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Analytica Chimica Acta (v.777, #)
Chemical surface modifications for the development of silicon-based label-free integrated optical (IO) biosensors: A review by María-José Bañuls; Rosa Puchades; Ángel Maquieira (pp. 1-16).
Display Omitted► IO devices made with silicon based technologies are at the core of biosensors development. ► Surface biofunctionalization is crucial to reach competitive performance. ► Main achievements reached in real sample biosensing are critically discussed.Increasing interest has been paid to label-free biosensors in recent years. Among them, refractive index (RI) optical biosensors enable high density and the chip-scale integration of optical components. This makes them more appealing to help develop lab-on-a-chip devices. Today, many RI integrated optical (IO) devices are made using silicon-based materials. A key issue in their development is the biofunctionalization of sensing surfaces because they provide a specific, sensitive response to the analyte of interest. This review critically discusses the biofunctionalization procedures, assay formats and characterization techniques employed in setting up IO biosensors. In addition, it provides the most relevant results obtained from using these devices for real sample biosensing. Finally, an overview of the most promising future developments in the fields of chemical surface modification and capture agent attachment for IO biosensors follows.
Keywords: Optical biosensors; Surface biofunctionalization; Label free; Integrated biosensors
Three-dimensional voltammetry assisted by parametric signal fitting: A new perspective for the electrochemical evaluation of metal binding in the presence of electrodic adsorption by José Manuel Díaz-Cruz; Arístides Alberich; Cristina Ariño; Miquel Esteban (pp. 17-24).
•3D-voltammograms are obtained by integration of multiple chronoamperograms.•A new chemometric method is proposed for the analysis of 3D-voltammograms.•It fits time-dependent parametric waves and peaks to the signals along the matrix.•It allows the separation of adsorptive and diffusive contributions to the current.•Augmented matrices allow the analysis of 3D-voltammetric titrations.A new perspective of three-dimensional voltammetry is given for the study of metal complexation in the presence of adsorption phenomena and, eventually, when the electrochemical reversibility of the processes decreases. For this purpose, 3D-voltammograms are obtained as usual, i.e., by combination of chronoamperograms measured at different potential steps, but they are analysed by the new methodology of parametric signal fitting (PSF), which uses the full data matrix to fit a five-parameter equation to every component. The parametric signals can be time-dependent peaks or waves and the optimised parameters inform about the concentrations in both dissolved and adsorbed phases. The analysis can be carried out on both individual and augmented matrices. The preliminary tests on the well-known Cd(II)-glutathione system yield promising results and encourage the combination of 3D-voltammetry and PSF as a complementary tool for the study of metal complexation in complicated systems.
Keywords: 3D-voltammetry; Parametric signal fitting; Cd(II)-glutathione; Electrodic adsorption; Multivariate curve resolution; Non-linear data
Use of potentiometric detection in (ultra) high performance liquid chromatography and modelling with adsorption/desorption binding kinetics by D. Daems; G. Van Camp; M. Fernandez; Y. Guisez; E. Prinsen; L.J. Nagels (pp. 25-31).
Display Omitted•The first use of a potentiometric detector in UPLC is described.•The potentiometric detector is also used in HPLC.•Alkaloids were sensitively determined.•A model is given that describes how adsorption/desorption kinetics determines the detector characteristics.•Binding kinetics can be performed with the detector, in Flow injection analysis.Observation of a potentiometric sensor's response behaviour after injection in flow injection analysis at different concentrations allowed studying “on” and “off” kinetics of the analyte's adsorption/diffusion behaviour. The alkaloid metergoline was mostly used as an example. kon and koff rate constant values were measured, and the association constant Kass, and ΔG values of the analyte–surface interaction were calculated with an adsorption-based model which proved to be fully applicable. kon increased by decreasing the sensor dimensions, while koff was unaffected by miniaturization. Increasing acetonitrile concentrations in the running buffer increased koff, while kon was unaffected. The experimentally determined ΔG values of the analyte–surface interaction showed a linear relation to the response of the sensor, in mV. This knowledge was applied to optimize the potentiometric detection of plant alkaloids in (U)HPLC. Sub-micromolar detection limits were obtained with the potentiometric detector/(U)HPLC combination. This is the first time that the response rates and the response itself can be modelled accurately for coated wire potentiometric sensors, and it is the first application of a potentiometric detector in UPLC.
Keywords: Potentiometry; Sensorgram; FIA; Kinetics; (U)HPLC, Alkaloids
Determination of neonicotinoid insecticides residues in eels using subcritical water extraction and ultra-performance liquid chromatography–tandem mass spectrometry by Zhiming Xiao; Yunxia Yang; Yang Li; Xia Fan; Shuangyang Ding (pp. 32-40).
