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.

Integrated Three-Electrode Dual-Mode Detection Chip for Place Cell Analysis: Dopamine Facilitates the Role of Place Cells in Encoding Spatial Locations of Novel Environments and Rewards.

The functioning of place cells requires the involvement of multiple neurotransmitters, with dopamine playing a critical role in hippocampal place cell activity. However, the exact mechanisms through which dopamine influences place cell activity remain largely unknown. Herein, we present the development of the integrated three-electrode dual-mode detection chip (ITDDC), which enables simultaneous recording of the place cell activity and dopamine concentration fluctuation. The working electrode, reference electrode, and counter electrode are all integrated within the ITDDC in electrochemical detection, enabling the real-time in situ monitoring of dopamine concentrations in animals in motion. The reference, working, and counter electrodes are surface-modified using PtNPs and polypyrrole, PtNPs and PEDOT:PSS, and PtNPs, respectively. This modification allows for the detection of dopamine concentrations as low as 20 nM. We conducted dual-mode testing on mice in a novel environment and an environment with food rewards. We found distinct dopamine concentration variations along different paths within a novel environment, implying that different dopamine levels may contribute to spatial memory. Moreover, environmental food rewards elevate dopamine significantly, followed by the intense firing of reward place cells, suggesting a crucial role of dopamine in facilitating the encoding of reward-associated locations in animals. The real-time and in situ recording capabilities of ITDDC offer new opportunities to investigate the interplay between electrophysiology and dopamine during animal exploration and reward-based memory and provide a novel glimpse into the correlation between dopamine levels and place cell activity.

Cytosine base editors (CBEs) for inducing targeted DNA base editing in Nicotiana benthamiana.

BACKGROUND: The base editors can introduce point mutations accurately without causing double-stranded DNA breaks or requiring donor DNA templates. Previously, cytosine base editors (CBEs) containing different deaminases are reported for precise and accurate base editing in plants. However, the knowledge of CBEs in polyploid plants is inadequate and needs further exploration. RESULTS: In the present study, we constructed three polycistronic tRNA-gRNA expression cassettes CBEs containing A3A, A3A (Y130F), and rAPOBEC1(R33A) to compare their base editing efficiency in allotetraploid N. benthamiana (n = 4x). We used 14 target sites to compare their editing efficiency using transient transformation in tobacco plants. The sanger sequencing and deep sequencing results showed that A3A-CBE was the most efficient base editor. In addition, the results showed that A3A-CBE provided most comprehensive editing window (C1 ~ C17 could be edited) and had a better editing efficiency under the base background of TC. The target sites (T2 and T6) analysis in transformed N. benthamiana showed that only A3A-CBE can have C-to-T editing events and the editing efficiency of T2 was higher than T6. Additionally, no off-target events were found in transformed N. benthamiana. CONCLUSIONS: All in all, we conclude that A3A-CBE is the most suitable vector for specific C to T conversion in N. benthamiana. Current findings will provide valuable insights into selecting an appropriate base editor for breeding polyploid plants.

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.

PtNPs/rGO-GluOx/mPD Directionally Electroplated Dual-Mode Microelectrode Arrays for Detecting the Synergistic Relationship between the Cortex and Hippocampus of Epileptic Rats.

Precise and directional couplings of functional nanomaterials with implantable microelectrode arrays (IMEAs) are critical for the manufacture of sensitive enzyme-based electrochemical neural sensors. However, there is a gap between the microscale of IMEA and conventional bioconjugation techniques for enzyme immobilization, which leads to a series of challenges such as limited sensitivity, signal crosstalk, and high detection voltage. Here, we developed a novel method using carboxylated graphene oxide (cGO) to directionally couple the glutamate oxidase (GluOx) biomolecules onto the neural microelectrode to monitor glutamate concentration and electrophysiology in the cortex and hippocampus of epileptic rats under RuBi-GABA modulation. The resulting glutamate IMEA exhibited good performance involving less signal crosstalk between microelectrodes, lower reaction potential (0.1 V), and higher linear sensitivity (141.00 ± 5.66 nA µM-1 mm-2). The excellent linearity ranged from 0.3 to 68 µM (R = 0.992), and the limit of detection was 0.3 µM. For epileptic rats, the proposed IMEA sensitively obtained synergetic variations in the action potential (Spike), local field potentials (LFPs), and glutamate of the cortex and hippocampus during seizure and RuBi-GABA inhibition. We found that the increase in glutamate preceded the burst of electrophysiological signals. At the same time, both changes in the hippocampus preceded the cortex. This reminded us that glutamate changes in the hippocampus could serve as important indicators for early warning of epilepsy. Our findings provided a new technical strategy for directionally stabilizing enzymes onto the IMEA with versatile implications for various biomolecules' modification and facilitated the development of detecting tools for understanding the neural mechanism.

Genome-Wide Identification and Structural Characterization of Growth-Regulating Factors (GRFs) in Actinida eriantha and Actinidia chinensis.

