Polypyrrole/carbon dot nanocomposite as an electrochemical biosensor for liquid biopsy analysis of tryptophan in the human serum of normal and breast cancer women

Liquid biopsy analysis represents a suitable alternative analysis procedure in several cases where no tumor tissue is available or in poor patient conditions. Amino acids can play a crucial role in aiding cancer diagnosis. Monitoring of tryptophan (Trp) catabolism can aid in tracking cancer progression. Therefore, a novel nanocomposite was fabricated using overoxidized polypyrrole film doped with nano-carbon dots (nano-CDs) on the pencil graphite electrode (PGE) surface for sensitive evaluation of Trp in human serum. Using square wave voltammetry (SWV), the overoxidized polypyrrole/carbon dots/pencil graphite electrode (Ov-Ox PPy/CDs/PGE) achieved excellent electrochemical catalytic activity for evaluating Trp. The modified electrode, known as Ov-Ox PPy/CDs/PGE, demonstrated superior electrochemical catalytic activity compared to bare PGE, CDs/PGE, PPy/PGE, and PPy/CDs/PGE for evaluation of Trp. The method's excellent sensitivity was confirmed by the low limits of detection (LOD = 0.003 μmol L-1) and limit of quantitation (LOQ = 0.009 μmol L-1). The biosensor that was developed can measure tryptophan (Trp) levels in the serum of both healthy individuals and female breast cancer patients with high accuracy and sensitivity. The results indicate that there is a significant difference, as shown by the F-test, between healthy individuals and those with breast cancer. This suggests that Trp amino acid could be an essential biomarker for cancer diagnosis. Consequently, liquid biopsy analysis presents a valuable opportunity for early disease detection, particularly for cancer.

Colorimetric Determination of Certain Phenothiazine Drugs by Using Morpholine and Iodine-Potassium Iodide Reagents

A colorimetric method was developed for the quantitative estimation of 11 phenothiazine drugs. The method is based on the interaction of unsulfoxidized drug with morpholine and iodine-potassium iodide reagents. The interaction for all studied phenothiazine drugs yields a blue product with 2 absorption maxima: one in the range of 620-640 nm with lower molar absorptivity and the other in the range of 662-690 nm with higher molar absorptivity. The color was stable for at least 10 h. The reproducibility and recovery of the method were excellent. The method was applied successfully to the analysis of various commercially available phenothiazines in different dosage forms. The results were comparable to those obtained by official procedures. The suitability of the method for detection and estimation of promethazine excreted in urine has been suggested by preliminary experiments. Reaction products have been isolated and identified.

Spectrofluorimetric Determination of Acetaminophen with N-Bromosuccinimide

A simple, sensitive, and selective method for determination of acetaminophen based on its oxidation using N-bromosuccinimide (NBS) to produce a highly fluorescent product. Optimization of reaction variables was carried out concerning NBS concentration, pH, temperature, reaction time, and stability time. Under optimal analytical conditions, the fluorescent intensity was measured at λemission. 442 nm (excitation at λ 330 nm). The linearity range is 120–800 ng/mL with lower detection limit of 33.6 ng/mL acetaminophen. The method was applied successfully to the determination of the compound in pharmaceutical preparations, with average recovery of 100.3 ± 2%. The method was also applied successfully to the determination of the drug in spiked plasma samples, with an average recovery of 101.2 ± 1%. Interference effects of some compounds, present in combination with acetaminophen, were studied and the tolerance limits of these compounds were determined.

Highly sensitive UHPLC-DAD method for simultaneous determination of two synergistically acting antiepileptic drugs; levetiracetam and lacosamide: Application to pharmaceutical tablets and human urine

A simple and highly sensitive ultra-high-performance liquid chromatographic-diode array (UHPLC-DAD) detection method was developed and validated for the simultaneous estimation of levetiracetam (LEV) and lacosamide (LAC). It was clinically proven that the combination of LEV and LAC exhibits a synergistic effect against refractory seizures in mice, which was the motivation for the analysis of this binary mixture both in bulk and in human urine samples. The binary mixture was resolved on a Hypersil BDS C₁₈ analytical column, utilizing a mobile phase of 0.050 mol L^-1 phosphate buffer (pH 5.60), methanol and acetonitrile in the ratio (80:10:10 v/v/v) using catechol as an internal standard. The mobile phase was pumped at a flow rate of 1.2 mL min^-1 with diode array detection at 205 nm for both drugs and 270 nm for IS. Calibration curves were linear with correlation coefficient >0.9990 over the studied concentration range of 0.1-70.0 μg mL^-1 for both drugs. The developed method was reproducible with low relative standard deviation values for intra- and inter-day precision (<2.0%). Both drugs were determined in bulk, pharmaceutical formulations and human urine samples without any interference from complex matrices.

