Alumina inorganic molecularly imprinted polymer modified multi-walled carbon nanotubes for uric acid detection in sweat.

Alumina inorganic molecularly imprinted polymer (MIP) modified multi-walled carbon nanotubes (MWCNTs) on a glassy carbon electrode (MWCNTs-Al2O3-MIP/GCE) was firstly designed and fabricated by one-step electro deposition technique for the detection of uric acid (UA) in sweat. The UA templates were embedded within the inorganic MIP by co-deposition with Al2O3. Through the evaluation of morphology and structure by Field Emission Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM), it was verified that the specific recognition sites can be fabricated in the electrodeposited Al2O3 molecular imprinted layer. Due to the high selectivity of molecular imprinting holes, the MWCNTs-Al2O3-MIP/GCE electrode demonstrated an impressive imprinting factor of approximately 2.338 compared to the non-molecularly imprinted glassy carbon electrode (MWCNTs-Al2O3-NIP/GCE) toward uric acid detection. Moreover, it exhibited a remarkable limit of detection (LOD) of 50 nM for UA with wide detection range from 50 nM to 600 µM. The MWCNTs-Al2O3-MIP/GCE electrode also showed strong interference resistance against common substances found in sweat. These results highlight the excellent interference resistance and selectivity of MWCNTs-Al2O3-MIP/GCE sensor, positioning it as a novel sensing platform for non-invasive uric acid detection in human sweat.

Comprehensive Analysis and Experimental Validation of FOXD2 as a Novel Potential Prognostic Biomarker Associated with Immune Infiltration in Head and Neck Squamous Cell Carcinoma.

BACKGROUND: The role of Forkhead Box D2 (FOXD2) in head and neck squamous cell carcinoma (HNSC) has never been studied. OBJECT: Our object was to explore the role of FOXD2 in HNSC. METHODS: Clinical data for patients with HNSC was obtained from TCGA. Our study examined the atypical expression of FOXD2 in both HNSC and pan-cancer, along with its diagnostic and prognostic implications, as well as the association between FOXD2 expression and clinical characteristics, immune infiltration, immune checkpoint genes, and MSI. Gene set enrichment analysis (GESA) was used to investigate the potential regulation network of FOXD2 in HNSC. We analyze the genomic alterations of FOXD2 in HNSC. GSE13397 and qRT-PCR were used for the validation of FOXD2 expression. RESULTS: FOXD2 was aberrantly expressed in 24 tumors. FOXD2 was significantly up-regulated in HNSC compared to normal head and neck tissue (p < 0.001). High FOXD2 expression was associated with the histologic grade of the patient with HNSC (p < 0.001), lymphovascular infiltration (p = 0.002) and lymph node neck dissection (p = 0.002). In HNSC, an autonomous correlation between FOXD2 expression and OS was observed (HR: 1.36; 95% CI: 1.04-1.78; p = 0.026). FOXD2 was associated with the neuronal system, neuroactive ligand-receptor interaction, and retinoblastoma gene in cancer. FOXD2 was associated with immune infiltration, immune checkpoints, and MSI. The somatic mutation rate of FOXD2 in HNSC was 0.2%. FOXD2 was significantly up-regulated in HNSC cell lines. CONCLUSION: Our findings suggest that FOXD2 has the potential to serve as a prognostic biomarker and immunotherapeutic target for individuals with HNSC.

Transistor-based immunosensor using AuNPs-Ab2-HRP enzyme nanoprobe for the detection of antigen biomarker in human blood.

Alpha-fetoprotein (AFP) is inextricably linked to various diseases, including liver cancer. Thus, detecting the content of AFP in biology has great significance in diagnosis, treatment, and intervention. Motivated by the urgent need for affordable and convenient electronic sensors in the analysis and detection of aqueous biological samples, we combined the solution-gated graphene transistor (SGGT) with the catalytic reaction of enzyme nanoprobes (HRP-AuNPs-Ab2) to accurately sense AFP. The SGGT immunosensor demonstrated high specificity and stability, excellent selectivity, and excessive linearity over a range of 4 ng/mL to 500 ng/mL, with the lower detection limit down to 1.03 ng/mL. Finally, clinical samples were successfully detected by the SGGT immunosensor, and the results were consistent with chemiluminescence methods that are popular in hospitals for detecting AFP. Notably, the SGGT immunosensor is also recyclable, so it has excellent potential for use in high-throughput detection.