•A novel SWE technique for the determination of neonicotinoids in eels is presented.•Extraction parameters have been optimized along with the validation procedures.•The proposed method is accurate, sensitive, and environmental-friendly.•It was successfully applied for the analysis of neonicotinoids in real world samples.A rapid, sensitive, and environmental-friendly multi-residue method has been developed for the simultaneous determination of seven neonicotinoid insecticides (dinotefuran, nitenpyram, thiamethoxam, imidacloprid, clothianidin, acetamiprid, and thiacloprid) residues in eel samples. Subcritical water extraction was investigated as a novel and alternative technology for the extraction of neonicotinoids from eel matrices and the results were compared with the conventional ultrasonic and shaking extraction. The target compounds were identified and quantitatively determined by ultra-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC–MS/MS) operated in multiple reaction monitoring mode. Under the current optimized chromatographic conditions, each LC run was completed in 5min. Average recoveries of the seven analytes from fortified samples ranged between 84.6% and 102.0%, with relative standard deviations (RSD) lower than 10.8%. The limits of detection (LODs) and quantification (LOQs) for neonicotinoids were in the ranges of 0.12–0.36μgkg−1 and 0.42–1.12μgkg−1, respectively. The proposed method is fast, sensitive, easy to perform, water-based thus more environmentally acceptable, making it applicable for high-throughput monitoring of insecticides residues in aquatic products.
Keywords: Neonicotinoid; Eel; Subcritical water extraction; Ultra-performance liquid chromatography; Tandem mass spectrometry
Characterisation of the flavour profile from Graciano Vitis vinifera wine variety by a novel dual stir bar sorptive extraction methodology coupled to thermal desorption and gas chromatography–mass spectrometry by Maria Arbulu; M. Carmen Sampedro; Alicia Sanchez-Ortega; Alberto Gómez-Caballero; Nora Unceta; M. Aranzazu Goicolea; Ramón J. Barrio (pp. 41-48).
Display Omitted•A novel dual-SBSE and thermal desorption GC–MS method is established.•The flavour metabolome of the Graciano Vitis vinifera wine variety is characterised.•The deconvolution software AMDIS has been used in metabolomic studies.•The method permits the characterisation of 205 metabolites.•Six of these metabolites have never been previously reported in wine.The aim of this work was to develop a new analytical technique for the study of the organoleptic compounds (flavour profile) of the Graciano Vitis vinifera wine variety. The cv. Graciano is a singular variety of red grapes with its origins in La Rioja and Navarra (northern Spain). This variety transfers an intense red colour, aroma and high acidity to musts and provides greater longevity and, consequently, a better capacity for ageing wine. A new dual-stir bar sorptive extraction approach coupled with thermal desorption (TD) and GC–MS has been used to extract the volatile and semivolatile compounds. In this extraction step, the optimal values for the experimental variables were obtained through the Response Surface Methodology (RSM). Full scan chromatogram data were evaluated with two deconvolution software tools, and the results were compared. The volatile and semivolatile components were identified with an MS match ≥80%. As a result, the flavour metabolome of the Graciano Vitis vinifera wine variety was obtained, and 205 metabolites were identified using different databases. These metabolites were grouped into esters, acids, alcohols, nitrogen compounds, furans, lactones, ketones, aldehydes, phenols, terpenes, norisoprenoids, sulphur compounds, acetals and pyrans. The majority of the metabolites observed had already been reported in the literature; however, this work also identified new, previously unreported metabolites in red wines, which may be characteristic of the Graciano variety.
Keywords: Flavour-metabolome; Wine; Graciano Vitis vinifera; Stir bar sorptive extraction
Rapid screening of bioactive compounds from natural products by integrating 5-channel parallel chromatography coupled with on-line mass spectrometry and microplate based assays by Yufeng Zhang; Shun Xiao; Lijuan Sun; Zhiwei Ge; Fengkai Fang; Wen Zhang; Yi Wang; Yiyu Cheng (pp. 49-56).
•A 5-channel parallel chromatography coupled with mass spectrometry method was established to screen active compounds.•The proposed approach has satisfied sensitivity and stability.•Three case studies of this approach identified several active compounds.•Agelasine B and (−)-agelasine D from marine sponge were found to have anti-tumor effect.A high throughput method was developed for rapid screening and identification of bioactive compounds from traditional Chinese medicine, marine products and other natural products. The system, integrated with five-channel chromatographic separation and dual UV–MS detection, is compatible with in vitro 96-well microplate based bioassays. The stability and applicability of the proposed method was validated by testing radical scavenging capability of a mixture of seven known compounds (rutin, dihydroquercetin, salvianolic acid A, salvianolic acid B, glycyrrhizic acid, rubescensin A and tangeretin). Moreover, the proposed method was successfully applied to the crude extracts of traditional Chinese medicine and a marine sponge from which 12 bioactive compounds were screened and characterized based on their anti-oxidative or anti-tumor activities. In particular, two diterpenoid derivatives, agelasine B and (−)-agelasine D, were identified for the first time as anti-tumor compounds from the sponge Agelas mauritiana, showing a considerable activity toward MCF-7 cells (IC50 values of 7.84±0.65 and 10.48±0.84μM, respectively). Our findings suggested that the integrated system of 5-channel parallel chromatography coupled with on-line mass spectrometry and microplate based assays can be a versatile and high efficient approach for the discovery of active compounds from natural products.
