High-Throughput Microelectrode Arrays for Precise Functional Localization of the Globus Pallidus Internus.

The globus pallidus internus (GPi) was considered a common target for stimulation in Parkinson's disease (PD). Located deep in the brain and of small size, pinpointing it during surgery is challenging. Multi-channel microelectrode arrays (MEAs) can provide micrometer-level precision functional localization, which can maximize the surgical outcome. In this paper, a 64-channel MEA modified by platinum nanoparticles with a detection site impedance of 61.1 kΩ was designed and prepared, and multiple channels could be synchronized to cover the target brain region and its neighboring regions so that the GPi could be identified quickly and accurately. The results of the implant trajectory indicate that, compared to the control side, there is a reduction in local field potential (LFP) power in multiple subregions of the upper central thalamus on the PD-induced side, while the remaining brain regions exhibit an increasing trend. When the MEA tip was positioned at 8,700 µm deep in the brain, the various characterizations of the spike signals, combined with the electrophysiological characteristics of the ß-segmental oscillations in PD, enabled MEAs to localize the GPi at the single-cell level. More precise localization could be achieved by utilizing the distinct characteristics of the internal capsule (ic), the thalamic reticular nucleus (Rt), and the peduncular part of the lateral hypothalamus (PLH) brain regions, as well as the relative positions of these brain structures. The MEAs designed in this study provide a new detection method and tool for functional localization of PD targets and PD pathogenesis at the cellular level.

Design and Validation of a Short Novel Estradiol Aptamer and Exploration of Its Application in Sensor Technology.

The specific and sensitive detection of 17ß-estradiol (E2) is critical for diagnosing and treating numerous diseases, and aptamers have emerged as promising recognition probes for developing detection platforms. However, traditional long-sequence E2 aptamers have demonstrated limited clinical performance due to redundant structures that can affect their stability and recognition ability. There is thus an urgent need to further optimize the structure of the aptamer to build an effective detection platform for E2. In this work, we have designed a novel short aptamer that retains the key binding structure of traditional aptamers to E2 while eliminating the redundant structures. The proposed aptamer was evaluated for its binding properties using microscale thermophoresis, a gold nanoparticle-based colorimetric method, and electrochemical assays. Our results demonstrate that the proposed aptamer has excellent specific recognition ability for E2 and a high affinity with a dissociation constant of 92 nM. Moreover, the aptamer shows great potential as a recognition probe for constructing a highly specific and sensitive clinical estradiol detection platform. The aptamer-based electrochemical sensor enabled the detection of E2 with a linear range between 5 pg mL-1 and 10 ng mL-1 (R2 = 0.973), and the detection capability of a definite low concentration level was 5 pg mL-1 (S/N = 3). Overall, this novel aptamer holds great promise as a valuable tool for future studies on the role of E2 in various physiological and pathological processes and for developing sensitive and specific diagnostic assays for E2 detection in clinical applications.

Reduced Graphene Oxide and Gold Nanoparticles-Modified Electrochemical Aptasensor for Highly Sensitive Detection of Doxorubicin.

Doxorubicin (DOX) is the most clinically important antibiotic in cancer treatment, but its severe cardiotoxicity and other side effects limit its clinical use. Therefore, monitoring DOX concentrations during therapy is essential to improve efficacy and reduce adverse effects. Here, we fabricated a sensitive electrochemical aptasensor for DOX detection. The sensor used gold wire as the working electrode and was modified with reduced graphene oxide (rGO)/gold nanoparticles (AuNPs) to improve the sensitivity. An aptamer was used as the recognition element for the DOX. The 5' end of the aptamer was modified with a thiol group, and thus immobilized to the AuNPs, and the 3' end was modified with methylene blue, which acts as the electron mediator. The combination between the aptamer and DOX would produce a binding-induced conformation, which changes the electron transfer rate, yielding a current change that correlates with the concentration of DOX. The aptasensor exhibited good linearity in the DOX concentration range of 0.3 µM to 6 µM, with a detection limit of 0.1 µM. In addition, the aptasensor was used for DOX detection in real samples and results, and showed good recovery. The proposed electrochemical aptasensor will provide a sensitive, fast, simple, and reliable new platform for detecting DOX.

