The influence of advanced materials on the analytical performance of semiconductor-based gas sensors.

Chemiresistive gas sensors are metal oxide-based sensors that have received significant attention in different fields. Ambient gas sensors are especially important in the fabrication of wearable probes for the real-time detection of biomarkers in human body samples. Usually, room temperature sensors are affordable due to their low power consumption, resulting in simple instrumentation and maintenance. To fabricate versatile gas sensors, i.e. sensitive, selective, ambient temperature operating gas sensors, and improve the sensing performance of the traditionally used sensor, new materials play an important role. In other words, new advanced materials are essential for designing and fabricating new gas sensors. Hence, in this review, the application and impact of new advanced materials in the fabrication of reliable gas sensors are discussed in detail. Special emphasis is given to the effect of new materials in the fabrication of room-temperature operating systems. Finally, future research outlook and possible challenges that may be encountered by reliable gas sensors are also explained.

A new method for investigating bioequivalence of inhaled formulations: A pilot study on salbutamol.

Purpose: An efficient, cost-effective and non-invasive test is required to overcome the challenges faced in the process of bioequivalence (BE) studies of various orally inhaled drug formulations. Two different types of pressurized meter dose inhalers (MDI-1 and MDI-2) were used in this study to test the practical applicability of a previously proposed hypothesis on the BE of inhaled salbutamol formulations. Methods: Salbutamol concentration profiles of the exhaled breath condensate (EBC) samples collected from volunteers receiving two inhaled formulations were compared employing BE criteria. In addition, the aerodynamic particle size distribution of the inhalers was determined by employing next generation impactor. Salbutamol concentrations in the samples were determined using liquid and gas chromatographic methods. Results: The MDI-1 inhaler induced slightly higher EBC concentrations of salbutamol when compared with MDI-2. The geometric MDI-2/MDI-1 mean ratios (confidence intervals) were 0.937 (0.721-1.22) for maximum concentration and 0.841 (0.592-1.20) for area under the EBC-time profile, indicating a lack of BE between the two formulations. In agreement with the in vivo data, the in vitro data indicated that the fine particle dose (FPD) of MDI-1 was slightly higher than that for the MDI-2 formulation. However, the FPD differences between the two formulations were not statistically significant. Conclusion: EBC data of the present work may be considered as a reliable source for assessment of the BE studies of orally inhaled drug formulations. However, more detailed investigations employing larger sample sizes and more formulations are required to provide more evidence for the proposed method of BE assay.

Comparative Drug Solubility Studies Using Shake-Flask Versus a Laser-Based Robotic Method.

Drug solubility is of central importance to the pharmaceutical sciences, but reported values often show discrepancies. Various factors have been discussed in the literature to account for such differences, but the influence of manual testing in comparison to a robotic system has not been studied adequately before. In this study, four expert researchers were asked to measure the solubility of four drugs with various solubility behaviors (i.e., paracetamol, mesalazine, lamotrigine, and ketoconazole) in the same laboratory with the same instruments, method, and material sources and repeated their measurements after a time interval. In addition, the same solubility data were determined using an automated laser-based setup. The results suggest that manual testing leads to a handling influence on measured solubility values, and the results were discussed in more detail as compared to the automated laser-based system. Within the framework of unavoidable uncertainties of solubility testing, it is a possibility to combine minimal experimental testing that is preferably automated with mathematical modeling. That is a practical suggestion to support future pharmaceutical development in a more efficient way.

A colorimetric nanoprobe based on dynamic aggregation of SDS-capped silver nanoparticles for tobramycin determination in exhaled breath condensate.

