Development of colorimetric cholesterol detection kit using TPU nanofibre/cellulose acetate membrane

In this study, the authors report a simple fabrication of thermoplastic polyurethane (TPU) nanofibres‐based kit for cholesterol detection. TPU is a polymer that is highly elastic, resistant to microorganisms, abrasion and compatible with blood; thus, making it a natural selection as an immobilisation matrix for cholesterol oxidase (ChOx) enzyme. The nanofibre was fabricated by electrospinning process and was characterised using scanning electron microscopy and Fourier transform‐infrared spectroscopy. ChOx was covalently immobilised on TPU nanofibre and cholesterol level/concentration was visually found using 4‐aminoantipyrine, a dye that reacts with H₂ O₂ produced from the oxidation of cholesterol by ChOx and changes colour from yellow to red. The efficacy of the nanofibre to act as a detecting substrate was compared with cellulose acetate (CA) membrane, a well‐documented enzyme immobilisation matrix. The optimisation of enzyme concentration and dye quantity were performed using standard ChOx spectrophotometric assay and the same was used in CA membrane and TPU nanofibre. The ChOx immobilised nanofibre showed good linear range from 2 to 10 mM with a lower detection limit of 2 mM and was highly stable compared to that of CA membrane. The enzyme immobilised nanofibre was further validated in serum samples.Inspec keywords: colorimetry, nanofibres, biomembranes, biosensors, nanosensors, nanofabrication, polymer fibres, elasticity, nanomechanics, biomechanics, blood, nanomedicine, biomedical equipment, enzymes, molecular biophysics, molecular configurations, biochemistry, abrasion, biomedical materials, electrospinning, scanning electron microscopy, Fourier transform infrared spectra, dyes, oxidation, spectrophotometryOther keywords: colorimetric cholesterol detection kit, TPU nanofibre‐cellulose acetate membrane, thermoplastic polyurethane nanofibres‐based kit, highly elastic polymer, microorganisms, abrasion, blood compatibility, natural selection, immobilisation matrix, cholesterol oxidase ChOx enzyme, electrospinning, scanning electron microscopy, Fourier transform‐infrared spectroscopy, TPU nanofibre, cholesterol level‐concentration, 4‐aminoantipyrine, H₂ O₂ production, oxidation, cellulose acetate membrane, enzyme immobilisation matrix, enzyme concentration, optimisation, dye quantity, standard ChOx spectrophotometric assay, enzyme immobilised nanofibre, serum samples     

Metal oxide–chitosan based nanocomposite for cholesterol biosensor

Metal oxide [cerium oxide (NanoCeO₂)]–chitosan (CH) nanocomposite film has been fabricated onto indium-tin-oxide (ITO) coated glass plate to immobilize cholesterol oxidase (ChOx) via physiosorption for cholesterol detection. Electrochemical studies reveal that the presence of NanoCeO₂ in CH–CeO₂ nanocomposite results in increased electroactive surface area for ChOx loading resulting in enhanced electron transport between ChOx and electrode. The ChOx/CH–NanoCeO₂/ITO bioelectrode exhibits interesting characteristics such as detection range of 10–400 mg/dL, detection limit of 5 mg/dL, response time of 10 s, low K_m value of 3.5 mg/dL and value of regression coefficient of 0.994.     

Sol-gel derived cerium-oxide-silicon-oxide nanocomposite for cypermethrin detection

Cerium oxide (CeO₂) nanoparticles have been self-assembled onto sol-gel derived silicon-oxide (SiO₂) film fabricated onto indium tin oxide (ITO) coated glass plate. These SiO₂-CeO₂ nanocomposite films have been used to immobilize the double stranded calf thymus deoxy ribose nucleic acid (dsCT-DNA) by physical adsorption to detect cypermethrin (CM). Both CeO₂-SiO₂/ITO electrode and dsCT-DNA/CeO₂-SiO₂/ITO bioelectrodes have been characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microsopy (SEM) and differential pulse voltammetry (DPV) to confirm the formation of CeO₂-SiO₂ nanocomposite and binding of dsCT-DNA with CeO₂-SiO₂ nanocomposite. Electrochemical response studies of dsCT-DNA/CeO₂-SiO₂/ITO bioelectrode carried out as a function of CM concentration using DPV technique exhibit detection limit up to 0.0025 ppm with response time of 30 s.     

Review of the recent developments in cellulose nanocomposite processing

This review addresses the recent developments of the processing of cellulose nanocomposites, focusing on the most used techniques, including solution casting, melt-processing of thermoplastic cellulose nanocomposites and resin impregnation of cellulose nanopapers using thermoset resins. Important techniques, such as partially dissolved cellulose nanocomposites, nanocomposite foams reinforced with nanocellulose, as well as long continuous fibers or filaments, are also addressed. It is shown how the research on cellulose nanocomposites has rapidly increased during the last 10 years, and manufacturing techniques have been developed from simple casting to these more sophisticated methods. To produce cellulose nanocomposites for commercial use, the processing of these materials must be developed from laboratory to industrially viable methods.     

