Synthesis, characterization and deepening in the comprehension of the biological action mechanisms of a new nickel complex with antiproliferative activity

Thiosemicarbazones are versatile organic compounds that present considerable pharmaceutical interest because of a wide range of properties. In our laboratory we synthesised some new metal-complexes with thiosemicarbazones derived from natural aldehydes which showed peculiar biological activities. In particular, a nickel complex [Ni(S-tcitr)(2)] (S-tcitr=S-citronellalthiosemicarbazonate) was observed to induce an antiproliferative effect on U937, a human histiocytic lymphoma cell line, at low concentrations (IC(50)=14.4microM). Therefore, we decided to study the interactions of this molecule with various cellular components and to characterise the induced apoptotic pathway. Results showed that [Ni(S-tcitr)(2)] causes programmed cell death via down-regulation of Bcl-2, alteration of mitochondrial membrane potential and caspase-3 activity, regardless of p53 function. The metal complex is not active on G(0) cells (i.e. fresh leukocytes) but is able to induce perturbation of the cell cycle on stimulated lymphocytes and U937 cells, in which a G(2)/M block was detected. It reaches the nucleus where it induces, at low concentrations (2.5-5.0microM), DNA damage, which could be partially ascribed to oxidative stress. [Ni(S-tcitr)(2)] is moreover able to strongly reduce the telomerase activity. Although the biological target of this metal complex is still unknown, the reported data suggest that [Ni(S-tcitr)(2)] could be a good model for the synthesis of new metal thiosemicarbazones with specific biological activity.

Thioamido Coordination in a Thioxo-1,2,4-triazole Copper(II) Complex Enhances Nonapoptotic Programmed Cell Death Associated with Copper Accumulation and Oxidative Stress in Human Cancer Cells

The thioamido function of [CuCl2(1H)]Cl (2) (1=4-amino-1,4-dihydro-3-(2-pyridyl)-5-thioxo-1,2,4-triazole), a cytotoxic copper complex, was converted into thioether moieties, leading to the synthesis of [CuCl2(3)]2 (4) and [CuCl2(5)] (6) (3=6-methyl-3-pyridin-2-yl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine; 5=4-amino-5-ethylthio-3-(2-pyridyl)-1,2,4-triazole). These complexes were structurally characterized, and their stability constants, along with their biological activity, were determined. 4 and 6 were slightly less stable and significantly less active than 2. However, as 2, both complexes induced nonapoptotic vacuolar cell death. Copper uptake, investigated in both 2-sensitive and -insensitive cell types, was markedly higher in sensitive cells where it was associated with an increase in oxidized glutathione. These data suggest that the thioamido function enhances the cytotoxicity of copper complexes in cancer cells promoting the accumulation of the metal and its interaction with cell thiols.

A Folding-Based Electrochemical Aptasensor for the Single-Step Detection of the SARS-CoV-2 Spike Protein

Efficient and timely testing has taken center stage in the management, control, and monitoring of the current COVID-19 pandemic. Simple, rapid, cost-effective diagnostics are needed that can complement current polymerase chain reaction-based methods and lateral flow immunoassays. Here, we report the development of an electrochemical sensing platform based on single-walled carbon nanotube screen-printed electrodes (SWCNT-SPEs) functionalized with a redox-tagged DNA aptamer that specifically binds to the receptor binding domain of the SARS-CoV-2 spike protein S1 subunit. Single-step, reagentless detection of the S1 protein is achieved through a binding-induced, concentration-dependent folding of the DNA aptamer that reduces the efficiency of the electron transfer process between the redox tag and the electrode surface and causes a suppression of the resulting amperometric signal. This aptasensor is specific for the target S1 protein with a dissociation constant (K_D) value of 43 ± 4 nM and a limit of detection of 7 nM. We demonstrate that the target S1 protein can be detected both in a buffer solution and in an artificial viral transport medium widely used for the collection of nasopharyngeal swabs, and that no cross-reactivity is observed in the presence of different, non-target viral proteins. We expect that this SWCNT-SPE-based format of electrochemical aptasensor will prove useful for the detection of other protein targets for which nucleic acid aptamer ligands are made available.