A colorimetric nanoprobe was developed for the quantification of tobramycin in exhaled breath condensate (EBC). The nanoprobe consists of silver nanoparticles (Ag NPs) modified with sodium dodecyl sulfate (SDS), which is applied in the presence of sodium metaborate. Characterization of the synthesized SDS-capped Ag NPs by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX) showed that the nanoparticles were well synthesized with nearly uniform size and an average diameter of < 30 nm. Interaction of sodium metaborate with the SDS-capped Ag NPs and tobramycin results in aggregation of the nanoparticles and consequently decreases the absorbance intensity, leading to the production of a new absorbance peak and a color change from yellow to purple. The absorbance intensity was recorded at λmax = 400 nm and 522 nm and λ522/λ400 was used as the analytical signal. The experimental parameters were investigated and optimized using a multivariate optimization method (central composite design). The current nanoprobe gives a linear response for tobramycin from 1.0 to 50.0 ng mL-1 with a detection limit of 0.5 ng mL-1. The intra- and inter-day relative standard deviations for five replicated analyses of 10.0 ng mL-1 tobramycin are 2.8% and 4.2%, respectively. Graphical abstractSchematic representation of SDS-capped silver nanoparticles's response to tobramycin in the presence of sodium metaborate.

A single-shot diagnostic platform based on copper nanoclusters coated with cetyl trimethylammonium bromide for determination of carbamazepine in exhaled breath condensate.

A fluorescent nanoprobe is designed for the determination of carbamazepine (CBZ) in exhaled breath condensate (EBC) of patients receiving CBZ. The probe consists of copper nanoclusters (Cu NCs) coated with cetyl trimethylammonium bromide. The interaction of probe with CBZ results in blocking non-radiative e-/h+ recombination defect sites on the surface of Cu NCs and consequently enhancing the blue-green fluorescence of Cu NCs (excitation/emission wavelengths: 290/480 nm). The experimental conditions were optimized using a response surface methodology (central composite design). Under the optimized conditions, the calibration plot is linear in the 0.2 to 20 µg mL-1 CBZ concentration range and the detection limit is as low as 0.08 µg mL-1. The intra-day and inter-day relative standard deviations for six replicated measurements of 10 µg mL-1 CBZ are 3.9% and 4.8%, respectively. The method was applied for the determination of CBZ level in EBC of patients receiving CBZ. The accuracy of the method was confirmed by HPLC-UV analysis as a reference method. Graphical abstract Graphical abstract contains poor quality and small text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf. "Figures 1 contains poor quality of text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.A new PDF format of Graphical Abstract was provided in attachment section. Schematic presentation of cetyl trimethylammonium bromide coated copper nanocluster's response to carbamazepine.

Smart systems for determination of drug's solubility.

The solubility of drugs is a crucial physicochemical property in the drug discovery or development process and for improving the bioavailability of drugs. There are various methods for evaluating the solubility of drugs including manual measurement methods, mathematical methods, and smart methods. Manual measurement and mathematical methods have some defects which make the smart systems more reliable and important in this field. In this review, various instruments used for the solubility determination, along with the smart systems, have been discussed. Mechanism and applications of each method have been elaborated in detail. Moreover, unique characteristics as well as some limitations of discussed methods are also described.

Electrochemical monitoring of malondialdehyde biomarker in biological samples via electropolymerized amino acid/chitosan nanocomposite.

This study reports on the electropolymerization of a low toxic and biocompatible nanopolymer with entitle poly arginine-graphene quantum dots-chitosan (PARG-GQDs-CS) as a novel strategy for surface modification of glassy carbon surface and preparation of a new interface for measurement of malondialdehyde (MDA) in exhaled breath condensate. Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of GQDs-CS nanostructures on a PARG prepolymerized on the surface of glassy carbon electrode using cyclic voltammetry techniques in the regime of -1.5 to 2 V. The modified electrode appeared as an effective electroactivity for detection of MDA by using cyclic voltammetry, linear sweep voltammetry, and differential pulse voltammetry. The prepared modified electrode demonstrated a noticeably good activity for electrooxidation of MDA than PARG. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between the excellent properties of PARG and semiconducting polymer, GQDs as high density of edge plane sites and subtle electronic characteristics and unique properties of CS such as excellent film-forming ability, high permeability, good adhesion, nontoxicity, cheapness, and a susceptibility to chemical modification. The prepared sensor showed 1 oxidation processes for MDA at potentials about 1 V with a low limit of quantification 5.94 nM. Finally, application of new sensor for determination of MDA in exhaled breath condensate was suited. In general, the simultaneous attachment of GQDs and CS to structure of poly amino acids provides new opportunities within the personal healthcare.

Non-volatile compounds in exhaled breath condensate: review of methodological aspects.