PPy/SWCNTs-Modified Microelectrode Array for Learning and Memory Model Construction through Electrical Stimulation and Detection of In Vitro Hippocampal Neuronal Network.

The learning and memory functions of the brain remain unclear, which are in urgent need for the detection of both a single cell signal with high spatiotemporal resolution and network activities with high throughput. Here, an in vitro microelectrode array (MEA) was fabricated and further modified with polypyrrole/carboxylated single-walled carbon nanotubes (PPy/SWCNTs) nanocomposites as the interface between biological and electronic systems. The deposition of the nanocomposites significantly improved the performance of microelectrodes including low impedance (60.3 ± 28.8 k Ω), small phase delay (-32.8 ± 4.4°), and good biocompatibility. Then the modified MEA was used to apply learning training and test on hippocampal neuronal network cultured for 21 days through electrical stimulation, and multichannel electrophysiological signals were recorded simultaneously. During the process of learning training, the stimulus/response ratio of the hippocampal learning population gradually increased and the response time gradually decreased. After training, the mean spikes in burst, number of bursts, and mean burst duration increased by 53%, 191%, and 52%, respectively, and the correlation of neurons in the network was significantly enhanced from 0.45 ± 0.002 to 0.78 ± 0.002. In addition, the neuronal network basically retained these characteristics for at least 5 h. These results indicated that we have successfully constructed a learning and memory model of hippocampal neurons on the in vitro MEA, contributing to understanding learning and memory based on synaptic plasticity. The proposed PPy/SWCNTs-modified in vitro MEA will provide a promising platform for the exploration of learning and memory mechanism and their applications in vitro.

Sensitive detection of electrophysiology and dopamine vesicular exocytosis of hESC-derived dopaminergic neurons using multifunctional microelectrode array.

Clinical transplantation of human embryonic stem cells derived dopaminergic neurons (hESC-DDNs) is expected to be a potential therapy for treating neurodegenerative diseases. However, the assessment of the physiological functions, including electrophysiology and dopamine (DA) vesicular exocytosis of hESC-DDNs are not impeccable currently, which deeply limits the clinical application of hESC-DDNs. To overcome this challenge, we developed a multifunctional microelectrode array (MEA) which can detect both electrophysiological signals and DA vesicular exocytosis. The reduced oxidation graphene, poly(3,4-ethylenedioxythiophene) and poly (sodium-4-styrenesultanate) nanocomposites (rGO/PEDOT:PSS) were electrochemically deposited on the MEAs to improve their electrical characterizations with low impedance and small phase delay, and electrochemical characterizations with low oxidation potential, low detection limit, high sensitivity, wide linear range and high sensitivity. In the hESC-DDNs experiment, the modified MEA could detect electrophysiological signals with low noise (25 µV) and high signal-to-noise ratio (>5.4), and the weak current signals generated by DA vesicular exocytosis with high sensitivity (∼pA), high time resolution (sub-millisecond) and low noise (3 pA). Moreover, due to increased accuracy, the MEA could clearly distinguish two typical kinds of exocytosis spike events ("Spikes with foot" and "Spikes without foot") and found that the slow and low release through the fusion pore was an important mode of DA vesicular exocytosis in hESC-DDNs. Our work proved that the hESC-DDNs had the basic physiological functions as human dopaminergic neurons, which would be beneficial to the clinical application of the hESC-DDNs.

Multifunctional self-driven origami paper-based integrated microfluidic chip to detect CRP and PAB in whole blood.

