102,039 research outputs found
Electrochemical Fingerprint of Arsenic (III) by Using Hybrid Nanocomposite-Based Platforms
No full textArsenic, one of the most abundant mineral and also one to the most toxic compounds. Due to its high toxicity sensitive analytical methods are highly important, taking into account that the admitted level is in the range of mu g L-1. A novel and easy to use platform for As(III) detection from water samples is proposed, based on gold and platinum bi metallic nanoparticles and a conductive polymer (polyaniline). The electrochemical detection was achieved after optimization of cathodic pre-concentration and stripping parameters by square wave anodic stripping voltammetry at modified screen-printed carbon-based electrochemical cells, proving its applicability for disposable and cost-effective in situ analysis of arsenic
Beta-lactoglobulin Electrochemical Detection Based with an Innovative Platform Based on Composite Polymer
No full textIn this work, we present a new electrochemical disposable platform based on poly(aniline-co-anthranilic acid) (PANI/PAA) composite polymer coupled with an aptamer for sensitive detection of beta-lactoglobulin. Firstly, PANI/PAA film was electrodeposited on the graphite screen-printed electrode surface by cyclic voltammetry. The co-polymer modified electrode was then employed as platform for the covalent immobilization of an amino-modified aptamer. Various beta-lactoglobulin solutions, with a fixed amount of biotinylated oligonucleotide complementary sequence, were dropped onto the aptasensor surface. A streptavidin-alkaline phosphatase conjugate was then employed to trace the affinity reaction. After the addition of 1-naphthyl-phosphate enzymatic substrate, 1-naphthol electroactive product was detected by differential pulse voltammetry. A decrease in the signal was obtained when the target concentration was increased, in according to a signal-off approach. After optimization of key experimental parameters, a dose-response curve was obtained between 0.01-1.0 mu g mL(-1) beta-lactoglobulin concentration range. The limit of detection of 0.053 mu g L-1 was obtained. Milk samples spiked with beta-lactoglobulin were analyzed
New micro-and nano-technologies for biosensor development
No full textRecent advances in micro- and nanotechnology have produced a number of new materials which exhibit exceptional potential for the design of novel sensing strategies and to enhance the analytical performance of biosensing systems.
In this thesis three different types of miniaturisation pathways were investigated for electrochemical biosensing applications. Vertically aligned carbon nanotube thin films were designed and tested as platforms for DNA immobilisation and for the development of a model electrochemical genosensor. The sensor format involved the immobilisation of oligoucleotide probes onto the sensor surface, hybridisation with the target sequence and electrochemical detection of the duplex formation. By combining such an electrode platform with an enzyme labeling, a detection limit of oligonucleotide targets in the nanomolar range was achieved.
A novel magnetic particle-based microfluidic sensor was also realised by integrating a microfluidic platform with a new analytical procedure based on the use of paramagnetic beads for the detection of real PCR samples. The hybridisation reaction was carried out on probe-modified beads in a flow-through format, thus enhancing the surface area-to-volume ratio and consequently the sensitivity. Moreover, the magnetic properties of the beads greatly facilitated the delivery and removal of reagents through the microfluidic channels. This format allowed the detection of nanomolar levels of double-stranded DNA sequences, with high reproducibility and fast time of analysis.
Finally, polyaniline nanotubes arranged in an ordered structure directly on gold electrode surfaces were realised and employed to create a model molecularly imprinted (MIP) polymer -sensor for catechol detection. The advantages of using nanostructures in this particular biosensing application have been evaluated by comparing the analytical performance of the sensor with an analogous non-nanostructured MIP-sensor that we had previously developed. A significantly lower limit of detection (one order of magnitude) was achieved, thus
demonstrating that the nanostructures enhanced the analytical performance of the sensor
Electrochemical Detection of Vascular Endothelial Growth Factor by Molecularly Imprinted Polymer
No full textIn this study, we report the development of a sensitive label-free impedimetric sensor based on molecularly imprinted polymer (MIP) as biomimetic receptor coupled with screen-printed electrodes (SPEs) for the detection of vascular endothelial growth factor (VEGF). Firstly, electropolymerization of o-phenylenediamine (o-PD) in the presence of VEGF molecule by cyclic voltammetry was performed onto graphite screen-printed electrodes. The solvent extraction of the target was then carried out. The MIP based sensor was characterized by electrochemical techniques and scanning electron microscopy (SEM). Using optimized experimental conditions, the single-use MIP-based sensor showed a good analytical performance for VEGF detection from 20 to 200 pg mL(-1) with limit of detection of 0.08 pg mL(-1). Finally, the developed MIP-based sensor in human serum samples was also tested
Electrochemical enzyme-linked oligonucleotide array for aflatoxin B1 detection
