Toward nano-sized imprinted norepinephrine-derived biopolymer as artificial receptors for detecting IgG1 by surface plasmon resonance

Bio-based nanostructured molecularly imprinted polymers (nano-MIPs), also known as 'plastibodies', have a real potential to be used as alternatives to natural antibodies. These nanostructures have recently gained significant attention for diagnostic and therapeutic purposes. In this context, we have developed polynorepinephrine (PNE)-based nano-MIPs using an eco-friendly one-pot process for the sensitive and selective detection of a model biomolecule, immunoglobulin IgG1. We first investigated non-imprinted nanostructures (nano-NIPs) based on polydopamine as reference material, using DLS, SEM, and UV-Vis spectroscopy. Subsequently, PNE scaffolds were characterized, both in the form of nano-NIPs and nano-MIPs. Concerning nano-MIPs, we used the epitope-directed imprinting technology to create binding cavities using a small peptide from the constant region of IgG1 as a template. Nano-MIPs were initially immobilized on a sensing surface to assess their binding capacity via surface plasmon resonance (SPR) spectroscopy. This strategy showed very good sensitivity, outperforming planar PNE-based imprinted films while keeping a high selectivity even in complex biological matrices such as human serum. Furthermore, we confirmed the presence of selective binding sites on nano-MIPs by flowing them, along with nano-NIPs, through a microfluidic SPR system, where they interact with the covalently immobilized analyte. This approach resulted in a good imprinting factor of 4.5. Overall, this study underscores the broad potential of these nanostructures as a viable and reusable alternative to antibodies across a variety of bioanalytical, biochemical, and immunohistochemistry analysis techniques.

Health and economic impact of dapagliflozin for type 2 diabetes patients who had or were at risk for atherosclerotic cardiovascular disease in the Italian general practitioners setting: a budget impact analysis

AIM

In 2022, in Italy, general practitioners (GPs) have been allowed to prescribe SGLT2i in Type 2 Diabetes (T2D) under National Health Service (NHS) reimbursement. In the pivotal clinical trial named DECLARE-TIMI 58, dapagliflozin reduced the risk of hospitalization for heart failure, CV death and kidney disease progression compared to placebo in a population of T2D patients. This study evaluated the health and economic impact of dapagliflozin for T2D patients who had or were at risk for atherosclerotic cardiovascular disease in the Italian GPs setting.

METHODS

A budget impact model was developed to assess the health and economic impact of introducing dapagliflozin in GPs setting. The analysis was conducted by adopting the Italian NHS perspective and a 3-year time horizon. The model estimated and compared the health outcomes and direct medical costs associated with a scenario with dapagliflozin and other antidiabetic therapies available for GPs prescription (scenario B) and a scenario where only other antidiabetic therapies are available (scenario A). Rates of occurrence of cardiovascular and renal complications as well as adverse events were captured from DECLARE-TIMI 58 trial and the literature, while cost data were retrieved from the Italian tariff and the literature. One-way sensitivity analyses were conducted to test the impact of model parameters on the budget impact.

RESULTS

The model estimated around 442.000 patients eligible for the treatment with dapagliflozin in the GPs setting for each simulated year. The scenario B compared to scenario A was associated with a reduction in the occurrence of cardiovascular and renal complication (-1.83%) over the 3 years simulated. Furthermore, the scenario A allowed for an overall cost saving of 102,692,305€: 14,521,464€ in the first year, 33,007,064€ in the second and 55,163,777€ in the third. The cost of cost of drug acquisition, the probability of cardiovascular events and the percentage of patients potentially eligible to the treatment were the factor with largest impact on the results.

CONCLUSIONS

The use of dapagliflozin in GPs setting reduce the number of CVD events, kidney disease progression and healthcare costs in Italy. These data should be considered to optimize the value produced for the T2D patients who had or were at risk for atherosclerotic cardiovascular disease.

Serotonin: A new super effective functional monomer for molecular imprinting. The case of TNF-α detection in real matrix by Surface Plasmon Resonance

Molecular imprinting and related technologies are becoming increasingly appreciated in bioanalysis and diagnostic applications. Among the imprinted polymers, we have already demonstrated that the endogenous neurotransmitters (NTs) dopamine (DA) and norepinephrine (NE) can be efficiently used as natural and sustainable monomers to straightforwardly design and synthesize a new generation of green and "soft" Molecularly Imprinted BioPolymers (MIBPs). Here, we demonstrated for the first time the ability of a further NT, i.e., serotonin (SE), in forming adhesive imprinted nanofilms coupled to label-free optical biosensing. Its imprinting efficiency is compared with those obtained with PDA and PNE. As a model study, tumor necrosis factor-alpha (TNF-α) was selected as a biomolecular target of interest in clinical diagnostics. The biomimetic receptor was coupled to Surface Plasmon Resonance (SPR), and TNF-α detection was performed in label-free and real-time manner both in buffer and biological matrices, i.e. synovial fluid and human serum. The results indicate that, under the same imprinting and binding conditions, the analytical performances of PSE are impressively superior to those of PDA and PNE. The PSE-based MIBP was able to detect TNF-α in human matrices with a good sensitivity, selectivity, and repeatability.