A 3D phytic acid cross-linked high-porous conductive hydrogel integrating g-C3N4 for electrochemical multiplex sensing of heavy metal ions.

It is a great challenge to develop an effective super-sensitive capture method for multiplex heavy metal ions (HMIs), because HMIs is extremely toxic to public health and the environment, what's more their contamination is usually multiplex ions pollution. In this work, a 3D high-porous conductive polymer hydrogel was designed and prepared with high-stable and easy mass production, which is very favorable for the industrialization. The polymer hydrogel (g-C3N4-P(Ani-Py)-PAAM) was formed from the mixture of aniline pyrrole copolymer and acrylamide cross-linked with phytic acid as dopant and cross-linker and integrated with g-C3N4. The 3D networked high-porous hydrogel not only exhibits excellent electrical conductivity, but also provides a large surface area for increasing the number of immobilized ions. Importantly, the 3D high-porous conductive polymer hydrogel was applied successfully in electrochemical multiplex sensing of HIMs. The prepared sensor used differential pulse anodic stripping voltammetry exhibited high sensitivities, low detection limit and wide detection ranges for Cd2+, Pb2+, Hg2+ and Cu2+, respectively. Moreover, the sensor showed a high accuracy in lake water test. The preparation and application of the hydrogel in electrochemical sensor provided an availability strategy to capture and detect the various HMIs by electrochemistry in solution and has great commercial application prospect.

Long-Term Outcomes of Nasopharyngeal Carcinoma by Epstein-Barr Virus Status in the Chinese Population: A Multicenter Investigation.

Background: Because the vast majority of nasopharyngeal carcinoma (NPC) in Chinese patients is a direct result of Epstein-Barr virus (EBV) infection, there is a dearth of data for EBV-negative patients in this population. This multicenter study sought to examine the clinical characteristics of EBV-negative patients and compare long-term outcomes with a propensity-matched (1:1.5) EBV-positive cohort. Methods: NPC patients with known EBV status from four hospitals were collated (2013-2021). A logistic regression model was conducted to evaluate the relationship between patient characteristics and EBV status. The Kaplan-Meier method and Cox regression analysis were used to analyze survival data. Results: This study analyzed 48 (40%) EBV-negative and 72 (60%) EBV-positive patients. The median follow-up time was 63.5 months. Most EBV-negative NPC patients (77.1%) were diagnosed in advanced stages with a higher rate (87.5%) of positive lymph node disease, and no significant prognostic factors were discerned in this subpopulation. The EBV-negative disease was more associated with the keratinizing subtype (18.8% vs. 1.4%, p < 0.05). Compared to EBV-negative NPC patients, EBV-positive NPC patients were more likely to develop a local recurrence (9.7% vs. 0%, p = 0.026). There was no statistical difference in mortality (EBV-negative vs. EBV- positive, 8.3% vs. 4.2%, p = 0.34) during the follow-up period. Although the median PFS and median OS were not reached, the 3-year PFS rate was 68.8% vs. 70.8% (EBV-negative vs. EBV-positive, p = 0.06), the 3-year OS rate was 70.8% vs. 76.4% (EBV-negative vs. EBV-positive, p = 0.464), the 5-year PFS rate was 56.3% vs. 50% (EBV-negative vs. EBV-positive, p = 0.451), and the 5-year OS rate was 56.3% vs. 58.3% (EBV-negative vs. EBV-positive, p = 0.051), respectively. These data show that EBV-positive NPC patients seem to have a tendency to gain better survival compared with EBV-negative NPC patients. Conclusions: Most of the EBV-negative patients were in the middle and late stages at the time of diagnosis and were more associated with the keratinizing subtype. EBV status may be associated with prognosis in NPC. EBV positivity seems to be associated with better survival in NPC patients. Still, due to the small cohort of patients and the short observation period for a number of patients, further work is required to corroborate these conclusions.

Optimizing induction chemotherapy regimens for radiotherapy in patients with locoregionally advanced nasopharyngeal carcinoma.

