Light-addressable Potentiometric Sensor System Research Articles

A light-addressable potentiometric sensor-based extracellular calcium dynamic monitoring and imaging platform for cellular calcium channel drug evaluation

Disruption and dysregulation of cellular calcium channel function can lead to diseases such as ischemic stroke, heart failure, and arrhythmias. Corresponding calcium channel drugs typically require preliminary efficacy evaluations using in vitro models such as cells and simulated tissues before clinical testing. However, traditional detection and evaluation methods often encounter challenges in long-term continuous monitoring and lack calcium specificity. In this study, a dynamic monitoring system based on ion-sensitive membranes for light-addressable potentiometric sensor (LAPS) was developed to meet the demand for monitoring changes in extracellular calcium ion (Ca2+) concentration in live cells. The effects of Ca2+ channel agonists and blockers on 2D and 3D HL-1 cells were investigated, with changes in extracellular Ca2+ concentration reflecting cellular calcium metabolism, facilitating drug evaluation. Additionally, calcium imaging technology with optical addressing capability complemented the LAPS system's ability to perceive 3D cell morphology, enhancing its drug evaluation capabilities. This work provides a novel, label-free, specific, and stable technique for monitoring cellular calcium metabolism. It achieves both continuous monitoring at single points and custom sensing area calcium imaging, holding significant implications for drug screening and disease treatment related to human calcium homeostasis.

Rapid and specific detection of LDL based on light addressable potentiometric sensor decorated with reduced graphene oxide-polyaniline-hemin nanocomposites

Atherosclerotic Cardiovascular Disease (ASCVD) is one of the major fatal diseases for humans and the fatality rate is increasing rapidly. Low density lipoprotein (LDL) is a serum key marker in the diagnosis of ASCVD because LDL level is associated with the prevalence of ASCVD. Herein, a light addressable potentiometric sensor (LAPS) was constructed for rapid detection of LDL using reduced graphene oxide-polyaniline-hemin nanocomposites (RGO-PANI-HNCs) and low density lipoprotein aptamer (LDLapt) as sensitive membrane of LAPS. Under the effect of bias voltage, the specific binding between LDL and LDLapt, and forming the LDL-LDLapt complex will cause the voltage change on the sensitive membrane surface of the LAPS system, which will cause the change of original current–voltage (I-V) balance in the circuit, resulting in the shift of I-V curve. The correlation between the potential shift of LAPS and LDL concentration was linear from 1.0 to 100.0 μg/mL under optimal conditions. The sensitivity is 4.7671 mV/μg/mL, and the detection limit is 0.79 μg/mL. Also, the LDL biosensor showed satisfactory specificity, selectivity, reproducibility, and showed a good precision in real human serum samples, which provides a simple and effective way for the early diagnosis of ASCVD.

A differential light addressable potentiometric sensor using solid-state reference

The differential light addressable potentiometric sensor (LAPS) can provide low-background measurement for chemicals. For the conventional differential LAPS system, the acquisition of reference signal requires liquid participation. In this study, a differential LAPS with solid-state reference (SSR) is presented for pH measurement, where SSR based on the structure of metal-insulator-semiconductor is used as reusable reference signal source. In order to facilitate the differential signal matching and realize the effect of large reduction of background signal, an intelligent method to match the amplitude and phase between LAPS output and SSR output by controlling the illumination excitation of SSR is proposed. Effect of SSR as reference signal source for differential LAPS is studied, which is including pH sensing and chemical image performance. As an auxiliary liquid-free chip, SSR can assist the differential LAPS to realize low-background pH measurement conveniently and flexibly.

Label-free detection of glypican-3 using reduced graphene oxide /polyetherimide/gold nanoparticles enhanced aptamer specific sensing interface on light-addressable potentiometric sensor

