Modern gas sensing systems based on nanotechnologies may enable reliable and continuous detection of different gaseous compounds to control atmospheric pollutants and human health. Wide bandgap semiconductor nanostructures with their quantum-mechanical properties can affect the features of functional devices. Therefore, the application of semiconductor nanomaterials in the development of chemical gas sensors is of great interest. Highly ordered transition metal oxide nanostructures have been considered as promising materials for applications in chemical gas sensors due to their good chemical stability and functional properties. In this regard, well-ordered and highly aligned titania nanotubes with their superior electron transport properties and large surface area are very attractive structures for the fabrication of gas sensing systems. Herein, we report the preparation and investigation of sensing properties of titania-based nanotubular structures for their application in gas detection devices. We studied the effect of additive materials on the functionalities of nanotubes to optimize their sensing performance. The morphology, structure and composition of prepared materials were examined. The sensing properties of structures were studied towards different gases. We have analyzed the interaction mechanism between the prepared nanotubes and gaseous compounds considering their structural and compositional modifications. The experimental findings demonstrate that the introduction of dopant materials and surface functionalization are very promising strategies to enhance the sensing performance of titania nanotubes.

A compound of great interest to both researchers of medicine, chemistry and psychologists is tyrosine (Tyr), an amino acid synthetized in the body from phenylalanine, because it is the main responsible for the installation of diseases and conditions that grew during the pandemic caused by the new coronavirus Sars- CoV-2. Parkinson's disease, depression, Alzheimer's disease, premenstrual syndrome and ADHD (attention deficit hyperactivity disorder) are just some examples of other clinical manifestations of individuals suffering from a deficit or excess of tyrosine. Sensors and biosensors are state-of-the-art devices, used in various fields of activity, due to the multiple advantages they have: low manufacturing costs, miniaturization and portability, high sensitivity, and fast response. These devices can be successfully applied for rapid and early detection of this amino acid in real samples. In the present study, electrochemical biosensors based on polypyrrole doped with various anionic agents and enzyme laccase were studied by a comparative analysis in order to detect L-Tyrosine (L-Tyr). The methods used for the characterization of these devices were chronoamperometry, cyclic voltammetry and Fourier Transform Infrared Spectroscopy. The results obtained with the novel biosensors showed higher performances than those reported in the literature in the terms of sensitivity, selectivity and detection limit. These validation results demonstrated that L-Tyr can be successfully applied to both pharmaceuticals products and human serum.

Apple juice is a nutritious beverage commonly consumed for its refreshing attributes, taste, flavor, nutritional properties and health benefits; being rich in carbohydrates, minerals, vitamins and many other phytonutrients, it contributes to a good health status, while playing an important role in a wholesome diet. Unfortunately, the temptation for a fast economic gain, lead to food frauds, such adulterations; for juices, adulteration is accomplished usually by practices such as dilution with water, using cheaper ingredients (mainly different combinations of sugar solutions and syrups), addition of peel and/ or pulp wash. This paper presents a method for fast detection of apple juice adulteration based on parallel chromatography, followed by chemometric data analysis. To prove its usefulness, commercial apple juices were obtained from the local supermarkets; after dilution 1/ 10 (v/v) with ultrapure water and filtration through 0.45 mm Millipore membrane filters, chromatographic analyses were performed on a hybrid Shimadzu system, consisting of two Prominence LC-20AP solvent delivery modules, a Prominence DGU 20As online degasser, an automatic sample injector SIL-10AF, an RID-10A differential refractive index detector, a CDD-10Avp dual channel conductivity detector, a Prominence CTO-20A column oven, an FCV-10AH2 valve unit and a Prominence CBM-20A system controller. Isocratic separations were conducted at 40⁰C, using a Universal Cation 7u column for cation analysis, while carbohydrates were separated using an EC 250/4 Nucleodur 100–5 NH₂ RP column; the external standard method was used for quantification. Reference apple juices were obtained from Starkinson and Red-Star apples using a centrifugal juice-extractor; after homogenization, the freshly-made juices were processed as mentioned before. The external standard method was used for quantification, all the samples being analyzed in triplicates; recoveries were established by spiking several samples with known concentrations of analytes. Instrument control, data acquisition and data analysis were accomplished by „LCsolution” software. Multivariate data analysis was completed on autoscaled chromatographic data using Matlab (The Mathworks Inc., USA). The proposed configuration delivered simultaneously the concentrations of sodium, potassium, calcium, magnesium, fructose, glucose and saccharose. Principal component analysis and cluster analysis of the data matrix highlighted four classes of apple juices: juices sweetened with saccharose, juices sweetened with glucose-fructose syrup, genuine apple juices (containing also the laboratory-extracted juices) and adulterated apple juices. Hence, chromatographic analysis in conjunction with multivariate data analysis proved to be appropriate complimentary tools in discriminating between sweetened and non-sweetened apple juices, between genuine and adulterated products - with minimal sample workup, separations being achieved in less than 17 minutes.

