Fabrication of an (α-Mn2O3:Co)-decorated CNT highly sensitive screen printed electrode for the optimization and electrochemical determination of cyclobenzaprine hydrochloride using response surface methodology

A new chemically optimized screen-printed electrode modified with a cobalt-doped α-Mn₂O₃ nanostructure on carbon nanotube paste (α-Mn₂O₃:Co@CNTs) has been constructed for the recognition of cyclobenzaprine hydrochloride. The prepared paste is based on the incorporation of oxide ion conductors, such as the α-Mn₂O₃ nanostructure with cobalt and ion pairs (tetraphenyl borate coupled with the drug), as electroactive species in the screen-printed electrode to increase the sensor surface area and decrease electrical resistance. The central composite design is a useful methodology for the estimation and modeling of the exact optimum parameters specifically designed for this process. This is a good way to graphically clarify the relationship between various experimental variables and the slope response. The proposed sensor, α-Mn₂O₃:Co@CNTs, possesses very good sensitivity and the ability to recognize the drug over the concentration range of 1 × 10⁻⁶ to 1 × 10⁻² mol L⁻¹ at 25 ± °C with a detection limit of 2.84 × 10⁻⁷ mol L⁻¹. It exhibits a reproducible potential and stable linear response for six months at a Nernstian slope of 58.96 ± 0.76 mV per decade. The proposed electrode approach has been successfully applied in the direct determination of the drug in its pure and dosage forms.

A new chemically optimized screen-printed electrode modified with a cobalt-doped α-Mn₂O₃ nanostructure on carbon nanotube paste (α-Mn₂O₃:Co@CNTs) has been constructed for the recognition of cyclobenzaprine hydrochloride.     

Disposable gold nanoparticle functionalized and bare screen-printed electrodes for potentiometric determination of trazodone hydrochloride in pure form and pharmaceutical preparations

In the present study, screen-printed electrodes unmodified and chemically modified with gold nanoparticles were used as sensitive electrochemical sensors for the determination of trazodone hydrochloride. The sensors were based on the use of a tetraphenylborate ion association complex as an electroactive material in screen-printed electrodes with dioctyl phthalate (DOP) as a solvent mediator modified with gold nanoparticles which improve the electrode conductivity and enhance the surface area. The sensors displayed a stable response for 5, 6 and 7 months with a reproducible potential and linear response over the concentration range 1 × 10⁻⁵–1 × 10⁻² mol L⁻¹ at 25 ± 1 °C with Nernstian slopes of 57.50 ± 0.66, 58.30 ± 0.45 and 59.05 ± 0.58 mV per decade and detection limits of 7.9 × 10⁻⁶, 7.6 × 10⁻⁶ and 6.8 × 10⁻⁶ mol L⁻¹ for sensor 1, 2 and 3 respectively. The analytical performance of the screen printed electrodes in terms of selectivity coefficients for trazodone hydrochloride relative to the number of potentially interfering substances was investigated. The proposed method has been applied successfully for the analysis of the drug in its pure and dosage forms and there is no interference from any common pharmaceutical additives.

In the present study, screen-printed electrodes unmodified and chemically modified with gold nanoparticles were used as sensitive electrochemical sensors for the determination of trazodone hydrochloride.     

Simple,fast and environmentally friendly method to determine ciprofloxacin in wastewater samples based on an impedimetric immunosensor

In this study an impedimetric immunosensor was developed in order to determine ciprofloxacin (CIP) in wastewater samples, an emergent contaminant widely found in wastewater. To achieve this, an anti-ciprofloxacin antibody was immobilized on the surface of a printed carbon electrode. Then, the developed immunosensor was applied in wastewater samples from Université Laval residences (Québec, Canada) through the load transfer resistance (R_ct) using [Fe(CN)₆]^3−/4− as a redox probe, and the average CIP concentration was found to be 2.90 × 10⁻⁴ μg mL⁻¹. The observed R_ct changes presented a linear relationship from CIP concentrations of 10⁻⁵ to 1.0 μg mL⁻¹, with detection and quantification limits of 2.50 × 10⁻⁶ and 7.90 × 10⁻⁶ μg mL⁻¹, respectively. The immunosensor presented high selectivity and repeatability, as well as a good recovery rate in wastewater samples (97%). Significant interference with other compounds was not observed. The proposed method requires only 30 μL of sample without the use of organic solvents or preceding sample preparation and/or extraction techniques. Moreover, the method is fast: only 20 min of incubation followed by 2 min of analysis time was sufficient to obtain the CIP concentration. The method''s estimated cost is U$ 2.00 per sample.