Glypican-3 (GPC3) protein is considered as an effective and specific biomarker for the accurate diagnosis of hepatocellular carcinoma (HCC), and there is a critical demand to construct strategies with shorter time, lower cost noise and higher sensitivity. In this study, a biosensor for label-free detection of GPC3 was prepared by modifying GPC3 aptamer (GPC3Apt) on the surface of Si-based light addressable potentiometric sensor (LAPS) chip modified by reduced graphene oxide/polyetherimide/gold nanoparticles (rGO/PEI/AuNPs). Among them, GPC3Apt with a low equilibrium dissociation constant was used as a biorecognition molecule to recognize and capture GPC3. The rGO/PEI/AuNPs decorated on the LAPS surface could enlarge the surface area for GPC3Apt immobilization and provide more active sites for GPC3Apt to bind effectively with the target GPC3. When a bias voltage was provided to the LAPS system, the forming GPC3-GPC3Apt complexs on the sensing interface of LAPS would cause the potential of the sensitive membrane surface to change and generate a corresponding offset response in photocurrent-voltage (I-V) curves. The potential shift and GPC3 concentration showed a good linear range from 0.1 to 100.0 μg/mL with a detection limit of 40.0 ng/mL (S/N = 3) and a sensitivity of 1.33638 mV/μg/mL. In addition, the LAPS detection system also has good specificity and stability, which can be used for the detection of GPC3 in spiked serum samples.

1,5-anhydroglucitol biosensor based on light-addressable potentiometric sensor with RGO-CS-Fc/Au NPs nanohybrids

In this paper, a novel silicon-based light-addressable potentiometric sensor (LAPS) has been designed for the detection of 1,5-anhydroglucitol (1,5-AG) in human serum. Reduced graphene oxide-chitosan-ferrocene (RGO-CS-Fc)/AuNPs nanohybrids and pyranose oxidase (PROD) enzyme is used to fabricate biological sensitive membrane unit by layer-by-layer assembly technology. When a bias voltage is provided to the LAPS system, the catalytic oxidation reaction between 1,5-AG and PROD to produce H2O2. The by-product H2O2 can oxidize Fc(Fe2+) ions in RGO-CS-Fc nanohybrids into Fc(Fe3+) ions, which cause the potential of the sensitive membrane surface to change and the potential shift of I-V curve will generate a corresponding offset response. Under the optimal conditions, the potential shift of the LAPS is linearly related to the concentration of 1,5-AG at 10 µg·mL−1 –350 µg·mL−1 with the correlation coefficient of 0.97414. The sensitivity is 0.44273 mV/µg·mL−1 and the lowest detection limit is 10 µg·mL−1. In addition, the biosensor showed good specificity, acceptable stability and satisfactory recovery rates (91.28%-107.66%), which would be a potential testing methods in actual clinical samples.

Silicone-Rubber Based Multiplex Ion-Sensitive Light-Addressable Potentiometric Sensor (ISLAPS) System for Physiological Ions Detection

Silicone-Rubber Based Multiplex Ion-Sensitive Light-Addressable Potentiometric Sensor (ISLAPS) System for Physiological Ions Detection

A novel aptasensor based on light-addressable potentiometric sensor for the determination of Alpha-fetoprotein

In this work, a novel and simple aptasensor based on the light-addressable potentiometric sensor (LAPS) for Alpha-fetoprotein (AFP) detection was proposed. Due to the light addressable capability and potentiometric stability of LAPS, the concentration of AFP can be determined by monitoring the potential shifts of LAPS, which was caused by specific reaction between AFP-aptamer and AFP. The AFP-aptamer and gold nanoparticles (Au NPs) were modified on the surface of LAPS chip to fabricate the biological sensing element of LAPS system. The AFP-aptamer was used as molecules probe to recognize and capture AFP. Au NPs deposited on the LAPS surface could enlarge the surface area for the AFP-aptamer immobilization and provide more sites for AFP-aptamer to bind effectively with the target AFP and form more aptamer-antigen complex. Under optimal conditions, the potential shifts of the LAPS detection system were proportional to the AFP concentration in a wide linear range from 0.1–100 μg/mL. The regression equation is Y = 2.5892X+103.42778 (Y was the potential shift and X indicated the concentration of AFP) with a correlation coefficient of 0.9959 and a detection limit of 92.0 ng/mL at a signal-to-noise ratio of 3. The proposed method exhibited a good analytical performance and provided a promising potential application for aptasensor combined with LAPS in immunoassays.

