1,721,104 research outputs found
Solid-phase synthesis of electroactive nanoparticles of molecularly imprinted polymers. A novel platform for indirect electrochemical sensing applications
Full text linkElectroactive nanoparticles of molecularly imprinted polymers (MIP NPs) specific for a non-electroactive template (i.e., the antibiotic vancomycin) were for the first time synthesized by solid-phase synthesis adding two ferrocene-derivative monomers (namely, vinylferrocene and ferrocenylmethyl methacrylate) in different amount to polymerization mixture. MIP NPs were characterized by dynamic light scattering and by cyclic voltammetry studies. This latter allowed identifying the synthetic conditions determining the highest MIP NP electroactivity. The content of electrochemical label was verified by X-Ray Photoelectron Spectroscopy, which provided an estimation of the amount of ferrocene moieties in nanoparticle structure. In the attempt to apply MIP NPs for sensing applications, nanoparticles were anchored to a Nafion modified electrode by a simple self-assembly process and the indirect electrochemical detection of vancomycin was allowed by the change of ferrocene group redox properties upon the exposure to vancomycin. The observed behavior is believed to be due to hindering of the electron transfer process of the ferrocene redox sites within nanoparticles by their interaction with non-electroactive vancomycin. A novel sensing platform is thus developed by directly anchoring to the electrode surface an electroactive probe integrated within the imprinted polymer thus allowing the selective, easy and rapid electrochemical detection of non-electroactive target molecules
An impedimetric sensor based on molecularly imprinted nanoparticles for the determination of trypsin in artificial matrices – towards point-of-care diagnostics
Full text linkA high-performance impedimetric sensing platform was designed to detect proteins by employing molecularly imprinted polymeric nanoparticles (nanoMIPs) as selective receptors. This was achieved via the combination of the nanoMIPs with a self-assembled thioctic acid (SAM-TA) monolayer onto screen-printed gold electrodes, providing stable covalent attachment of the selective binder to the transducer. Taguchi design has been modelled to achieve the optimal level of sensor fabrication parameters and to maximise the immobilisation of nanoMIPs and their response (e.g. the response of imprinted polymers compared with the non-imprinted control). The developed sensor was tested towards a range of concentrations of trypsin dissolved in ammonium acetate (pH = 6) and showed promising applicability in artificial saliva, with a recovery percentage between 103 and 107%
Correction: An impedimetric sensor based on molecularly imprinted nanoparticles for the determination of trypsin in artificial matrices – towards point-of-care diagnostics
No full textCorrection for 'An impedimetric sensor based on molecularly imprinted nanoparticles for the determination of trypsin in artificial matrices - towards point-of-care diagnostics' by Sabrina Di Masi et al., Anal. Methods, 2024, 16, 742-750, https://doi.org/10.1039/D3AY01762A
NanoMIP-based approach for the suppression of interference signals in electrochemical sensors
No full textHerein, we describe the use of molecularly imprinted nanoparticles (nanoMIPs) as sequestering (masking) agents, to suppress the signal coming from interfering molecules and facilitate the detection of the target analyte. In this work, ascorbic acid was used as a model interfering molecule in dopamine electrochemical detection. NanoMIPs selective for ascorbic acid demonstrated to be capable of binding and suppressing electrochemical signal from ascorbic acid, enabling the detection of dopamine in the range 100-500 nM, without any need for sample pre-treatment. Tests in real samples (spiked human serum) were also carried out successfully. Due to the generic nature of the imprinting process, the proposed approach can be tailored to suppress potentially any interfering species, by simply varying the type of nanoMIPs used
Dormant radical technology synthesis of materials and potential applications
Full text linkThis research was focused on the study of the polymer dormant radical
systems, species containing free radical structures that have longer lifetimes
and greater stability than radicals in general.
In order to understand the nature and reactivity of the dormant radicals,
polymeric systems capable of producing dormant free radicals were
synthesised.
In addition, the use of these novel polymeric materials in a range of applications
were studied. Those applications exploited the nature of the dormant radical
groups and included controlled modifications in the polymeric structure,
heterogeneous catalysis and chromatographic separations
Molecularly Imprinted Polymers for Cell Recognition
Full text linkSince their conception 50 years ago, molecularly imprinted polymers (MIPs) have seen extensive development both in terms of synthetic routes and applications. Cells are perhaps the most challenging target for molecular imprinting. Although early work was based almost entirely around microprinting methods, recent developments have shifted towards epitope imprinting to generate MIP nanoparticles (NPs). Simultaneously, the development of techniques such as solid phase MIP synthesis has solved many historic issues of MIP production. This review briefly describes various approaches used in cell imprinting with a focus on applications of the created materials in imaging, drug delivery, diagnostics, and tissue engineering
A development of a molecularly imprinted polymer: Specific for ochratoxin A: Theoretical and sensor applications
No full textIn this work the development of two molecularly imprinted polymers, specific
for ochratoxin A, is presented. Ochratoxin A is produced by several
Aspergillus and Penicillium species and is common in cereals and other
starch rich foods and has also been found in coffee, dried fruits, wine, beer
and meats. It demonstrates potent teratogenic, immunosuppressive,
mutagenic and carcinogenic properties. The toxin is also linked to Balkan
Endemic Nephropathy, a chronic kidney disease found in South-Eastern
Europe. Due to this the European Union has set limits on foodstuffs ranging
between 2-10 ng g-1. Therefore the requirement of a simple and inexpensive
biosensor to monitor this legislation is a necessity. Currently detection is
performed by chromatographic methods such as HPLC, and by ELISA
formats.
