1,721,053 research outputs found
Comparison among differential Pulse Voltammetry (DPV), and amperometric biosensor and HPLC/DAD Analysis for polyphenol determinations
No full textProtein-templated copper nanoclusters for fluorimetric determination of human serum albumin
Full text linkCopper nanoclusters (CuNCs) are attractive for their unique optical properties, providing sensitive fluorescent detection of several kinds of targets even in complex matrices. Their ability in growing on suitable protein and nucleic acid templates make CuNCs efficient optical reporters to be exploited in bioanalysis. In this work, we report the specific and sensitive determination of human serum albumin (HSA) in human serum (HS) and urine via CuNCs fluorescence. HSA is the most abundant protein in plasma, and plays a key role in the early diagnosis of serious pathological conditions such as albuminuria and albuminemia. Recently, HSA has become clinically central also as a biomarker to assess severity, progression, and prognosis of various cancers. We report the controlled and reproducible growth of CuNCs directly on the target analyte, HSA, which results in a fine dose-dependent fluorescent emission at 405 nm. The protocol is optimized in water, and then applied to serum and urine specimens, without matrix pretreatment. The method linearly responds within the whole concentration of clinical interest, with a sensitivity of 1.8 ± 0.1 × 10-3 g L-1 and 0.62 ± 0.03 × 10-3 g L-1 in serum and urine, respectively, and excellent reproducibility (CVav% ca. 3% for both). The assay is designed to have a single protocol working for both matrices, with recovery of 95% (HS) and 96% (urine). The stability of the fluorescence after CuNCs formation was tested over 3 days, displaying good results (yet higher in urine than in serum)
A Piezoelectric Biosensor as a Direct Affinity Sensor
No full textIt is well - known that the resonant frequency of an oscillating piezoelectric crystal can be affected by a change in mass at the crystal surface. 1 This method can be used as sensor for protein adsorption studies and for direct immunosensing. Up to now these studies have been performed by measuring the frequency in dry state, i.e. with the "dip and dry" technique which is rather cumbersome and time consuming.
Recently we obtained some results with piezoelectric crystals used directly in liquid solutions.
We will discuss a real-time monitoring of (i) adsorption of the human immunoglobulin Ig G (h -Ig G); (ii) the affinity reaction between covalently immobilized antigen (the pesticide 2,4 -D) and specific monoclonal antibodies (Mab anti- 2,4-D) from two different clones (clone F6C 10 and clone E2G2); and, (iii) immunoreactions between immobilized antigen and antibodies performing a competitive assay.
All experiments show how the reaction under study is linked to a mass increase which can be monitored continuously in real time. Direct antigen - antibody interaction can, thus, be studied without any kind of label.
A microprocessor controlled piezoelectric detector as sensor was employed to monitor in real time protein adsorption and immunoreactions using piezoelectric quartz crystals (AT-cut) with basic resonant frequency of 10 MHz. The adsorbed protein was an immunoglobulin (h -Ig G); in the immunosensing a covalent immobilized molecule (the
pesticide 2,4 -D) formed the receptor for the immobilized ligand sample (Mab anti- 2,4- D) in a competitive assay
Colorimetric analysis of the early oxidation of dopamine by hypochlorous acid as preliminary screening tool for chemical determinants of neuronal oxidative stress
No full textThe hypochlorous acid produced by the innate immune system during inflammation characteristic of several neurodegenerative disorders is responsible for the generation of chlorinated byproducts of dopamine in neurons where this neurotransmitter reaches the highest concentration. Therefore, this physiological acid could play a key role in neuronal oxidative stress associated to aberrant dopamine-quinones (DQ) production. Here we report a model study simulating simplified conditions of HOCl reaction with dopamine (DA) in neurons, showing for the first time that DA is immediately converted by HOCl to the yellow colored DQ molecule. The DQ originated from dopamine oxidation results directly proportional to the total amount of the oxidant with excellent reproducibility. Furthermore, following the several evidences of the interplay between cytosolic dopamine and calcium in neurodegenerative disorders, we have verified that the presence of calcium cation influences the dopamine oxidation pathway likely due to the metal chelation by semiquinone formed in the early stage of dopamine oxidation. This experimental approach, based on the isolation of the highly reactive DQ molecule, could be useful for prelaminar investigation of the (putative) determinants of dopamine-poisoning derivatives formation
Polydopamine-based quantitation of albuminuria for the assessment of kidney damage
No full textProteinuria is considered indicative of kidney damage that can be related to various adverse outcomes. Nowadays, there is a huge demand for routine urine screening methods to assess health risks in clinical setting without expensive procedures and long pretreatment of the sample. To address this issue, a polydopamine-based colorimetric assay to determine urinary albumin concentration in real samples is proposed here. The core of this approach relies on the established competitive adsorption of polydopamine film and human serum albumin onto the polystyrene surface of ELISA plates. Herein, we investigated the influence of temperature and the Tris-HCl buffer concentration on the polydopamine film growth. The absorbance of polydopamine film, after 24 h at 25 °C, decreases with the increase of HSA concentration, allowing the selective detection of HSA down to 0.036 ± 0.001 g L−1 in untreated urine. This simple and low-cost bioanalytical assay exhibited very good reproducibility, %CVmean = 2 in human urine, and was superior in terms of analytical performances to some standard methods available on the market, especially in comparison to the Bradford assay, for early screening and assessment of kidney damage. Graphical abstract: [Figure not available: see fulltext.