In contrast to bronchial and nasal lavages, the analysis of exhaled breath condensate (EBC) is a promising, simple, non-invasive, repeatable, and diagnostic method for studying the composition of airway lining fluid with the potential to assess lung inflammation, exacerbations, and disease severity, and to monitor the effectiveness of treatment regimens. Recent investigations have revealed the potential applications of EBC analysis in systemic diseases. In this review, we highlight the analytical studies conducted on non-volatile compounds/biomarkers in EBC. In contrast to other related articles, this review is classified on the basis of analytical techniques and includes almost all the applied methods and their methodological limitations for quantification of non-volatile compounds in EBC samples, providing a guideline for further researches. The studies were identified by searching the SCOPUS database with the keywords "biomarkers," "non-volatile compounds," "determination method," and "EBC."

Extraction and Analysis of Methadone in Exhaled Breath Condensate Using a Validated LC-UV Method.

PURPOSE: A combined microextraction and separation method is presented for the determination of methadone in exhaled breath condensate (EBC) which is a promising non-invasive biological component for monitoring drug concentrations. METHODS: In this work, dispersive liquid-liquid microextraction (DLLME) and ultrasonic liquid-liquid microextraction (ULLME) procedure coupled with a validated liquid chromatography method were used for analysis of methadone in EBC collected using an in-house cold trap setup. The method has been validated according to the FDA guidelines using EBC-spiked samples and tested on a number of EBC samples collected from patients. RESULTS: The best DLLME conditions involved the use of a disperser solvent of methanol (1 mL), extraction solvent of chloroform (200 mL), EBC sample pH of 10.0 and centrifugation at 6000 rpm for 5 minutes. The conditions for ULLME were 150 mL of chloroform and the samples were sonicated for 4 minutes. The method was validated over the concentration range of 0.5-10 mg/L-1 in EBC. Inter- and intra-day precision and accuracy were less than 5 % where the acceptable levels are less than 20%. Furthermore, the validated method was successfully applied for the determination of methadone in patients' EBC samples. CONCLUSIONS: The outcomes indicate that the developed LC-UV combined with DLLME and/or ULLME extraction methods can be employed for the extraction and separation of methadone in EBC samples.

Digital image colorimetry for determination of ethanol in exhaled breath condensate.

Aim: This study aimed to develop a colorimetric approach for quantifying ethanol using smartphone image analysis. Method: This research presents a straightforward smartphone-based colorimetric sensor that efficiently measures ethanol levels in exhaled breath condensate (EBC) samples. The process involved changing the acidic dichromate color in an ethanolic solution, followed by image analysis. Results: The results showed that this method was able to estimate ethanol concentrations in the range of 300-1500 and 1600-8000 µg ml-1 in EBC. Conclusion: This study was a follow-up study on the previous work published for the determination of ethanol in EBC samples and highlights the potential benefits of using digital images and smartphone applications for ethanol determination in biological samples.

Propofol-induced in-situ formation of silver nanoparticles: A sensing colorimetric method.

A simple and eco-friendly colorimetric sensing method has been developed for the extremely effective detection of propofol in exhaled breath condensate (EBC). In this study, we put forward a Tollens' procedure, in which silver nanoparticles (AgNPs) were produced using propofol as a reducing agent. To verify the in-situ synthesis of AgNPs, the TEM images, and UV-Vis absorbance were recorded in the absence and presence of propofol. The solution turned from a colorless to yellow and deep yellow color due to the surface plasmon resonance absorption band of formed AgNPs. The intensity of nanoparticle absorbance was quantitatively correlated with the propofol concentration. The proposed sensor revealed good linearity over the range of 0.01-0.8 µg mL-1 at 422 nm with the detection limit of 8.8 ng mL-1 under optimum conditions. Finally, the proposed colorimetric sensor was successfully used for the determination of propofol in the EBC sample of patients receiving propofol.

A smartphone digital image colorimetric method based on nanoparticles for determination of lamotrigine.