The rapid technological advancements in the last decade call for a smart and sustainable lifestyle management with sensors playing a vital role. Electron spin is fast becoming a very useful tool in sensing devices based on spintronics. First-principles calculations play a very important role in the search for materials with high spin polarization that are very desirable for spintronics.

Half-metallic ferromagnetic (HMF) materials demonstrate 100% spin polarization at the Fermi level due to the fact that they have one spin channel metallic with the presence of states at the Fermi level and the other spin channel is semiconducting/insulating; making them promising candidates for spintronic sensing applications.

In this work, the full potential linearized augmented plane wave (FP-LAPW) density Functional Theory (DFT) method is used to calculate the electro- magnetic properties of the transition metal perovskite NbScO₃ with the modified Becke-Johnson (mBJ) approximation for the exchange and correlation. The electronic band structures for the two spin orientations indicates perfect 100% spin polarization for NbScO₃ indicating it to be a HMF with an integer magnetic moment of 2.0 μ_B. The new half metal perovskite shows metallic behavior in the majority spin and semiconducting in the minority spin channel with a large indirect R− Γ band gaps of 3.61eV creating the necessary conditions for spintronics.

Nanoscale delivery systems have been investigated for disease treatment due to their well-recognized advantages, including the sustained delivery of drugs to cells, enhanced therapeutic efficacy, and reduction of undesired effects compared to conventional treatments. The application of nanocarriers in medicine is still hampered by significant experimental challenges, such as the investigation of the drug release profile in living cells rather than in cell medium. Here, we describe a hybrid nanoplatform for monitoring the drug release in colorectal cancer (CRC) cells at a femtogram scale by Surface-Enhanced Raman Scattering (SERS). Specifically, the anticancer drug Galunisertib was encapsulated in porous diatomite nanoparticles (DNPs) decorated by 25 nm gold nanoparticles (AuNPs) and capped by a layer of gelatin¹. The combination of the drug-loading capacity of DNPs with the strong Raman enhancement of molecules close to AuNPs enabled combining therapeutic purposes with label-free intracellular drug monitoring. The hybrid nanoplatform integrated bio-imaging and drug delivery goals without the use of any fluorophore or marker, avoiding fluorescence-quenching issues. Thanks to the strong enhancement provided by the AuNPs, the drug release profile was monitored and quantified by SERS with a femtogram scale resolution. When the gelatin layer was digested by proteases, Galunisertib was released and the SERS spectrum of the drug decreased as well, allowing to quantify the amount of drug released in CRC cells within 48 hours. The results were compared to in vitro investigations performed with spectroscopic techniques, revealing that the gelatin layer caused both a sustained and pH-sensitive release of Galunisertib. The drug release was faster in the acidic microenvironment and slower in the physiological medium. The therapeutic outcomes of the nanoplatform were finally tested in the CRC cell line, revealing that the Galunisertib delivery system improved drug efficacy, reduced its toxicity, offering an alternative administration route for cancer treatment.

Tramontano, C.; Chianese, G.; Terracciano, M.; De Stefano, L.; Rea, I.; "Nanostructured Biosilica of Diatoms: From Water World to Biomedical Applications", Appl. Sci. 2020, 10, 6811. https://doi.org/10.3390/app10196811

In spite of the large number of publications concerning quantitative analysis of metal ions by different electroanalytical techniques, their complete method validation is not frequently carried out. Electrochemists often view the validation procedure as a time consuming novelty and do not give it the scientific value deserved, thus neglecting to undertake the complete validation procedure. They tend to focus on the exceptional feature of the proposed electrochemical method or assembly, without clearly demonstrating its suitability for quantitative purposes. Because of this, the number of routine analyses by electroanalytical methods employed by various laboratories is unfortunately very low, compared with the less cost-effective and sometimes cumbersome atomic adsorption techniques. Thus, here we present the development of the previously obtained modified electrodes based on poly(2,2'-(ethane-1,2-diylbis((2-(azulen-2-ylamino)-2-oxoethyl)azanediyl))diacetic acid, (polyL) [1, 2] to laboratory-scale studies and physically validate the analytical predictions by developing an assembly system made of screen printed modified electrodes (SPEs) with polyL selective complexing polymeric films coupled with a low-cost, small, portable, stand-alone, hand-held, single-technique, potentiostat to analyze the Hg(II) ions content from environmental water samples. The purpose these modified electrodes is to provide real-time reliable information about the chemical composition of its surrounding environment.