Gastrointestinal fistula, a complication of gastrointestinal cancer surgery, has a high mortality rate. Detection of both C-reactive protein (CRP) and prealbumin (PAB) is advantageous in the auxiliary diagnosis of postoperative complications. However, traditional detection methods are not capable of on-site rapid detection. In an attempt to overcome these challenges, a multifunctional origami-paper-based device (ePADs) was developed to simultaneously detect CRP and PAB in whole blood. After integration, functionalization, and modification, the electrochemical dual-parameter device was capable of separating blood cells and detecting target analytes. The plasma separation performance revealed a sample diffusion time of 75 s for a whole blood sample volume of 73.3 µL. The efficiency of the device in separating blood cells was 99.91%. Electrochemical results showed that the multifunctional device exhibited linearity between 5 pg mL-1 and 1 µg mL-1 for CRP (R2 = 0.990), and between 10 pg mL-1 and 1 µg mL-1 for PAB (R2 = 0.998). The limits of detection for CRP and PAB were 5 and 10 pg mL-1, respectively (S/N = 3). We also successfully evaluated the accuracy of the dual-parameter device with clinical whole blood samples. Based on these results, the multifunctional device can facilitate clinical detection and provide a new platform for domestic point-of-care testing.

A Dual-Channel Intelligent Point-of-Care Testing System for Soluble Programmed Death-1 and Programmed Death-Ligand 1 Detection Based on Folding Paper-Based Immunosensors.

Both programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) are important proteins in cancer immunotherapy. Soluble forms (sPD-1 and sPD-L1) have potential for determining treatment and prognosis monitoring. However, there is a lack of detection methods for point-of-care testing (POCT) of these two proteins, so a low-cost rapid detection platform is urgently needed. To solve this problem, a dual-channel electrochemical platform, including a folding paper-based immunosensor and a POCT system for rapid simultaneous detection of these two proteins was designed and fabricated. The immunosensor consists of a three-electrode system and a reaction cell. The surface of the working electrode was modified with nanocomposites synthesized from amine-functionalized single-walled carbon nanotubes, new methylene blue, and gold nanoparticles. Antibodies to sPD-1 and sPD-L1 were also immobilized on the working electrode surface. A differential pulse voltammetry electrochemical method was adopted. The immunosensor was able to detect sPD-1 and sPD-L1 in the ranges of 50 pg/mL to 50 ng/mL and 5 pg/mL to 5 ng/mL, respectively. The limits of detection were 10 and 5 pg/mL. Using this detection platform, sPD-1 and sPD-L1 in plasma were detected by both enzyme-linked immunosorbent assay and the immunosensor, which has good application potential.

Electrochemical Microfluidic Paper-Based Aptasensor Platform Based on a Biotin-Streptavidin System for Label-Free Detection of Biomarkers.

Timely and rapid detection of biomarkers is extremely important for the diagnosis and treatment of diseases. However, going to the hospital to test biomarkers is the most common way. People need to spend a lot of money and time on various tests for potential disease detection. To make the detection more convenient and affordable, we propose a paper-based aptasensor platform in this work. This device is based on a cellulose paper, on which a three-electrode system and microfluidic channels are fabricated. Meanwhile, novel nanomaterials consisting of amino redox graphene/thionine/streptavidin-modified gold nanoparticles/chitosan are synthesized and modified on the working electrode of the device. Through the biotin-streptavidin system, the aptamer whose 5'end is modified with biotin can be firmly immobilized on the electrode. The detection principle is that the current generated by the nanomaterials decreases proportionally to the concentration of targets owing to the combination of the biomarker and its aptamer. 17ß-Estradiol (17ß-E2), as one of the widely used diagnostic biomarkers of various clinical conditions, is adopted for verifying the performance of the platform. The experimental results demonstrated that this device enables the determination of 17ß-E2 in a wide linear range of concentrations of 10 pg mL-1 to 100 ng mL-1 and the limit of detection is 10 pg mL-1 (S/N = 3). Moreover, it enables the detection of targets in clinical serum samples, demonstrating its potential to be a disposable and convenient integrated platform for detecting various biomarkers.

An origami paper-based nanoformulated immunosensor detects picograms of VEGF-C per milliliter of blood.