Multiplex liquid chromatography-tandem mass spectrometry for the detection of wheat, oat, barley and rye prolamins towards the assessment of gluten-free product safety

Celiac patients should feel confident in the safety of foods labelled or expected to be gluten-free. In this context, a targeted proteomic approach based on liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) technique was proposed to assess the presence of celiotoxic cereals, namely wheat, oats, barley and rye, in raw and processed food products. To this aim, unique marker peptides were properly selected in order to distinguish between the different cereal types. A revised cocktail solution based on reducing and denaturing agents was exploited for prolamin extraction from raw and processed food; in addition, defatting with hexane was carried out for sample clean-up, allowing to largely reduce problems related to matrix effect. Method validation on fortified rice flour showed good analytical performance in terms of sensitivity (limits of detection in the 2-18 mg kg(-1) range). However, poor trueness was calculated for self-made incurred bread (between 3 and 30% depending on the peptide), probably due to baking processes, which reduce gluten extractability. Thus, it is evident that in the case of processed foods further insights into sample treatment efficiency and reference materials for protein calibration are required to obtain accurate gluten determination. Finally, the developed method was applied for the analysis of market food products, offering the possibility to discriminate among cereals, with good agreement with labelled ingredients for gluten-containing foodstuffs.

Competitive amperometric immunosensor for determination of p53 protein in urine with carbon nanotubes/gold nanoparticles screen-printed electrodes: A potential rapid and noninvasive screening tool for early diagnosis of urinary tract carcinoma

Since p53 protein has become recognized biomarker for both diagnostic and therapeutic purposes in oncological diseases with particular relevance for bladder cancer, it is highly desirable to search for a novel sensing tool for detecting the patient's p53 level at the early stage. Here we report the first study on the development and validation of a novel disposable competitive amperometric immunosensor for determination of p53 protein at subnanomolar levels, based on p53 immobilization on gold nanoparticles/carbon nanotubes modified screen-printed carbon electrodes. The assay protocol requires the use of single anti-p53 mouse monoclonal antibody (DO-7 clone), able to recognize both wild-type and mutant p53. The developed immunosensor as well as the protocol of the electrochemical immunoassay were optimized by means of an experimental design procedure to assess the suitability of the device to be validated and applied for the determination of p53 in untreated and undiluted urine samples. It was found that the developed competitive immunodevice was able to achieve wide linear range detection of wild-type p53 from 20 pM to 10 nM with a low detection limit of 14 pM in synthetic urine samples, suggesting the sensor's capability of working in a complex sample matrix. The excellent performance results also in terms of selectivity, trueness and precision, coupled with the advantages of an easy preparation and low-cost assay in contrast to other methods which require very complex, time-consuming and costly nanostructured architectures, makes the developed competitive immunosensor an analytically robust diagnostic tool, valuable for implementation of screening and follow-up programs in patients with urologic malignancies.

Calixarene--poly(dithiophene)-based chemically modified electrodes

The stepwise synthesis of cone and partial cone 1,3-bridged n-propoxy-calix[4]crown ethers ("monomers" 2 and 3) with an electropolymerizable 2,2'-dithiophene-3-yl-hexylene functionality at the lower rim, is described. The potential of 2 and 3 as sensing agents for alkali metal ions was investigated by 1H NMR titration experiments with NaSCN and KSCN. The results obtained have confirmed that the presence of the heterocyclic subunit does not affect the well-known size-selectivity observed with calix[4]crowns. Monomers 2 and 3 were electropolymerized (Pt as a working electrode, CH2Cl2/CH3CN, Bu4NPF6) to produce the title chemically modified electrodes (CMEs). After coating with a PVC membrane containing a lipophylic cation exchanger, CMEs based on calix[4]-crown-5 2b (cone) and 3b (partial cone) were tested for the potentiometric recognition of alkali metal ions in aqueous solution. In agreement with NMR titration studies, a satisfactory potentiometric response in terms of K+/Na+ selectivity was obtained only with CME 2b (pK(K/Na) 1.51). The amperometric responses of PVC-uncoated CMEs were studied by cyclic voltammetry (CV) experiments in CH3CN solution. High Na- selectivity was found with the CME based on partial cone calix[4]crown-4 3a, and frequency response analysis (FRA) measurements support this finding.