Biomimetic design of a bacterial cellulose/hydroxyapatite nanocomposite for bone healing applications

This study describes the design and synthesis of bacterial cellulose/hydroxyapatite nanocomposites for bone healing applications using a biomimetic approach. Bacterial cellulose (BC) with various surface morphologies (pellicles and tubes) was negatively charged by the adsorption of carboxymethyl cellulose (CMC) to initiate nucleation of calcium-deficient hydroxyapatite (cdHAp). The cdHAp was grown in vitro via dynamic simulated body fluid (SBF) treatments over a one week period. Characterization of the mineralized samples was done with X-ray Photoelectron Spectroscopy (XPS) and Field Emission Scanning Electron Microscopy (FESEM) with Energy Dispersive Spectroscopy (EDS). The amount of cdHAp observed varied among different samples. XPS demonstrated that the atomic presence of calcium and phosphorus ranged from 0.44 at.% to 7.71 at.% Ca and 0.27 at.% to 11.18 at.% P. The Ca/P overall ratio ranged from 1.22 to 1.92. FESEM images showed that the cdHAp crystal size increased with increasing nanocellulose fibril density. To determine the viability of the scaffolds in vitro, the morphology and differentiation of osteoprogenitor cells was analyzed using fluorescence microscopy and alkaline phosphatase gene expression. The presence of cdHAp crystals on BC surfaces resulted in increased cell attachment.     

Chitosan nanocomposite films incorporating cellulose nanocrystals and grape pomace extracts

Chitosan nanocomposite films incorporating grape pomace extract (GPE), either Cabernet Franc (CF; a red variety) or Viognier (a white variety), and cellulose nanocrystal (CNC) were prepared using a solvent casting method. Mechanical properties, water vapour permeability, color and opacity, crystalline structure, thermal properties, total phenolic content, and antioxidant activity of the films were characterized. Incorporating CNC alone significantly (P < .05) increased tensile strength of the films and decreased their percent elongation at break and water vapour permeability. Grape pomace extract had an opposite effect on mechanical properties by decreasing tensile strength but increasing percent elongation at break. Film color was mainly influenced by the presence and type of GPE. Films containing CF extract exhibited the darkest appearance with increased reddish and bluish hues. Addition of CNC significantly increased film opacity and the alignment of chitosan chains, while the effect of GPE was not significant. Thermal analysis showed that chitosan and CNC were partially miscible and that the addition of CNC did not significantly change decomposition temperature of the films. Incorporation of GPE significantly (P < .05) increase total phenolic content and antioxidant activity. Films containing CF had higher DPPH? radical scavenging capacity than their counterparts with Viognier. Film incorporating both CNC and CF shows greater potential for food packaging application because of a combination of improved physical properties and high antioxidant activity.     

Flexible cellulose and ZnO hybrid nanocomposite and its UV sensing characteristics

Abstract

This paper reports the synthesis and UV sensing characteristics of a cellulose and ZnO hybrid nanocomposite (CEZOHN) prepared by exploiting the synergetic effects of ZnO functionality and the renewability of cellulose. Vertically aligned ZnO nanorods were grown well on a flexible cellulose film by direct ZnO seeding and hydrothermal growing processes. The ZnO nanorods have the wurtzite structure and an aspect ratio of 9 ~ 11. Photoresponse of the prepared CEZOHN was evaluated by measuring photocurrent under UV illumination. CEZOHN shows bi-directional, linear and fast photoresponse as a function of UV intensity. Electrode materials, light sources, repeatability, durability and flexibility of the prepared CEZOHN were tested and the photocurrent generation mechanism is discussed. The silver nanowire coating used for electrodes on CEZOHN is compatible with a transparent UV sensor. The prepared CEZOHN is flexible, transparent and biocompatible, and hence can be used for flexible and wearable UV sensors.     

A low-cost method for producing high-performance nanocomposite thin-films made from silica and CNTs on cellulose substrates

We show that thin films of silica loaded with 22 wt% of carbon nanotubes (CNTs) can be deposited on cellulose substrate via the sol–gel route by a well-controlled process. The high loadings are obtained by airbrush spraying of a diluted sol solution (which contained a much smaller concentration of CNTs) followed by drying at 200 °C. The films are nearly continuous despite the fibrous structure of the substrate. The high degree of connectivity of the stranded structure of the CNTs yields a specific electrical conductivity of 3 × 10³ Ω⁻¹ m⁻¹. In contrast, films made with high loadings of carbon black have poor electrical conductivity. Results from mechanical tensile tests of samples are also reported. This economical method of producing CNT dispersed thin films could find application in catalysis, as electrodes in fuel cells and batteries, and in sensor technologies.     