In this study an impedimetric immunosensor was developed in order to determine ciprofloxacin (CIP) in wastewater samples, an emergent contaminant widely found in wastewater samples.     

Sensitive impedimetric detection of troponin I with metal–organic framework composite electrode

Metal–organic frameworks (MOFs) are promising materials for biosensing applications due to their large surface to volume ratio, easy assembly as thin films, and better biocompatibility than other nanomaterials. Their application in electrochemical biosensing devices can be realized by integrating them with other conducting materials, like polyaniline (PANI). In the present research, a composite of a copper-MOF (i.e., Cu₃(BTC)₂) with PANI has been explored to develop an impedimetric sensor for cardiac marker troponin I (cTnI). The solvothermally synthesized Cu₃(BTC)₂/PANI composite has been coated as a thin layer on the screen-printed carbon electrodes (SPE). This electroconductive thin film was conjugated with anti-cTnI antibodies. The above formed immunosensor has allowed the impedimetric detection of cTnI antigen over a clinically important concentration range of 1–400 ng mL⁻¹. The whole process of antigen analysis could be completed within 5 min. The detection method was specific to cTnI even in the co-presence of other possibly interfering proteins.

A Cu-MOF/PANI modified screen-printed electrode based immunosensing technique is described for the sensitive detection of cardiac troponin I. The sensor provides detection over a wide concentration range with a limit of detection of 0.8 ng mL⁻¹.     

Development and validation of a sensitive LC-MS/MS method for pioglitazone: application towards pharmacokinetic and tissue distribution study in rats

In the present study, a sensitive LC-MS/MS method was developed and validated to measure pioglitazone (PGZ) concentrations in rat plasma and tissues. The chromatographic separation was achieved by using a YMC Pro C₁₈ column (100 mm × 4.6 mm, 3μ) with a mobile phase consisting of formic acid (0.1% v/v) and acetonitrile (5 : 95) at a flow rate of 0.7 mL min⁻¹ and injection volume of 10 μL (IS: rosiglitazone). Mass spectrometric detection was done using triple quadrupole mass spectrometry using the ESI interface operating in a positive ionization mode. The developed method was validated over a linearity range of 1–500 ng mL⁻¹ with detection and a lower quantification limit of 0.5 ng mL⁻¹ and 1 ng mL⁻¹. The method accuracy ranged from 95.89–98.78% (inter-day) & 93.39–97.68% (intra-day) with a precision range of 6.09–8.12% for inter-day & 7.55–9.87% for intra-day, respectively. The PGZ shows the highest C_max of 495.03 ng mL⁻¹ in plasma and the lowest C_max, 24.50 ± 2.71 ng mL⁻¹ in bone. The maximum T_max of 5.00 ± 0.49 h was observed in bone and a minimum of 1.01 ± 0.05 h in plasma. The AUC_{(0–24 h and 0–∞)} values are highest in plasma (1056.58 ± 65.78 & 1069.38 ± 77.50 ng h⁻¹ mL⁻¹) and lowest in brain (166.93 ± 15.70 &167.12 ± 16.77 ng h⁻¹ mL⁻¹), and the T_1/2 was highest in plasma (5.62 ± 0.74 h) and lowest in kidney (2.78 ± 0.19). The developed method was successfully used to measure the PGZ pharmacokinetic and tissue distribution. Further, the developed method could be utilized for validating target organ (adipose tissue) specific delivery of PGZ (nano-formulations) in addition to conventional dosage forms.