Novel amperometric genosensor based on peptide nucleic acid (PNA) probes immobilized on carbon nanotubes-screen printed electrodes for the determination of trace levels of non-amplified DNA in genetically modified (GM) soy

A novel amperometric genosensor based on PNA probes covalently bound on the surface of Single Walled Carbon Nanotubes - Screen Printed Electrodes (SWCNT-SPEs) was developed and validated in samples of non-amplified genomic DNA extracted from genetically modified (GM)-Soy. The sandwich assay is based on a first recognition of a 20-mer portion of the target DNA by a complementary PNA Capture Probe (CP) and a second hybridization with a PNA Signalling Probe (SP), with a complementary sequence to a different portion of the target DNA. The SP was labelled with biotin to measure current signal by means of a final incubation of an Alkaline Phosphatase-streptavidin conjugate (ALP-Strp). The electrochemical detection was carried out using hydroquinone diphosphate (HQDP) as enzymatic substrate. The genoassay provided a linear range from 250 pM to 2.5 nM, LOD of 64 pM and LOQ of 215 pM Excellent selectivity towards one base mismatch (1-MM) or scrambled (SCR) sequences was obtained. A simple protocol for extraction and analysis of non-amplified soybean genomic DNA without sample treatment was developed and validated. Our study provides insight into how the outstanding recognition efficiency of PNAs can be combined with the unique properties of CNTs in terms of signal response enhancement for direct detection of genomic DNA samples at the level of interest without previous amplification.

New competitive dendrimer-based and highly selective immunosensor for determination of atrazine in environmental, feed and food samples: the importance of antibody selectivity for discrimination among related triazinic metabolites

A new voltammetric competitive immunosensor selective for atrazine, based on the immobilization of a conjugate atrazine-bovine serum albumine on a nanostructured gold substrate previously functionalized with poliamidoaminic dendrimers, was realized, characterized, and validated in different real samples of environmental and food concern. Response of the sensor was reliable, highly selective and suitable for the detection and quantification of atrazine at trace levels in complex matrices such as territorial waters, corn-cultivated soils, corn-containing poultry and bovine feeds and corn flakes for human use. Selectivity studies were focused on desethylatrazine, the principal metabolite generated by long-term microbiological degradation of atrazine, terbutylazine-2-hydroxy and simazine as potential interferents. The response of the developed immunosensor for atrazine was explored over the 10(-2)-10(3) ng mL(-1) range. Good sensitivity was proved, as limit of detection and limit of quantitation of 1.2 and 5 ng mL(-1), respectively, were estimated for atrazine. RSD values <5% over the entire explored range attested a good precision of the device.

Synthesis, Structure, and Electrochemical Properties of Copper(I) Complexes with S/N Homoscorpionate and Heteroscorpionate Ligands

Dinuclear Cu(I) complexes with bifunctionalized homoscorpionate ligands, hydrotris(thioxotriazolyl)borato [Li(Tr(Me,o)(-)(Py)) (1) and Li(Tr(Mes,Me)) (2)], and the heteroscorpionate ligand hydro[bis(thioxotriazolyl)-3-(2-pyridyl)pyrazolyl]borato [K(Br(Mes)pz(o)(-)(Py))] (3) were synthesized and crystallographically characterized. The complexes [Cu(Tr(Mes,Me))](2) (4) and [Cu(Tr(Me,o)(-)(Py))](2) (5) exhibit a similar coordination geometry where every metal is surrounded by three thioxo groups in a trigonal arrangement. The presence of a [B-H...Cu] three-center-two-electron interaction in both compounds causes the overall coordination to become tetrahedrally distorted (S(3)H coordination for each metal). The complex [Cu(Br(Mes)pz(o)(-)(Py))](2) (6) presents a trigonal geometry in which the metals interact with two thioxo groups and a bridging pyrazolyl nitrogen atom. A weak contact with a pyridine nitrogen atom completes the coordination of the metals (S(2)N,N' coordination for each metal). [Cu(Tr(Mes,Me))](2), [Cu(Tr(Me,o)(-)(Py))](2), and [Cu(Br(Mes)pz(o)(-)(Py))](2) exhibit fluxional behavior in solution as evidenced by variable-temperature NMR spectroscopy, and for 5 and 6 two species in equilibrium [in the ratio 2/1 for 5 (CDCl(3)) and 3/2 for 6 (CD(2)Cl(2))] are distinguishable in the (1)H NMR spectra at 270 K. 2D-NOESY spectra recorded at 270 K assisted in the attribution of solution molecular geometries for each isomer of 5 and 6. The free energy of activation (DeltaG()(Tc)) was determined for both equilibria from the evaluation of the coalescence temperature. DFT calculations were performed to describe plausible molecular geometry for the minor isomer of 5 and 6 and to propose a possible mechanism of interconversion between major and minor isomers. Cyclic voltammograms were recorded in CH(2)Cl(2) (3 and 6) or CH(2)Cl(2)/CH(3)CN (1/1, v/v) (2, 4, and 5) solutions using 0.1 M TBAHFP or TBAOTf as supporting electrolytes. [Cu(Tr(Mes,Me))](2), [Cu(Tr(Me,o)(-)(Py))](2), and [Cu(Br(Mes)pz(o)(-)(Py))](2) exhibit a quasi-reversible Cu(I)/Cu(II) redox behavior with E(pa) = +719 mV and E(pc) = +538 mV for 4, E(pa) = +636 mV and E(pc) = -316 mV for 5, and E(pa) = +418 mV and E(pc) = -319 mV for 6.