An electronic nose for amine detection based on polymer/SWNT-COOH nanocomposite

An electronic nose (e-nose) system based on polymer/carboxylic-functionalized single-walled carbon nanotubes (SWNT-COOH) was developed for sensing various volatile amines. The SWNT-COOH dispersed in the matrix of different polymers; namely, polyvinyl chloride (PVC), cumene terminated polystyrene-co-maleic anhydride (cumene-PSMA), poly(styrenecomaleic acid) partial isobutyl/methyl mixed ester (PSE), and polyvinylpyrrolidon (PVP), were deposited on interdigitated gold electrodes to make the gas sensors. The response of these sensors to volatile amines was studied by both static and dynamic flow measurements. It was found that all sensors exhibited behaviors corresponding to Plateau-Bretano-Stevens law (R2 = 0.81 to 0.99) as the response to volatile amines. Real-world application was demonstrated by applying this e-nose to monitor the odor of sun-dried snakeskin gourami that was pre-processed by salting-preservation. This electronic nose can discriminate sun-dried fish odors with different stored days using a simple pattern recognition based on the principal component analysis (PCA).     

Synthesis and characterisation of TiO2 nanofibre/cellulose acetate nanocomposite ultrafiltration membrane

ABSTRACT

Nanofibres of TiO₂ were synthesised by hydrothermal routine. Cellulose acetate/TiO₂ nanofibre composite membranes were synthesised via blending TiO₂ nanofibre in cellulose acetate solutions in 1-methyl-2-pyrrolidone. In order to study the effect of addition of nanofibre, membranes with various composition were synthesised, first by keeping cellulose acetate to 1-methyl-2-pyrrolidone ratio constant and second by decreasing cellulose acetate concentration with increasing addition of TiO₂ nanofibre. The membranes were characterised using scanning electron microscope and X-ray diffraction. Hydrophilicity of the membranes was evaluated in terms of contact angle measurements and water uptake study. Permeation characteristics were determined in terms of pure water flux and bovine serum albumin rejection. Antifouling property was studied in terms of flux recovery after rejection. Remarkable improvement in membrane flux and antifouling properties is achieved by the addition of TiO₂ nanofibres.     

Reduced graphene oxide/ZnO nanocomposite modified electrode for the detection of tetracycline

Journal of Materials Science - In this work, rGO-ZnO (reduced graphene oxide–zinc oxide) nanocomposite was prepared and used for modification of GC (glassy carbon) surface in order to obtain...     

Novel nanocomposite concept based on cross-linking of hyperbranched polymers in reactive cellulose nanopaper templates

Cellulosic fibers offer interesting possibilities for good interfacial adhesion due to the high density of hydroxyl groups at the surface. In the present study, the potential of a new nanocomposite concept is investigated, where a porous cellulose nanofiber network is impregnated with a solution of reactive hyperbranched polyester. The polymer is chemically cross-linked to form a solid matrix. The resulting nanocomposite structure is unique. The matrix surrounds a tough nanopaper structure consisting of approximately 20 nm diameter nanofibers with an average interfiber distance of only about 6 nm. The cross-linked polymer matrix shows strongly altered characteristics when it is cross-linked in the confined space within the nanofiber network, including dramatically increased T_g, and this must be due to covalent matrix-nanofiber linkages.     

Structure and thermal properties of poly(lactic acid)/cellulose whiskers nanocomposite materials

The goal of this work was to produce nanocomposites based on poly(lactic acid) (PLA) and cellulose nanowhiskers (CNW). The CNW were treated with either tert-butanol or a surfactant in order to find a system that would show flow birefringence in chloroform. The nanocomposites were prepared by incorporating 5 wt% of the different CNW into a PLA matrix using solution casting. Field emission scanning electron microscopy showed that untreated whiskers formed flakes, while tert-butanol treated whiskers formed loose networks during freeze drying. The surfactant treated whiskers showed flow birefringence in chloroform and transmission electron microscopy showed that these whiskers produced a well dispersed nanocomposite. Thermogravimetric analysis indicated that both whiskers and composite materials were thermally stable in the region between 25 °C and 220 °C. The dynamic mechanical thermal analysis showed that both the untreated and the tert-butanol treated whiskers were able to improve the storage modulus of PLA at higher temperatures and a 20 °C shift in the tan δ peak was recorded for the tert-butanol treated whiskers.     