LAPS-based monitoring of metabolic responses of bacterial cultures in a paper fermentation broth

As an alternative renewable energy source, methane production in biogas plants is gaining more and more attention. Biomass in a bioreactor contains different types of microorganisms, which should be considered in terms of process-stability control. Metabolically inactive microorganisms within the fermentation process can lead to undesirable, time-consuming and cost-intensive interventions. Hence, monitoring of the cellular metabolism of bacterial populations in a fermentation broth is crucial to improve the biogas production, operation efficiency, and sustainability. In this work, the extracellular acidification of bacteria in a paper-fermentation broth is monitored after glucose uptake, utilizing a differential light-addressable potentiometric sensor (LAPS) system. The LAPS system is loaded with three different model microorganisms (Escherichia coli, Corynebacterium glutamicum, and Lactobacillus brevis) and the effect of the fermentation broth at different process stages on the metabolism of these bacteria is studied. In this way, different signal patterns related to the metabolic response of microorganisms can be identified. By means of calibration curves after glucose uptake, the overall extracellular acidification of bacterial populations within the fermentation process can be evaluated.

Recent Developments of High-Resolution Chemical Imaging Systems Based on Light-Addressable Potentiometric Sensors (LAPSs).

A light-addressable potentiometric sensor (LAPS) is a semiconductor electrochemical sensor based on the field-effect which detects the variation of the Nernst potential on the sensor surface, and the measurement area is defined by illumination. Thanks to its light-addressability feature, an LAPS-based chemical imaging sensor system can be developed, which can visualize the two-dimensional distribution of chemical species on the sensor surface. This sensor system has been used for the analysis of reactions and diffusions in various biochemical samples. In this review, the LAPS system set-up, including the sensor construction, sensing and substrate materials, modulated light and various measurement modes of the sensor systems are described. The recently developed technologies and the affecting factors, especially regarding the spatial resolution and temporal resolution are discussed and summarized, and the advantages and limitations of these technologies are illustrated. Finally, the further applications of LAPS-based chemical imaging sensors are discussed, where the combination with microfluidic devices is promising.

Quantitative differential monitoring of the metabolic activity of Corynebacterium glutamicum cultures utilizing a light-addressable potentiometric sensor system

Applying biosensors for evaluation of the extracellular acidification of microorganisms in various biotechnological fermentation processes is on demand. An early stage detection of disturbances in the production line would avoid costly interventions related to metabolically inactive microorganisms. Furthermore, the determination of the number of living cells through cell plating procedure after cultivations is known as time- and material-consuming. In this work, a differential light-addressable potentiometric sensor (LAPS) system was developed to monitor the metabolic activity of Corynebacterium glutamicum (C. glutamicum ATCC13032) as typical microorganism in fermentation processes. In this context, the number of living cells in suspensions was directly determined utilizing the read-out principle of the LAPS system. The planar sensor surface of the LAPS design allows to fixate 3D-printed multi-chamber structures, which enables differential measurements. In this way, undesirable external influences such as pH variations of the medium and sensor signal drift can be compensated.

Determination of the extracellular acidification of Escherichia coli K12 with a multi‐chamber‐based LAPS system

On‐line monitoring of the metabolic activity of microorganisms involved in intermediate stages of biogas production plays an important role to avoid undesirable “down times” during the biogas production. In order to control this process, an on‐chip differential measuring system based on the light‐addressable potentiometric sensor (LAPS) principle combined with a 3D‐printed multi‐chamber structure has been realized. As a test microorganism, Escherichia coli K12 (E. coli K12) were used for cell‐based measurements. Multi‐chamber structures were developed to determine the metabolic activity of E. coli K12 in suspension for a different number of cells, responding to the addition of a constant or variable amount of glucose concentrations, enabling differential and simultaneous measurements.Multi‐chamber differential measurement setup based on the LAPS principle; RE, reference electrode.

Highly sensitive covalently functionalized light-addressable potentiometric sensor for determination of biomarker

A biomarker is related to the biological status of a living organism and shows great promise for the early prediction of a related disease. Herein we presented a novel structured light-addressable potentiometric sensor (LAPS) for the determination of a model biomarker, human immunoglobulin G (hIgG). In this system, the goat anti-human immunoglobulin G antibody was used as recognition element and covalently immobilized on the surface of light-addressable potentiometric sensor chip to capture human immunoglobulin G. Due to the light addressable capability of light-addressable potentiometric sensor, human immunoglobulin G dissolved in the supporting electrolyte solution can be detected by monitoring the potential shifts of the sensor. In order to produce a stable photocurrent, the laser diode controlled by field-programmable gate array was used as the light emitter to drive the light-addressable potentiometric sensor. A linear correlation between the potential shift response and the concentration of human immunoglobulin G was achieved and the corresponding regression equation was ΔV (V)=0.00714ChIgG (μg/mL)–0.0147 with a correlation coefficient of 0.9968 over a range 0–150μg/mL. Moreover, the light-addressable potentiometric sensor system also showed acceptable stability and reproducibility. All the results demonstrated that the system was more applicable to detection of disease biomarkers with simple operation, multiple-sample format and might hold great promise in various environmental, food, and clinical applications.