BACKGROUND AND PURPOSE: The optimal number of cycles of induction chemotherapy (IC) in locoregionally advanced nasopharyngeal carcinoma (LANPC) remains unresolved. This study aimed to quantitatively assess the changes in gross tumor volumes (GTVs) and to select the most optimal number of IC cycles. METHODS: We analyzed 54 patients who received a three-cycle IC before commencing radiotherapy, with the tumor and nodal responses assessed by a CT scan before IC and after each IC cycle. The gross tumor volumes of the nasopharynx primary lesion (GTV_T), involved retropharyngeal lymph node (GTV_RP), and involved cervical lymph node (GTV_N) were contoured on each scan. The volume change following each IC cycle was evaluated with Wilcoxon signed-rank test. The three-dimensional vector displacements of target centers were also calculated and compared. RESULTS: The volume reductions of GTVs following IC varied across different patients and showed different trends for the three GTV types. GTV_T and GTV_RP did not display further volume reduction after two IC cycles, whereas GTV_N showed monotonic volume decreases. For GTV_T and GTV_RP following the three IC cycles, the total volume reduction relative to the initial volume before IC was 12.0%, 22.5%, and 20.1% and 26.0%, 44.1%, and 42.2%, respectively. In contrast, for GTV_N, continuing volume reduction was observed with a total reduction of 25.3%, 43.2%, and 54.7% following the three cycles, and the reductions were all significant. Average displacements of the GTVs were <1.5 mm in all directions; their average three-dimensional displacements were 2.6, 4.0, and 1.7 mm, respectively. Acceptable toxicity was observed in most patients. CONCLUSION: This study supports two cycles of IC before radiotherapy for patients with LANPC if the initial metastatic cervical lymph node volume is not dominating. Otherwise, three cycles of IC is recommended to further reduce the cervical node volume.

Exploration of prognostic biomarkers in head and neck squamous cell carcinoma microenvironment from TCGA database.

Background: Immune checkpoint blockade (ICB) therapies have redefined human cancer treatment, including for head and neck squamous cell carcinoma (HNSCC). However, clinical responses to various immune checkpoint inhibitors are often accompanied by immune-related adverse events (irAEs). Therefore, it is crucial to obtain a comprehensive understanding of the association between different immune tumor microenvironments (TMEs) and the immunotherapeutic response. Methods: The research data were obtained from The Cancer Genome Atlas (TCGA) database. We applied RNA-seq genomic data from tumor biopsies to assess the immune TME in HNSCC. As the TME is a heterogeneous system that is highly associated with HNSCC progression and clinical outcome, we relied on the Estimation of Stromal and Immune cells in Malignant Tumor tissues using Expression data (ESTIMATE) algorithm to calculate immune and stromal scores that were evaluated based on the immune or stromal components in the TME. Then, the Tumor Immune Dysfunction and Exclusion algorithm (TIDE) was used to predict the benefits of ICB to each patient. Finally, we identified specific prognostic tumor-infiltrating immune cells (TIICs) by quantifying the cellular composition of the immune response in HNSCC and its association to survival outcome, using the CIBERSORT algorithm. Results: Utilizing the HNSCC cohort of the TCGA database and TIDE and ESTIMATE algorithm-derived immune scores, we obtained a list of microenvironment-associated lncRNAs that predicted different clinical outcomes in HNSCC patients. We validated these correlations in a different HNSCC cohort available from the TCGA database and provided insight into the prediction of response to ICB therapies in HNSCC. Conclusions: This study confirmed that CD8+ T cells were significantly associated with better survival in HNSCC and verified that the top five significantly mutated genes (SMGs) in the TCGA HNSCC cohort were TP53, TTN, FAT1, CDKN2A, and MUC16. A high level of CD8+ T cells and high immune and stroma scores corresponded to a better survival probability in HNSCC.

Graphene electrochemical transistor incorporated with gel electrolyte for wearable and non-invasive glucose monitoring.

With the rapid development of wearable electronic devices, health monitoring is undergoing a fundamental shift from hospital-centered treatment to patient-centered diagnosis. Solution-gated graphene transistors provide an effective platform for developing high-sensitivity wearable devices due to their unique signal amplification, low energy consumption, and compatibility for miniaturization. However, it is still a major challenge to perform real-time sweat composition monitoring directly on the dry skin surface. In this work, a skin-based flexible gel electrolyte graphene transistor (GEGT) was successfully designed and fabricated for glucose detection, consisting of a gate electrode decorated with Au nanoparticles modified reduced graphene oxide (AuNPs/RGO) nanocomposites and a monolayer graphene channel. Glycerin gel was used to replace the traditional liquid electrolyte, not only could better fit the human skin, but also play the role of fluid collection, providing stable testing conditions for the sensor. Based on the high electron mobility of graphene channel and the excellent electrocatalytic performance of AuNPs/RGO nanocomposites, the constructed GEGT sensor exhibits excellent sensing performance for glucose with good selectivity, low operating voltage (0.5 V), wide detection range (10 nM - 25 mM), and low detection limit (10 nM). The device maintains stable performance after up to 1000 bending cycles with a bending radius of 4 mm. In addition, the GEGT sensor displays good accuracy in sweat detection and sensitive dynamic response during actual wearing, which provides a guarantee for the construction of wearable transistor devices and real-time health tracking.