Micelle and inclusion complex enhanced spectrofluorimetric methods for determination of Retigabine: Application in pharmaceutical and biological analysis

Two new, simple, selective, and highly sensitive spectrofluorimetric methods were developed and validated for the determination of the antiepileptic drug; retigabine (RTG). The first method (Method-I) depends on enhancement of the weak native fluorescence of RTG via the use of an organized medium; sodium dodecyl sulphate (SDS) in acetate buffer (pH 3.74). The second method (Method-II) depends on the enhancement of RTG weak native fluorescence through complexation with a macromolecule; beta cyclodextrin (β-CD) in phosphate buffer (pH 3.20). A full study of different experimental parameters influencing the fluorescence intensity was carried out. In addition, a thorough investigation of the fluorescence quantum yield, fluorophore brightness and mechanism of fluorescence enhancement was performed. A seven-fold improvement in the fluorescence intensity was brought by the first method, whereas a six and half-fold enhancement of the fluorescence intensity was obtained by the second one. Linearity was achieved over wide ranges (0.05-12.5 μg mL^-1) and (0.05-15 μg mL^-1) with low limits of detection (LOD) of 10.6 and 14.3 ng mL^-1, and limits of quantification (LOQ) of 32.0 and 43.2 ng mL^-1 for (Method-I) and (Method-II), respectively. The proposed methods were validated according to ICH and US-FDA guidelines. The applicability of the proposed methods was tested for determination of RTG in its pharmaceutical dosage forms, and to study the stability of RTG under different stress conditions according to ICH guidelines including alkaline, acidic, oxidative, thermal, and photolytic stress conditions. Moreover, the high sensitivity achieved by the proposed methods permitted the determination and detection of RTG in both spiked and real rabbit plasma samples utilizing a simple protein precipitation step followed by liquid-liquid extraction method. Percentage recoveries from rabbit plasma samples were within the acceptable limits; (93.47-104.74%) and (91.33-105.70%) for (Method-I) and (Method-II), respectively.

Determination of donepezil in spiked rabbit plasma by high-performance liquid chromatography with fluorescence detection

The aim of this paper is to develop sensitive, accurate, reproducible and robust RP-HPLC with fluorescence detection for estimation of donepezil (DZ) in rabbit plasma using silodosin as the internal standard (IS). The prepared samples were quantified on reversed phase column Luna C₁₈₍₂₎ (150 × 4.6 mm i.d., 5 µm particle size) operated at room temperature using the mobile phase consisting of methanol: 0.1% acetic acid (50 : 50, v/v) at a flow rate of 1 ml min^-1. The method was fully validated according to bioanalytical validation guidelines of FDA in terms of system suitability, selectivity, sensitivity, precision and stability. It was found that the increase in peak areas followed the increase of DZ concentration in the range of 2.56-200.00 ng ml^-1 with LOD of 0.85 ng ml^-1. The method was successfully applied for the determination of DZ in rabbit plasma using manual shaking dispersive liquid-liquid microextraction.

Use of isotope hydrology in groundwater conceptualization for modeling flow and contaminant transport at northwestern Sinai, Egypt

The study area extends along northwestern Sinai coastal plain, which is considered an integral part of the Mediterranean Sea. It depends mainly on the groundwater resource for different type of human activities such as agricultural and drinking. Many programs and policies should be implemented in this area to concurrently improve the sustainability of groundwater use and manage the risks of its degradation. Leakage from some factories in Bir El-Abd might be a contamination source that would threaten groundwater. In this paper, an attempt was made using an integrated approach of the hydrogeological setting and the conjugation of the hydrogeochemical data with the stable isotope hydrology for representation of the conceptual model of the study area. Those tools give more insights on the characterization of the groundwater system with all relevant boundaries and main recharge sources of the aquifer; which is considered to be the key components of a groundwater modeling. A particular focus is placed on modeling a hypothetical accident for contaminant transport in the groundwater system, using both lead and chromium as a typical contaminant component. Further predication of the concentration of those elements has been estimated, and the safety distances of their plume have been determined. This study would be helpful in dealing with water management issues related to contaminant hydrogeology. As well, it introduces some finding for reducing the environmental risk form the industrial development at the study area.