The developed method was investigated for target and off-target distribution of pioglitazone and could be applied to validate the site-specific delivery systems.     

Integrated all-solid-state sulfite sensors modified with two different ion-to-electron transducers: rapid assessment of sulfite in beverages

An integrated all-solid-state screen-printed ion-selective potentiometric sensor for rapid assessment of sulfite ion in beverages, based on analytical transduction, is described. The constructed potentiometric cell incorporates a polymeric membrane sulfite ion-selective electrode based on cobalt(ii) phthalocyanine (CoPC) as a recognition material and an Ag/AgCl reference electrode with a polyvinyl butyral reference membrane. Two different solid-contact transducers, namely multi-walled carbon nanotubes (MWCNTs) and polyaniline (PANI) were used for a comparative study. The presented sensors exhibited a rapid Nernst response across the concentration ranges from 2.0 × 10⁻⁶ to 2.3 × 10⁻³ M and from 5.0 × 10⁻⁶ to 2.3 × 10⁻³ M with detection limits equal to 1.1 × 10⁻⁶ M and 1.5 × 10⁻⁶ M for sensors based on MWCNTs and PANI, respectively. The proposed sensors manifested high selectivity and sensitivity, enhanced stability and low cost that provides a wide number of potential applications for food analysis. Good performance characteristics were obtained for the proposed method after applying the validation requirements. Method precision, accuracy, bias, trueness, repeatability, reproducibility, and uncertainty are examined. These analytical capabilities support the rapid and direct determination of sulfite in different beverage samples. The analytical results were verified and compared with the standard iodometric method.

An integrated all-solid-state screen-printed ion-selective potentiometric sensor for rapid assessment of sulfite ion in beverages, based on analytical transduction, is described.     

Application of pyrite and chalcopyrite as sensor electrode for amperometric detection and measurement of hydrogen peroxide

The sensing performance of solid-state amperometric sensors based on natural sulfide minerals, i.e., pyrite and chalcopyrite, has been characterized for the detection and measurement of hydrogen peroxide (H₂O₂) in aqueous medium. The sensors showed a wide linear relationship range between response current and the concentration of H₂O₂ from 1.0 × 10⁻⁵ mol L⁻¹ to 1.0 × 10⁻² mol L⁻¹ and 1.0 × 10⁻⁴ mol L⁻¹ to 3.0 × 10⁻² mol L⁻¹ for pyrite and chalcopyrite, respectively. The limit of detection (LOD) was as low as 8.6 × 10⁻⁶ mol L⁻¹ and 5.2 × 10⁻⁵ mol L⁻¹ (S/N = 3), respectively. The electrodes exhibited great sensitivity, repeatability and short response time (less than 5 s). The results show that pyrite and chalcopyrite can be used as a natural, low cost, reliable and sensitive sensor for hydrogen peroxide detection, creating a new and high value application for the sulfide minerals.

The sensing performance of solid-state amperometric sensors based on natural sulfide minerals, i.e., pyrite and chalcopyrite, has been characterized for the detection and measurement of hydrogen peroxide (H₂O₂) in aqueous medium.     

A new strategy for synthesizing silver doped mesoporous bioactive glass fibers and their bioactivity,antibacterial activity and drug loading performance

A new strategy for preparing mesoporous metal-doped bioactive glass fibers (MBGFs) was designed, which included electrospinning and sulfonating mesoporous PS fibers, precipitating metal ions and bioactive glass sol–gel precursor into the mesoporous polystyrene (PS) fibers and calcinations. Silver-doped mesoporous BGFs (Ag-MBGFs) with a uniform diameter of 1–2 μm and a specific surface area of 40.22 m² g⁻¹ were prepared as an example and characterized by SEM, XRD, TG, ICP and FTIR. These Ag-MBGFs showed excellent bioactivity, antibacterial properties and drug loading and release performance due to their special mesoporous and fibrous structure. The concentration of Staphylococcus aureus decreased from 1 × 10⁸ colony-forming units per mL (CFU mL⁻¹) to 2.5 × 10⁶ CFU mL⁻¹ in 2 h and then to 2 × 10² CFU mL⁻¹ in 12 h when the concentration of the Ag-MBGFs reached 16 mg mL⁻¹. BGFs of different compositions and functions could be prepared by the same strategy in a mesoporous PS fiber template, which could enrich materials for constructing orthopedic implants.