Detecting vascular endothelial growth factor C (VEGF-C), a kind of tumor biomarker, is of significant clinical importance in evaluating the prognosis of patients with cancer. However, laboratory analyses are usually not suitable for point-of-care testing because they are expensive and time consuming. In response to these challenges, we fabricated an origami paper-based microfluidic electrochemical device. To improve the specificity of VEGF-C detection, nanocomposites, synthesized by new methylene blue (NMB), amino-functional single-walled carbon nanotubes (NH2-SWCNTs), and gold nanoparticles (AuNPs), were used to modify the surface of working electrodes. Results of electrochemical detection showed that the immunosensor had excellent linearity, ranging from 0.01 to 100 ng mL-1 (R2 = 0.988), and the limit of detection was 10 pg mL-1. To confirm the high specificity of the device under real-world conditions, we evaluated the device using clinical serum samples from our hospital. The results demonstrated that the device had an excellent performance and could provide a platform for real-time detection of cancers.

Construction of a Vibrio anguillarum flagellin B mutant and analysis of its immuno-stimulation effects on Macrobrachium rosenbergii.

Vibrio anguillarum is a globally distributed aquatic pathogen, and its flagellin B (FlaB) protein can evoke innate immune responses in hosts. In order to explore the role of FlaB in V. anguillarum infection, we constructed a FlaB-deficient mutant using overlapping PCR and two-step homologous recombination, and gene sequencing confirmed successful knockout of the FlaB gene. Scanning electron microscopy showed no significant differences in the morphological structure of the flagellum between wild-type and FlaB-deficient strains. The mutant was subsequently injected into the freshwater prawn (Macrobrachium rosenbergii) to explore its pathogenicity in the host, and expression of myeloid differentiation factor 88, prophenoloxidase, catalase, superoxide dismutase and glutathione peroxidase was investigated by real-time PCR. The results showed that deletion of FlaB had little effect on V. anguillarum-induced expression of these immune-related genes (p > 0.05). In general, the FlaB mutant displayed similar flagella morphology and immune characteristics to the wild-type strain, hence we speculated that knockout of FlaB might promote the expression and function of other flagellin proteins. Furthermore, this study provides a rapid and simple method for obtaining stable mutants of V. anguillarum free from foreign plasmid DNA.

Low sample volume origami-paper-based graphene-modified aptasensors for label-free electrochemical detection of cancer biomarker-EGFR.

In this work, an electrochemical paper-based aptasensor was fabricated for label-free and ultrasensitive detection of epidermal growth factor receptor (EGFR) by employing anti-EGFR aptamers as the bio-recognition element. The device used the concept of paper-folding, or origami, to serve as a valve between sample introduction and detection, so reducing sampling volumes and improving operation convenience. Amino-functionalized graphene (NH2-GO)/thionine (THI)/gold particle (AuNP) nanocomposites were used to modify the working electrode not only to generate the electrochemical signals, but also to provide an environment conducive to aptamer immobilization. Electrochemical characterization revealed that the formation of an insulating aptamer-antigen immunocomplex would hinder electron transfer from the sample medium to the working electrode, thus resulting in a lower signal. The experimental results showed that the proposed aptasensor exhibited a linear range from 0.05 to 200 ngmL-1 (R 2 = 0.989) and a detection limit of 5 pgmL-1 for EGFR. The analytical reliability of the proposed paper-based aptasensor was further investigated by analyzing serum samples, showing good agreement with the gold-standard enzyme-linked immunosorbent assay.

Folding Paper-Based Aptasensor Platform Coated with Novel Nanoassemblies for Instant and Highly Sensitive Detection of 17ß-Estradiol.

