologies that attempt to recreate animal and human physiological functions on a chip and could be used to revolutionize drug development. These ambitious goals will, however, require new biofabrication methodologies that help connect microelectronics and biological systems and yield new approaches to device assembly and communication. Here, we report the electrically mediated assembly, interrogation and control of a multi-domain fusion protein that produces a bacterial signalling molecule. The biological system can be electrically tuned using a natural redox molecule, and its biochemical response is shown to provide the signalling cues to drive bacterial population behaviour. We show that the biochemical output of the system correlates with the electrical input charge, which suggests that electrical inputs could be used to control complex on-chip biological processes.

a b s t r a c t Schizophrenia is a lifelong mental disorder with few recent advances in treatment. Clozapine is the most effective antipsychotic for schizophrenia treatment. However, it remains underutilized since frequent blood draws are required to monitor adverse side effects, and maintain clozapine concentrations in a therapeutic range. Micro-system technology utilized towards real-time monitoring of efficacy and safety will enable personalized medicine and better use of this medication. Although work has been reported on clozapine detection using its electrochemical oxidation, no in situ monitoring of clozapine has been described. In this work, we present a new concept for clozapine in situ sensing based on amplifying its oxidation current. Specifically, we use a biofabricated catechol-modified chitosan redox cycling system to provide a significant amplification of the generated oxidizing current of clozapine through a continuous cycle of clozapine reduction followed by re-oxidation. The amplified signal has improved the signal-to- noise ratio and provided the required limit-of-detection and dynamic range for clinical applications with minimal pre-treatment procedures. The sensor reports on the functionality and sensitivity of clozapine detection between 0.1 and 10 g/mL. The signal generated by clozapine using the catechol-modified chitosan amplifier has shown to be 3 times greater than the unmodified system. The sensor has the ability to differentiate between clozapine and its metabolite norclozapine, as well as the feasibility to detect clozapine in human serum in situ within the required dynamic range for clinically related applications. This new biosensing approach can be further developed towards its integration in miniaturized devices for improved personalized mental health care.

The antipsychotic clozapine is the most effective medication available for schizophrenia and it is the only antipsychotic with a known efficacious clinical range. However, it is dramatically underutilized due to the inability to test clozapine blood levels in finger-pricked patients' samples. This prevents obtaining immediate blood levels information, resulting in suboptimal treatment. The development of an electrochemical microsensor is presented, which enables, for the first time, clozapine detection in microliters volume whole blood. The sensor is based on a microelectrode modified with micrometer-thick biopolymer chitosan encapsulating carbon nanotubes. The developed sensor detects clozapine oxidation current, in the presence of other electroactive species in the blood, which generate overlapping electrochemical signals. Clozapine detection, characterized in whole blood from healthy volunteers, displays a sensitivity of 32 ± 3.0 µA cm-2 µmol-1 L and a limit-of-detection of 0.5 ± 0.03 µmol L-1 . Finally, the developed sensor displays a reproducible electrochemical signal (0.6% relative standard deviation) and high storage stability (9.8% relative standard deviation after 8 days) in serum samples and high repeatability (9% relative standard deviation for the 5th repetition) in whole blood samples. By enabling the rapid and minimally invasive clozapine detection at the point-of-care, an optimal schizophrenia treatment is provided.

The response modeling of whole-cell biochip represents the link between cellular biology and transducer output, allowing better system engineering. It provides the mathematical background for signal and noise modeling, performance prediction and data analysis. Here we describe an analytical model for whole-cell biosensors with electrochemical detection for single use, test and dispose applications. In this system the electrochemical signal is generated by the oxidation of the by-products of the reaction between an external substrate and the enzyme alkaline phosphatase. The enzyme expression can be either normal or enhanced due to the response of the biological cell to an external excitation. The electrochemical oxidation current is measured as a function of time. The model is based on the electrochemical reaction rate equations; an analytical solution is presented, compared to data and discussed.

We present the first in-depth system integration study of in-plane hydrodynamic focusing in a microfluidic impedance cytometry lab-on-a-chip. The method relies on constricting the detection volume with non-conductive sheath flows and characterizing particles or cells based on changes in impedance. This approach represents an avenue of overcoming current limitations in sensitivity with translating cytometers to the point of care for rapid, low-cost blood analysis. While examples of integrated devices are present in the literature, no systematic study of the interplay between hydrodynamics and electrodynamics has been carried out as of yet. We develop analytical and numerical models to describe the impedimetric response of the sensor as a function of cellular characteristics, physical flow properties, and device geometry. We fabricate a working prototype lab-on-a-chip for experimental validation using latex particles. We find that ionic diffusion can be a critical limiting factor even at high Peclet number. Moreover, we explore geometric variations, revealing that the ionic diffusion-related distance between the center of the hydrodynamic focusing junction and the impedance measurement electrodes plays a dominant role. With our device, we demonstrate over fivefold enhancement in impedance signals and population separation with in-plane hydrodynamic focusing. It is only through such in-depth system studies, in both models and experiments, that optimal utilization of microsystem capabilities becomes possible.