Quantitative Colorimetric Sensing of Carbidopa in Anti-Parkinson Drugs Based on Selective Reaction with Indole-3-Carbaldehyde

The quality of life of patients affected by Parkinson's disease is improved by medications containing levodopa and carbidopa, restoring the dopamine concentration in the brain. Accordingly, the affordable quality control of such pharmaceuticals is very important. Here is reported the simple and inexpensive colorimetric quantification of carbidopa in anti-Parkinson drugs by the selective condensation reaction between the hydrazine group from carbidopa and the formyl functional group of selected aldehydes in acidified hydroalcoholic solution. An optical assay was developed by using indole-3-carbaldehyde (I3A) giving a yellow aldazine in EtOH:H2O 1:1 (λmax~415 nm) at 70 °C for 4 h, as confirmed by LC-MS analysis. A filter-based plate reader was used for colorimetric data acquisition, providing superior results in terms of analytical performances for I3A, with a sensitivity ~50 L g-1 and LOD ~0.1 mg L-1 in comparison to a previous study based on vanillin, giving, for the same figures of merit values, about 13 L g-1 and 0.2-0.3 mg L-1, respectively. The calibration curves for the standard solution and drugs were almost superimposable, therefore excluding interference from the excipients and additives, with very good reproducibility (avRSD% 2-4%) within the linear dynamic range (10 mg L-1-50 mg L-1).

Sensing of Catecholamine in Human Urine Using a Simple Colorimetric Assay Based on Direct Melanochrome and Indolequinone Formation

We used the first enzyme-free synthesis and stabilization of soluble melanochrome (MC) and 5,6-indolequinone (IQ) derived from levodopa (LD), dopamine (DA), and norepinephrine (NE) oxidation to develop a simple colorimetric assay for catecholamine detection in human urine, also elucidating the time-dependent formation and molecular weight of MC and IQ using UV-Vis spectroscopy and mass spectrometry. The quantitative detection of LD and DA was achieved in human urine using MC as a selective colorimetric reporter to demonstrate the potential assay applicability in a matrix of interest in therapeutic drug monitoring (TDM) and in clinical chemistry. The assay showed a linear dynamic range between 5.0 mg L^-1 and 50.0 mg L^-1, covering the concentration range of DA and LD found in urine samples from, e.g., Parkinson's patients undergoing LD-based pharmacological therapy. The data reproducibility in the real matrix was very good within this concentration range (RSD_av% 3.7% and 6.1% for DA and LD, respectively), also showing very good analytical performances with the limits of detection of 3.69 ± 0.17 mg L^-1 and 2.51 ± 0.08 mg L^-1 for DA and LD, respectively, thus paving the way for the effective and non-invasive monitoring of dopamine and levodopa in urine from patients during TDM in Parkinson's disease.

Serotonin-Derived Fluorophore: A Novel Fluorescent Biomaterial for Copper Detection in Urine

We took advantage of the fluorescent features of a serotonin-derived fluorophore to develop a simple and low-cost assay for copper in urine. The quenching-based fluorescence assay linearly responds within the concentration range of clinical interest in buffer and in artificial urine, showing very good reproducibility (CV_av% = 4% and 3%) and low detection limits (16 ± 1 μg L^-1 and 23 ± 1 μg L^-1). The Cu²⁺ content was also estimated in human urine samples, showing excellent analytical performances (CV_av% = 1%), with a limit of detection of 59 ± 3 μg L^-1 and a limit of quantification of 97 ± 11 μg L^-1, which are below the reference value for a pathological Cu²⁺ concentration. The assay was successfully validated through mass spectrometry measurements. To the best of our knowledge, this is the first example of copper ion detection exploiting the fluorescence quenching of a biopolymer, offering a potential diagnostic tool for copper-dependent diseases.