Acknowledgments

The authors gratefully acknowledge the financial support of the Romanian National Authority for Scientific Research, UEFISCDI, under grant PN-III-P2-2.1-PED-2019-0730, contract no. 293PED/2020.

References

1.G.-O. Buica, I.-G. Lazar, L. Birzan, C. Lete, M. Prodana, M. Enachescu, V. Tecuceanu, A.B. Stoian, E.-M. Ungureanu, Azulene-ethylenediaminetetraacetic acid: A versatile molecule for colorimetric and electrochemical sensors for metal ions, ElectrochimicaActa 263 (2018) 382-390.

2.G.-O. Buica, A.A. Ivanov, I.-G. Lazar, G.-L. Tatu (Arnold), C. Omocea, L. Birzan, E.-M. Ungureanu, Colorimetric and voltammetric sensing of mercury ions using 2,2′-(ethane-1,2-diylbis((2-(azulen-2-ylamino)-2-oxoethyl)azanediyl)) diacetic acid, J.Electroanal.Chem., 849 (2019) 113351.

Near infrared spectroscopy (NIRS) is nowadays a highly-appreciated quality control technique, due to its numerous advantages, such as: non-demanding sample preparation (even no sample preparation)/ easy to use/ robust/ environmental – friendly/ short analysis time. Hence, it gained an important position in laboratories, being more and more used in food industry for characterizing the quality of both food products and raw materials. There are numerous researches dealing with the quality control of agricultural products, among which there are also the seeds of crop plants; the improvement in both biological and nutritional properties was and continues to be a major concern for breeding programs and in this context NIRS can bring a valuable contribution, by providing relevant data on nutritional quality in a fast way. This paper is a case study in which soybeans genotypes were tested in order to find both the quality attributes and the best candidates for the developing of new varieties. 72 soybean cultivars from the Research & Development Station for Agriculture, Turda were analyzed using a Tango spectrometer (Bruker, Germany). The instrument was calibrated to provide data for intact grains, on: moisture, fat, proteins, as well as for several fatty acids: stearic, oleic, linoleic and linolenic. Data were further subjected to chemometric analysis, which was accomplished using Matlab (MathWorks Inc., USA) ; principal component analysis was accomplished on autoscaled preprocessed data, using six variables (the measured parameters), reveling both the genotypes with the best quality attributes and similarities between the studied ones. The variability of the chemical composition within the analyzed germoplasm indicates that there is potential for successful improvement of the quality parameters in soybeans. This study can provide a framework for new applied researches for both plant breeding programs as well as a new method for quality control of soybeans’ products; the method is advantageous since the analyzed seeds can be used further, being not destroyed for analysis.

In this work, an optical fiber sensor based on the Localized Surface Plasmon Resonance (LSPR) phenomenon is presented as a powerful tool for the detection of heavy metals (Hg²⁺) in the field of environmental applications [1], [2]. The resultant sensing film has been fabricated using a nanofabrication process, known as Layer-by-Layer Embedding (LbL-E) technique [3], which makes possible a successful immobilization of metallic nanoparticles into a polymeric matrix. In this sense, both silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) have been synthesized using a synthetic chemical protocol as a function of a strict control of three main parameters such as polyelectrolyte concentration, loading agent and reducing agent, respectively. The use of metallic nanostructures as sensing materials is of great interest because well-located absorption peaks associated to their LSPR are obtained at 420 nm (AgNPs) and 530 nm (AuNPs), respectively [4]. Both plasmonic peaks provide a stable real-time references that can be extracted from the spectral response of the optical fiber sensor, giving a reliable monitoring of the Hg²⁺ concentration. An exhaustive study about the most appropriate deposition parameters (mostly pH and thickness) has been evaluated in order to obtain a more detailed analysis of the sensing spectral response. To sum up, this is the first time that an optical fiber sensor based on two different LSPR sensing signals has been presented for Hg²⁺ detection in the bibliography.