The Information Age transformed our lives but it has had surprisingly little impact on the way chemical information (e.g., from our biological world) is acquired, analyzed and communicated. Sensor systems are poised to change this situation by providing rapid access to chemical information. This access will be enabled by technological advances from various fields: biology enables the synthesis, design and discovery of molecular recognition elements as well as the generation of cell-based signal processors; physics and chemistry are providing nano-components that facilitate the transmission and transduction of signals rich with chemical information; microfabrication is yielding sensors capable of receiving these signals through various modalities; and signal processing analysis enhances the extraction of chemical information. The authors contend that integral to the development of functional sensor systems will be materials that (i) enable the integrative and hierarchical assembly of various sensing components (for chemical recognition and signal transduction) and (ii) facilitate meaningful communication across modalities. It is suggested that stimuli-responsive self-assembling biopolymers can perform such integrative functions, and redox provides modality-spanning communication capabilities. Recent progress toward the development of electrochemical sensors to manage schizophrenia is used to illustrate the opportunities and challenges for enlisting sensors for chemical information processing.

The electrode geometry and material have a significant effect on the electrochemical biochip transduction of chemical signals into electrical current or voltage. In this work we focus on the working electrode aiming to improve the signal level of live cell sensors integrated on solid-state microchips. We present here a model and measurements describing the effect of the electrode material and dimensions on the biochip performance. The research hypothesis was that the electrode transduction efficiency increases as its effective area increases. Therefore, we investigated two methods to increase the electrode effective area: 3D structures and a polymer modified electrode. An electrochemical microchip was fabricated with a working electrode that was further modified, resulting in two structure types: 3D metallic pillar-based and polypyrrole-coated. The electrochemical performance of both modified electrodes was characterized and their utilization as working electrodes in whole-cell biochips for toxicity sensing was studied. Bio-detection efficiency analysis demonstrated higher biosensing performance for the metallic (e.g. Cu/Au) pillar-based microchip than for the polypyrrole-modified and the non-modified microchips. Therefore, we conclude that the enhanced signal of the modified geometry electrode is most probably due to the increased effective surface area and the improved charge transfer efficiency.

DNA hybridization detection in microfluidic devices can reduce sample volumes, processing times, and can be integrated with other measurements. However, as device footprints decrease and their complexity increase, the signal-to-noise ratio in these systems also decreases and the sensitivity is thereby compromised. Device miniaturization produces distinct properties and phenomena with greater influence at the micro-scale than at the macro-scale. Here, a diffusion-restriction model was applied to a miniaturized biochip nanovolume reactor to accurately characterize DNA hybridization events that contribute to shifts in both charge transfer resistance and diffusional resistance. These effects are shown to play a significant role in electrochemical impedance spectroscopy (EIS) analyses at these length scales. Our highly functional microfluidic biosensor enables the detection of ssDNA targets selectively, with a calculated detection limit of 3.8 nM, and cross-reactivity of 13% following 20 min incubation with the target. This new biosensing approach can be further modeled and tested elucidating diffusion behavior in miniaturized devices and improving the performance of biosensors.

Integrated polypyrrole, a conductive polymer, interconnects on polymeric substrates were microfabricated for flexible sensors and actuators applications. It allows manufacturing of moving polymeric microcomponents suitable, for example, for micro-optical-electromechanical (MOEMS) systems or implanted sensors. This generic technology allows producing “all polymer” components where the polymers serve as both the structural and the actuating materials. In this paper we present two possible novel architectures that integrate polypyrrole conductors with other structural polymers: (a) polypyrrole embedded into flexible polydimethylsiloxane (PDMS) matrix forming high aspect ratio electrodes and (b) polypyrrole deposited on planar structures. Self-aligned polypyrrole electropolymerization was developed and demonstrated for conducting polymer lines on either gold or copper seed layers. The electropolymerization process, using cyclic voltammetry from an electrolyte containing the monomer, is described, as well as the devices’ characteristics. Finally, we discuss the effect of integrating conducting polymers with metal seed layer, thus enhancing the device durability and reliability.

In this article the research for developing whole-cell biochips has been presented using both bioluminescent and electrochemical methods. The research was on integrating an electrode cell with both electrochemical and bioluminescent detection using a single VLSI chip. The authors have investigated the signal conditioning system that can work with any kind of amperometric and bioluminescent sensor. During this research the authors focused on the analog front-end unit. The work includes investigating the electronic model for simulation for an electrochemical cell and conceiving a fully integrated 8X8 electrochemical sensor array. The authors are focusing on signal conditioning system and its functionality. The main concern for the authors was to maintain the complexity and the number of electronic devices as low as possible.