Keywords: Natural products; Parallel chromatography; Rapid identification; Traditional Chinese medicine; Targeted screening
Surface-imprinted core–shell Au nanoparticles for selective detection of bisphenol A based on surface-enhanced Raman scattering by Jin-Qun Xue; Da-Wei Li; Lu-Lu Qu; Yi-Tao Long (pp. 57-62).
•The molecularly imprinted polymer capped core–shell AuNPs (MIP-ir-AuNPs) were fabricated as a specific functional SERS substrate.•MIP-ir-AuNPs could be utilized in rapid and selective detection of BPA.•MIP-ir-AuNPs displayed good capability for determination of BPA in real samples.Surface-imprinted core–shell Au nanoparticles (AuNPs) were explored for the highly selective detection of bisphenol A (BPA) by surface-enhanced Raman scattering (SERS). A triethoxysilane-template complex (BPA-Si) was synthesized and then utilized to fabricate a molecularly imprinted polymer (MIP) layer on the AuNPs via a sol–gel process. The imprinted BPA molecules were removed by a simple thermal treatment to generated the imprint-removed material, MIP-ir-AuNPs, with the desired recognition sites that could selectively rebind the BPA molecules. The morphological and polymeric characteristics of MIP-ir-AuNPs were investigated by transmission electron microscopy and Fourier-transform infrared spectroscopy. The results demonstrated that the MIP-ir-AuNPs were fabricated with a 2nm MIP shell layer within which abundant amine groups were generated. The rebinding kinetics study showed that the MIP-ir-AuNPs could reach the equilibrium adsorption for BPA within 10min owning to the advantage of ultrathin core–shell nanostructure. Moreover, a linear relationship between SERS intensity and the concentration of BPA on the MIP-ir-AuNPs was observed in the range of 0.5–22.8mgL−1, with a detection limit of 0.12mgL−1 (blank±3×s.d.). When applied to SERS detection, the developed surface-imprinted core–shell MIP-ir-AuNPs could recognize BPA and prevent interference from the structural analogues such as hexafluorobisphenol A (BPAF) and diethylstilbestrol (DES). These results revealed that the proposed method displayed significant potential utility in rapid and selective detection of BPA in real samples.
Keywords: Surface-imprinted; Core–shell; Nanoparticles; Surface-enhanced Raman scattering; Bisphenol A
Molecularly imprinted polyaniline-polyvinyl sulphonic acid composite based sensor for para-nitrophenol detection by Abhijit Chandra Roy; V.S. Nisha; Chetna Dhand; Md. Azahar Ali; B.D. Malhotra (pp. 63-71).
•Biomimetic para-nitrophenol (PNP) imprinted sensor is used to detect PNP.•The PVSA doped polyaniline shows high conductivity.•The sensor shows excellent sensitivity, 18 times reusability and higher stability.•PANI-PVSA composite shows increased stability of the sensor.We report results of the studies relating to the fabrication and characterization of a conducting polymer based molecularly imprinted para-nitrophenol (PNP) sensor. A water pollutant, para-nitrophenol is electrochemically imprinted with polyvinyl sulphonic acid (PVSA) doped polyaniline onto indium tin oxide (ITO) glass substrate. This PNP imprinted electrode (PNPI-PANI-PVSA/ITO) prepared via chronopotentiometric polymerization and over-oxidation is characterized by Fourier transform infra-red spectroscopy (FT-IR), UV–visible (UV–vis) spectroscopy, contact angle (CA), scanning electron microscopy (SEM), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) studies. The response studies of PNPI-PANI-PVSA/ITO electrode carried out using DPV reveal a lower detection limit of 1×10−3mM, improved sensitivity as 1.5×10−3AmM−1 and stability of 45 days. The PNPI-PANI-PVSA/ITO electrode shows good precision with relative standard deviation of 2.1% and good reproducibility with standard deviation of 3.78%.
Keywords: Molecular imprinting; Conducting polymer; Polyaniline; Para-nitrophenol; Polyvinyl sulphonic acid
Application of surface plasmon resonance spectroscopy for adsorption studies of different types of components on poly(dimethylsiloxane) by Attila Gaspar; Frank A. Gomez (pp. 72-77).