Ag nanocubes monolayer-modified PDMS as flexible SERS substrates for pesticides sensing.

A new approach is presented to fabricate flexible surface-enhanced Raman scattering (SERS) substrate of Ag nanocubes monolayer-modified polydimethylsiloxane (Ag NCs/PDMS) through a powerful three-phase interface self-assemble method. The morphologies and crystal structures were characterized by scanning electron microscopy and X-ray diffraction. The self-assembled Ag NCs/PDMS substrate exhibited high SERS activity and good signal homogeneity, which was successfully used for quantitative detection of thiram; the detection limit reached 10 ng/mL, and the linear range is 10-1000 ng/mL. Furthermore, the flexible SERS substrates were successfully employed to detect thiram residues on factual apple samples, and trace amount (1 ng/cm2) of thiram residues was detected on apple peels. The excellent SERS detection ability of self-assembled Ag NCs/PDMS substrate indicated that it will play an important role in pesticide detection in the future.

Synthesis of tetraphenylethene-based D-A conjugated molecules with near-infrared AIE features, and their application in photodynamic therapy.

Herein, five aggregation-induced emission (AIE) photosensitizers (PSs) with D-π-A structures are smoothly designed and synthesized through donor and acceptor engineering. The photophysical properties and theoretical calculation results show that the synergistic effect of methoxy substituted tetraphenylethene (MTPE), 3,4-ethylenedioxythiophene can enhance the intramolecular charge transfer effect (ICT), and promote the intersystem crossing (ISC) process of the whole molecule. In these AIE-PSs, the best-performing AIE-PS (MTPE-DT-Py) has bright NIR (740 nm) emission, the highest 1O2 generation efficiency (5.9-fold that of Rose Bengal) and efficient mitochondrial targeting ability. Subsequently, PDT anti-cancer and anti-bacterial experiments indicate that MTPE-DT-Py could obviously target mitochondria and kill breast cancer cells (MCF-7), and selectively inactivate S. aureus (G(+)) under white light irradiation. This work mainly proposes a practical design strategy for high effect AIE-PSs and provides more excellent candidates for fluorescence imaging-guided photodynamic therapy.

High-performance Pt/Ti3C2Tx MXene based graphene electrochemical transistor for selective detection of dopamine.

Accurate measurement of dopamine (DA) is of great significance for human health monitoring and disease prevention. Herein, two-dimensional Ti3C2Tx MXene with high performance was prepared by layer liquid exfoliation method and used for the modification of gate electrode. The glassy carbon electrode (GCE) modified with Pt/Ti3C2Tx was used as the gate, and assembled with monolayer graphene channel to form a complete transistor device. The device combines the amplification effect of transistors, good electrical conductivity of Ti3C2Tx MXene and excellent catalytic properties of Pt nanoparticles, showing a low detection limit (50 nM) and a wide detection concentration range (50 nM-9 mM) of DA. Ti3C2Tx MXene not only provides a large number of attachment sites for the deposition of Pt nanoparticles, but also improves the electrical conductivity and hydrophilicity of the electrode material, thus enhancing the sensitivity of the device and facilitating the penetration of the solution to be measured. In addition, Ti3C2Tx MXene is negatively charged, it has a certain electrostatic adsorption effect on protonated DA and electrostatic repulsion effect on negatively charged interfering substances. As a result, the device exhibits good selectivity, which provides a great application prospect for the construction of DA sensing platform.

Au-PEDOT/rGO nanocomposites functionalized graphene electrochemical transistor for ultra-sensitive detection of acetaminophen in human urine.