In this work two polymeric materials, rationally designed by computational
modelling and synthesised using molecular imprinting, are studied. The
modelling is complimented with a Nuclear Magnetic Resonance (NMR) study.
The first polymer (Polymer A) consisted of 1 mol of acrylamide and 1 mol of
methacrylic acid to 1 mol of template. This material demonstrated an unusual
binding mechanism, working solely in aqueous solvents. A theoretical
mechanism for this binding is presented and discussed.
The second polymer, again rationally designed, but under different conditions,
consisted of 1 mol of N,N- diethylamino ethyl methacrylate (DEAEM) to 1 mol
of template. This polymer demonstrated high affinity for the template in
acetonitrile.
Polymer A is used in combination with an ion-exchange SPE protocol
(developed for this purpose) for the extraction of OTA from maize.
Both polymer compositions are used in development of a MIP membrane
optical sensor, with partial success seen in the detection of OTA in grape juice
and white wine
Development Of Novel Matrices For Biomolecule Immobilisation On Sensor Surfaces
Full text linkThe development of a novel protocol for the covalent immobilisation of biomolecules containing primary amines using either polythiol compounds or novel, inexpensive and simple polymers is presented in this thesis. When developing biosensors, the method used for the immobilisation of the sensing elements is very important. The immobilisation needs to be fast, cheap and most importantly should not affect the biorecognition activity of the immobilised receptor. The chemistry used for the immobilisation is based on the well known reaction between primary amines and thioacetal groups, formed upon reaction of o-phthaldialdehyde (OPA) and thiol compounds. Initially the possibility to use this chemistry to immobilise receptors and develop biosensors was proved using commercially available polythiol compounds. Such compounds can be irreversibly adsorbed, creating self-assembling monolayers (SAMs), on noble metal transducer surfaces. These SAMs were immobilised on Biacore surface plasmon resonance (SPR) gold chips and then used to study kinetic of biomolecules interactions and to detect cells. A general protocol suitable for the immobilisation of enzymes and antibodies such as anti-prostate specific antigen (anti-PSA) and anti-Salmonella typhimurium antibody was optimised. Kinetic data were obtained for PSA binding to anti-PSA antibody and they were compared to the results obtained using commercially available Biacore chips, CM1. For Salmonella typhimurium cells, a detection limit of 5 × 106 cells ml-1 with minimal non-specific binding of other biomolecules was obtained. An interesting capability shown by these SAMs, in contrast with commercially available chips, was the opportunity to immobilise any proteins, even those with very low or high isoelectric points, pI. In addition protein immobilisation was achieved with a simple step, without requirement of any activation. These findings make this immobilisation technique a very promising alternative to peptide bond formation for amine coupling.
Even though, the developed SAMs showed to be useful for certain type of applications (kinetic study and detection of very large analyte), it was clear that due to a combination of factors (e.g. limited and steric hindrance), they were not suitable for the development of biosensors good enough for practical applications. Therefore to overcome the drawbacks shown by polythiol SAMs, a novel 3-D polymer was developed. The main advantage of this polymer is the tridimensional (3D) network, which, after
immobilisation, ensures the availability of a high percentage of receptor binding sites. As the polythiol SAMs, also the 3-D polymer contains thioacetal groups, which do not need any activation to react with primary amines in proteins. The novel 3-D polymer also contains thiol derivative groups (disulphide groups or thioethers) that promote self-assembling on metal surfaces. As before, the polymer was immobilised on SPR gold chips and the resulting layer was characterised using contact angle meter, atomic force microscopy (AFM) and ellipsometry. Contact angle demonstrated that the immobilisation of polymer on sensor surface produced a relatively hydrophobic surface. The thickness of polymer layer was determined by applying ellipsometry, whereas AFM showed the change of surface roughness after polymer attachment. A general protocol suitable for the immobilisation of BSA, enzymes and antibodies such as polyclonal anti-microcystin-LR and monoclonal anti-prostate specific antigen (anti-PSA) antibody was then optimised. The affinity characteristics of developed immunosensors were investigated in reaction with microcystin-LR, and PSA. The calculated detection limit for analytes depended on the properties of the antibodies. The detection limit for microcystin-LR was 10 ng ml
and for PSA 0.05 ng ml. The 3-D polymer chips were stored for up to 2 months without any noticeable deterioration in their ability to react with proteins. The performance of 3-D polymer chips were also compared with commercially available Biacore chips, as CM5. The main advantages were found to be the low cost, the possibility to immobilise biomolecules at physiological pH (pH 7.4), the lack of any activation step for biomolecules immobilisation and the opportunity to immobilise proteins with very different pI (also very low pI).
