Layer-by-layer assemblies of chitosan/multi-wall carbon nanotubes and glucose oxidase for amperometric glucose biosensor applications

Development of a New Amperometric Biosensor for Measurement of Plasma Galactose Levels

Galactosemia is an inherited disease that occurs as a result of insufficient or no synthesis of some enzymes (GALT, GALK, and GALE) in galactose metabolism. Failure to make an early diagnosis, especially in newborns, can lead to severe clinical and even fatal consequences. The aim of this study is to develop a biosensor for measuring free galactose in plasma. The immobilization components of the developed free galactose biosensor are screen printed carbon electrode (SCPE), Prussian blue (PB), chitosan (CHIT), Nafion (NAF), gold nanoparticle (GNP), and galactose oxidase (GaOX). The CHIT/GaOX/NAF-GNP/GaOX/CHIT-GNP/SCPE-PB electrode showed a sensitive amperometric response to detect galactose. While the surface characterization of the biosensor was performed with cyclic voltammetry and scanning electron microscopy, the optimization and performance characterizations were made by applying an amperometry technique. The amperometric operating potential for the free galactose biosensor was determined as -0.05 V. The linear detection range for the free galactose biosensor is between 0.025 and 10 mM. This range includes galactose levels in plasma of both healthy and patients. The percent coefficient of variation values calculated for intraday and interday repeatability of the developed biosensor are below 10%. The practical use of the biosensor, for which optimization and characterization studies were carried out, was tested in 10 healthy 11 patients with galactosemia, and the results were compared with the colorimetric method. In conclusion, the unique analytical properties and effortless preparation of the new galactose biosensor developed in this study make them serious candidates for point-of-care diagnostic testing.

Chitosan mediated layer-by-layer assembly based graphene oxide decorated surface plasmon resonance biosensor for highly sensitive detection of β-amyloid

Alzheimer's disease (AD), and its consequent effect primarily clinical dementia, Parkinson's disease dementia, etc. currently bring potential avenues for diagnosis centered on identification of beta-amyloid_1-42 (Aβ_1-42). Unfortunately, techniques engaged in AD core biomarker (Aβ_1-42) detection are majorly suffering from poor sensitivity and selectivity. Thus, we fabricated graphene oxide (GO) surface decorated chitosan (CS) mediated layer-by-layer (LbL) assembly based surface plasmon resonance (SPR) biosensor for highly sensitive and selective recognition of Aβ_1-42. Briefly, silver nanoparticles (AgNPs) and GO synthesis were achieved through a greener approach. LbL assembly was designed using CS and polystyrene sulphonate (PSS) on surface of AgNPs (AgNPs-CS-PSS-CS) and then antibodies of Aβ (anti-Aβ) were fixed on LbL assembly (AgNPs-CS-PSS-CS@anti-Aβ). Herein, amine functionality of CS offers a plethora of sites for anti-Aβ antibody immobilization that gives specific direction, high selectivity, and an adequate amount of antibody immobilization. For fabrication, synthesized GO was immobilized on an amine-modified gold-coated sensor chip via carbodiimide chemistry followed by AgNPs-CS-PSS-CS@anti-Aβ immobilization on an activated GO surface. Inimitable features of LbL assembly showed improved selectivity towards Aβ peptide whereas utilization of affinity biotransducer with a combination of plasmonic and non-plasmonic nanomaterial improved sensitivity and selectivity. Consequently, linearity range and limit of detection (LOD) of Aβ_1-42 antigens were found to be 2 fg/mL to 400 ng/mL and 1.21 fg/mL, respectively. Moreover, analysis of Aβ_1-42 in AD-induced rats confirmed the real-time-applicability of the designed SPR biosensor. Hence, GO surface decorated AgNPs-CS-PSS-CS@anti-Aβ mediated SPR biosensor would provide a novel approach for exceptionally sensitive and selective Aβ detection.

Polyaniline nanoflowers grafted onto nanodiamonds via a soft template-guided secondary nucleation process for high-performance glucose sensing

We demonstrated that the electrochemical glucose biosensor fabricated using glucose oxidase-immobilized polyaniline nanoflower-grafted nanodiamonds exhibits superior performances.

High sensitivity chlorogenic acid detection based on multiple layer-by-layer self-assembly films of chitosan and multi-walled carbon nanotubes on a glassy carbon electrode

A chlorogenic acid sensor based on a chitosan (CS) and multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrode (GCE) was fabricated via a layer-by-layer (LBL) self-assembly method.