Advances and perspectives in the analytical technology for small peptide hormones analysis: A glimpse to gonadorelin

In the last twenty years, we have witnessed an important evolution of bioanalytical approaches moving from conventional lab bench instrumentation to simpler, easy-to-use techniques to deliver analytical responses on-site, with reduced analysis times and costs. In this frame, affinity reagents production has also jointly advanced from natural receptors to biomimetic, abiotic receptors, animal-free produced. Among biomimetic ones, aptamers, and molecular imprinted polymers (MIPs) play a leading role. Herein, our motivation is to provide insights into the evolution of conventional and innovative analytical approaches based on chromatography, immunochemistry, and affinity sensing referred to as peptide hormones. Indeed, the analysis of peptide hormones represents a current challenge for biomedical, pharmaceutical, and anti-doping analysis. Specifically, as a paradigmatic example, we report the case of gonadorelin, a neuropeptide that in recent years has drawn a lot of attention as a therapeutic drug misused in doping practices during sports competitions.

Imprinted biopolymers as green abiotic route in immunoglobulin affinity plasmonic sensing

The relentless research in material science is pushing towards sustainable building blocks, which may be exploited in the molecularly imprinting technology, a potentially ground-breaking tool for producing affinity mimetic receptors. In this scenario, we report and characterize a novel polynorepinephrine (PNE)-based mimetic for IgG detection, biomolecules of utmost clinical interest, coupled to a label-free and real-time sensing based on Surface Plasmon Resonance (SPR). A "molecular walk" around the Y-shaped IgG structure is performed to select small peptide portions to be used as templates during the epitope imprinting process. For real-time diagnosis, the mimetic receptor is integrated into SPR sensing platform, to directly target the IgG both in standard solutions and human serum specimens using the standard addition method. The designed platform is characterized in terms of binding kinetic/affinity parameters and analytical figures of merit, (selectivity, repeatability, limit of detection and quantification, namely 0.90 ± 0.02 μg mL^-1 and 3.01 ± 0.07 μg mL^-1, respectively), displaying excellent promising outcomes also when the material is subjected to thermal stress. Comprehensively, the excellent analytical performances of the MIP-based SPR sensing and the well-known versatility of such biopolymer encourage the further development of serological point-of-care testing for IgG antibodies detection.

Colorimetric determination of carbidopa in anti-Parkinson drugs based on 4-hydroxy-3-methoxybenzaldazine formation by reaction with vanillin

In this paper is reported the selective colorimetric detection and quantification of carbidopa, an inhibitor of aromatic amino acid decarboxylase, in the co-presence of levodopa as dopamine precursor in pharmaceutical formulations for the treatment of Parkinson's disease. The method is based on the selective condensation reaction between the hydrazine group from carbidopa and the formyl functional group of vanillin, a natural flavoring agent, in acidified alcoholic solution. The yellow color development (λmax ~ 420 nm) due to the formation of 4-hydroxy-3-methoxybenzaldazine (HMOB) was observed for carbidopa only, whereas levodopa, lacking the hydrazine group, did not color the solution, as expected. The calibration curves for two tablet formulations of levodopa in combination with carbidopa (4:1) were superimposable with levodopa/carbidopa (4:1), as well as carbidopa alone, in standard solution, i.e., the excipients and additives did not interfere with carbidopa determination, corresponding to a mean recovery about 105%. The linear dynamic range was between 5.00 and 50.0 mg L-1 with very good reproducibility within this range (CVav% about 3-4%) and very good sensitivity, with limits of quantification of about 1 mg L-1. The colorimetric method developed here is very simple, inexpensive, and effective for drug estimation and quality control of pharmaceutical formulations.

Structurally Constrained MUC1-Tn Mimetic Antigen as Template for Molecularly Imprinted Polymers (MIPs): A Promising Tool for Cancer Diagnostics

Abnormal glycoconjugates have distinctly been recognized as potential biomarkers for cancer diagnosis. A great deal of attention has been focused on Tn antigen, an oversimplified mucin-1 O-glycan, over-expressed in different cancers. Herein, we investigate the possibility to replace the use of anti-Tn monoclonal antibodies with an innovative class of catecholamine-based Molecularly Imprinted Polymers (MIPs), emerging in recent years as promising tools for bioanalytical applications. MIPs are synthetic receptors characterized by high sensitivity and specificity towards the imprinted target. Here, original polynorepinephrine-based MIPs coupled to Surface Plasmon Resonance biosensing for Tn antigen recognition are reported. We have verified the imprinting and binding capacity of these MIPs towards very small antigenic entities, represented by the natural Tn antigen and the TnThr mimetic 1 (conjugated to BSA or linked to a MUC1 hexapeptide analogue), and compared the biosensor performances with an anti-Tn monoclonal antibody. The results clearly display the effectiveness of the pursued imprinting strategies.