No full textIn this work, an electrochemical enzyme-linked oligonucleotide array to achieve simple and rapid multidetection of aflatoxin B1 (AFB1) is presented. The assay is based on a competitive format and disposable screen-printed cells (SPCs). Firstly, the electrodeposition of poly(aniline-anthranilic acid) copolymer (PANI-PAA) on graphite screen-printed working electrodes was performed by means of cyclic voltammetry (CV). Aflatoxin B1 conjugated with bovine serum albumin (AFB1-BSA) was then immobilized by covalent binding on PANI-PAA copolymer. After performing the affinity reaction between AFB1 and the biotinylated DNA-aptamer (apt-BIO), the solution was dropped on the modified SPCs and the competition was carried out. The biotinylated complexes formed onto the sensor surface were coupled with a streptavidin-alkaline phosphatase conjugate. 1-naphthyl phosphate was used as enzymatic substrate; the electroactive product was detected by differential pulse voltammetry (DPV). The response of the enzyme-linked oligonucleotide assay was signal-off, according to the competitive format. A dose-response curve was obtained between 0.1 ng mL−1 and 10 ng mL−1 and a limit of detection of 0.086 ng mL−1 was achieved. Finally, preliminary experiments in maize flour samples spiked with AFB1 were also performed
Nano-biosensing platforms for detection of cow’s milk allergens: An overview
No full textAmong prevalent food allergies, cow milk allergy (CMA) is most common and may persist throughout the life. The allergic individuals are exposed to a constant threat due to milk proteins' presence in uncounted food products like yogurt, cheese, and bakery items. The problem can be more severe due to cross-reactivity of the milk allergens in the food products due to homologous milk proteins of diverse species. This problem can be overcome by proper and reliable food labeling in order to ensure the life quality of allergic persons. Therefore, highly sensitive and accurate analytical techniques should be developed to detect the food allergens. Here, significant research advances in biosensors (specifically immunosensors and aptasensors) are reviewed for detection of the milk allergens. Different allergic proteins of cow milk are described here along with the analytical standard methods for their detection. Additionally, the commercial status of biosensors is also discussed in comparison to conventional techniques like enzyme-linked immunosorbent assay (ELISA). The development of novel biosensing mechanisms/kits for milk allergens detection is imperative from the perspective of enforcement of labeling regulations and directives keeping in view the sensitive individuals
Mercury Detection in Novel Foods by a Smart Pocket Sensor
No full textMercury is one of the most well-known toxic contaminants of natural and anthropogenic origin in aquatic ecosystems that can bioaccumulate in vegetal and animal organisms. In this work, we propose a smart detection system for Hg(II) ions by square wave anodic stripping voltammetry at nanocomposite graphite screen-printed electrodes, as an analytical tool to be applied in food quality control. The nanocomposite surfaces were obtained by the modification of screen-printed graphite electrodes with poly(l-aspartic acid) and gold nanoparticles and were characterized by means of electrochemical techniques. An exhaustive study of the experimental conditions involved both in the electropolymerization and in the voltammetric stripping measurements was addressed to develop a reliable method capable of measuring Hg(II) concentration in the low mu g/L range, both in conventional and drop configurations. The sensor was integrated in a smart setup, comprising a Sensit Smart pocket instrument connected to a smartphone, thus proving its applicability for in situ analysis due to its cost-effectiveness. The analytical significance of the developed sensor was assessed by detecting Hg(II) in novel food samples.imag
Aligned carbon nanotube thin films for DNA electrochemical sensing
No full textCarbon nanotubes are interesting materials for DNA electrochemical sensing due to their unique electric
properties: high surface area, fast heterogeneous electron transfer, and electrochemical stability. In this
work aligned Carbon NanoTube (CNT) thin films were designed and tested as candidate platforms for
DNA immobilization and for the development of an electrochemical genosensor.
The filmswere prepared by Chemical Vapor Deposition (CVD) using acetylene and ammonia as precursor
gases and nickel particles as catalyst. A preliminary electrochemical characterization was performed
using cyclic voltammetry since, so far, these films have been used only for gas sensing. The surfaces were
then covalently functionalized with a DNA oligonucleotide probe, complementary to the sequence of
the most common inserts in the GMOs: the Promoter 35S. The genosensor format involved the immobilization
of the probe onto the sensor surface, the hybridization with the target-sequence and the
electrochemical detection of the duplex formation. Careful attention was paid to the probe immobilization
conditions in order to minimize the signal due to non-specifically adsorbed sequences. For the
detection of the hybridization event both label-free and enzyme-labelled methods were investigated. In
case of the enzyme-labelled method a target concentration at nanomolar level can be easily detected,
with a linear response from 50nM to 200 nM, whereas the label-free method showed a linear response
between 0.5Mand 10M. The reproducibility was 11% and 20% with the enzyme-labelledmethod and
the label-free method, respectively. The batch-to-batch reproducibility of the different sensors was also
evaluated
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