Aim: A colorimetric approach for quantification of lamotrigine using spectrophotometric and smartphone image analysis is described in this study. Methods: For full optimization and validation procedures, UV-visible spectroscopy was used, and image analysis was carried out with the help of an app (PhotoMetrix PRO®). Then, as a multivariate calibration method, parallel factor analysis was used for data analysis. Results: The results demonstrated the capacity of these methods to estimate lamotrigine concentrations in the range of 0.1-7.0 µg.ml-1 in exhaled breath condensate, indicating the value of using digital images and smartphone applications in combination with chemometric tools. Conclusion: The image analysis can be superior for its fast and reliable lamotrigine analysis in biological samples.

A Rayleigh light scattering technique based on ß- cyclodextrin modified gold nanoparticles for phenytoin determination in exhaled breath condensate.

In the current work, a RLS technique based on ß-cyclodextrin modified gold nanoparticles was validated for phenytoin determination in the exhaled breath condensate. It relies on the complexation of ß-cyclodextrins using -OH groups with amine groups of phenytoin which results in an aggregation-induced Rayleigh light scattering intensity enhancement proportional to phenytoin addition. The method shows a linear relationship with phenytoin concentration in the range of 0.005-0.6 µg.mL-1 with a limit of detection of 0.003 µg.mL-1. The validated Rayleigh light scattering system is successfully used for phenytoin determination in the EBC of patients receiving phenytoin.

Utilizing a nanocomposite aerogel grafted with Fe3O4@GO for the extraction and determination of metoprolol in exhaled breath condensate.

This article presents a solid-phase extraction method combined with a spectrofluorometric method for the extraction/pre-concentration and determination of metoprolol (MET) in exhaled breath condensate. The extraction sorbent is an agarose aerogel nanocomposite grafted with graphene oxide (GO) Fe3O4. The size and morphology of the nanosorbent were characterized via X-ray crystallography, scanning electron microscopy, Fourier-transform infrared spectrometry, and Brunauer-Emmett-Teller analysis. Factors affecting the extraction/determination of MET were optimized using the one-at-a-time method. Under optimized experimental conditions, the calibration graph was linear in the range of 0.005 to 2.0 µg mL-1 with a detection limit of 0.001 µg mL-1. The method was successfully applied for the determination of MET in biological samples taken from patients receiving MET.

Online preconcentration and chiral separation of ofloxacin in exhaled breath condensate by capillary electrophoresis.

Breath analysis is an effective method of monitoring systemic or respiratory ailments. A simple chiral capillary electrophoresis method coupled with an online field-amplified sample injection stacking method is presented for ultratrace quantification of the enantiomers of ofloxacin in exhaled breath condensate (EBC). The study is focused on the use of EBC as an easily available biological sample to monitor ofloxacin's enantiomers levels with good patient compliance. The proposed method was validated in accordance with FDA guidelines over the concentration range of 0.004-1.0 µg mL-1 of racemic ofloxacin. Inter- and intra-day precision and accuracy were within the acceptable limit (below 8.50 %). The method was specific for routine analysis of ofloxacin's enantiomers. A small volume of EBC samples from seven patients under ofloxacin therapy was analyzed using the proposed method in which the concentrations of "R" and "S" enantiomers were between 0.0026 and 0.056 µg mL-1.

Efficient dispersive solid-phase extraction of methylprednisolone from exhaled breath of COVID-19 patients.

In the current study, bismuth ferrite nano-sorbent was synthesized and utilized as a sorbent for the dispersive solid-phase extraction of methylprednisolone from exhaled breath samples. The size and morphology of the nano-sorbent were characterized by X-ray diffraction analysis and scanning electron microscopy. Following its desorption with acetonitrile, methylprednisolone was quantified by a high-performance liquid chromatography-ultraviolet detector. Factors affecting the extraction of methylprednisolone were optimized. Under optimized experimental conditions, a linear relationship between the analytical signals and methylprednisolone concentration was obtained in the range of 0.001-0.2 µg mL-1 for exhaled breath condensate samples and 0.002-0.4 µg per filter for filter samples. A pre-concentration factor of 6.4-fold, corresponding to an extraction recovery of 96.0%, was achieved. The validated method was applied for the determination of methylprednisolone in real samples taken from the exhaled breath of COVID-19 patients under mechanical ventilation.

