Peptide nanotube functionalized molecularly imprinted polydopamine based single-use sensor for impedimetric detection of malathion.

In the present study, a peptide nanotube functionalized polydopamine (p-Dop) based molecularly imprinted (MIP) sensor system was constructed, characterized, and studied for the impedimetric sensing of an organophosphorus pesticide, malathion (MLT). Electropolymerization in the presence of a template (MLT) was utilized as a convenient and effective strategy to generate imprinted p-Dop films on peptide nanotubes (PNTs) modified graphite electrodes (PGEs). Upon the removal of template, the adsorption of MLT on the specific cavities formed in the MIP film was tracked using electrochemical impedance spectroscopy (EIS). To attain optimal sensor response, experimental conditions, such as film thickness, analyte/functional monomer ratio, and desorption/adsorption time, were analyzed. The obtained MIP(p-Dop)-PNT-PGE sensor exhibited high sensitivity for electrochemical MLT analysis with a wide dynamic detection range of 13 pg mL-1 - 1.3 µg mL-1 and a LOD of 1.39 pg mL-1. The combination of a bio-inspired p-Dop-based MIP with the EIS technique allowed excellent sensitivity and selectivity toward MLT sensing which also yielded high recoveries in real samples. The success of this research strategy in real samples revealed its potential for various future environmental applications.

Wearable soft electrochemical microfluidic device integrated with iontophoresis for sweat biosensing.

A soft and flexible wearable sweat epidermal microfluidic device capable of simultaneously stimulating, collecting, and electrochemically analyzing sweat is demonstrated. The device represents the first system integrating an iontophoretic pilocarpine delivery system around the inlet channels of epidermal polydimethylsiloxane (PDMS) microfluidic device for sweat collection and analysis. The freshly generated sweat is naturally pumped into the fluidic inlet without the need of exercising. Soft skin-mounted systems, incorporating non-invasive, on-demand sweat sampling/analysis interfaces for tracking target biomarkers, are in urgent need. Existing skin conformal microfluidic-based sensors for continuous monitoring of target sweat biomarkers rely on assays during intense physical exercising. This work demonstrates the first example of combining sweat stimulation, through transdermal pilocarpine delivery, with sample collection through a microfluidic channel for real-time electrochemical monitoring of sweat glucose, in a fully integrated soft and flexible multiplexed device which eliminates the need of exercising. The on-body operational performance and layout of the device were optimized considering the fluid dynamics and evaluated for detecting sweat glucose in several volunteers. Furthermore, the microfluidic monitoring device was integrated with a real-time wireless data transmission system using a flexible electronic board PCB conformal with the body. The new microfluidic platform paves the way to real-time non-invasive monitoring of biomarkers in stimulated sweat samples for diverse healthcare and wellness applications.

Non-Enzymatic Electrochemical Sensing of Malathion Pesticide in Tomato and Apple Samples Based on Gold Nanoparticles-Chitosan-Ionic Liquid Hybrid Nanocomposite.

Malathion (MLT) is an organophosphorous type pesticide and having seriously high toxicity and electrochemical platforms for rapid, simple, inexpensive and sensitive determination of pesticides is still a special concern. This paper describes a simple preparation of a composite film consisting of ionic liquid (IL), chitosan (CS) and electrochemically synthesized gold nanoparticles (AuNPs) on single use pencil graphite electrodes (PGEs). The microscopic and electrochemical characterization of AuNP-CS-IL/PGE was studied using scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. This fabricated surface was then explored for the first time as a sensing matrix for the non-enzymatic electrochemical sensing of malathion by cyclic voltammetry and square wave voltammetry measurements. The proposed AuNP-CS-IL/PGE showed excellent characteristics and possessed remarkable affinity for malathion. The voltammetric current response exhibited two linear dynamic ranges, 0.89-5.94 nM and 5.94-44.6 nM reflecting two binding sites, with a detection limit of 0.68 nM. The method was applied in real sample analysis of apple and tomato. The results demonstrate the feasibility of AuNP-CS-IL-modified electrodes for simple, fast, ultrasensitive and inexpensive detection of MLT.

Fabrication of a polyaniline ultramicroelectrode via a self assembled monolayer modified gold electrode.

Herein, we report a simple and inexpensive way for the fabrication of an ultramicroelectrode and present its characterization by electrochemical techniques. The fabrication of polyaniline UME involves only two steps: modification of a gold (Au) electrode by self assembled monolayers (SAM) and then electrodeposition of polyaniline film on this thiol-coated Au electrode by using cyclic voltammetry and constant potential electrolysis methods. Two types of self-assembled monolayers (4-mercapto-1-butanol, MB, and 11-mercaptoundecanoic acid, MUA) were used, respectively, to see the effect of chain length on microelectrode formation. Microelectrode fabrication and utility of the surface was investigated by cyclic voltammetric measurements in a redox probe. The thus prepared polyaniline microelectrode was then used for DNA immobilization. Discrimination between double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) was obtained with enhanced electrochemical signals compared to a polyaniline-coated Au electrode. Different modifications on the electrode surfaces were examined using scanning electron microscopy (SEM).