Hydrochemical and multivariate analysis of groundwater quality in the northwest of Sinai, Egypt

The northwestern coast of Sinai is home to many economic activities and development programs, thus evaluation of the potentiality and vulnerability of water resources is important. The present work has been conducted on the groundwater resources of this area for describing the major features of groundwater quality and the principal factors that control salinity evolution. The major ionic content of 39 groundwater samples collected from the Quaternary aquifer shows high coefficients of variation reflecting asymmetry of aquifer recharge. The groundwater samples have been classified into four clusters (using hierarchical cluster analysis), these match the variety of total dissolvable solids, water types and ionic orders. The principal component analysis combined the ionic parameters of the studied groundwater samples into two principal components. The first represents about 56% of the whole sample variance reflecting a salinization due to evaporation, leaching, dissolution of marine salts and/or seawater intrusion. The second represents about 15.8% reflecting dilution with rain water and the El-Salam Canal. Most groundwater samples were not suitable for human consumption and about 41% are suitable for irrigation. However, all groundwater samples are suitable for cattle, about 69% and 15% are suitable for horses and poultry, respectively.

Selective densitometric determination of four alpha-aminocephalosporins using ninhydrin reagent

A simple, selective, and precise densitometric method for analysis of four alpha-aminocephalosporins, namely cefaclor monohydrate, cefadroxil monohydrate, cefalexin anhydrous, and cefradine anhydrous, both in bulk drugs and in formulations was developed and validated. The method employed thin-layer chromatography (TLC) aluminium sheets precoated with silica gel G 60 F(254) as the stationary phase. The solvent system consists of ethyl acetate-methanol-water with different ratios for all studied drugs (R(f) values of 0.40-0.60). The separated spots were visualized as blue to violet color after spraying with ninhydrin reagent. The linear regression analysis data for the calibration plots of all studied drugs produced a good linear relationship with correlation coefficients ranging from 0.9990 to 0.9996 and coefficients of determination ranging from 0.9986 to 0.9992 over the concentration range 2-10 microg/spot. The limits of detection and quantitation for all studied drugs ranged from 0.09 to 0.23 and from 0.27 to 0.84 microg/spot, respectively. The developed method was applied successfully for the determination of the studied drugs in their pharmaceutical dosage forms with good precision and accuracy. Also, the method can be employed as a promising stability-indicating assay.

Kinetic spectrophotometric determination of certain cephalosporins using oxidized quercetin reagent

A simple, precise and accurate kinetic spectrophotometric method for determination of cefoperazone sodium, cefazolin sodium and ceftriaxone sodium in bulk and in pharmaceutical formulations has been developed. The method is based upon a kinetic investigation of the reaction of the drug with oxidized quercetin reagent at room temperature for a fixed time of 30 min. The decrease in absorbance after the addition of the drug was measured at 510 nm. The absorbance concentration plot was rectilinear over the range 80-400 microg mL(-1) for all studied drugs. The concentration of the studied drugs was calculated using the corresponding calibration equation for the fixed time method. The determination of the studied drugs by initial rate, variable time and rate-constant methods was feasible with the calibration equations obtained but the fixed time method has been found to be more applicable. The analytical performance of the method, in terms of accuracy and precision, was statistically validated; the results were satisfactory. The method has been successfully applied to the determination of the studied drugs in commercial pharmaceutical formulations. Statistical comparison of the results with a well established reported method showed excellent agreement and proved that there is no significant difference in the accuracy and precision.

Epidermal growth factor receptor in colorectal carcinoma: correlation with clinico-pathological prognostic factors

OBJECTIVE

This study was undertaken to determine the relationship between epidermal growth factor receptor (EGFR) status in primary colorectal cancer (CRC) to different clinico-pathological prognostic factors.

METHOD

Seventy-nine primary CRC were studied using four scoring systems: 1- EGFR pharmDx score, 2- score modified from the Hercept test [J Histo cytochem, 52 (2004) 893], 3- two additive scores with different cutoff points [Mod Pathol, 11 (1998) 155], 4- two multiplicative scores with different cutoff points [Ann Oncol, 16 (2005) 102].

RESULTS

More than 10% membranous EGFR reactivity was identified in 46.8% (37/79) of the tumours. The intensity was classified as mild, moderate and strong representing 8.9%, 20.3% and 17.7% respectively. Strong correlation was found between the EGFR pharmDx and the proposed scores, at different cutoff points (P < 0.01). A strong correlation was found between EGFR expression, advanced clinical stage (P < 0.01), nodal involvement (P < 0.01) and lympho-vascular invasion (LV) (P < 0.05) in category I factors, poorly differentiated tumours in IIA (P < 0.05), infiltrative border configuration in IIB (P < 0.01), perineural invasion (PN) in III (P < 0.01), and larger tumours in IV (P < 0.01). Heterogenous staining was present in 46.3% of tumours and was associated with an increased score, LV and PN invasion and advanced clinical stage (P < 0.05).