A novel graphene electrochemical transistor (GECT) sensor based on Au-poly(3,4-ethylenedioxythiophene)/reduced graphene oxide (Au-PEDOT/rGO) nanocomposites functionalized the gate electrode and monolayer graphene as channel was proposed and constructed for the ultra-sensitive detection of acetaminophen (AP). Au-PEDOT/rGO nanocomposites were synthesized by a simple one-pot method to modify the gate electrode of GECT. With the high catalytic activity of Au nanoparticles, the good conductivity and stability of PEDOT, the large specific surface area and abundant adhesion sites of rGO, the sensitivity and stability of the device for AP detection could be effectively improved. The sensing mechanism of the device was that the electrochemical reactions of the AP on the surface of gate electrode causes the effective gate voltage on the GECT to change, thereby adjusting the carrier concentration and current of the graphene channel. Combined with the excellent catalytic properties of Au-PEDOT/rGO nanocomposites and the high carrier mobility of the graphene channel, the resulting device has remarkable sensing performance for AP, with a detection limit as low as 1 nM and a linear range from 1 nM to 8 mM. In addition, the device has good anti-interference ability and accuracy in the detection of AP in urine samples and tablets, which proved that it could be used to determine AP in human non-invasive and pharmaceutical products. The GECT sensor based on Au-PEDOT/rGO provides an efficient, sensitive and cost-effective sensing platform for AP detection, and is expected to realize in vitro diagnosis of diseases.

Concurrent Apatinib and Brain Radiotherapy in Patients With Brain Metastases From Driver Mutation-negative Non-small-cell Lung Cancer: Study Protocol for an Open-label Randomized Controlled Trial.

Brain radiotherapy (BR) is a well-recognized approach for multiple brain metastases (BMs) from non-small-cell lung cancer (NSCLC). However, the prognosis for these patients remains poor. Apatinib, an antiangiogenic agent targeting vascular endothelial growth factor receptor-2, has shown excellent efficacy in multiple solid tumors. This phase II (WWW. ClinicalTrials.gov Identifier: VEGFR-2 NCT03801200) randomized trial aims to evaluate the efficacy and safety of this combined modality paradigm in patients with BMs from driver mutation-negative NSCLC. This is a multicenter, open-label, randomized controlled clinical trial. A total of 90 eligible patients will be allocated in a 1:1 ratio, to either the experimental group (concurrent apatinib and BR) or the control group (BR alone). The primary endpoint is intracranial progression-free survival. The secondary endpoints include intracranial objective response rate, intracranial disease control rate, intracranial time to progression, overall survival, and occurrence of peritumoral brain edema using standardized measurement. Quality of life and adverse events will also be evaluated. Assessments will be carried out before enrollment (baseline) along with 4 and 12 weeks after radiotherapy, followed by every 12 weeks thereafter and up to 24 months. In summary, the aim of this trial is to demonstrate the clinical efficacy and safety of concurrent BR and apatinib in patients with driver mutation-negative NSCLC with multiple BMs, in efforts to expand management options for this population with poor prognosis.

A novel solution-gated graphene transistor biosensor for ultrasensitive detection of trinucleotide repeats.

A new way to detect GAA trinucleotide repeats (TNRs) based on a solution-gated graphene transistor (SGGT) with high performance was developed. Friedreich's ataxia (FRDA) is a neurodegenerative disease where the first intron of the frataxin (FXN) gene exhibits an extended GAA repeat region. Herein, a SGGT biosensor was constructed based on G-quadruplex DNAzymes and graphene channels. The DNAzymes quantify the captured target DNA by producing a strong catalytic current signal depending on the peroxidase-like activity. The higher the target DNA quantity captured on the gate electrode is, the higher is the concentration of DNAzymes on the surface of the gate electrode, which generates a high catalytic current. Due to the excellent self-amplifying performance of the transistor, the current signal of the SGGT is several hundreds of times larger than in conventional electrochemistry under identical detection conditions. Moreover, a large current signal can be obtained in the case of a low concentration of H2O2 when compared to the case of an enzyme-catalyzed transistor. The SGGT biosensor also exhibits an ultra-low detection limit (32.25 fM), a wide linear range (100 fM-100 nM), and excellent selectivity. The results show that the SGGT biosensor has great potential in the early diagnosis of neurodegenerative diseases.

Non-invasive detection of glucose via a solution-gated graphene transistor.