Peptide nanotubes/self-assembled polydopamine molecularly imprinted biochip for the impedimetric detection of human Interleukin-6.

In the study, an impedimetric biochip was designed with molecularly imprinted polydopamine (MIP(pDa)) on peptide nanotube (PNT) functionalized screen printed electrodes (SPEs) and adopted first time as a support matrix to construct the electrochemical sensor for the determination of interleukin 6 (IL-6). IL-6, which is one of the important cytokines, was used as a template molecule during the self-assembly polymerization strategy of dopamine. Dopamine acted as a functional monomer and self-polymerization occurred without any initiator, enzyme, or crosslinker. Impedimetric, spectrometric, and morphological characterization data demonstrated that MIP(pDa)/PNT provided satisfactory performance for the impedimetric diagnosis of IL-6. Analyzed IL-6 biomolecules could be detected in the range of 1-200 pg/mL due to the good correlation between the redox pair response and the logarithm of IL-6 concentration. The MIP(pDa)/PNT electrode was capable of selective binding for IL-6 with high recovery values in urine sample. The designed methodology allowed us to detect IL-6 with an effective, facile and inexpensive route that was easy to fabricate and scale-up. The coupling of MIP(pDa)/PNT with SPEs and the use of the impedimetric detection approach holds great potential to provide a new avenue for clinical diagnostics because in these systems small volumes of samples can be analyzed without the need for any pre-processing steps in short times.

Polydopamine nanoparticles-assisted impedimetric sensor towards label-free lung cancer cell detection.

Polydopamine nanoparticles (PDA NPs), among nature-inspired building materials, show special functions for biomedical systems and exploring PDA derived nanostructures for future developments is a fast growing field. Herein, we demonstrated the first evaluation of the PDA NPs for the electrochemical determination of lung cancer cells. In the presented study, PDA NPs were synthesized in a mild and cost-effective fashion by self-polymerization of dopamine in an alkaline environment. The structural and chemical characterizations clearly demonstrated the formation of PDA NPs with controllable size (130 nm), hence applied as a suitable material to functionalize the pencil graphite electrode (PGE) surface to construct a cytosensing nanoprobe. The ability of the developed sensor (PDA NPs/PGE) for label-free electrochemical A-549 lung cancer cells detection was investigated. The designed PDA NPs based cytosensor exhibited good biocompatibility and sensitivity for impedimetric diagnosis of A-549 cells in a wide linear range (1.0 × 102-1.0 × 105 cells mL-1) with low detection limit (25 cells mL-1). Furthermore, the developed bioassay has great potential as liquid biopsy for early cancer detection.

Folic acid conjugated Prussian blue nanoparticles: Synthesis, physicochemical characterization and targeted cancer cell sensing.

In the study, folic acid doped Prussian blue nanoparticles (FA-PB NPs) for theranostic applications were synthesized for the first time. Folic acid was chosen for maintaining nanoparticle stability and also to increase its binding affinity especially for cancer cells. Multifunctional PB NPs were fabricated by one route co-precipitation method to synthesize biocompatible NPs without any further process. Then, FA was doped on the surface of PB NPs. The characterization studies demonstrated that the FA-PB NPs modified sensor surface had large surface area with biocompatible and hydrophilic properties where cancer cells can easily bind. The FA-PB NPs were used for the modification of pencil graphite electrode (PGE) for electrochemical detection of colon cancer cells (DLD-1). Electrochemical impedimetric diagnosis was based on the specific interaction between FA groups on the nanoparticles and FA receptors overexpressed on cancer cells. The voltammetric and impedimetric results showed that the FA-PB NPs based electrode had good sensing performance for the immobilized DLD-1 cells.

Acoustic Nanomotors for Detection of Human Papillomavirus-Associated Head and Neck Cancer.