Conformationally Constrained Sialyl Analogues as New Potential Binders of h-CD22

Here, two conformationally constrained sialyl analogues were synthesized and characterized in their interaction with the inhibitory Siglec, human CD22 (h‐CD22). An orthogonal approach, including biophysical assays (SPR and fluorescence), ligand‐based NMR techniques, and molecular modelling, was employed to disentangle the interaction mechanisms at a molecular level. The results showed that the Sialyl‐TnThr antigen analogue represents a promising scaffold for the design of novel h‐CD22 inhibitors. Our findings also suggest that the introduction of a biphenyl moiety at position 9 of the sialic acid hampers canonical accommodation of the ligand in the protein binding pocket, even though the affinity with respect to the natural ligand is increased. Our results address the search for novel modifications of the Neu5Ac‐α(2‐6)‐Gal epitope, outline new insights for the design and synthesis of high‐affinity h‐CD22 ligands, and offer novel prospects for therapeutic intervention to prevent autoimmune diseases and B‐cell malignancies.

Colorimetric selective quantification of anthocyanins with catechol/pyrogallol moiety in edible plants upon zinc complexation

Here is examined the colour development from common anthocyanins (i.e., cyanidin, delphinidin, malvidin, and pelargonidin glycosides) and from anthocyanins-rich extracts (i.e., bilberries, strawberries, and raspberries), using zinc-anthocyanin complexes as molecular probe. We have observed the absorbance increase in the blue region in presence of large excess of zinc ion at acidic pH for cyanidin and delphinidin derivatives, likely due to quinoidal base stabilization from catechol and pyrogallol moiety. The assay condition were studied and applied to natural extracts containing these compounds. The same behaviour was observed for bilberry and, to a minor extent, for raspberry extracts, due to the larger cyanidin/delphinidin contents in the former than in the latter. Anthocyanin standard UV-Vis analysis in buffer has shown a very good linear correlation for cyanidin and delphinidin (R² = 0.995 and 0.997, respectively), good precision (CV% = 7.4% and 5.3% respectively), high sensitivity (Cyε_600nm = 8300 M^-1 cm^-1, LOD = 0.264 ± 0.005 mg L^-1, LOQ = 0.478 ± 0.007 mg L^-1, and Dpε_600nm = 15,900 M^-1 cm^-1, LOD = 0.143 ± 0.002 mg L^-1, LOQ = 0.478 ± 0.007 mg L^-1). The effectiveness of this colorimetric method for the selective quantification of catechol/pyrogallol-based anthocyanins has been demonstrated in the aforementioned complex real matrices and compared to LC-MS/MS analysis and pH-differential method, offering a valuable tool to characterize plant and food extracts particularly rich in zinc-coordinating anthocyanins.

Melanochrome-based colorimetric assay for quantitative detection of levodopa in co-presence of carbidopa and its application to relevant anti-Parkinson drugs

In this paper is reported the selective detection and quantification of levodopa in co-presence of carbidopa. The method took advantage of the spontaneous oxidation and color development of levodopa at basic pH here driven by alkaline earth cations and co-solvent in solution. We have shown for the first time the generation and stabilization of the purple melanochrome from levodopa, by using magnesium acetate and dimethyl sulfoxide, which was here exploited for the development of a quantitative colorimetric assay for the active principle ingredient in commercial drugs for the treatment of Parkinson's disease. The calibration curves of levodopa in the two tablet formulations, containing carbidopa as decarboxylase inhibitor, showed a common linear trend between 10 mg L^-1 and 40 mg L^-1 with levodopa alone or in combination with carbidopa in standard solutions, with very good reproducibility (CV_av%, 3.3% for both brand and generic drug) and very good sensitivity, with limit of quantification about 0.6 mg L^-1 in any case. The colorimetric method here developed is very simple and effective, appearing as a rapid and low-cost alternative to other methodologies, involving large and expensive instrumentations, for drug estimation and quality control of pharmaceutical formulations.

Sensitive 'two-steps' competitive assay for gonadotropin-releasing hormone detection via SPR biosensing and polynorepinephrine-based molecularly imprinted polymer

The 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.