A new strategy for preparing mesoporous metal-doped bioactive glass fibers.     

NaBiF4 upconversion nanoparticle-based electrochemiluminescent biosensor for E. coli O157 : H7 detection

Foodborne or water-borne pathogens pose great threats to human beings and animals. There is an urgent need to detect pathogens with cheap, rapid and sensitive point-of-care diagnostic assays. Herein, we report the electrochemiluminescent (ECL) behaviors of NaBiF₄ : Yb³⁺/Er³⁺ upconversion nanoparticles (UCNPs) which were synthesized via a fast and environment-friendly method at room temperature for the first time. The UCNPs together with K₂S₂O₈ exhibit high ECL intensity and stable cathodic signals. Further, the Au nanoparticles (Au NPs) and Anti-E. coli O157 : H7 antibody were assembled on the surface of UCNPs successively to construct a novel ECL immunosensor for the detection of deadly E. coli O157 : H7. The as-prepared ECL immunosensor reveals high sensitivity to E. coli O157 : H7 in a linear range of 200–100 000 CFU mL⁻¹, and the minimum detection limit could reach up to 138 CFU mL⁻¹. The designed UCNP-based biosensor demonstrates high specificity, good stability and remarkable repeatability, and the strategy will provide a sensitive and selective method for rapid detection of E. coli O157 : H7 in food safety and preclinical diagnosis.

The ECL behaviors of NaBiF₄ : Yb³⁺/Er³⁺ UCNPs synthesized via a fast and environment-friendly method are reported for the first time. UCNPs-based ECL biosensor shows a wide detection range with low detection limit of 138 CFU mL⁻¹ for E. coli O157 : H7.     

Electrochemical sensory detection of Sus scrofa mtDNA for food adulteration using hybrid ferrocenylnaphthalene diimide intercalator as a hybridization indicator

In this study, an electrochemical DNA biosensor was developed based on the fabrication of silicon nanowires/platinum nanoparticles (SiNWs/PtNPs) on a screen-printed carbon electrode (SPCE) for the detection of Sus scrofa mitochondrial DNA (mtDNA) in food utilizing a new hybrid indicator, ferrocenylnaphthalene diimide (FND). The morphology and elemental composition of the SiNWs/PtNPs-modified SPCE was analyzed by field emission scanning electron microscopy (FESEM) combined with energy dispersive X-ray spectroscopy (EDX). Cyclic voltammetry (CV) was used to study the electrical contact between the PtNPs and the screen-printed working electrode through SiNWs, while electrochemical impedance spectroscopy (EIS) was used to measure the charge transfer resistance of the modified electrode. The results clearly showed that the SiNWs/PtNPs were successfully coated onto the electrode and the effective surface area for the SiNWs/PtNPs-modified SPCE was increased 16.8 times as compared with that of the bare SPCE. Differential pulse voltammetry used for the detection of porcine DNA with FND as an intercalator confirmed its specific binding to the double-stranded DNA (dsDNA) sequences. The developed biosensor showed a selective response towards complementary target DNA and was able to distinguish non-complementary and mismatched DNA oligonucleotides. The SiNWs/PtNPs-modified SPCE that was fortified with DNA hybridization demonstrated good linearity in the range of 3 × 10⁻⁹ M to 3 × 10⁻⁵ M (R² = 0.96) with a detection limit of 2.4 × 10⁻⁹ M. A cross-reactivity study against various types of meat and processed food showed good reliability for porcine samples.