Exhaled breath condensate efficacy to identify mutations in patients with lung cancer: A pilot study.

Exhaled breath condensate (EBC) is used to investigate the efficacy of EBC to detect the genetic mutations in patients with lung cancer. Samples of 5 patients and 5 healthy volunteers were collected. DNA was extracted and used for amplification of hotspot regions of TP53 and KRAS genes by using PCR. We performed the mutation analysis by direct sequencing in all subjects. Detected mutations in EBC samples were compared with those of corresponding tumor tissues and there was complete agreement within the detected mutations in EBC and tumorous tissue. EBC can be used as an efficient and noninvasive source for the assessment of gene mutations in patients with lung cancer.

Development a coordination polymer based nanosensor for phenobarbital determination in exhaled breath condensate.

In this study, a fluorometric probe based on luminol-terbium coordination polymer nanoparticles (luminol-Tb CP NPs) is validated for the quantification of phenobarbital in the exhaled breath condensate collected from expiratory circuit of the mechanical ventilator (MVEBC). It relies on the coordination of phenobarbital to luminol-Tb CP NPs which casing an aggregation-induced fluorescence enhancement of probe owing to the increasing the system rigidity and the decreasing the nonradiative decay rate. As the increase in response intensity is proportional to phenobarbital amount, a method is offered for its determination in MVEBC. This method presents a linear relationship with phenobarbital concentration in the range of 0.1-10.0 mg.L-1 with a limit of detection of 0.024 mg.L-1 and the relative standard deviation of 3.6%. The proposed method is used in MVEBC of the pre-term newborn babies receiving phenobarbital under mechanical ventilator.

Electromembrane extraction of tramadol from exhaled breath condensate and its liquid chromatographic analysis.

Tramadol has extracted from the exhaled breath condensate (EBC) samples through the supported liquid membrane consisting of 2-nitrophenyl octyl ether impregnated in the hollow fiber wall, and the lumen of the hollow fiber was filled with 20 µL of an acceptor phase. Under the optimum conditions of the electromembrane extraction, i.e. the stirring speed of 750 rpm, extraction time of 20 min, acceptor pH at 1.0, donor phase pH at 6.0, and an applied voltage of 170 V across the supported liquid membrane, a preconcentration factor of 128-fold with a extraction recovery of 64% was achieved. Acceptable linearity was obtained in the tramadol concentration range of 5-1000 ng mL-1 (R2 = 0.9999) with a limit of detection of 1.5 ng mL-1 and a limit of quantitation of 5 ng mL-1. The relative standard deviations for the intra-day and inter-day replications were obtained between 0.4% and 2.5%. The validated technique was successfully used to determine tramadol in real EBC samples.

Selection of Specific Aptamer against Rivaroxaban and Utilization for Label-Free Electrochemical Aptasensing Using Gold Nanoparticles: First Announcement and Application for Clinical Sample Analysis.

For the first time, a novel aptamer was designed and utilized for the selective detection of rivaroxaban (RIV) using the integration of bioinformatics with biosensing technology. The selected aptamer with the sequence 5'-TAG GGA AGA GAA GGA CAT ATG ATG ACT CAC AAC TGG ACG AAC GTA CTT ATC CCC CCC AAT CAC TAG TGA ATT-3' displayed a high binding affinity to RIV and had an efficient ability to discriminate RIV from similar molecular structures. A novel label-free electrochemical aptasensor was designed and fabricated through the conjugation of a thiolated aptamer with Au nanoparticles (Au-NPs). Then, the aptasensor was successfully applied for the quantitative determination of RIV in human plasma and exhaled breath condensate (EBC) samples with limits of detection (LODs) of 14.08 and 6.03 nM, respectively. These valuable results provide ample evidence of the green electrogeneration of AuNPs on the surface of electrodes and their interaction with loaded aptamers (based on Au-S binding) towards the sensitive and selective monitoring of RIV in human plasma and EBC samples. This bio-assay is an alternative approach for the clinical analysis of RIV and has improved specificity and affinity. As far as we know, this is the first time that an electrochemical aptasensor has been verified for the recognition of RIV and that allows for the easy, fast, and precise screening of RIV in biological samples.