198 research outputs found
The potential of molecular imprinting as a biosensing devices for monitoring the CEA cancer biomarker
6th Graduate Student Symposium on Molecular Imprinting6th Graduate Student Symposium on Molecular Imprinting, in Medway School of Pharmacy, Kent, UK, August 27-28, 2015Colorectal cancer is the third most common type of cancer and the major cause of the death throughout the world. Widely known, carcinoembryonic antigen (CEA) is an important tumour marker responsible for clinical diagnosis of 95% of all colon tumors1. The discovery of novel non-invasive biomarkers, as CEA, and its fast determination at low cost is presently required, to enable its use over wide screening programs and applications in point-of-care context, and, thus, its monitoring quite early.
As a novel approach, this work proposes a novel support with molecular imprinted polymer (MIP) for CEA cancer biomarker based on carbon ink matrix linked by sol-gel chemistry on top of conductive glass covered by fluorine-doped tin oxide (FTO glass). In brief, the electrical biosensor was tailored on top of a disposable conductive glass electrode, following a bottom-up approach. The several stages of this process included the chemical modification of a homemade carbon ink layer and the assembly of a MIP or non-imprinted polymer (NIP) layer.
The analytical performance of the obtained devices was followed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Chemical modifications of the surface were characterized using Fourier Transform Infrared (FTIR), and Raman spectroscopy with confocal microscopy. Overall, the MIP/FTO glass-based device displayed linear responses to CEA in EIS assays from 2.5×10-3 µg.mL-1 to 1.25 µg.mL-1 in PBS buffer, with detection limits of 2.5×10-3 µg.mL-1. Successful detection of CEA was, also, achieved in spiked samples of fetal bovine serum.
In conclusion, the devices developed are a promising tool for the monitoring of CEA in a point-of-care applications, due to its detection capability below the normal physiological levels expected for this cancer biomarker, simplicity of manufacture, low-cost and good sensitivity and selectivity
Determination of polyphenols in wines by reaction with 4-aminoantipyrine and photometric flow-injection analysis
A new flow-injection analytical procedure is
proposed for the determination of the total amount of
polyphenols in wines; the method is based on the formation
of a colored complex between 4-aminoantipyrine and
phenols, in the presence of an oxidizing reagent. The oxidizing
agents hexacyanoferrate(III), peroxodisulfate, and
tetroxoiodate(VII) were tested.
Batch trials were first performed to select appropriate
oxidizing agents, pH, and concentration ratios of reagents,
on the basis of their effect on the stability of the colored
complex. Conditions selected as a result of these trials
were implemented in a flow-injection analytical system in
which the influence of injection volume, flow rate, and reaction-
coil length, was evaluated. Under the optimum conditions
the total amount of polyphenols, expressed as gallic
acid, could be determined within a concentration range of
36 to 544 mg L–1, and with a sensitivity of 344 L mol–1 cm–1
and an RSD <1.1%. The reproducibility of analytical
readings was indicative of standard deviations <2%. Interference
from sugars, tartaric acid, ascorbic acid, methanol,
ammonium sulfate, and potassium chloride was negligible.
The proposed system was applied to the determination
of total polyphenols in red wines, and enabled analysis of
approximately 55 samples h–1. Results were usually precise
and accurate; the RSD was <3.9% and relative errors,
by the Folin–Ciocalteu method, <5.1%
Construction and evaluation of cysteine selective electrodes for FIA analysis of pharmaceuticals
A flow injection analysis (FIA) system comprising a cysteine selective
electrode as detection system was developed for determination of this
amino acid in pharmaceuticals. Several electrodes were constructed
for this purpose, having PVC membranes with different ionic
exchangers and mediator solvents. Better working characteristics
were attained with membranes comprising o-nitrophenyl octyl ether
as mediator solvent and a tetraphenylborate based ionic-sensor. Injection of 500 µL standard solutions into an ionic strength adjuster
carrier (3x10-3 M) of barium chloride flowing at 2.4mL min-1,
showed linearity ranges from 5.0x10-5 to 5.0x10-3 M, with
slopes of 76.4±0.6mV decade-1 and R2>0.9935. Slope decreased
significantly under the requirement of a pH adjustment, selected
at 4.5. Interference of several compounds (sodium, potassium,
magnesium, barium, glucose, fructose, and sucrose) was estimated
by potentiometric selectivity coefficients and considered negligible.