CONCLUSION

Using a cut-off point of 10%, similar results with different scoring systems were obtained, representing standardization for EGFR interpretation. EGFR expression is correlated with conventional clinico-pathological prognostic factors.

Analysis of cephalosporin antibiotics

A comprehensive review with 276 references for the analysis of members of an important class of drugs, cephalosporin antibiotics, is presented. The review covers most of the methods described for the analysis of these drugs in pure forms, in different pharmaceutical dosage forms and in biological fluids.

Spectrofluorimetric determination of acetaminophen with N-bromosuccinimide

A simple, sensitive, and selective method for determination of acetaminophen based on its oxidation using N-bromosuccinimide (NBS) to produce a highly fluorescent product. Optimization of reaction variables was carried out concerning NBS concentration, pH, temperature, reaction time, and stability time. Under optimal analytical conditions, the fluorescent intensity was measured at lambda emission. 442 nm (excitation at lambda 330 nm). The linearity range is 120-800 ng/mL with lower detection limit of 33.6 ng/mL acetaminophen. The method was applied successfully to the determination of the compound in pharmaceutical preparations, with average recovery of 100.3 +/- 2%. The method was also applied successfully to the determination of the drug in spiked plasma samples, with an average recovery of 101.2 +/- 1%. Interference effects of some compounds, present in combination with acetaminophen, were studied and the tolerance limits of these compounds were determined.

A validated spectrofluorimetric method for determination of some psychoactive drugs

Five psychoactive drugs namely, chlorpromazine HCl, thioridazine HCl, clomipramine HCl, imipramine HCl and desipramine HCl were analyzed by a simple spectrofluorimetric method. The method is based on oxidation of the studied drugs using cerium(IV) in presence of sulphuric acid and monitoring the fluorescence of the formed cerium(III) at lambda(ex.) = 254 nm and lambda(em.) = 355 nm. All variables affecting the reaction conditions such as; cerium(IV) concentration, sulphuric acid concentration, heating time, temperature and dilution solvents were carefully studied. The effect of potential interference due to common ingredients as glucose, sucrose, lactose, citric acid and propylene glycol were investigated. A validation study of the proposed method was carried out according to USP 2002. Beer's law was obeyed for all the studied drugs in the concentration range of 0.05-1.3 microg/ml. Limits of detection range was 0.035-0.038 microg/ml and limits of quantitation of 0.116-0.125 microg/ml were obtained. The method was successfully applied for the assay of the studied drugs in pure form and in pharmaceutical dosage forms. Results were compared with official methods. The t- and F-values were calculated and compared with the theoretical values, which indicate high accuracy and good precision of the proposed method.

Differential scanning calorimetry to investigate the compatibility of ciprofloxacin hydrochloride with excipients

The compatibility between ciprofloxacin hydrochloride (CFX) and some excipients was evaluated using differential scanning calorimetry (DSC). Physical mixture, coground mixture, compressed mixture and kneaded mixture were prepared to study the effect of sample manipulation. In addition, the samples of physical mixture were also accelerated at 55 degrees C for three weeks to obtain more reliable conclusions. Different types of excipients currently used in tablet or capsule formulations namely, calcium phosphate dibasic dihydrate (Emcompress), magnesium stearate lactose, sorbitol, mannitol, croscarmellose sodium (Ac-Di-Sol), sodium carboxymethyl starch (Primojel), microcrystalline cellulose (Avicel PH 101, Emcocil) were examined. The DSC scan of CFX displayed two endothermic peaks probably as a result of a fusion process followed by a decomposition process. CFX appeared to interact with sorbitol, mannitol, Ac-Di-Sol, Primojel, Avicel PH 101 and Emcocil.

A comparative study of blood retinol and selenium in minor lower urinary lesions. A case control study

A case control study was done at Ain Shams University Hospital. Eligibility criteria were put to select cases from the clinics of urosurgery department and a control group from the clinics of surgery departments. The study was conducted in the period form 1st of February till 1st of June 1992. Both cases and control groups were subjected to an interview questionnaire, clinical examination and laboratory investigation to estimate the serum levels of retinol and selenium. Serum retinol and selenium were significantly lower among cases than among control group (p < 0.05 and p < 0.0001 respectively). Moreover, it was found that cases who lived in lower Egypt, belonged to lower socioeconomic class, smoked cigarettes and with current urinary tract infections had mean value of serum retinol significantly lower than the control group (p < 0.05). There was a significant difference in the mean blood selenium between cases and control groups who lived in Cairo (p < 0.001).