An electrochemical DNA biosensor was developed based on the fabrication of silicon nanowires/platinum nanoparticles on a screen-printed carbon electrode for the detection of Sus scrofa mitochondrial DNA in food.     

An azo-coupling reaction-based surface enhanced resonance Raman scattering approach for ultrasensitive detection of salbutamol

To date, great achievements with GC-MS, HPLC-MS, and fluorescence biosensing techniques have been made to detect illegal additives of salbutamol (SAL) in swine meat. However, these methods are not suitable for rapid on-site screening due to either costly instruments or rather complicated and/or time consuming sample pretreatments. Herein, a simple, rapid and ultrasensitive approach based on an azo-coupling reaction and surface-enhanced resonance Raman scattering (SERRS) is presented. By combining with a magnetic SERS substrate, an indirect detection for SAL, with a LOD of 1.0 × 10⁻¹¹ M (2.39 pg mL⁻¹), was realized. Moreover, a colorimetric method for naked eye detection was successfully carried out for rapid screening of SAL in concentrations higher than 2.09 × 10⁻⁵ M (5 μg mL⁻¹). In addition, the proposed method was successfully applied for the rapid determination of SAL in real swine meat. The entire process, including pretreatment, coupling reaction and SERRS detection, was performed within 7 min. Moreover, the SERRS fingerprint band being specific to corresponding functional group guarantees the selectivity for the target molecule. Therefore, the proposed strategy in the present study offers a new way to identify trace amounts of analytes, such as SAL as well as other illegal additives in health-related products and food.

Azo-coupling reaction-based SERRS indirect approach for SAL detection, with a LOD of 1.0 × 10⁻¹¹ M within 7 min for real samples.     

Knecorticosanones C–H from the fruits of Knema globularia (Lam.) warb

Six undescribed polyketides, 1–6, were discovered from the fruits of Knema globularia (Lam.) warb. Two known polyketides and three known lignans were also isolated. Cytotoxicities against HepG2 and KKU-M156 cells of all polyketides were evaluated. Compound 1 displayed the most cytotoxic activity against HepG2 and KKU-M156 cell lines with IC₅₀ values of 1.57 ± 0.37 and 1.78 ± 0.14 μg mL⁻¹, respectively. The structure of all isolates was identified using spectroscopic methods including NMR, IR, MS and ECD.

Compound 1 displayed the most cytotoxic activity against HepG2 and KKU-M156 cell lines with IC₅₀ values of 1.57 ± 0.37 and 1.78 ± 0.14 μg mL⁻¹, respectively.     

Developing a screen-printed graphite–polyurethane composite electrode modified with gold nanoparticles for the voltammetric determination of dopamine

A screen-printed electrode (SPGPUE) was prepared with graphite–polyurethane composite ink containing gold nanoparticles (AuNPs), resulting in a screen-printed graphite–polyurethane composite electrode modified with gold nanoparticles (SPGPUE–AuNPs). Gold nanoparticles were prepared by the citrate method and extracted from the water medium since polyurethane is not compatible with humidity. After extraction to chloroform, they were characterized via transmission electron microscopy (TEM). The presence of gold on the SPGPUE–AuNP surface was confirmed via SEM and EDX analyses, while thermogravimetry revealed the presence of approximately 3.0% (m/m) gold in the composite. An electrochemical pretreatment in 0.10 mol L⁻¹ phosphate buffer (pH 7.0) with successive cycling between −1.0 V and 1.0 V (vs. pseudo-Ag/AgCl) under a scan rate of 200 mV s⁻¹ and 150 cycles was required in order to provide a suitable electrochemical response for the voltammetric determination of dopamine. After the optimization of the parameters of differential pulse voltammetry (DPV), an analytical curve was obtained within a linear dynamic range of 0.40–60.0 μmol L⁻¹ and detection limit (LOD) of 1.55 ×10⁻⁸ mol L⁻¹ for dopamine at the SPGPUE–AuNP. A non-modified SPGPUE was used for comparison and a linear range was obtained between 2.0 and 10 μmol L⁻¹ with an LOD of 2.94 × 10⁻⁷ mol L⁻¹. During the dopamine determination in cerebrospinal synthetic fluid (CSF), recoveries between 89.3 and 103% were achieved. There were no significant interferences from ascorbic acid and uric acid, but some from epinephrine due to the structural similarity.