Integrated multifunctional cell-based biosensor system for monitoring extracellular acidification and cellular growth

In order to achieve the recording of cellular multiple physiological parameters, a multifunctional biosensor system is developed with light-addressable potentiometric sensor (LAPS) unit, electrical cell–substrate impedance sensor (ECIS) unit and their instrument. Sensor basic performance and cell experiments were carried out to test the functions of multifunctional biosensor system. The results showed that LAPS and ECIS multifunction system can simultaneously detect extracellular acidification and cellular growth with basic performance. Based on the real-time, label-free, and non-invasive sensor technologies, the multifunctional biosensor system may provide a utility platform in the field of cellular physiology study and drug analysis in vitro.

A Novel Biosensor Based on LAPS for the Detection of IgG

Immunoglobulin G (IgG) is one of the most important factors in diagnosing some diseases in clinic. A novel biosensor for dectection of IgG based on light-addressable potentiometric sensor (LAPS) was presented in this paper. The LAPS measurement system included the LAPS sensor, light source, the electrode and the electrochemical workstation. The LAPS sensor was fabricated by the method of the Layer-by-Layer Self-Assembly (LBL-SA). The IgG antibody modified onto the silicon wafer of LAPS to capture the corresponding antigen by the specific immune response which has an effect on the sensitive of LAPS to change the photocurrent. The laser diode (LD) light source of 890 nm wavelength was chose as illuminant to drive the LAPS to create the photocurrent. A FPGA was introduced to control the LD and generate a sine wave signal with the special frequency. Different concentration of IgG arranged 50-150μg/mL was detected by the LAPS system. A calibration curve that represented linear correlation between the bias voltage values and theconcentration of IgG was illustrated, and the linear correlation coefficient was 0.9943. This new biosensor can be very useful for detection of IgG based on the LAPS principle.

Light-addressable potentiometric sensor based on precise light intensity modulation for eliminating measurement error caused by light source

To eliminate measurement error caused by fluctuation, distortion and noise of light source output in a light-addressable potentiometric sensor (LAPS) system, LAPS system based on precise light intensity modulation is presented in this study. A superluminescence LED (SLED) module, with a home-made multi negative feedback SLED driver, is proposed as the precise light source in this system. A high-speed optical fiber spectrometer is introduced for on-line monitoring and long period intensity compensation. The precise light source provides light output to LAPS, and keeps light intensity on sensitive surface to meet sine rules with low distortion and low noise. Furthermore, it is immune from variation of ambient temperature. Detailed optical parameters of precise light source are presented and compared with conventional light source. H+ measurements for LAPS system based on precise light intensity modulation were given and compared with system with conventional light source. From contrast experiments, it can be deduced that LAPS system based on precise light intensity modulation has better linearity, higher accuracy and lower noise than LAPS system with conventional light source.

A novel microphysiometer based on high sensitivity LAPS and microfluidic system for cellular metabolism study and rapid drug screening

This study presents a novel microphysiometer for studying the mechanism of cellular metabolism and drug effect. Based on the photocurrent amplification of light-addressable potentiometric sensor (LAPS), the constant voltage detection mode was introduced to enhance the detection sensitivity to replace the conventional constant current mode with the slow feedback rate. The photocurrent amplification of LAPS was improved by developing the sensor structure and fabrication processes. The sensor unit with microfluidic system was designed to detect the concentration change of cellular acidic metabolites in the extracellular microenvironment rapidly. Characteristic test experiments and cellular metabolism experiments were carried out to determine the performance of microphysiometer. The result showed that sensitivity of microphysiometer is significantly enhanced to sense the fluctuation of cellular metabolism rapidly and sensitively in real-time detection of living cells under physiological condition. With these improvements, the novel microphysiometer holds promise as a utility platform for studying cellular metabolism and evaluating drug effect.