OBJECTIVE: Human papillomavirus (HPV)-associated oropharyngeal cancer (OPC) is a lethal disease with increasing incidence; however, technologies for early detection are limited. Nanomotors are synthetic nanostructures that can be powered by different mechanisms and functionalized for specific applications, such as biosensing. The objective of this investigation was to demonstrate an in vitro proof of concept for a novel nanomotor-based cancer detection approach toward in vivo detection of HPV-OPC. STUDY DESIGN: In vitro cell line incubated with ultrasound-propelled nanomotors. SETTING: Basic science and engineering laboratories. SUBJECTS AND METHODS: Ultrasound-powered gold nanowire nanomotors were functionalized with graphene oxide and dye-labeled single-stranded DNA for the specific intracellular detection of HPV16 E6 mRNA transcripts. Nanomotors were incubated with HPV-positive or HPV-negative human OPC cells under static conditions or with an applied ultrasound field for 15 minutes. The resulting intracellular fluorescence was assessed with fluorescence microscopy and analysis software. RESULTS: Nanomotors incubated with RNA extracted from HPV-positive OPC cells resulted in 60.7% of maximal fluorescence recovery, while incubation with RNA extracted from HPV-negative cells produced negligible fluorescence. Nanomotor incubation with intact HPV-negative cells produced minimal fluorescence (0.01 au), while incubation with HPV-positive cells produced a detectable signal (0.43 au) under static conditions and had 2.3-times greater intensity when powered with ultrasound. CONCLUSION: Acoustically powered nanomotors can successfully identify HPV16 E6 mRNA transcripts extracellularly and within intact cells. This work represents the first step toward a novel, practical approach to address the challenge of visually detecting HPV-OPC in real time.

Eyeglasses-based tear biosensing system: Non-invasive detection of alcohol, vitamins and glucose.

We report on a wearable tear bioelectronic platform, integrating a microfluidic electrochemical detector into an eyeglasses nose-bridge pad, for non-invasive monitoring of key tear biomarkers. The alcohol-oxidase (AOx) biosensing fluidic system allowed real-time tear collection and direct alcohol measurements in stimulated tears, leading to the first wearable platform for tear alcohol monitoring. Placed outside the eye region this fully wearable tear-sensing platform addresses drawbacks of sensor systems involving direct contact with the eye as the contact lenses platform. Integrating the wireless electronic circuitry into the eyeglasses frame thus yielded a fully portable, convenient-to-use fashionable sensing device. The tear alcohol sensing concept was demonstrated for monitoring of alcohol intake in human subjects over multiple drinking courses, displaying good correlation to parallel BAC measurements. We also demonstrate for the first time the ability to monitor tear glucose outside the eye and the utility of wearable devices for monitoring vitamin nutrients in connection to enzymatic flow detector and rapid voltammetric scanning, respectively. These developments pave the way to build an effective eyeglasses system capable of chemical tear analysis.

Peptide nanoparticles (PNPs) modified disposable platform for sensitive electrochemical cytosensing of DLD-1 cancer cells.

A novel diphenylalaninamid (FFA) based peptide nanoparticles (PNPs) modified pencil graphite electrodes (PGEs) for construction of electrochemical cytosensor was demonstrated for the first time in this study. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed the spherical nanostructure of the synthesized FFA based PNPs while attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectra provided information about the structure and conformation of proteins in their structure. Self-assembly of PNPs on PGE surface and adhesion of DLD-1 cancer cells on this surface was also characterized by electrochemical measurements. PNP/PGEs acted as a sensitive platform for simple and rapid quantification of low concentration of DLD-1 cancer cells in early diagnosis using the electrochemical impedance method (EIS). The offered cytosensor demonstrated outstanding performance for the detection of DLD-1 cells by the EIS method. The impedance of electronic transduction was associated with the amount of the immobilized cells ranging from 2 × 102 to 2.0 × 105 cellsmL-1 with a limit of detection of 100 cellsmL-1. The efficient performance of the cytosensor was attributed to the well-defined nanostructure and biocompability of PNPs on the substrate.

Electrochemical behavior and voltammetric detection of fenitrothion based on a pencil graphite electrode modified with reduced graphene oxide (RGO)/poly(E)-1-(4-((4-(phenylamino)phenyl)diazenyl)phenyl)ethanone (DPA) composite film.

A combination of a novel synthesized azo dye (E)-1-(4-((4-(phenylamino)phenyl)diazenyl) phenyl)ethanone and reduced graphene oxide was used to electrochemically modify the surface of a pencil graphite electrode. The surfaces of the modified electrodes were characterized using electrochemical techniques (cyclic voltammetry and electrochemical impedance spectroscopy) and spectroscopic techniques (scanning electron microscopy and attenuated total reflectance). This azo dye/reduced graphene oxide modified electrode was applied first time for the electrochemical detection of an organophosphorus pesticide, fenitrothion. The modified pencil graphite electrode displayed excellent performance for the detection of fenitrothion. Cyclic voltammetry was used to study the dependence of the scan rate on the peak current and peak potential and to determine the kinetic parameters for fenitrothion. Square wave voltammetry was used to determine the effect of pH on the peak potential and for the sensitive and selective detection of fenitrothion using the modified electrode. Satisfactory results were obtained with the proposed sensor for the analysis of FT in tomato samples.