A screen-printed modified composite electrode (SPGPUE) was prepared with graphite–polyurethane ink containing gold nanoparticles (AuNPs), resulting in a sensor with improved sensitivity regarding the unmodified device in dopamine determination.     

Exploring the nature of the clopidogrel–bromocresol green interaction via spectrophotometric measurements and quantum chemical calculations

Clopidogrel is an oral, thienopyridine class antiplatelet agent used to inhibit blood clots in coronary arteries, peripheral vascular and cerebrovascular diseases. A spectrophotometric method was developed for clopidogrel bisulfate (CLOP·H₂SO₄) determination using bromocresol green (BCG) as an ion-pairing agent. To explore the binding nature of CLOP·H₂SO₄ with BCG at a molecular level, quantum chemical calculations have been performed. DFT based full geometry optimization has been carried out for BCG and clopidogrel in basic (CLOP) and protonated (CLOP⁺) forms as well as for BCG ion-pairs with CLOP and CLOP·H₂SO₄. The DFT calculations referred to the stability of the BCG–CLOP⁺ ion-pair and its spontaneous formation reaction from BCG and CLOP·H₂SO₄ compared to the BCG–CLOP-ion-pair. Furthermore, the UV-visible spectra and their corresponding excited states and electronic transitions for BCG, BCG–CLOP⁺ ion-pair, and BCG–CLOP ion-pair have been investigated. These spectra provided a molecular level understanding of the nature of the different intra-molecular and intermolecular electronic transitions in the BCG ion-pairs with CLOP⁺. Moreover, the quantitative analysis based on extracting a yellow-formed ion-pair into chloroform from aqueous medium was carried out. The ion-pair exhibits an absorption maximum at 413 nm. The optimum conditions of the reactions were studied experimentally and optimized. The calibration graph shows that CLOP·H₂SO₄ can be determined up to 100.0 μg mL⁻¹ with detection limit (LOD) of 0.57 μg mL⁻¹ and quantification limit (LOQ) of 1.86 μg mL⁻¹. The low relative standard deviation values, 0.16–1.16, indicate good precision. The results were compared to other published data and were treated statistically using F and t-tests.

The nature of the different electronic transitions of clopidogrel bisulfate; antiplatelet agent, in BCG ion-pair and quantitative analysis based on extracting a yellow-formed ion-pair into chloroform from aqueous medium is obtained.     

Immunochromatographic assay for melamine based on luminescent quantum dot beads as signaling probes

To screen and detect the harmful substance melamine (MEL), a quantum-dot-bead-based immunochromatographic assay (QB-ICA) was formulated. After optimization, calibration was performed within the linear range from 0.06 to 0.28 ng mL⁻¹, with limit of detection (LOD) of 0.04 ng mL⁻¹. The LOD was 35 times lower than that of ICA that used colloidal gold nanoparticles (LOD = 1.4 ng mL⁻¹) and 40 times lower than that of the assay based on quantum dots (LOD = 1.6 ng mL⁻¹). In the detection of MEL in spiked pure milk using the proposed QB-ICA strategy, the LOD (LOD = 0.19 ng mL⁻¹) of the samples with the proposed pretreatment was 18.4 times lower than those of the samples without pretreatment (LOD = 3.5 ng mL⁻¹). The performance and practicability of the proposed QB-ICA system was validated; the obtained results reveal that QB-ICA is comparable with the conventional enzyme-linked immunosorbent assay (ELISA) method, but with enhanced applicability. Given its high sensitivity and practicability, the QB-ICA strategy could become a worthwhile alternative for the rapid, sensitive, and quantitative onsite detection of harmful substances, facilitating food safety monitoring.