3,3',5,5'-tetramethylbenzidine as multi-colorimetric indicator of chlorine in water in line with health guideline values

Sanitizing solutions against bacterial and viral pathogens are of utmost importance in general and, in particular, in these times of pandemic due to Sars-Cov2. They frequently consist of chlorine-based solutions, or in the direct input of a certain amount of chlorine in water supply systems and swimming pools. Colorimetry is one of the techniques used to measure the crucial persistence of chlorine in water, including household chlorine test kits commonly based on colorimetric indicators. Here, we show a simple and cheap colorimetric method based on 3,3',5,5'-tetramethylbenzidine (TMB), commonly used as chromogenic reagent for enzyme-linked immunosorbent assays. TMB is converted by chlorine to a colored molecule through a pH-dependent multi-step oxidation process where the chromaticity of TMB is directly proportional to chlorine content. This molecule offers several advantages over other commonly used reagents in terms of safety, sensitivity, and, peculiarly, hue modulation, giving rise to the detection of chlorine in water with a multi-color change of the indicator solution (transparent/blue/green/yellow). Moreover, through the appropriate setting of reaction conditions, such coloration is finely tunable to cover the range of chlorine concentration recommended by international health agencies for treatment of drinking water and swimming pools and to test homemade solutions prepared by dilution of household bleach during health emergency events such as during the current pandemic. Graphical abstract.

Characterization of troponin T binding aptamers for an innovative enzyme-linked oligonucleotide assay (ELONA)

Early diagnosis of acute myocardial infarction (AMI) is of outmost importance to reduce the mortality rate, and cardiac troponins are considered the gold standard biomarkers of myocardial necrosis. In this scenario, the characterization of two troponin T (TnT)-binding aptamers as viable alternative to antibodies employed on clinical immunoassays is here reported for the first time. Their recognition ability was first investigated through surface plasmon resonance (SPR). Subsequently, an enzyme-linked oligonucleotide assay (ELONA) was developed on common 96-well polystyrene plates, both by direct and sandwich detection strategies for comparison. In both cases, the assay exhibits a detection ability of TnT in the range of low nanomolar but a great advantage on serum interference was obtained by using both aptamers in a sandwich format, with excellent reproducibility and recovery values. Despite the sensitivity needing to be enhanced to the low picomolar range, these results are encouraging for the development of new, low-cost, and rapid antibody-free colorimetric assays for AMI studies based on aptamer-Troponin T recognition.

Erratum: Li, D.; Scarano, S.; Lisi, S.; Palladino, P.;Minunni, M. Real-Time Tau Protein Detection bySandwich-Based Piezoelectric Biosensing: ExploringTubulin as a Mass Enhancer. Sensors 2018, 18, 946

The authors wish to make the following erratum to this paper [...].

A straightforward synthesis of phenyl boronic acid (PBA) containing BODIPY dyes: new functional and modular fluorescent tools for the tethering of the glycan domain of antibodies

We report here on the efficient and straightforward synthesis of a series of modular and functional PBA-BODIPY dyes 1–4. They are an outstanding example of the efficient merge of the versatility of the 3,5-dichloro-BODIPY derivatives and the receptor-like ability of the PBA moiety. The potential bioanalytical applicability of these tools was assessed by measuring the binding to glycan chains of antibodies by a Quartz Crystal Microbalance (QCM).

PBA-BODIPY dyes as functional and modular fluorescent probes for the tethering of the glycan domain of mAbs.

Real-Time Tau Protein Detection by Sandwich-Based Piezoelectric Biosensing: Exploring Tubulin as a Mass Enhancer

Human tau protein is one of the most advanced and accepted biomarkers for AD and tauopathies diagnosis in general. In this work, a quartz crystal balance (QCM) immunosensor was developed for the detection of human tau protein in buffer and artificial cerebrospinal fluid (aCSF), through both direct and sandwich assays. Starting from a conventional immuno-based sandwich strategy, two monoclonal antibodies recognizing different epitopes of tau protein were used, achieving a detection limit for the direct assay in nanomolar range both in HBES-EP and aCSF. Afterward, for exploring alternative specific receptors as secondary recognition elements for tau protein biosensing, we tested tubulin and compared its behavior to a conventional secondary antibody in the sandwich assay. Tau–tubulin binding has shown an extended working range coupled to a signal improvement in comparison with the conventional secondary antibody-based approach, showing a dose–response trend at lower tau concentration than is usually investigated and closer to the physiological levels in the reference matrix for protein tau biomarker. Our results open up new and encouraging perspectives for the use of tubulin as an alternative receptor for tau protein with interesting features due to the possibility of taking advantage of its polymerization and reversible binding to this key hallmark of Alzheimer’s disease.

Determination of fermentable sugars in beer wort by gold nanoparticles@polydopamine: A layer-by-layer approach for Localized Surface Plasmon Resonance measurements at fixed wavelength

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.