Analysis of real samples were performed and considered accurate,
with a relative error to an independent method of +2.7%
Ciprofloxacin-imprinted polymeric receptors as ionophores for potentiometric transduction
A 3D-mirror synthetic receptor for ciprofloxacin host–guest interactions and potentiometric transduction
is presented. The host cavity was shaped on a polymeric surface assembled with methacrylic acid
or 2-vinyl pyridine monomers by radical polymerization. Molecularly imprinted particles were dispersed
in 2-nitrophenyl octyl ether and entrapped in a poly(vinyl chloride) matrix. The sensors exhibited
a near-Nernstian response in steady state evaluations. Slopes and detection limits ranged from 26.8
to 50.0mVdecade−1 and 1.0×10−5 to 2.7×10−5 mol L−1, respectively. Good selectivity was observed
for trimethoprim, enrofloxacin, tetracycline, cysteine, galactose, hydroxylamine, creatinine, ammonium
chloride, sucrose, glucose, sulphamerazine and sulfadiazine. The sensors were successfully applied to
the determination of ciprofloxacin concentrations in fish and in pharmaceuticals. The method presented
offered the advantages of simplicity, accuracy, applicability to colored and turbid samples and automation
feasibility, as well as confirming the use of molecularly imprinted polymers as ionophores for organic
ion recognition in potentiometric transduction
Synthesis of an antibody-like material for the detection of Albumin
6th Graduate Student Symposium on Molecular Imprinting6th Graduate Student Symposium on Molecular Imprinting, Medway School of Pharmacy, Kent, 27-28 de Agosto 2015A novel molecularly imprinted polymer (MIP) is presented for the detection of Albumin,
currently a biomarker of several diseases. The material acted as an antibody for Albumin and
was obtained through a bulk imprinting approach, by electropolymerizing Eriochrome blackT
(EBT) around the target protein
Desenvolvimento de detectores tubulares potenciométricos e de metodologias automáticas de fluxo contínuo com detecção potenciométrica destinados ao controlo químico de produtos farmacêuticos
Dissertação de Doutoramento em Química Analítica apresentada à Faculdade de Farmácia da Universidade do PortoA presente dissertação tem por objectivo estabelecer a simplificação de alguns procedimentos analíticos envolvidos no controlo de qualidade de produtos farmacêuticos, propondo-se para isso sistemas alternativos, baseados na análise por injecção em fluxo com detecção potenciométrica.Neste sentido, descrevem-se, de um modo detalhado, eléctrodos selectivos às formas iónicas da tripelenamina, da prometazina, da cefuroxima e da tetraciclina, construídos com membranas poliméricas de condutor móvel. Numa tentativa de encontrar unidades com boas características de resposta, estabelecem-se várias membranas alternativas, aplicadas em eléctrodos com uma configuração convencional. A avaliação do comportamento destes eléctrodos conduz à selecção da membrana mais adequada a cada caso, com a qual se procede posteriormente à construção de detectores potenciométricos com uma configuração tubular. Estes detectores são então incorporados em sistemas de fluxo, simples e económicos, e as suas características de resposta determinadas.Com as unidades potenciométricas preparadas com a membrana seleccionada, efectuam-se análises discretas e em fluxo de várias especialidades farmacêuticas. Os resultados obtidos são, sempre que possível, comparados com aqueles fornecidos pela execução de metodologias propostas em farmacopeias.Propõe-se ainda a determinação de dopamina em formulações farmacêuticas, baseada na sua reacção de oxidação pelo periodato e recorrendo a um detector tubular selectivo a esta última espécie química. Este eléctrodo constitui também uma nova proposta na literatura e é avaliado na sua configuração convencional. O sistema de análise por injecção em fluxo estabelecido permite realizar a leitura directa da concentração de dopamina e é aplicado à análise de injectáveis. A qualidade dos resultados produzidos é avaliada por comparação com aqueles decorrentes de um procedimento analítico distinto
Backside-surface imprinting as a new strategy to generate specific plastic antibody materials
A backside protein-surface imprinting process is presented herein as a novel way to generate specific synthetic antibody materials. The template is covalently bonded to a carboxylated-PVC supporting film previously cast on gold, let to interact with charged monomers and surrounded next by another thick polymer. This polymer is then covalently attached to a transducing element and the backside of this structure (supporting film plus template) is removed as a regular “tape”. The new sensing layer is exposed after the full template removal, showing a high density of re-binding positions, as evidenced by SEM. To ensure that the templates have been efficiently removed, this re-binding layer was cleaned further with a proteolytic enzyme and solution washout. The final material was named MAPS, as in the back-side reading of SPAM, because it acts as a back-side imprinting of this recent approach. It was able to generate, for the first time, a specific response to a complex biomolecule from a synthetic material. Non-imprinted materials (NIMs) were also produced as blank and were used as a control of the imprinting process. All chemical modifications were followed by electrochemical techniques. This was done on a supporting film and transducing element of both MAPS and NIM. Only the MAPS-based device responded to oxLDL and the sensing layer was insensitive to other serum proteins, such as myoglobin and haemoglobin. Linear behaviour between log(C, μg mL−1) versus charged tranfer resistance (RCT, Ω) was observed by electrochemical impedance spectroscopy (EIS). Calibrations made in Fetal Calf Serum (FCS) were linear from 2.5 to 12.5 μg mL−1 (RCT = 946.12 × log C + 1590.7) with an R-squared of 0.9966. Overall, these were promising results towards the design of materials acting close to the natural antibodies and applied to practical use of clinical interest
Development of paper-based color test-strip for drug detection in aquatic environment: Application to oxytetracycline
The wide use of antibiotics in aquaculture has led to the emergence of resistant microbial species. It should be avoided/minimized by controlling the amount of drug employed in fish farming. For this purpose, the present work proposes test-strip papers aiming at the detection/semi-quantitative determination of organic drugs by visual comparison of color changes, in a similar analytical procedure to that of pH monitoring by universal pH paper. This is done by establishing suitable chemical changes upon cellulose, attributing the paper the ability to react with the organic drug and to produce a color change. Quantitative data is also enabled by taking a picture and applying a suitable mathematical treatment to the color coordinates given by the HSL system used by windows.