An immunochromatographic assay using quantum dot beads as a label was established for melamine detection in milk with fast and effective pretreatment.     

Novel chalcone derivatives containing a 1,2,4-triazine moiety: design,synthesis, antibacterial and antiviral activities

A series of novel chalcone derivatives containing the 1,2,4-triazine moiety were synthesized and their structures were confirmed by ¹H NMR, ¹³C NMR and elemental analyses. Antiviral bioassays revealed that most of the compounds exhibited good antiviral activity against tobacco mosaic virus (TMV) at a concentration of 500 μg mL⁻¹. The designated compound 4l was 50% effective in terms of curative and protective activities against TMV with 50% effective concentrations (EC₅₀) of 10.9 and 79.4 μg mL⁻¹, which were better than those of ningnanmycin (81.4 and 82.2 μg mL⁻¹). Microscale thermophoresis (MST) also showed that the binding of compound 4l to coat protein (TMV-CP) yielded a K_d value of 0.275 ± 0.160 μmol L⁻¹, which was better than that of ningnanmycin (0.523 ± 0.250 μmol L⁻¹). At the same time, molecular docking studies for 4l with TMV-CP (PDB code:1EI7) showed that the compound was embedded well in the pocket between the two subunits of TMV-CP. Meanwhile, compound 4a demonstrated excellent antibacterial activities against Ralstonia solanacearum (R. solanacearum), with an EC₅₀ value of 0.1 μg mL⁻¹, which was better than that of thiodiazole-copper (36.1 μg mL⁻¹) and bismerthiazol (49.5 μg mL⁻¹). The compounds act by causing folding and deformation of the bacterial cell membrane as observed using scanning electron microscopy (SEM). The chalcone derivatives thus synthesized could become potential alternative templates for novel antiviral and antibacterial agents.

A series of novel chalcone derivatives containing the 1,2,4-triazine moiety were synthesized and their structures were confirmed by ¹H NMR, ¹³C NMR and elemental analyses.     

Graphitic carbon nitride and APTES modified advanced electrochemical biosensor for detection of 17β-estradiol in spiked food samples

This work demonstrates a simple and inexpensive electrochemical biosensing pathway for selective and sensitive recognition of 17β-estradiol (E2) in environmental and food samples. The biosensing system is based on graphitic carbon nitride (g-C₃N₄) and a conductive polymer 3-aminopropyltriethoxysilane (APTES). The proposed biosensor shows the ability to detect E2 in attomolar levels within a wide linear logarithm concentration range of 1 × 10⁻⁶ to 1 × 10⁻¹⁸ mol L⁻¹ with a limit of detection (LOD) of 9.9 × 10⁻¹⁹ mol L⁻¹. The selectivity of the developed biosensor was confirmed by conducting the DPV of similarly structured hormones and naturally occurring substances. The proposed biosensor is highly stable and applicable to detect E2 in the presence of spiked food and environmental samples with satisfactory recoveries ranging from 95.1 to 104.8%. So, the designed electrochemical biosensor might be an effective alternative tool for the detection of E2 and other endogenous substances to attain food safety.

This work demonstrates a simple and inexpensive electrochemical biosensing pathway for selective and sensitive recognition of 17β-estradiol (E2) in environmental and food samples.     

Unravelling the antifungal and antiprotozoal activities and LC-MS/MS quantification of steroidal saponins isolated from Panicum turgidum

