Millions of premature deaths per year from cardiovascular diseases represent a global threat urging governments to increase global initiatives, as advised by World Health Organization. In particular, ...together with prevention and management of risk factors, the development of portable platforms for early diagnosis of cardiovascular disorders appears a fundamental task to carry out. Contemporary assays demonstrated very good accuracy for diagnosis of acute myocardial infarction (AMI), but they are based on expensive and fragile capture antibodies. Accordingly, also considering the massive demand from developing countries, we have devoted our study to an affinity-based biosensor for detection of troponin T (TnT), a preferred biomarker of AMI. This combines a stable and inexpensive molecularly imprinted polymer (MIP) based on polydopamine (PDA) with surface plasmon resonance (SPR) transduction. Herein we report the fast and specific answer upon TnT binding onto an epitope-imprinted surface that strongly encourages the further development toward antibody-free point-of-care testing for cardiac injury.
•Troponin T is the most sensitive and selective biomarker of acute myocardial infarction.•Emergency and clinical tests for TnT are still based on immuno-reactions and antibodies.•Here the first TnT biosensor based on epitope imprinting on polydopamine is presented.•Epitope imprinting with short peptides from TnT allowed low-cost and fast preparation.•Direct assays in standard solutions and sandwich assays on spiked serum are reported.
Procalcitonin (PCT) has emerged as a promising biomarker for the rapid identification of sepsis both in human and veterinary medicine. Nevertheless, the only analytical method currently available for ...the detection of PCT in veterinary species, is represented by immunoassays, useful only for research purposes. In this work, we report the development of two biosensors which utilize molecularly imprinted polymers (MIPs) for the detection of canine and equine PCT. Dopamine (DA) and norepinephrine (NE) were used as monomers for the synthesis of the MIP films on surface plasmon resonance (SPR) gold chips and the imprinting efficiency of canine and equine PCT in terms of binding affinity toward the analyte, selectivity, and sensitivity were compared. After optimization in buffer conditions, PCTs calibration was successfully achieved also in animal plasma, with good specificity and reproducibility. More effective protein binding and imprinting was obtained with polynorepinephrine (PNE) for both PCTs, and the SPR biosensors were able to detect the biomarkers in plasma with a LOD of 15 ng mL−1 and 30 ng mL−1 respectively for equine and canine PCT.
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•Methods for procalcitonin detection are poorly investigated in veterinary medicine.•The only analytical method available is represented by immunoassays.•Molecular imprinting is a widely explored strategy to develop biosensors platforms.•Here we report two MIP receptors for canine and equine procalcitonin.•PDA- and PNE-based MIPs are optimized and compared by SPR.
The continuous research for alternatives to antibody-based detection drove, in the last decades, the development of numerous strategies. Molecularly imprinted polymers (MIPs) emerged thanks to the ...low-cost and long-term stability features, where the choice of natural functional monomer(s) represents the key step for efficient imprinting of biomolecules. The chemical structure of dopamine (DA), one of the most used natural functional monomers, provided the inspiration for this work. We wondered why norepinephrine (NE) that differs from dopamine only for an additional hydroxyl group was not investigated at all in biosensing applications. In fact, there is only one paper exploiting polynorepinephrine (PNE) in molecular recognition applications, taking advantage of molecular imprinting, but not for biosensing purposes. In contrast, hundreds of papers describe polydopamine-based sensors. Therefore, we firstly investigated how the additional hydroxyl group of NE could affect the properties of the resulting polymer, and how these properties could be exploited for biosensing applications. The results highlighted the reduced non-specific adsorption of proteins onto PNE with respect to dopamine polymer. Furthermore, as a case study, we successfully developed a PNE-based imprinted biosensor for the early detection of Troponin I, a crucial biomarker for heart failure, by coupling the MIP biosensor with surface plasmon resonance (SPR) detection. The results indicate the feasible use of imprinted PNE as synthetic receptor for biomolecules, opening new perspectives for this biopolymer, so far not considered, and encouraging further investigations on its potential application in biosensing.
