Myoglobin-silver reduced graphene oxide nanocomposite stochastic biosensor for the determination of luteinizing hormone and follicle-stimulating hormone from saliva samples.

A silver reduced graphene oxide (Ag-rGO) nanocomposite paste was prepared for the assay of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in children's saliva. The paste was modified with a solution of myoglobin (Myb) to form the stochastic biosensor, to improve the sensitivity of the method. The Ag-rGO powder and Myb-Ag-rGO paste were morphologically and structurally characterized by SEM, TEM and XRD measurements. For the molecular recognition of the hormones, the biosensor based on Myb-Ag-rGO reached determination limits of 8.5 × 10-3 UI L-1 (2.0 × 10-12 g/mL) for luteinizing hormone and 1.4 × 10-2 UI L-1 (1.0 × 10-12 g/mL) for follicle-stimulating hormone. The determination of both hormones in saliva samples collected from children was done with high reliability. Graphical Abstract.

Gold nanoparticle-graphene quantum dots nanozyme for the wide range and sensitive electrochemical determination of quercetin in plasma droplets.

A gold nanoparticle/graphene quantum dots (AuNP/GQD) nanozyme-modified screen-printed carbon electrode (SPCE) was developed for fast and ultrasensitive determination of quercetin by square-wave voltammetry. The nanosensing device was inserted in miniaturized equipment. Under the optimal experimental conditions, a good linear relationship between oxidation peak current and concentration of quercetin within a very wide range of 1.0 × 10-10 to 1.0 × 10-3 mol L-1 was obtained, with a very low limit of detection of 3.3 × 10-11 mol L-1. To prove the performance of the method, the reproducibility was evaluated and the RSD values were lower than 5.3% and 5.1% for the intra-day and inter-day measurements, respectively. The method was applied to the sensitive determination of quercetin in human plasma droplets with recovery rates of 92.6 to 101.7%.Graphical abstract.

Molecular Recognition of Nitrites and Nitrates in Water Samples Using Graphene-Based Stochastic Microsensors.

Two stochastic microsensors based on graphene powders and protoporphyrin IX were proposed for the simultaneous assay of nitrite and nitrate in water samples. The proposed microsensors can provide a fast screening of water samples with a qualitative and quantitative analysis for NO2- and NO3- at very low concentration levels. The linear concentration ranges were wide, covering clean as well as polluted waters. The results provided by the stochastic microsensors were in agreement with those obtained by utilization of standard methods, recoveries higher than 99.00% and RSD lower than 1.00%, proving that the method can be reliable used for simultaneous assay of NO2- and NO3- in water samples.

Molecular recognition of IL-8, IL-10, IL-12, and IL-15 in biological fluids using phthalocyanine-based stochastic sensors.

Two stochastic sensors based on the modification of graphite paste with the complexes formed by phthalocyanine (PhCN) with Ni and Cu were designed and used for molecular recognition of IL-8, IL-10, IL-12, and IL-15. The four interleukins were recognized according to their signatures-called toff (qualitative parameter) from the diagrams obtained after measurements. The limit of determination for IL-8 was 1 × 10-4µg mL-1 when both stochastic sensors were used; for IL-10, the determination limit was 4.5 × 10-4µg mL-1 for the Ni complex-based sensor, and 4.5 × 10-7µg mL-1 for the Cu complex-based sensor, respectively; for IL-12, the determination limit was 5 × 10-4µg mL-1 for the Ni complex-based sensor, and 5 × 10-7µg mL-1 for the Cu complex-based sensor, respectively; while for IL-15, the determination limit was 5 × 10-5µg/mL for the Ni complex-based sensor, and 5 × 10-5µg/mL for the Cu complex-based sensor, respectively. The stochastic method used was validated using the following biological fluids: nasal lavage, saliva, serum, and whole blood. Graphical abstract ᅟ.

Pattern recognition of 8-hydroxy-2'-deoxyguanosine in biological fluids.

8-Hydroxy-2'-deoxyguanosine (8-OHdG), a product of oxidative DNA damage, which has been used as a sensitive and reliable marker of oxidative stress and carcinogenesis, is found in high levels in biological fluids of leukemia patients. A reliable screening method based on pattern recognition of 8-OHdG using stochastic sensors designed with graphene materials decorated with nanoparticles of TiO2Ag or TiO2Au was developed. 5,10,15,20-Tetraphenyl-21H,23H porphyrin (P), 2,6-bis((E)-2-(furan-2-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyridine (Py1), and 2,6-bis((E)-2-(thiophen-3-yl)vinyl)-4-(4,6,8-trimethylazulen-1-yl)pyridine (Py2) were used as modifiers of the graphene paste in the design of sensors. The screening method used for pattern recognition was developed for two pH values accordingly with the nature of the biological fluid to be screened: pH = 3.02 for urine samples and pH = 7.49 for whole blood samples. High sensitivities and low limits of determination for 8-OHdG obtained at both pH values favored the early detection of leukemia. Recoveries over 98.00% with RSD (%) values lower than 1.00% proved the reliability of the proposed screening method. Graphical abstract Graphene based sensors detect 8-hydroxy-2'-deoxyguanosine in biological fluids.