Bioassay-guided investigation of Panicum turgidum extract resulted in the identification of seven steroidal saponins (Turgidosterones 1–7). They were evaluated for their in vitro antifungal, antileishmanial, and antitrypanosomal activities. Turgidosterone 6 was the most active antifungal against Candida albicans and Candida neoformans (IC₅₀ values of 2.84 and 1.08 μg mL⁻¹, respectively). Turgidosterones 4–7 displayed antileishmanial activity against Leishmania donovani promastigotes with IC₅₀ values ranging from 4.95 to 8.03 μg mL⁻¹ and against Leishmania donovani amastigote/THP with IC₅₀ values range of 4.50–9.29 μg mL⁻¹. Activity against Trypanosoma brucei was also observed for Turgidosterones 4–7 with an IC₅₀ values range of 1.26–3.77 μg mL⁻¹. Turgidosterones 1–3 did not display any activity against the tested pathogens. The study of structure–activity relationships of the isolated saponins indicated that the antifungal, antileishmanial, and antitrypanosomal activities are markedly affected by the presence of spirostane-type saponins and the elongation of the sugar residue at C-3. To quantitatively determine the most abundant active ingredient in Panicum turgidum extract, a single run, sensitive, and highly selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been applied under positive and negative modes. The obtained results showed that compound 5 was the most abundant (95.93 ± 1.10 mg per gram of dry Panicum turgidum extract), followed by 6 (52.51 ± 1.05 mg gm⁻¹), 4 (32.71 ± 0.48 mg gm⁻¹), and 7 (13.19 ± 0.50 mg gm⁻¹). Docking of these saponins against the Candida albicans oxidoreductases and Leishmania infantum trypanothione reductase active sites revealed their potential to effectively bind with a number of key residues in both receptor targets.

Bioassay-guided investigation of Panicum turgidum extract resulted in the identification of seven steroidal saponins (Turgidosterones 1–7).     

Fabrication of an immunosensor for quantitative detection of breast cancer biomarker UBE2C

This work reports the design of a new electrochemical impedimetric immunosensor for the direct determination of ubiquitin-conjugating enzymes 2C (UBE2C), a potential diagnostic biomarker for breast cancer. The immunosensor was fabricated by immobilizing the capture anti-UBE2C antibody onto a polyaniline (PANI) modified glassy carbon electrode (GCE) through glutaraldehyde crosslinking. The assembly process of the immunosensor was examined using scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The fabricated immunosensor enabled the detection of recombinant human UBE2C in the range of 500 pg mL⁻¹ to 5 μg mL⁻¹. The limit of detection and limit of quantification were found to be 7.907 pg mL⁻¹ and 26.356 pg mL⁻¹, respectively. The diagnostic application of the fabricated immunosensor was explored for the analysis of breast cancer cell line MCF-7 cell extract. The immunosensor demonstrated high selectivity for UBE2C. The fabricated immunosensor also exhibited good reproducibility and storage stability.

Antibodies crosslinking on PANI modified electrode to design a highly selective immunosensor to detect UBE2C.     

Development of a HPLC-FL method to determine benzaldehyde after derivatization with N-acetylhydrazine acridone and its application for determination of semicarbazide-sensitive amine oxidase activity in human serum

A novel fluorescence labeling reagent N-acetylhydrazine acridone (AHAD) was designed and synthesized. A highly sensitive high performance liquid chromatography (HPLC) method coupled with fluorescence detection to determine benzaldehyde after derivatization with AHAD was developed. Optimum derivatization was obtained at 40 °C for 30 min with trichloroacetic acid as catalyst. Benzaldehyde derivative was separated on a reversed-phase SB-C18 column in conjunction with a gradient elution and detected by fluorescence detection at excitation and emission wavelengths of 371 nm and 421 nm. The established method exhibited excellent linearity over the injected amount of benzaldehyde of 0.003 to 5 nmol mL⁻¹. The method was successfully applied to the determination of serum semicarbazide-sensitive amine oxidase (SSAO) activity in humans. SSAO is a significant biomarker because serum SSAO activity is elevated in patients with Alzheimer''s disease, vascular disorders, heart disease and diabetes mellitus. It was demonstrated that the SSAO activity of the hyperglycemic group (60 ± 4 nmol mL⁻¹ h⁻¹) was significantly higher than that of normal blood sugar group (44 ± 4 nmol mL⁻¹ h⁻¹) with P < 0.05.

A highly sensitive HPLC-FL method to determine semicarbazide-sensitive amine oxidase activity was developed utilizing AHAD as the novel fluorescence labeling reagent.