[1] X. Zhong, L. Ma G. Yin, M. Gan, and Y.Wei, “Hg²⁺ Optical Fiber Sensor Based on LSPR with PDDA Templated AuNPs and CS/PAA Bilayers,” Applied Sciences, vol. 10, no. 14, 2020.

[2] M. E. Martínez-Hernández, J. Goicoechea, and F. J. Arregui, “Hg²⁺ optical fiber sensor based on LSPR generated by gold nanoparticles embedded in LBL nano-assembled coatings,” Sensors (Switzerland), vol. 19, no. 22, 2019.

[3] P. J. Rivero, J. Goicoechea, I. R. Matias, and F. J. Arregui, “A comparative study of two different approaches for the incorporation of silver nanoparticles into layer-by-layer films,” Nanoscale Res. Lett., vol. 9, no. 1, pp. 1–11, 2014.

[4] J. Goicoechea, P. J. Rivero, S. Sada, and F. J. Arregui, “Self-Referenced Optical Fiber Sensor for Hydrogen Peroxide Detection based on LSPR of Metallic Nanoparticles in Layer-by-Layer Films,” Sensors, vol. 19, no. 18, p. 3872, 2019.

The need to perform in-situ sensing measurements leads to the development of innovative and smart field-portable devices. The advantages of such systems are remarkable since they are mainly battery-powered, lightweight and easy to carry and keep. Moreover, field-portable devices are easy to use and able to give fast sensing responses.

In the last years, many efforts have been made in the development of new performing systems and the advantageous use of nanofibrous materials was assessed. To this purpose, the electrospinning has been recognized as the most powerful and facile technique for generating uniform nanofibers with controlled dimension and morphology. When conductive polymers are electrospun, very interesting electrical properties can be obtained along with the well-known ones typical of nanofibers. Among these polymers, polyaniline has been extensively used.

In this work an innovative hybrid material based on polyaniline/polyvinyl acetate/graphene oxide nanofibers was developed and tested as a sensor toward the detection of contaminants in aqueous media. Nanofibers, in the form of a compact mat, were deposited onto a support with suitable electrical contacts. Measurements were performed exploiting the excellent electrical properties of the realized nanofibers in both direct and alternating current. When direct current was used, the change in nanofibers resistance value was registered upon exposure to contaminated aqueous solutions and used to determine the presence or absence of contaminants; whereas when tests in alternating current were performed, quantitative determination of single species in contaminated solutions was also possible.

In this way, by the integration of the two different measurement methodologies, an opportunely designed multifunctional portable device will be developed for both qualitative and quantitative contaminants determinations.

Cardiovascular diseases (CVD) are considered one of the leading causes of death worldwide. To prevent cardiovascular complications and further loss of life oral anticoagulants (e.g., warfarin and clopidogrel) are frequently prescribed to patients. Nevertheless, both therapeutic agents present narrow therapeutic windows with well-documented health risks. Some of these dose-responses are a result of specific single-nucleotide polymorphism (SNP) genetic variations present in a patient’s DNA. Among them, determined SNP in the cytochrome P4502C9 (CYP2C9), namely CYPC9*2 and CYP2C*3, and the SNP 1639G>A in the vitamin K epoxide reductase complex subunit 1 (VKORC1) genes have both been identified as dose-response altering SNP. Therefore, the need for a rapid, selective, low-cost and in real time detection device is crucial before prescribing any anticoagulants.

This work addresses the development of a disposable electrochemical genosensor capable of detecting SNP in the CYPC9*3 allele. Analysing public databases, two specific 78 bp DNA probes; one with the adenine (TA) and another with the cytosine (TC) SNP genetic variation were selected and designed. The genosensor methodology implied the immobilization of a mixed self-assembled monolayer (SAM) linear CYPC9*3 DNA-capture probe and mercaptohexanol (MCH) onto screen-printed gold electrodes (SPGE). To improve the genosensor’s selectivity and avoid strong secondary structures, that could hinder the hybridization efficiency, a sandwich format of the CYPC9*3 allele was designed using a complementary fluorescein isothiocyanate-labelled signalling DNA probe and enzymatic amplification of the electrochemical signal. Chronoamperometry measurements were carried out obtaining a concentration range from 0.015 to 1.0 nM for both TA and TC SNP target probes. Analysing the results, the developed genosensor could discriminate between the two SNP probes.