Multimode sensors as new tools for molecular recognition of testosterone, dihydrotestosterone and estradiol in children's saliva.

Increased levels of testosterone (T2 ), dihydrotestosterone (DHT) and estradiol (E2 ) in children may be responsible for their early/delayed puberty and obesity conditions. Therefore, multimode sensors based on carbon matrices, such as graphite, graphene, fullerene C60 and multiwall carbon nanotubes modified with maltodextrin, were designed to assess reliably T2 , DHT and E2 in children saliva. The modes used for the assay of hormones were stochastic mode (for qualitative and quantitative determination of hormones) and differential pulse voltammetry mode (for quantitative determination of hormones). The advantage of this type of sensors, for hormone analysis, is their possibility to reach low concentration levels- are placed for children saliva under the detection limit of standard methods (e.g. ELISA used for the determination of these hormones in saliva). This made the multimode sensors an excellent tool for clinical analysis and especially for determination of substances of clinical importance in saliva samples. The proposed method is fast and simple, and no sampling of saliva is required.

Advanced Methods for the Analysis of Testosterone.

Testosterone is the principal endogenous androgenic-anabolic steroid in humans. The levels of testosterone in the human body are correlated with many hormonal disorders (hypogonadism, impotence, etc) mostly in men, and with many types of diseases such as: prostate cancer, metabolic syndrome, obesity, cardiovascular diseases and so on. Testosterone is extensively used among sportsmen willing to increase strength, aggressiveness, and recovery; making it the most commonly reported substance in steroid abuse. Fast, easy and cheap methods for the evaluation of testosterone are extremely needed in clinics and hospitals. This review is dedicated to surveying recent determination methods of testosterone from different biological samples such as: serum, saliva, plasma, urine or fingernail samples. After a brief description of the role of this steroid hormone in the biomedical field, various types of determination methods are described. The most important methods are immunoassays, liquid chromatography tandem massspectrometry and electrochemical methods. Different types of sensors were designed for the rapid assessment of testosterone: immunosensors, biosensors, stochastic or multimode sensors. One can conclude that to date, the available methods of analysis can cover a wide concentration range, able to detect testosterone from children`s saliva, where the levels are the lowest (using stochastic sensors), to whole blood, where electrochemical, immunological and chromatographic methods can be used.

Salivary biomarkers of inflammation in systemic lupus erythematosus.

Saliva is currently used as a reliable diagnostic fluid in a wide range of local and systemic diseases. However, the link between salivary diagnosis and the inflammatory process in autoimmune diseases has not yet been explored. The aim of our study is to assess possible correlations between salivary inflammatory markers and systemic lupus erythematosus (SLE). Patients fulfilling the Systemic Lupus International Collaborating Clinics (SLICC) diagnosis criteria were included. Salivary and serum levels of interleukin-6 (IL-6), leptin, monocyte chemoattractant protein-1 (MCP-1) and plasminogen activator inhibitor-1 (PAI-1) were determined using stochastic sensors. Serum leptin and IL-6 had significantly higher levels in SLE patients compared to non-SLE. Also, salivary IL-6 levels highly correlated with the serum IL-6 levels. A positive correlation was found between salivary and serum levels of IL-6, signaling salivary IL-6 as a reliable marker for assessing the inflammation process in SLE.

Pattern recognition of monocyte chemoattractant protein-1 (MCP-1) in whole blood samples using new platforms based on nanostructured materials.

Four stochastic microsensors based on nanostructured materials (graphene, maltodextrin (MD), and diamond) integrated in miniaturized platforms were proposed. Monocyte chemoattractant protein-1 (MCP-1) is a pro-inflammatory cytokine whose main function is to regulate cell trafficking. It is correlated with the incidence of cardiovascular diseases and obesity, and was used as the model analyte in this study. The screening of whole blood samples for MCP-1 can be done for concentrations ranging from 10(-12) to 10(-8) g mL(-1). The method was used for both qualitative and quantitative assessments of MCP-1 in whole blood samples. The lowest quantification limits for the assay of MCP-1 (1 pg mL(-1)) were reached when the microsensors based on protoporphyrin IX/Graphene-Au-3 and on MD/Graphene were employed in the platform design.

Pattern recognition of estradiol, testosterone and dihydrotestosterone in children's saliva samples using stochastic microsensors.

Stochastic microsensors based on diamond paste and three types of electroactive materials (maltodextrin (MD), α-cyclodextrin (α-CD) and 5,10,15,20-tetraphenyl-21H,23H porphyrin (P)) were developed for the assay of estradiol (E2), testosterone (T2) and dihydrotestosterone (DHT) in children's saliva. The main advantage of utilization of such tools is the possibility to identify and quantify all three hormones within minutes in small volumes of childen's saliva. The limits of quantification obtained for DHT, T2, and E2 (1 fmol/L for DHT, 1 pmol/L for T2, and 66 fmol/L for E2) determined using the proposed tools allows the utilization of these new methods with high reliability for the screening of saliva samples from children. This new method proposed for the assay of the three hormones overcomes the limitations (regarding limits of determination) of ELISA method which is the standard method used in clinical laboratories for the assay of DHT, T2, and E2 in saliva samples. The main feature of its utilization for children's saliva is to identify earlier problems related to early puberty and obesity.