Despite the successful detection of PSA achieved in buffer (detection limit 0.05 ng ml-1) using 3-D polymer chips, the detection of proteins in serum resulted to be very challenging due to the complex nature of the matrix, which contains a high content of many different compounds. Different techniques were applied in order to reduce the non specific adsorption of serum on 3-D polymer sensors with antibodies immobilised on the surface. Satisfactory results were finally obtained by including the surfactant P20 into the measuring system. The detection of PSA in serum using 3-D polymer sensors, however, became possible only by switching from a direct detection to a ‘sandwich detection’. In this sandwich format, after injecting samples of PSA (prepared both in buffer or 20%
serum) onto a specific antibody (capture-Ab, C-Ab) immobilised on the 3-D polymer surface, the analytical signal is recorded by injecting a second specific Ab (detection-Ab, prepared in PBS), which recognises a different epitope of the antigen. With this format, the analytical signal is recorded in absence of any complex matrix, avoiding interference from non specific adsorption. The detection limit for PSA, obtained using the sandwich immunosensor (developed on 3-D polymer chips) was 0.1 ng ml-1 in buffer and 5 ng ml-1 in 20% serum, which is very close to the sensitivity necessary for detection of the prostate biomarker in real samples. Therefore this study has demonstrated the opportunity to apply the novel 3-D polymer for development of biosensors suitable for applications in real samples
Disposable electrochemical sensor based on ion imprinted polymeric receptor for Cd(II) ion monitoring in waters
Full text linkCadmium is a highly toxic heavy metal, even at low concentrations. Moreover, it bio-accumulates with a long biological half-life producing a wide variety of acute and chronic effects like cancer in humans. Therefore, there is significant interest in providing a portable and user-friendly sensor for heavy metal detection. A highly sen-sitive and selective electrochemical sensor for Cd(II) determination was developed as an alternative. The Cd (II) receptors were integrated into the sensor using an ion-imprinted polymer film (IIPs film). Accordingly, 4-amino-phenylacetic acid (4-APA) was electropolymerised in the presence of Cd(II) ions as a template using cyclic voltammetry (CV) on screen-printed carbon electrodes (SPCEs). Imprinted cavities were obtained after the alkaline elution of ions. Sensor characterisation was performed using SEM, ATR-FTIR and electrochemical methods, such as cyclic voltammetry (CV) and electrochemical Impedance Spectroscopy (EIS), and compared to control experiments (not imprinted polymeric film, NIP film). Analytical performances of the IIP sensor revealed a sensitivity 5-order of magnitude higher than the NIP response in a concentration range from 10 to 1200 nM of Cd (II). This technology can potentially be applied for water quality control and monitoring of heavy metals
Rational analysis of physico-chemical parameters affecting recognition properties of molecularly imprinted polymers
No full textMolecularly imprinted polymers (MIPs) are new type of materials with tailor
made molecular
recognition sites. Despite their enormous potential in separations,
sensing and pharmaceutical industry, MIPs have so far failed to achieve significant
commercial
application. This is in part due to lack of understanding of MIPs at a
molecular level, strong binding site heterogeneity and poor compatibility with
aqueous solvents. This work is aimed at improving overall MIP performance and
quality, with special focus on the improvement of compatibility with aqueous
environment.
Compatibility with aqueous solvents was achieved by (i) employing a
molecular
modelling step prior to polynerisation, (ii) by studying the ionic properties
of the
polymer and (iii) by analysis of the influence of different polymerisation
conditions. The
study of the pressure and magnetic field effects on polymers allowed
us to
produce materials with increased stability, lower binding site heterogeneity and
higher affinity, as compared to standard imprinted materials. To minimise site
heterogeneity imprinted nanoparticles with ca. 90 kDa were produced using a living
polymerisation method. The particles with essentially uniform population of binding
sites were obtained
by employing affinity chromatography with immobilised
template. As a model system variety of drugs were imprinted with the polymers being
able to discriminate between
closely related structural analogues in aqueous media.
This work had substantial effect on success of project Pisarro - Piezoelectric
Sensing Arrays for Biomolecular Interactions and Gas Monitoring where range of
imprinted polymers were designed with high affinity to drugs of abuse. Currently
1
work is in
progress aimed at application of these materials in commercial sensors for
forensic use
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