Sample-to-answer acoustic detection of DNA in complex samples

The present study demonstrates the sensitive and label-free acoustic detection of dsDNA amplicons produced from whole Salmonella Thyphimurium cells without employing any DNA extraction and/or purification step, in the presence of the lysed bacterial cells and in a hybridization-free assay.

Streptavidin-coated gold nanoparticles: critical role of oligonucleotides on stability and fractal aggregation

Gold nanoparticles (AuNPs) exhibit unique properties that can be modulated through a tailored surface functionalization, enabling their targeted use in biochemical sensing and medical diagnostics. In particular, streptavidin-modified AuNPs are increasingly used for biosensing purposes. We report here a study of AuNPs surface-functionalized with streptavidin-biotinylated oligonucleotide, focussing on the role played by the oligonucleotide probes in the stabilization/destabilization of the functionalized nanoparticle dispersion. The behaviour of the modified AuNP dispersion as a consequence of the competitive displacement of the biotinylated oligonucleotide has been investigated and the critical role of displaced oligonucletides in triggering the quasi one-dimensional aggregation of nanoparticles is demonstrated for the first time. The thorough understanding of the fundamental properties of bioconjugated AuNPs is of great importance for the design of highly sensitive and reliable functionalized AuNP-based assays.

Surface plasmon resonance for the label-free detection of Alzheimer's β-amyloid peptide aggregation

Amyloid peptide oligomers and fibrils are studied as targets for therapy and diagnosis of Alzheimer's disease. They are usually detected by amyloid incubation, but such method is necessarily associated with Aβ1-42 depletion and dye binding or conjugation, which have a complex influence on fibril growth, provide information about fibril elongation over long time periods only, and might lead to false-positive results in amyloid inhibition assay. Surface plasmon resonance (SPR) is used to study with no labelling and in real time the aggregation of Aβ1-42 amyloid on specific antibodies. SPR data show, for the first time by using SPR, a multi-phase association behavior for Aβ1-42 oligomers accounting for a sigmoidal growth of amyloid as a function of time, with two antibody-dependent aggregation patterns. The new method represents an advantageous alternative to traditional procedures for investigating amyloid self-assembly and inhibition from early-stage oligomer association, on the time scale of seconds to minutes, to long-term polymerization, on the time scale of hours to days.

Conformation and self-association of peptide amphiphiles based on the KTTKS collagen sequence

Studying peptide amphiphiles (PAs), we investigate the influence of alkyl chain length on the aggregation behavior of the collagen-derived peptide KTTKS with applications ranging from antiwrinkle cosmetic creams to potential uses in regenerative medicine. We have studied synthetic peptides amphiphiles C(14)-KTTKS (myristoyl-Lys-Thr-Thr-Lys-Ser) and C(18)-KTTKS (stearoyl-Lys-Thr-Thr-Lys-Ser) to investigate in detail their physicochemical properties. It is presumed that the hydrophobic chain in these self-assembling peptide amphiphiles enhances peptide permeation across the skin compared to KTTKS alone. Subsequently C(n)-KTTKS should act as a prodrug and release the peptide by enzymatic cleavage. Our results should be useful in the further development of molecules with collagen-stimulating activity.

Ionic strength effects on the critical micellar concentration of ionic and nonionic surfactants: the binding model

We have recently investigated the aggregation behavior of zwitterionic n-dodecyl phosphocholine in the presence of high salt. As double logarithmic Corrin-Harkins plots of the critical micellar concentration versus the salt concentration were not linear, here we re-examine those data in the context of the binding model of surfactant aggregation, as previously developed by us for ionic surfactants. We have also re-examined plenty of data available in the literature on the salt-dependent aggregation of neutral surfactants. The use of double-logarithmic plots allowed us to show that the binding model is of general applicability. Indeed, it permits unified treatment of ionic and uncharged aggregation without requiring the introduction of linear terms in the salt concentration, as needed in the empirical Corrin-Harkins treatment of nonionic surfactants. The use of this model could be of help in a broad range of surfactant-based applications in the presence of high salt.

Visual Analysis of Large Graphs Using (X,Y)-Clustering and Hybrid Visualizations

Many different approaches have been proposed for the challenging problem of visually analyzing large networks. Clustering is one of the most promising. In this paper, we propose a new clustering technique whose goal is that of producing both intracluster graphs and intercluster graph with desired topological properties. We formalize this concept in the (X,Y) -clustering framework, where Y is the class that defines the desired topological properties of intracluster graphs and X is the class that defines the desired topological properties of the intercluster graph. By exploiting this approach, hybrid visualization tools can effectively combine different node-link and matrix-based representations, allowing users to interactively explore the graph by expansion/contraction of clusters without loosing their mental map. As a proof of concept, we describe the system Visual Hybrid (X,Y)-clustering (VHYXY) that implements our approach and we present the results of case studies to the visual analysis of social networks.