Owing to its high sensitivity, a solution-gated graphene transistor has rapidly emerged as a cutting edge technology in electrochemical sensing. In this work, composites of gold nanoparticles and reduced graphene oxide were synthesized on a glassy carbon electrode by using the electrodeposition method. A modified glassy carbon electrode was used as the gate electrode and assembled into the solution-gated graphene transistor device along with the graphene channel for a non-invasive glucose detection. The sensing mechanism was based on the change in current in the channel of the device caused by the addition of glucose, of which electro-oxidation on the surface of the gold nanoparticles and reduced graphene oxide led to a change in equivalent gate voltage, and consequently, affected the channel carrier concentration. The self-amplification effect of transistors was utilized in our sensors, which resulted in a detection limit that was 10 times lower than those of conventional electrochemical sensors. Compared to traditional enzymatic transistor sensors, the novel solution-gated graphene transistor nonenzymatic sensors based on gold nanoparticles and reduced graphene oxide demonstrated significant sensing advantages, such as a simple structure, wide linear range from 10 µM to 400 µM and 400 µM to 31 mM, and low detection limit down to 4 µM. The chemicals coexisting in human sweat e.g. sodium chloride, urea, and lactic acid imposed no distinct interference for the glucose detection. Therefore, we achieved a non-invasive detection of glucose in the artificial sweat samples with satisfactory sensing results. This work demonstrates an effective route for non-invasive glucose testing in practical clinical diagnosis by using nonenzymatic, solution-gated graphene transistor devices.

Highly sensitive nitrite sensor based on AuNPs/RGO nanocomposites modified graphene electrochemical transistors.

Detection of nitrite is important for environmental safety and human health, and the development of high-performance sensors for accurate detection of nitrite is highly desirable. Herein, a highly sensitive graphene electrochemical transistor (GECT) nitrite sensor was designed and fabricated for the first time. A single layer of graphene was placed between the source and drain electrodes by the wetting transfer method to act as channel for the transistor. Au nanoparticles modified reduced graphene oxide nanocomposites (AuNPs/RGO) were electrodeposited at the transistor gate to improve its catalytic oxidation performance of nitrite with optimized electrodeposition conditions. The sensing principle was attributed to changes in effective gate voltage applied to GECT induced by electrooxidation of nitrite at gate electrodes. Due to the high carrier mobility of graphene in the channel and the excellent electrocatalytical activity of AuNPs/RGO on the gate, the obtained sensor device exhibited an exceedingly low detection limit (0.1 nM nitrite) and ultra-wide linear range from 0.1 nM to 7 µM and from 7 to 1000 µM, which are comparable or superior to the performance of large-scale instruments (e.g. chromatography, spectrophotometry, and spectrofluorimetry etc.). The GECT device also showed good anti-interference performance toward common interfering ions and stable performances. Nitrite in natural lake water has been proven to be monitored by our devices. Therefore, the present novel GECT sensor could act as a desirable practical platform for highly sensitive detection of nitrite in the food and environmental fields.

A gold electrode modified with a gold-graphene oxide nanocomposite for non-enzymatic sensing of glucose at near-neutral pH values.

A nanocomposite was prepared from gold and graphene oxide via one-step electrodeposition and used to modify the surface of a gold electrode (Au-Gr/GE) that was then applied to non-enzymatic determination of glucose. The effects of deposition time and supporting substrate on the morphology, structure, and electrochemical properties of the nanocomposite were optimized. The morphologies and crystal structures were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results indicate that gold nanoparticles grew on the surface of two-dimensional graphene oxide. The electrocatalytic activity of the modified electrode towards glucose oxidation was evaluated by cyclic voltammetry and amperometric methods at pH 7.4. The Au-Gr/GE, typically operated at a potential of 0.00 V (vs. Ag/AgCl), has a linear response in the 0.05-14 mM and 14-42 mM glucose concentration range, high sensitivity (604 and 267 µA cm-2 mM-1) and a low detection limit (12 µM). The modified GE was applied to quantify glucose in sweat where it exhibited excellent sensitivity and accuracy. Graphical abstract The gold electrode modified with a gold-graphene (Au-Gr/GE) is prepared via a direct electrodeposition. The Au-Gr/GE is used for glucose detection in the neutral solution and it can achieve the effect of non-intrusive detection.

Ratiometric electrochemical biosensor based on Exo III-Assisted recycling amplification for the detection of CAG trinucleotide repeats.

