This work outlines a simple fabricated microneedle electrode for sensitive and real sample monitoring of plant polyphenolics. The electrode was fabricated by layer-by-layer assembly (LBL) with nanocomposite of carbon nanotubes (CNT) and cellulose nanocrystals (CNC) as the first layer, followed by polyaniline (PANI), and finally, the 3-(glycidyloxypropyl)trimethoxysilane (GOPS) layer as the binding agent. The microneedle electrodes were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy. The developed microneedle electrodes were successfully applied for the capacitive detection of gallic acid (GA) and chlorogenic acid (CA) as polyphenol model compounds. The microneedle electrode was also used to quantify polyphenols in orange juice. The electrochemical capacitance responses were linearly proportional to the concentrations of GA and CA in the range of 0.1-87.23 μg/mL for GA and 0.1-78.01 μg/mL for CA. The calculated detection limits (LOD) for GA and CA were found to be 0.29 ± 0.2 μg/mL and 0.34 ± 0.2 μg/mL respectively. As minimally invasive technology, microneedle electrodes were found to be promising for successful in situ screening of antioxidants in different fruit matrices. The microneedle electrodes were also applied to the depth profiling of antioxidant content in fruit samples.
We report herewith an inexpensive flexible dual target electrochemical sensor for simultaneous detection of pH and cortisol in human sweat. The sensor was fabricated by printing layer by layer (LbL) on a conductive microneedle polydimethylsiloxane (PDMS) flexible substrate. The dual sensor integrates two detection chambers comprising polyaniline (PANi) and cortisol imprinted poly (glycidylmethacrylate-co ethylene glycol dimethacrylate) (poly (GMA-co-EGDMA)). The dual wearable sensor rapidly (< 1 min) responded linearly to pH in the range of 3-9, while the cortisol sensor chamber had a linear range of 0-100 ng/mL. The cortisol sensing region had an excellent limit of detection (LOD) of 1.4 ± 0.3 ng/mL, with intra-batch reproducibility of 2.4% relative standard deviation (%RSD). The inter-batch precision (%RSD for three different sensors) was determined to be 4.7%. Demonstrating excellent stability and reusability, a single patch of cortisol sensor was used for 15 times over a 30-day period, with minimal change in response. The dual analyte wearable sensors were effective for detection of pH and cortisol in real human sweat. K E Y W O R D Scapacitive sweat sensors, dual electrochemical sensor for simultaneous pH and cortisol detection, microneedle biomimetic flexible e-skin sensors, PANi-based pH sensors, poly (GMA-co-EDMA) cortisol imprinted polymer film 1This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Background. Osteosarcoma (OS) is one of the most malignant bone tumors and has a high metastatic rate. Increasing research has demonstrated the vital roles of long noncoding RNAs (lncRNAs) in human cancers, including OS. LncRNA LINC00662 has been revealed to act as an oncogene involved in multiple tumor progression. This study aimed to investigate the expression pattern, function, and regulatory mechanism of LINC00662 in OS. Methods. Patients who underwent OS surgery were involved in this study. Experiments including RT-qPCR, MTT, western blot, FISH, RNA pull-down, luciferase reporter, colony formation, transwell invasion and migration, and sphere formation assay were performed to investigate the regulatory role of LINC00662 in OS. Results. In the present study, our findings demonstrated the upregulation of LINC00662 expression in OS tissues and cells, and high expression of LINC00662 predicted a poor clinical prognosis of patients’ iNOS. Through a series of in vivo assays, LINC00662 knockdown suppressed OS cell proliferation, invasion, migration, and stemness property maintenance. Further mechanistical investigations indicated that LINC00662 functioned as a competing endogenous RNA (ceRNA) for sponging microRNA-16-5p (miR-16-5p) to upregulate the expression of IP receptor type 1 (ITPR1) in OS cells. Restoration assays validated the involvement of ITPR1 in LINC00662-mediated regulation of cell functions in OS. Conclusion. LINC00662 exerts oncogenic functions in OS by targeting the miR-16-5p/ITPR1 axis.
A wearable, textile-based molecularly imprinted polymer (MIP) electrochemical sensor for cortisol detection in human sweat has been demonstrated. The wearable cortisol sensor was fabricated via layer-by-layer assembly (LbL) on a flexible cotton textile substrate coated with a conductive nanoporous carbon nanotube/cellulose nanocrystal (CNT/CNC) composite suspension, conductive polyaniline (PANI), and a selective cortisol-imprinted poly(glycidylmethacrylate-co-ethylene glycol dimethacrylate) (poly(GMA-co-EGDMA)) decorated with gold nanoparticles (AuNPs), or plated with gold. The cortisol sensor rapidly (<2 min) responded to 9.8–49.5 ng/mL of cortisol, with an average relative standard deviation (%RSD) of 6.4% across the dynamic range, indicating excellent precision. The cortisol sensor yielded an excellent limit of detection (LOD) of 8.00 ng/mL, which is within the typical physiological levels in human sweat. A single cortisol sensor patch could be reused 15 times over a 30-day period with no loss in performance, attesting to excellent reusability. The cortisol sensor patch was successfully verified for use in quantification of cortisol levels in human sweat.
This work presents a multipurpose and multilayered stainless steel microneedle sensor for the in situ redox potential monitoring in food and drink samples, termed MN redox sensor. The MN redox sensor was fabricated by layer-by-layer (LbL) approach. The in-tube multilayer coating comprised carbon nanotubes (CNTs)/cellulose nanocrystals (CNCs) as the first layer, polyaniline (PANI) as the second layer, and the ferrocyanide redox couple as the third layer. Using cyclic voltammetry (CV) as a transduction method, the MN redox sensor showed facile electron transfer for probing both electrical capacitance and redox potential, useful for both analyte specific and bulk quantification of redox species in various food and drink samples. The bulk redox species were quantified based on the anodic/cathodic redox peak shifts (Ea/Ec) on the voltammograms resulting from the presence of redox-active species. The MN redox sensor was applied to detect selected redox species including ascorbic acid, H2O2, and putrescine, with capacitive limits of detection (LOD) of 49.9, 17.8, and 263 ng/mL for each species, respectively. For the bulk determination of redox species, the MN redox sensor displayed LOD of 5.27 × 103, 55.4, and 25.8 ng/mL in ascorbic acid, H2O2, and putrescine equivalents, respectively. The sensor exhibited reproducibility of ~ 1.8% relative standard deviation (%RSD). The MN redox sensor was successfully employed for the detection of fish spoilage and antioxidant quantification in king mushroom and brewed coffee samples, thereby justifying its potential for food quality and food safety applications. Lastly, the portability, reusability, rapid sampling time, and capability of in situ analysis of food and drink samples makes it amenable for real-time sensing applications.
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