Spectrophotometric determination of some catecholamine drugs using metaperiodate

A rapid spectrophotometric procedure for the determination of isoprenaline salts, levodopa, dopamine hydrochloride, and dobutamine hydrochloride, either in the drug substances or in pharmaceutical formulations, is described. The method is based on the development of orange, red, or violet products with sodium metaperiodate in an aqueous alcoholic medium. The reaction is suggested to proceed via oxidative cyclization of the catecholamine to form an aminochrome. The wavelengths of maximum absorption range from 465 to 520 nm. The structure of the cyclization product was confirmed by ultraviolet, infrared, and nuclear magnetic resonance spectroscopy and microanalysis data.

Short communication

A simple and rapid calorimetric method for the determination of 10 sulphonamides as single entities and sulphamethoxazole in combination with trimethoprim without prior separation was developed. The method is based on the reaction of sulphonamide with phenothiazine and N-bromosuccinimide at pH 6 to produce a blue coloured product after acidification. The chromogen for all the sulphonamides was measured at 605 nm. The effect of several variables on colour development (concentration of phenothiazine and N-bromosuccinimide, time, pH) were established. Beer's Law was obeyed for all the drugs. The method was successfully applied to the analysis of single component sulphonamide tablets and ophthalmic solutions, with average results of labelled claim of 96.7 +/- 0.95 to 100.67 +/- 1.2. A good correlation was observed between molar absorptivities and pK(a) values of the sulphonamides (r = 0.9005).

Colorimetric determination of C-2 unsubstituted phenothiazines, using morpholine and N-bromosuccinimide

A colorimetric method for quantitative determination of 6 C-2 unsubstituted phenothiazine derivatives is described. The method is based on reaction of phenothiazine derivative with morpholine and N-bromosuccinimide reagents in aqueous methanol at 60 degrees C to produce a blue color. Beer's law is obeyed in a wide range of concentrations for all 6 compounds at 660 nm. Optimum analytical conditions were determined and the produced color is stable for at least 24 h. Analytical data for determination of the pure compounds are presented together with the application of the proposed method to analysis of some pharmaceutical preparations. The results compare favorably with those of official methods. Furthermore, the method is specific for intact drug in the presence of oxidative decomposition products. The reaction product has been isolated and identified and a possible reaction mechanism is suggested.

Colorimetric Determination of C-2 Unsubstituted Phenothiazines, Using Morpholine and N-Bromosuccinimide

A colorimetric method for quantitative determination of 6 C-2 unsubstituted phenothiazine derivatives is described. The method is based on reaction of phenothiazine derivative with morpholine and N-bromosuccinimide reagents in aqueous methanol at 60°C to produce a blue color. Beer's law is obeyed in a wide range of concentrations for all 6 compounds at 660 nm. Optimum analytical conditions were determined and the produced color is stable for at least 24 h. Analytical data for determination of the pure compounds are presented together with the application of the proposed method to analysis of some pharmaceutical preparations. The results compare favorably with those of official methods. Furthermore, the method is specific for intact drug in the presence of oxidative decomposition products. The reaction product has been isolated and identified and a possible reaction mechanism is suggested.

Colorimetric determination of certain phenothiazine drugs by using morpholine and iodine-potassium iodide reagents

A colorimetric method was developed for the quantitative estimation of 11 phenothiazine drugs. The method is based on the interaction of unsulfoxidized drug with morpholine and iodine-potassium iodide reagents. The interaction for all studied phenothiazine drugs yields a blue product with 2 absorption maxima: one in the range of 620-640 nm with lower molar absorptivity and the other in the range of 662-690 nm with higher molar absorptivity. The color was stable for at least 10 h. The reproducibility and recovery of the method were excellent. The method was applied successfully to the analysis of various commercially available phenothiazines in different dosage forms. The results were comparable to those obtained by official procedures. The suitability of the method for detection and estimation of promethazine excreted in urine has been suggested by preliminary experiments. Reaction products have been isolated and identified.

Fibrinolytic activity in haemophiliacs

The fibrinolytic activity was studied in 7 haemophiliacs, in comparison with 5 normals and 7 patients with disseminated intravascular coagulopathy, by determining the level of the fibrin(ogen) degradation products (FDP) in samples obtained as sera, clotting occurring naturally, and samples obtained as plasma and converted into serum by addition of thrombin-EACA. It was found that in haemophiliacs serum samples had normal FDP levels while plasma converted to serum showed high levels. This was explained by the fibrinolytic action of thrombin. Fibrinolysis was not prevented by EACA present due to the fact that it is an inhibitor of the plasminogen system but not of thrombin.