Electrochemical detection of specific nucleic acid sequence remains a hot topic in current bioanalytical research. Here, a novel ratiometric electrochemical biosensor based on Exo III-assisted recycling amplification and graphene-modified electrode was fabricated for quantitative detection of trinucleotide repeat sequence d(CAG)n. The double-signals used are the hairpin DNAs labeled with ferrocene and methylene blue respectively as report DNAs, which can hybridize to target DNA. The hybridized DNA was digested by Exo III, resulting in the release of target and report fragments. The graphene-modified electrode can selectively adsorb the released report fragments to generate double electrochemical signals. The signal ratio (F/M) of ferrocene and methylene blue was used to determine the repeat length accurately: a linear relationship was found between F/M and numbers of repeats (n), F/M = 0.061 n + 1.97, with a correlation coefficient of 0.992. Moreover, any electrochemical signal can be used to test repeat concentration with detection limit of 0.22 pM. Therefore, this novel ratiometric electrochemical biosensor provided a reliable and efficient method for the analysis of d(CAG)n trinucleotide repeat and a potential simplified clinical tool for neurodegenerative diseases.

Silver nanoclusters-assisted triple-amplified biosensor for ultrasensitive methyltransferase activity detection based on AuNPs/ERGO hybrids and hybridization chain reaction.

In the paper, a triple-amplified biosensor was built for the purpose of ultrasensitive methyltransferase (Dam MTase) activity detection and inhibitor screening based on in-situ synthesized silver nanoclusters (AgNCs) as signal probes to provide amplified current signal coupling with gold nanoparticles/electrochemical reduced graphene oxide (AuNPs/ERGO) hybrids and hybridization chain reactions (HCR) amplification strategy. For biosensor preparation, the AuNPs/ERGO hybrids were firstly generated on the electrode surface by electrochemical co-reduction method, then the ds-DNA structures which comprised the specific recognition sequences (5'-G-A-T-C-3') of the Dam MTase and the restrictive endonuclease DpnI were formed on the electrode by the hybridization of the assistant DNA with the capture DNA. The presence of Dam MTase methylated partial ds-DNA structures on the electrode which could be digested by DpnI and could not undergo HCR process. The unmethylated ds-DNA structures underwent HCR process to further hybridize with DNA1 and DNA2 to form ds-DNA superstructures as effective template for AgNCs in-situ synthesis. Oxidation peak current of silver was obtained as signal output for Dam MTase detection. Integrated synthesis and detection in one as well as combined metal nanocluster with DNA superstructures, this biosensor showed a good performance for Dam MTase activity detection with a detection limit of 0.0073 U/mL. Compared with reported biosensor, the designed biosensor showed high sensitivity and had potential in clinical diagnosis as well as inhibitor screening.

A Novel Electrochemical Biosensor Based on a Double-Signal Technique for d(CAG)n Trinucleotide Repeats.

Electrochemical sensors now play an important role in analysis and detection of nucleic acids. In this work, we present a novel double-signal technique for electrochemically measuring the sequence and length of the d(CAG)n repeat. The double-signal technique used an electrochemical molecular beacon (a hairpin DNA labeled with ferrocene), which was directly modified on the surface of a gold electrode, while a reporter probe (a DNA sequence labeled with horseradish peroxidase) was hybridized to the target DNA. First a simple single-signal sensor was characterized in which d(CAG)n repeats were detected using a short reporter DNA strand labeled with horseradish peroxidase. To obtain a reliable signal that was dependent on repeat number, a double-signal biosensor was created in which the single strand capture DNA in single-signal sensor was replaced by an electrochemical molecular beacon labeled with ferrocene. When the hairpin DNA hybridized to the target-reporter DNA complex, it opened, resulting in a decreased ferrocene current. Both electrochemical biosensors exhibited high selectivity and sensitivity with low detection limits of 0.21 and 0.15 pM, respectively, for the detection of d(CAG)n repeats. The double-signal sensor was more accurate for the determination of repeat length, which was measured from the ratio of signals for HRP and ferrocene (H/F). A linear relationship was found between H/F and the number of repeats (n), H/F = 0.1398n + 9.89788, with a correlation coefficient of 0.974. Only 10 nM of target DNA was required for measurements based on the value of H/F in the double-signal technique. These results indicated that this new double-signal electrochemical sensor provided a reliable method for the analysis of CAG trinucleotide repeats.