Modified gold surfaces by 6-(ferrocenyl)hexanethiol/dendrimer/gold nanoparticles as a platform for the mediated biosensing applications

An electrochemical biosensor mediated by using 6-(Ferrocenyl) hexanethiol (FcSH) was fabricated by construction of gold nanoparticles (AuNPs) on the surface of polyamidoamine dendrimer (PAMAM) modified gold electrode. Glucose oxidase (GOx) was used as a model enzyme and was immobilized onto the gold surface forming a self assembled monolayer via FcSH and cysteamine. Cyclic voltammetry and amperometry were used for the characterization of electrochemical response towards glucose substrate. Following the optimization of medium pH, enzyme loading, AuNP and FcSH amount, the linear range for the glucose was studied and found as 1.0 to 5.0mM with the detection limit (LOD) of 0.6mM according to S/N=3. Finally, the proposed Au/AuNP/(FcSH+Cyst)/PAMAM/GOx biosensor was successfully applied for the glucose analysis in beverages, and the results were compared with those obtained by HPLC.

STUDY ON THE POTENTIOMETRIC GLUCOSE BIOSENSOR BASED ON THE SnO2/ITO/PET

A potentiometric glucose biosensor based on a SnO2/ITO/PET substrate is presented in this study. The sensing membrane of SnO2 is coated on ITO/PET substrate by utilized radio frequency (RF)-sputtering method of semiconductor fabrication. The potentiometric glucose biosensor is established on an FET-type pH sensor. Therein, the glucose oxidase (GOD) and chitosan/multi-wall carbon nano-tubes (chitosan/MWCNTs) are immobilized by 3-glycidoxypropyl trimethoxysilane (3-GPTS). Finally, the drift characteristic and calibration curve of the potentiometric pH sensor and potentiometric glucose biosensor is discussed in the following article. We find the nonideal effect of device reduced significantly, due to the coating of SnO2 thin film.

Clay-chitosan nanobrick walls: completely renewable gas barrier and flame-retardant nanocoatings

Thin films prepared via a layer-by-layer (LbL) assembly of renewable materials exhibit exceptional oxygen barrier and flame-retardant properties. Positively charged chitosan (CH), at two different pH levels (pH 3 and pH 6), was paired with anionic montmorillonite (MMT) clay nanoplatelets. Thin-film assemblies prepared with CH at high pH are thicker, because if the low polymer charge density. A 30-bilayer (CH pH 6-MMT) nanocoating (~100 nm thick) reduces the oxygen permeability of a 0.5-mm-thick polylactic acid film by four orders of magnitude. This same coating system completely stops the melting of a flexible polyurethane foam, when exposed to direct flame from a butane torch, with just 10 bilayers (~30 nm thick). Cone calorimetry confirms that this coated foam exhibited a reduced peak heat-release rate, by as much as 52%, relative to the uncoated control. These environmentally benign nanocoatings could prove beneficial for new types of food packaging or a replacement for environmentally persistent antiflammable compounds.

The application of carbon nanotubes in target drug delivery systems for cancer therapies

Among all cancer treatment options, chemotherapy continues to play a major role in killing free cancer cells and removing undetectable tumor micro-focuses. Although chemotherapies are successful in some cases, systemic toxicity may develop at the same time due to lack of selectivity of the drugs for cancer tissues and cells, which often leads to the failure of chemotherapies. Obviously, the therapeutic effects will be revolutionarily improved if human can deliver the anticancer drugs with high selectivity to cancer cells or cancer tissues. This selective delivery of the drugs has been called target treatment. To realize target treatment, the first step of the strategies is to build up effective target drug delivery systems. Generally speaking, such a system is often made up of the carriers and drugs, of which the carriers play the roles of target delivery. An ideal carrier for target drug delivery systems should have three pre-requisites for their functions: (1) they themselves have target effects; (2) they have sufficiently strong adsorptive effects for anticancer drugs to ensure they can transport the drugs to the effect-relevant sites; and (3) they can release the drugs from them in the effect-relevant sites, and only in this way can the treatment effects develop. The transporting capabilities of carbon nanotubes combined with appropriate surface modifications and their unique physicochemical properties show great promise to meet the three pre-requisites. Here, we review the progress in the study on the application of carbon nanotubes as target carriers in drug delivery systems for cancer therapies.

Carbon nanotubes in cancer theragnosis

Carbon nanotubes as a unique and novel class of nanomaterials have shown considerable promise in cancer therapy and diagnosis amidst the myriad of nanocarriers. The presence of a large surface area enables the engineering of the surface of nanotubes, thus making them biocompatible, and large benefits can be harnessed from them. Together with their ability to encapsulate small molecules, stacking interactions and conjugation, nanotubes have improved the profile of anticancer agents. The propensity to absorb the body transparent NIR radiation also envisages photothermal and photoacoustic therapy using nanotubes. This article sheds light on the role of carbon nanotubes in cancer therapy and diagnosis based on recent findings.