Amphiphilic CCK peptides assembled in supramolecular aggregates: structural investigations and in vitro studies

Supramolecular aggregates obtained by self-aggregation of five new cationic amphiphilic CCK8 peptides have been obtained in water solution and characterized for: (i) aggregate structure and stability; (ii) CCK8 peptide conformation and bioavailability on the external aggregate surface; and (iii) for their cell binding properties. The cationic amphiphilic CCK8 peptides self-aggregate giving a combination of liposomal and micelle structures, with radii ranging between ~60 nm and ~90 nm, and between ~5 and ~10 nm, respectively. The presence of CCK8 peptide well-exposed on the aggregate surface is demonstrated by fluorescence measurements. Peptide conformation changes in the five supramolecular aggregates: the CCK8 conformational behaviour is probably induced by the presence of three charged lysine residues close to the bioactive peptide sequence. Only aggregates in which the CCK8 peptide presents a structural arrangement similar to that found for the same peptide in DPC micelles give promising binding properties to CCK2-R receptors overexpressed by transfected A431 cells. Chemical modifications on the CCK8 N-terminus seem to play an important role in stabilizing the peptide active conformation, either when the peptide derivative is in monomeric or in aggregate form. For their easy preparation procedures and their binding properties, supramolecular aggregates based on cationic peptide amphiphiles can be considered as promising candidates for target selective drug carriers on cancer cells.

Privacy impact assessment in the design of transnational public health information systems: the BIRO project

OBJECTIVES

To foster the development of a privacy-protective, sustainable cross-border information system in the framework of a European public health project.

MATERIALS AND METHODS

A targeted privacy impact assessment was implemented to identify the best architecture for a European information system for diabetes directly tapping into clinical registries. Four steps were used to provide input to software designers and developers: a structured literature search, analysis of data flow scenarios or options, creation of an ad hoc questionnaire and conduction of a Delphi procedure.

RESULTS

The literature search identified a core set of relevant papers on privacy (n = 11). Technicians envisaged three candidate system architectures, with associated data flows, to source an information flow questionnaire that was submitted to the Delphi panel for the selection of the best architecture. A detailed scheme envisaging an "aggregation by group of patients" was finally chosen, based upon the exchange of finely tuned summary tables.

CONCLUSIONS

Public health information systems should be carefully engineered only after a clear strategy for privacy protection has been planned, to avoid breaching current regulations and future concerns and to optimise the development of statistical routines. The BIRO (Best Information Through Regional Outcomes) project delivers a specific method of privacy impact assessment that can be conveniently used in similar situations across Europe.

Effective critical micellar concentration of a zwitterionic detergent: a fluorimetric study on n-dodecyl phosphocholine

We have investigated the effect of ionic strength on the aggregation behavior of n-dodecyl phosphocholine. On the basis of the classical Corrin-Harkins relation, the critical micellar concentration of this detergent decreases with a biphasic trend on lithium chloride addition. It is nearly constant below 150 mM salt, with a mean value of 0.91 mM, whereas it undergoes a dramatic 80-fold decrease in 7 M LiCl. Such a drop in the critical micellar concentration could be explained by the effect of salting out and the implication of phosphocholine head groups on the organization of surrounding water. Knowledge of the effective critical micellar concentration of n-dodecyl phosphocholine could be useful in the purification of membrane proteins in non-denaturing conditions.

A thermodynamic approach to the conformational preferences of the 180-195 segment derived from the human prion protein alpha2-helix

On consideration that intrinsic structural weakness could affect the segment spanning the alpha2-helical residues 173-195 of the PrP, we have investigated the conformational stabilities of some synthetic Ala-scanned analogs of the peptide derived from the 180-195 C-terminal sequence, using a novel approach whose theoretical basis originates from protein thermodynamics. Even though a quantitative comparison among peptides could not be assessed to rank them according to the effect caused by single amino acid substitution, as a general trend, all peptides invariably showed an appreciable preference for an alpha-type organization, consistently with the fact that the wild-type sequence is organized as an alpha-helix in the native protein. Moreover, the substitution of whatever single amino acid in the wild-type sequence reduced the gap between the alpha- and the beta-propensity, invariably enhancing the latter, but in any case this gap was larger than that evaluated for the full-length alpha2-helix-derived peptide. It appears that the low beta-conformation propensity of the 180-195 region depends on the simultaneous presence of all of the Ala-scanned residues, indirectly confirming that the N-terminal 173-179 segment could play a major role in determining the chameleon conformational behavior of the entire 173-195 region in the PrP.