•Surface plasmon resonance spectroscopy was used for adsorption studies on poly(dimethylsiloxane) (PDMS) surfaces.•The technique can be used to monitor the kinetics of adsorption and desorption of different molecules.•Large, water-soluble polymer-like materials like proteins generally irreversibly adsorb to PDMS.•We propose that the extent of adsorption of the components on PDMS is related more to size than to hydrophobicity.Surface plasmon resonance (SPR) spectroscopy is utilized to study in real-time and, by label-free means, the reversible and quasi-irreversible adsorption of small ionic or neutral molecules, pharmaceuticals, and proteins on poly(dimethylsiloxane) (PDMS) surfaces. The SPR sensor is covered with 0.2% (w/v) PDMS in octane. During the timescale of a typical lab-on-a-chip analysis or an electrophoretic separation, it was found that small neutral components containing a hydrophobic part do not adsorb or absorb onto PDMS, while larger, water-soluble polymer-like materials like proteins generally irreversibly adsorb to PDMS. The technique can be used to monitor the kinetics of adsorption and desorption of the molecules. For the non-specific adsorption of teicoplanin to PDMS, a Langmuir-like adsorption isotherm was obtained ( Kd=32±2μmolL−1).
Keywords: Surface plasmon resonance; Poly(dimethylsiloxane); Adsorption; MicrochipAbbreviations; SPR; surface plasmon resonance; PDMS; poly(dimethylsiloxane); CE; capillary electrophoresis; EOF; electroosmotic flow; SDS; sodium dodecyl sulfate
Monitoring of potential cytotoxic and inhibitory effects of titanium dioxide using on-line and non-invasive cell-based impedance spectroscopy by Keith B. Male; Mahsa Hamzeh; Johnny Montes; Alfred C.W. Leung; John H.T. Luong (pp. 78-85).
•Probing cytotoxicity of TiO2 nanoparticles by cell-based impedance spectroscopy.•Real-time cell mobility and spreading serves as an indicator of cytotoxicity.•The cytotoxicity of TiO2 particles is cell-line and particle size dependent.•The crystal structure of is another major contributing factor to cytotoxicity.Titanium dioxide (TiO2) nanoparticles (NPs) with different sizes and structures were probed for plausible cytotoxicity using electric cell-substrate impedance sensing (ECIS), a non-invasive and on-line procedure for continuous monitoring of cytotoxicity. For insect cells ( Spodoptera frugiperda Sf9), the ECIS50 values, i.e., the concentration required to achieve 50% inhibition of the response, differed depending on the size and shape of the TiO2 nanostructure. The lowest ECIS50 value (158ppm) was observed for the needle shaped rutile TiO2 (10nm×40nm, 15.5nm nominal particle size), followed by 211ppm for P-25 (34.1nm, 80% anatase and 20% rutile), 302ppm for MTI5 (5.9nm, 99% anatase) and 417ppm for Hombitan LW-S bulk TiO2 (169.5nm, 99% anatase). Exposure of TiO2 NPs to UV light at 254nm or 365nm exhibited no significant effect on the ECIS50 value due to the aggregation of TiO2 NPs with diminishing photocatalytic activities. Chinese hamster lung fibroblast V79 cells, exhibited no significant cytotoxicity/inhibition up to 400ppm with P25, MTI5 and bulk TiO2. However, a noticeable inhibitory effect was observed (ECIS50 value of 251ppm) with rutile TiO2 as cell spreading on the electrode surface was prevented
Keywords: Titanium dioxide; Cytotoxicity; Inhibition; Nanoparticles; Nanomaterials; Impedance biosensing
Laser-photophoretic migration and fractionation of human blood cells by Hideaki Monjushiro; Yuko Tanahashi; Hitoshi Watarai (pp. 86-90).
•RBCs were migrated faster than WBCs and blood pellets by laser photophoresis.•Photophoretic efficiency of RBC and WBC was simulated by the Mie scattering theory.•Spontaneous orientation of RBC parallel to the migration direction was elucidated.•Laser photophoretic separation of RBC and WBC was possible in a tip flow system.Laser photophoretic migration behavior of human blood cells in saline solution was investigated under the irradiation of Nd:YAG laser beam (532nm) in the absence and the presence of the flow in a fused silica capillary. Red blood cells (RBC) were migrated faster than white blood cells (WBC) and blood pellets to the direction of propagation of laser light. The observed photophoretic velocity of RBC was about 11 times faster than those of others. This was understood from the larger photophoretic efficiency of RBC than that of WBC, which was simulated based on the Mie scattering theory. Furthermore, it was found that, during the photophoretic migration, RBCs spontaneously orientated parallel to the migration direction so as to reduce the drag force. Finally, it was demonstrated that RBC and WBC were separated in a micro-channel flow system by the laser photophoresis.
Keywords: Photophoresis; Red blood cell; Migration; Microchip; Fractionation; Mie theory