Competitive immunosensor based on gliadin immobilization on disposable carbon-nanogold screen-printed electrodes for rapid determination of celiotoxic prolamins

The first competitive disposable amperometric immunosensor based on gliadin-functionalized carbon/nanogold screen-printed electrodes was developed for rapid determination of celiotoxic prolamins. To date, no competitive spectrophotometric or electrochemical immunoassays have yet been successfully applied to gluten detection in processed food samples, which require the use of complex prolamin extraction solutions containing additives with denaturing, reducing and disaggregating functions. Thus, in this work, great effort was put into the optimization and performance evaluation of the immunosensor in terms of suitability as a screening tool for analysis of cereal-based food samples. For this purpose, aqueous ethanol or complex extraction mixtures, as the patented Cocktail Solution®, were proved effective in the extraction of gliadin. Good sensitivity was achieved after optimization of the immunocompetitive assay, giving limit of detection and limit of quantitation of 8 and 22 ng/ml of gliadin, respectively, for ethanol extracts. The immunosensor was proved to be suitable also for samples extracted with Cocktail Solution® after a proper dilution. Analysis of real samples of different flours proved the suitability of the immunosensing device as a powerful tool for safety assessment of raw materials used for the formulation of dietary products for celiac disease patients. This immunosensor combines good analytical performance using a very simplified set-up protocol with suitability for rapid screening analysis performed using inexpensive and portable instrumentation. Graphical abstract Depiction of the development and working principle of the competitive immunosensor.

A Self-Calibrating IoT Portable Electrochemical Immunosensor for Serum Human Epididymis Protein 4 as a Tumor Biomarker for Ovarian Cancer

Nowadays, analytical techniques are moving towards the development of smart biosensing strategies for the point-of-care accurate screening of disease biomarkers, such as human epididymis protein 4 (HE4), a recently discovered serum marker for early ovarian cancer diagnosis. In this context, the present work represents the first implementation of a competitive enzyme-labelled magneto-immunoassay exploiting a homemade IoT Wi-Fi cloud-based portable potentiostat for differential pulse voltammetry readout. The electrochemical device was specifically designed to be capable of autonomous calibration and data processing, switching between calibration, and measurement modes: in particular, firstly, a baseline estimation algorithm is applied for correct peak computation, then calibration function is built by interpolating data with a four-parameter logistic function. The calibration function parameters are stored on the cloud for inverse prediction to determine the concentration of unknown samples. Interpolation function calibration and concentration evaluation are performed directly on-board, thus reducing the power consumption. The analytical device was validated in human serum, demonstrating good sensing performance for analysis of HE4 with detection and quantitation limits in human serum of 3.5 and 29.2 pM, respectively, reaching the sensitivity that is required for diagnostic purposes, with high potential for applications as portable and smart diagnostic tool for point-of-care testing.