Bio-initiated light addressable potentiometric sensor for unlabeled biodetection and its MEDICI simulation

A bio-mimetic anchoring strategy based on L-3,4-dihydroxyphenylalanine (L-DOPA) was exploited to activate the surface of light addressable potentiometric sensor (LAPS), with the structure of Si(3)N(4)/SiO(2)/Si. X-Ray photoelectron spectroscopy (XPS) measurements were carried out to ascertain its existence. The protein's immobilization on L-DOPA-initiated LAPS were also tested by our LAPS system. Then L-DOPA-activated LAPS were applied in the unlabeled rabbit anti-mouse immunoglobulin (IgG) detection. The maximum sensitivity of L-DOPA-activated LAPS to antigen (Ag) is about 5.68 nA/p[Ag]. LAPS responses in IgG measurements were from 95 to 180 nA, when the concentration was varied from 0-4 μg mL(-1). These experiments show that L-DOPA is an available material for LAPS surface modifications. At the same time, simulations based on MEDICI (Synopsys™) were performed. The simulated curves are in accordance with experimental data which demonstrate our theoretical analysis for the experimental phenomenon, and indicate the feasibility of simulating biological electronic devices with MEDICI.

In vitro assessing the risk of drug-induced cardiotoxicity by embryonic stem cell-based biosensor

Drug-induced prolongation of ventricular repolarization with arrhythmia is a major concern in clinic safety pharmacology, and has been a common reason for the withdrawal of several promising drugs from the market. Therefore, novel techniques should be developed to evaluate cardiotoxicity of new drugs in preclinical research. A cardiomyocyte based biosensor was developed using the light addressable potentiometric sensor (LAPS). Mouse embryonic stem cells cultured on the surface of LAPS were induced to differentiate into synchronized spontaneity beating cardiomyocytes. Changes of extracellular potentials and cell shapes with their mechanical beatings could induce modulation of photocurrents in the LAPS system, and finally change the output of the sensor. With the characteristics of light addressability, LAPS can record cell clusters at any desired position. The sensor can be used to record the prolongation of ventricular action potentials with the cardiotoxicity induced by drugs such as amiodarone, levofloxacin, sparfloxacin, and noradrenaline. The quick and on time characteristics of the sensor were promising to establish a high-throughput platform for pharmacological toxicity investigation.

Neurochip based on light-addressable potentiometric sensor with wavelet transform de-noising

Neurochip based on light-addressable potentiometric sensor (LAPS), whose sensing elements are excitable cells, can monitor electrophysiological properties of cultured neuron networks with cellular signals well analyzed. Here we report a kind of neurochip with rat pheochromocytoma (PC12) cells hybrid with LAPS and a method of de-noising signals based on wavelet transform. Cells were cultured on LAPS for several days to form networks, and we then used LAPS system to detect the extracellular potentials with signals de-noised according to decomposition in the time-frequency space. The signal was decomposed into various scales, and coefficients were processed based on the properties of each layer. At last, signal was reconstructed based on the new coefficients. The results show that after de-noising, baseline drift is removed and signal-to-noise ratio is increased. It suggests that the neurochip of PC12 cells coupled to LAPS is stable and suitable for long-term and non-invasive measurement of cell electrophysiological properties with wavelet transform, taking advantage of its time-frequency localization analysis to reduce noise.

Label-free biosensor: A novel phage-modified Light Addressable Potentiometric Sensor system for cancer cell monitoring

Early diagnosis has become the most important factor influencing the cancer's curing efficiency in clinical medicine. Here we present a new way for detection of cancer markers and cancer cells based on phage-modified Light Addressable Potentiometric Sensor (phage-LAPS). Phages were immobilized on the Si3N4 chip surfaces covalently. Using the back-illuminating system, this phage-LAPS is tested to detect human phosphatase of regenerating liver-3 (hPRL-3) in the concentrations of 0.04–400nM, and the mammary adenocarcinoma cell (MDAMB231) in the concentrations of 0–105mL. The maximum responding signal is about 10 and 60μV, respectively. The results demonstrated that the system was more applicable to detection of cancer cell than that of cancer biomarkers. This work might show potential application in clinic assays of cancer and the study of phage–cell interaction.