Owing to its critical role in the development of female reproductive tissues and as a clinical biomarker, there is an urgent need to develop a rapid and cost-effective method to sensitively detect 17ß-estradiol (E2). In this work, a folding aptasensor platform with microfluidic channels for the label-free electrochemical detection of E2 is described. The platform, designed with a delicate folding structure, integrating filter holes, microfluidic channels, reaction chambers, and a three-electrode system, is extremely easy to use. To increase the detection sensitivity and immobilize the aptamer, we synthesized a novel nanoassembly consisting of amine-functionalized single-walled carbon nanotube/new methylene blue/gold nanoparticles (AuNPs) and modified the working electrode with this nanoassembly. The calibration curve obtained from the experimental results exhibited a linear range between 10 pg mL-1 and 500 ng mL-1 (R2 = 0.993), and a detection limit of 5 pg mL-1 was achieved (S/N = 3). Furthermore, experiments to detect E2 in clinical serum were conducted, and the results were highly similar to those obtained using a large electrochemical luminescence apparatus. By integrating multiple functional components, adopting novel nanoassemblies, and using a folding structure, this paper-based platform not only has great potential as a simple and convenient integrated device for point-of-care testing of E2, but also as a portable, low-cost, and highly sensitive aptasensor platform capable of detecting many diagnostic biomarkers with the appropriate aptamers.

Label-free microfluidic paper-based electrochemical aptasensor for ultrasensitive and simultaneous multiplexed detection of cancer biomarkers.

Simultaneous detection of multiple tumor biomarkers in body fluids could facilitate early diagnosis of lung cancer, so as to provide scientific reference for clinical treatment. This paper depicted a multi-parameter paper-based electrochemical aptasensor for simultaneous detection of carcinoembryonic antigen (CEA) and neuron-specific enolase (NSE) in a clinical sample with high sensitivity and specificity. The paper-based device was fabricated through wax printing and screen-printing, which enabled functions of sample filtration and sample auto injection. Amino functional graphene (NG)-Thionin (THI)- gold nanoparticles (AuNPs) and Prussian blue (PB)- poly (3,4- ethylenedioxythiophene) (PEDOT)- AuNPs nanocomposites were synthesized respectively. They were used to modify the working electrodes not only for promoting the electron transfer rate, but also for immobilization of the CEA and NSE aptamers. A label-free electrochemical method was adopted, enabling a rapid simple point-of-care testing. Experimental results showed that the proposed multi-parameter aptasensor exhibited good linearity in ranges of 0.01-500 ng mL-1 for CEA (R2 = 0.989) and 0.05-500 ng mL-1 for NSE (R2 = 0.944), respectively. The limit of detection (LOD) was 2 pg mL-1 for CEA and 10 pg mL-1 for NSE. In addition, the device was evaluated using clinical serum samples and received a good correlation with large electrochemical luminescence (ECL) equipment, which would offer a new platform for early cancer diagnostics, especially in those resource-limit areas.

Electrochemical integrated paper-based immunosensor modified with multi-walled carbon nanotubes nanocomposites for point-of-care testing of 17ß-estradiol.

17ß-estradiol (17ß-E2) plays a critical role in regulating reproduction in human, there is therefore an urgent need to detect it sensitively and precisely in a cost-effective and easy method. In this paper, a label-free integrated microfluidic paper-based analytical device was developed for highly sensitive electrochemical detection of 17ß-E2. The microfluidic channel of the paper-based sensor was fabricated with wax printing and the three electrodes, including working, counter and reference electrode were screen-printed. Multi-walled carbon nanotubes (MWCNTs)/ thionine (THI)/ gold nanoparticles (AuNPs) Nano composites were synthesized and coated on screen-printed working electrode (SPWE) for the immobilization of anti-E2. In this electro-chemical system of paper-based immunoassay, THI molecules serving as an electrochemical mediator while MWCNTs and AuNPs, due to their excellent electrical conductivities, could accelerate electron transfer for the signal amplification. Experimental results revealed that the immunoassay is able to detect 17ß-E2 as low as 10 pg mL-1, with a linear range from 0.01 to 100 ng mL-1. This microfluidic paper-based immunosensor would provide a new platform for low cost, sensitive, specific, and point-of-care diagnosis of 17ß-E2.

A wireless point-of-care testing system for the detection of neuron-specific enolase with microfluidic paper-based analytical devices.