Structural characterization of a neurotoxic threonine-rich peptide corresponding to the human prion protein alpha 2-helical 180-195 segment, and comparison with full-length alpha 2-helix-derived peptides

The 173-195 segment corresponding to the helix 2 of the globular PrP domain is a good candidate to be one of the several 'spots' of intrinsic structural flexibility, which might induce local destabilization and concur to protein transformation, leading to aggregation-prone conformations. Here, we report CD and NMR studies on the alpha2-helix-derived peptide of maximal length (hPrP[180-195]) that is able to exhibit a regular structure different from the prevalently random arrangement of other alpha2-helix-derived peptides. This peptide, which has previously been shown to be affected by buffer composition via the ion charge density dependence typical of Hofmeister effects, corresponds to the C-terminal sequence of the PrP(C) full-length alpha2-helix and includes the highly conserved threonine-rich 188-195 segment. At neutral pH, its conformation is dominated by beta-type contributions, which only very strong environmental modifications are able to modify. On TFE addition, an increase of alpha-helical content can be observed, but a fully helical conformation is only obtained in neat TFE. However, linking of the 173-179 segment, as occurring in wild-type and mutant peptides corresponding to the full-length alpha2-helix, perturbs these intrinsic structural propensities in a manner that depends on whether the environment is water or TFE. Overall, these results confirm that the 180-195 parental region in hPrP(C) makes a strong contribution to the chameleon conformational behavior of the segment corresponding to the full-length alpha2-helix, and could play a role in determining structural rearrangements of the entire globular domain.

[Management of risk of errors in health: which representation for a systemic approach?]

The management of the risk of error in Health currently configures as an institutionalized multi/hetero-professional and "complex" activity. This implicates the need to establish rules that codify the modalities of interaction among the actors, as well as rules of communication, which, defining in a clear and univocal way the terminology used, allow the different actors to understand themselves. The representation of these rules implies a systemic and global conceptual approach in which the attention is moved from "the physician's performance" to the "performance in Health": the whole System must be structured and employed in order to pretend towards a continuous improvement of Quality and Safety.

Ligand migration and binding in the dimeric hemoglobin of Scapharca inaequivalvis

Using Fourier transform infrared (FTIR) spectroscopy combined with temperature derivative spectroscopy (TDS) at cryogenic temperatures, we have studied CO binding to the heme and CO migration among cavities in the interior of the dimeric hemoglobin of Scapharca inaequivalvis (HbI) after photodissociation. By combining these studies with X-ray crystallography, three transient ligand docking sites were identified: a primary docking site B in close vicinity to the heme iron, and two secondary docking sites C and D corresponding to the Xe4 and Xe2 cavities of myoglobin. To assess the relevance of these findings for physiological binding, we also performed flash photolysis experiments on HbICO at room temperature and equilibrium binding studies with dioxygen. Our results show that the Xe4 and Xe2 cavities serve as transient docking sites for unbound ligands in the protein, but not as way stations on the entry/exit pathway. For HbI, the so-called histidine gate mechanism proposed for other globins appears as a plausible entry/exit route as well.

Transient ligand docking sites in Cerebratulus lacteus mini-hemoglobin

The monomeric hemoglobin of the nemertean worm Cerebratulus lacteus functions as an oxygen storage protein to maintain neural activity under hypoxic conditions. It shares a large, apolar matrix tunnel with other small hemoglobins, which has been implicated as a potential ligand migration pathway. Here we explore ligand migration and binding within the distal heme pocket, to which the tunnel provides access to ligands from the outside. FTIR/TDS experiments performed at cryogenic temperatures reveal the presence of three transient ligand docking sites within the distal pocket, the primary docking site B on top of pyrrole C and secondary sites C and D. Site C is assigned to a cavity adjacent to the distal portion of the heme pocket, surrounded by the B and E helices. It has an opening to the apolar tunnel and is expected to be on the pathway for ligand entry and exit, whereas site D, circumscribed by TyrB10, GlnE7, and the CD corner, most likely is located on a side pathway of ligand migration. Flash photolysis experiments at ambient temperatures indicate that the rate-limiting step for ligand binding to CerHb is migration through the apolar channel to site C. Movement from C to B and iron-ligand bond formation involve low energy barriers and thus are very rapid processes in the wt protein.