Growth-regulating factors (GRFs) encode plant-specific transcription factors that play a vital role in regulation of plant growth, development, and stress response. Although GRFs have been identified in various plants, there is no reported work available in Actinidia (commonly known as kiwifruit) so far. In the present study, we identified 22 GRF genes on A. chinensis (hereafter A. chinensis is referred to as Ac, and GRF genes in A. chinensis are referred to as AcGRF) distributed on 17 chromosomes and one contig, and 26 GRF genes in A. eriantha (hereafter A. eriantha is referred to as Ae, and GRF genes in A. eriantha are referred to as AeGRF) distributed on 21 chromosomes. Phylogenetic analysis showed that kiwifruit GRF proteins were clustered into five distinct groups. Additionally, kiwifruit GRFs showed motif composition and gene structure similarities within the same group. Synteny analysis showed that whole-genome duplication played a key role in the expansion of the GRF family in kiwifruit. The higher expression levels of kiwifruit GRFs in young tissues and under stress conditions indicated their regulatory role in kiwifruit growth and development. We observed two genes in Ae (AeGRF6.1, AeGRF 6.2) and two genes in Ac (AcGRF 6.1, AeGRF 6.2) significantly upregulated in different RNA-seq datasets. The presence of conserved protein structures and cis-regulatory elements caused functional divergence in duplicated gene pairs. The subcellular localization indicated the presence of kiwifruit GRFs in the nucleus of the plant cell. Protein-protein interaction analysis predicted AtGIF protein orthologs for AcGRFs and AeGRFs. Taken together, we systematically analyzed the characterization of kiwifruit GRF family members for their potential role in kiwifruit development and Pseudomonas syringae pv. actinidiae (Psa.) invasion response. Further functional studies of kiwifruit GRFs in plant growth, development, and stress response will provide valuable insights for kiwifruit breeders.

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.

SWCNTs/PEDOT:PSS-Modified Microelectrode Arrays for Dual-Mode Detection of Electrophysiological Signals and Dopamine Concentration in the Striatum under Isoflurane Anesthesia.

Accurate detection of the degree of isoflurane anesthesia during a surgery is important to avoid the risk of overdose isoflurane anesthesia timely. To address this challenge, a four-shank implantable microelectrode array (MEA) was fabricated for the synchronous real-time detection of dual-mode signals [electrophysiological signal and dopamine (DA) concentration] in rat striatum. The SWCNTs/PEDOT:PSS nanocomposites were modified onto the MEAs, which significantly improved the electrical and electrochemical performances of the MEAs. The electrical performance of the modified MEAs with a low impedance (16.20 ± 1.68 kΩ) and a small phase delay (-27.76 ± 0.82°) enabled the MEAs to detect spike firing with a high signal-to-noise ratio (> 3). The electrochemical performance of the modified MEAs with a low oxidation potential (160 mV), a low detection limit (10 nM), high sensitivity (217 pA/µM), and a wide linear range (10 nM-72 µM) met the specific requirements for DA detection in vivo. The anesthetic effect of isoflurane was mediated by inhibiting the spike firing of D2_SPNs (spiny projection neurons expressing the D2-type DA receptor) and the broadband oscillation rhythm of the local field potential (LFP). Therefore, the spike firing rate of D2_SPNs and the power of LFP could reflect the degree of isoflurane anesthesia together. During the isoflurane anesthesia-induced death procedure, we found that electrophysiological activities and DA release were strongly inhibited, and changes in the DA concentration provided more details regarding this procedure. The dual-mode recording MEA provided a detection method for the degree of isoflurane anesthesia and a prediction method for fatal overdose isoflurane anesthesia.

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.

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 high-sensitive nano-modified biosensor for dynamic monitoring of glutamate and neural spike covariation from rat cortex to hippocampal sub-regions.

BACKGROUND: Hippocampus is a critical part of brain tissue involved in many cognitive neural activities. They are controlled by various neurotransmitters such as glutamate (Glu), and affected by electrophysiology. NEW METHOD: Herein, we fabricated a 16-site (25µm in diameter) microelectrode array (MEA) biosensor applied in dual-mode tests including Glu and neural spike measurements. METHODS: All the 16 recording sites were electrodeposited with platinum nanoparticles (PtNPs) and 8 sites were used for electrical recording. Glutamate oxidase enzyme (Gluox) and 1,3-Phenylenediamine (mPD) layer were specially modified on the other 8 sites for Glu recording. The dual-mode MEA was implanted from cortex to hippocampus of anesthetized rat to record Glu content and firing rate. RESULTS: The electrical sites showed much lower impedance. The Glu sites showed much higher sensitivity(7.807 pA/µM), and ideal selectivity to the major molecules in brain. The post calibration sensitivity (3.935 pA/µM) maintained on a positive level. Different Glu content peaks including cortex (18.32µM) and hippocampal CA1 (4.39µM), CA3 (10.16µM), dentate gyrus (DG, two layers: 5.36µM and 10.34µM) have detected. The corresponded firing rate was recorded, too. COMPARISON WITH EXISTING METHODS: This modification showed much lower impedance and much higher sensitivity. We obtained more neuron activities simultaneously by dual-mode recording. The covariation of Glu and neural spike signals was discovered in the specific hippocampus sub-region. CONCLUSIONS: The covariation between Glu and firing rate changes were synchronous, and effected by regions. The dual-mode signals were useful to find the neurology disease mechanism.

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.