Neuron-specific enolase (NSE) had clinical significance on diagnosis, staging, monitoring effect and judging prognosis of small cell lung cancer. Thus, there had a growing demand for the on-site testing of NSE. Here, a wireless point-of-care testing (POCT) system with electrochemical measurement for NSE detection was developed and verified. The wireless POCT system consisted of microfluidic paper-based analytical devices (µPADs), electrochemical detector and Android's smartphone. Differential pulse voltammetry (DPV) measurement was adopted by means of electrochemical detector which including a potentiostat and current-to-voltage converter. µPADs were modified with nanocomposites synthesized by Amino functional graphene, thionine and gold nanoparticles (NH2-G/Thi/AuNPs) as immunosensors for NSE detection. Combined with µPADs, the performance of the wireless POCT system was evaluated. The peak currents showed good linear relationship of the logarithm of NSE concentration ranging from 1 to 500ngmL-1 with the limit of detection (LOD) of 10pgmL-1. The detection results were automatically stored in EEPROM memory and could be displayed on Android's smartphone through Bluetooth in real time. The detection results were comparable to those measured by a commercial electrochemical workstation. The wireless POCT system had the potential for on-site testing of other tumor markers.

A novel label-free microfluidic paper-based immunosensor for highly sensitive electrochemical detection of carcinoembryonic antigen.

In this work, a highly sensitive label-free paper-based electrochemical immunosensor employing screen-printed working electrode (SPWE) for detection of carcinoembryonic antigen (CEA) was fabricated. In order to raise the detection sensitivity and immobilize anti-CEA, amino functional graphene (NH2-G)/thionine (Thi)/gold nanoparticles (AuNPs) nanocomposites were synthesized and coated on SPWE. The principle of the immunosensor determination was based on the fact that the decreased response currents of Thi were proportional to the concentrations of corresponding antigens due to the formation of antibody-antigen immunocomplex. Experimental results revealed that the immunoassay enabled the determination of standard CEA solutions with linear working ranges of 50pgmL(-1) to 500ngmL(-1), the limit of detections for CEA is 10pgmL(-1) (S/N=3) and its corresponding correlation coefficients were 0.996. Furthermore, the proposed immunosensor could be used for the determination of clinical serum samples. A large number of clinical serum samples were detected and the relative errors between measured values and reference concentrations were calculated. Results showed that this novel paper-based electrochemical immunosensor could provide a new platform for low cost, sensitive, specific, and point-of-care diagnosis in cancer detection.

A Label-Free Microelectrode Array Based on One-Step Synthesis of Chitosan-Multi-Walled Carbon Nanotube-Thionine for Ultrasensitive Detection of Carcinoembryonic Antigen.

Carcinoembryonic antigen (CEA) has been an extensively used tumor marker responsible for clinical early diagnosis of cervical carcinomas, and pancreatic, colorectal, gastric and lung cancer. Combined with micro-electro mechanical system (MEMS) technology, it is important to develop a novel immune microelectrode array (MEA) not only for rapid analysis of serum samples, but also for cell detection in vitro and in vivo. In this work, we depict a simple approach to modify chitosan-multi-walled carbon nanotubes-thionine (CS-MWCNTs-THI) hybrid film through one-step electrochemical deposition and the CS-MWCNTs-THI hybrid films are successfully employed to immobilize anti-CEA for fabricating simple, label-free, and highly sensitive electro-chemical immune MEAs. The detection principle of immune MEA was based on the fact that the increasing formation of the antigen-antibody immunocomplex resulted in the decreased response currents and the relationship between the current reductions with the corresponding CEA concentrations was directly proportional. Experimental results indicated that the label-free MEA had good selectivity and the limit of detection for CEA is 0.5 pg/mL signal to noise ratio (SNR) = 3. A linear calibration plot for the detection of CEA was obtained in a wide concentration range from 1 pg/mL to 100 ng/mL (r = 0.996). This novel MEA has potential applications for detecting CEA for the research on cancer cells and cancer tissue slices as well as for effective early diagnosis.

Highly sensitive detection of quantal dopamine secretion from pheochromocytoma cells using neural microelectrode array electrodeposited with polypyrrole graphene.