Barium titanate as a filler for improving the dielectric property of cyanoethyl cellulose/antimony tin oxide nanocomposite films

CEC/ATO and CEC/BTO/ATO nanocomposite films were fabricated by introducing barium titanate (BTO) and antimony tin oxide (ATO) in cyanoethyl cellulose (CEC) via simple solution blending technique. The morphology, microstructure, thermal stability, mechanical, optical and dielectric properties of the nanocomposite films were investigated. The results indicated that CEC/BTO/ATO nanocomposite films possessed better dielectric property and mechanical property compared with CEC/ATO nanocomposite films. This could be ascribed to the homogeneous dispersion of ATO in CEC matrix due to the introduction of BTO. The nanocomposite films with only ATO nanoparticles had a certain optical transmissibility. In addition, all the nanocomposite films possessed better thermal stability than CEC polymer.     

Au nanoparticles decorated graphene/nickel foam nanocomposite for sensitive detection of hydrogen peroxide

The Au nanoparticles decorated graphene(AuNPs@Gr)/nickel foam(Gr/NiF) nanocomposite(AuNPs@Gr/NiF) was prepared by chemical vapor deposition followed by electrophoretic deposition of AuNPs on Gr/NiF. The morphology, microstructure and sensing performance of the as-prepared AuNPs@Gr/NiF nanocomposite were characterized and measured, respectively by scanning electron microscope, transmission electron microscope, ultraviolet visible spectroscopy and chemical workstation. The asprepared AuNPs@Gr/NiF nanocomposite was used as the electrode to construct a chemical sensor for the detection of hydrogen peroxide(H_2O_2). The results showed that the AuNPs distributed homogenously and stably on the surface of Gr/NiF. The chemical sensor exhibits a sensitive and selective performance to the detection of H_2O_2.     

A facile approach to prepare regenerated cellulose/graphene nanoplatelets nanocomposite using room-temperature ionic liquid

This study presents the preparation of regenerated cellulose (RC)/graphene nanoplatelets (GNPs) nanocomposites via room temperature ionic liquid, 1-ethyl-3-methylimidazolium acetate (EMIMAc) using solution casting method. The thermal stability, gas permeability, water absorption and mechanical properties of the films were studied. The synthesized nanocomposite films were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The T20 decomposition temperature of regenerated cellulose improved with the addition of graphene nanoplatelets up to 5 wt%. The tensile strength and Young's modulus of RC films improved by 34 and 56%, respectively with the addition of 3 wt% GNPs. The nanocomposite films exhibited improved oxygen and carbon dioxide gas barrier properties and water absorption resistance compared to RC. XRD and SEM results showed good interaction between RC and GNPs and well dispersion of graphene nanoplatelets in regenerated cellulose. The FTIR spectra showed that the addition of GNPs in RC did not result in any noticeable change in its chemical structure.     

Development and evaluation of ZnO-Fe2O3 based nanocomposite sensors for butanol detection

Olfactory sensing of specific volatile organic compounds released by bacterial pathogens is one of the unique ways for determining microbial contamination in packaged food products. This study reports the development and evaluation of zinc oxide-iron oxide (ZnO-Fe2O3) nanocomposite sensors to detect low concentrations of butanol, one of the VOCs specific to Salmonella contamination in packaged beef, at low operating temperature (100 degrees C). The ZnO-Fe2O3 sensor was developed using modified Sol-gel method on an interdigitated alumina substrate. The sensor thin film characterization confirmed a uniform layer of ZnO-Fe2O3 thin film formation with ZnO nanorods of 100 nm height. Also, ZnO-Fe2O3 nanocomposite sensor demonstrated repeatable responses and good sensitivity to butanol with an estimated lower detection limit of about 26 ppm at 100 degrees C.     

Cross-linked nanocomposite hydrogels based on cellulose nanocrystals and PVA: Mechanical properties and creep recovery

Cellulose nanocrystal (CNC) reinforced poly(vinyl alcohol) (PVA) hydrogels with a water content of ∼92% were successfully prepared with glutaraldehyde (GA) as a cross-linker. The effects of the CNC content on the thermal stability, swelling ratio and mechanical and viscoelastic properties of the cross-linked hydrogels were investigated. The compressive strength at 60% strain for the hydrogels with 1 wt% CNCs increased by 303%, from 17.5 kPa to 53 kPa. The creep results showed that the addition of CNCs decreased the creep elasticity due to molecular chain restriction. The almost complete strain recovery (∼97%) after fixed load removal for 15 min was observed from the hydrogels with CNCs, compared with 92% strain recovery of the neat cross-linked PVA hydrogels. The incorporation of CNCs did not affect the swelling ratio and thermal stability of the hydrogels. These results suggest the cross-linked CNC-PVA hydrogels have potential for use in biomedical and tissue engineering applications.