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•Molecular imprinting is a widely explored strategy to develop biosensors platforms.•Norepinephrine has not yet been investigated as functional monomer for biosensing.•Here we evaluated the surface properties of PNE and potential applications in MIPs.•A PNE-based MIP biosensor is for the first time reported for troponin I detection.•Promising results were obtained in terms of selectivity, affinity and sensitivity
In this work a novel self-powered microneedle-based transdermal biosensor for pain-free high-accuracy real-time measurement of glycaemia in interstitial fluid (ISF) is reported.
The proposed ...transdermal biosensor makes use of an array of silicon-dioxide hollow microneedles that are about one order of magnitude both smaller (borehole down to 4µm) and more densely-packed (up to 1×106needles/cm2) than state-of-the-art microneedles used for biosensing so far. This allows self-powered (i.e. pump-free) uptake of ISF to be carried out with high efficacy and reliability in a few seconds (uptake rate up to 1µl/s) by exploiting capillarity in the microneedles. By coupling the microneedles operating under capillary-action with an enzymatic glucose biosensor integrated on the back-side of the needle-chip, glucose measurements are performed with high accuracy (±20% of the actual glucose level for 96% of measures) and reproducibility (coefficient of variation 8.56%) in real-time (30s) over the range 0–630mg/dl, thus significantly improving microneedle-based biosensor performance with respect to the state-of-the-art.
•Self-powered pain-free microneedle-based transdermal biosensor for high-accuracy measurement of glycaemia in interstitial fluid (ISF).•Pump-free (autonomous) reliable, effective, and fast uptake of ISF by exploiting capillarity in tiny hollow microneedles.•FDA compliant real-time measurement of glucose in ISF by coupling microneedles under capillary-action and enzymatic glucose biosensors.•Performance of microneedle-based glucose biosensors in ISF: time 30 s, linearity 0–630 mg/dl, accuracy within ±20% for 96% of measures.
Polydopamine decorated in-situ with Localized Surface Plasmon Resonance (LSPR)-active gold nanoparticles (AuNPs) may extend the applicability of nanoplasmonic materials to original and innovative ...applications in several fields. Here we report the modification of disposable UV–Vis polystyrene cuvettes with AuNPs@PDA for refractive index LSPR-based measurements. An original layer-by-layer deposition method of PDA followed by AuNPs growth is here developed, showing linear correlation between PDA thickness and optical properties. In particular, the modulation from wavelength sensitivity toward absorbance sensitivity is obtained, allowing measurements at fixed wavelength (578 nm). As applicative example of the photonic cuvettes, the measurement of fermentable sugars in beer wort is here reported. The analytical performance of our approach has been directly compared to portable refractometer of reference, displaying excellent results in terms of the precise estimation of sugars in beer wort (expressed in degrees Brix), reproducibility and sensitivity. The approach may be extended to other materials of interest in LSPR based optical sensors, e.g. optical fibers.
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•Polydopamine (PDA) is able to spontaneously reduce Au(III) to gold nanoparticles at their surface.•PDA films decorated with gold nanoparticles can be exploited in LSPR measurements.•A layer-by-layer growth of PDA evidences the correlation between PDA thickness and LSPR behavior.•At certain thickness, absorbance intensity change instead of wavelength shift is successfully obtained.•Measurements of sugars in beer wort are obtained and compared with a portable refractrometer.
Interest on Tau protein is fast increasing in Alzheimer's disease (AD) diagnosis. There is the urgent need of highly sensitive and specific diagnostic platforms for its quantification, also in ...combination with the other AD hallmarks. Up to now, SPR has been poorly exploited for tau detection by immunosensing, due to sensitivity limits at nanomolar level, whereas the clinical requirement is in the picomolar range. Molecular architectures built in a layer-by-layer fashion, biomolecules and nanostructures (metallic or not) may amplify the SPR signal and improve the limit of detection to the desired sensitivity. Mostly gold nanostructures are widely employed to this aim, but great interest is also emerging in Multi Walled Carbon Nanotubes (MWCNTs). Here MWCNTs are modified and then decorated with the secondary antibody for tau protein. Eventually we took advantage from MWCNTs-antibody conjugate to obtain a sandwich-based bioassay with the capability to increase the SPR signal of about 102 folds compared to direct detection and conventional unconjugated sandwich. With respect to these results, we hope to give a strong impulse for further investigation on studying possible roles of carbon nanotubes in optical-based biosensing.