For the measurement of events of dopamine (DA) release as well as the coordinating neurotransmission in the nerve system, a neural microelectrode array (nMEA) electrodeposited directionally with polypyrrole graphene (PG) nanocomposites was fabricated. The deposited graphene significantly increased the surface area of working electrode, which led to the nMEA (with diameter of 20 µm) with excellent selectivity and sensitivity to DA. Furthermore, PG film modification exhibited low detection limit (4 nM, S/N = 3.21), high sensitivity, and good linearity in the presence of ascorbic acid (e.g., 13933.12 µA mM(-1) cm(-2) in the range of 0.8-10 µM). In particular, the nMEA combined with the patch-clamp system was used to detect quantized DA release from pheochromocytoma cells under 100 mM K(+) stimulation. The nMEA that integrates 60 microelectrodes is novel for detecting a large number of samples simultaneously, which has potential for neural communication research.

Carbon fiber ultramicrodic electrode electrodeposited with over-oxidized polypyrrole for amperometric detection of vesicular exocytosis from pheochromocytoma cell.

Vesicular exocytosis is ubiquitous, but it is difficult to detect within the cells' communication mechanism. For this purpose, a 2 µm ultramicrodic carbon fiber electrode was fabricated in this work based on electrodeposition with over-oxidized polypyrrole nanoparticle (PPyox-CFE), which was applied successfully for real-time monitoring of quantal exocytosis from individual pheochromocytoma (PC12) cells. PPyox-CFE was evaluated by dopamine (DA) solutions through cyclic voltammetry and amperometry electrochemical methods, and results revealed that PPyox-CFE improved the detection limit of DA. In particular, the sensitivity of DA was improved to 24.55 µA·µM(-1)·µm(-2) using the PPyox-CFE. The ultramicrodic electrode combined with the patch-clamp system was used to detect vesicular exocytosis of DA from individual PC12 cells with 60 mM K+ stimulation. A total of 287 spikes released from 7 PC12 cells were statistically analyzed. The current amplitude (Imax) and the released charge (Q) of the amperometric spikes from the DA release by a stimulated PC12 cell is 45.1 ± 12.5 pA and 0.18 ± 0.04 pC, respectively. Furthermore, on average ~562,000 molecules were released in each vesicular exocytosis. PPyox-CFE, with its capability of detecting vesicular exocytosis, has potential application in neuron communication research.

A rapid and highly sensitive portable chemiluminescent immunosensor of carcinoembryonic antigen based on immunomagnetic separation in human serum.

To detect a biomarker for lung cancer, carcinoembryonic antigen (CEA), a highly sensitive, selective, rapid and portable immunosensor based on immunomagnetic separation and chemiluminescence immunoassay was introduced. A sandwich scheme assay has been utilized with horseradish peroxidase (HRP) labeled anti-CEA antibody and immunomagnetic beads (IMBs). The presence of target protein CEA caused the formation of the sandwich structures (IMBs-CEA-HRP labeled antibody). IMBs were applied to capture CEA and immobilize CEA through the external magnetic field. The HRP at the surface of the antibody catalytically oxidized the luminescence substrate to generate optical signals which were detected by a portable home-made luminometer and which were directly proportional to the concentration of CEA in the samples. The signals were dependent on CEA concentrations in a linear range from 0 to 50 ng mL(-1). The limit of detection (LOD) of this method was as low as 5.0 pg mL(-1) (S/N=3). The novel immunosensor was highly sensitive with an assay time of <35 min. The intra- and inter-assay coefficients of variation were <10%. The anti-CEA antibody can be bound to the bead efficiently with a conjugation rate of 73%. IMBs could be stored in 4 °C protecting from light for 2 months without obvious reduction of biological activity. Human reference sera mixed with various concentrations of CEA were tested with the proposed method and commercial enzyme-linked immunosorbent assay (ELISA) kit, and a good linear relationship was obtained. This proposed technique demonstrated an excellent performance for quantifying CEA and was expected to be used for clinical testing.