As proof of concept, this approach was applied to oxytetracycline (OXY), one of the antibiotics frequently used in aquaculture. A bottom-up modification of paper was established, starting by the reaction of the glucose moieties on the paper with 3-triethoxysilylpropylamine (APTES). The so-formed amine layer allowed binding to a metal ion by coordination chemistry, while the metal ion reacted after with the drug to produce a colored compound. The most suitable metals to carry out such modification were selected by bulk studies, and the several stages of the paper modification were optimized to produce an intense color change against the concentration of the drug. The paper strips were applied to the analysis of spiked environmental water, allowing a quantitative determination for OXY concentrations as low as 30 ng/mL. In general, this work provided a simple, method to screen and discriminate tetracycline drugs, in aquaculture, being a promising tool for local, quick and cheap monitoring of drugs
New and low cost plastic membrane electrode with low detection limits for sulfadimethoxine determination in aquaculture waters
Sulfadimethoxine (SDM) is one of the drugs, often used in the aquaculture sector to prevent the spread of disease in freshwater fish aquaculture. Its spread through the soil and surface water can contribute to an increase in bacterial resistance. It is therefore important to control this product in the environment. This work proposes a simple and low-cost potentiometric device to monitor the levels of SDM in aquaculture waters, thus avoiding its unnecessary release throughout the environment. The device combines a micropipette tip with a PVC membrane selective to SDM, prepared from an appropriate cocktail, and an inner reference solution. The membrane includes 1% of a porphyrin derivative acting as ionophore and a small amount of a lipophilic cationic additive (corresponding to 0.2% in molar ratio). The composition of the inner solution was optimized with regard to the kind and/or concentration of primary ion, chelating agent and/or a specific interfering charged species, in different concentration ranges. Electrodes constructed with inner reference solutions of 1 × 10−8 mol/L SDM and 1 × 10−4 mol/L chromate ion showed the best analytical features. Near-Nernstian response was obtained with slopes of −54.1 mV/decade, an extraordinary detection limit of 7.5 ng/mL (2.4 × 10−8 mol/L) when compared with other electrodes of the same type. The reproducibility, stability and response time are good and even better than those obtained by liquid contact ISEs.
Recovery values of 98.9% were obtained from the analysis of aquaculture water samples
Determination of tartaric acid in wines by FIA with tubular tartrate-selective electrodes
A flow injection analysis (FIA) system comprising
a tartrate- (TAT) selective electrode has been developed
for determination of tartaric acid in wines. Several
electrodes constructed for this purpose had a PVC
membrane with a complex of quaternary ammonium and
TAT as anion exchanger, a phenol derivative as additive,
and a more or less polar mediator solvent. Characterization
of the electrodes showed behavior was best for membranes
with o-nitrophenyl octyl ether as solvent. On injection
of 500 μL into a phosphate buffer carrier (pH = 3.1;
ionic strength 10–2 mol/L) flowing at 3 mL/min, the slope
was 58.06 ± 0.6 with a lower limit of linear range of 5.0 ×
10–4 mol/L TAT and R2 = 0.9989. The interference of several
species, e.g. chloride, bromide, iodide, nitrate, gallic
acid, tannin, sucrose, glucose, fructose, acetate, and citrate,
was evaluated in terms of potentiometric selectivity
coefficients. The Hofmeister series was followed for inorganic
species and the most interfering organic ion was citrate.
When red and white wines were analyzed and the results
compared with those from an independent method
they were found to be accurate, with relative standard deviations
below 5.0%
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