Sensitive ‘two-steps’ competitive assay for gonadotropin-releasing hormone detection via SPR biosensing and polynorepinephrine-based molecularly imprinted polymer
No full textThe work reports an innovative bioassay for the detection of gonadorelin in urine, a gonadotropin-releasing hormone agonist widely used in fertility medicine and to treat hormonal dysfunctions. Gonadorelin is also a synthetic hormone listed by the World Anti-Doping Agency (WADA) and of interest in anti-doping controls. The main novelty relies on the development of a biocompatible, stable, and low-cost biomimetic receptor alternative to classic antibodies. Starting from norepinephrine monomer, a highly selective and sensitive molecularly imprinted polymer (MIP) was developed and optimized for optical real-time and label-free SPR biosensing. The selectivity has been addressed by testing a series of peptides, from high to low similarity, both in terms of molecular weight and primary sequence. Due to the very low molecular weight of gonadorelin (1182 Da), a ‘two-steps’ competitive assay was developed. Particular attention has been paid to the design of the competitor and its binding affinity constant towards the MIP, being a key step for the success of the competitive strategy. The SPR assay was first optimized in standard conditions and finally applied to untreated urine samples, achieving the sensitivity required by WADA guidelines. The MIP, tested in parallel with a monoclonal antibody, gave comparable results in terms of affinity constants and selectivity towards possible interfering analytes. However, the biomimetic receptor appears clearly superior in terms of sensitivity and reproducibility. This, together with its preparation simplicity, the extremely low-cost of the monomer and its reusability for hundreds of measurements, make polynorepinephrine-based MIPs powerful rivals to immune-based approaches in the near future for similar applications
Polynorepinephrine: state-of-the-art and perspective applications in biosensing and molecular recognition
No full textThe polymerization of norepinephrine, and the properties of the related polymer polynorepinephrine, started to be investigated barely 9 years ago and only few works were produced so far, mainly in materials science and medicine. An unexpectedly low relevance, especially if compared with the interest toward dopamine and polydopamine, differing from norepinephrine only for a hydroxyl group and whose properties were deeply investigated and applied to an impressive number of subject areas. We show here that in some cases, norepinephrine and dopamine monomers can be exchanged without virtually affecting the experimental results. But even more interesting, the choice of norepinephrine can positively influence the properties of the final polymer. In particular, the smoother and more hydrophilic surface of polynorepinephrine may enhance cell adhesion and proliferation, increase the activity of conjugated biomolecules, and induce higher cellular uptake of nanodrugs. Moreover, polynorepinephrine presents an additional anchoring point that can be exploited for further functionalization. Nevertheless, despite its potential for bioconjugation and molecular recognition, polynorepinephrine has not yet been considered in biosensing. Here we report our feelings in terms of perspective use of polynorepinephrine as new functional monomer for biomimetic receptor development by molecular imprinting, with application in affinity biosensing. [Figure not available: see fulltext.]
Electrochemical and piezoelectric DNA biosensors for hybridisation detection
No full textreview on DNA sensing based on electrochemical and piezoelectric sensin
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