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•Surface plasmon resonance immunosensor to detect tau protein is developed.•Analyzing tau in aCSF high protein stability and signal repeatability are obtained.•Sandwich assay improves selectivity and sensitivity using secondary antibody (mAb2).•Coupling secondary antibody to carbon nanotubes tau is detected down to 125pM.•Tau detection is carried out in artificial CSF.
MMP-9, human matrix metalloproteinase 9, belongs to the family of zinc-dependent peptide-bond hydrolases and is involved in the degradation of the extracellular matrix (ECM). In clinics, it is well ...known that elevated MMP-9 serum levels are associated with cardiovascular dysfunctions, several aspects of the physiology and pathology of the central nervous system, neuropsychiatric disorders and degenerative diseases related to brain tumors, and excitotoxic/neuroinflammatory processes. Due to the large interest of diagnostics in this protein, efforts to set up sensitive methods to detect MMP-9 for early diagnosis of a number of metabolic alterations are rapidly increasing. In this panorama, biosensors could play a key role; therefore we explored for the first time the development of an aptamer-based piezoelectric biosensor for a sensitive, label free, and real time detection of MMP-9. The detecting strategy involved two different aptamers in a sandwich-like approach able to detect down to 100 pg mL−1 (1.2 pM) of MMP-9 as detection limit in standard solution. As proof of principle, commercial serum was investigated in terms of possible interferents, their identification and role in MMP-9 detection. The estimated detection limit for MMP-9 is about 560 pg mL−1 (6.8 pM) in untreated serum.
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•The first piezoelectric aptasensor for human matrix metalloproteinase 9 is presented.•Specific and sensitive recognition is assured by a dual-aptamer strategy.•Matrix effect of serum is evaluated and tackled by magnetic microbeads.•Two comparable methods to quantify MMP-9 in serum, pre-treated or not, are shown.•The detection limit in buffer is 1.2 pM, comparable to 6.8 pM in untreated serum.
Two biosensors have been constructed using an RNA aptamer as biorecognition element. The aptamer, specific for HIV-1 Tat protein, has been immobilised on the gold surface of piezoelectric quartz ...crystals or surface plasmon resonance (SPR) chips to develop a quartz crystal microbalance (QCM)-based and an SPR-based biosensor, respectively. Both the biosensors were modified with the same immobilisation chemistry based on the binding of a biotinylated aptamer on a layer of streptavidin.
The binding between the immobilised aptamer and its specific protein has been evaluated with the two biosensors in terms of sensitivity, reproducibility and selectivity. A protein very similar to Tat, Rev protein, has been used as negative control.
The two biosensors both were very reproducible in the immobilisation and the binding steps. The selectivity was high in both cases.
The in vitro selection of combinatorial libraries of RNA/DNA, has allowed the identification of specific nucleic acids (aptamers) which bind to a wide range of target molecules with high affinity and ...specificity.
In this work, an RNA aptamer, specific for the protein trans-activator of transcription (Tat) of HIV-1, has been used as bio-recognition element to develop a biosensor (aptasensor). The biosensor was optimised using piezoelectric quartz-crystals as transducers and the aptamer was immobilised on the gold electrode of the crystal. The immobilisation procedure was based on the interaction between the biotinylated aptamer and streptavidin previously deposited on the electrode.
The main analytical characteristics of the biosensor, such as sensitivity, selectivity and reproducibility, have been studied in details. An optimised regeneration procedure allowed the multiple use of the aptamer-coated crystal.
The aptasensor has been compared with the corresponding immunosensor, based on the specific monoclonal anti-Tat antibody. The antibody was immobilised on a layer of carboxylated dextran previously deposited on the gold electrode.
The results demonstrated that the use of a biosensor with a specific aptamer as bio-recognition element could be an interesting approach in the detection of proteins, which has been here examined considering a model system.
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