Locust bean gum hydrogels are bioadhesive and improve indole-3-carbinol cutaneous permeation: influence of the polysaccharide concentration

Abstract The locust bean gum (LBG) is a polysaccharide with thickening, stabilizing and gelling properties and it has been used in the preparation of pharmaceutical formulations. Hydrogels (HGs) are obtained from natural or synthetic materials that present interesting properties for skin application. This study aimed to develop HGs from LBG using indole-3-carbinol (I3C) as an asset model for cutaneous application. HGs were prepared by dispersing LBG (2%, 3% and 4% w/v) directly in cold water. The formulations showed content close to 0.5 mg/g (HPLC) and pH ranging from 7.25 to 7.41 (potentiometry). The spreadability factor (parallel plate method) was inversely proportional to LBG concentration. The rheological evaluation (rotational viscometer) demonstrated a non-Newtonian pseudoplastic flow behavior (Ostwald De Weale model), which is interesting for cutaneous application. The HET-CAM evaluation showed the non-irritating characteristic of the formulations. The bioadhesive potential demonstrated bioadhesion in a concentration-dependent manner. Permeation in human skin using Franz cells showed that the highest LBG concentration improved the skin distribution profile with greater I3C amounts in the viable skin layers. The present study demonstrated the feasibility of preparing HGs with LBG and the formulation with the highest polymer concentration was the most promising to transport active ingredients through the skin.

TBISTAT: An open-source, wireless portable, electrochemical impedance spectroscopy capable potentiostat for the point-of-care detection of S100B in plasma samples.

Point-of-Care (POC) testing for biomarker detection demands techniques that are easy to use, readily available, low-cost, and with rapid response times. This paper describes the development of a fully open-source, modular, wireless, battery-powered, smartphone-controlled, low-cost potentiostat capable of conducting electrochemical impedance spectroscopy for the electrochemical detection of the S100B protein captured in an ANTI-S100B functionalized thin-film gold interdigitated electrode platform to support traumatic brain injury diagnosis and treatment. EIS results from the developed potentiostat were validated with a commercial benchtop potentiostat by comparing impedance magnitude and phase values along the EIS frequency range. In addition, an experimental design was performed for detecting S100B in spiked human plasma samples with S100B concentrations of clinical utility, and a calibration curve was found for quantifying S100B detection. No statistically significant differences were found between EIS results from the developed potentiostat and the commercial potentiostat. Statistically significant differences in the changes in charge transfer resistance signal between each tested S100B concentration (p < 0.05) were found, with a limit of detection of 35.73 pg/mL. The modularity of the proposed potentiostat allows easier component changes according to the application demands in power, frequency excitation ranges, wireless communication protocol, signal amplification and transduction, precision, and sampling frequency of ADC, among others, when compared to state-of-the-art open-source EIS potentiostats. In addition, the use of minimal, easy acquirable open-source hardware and software, high-level filtering, accurate ADC, Fast Fourier Transform with low spectral leakage, wireless communication, and the simple user interface provides a framework for facilitating EIS analysis and developing new affordable instrumentation for POC biosensors integrated systems.

Fluoride release from restorative materials.

The aim of this study was to evaluate in vitro fluoride (F) release from 4 restorative materials (3M ESPE): Ketak Molar Easymix [KME - conventional glass ionomer cement (GIC)]; Rely-X luting 2 [RL2 - resin-modified GIC (RMGIC)]; Vitremer (VIT- RMGIC); and Filtek Z250 [Z250 - negative control]. Disc-shaped specimens were fabricated according to the manufacturer's instructions and placed into 10 mL of reverse osmosis water at 37°C until the analyses were done using a liquid membrane for selective F ion electrode (Orion 710). F release was evaluated every 6 h in the first day and thereafter daily during 28 days (d). The results were analyzed statistically by two-way ANOVA and Tukey's test (α=0.05). Mean F release and standard deviation values (in ppm) were: KME: 6 h- 0.34 ± 0.04; 24 h- 1.22 ± 0.30; 7 d- 0.29 ± 0.09; 14 d- 0.20 ± 0.04; 28 d- 0.16 ± 0.01; RL2: 6 h- 2.46 ± 0.48; 24 h-12.33 ± 2.93; 7 d- 1.37 ± 0.38; 14 d- 0.80 ± 0.13; 28 d- 0.80 ± 0.21; VIT: 6 h- 0.98 ± 0.35; 24 h- 4.35 ± 1.22; 7 d- 0.66 ± 0.23; 14 d- 0.40 ± 0.07; 28 d- 0.39 ± 0.08; Z250: 6 h- 0.029 ± 0.001; 24 h- 0.024 ± 0.009; 7 d- 0.023 ± 0.004; 14 d- 0.025 ± 0.001; 28 d- 0.028 ± 0.001. RL2 RMGIC released more F than the other materials in all periods. The greatest release of F occurred in the first 24 h.

Potentiometric detection of citrate in beverages using a graphite carbon electrode.

The development, evaluation and application of a simple and low-cost graphite carbon electrode for the direct determination of citrate in food samples are described here. The electrode exhibits a linear response with a slope of -29.0 ± 1.0 mV decade(-1) in a concentration range of 0.07-7.0 mmol L(-1) in 0.1 mol L(-1) KCl/1.0 mmol L(-1) phosphate buffer solution with a limit of detection of 3.0 µmol L(-1). The electrode is easily constructed at a relatively low cost and has a fast time response (within 120 s) with no significant changes in its performance characteristics. The performance of the graphite sensor was tested to determine citrate in beverage samples (juices and an isotonic drink), and the results were validated against a reference procedure. The proposed method is quick, inexpensive, selective and sensitive, and is based entirely on conventional instrumentation.

Fluoride Release from Restorative Materials

The aim of this study was to evaluate in vitro fluoride (F) release from 4 restorative materials (3M ESPE): Ketak Molar Easymix [KME - conventional glass ionomer cement (GIC)]; Rely-X luting 2 [RL2 - resin-modified GIC (RMGIC)]; Vitremer (VIT- RMGIC); and Filtek Z250 [Z250 - negative control]. Disc-shaped specimens were fabricated according to the manufacturer’s instructions and placed into 10 mL of reverse osmosis water at 37°C until the analyses were done using a liquid membrane for selective F ion electrode (Orion 710). F release was evaluated every 6 h in the first day and thereafter daily during 28 days (d). The results were analyzed statistically by two-way ANOVA and Tukey’s test (α=0.05). Mean F release and standard deviation values (in ppm) were: KME: 6 h- 0.34 ± 0.04; 24 h- 1.22 ± 0.30; 7 d- 0.29 ± 0.09; 14 d- 0.20 ± 0.04; 28 d- 0.16 ± 0.01; RL2: 6 h- 2.46 ± 0.48; 24 h-12.33 ± 2.93; 7 d- 1.37 ± 0.38; 14 d- 0.80 ± 0.13; 28 d- 0.80 ± 0.21; VIT: 6 h- 0.98 ± 0.35; 24 h- 4.35 ± 1.22; 7 d- 0.66 ± 0.23; 14 d- 0.40 ± 0.07; 28 d- 0.39 ± 0.08; Z250: 6 h- 0.029 ± 0.001; 24 h- 0.024 ± 0.009; 7 d- 0.023 ± 0.004; 14 d- 0.025 ± 0.001; 28 d- 0.028 ± 0.001. RL2 RMGIC released more F than the other materials in all periods. The greatest release of F occurred in the first 24 h.

O objetivo deste estudo foi avaliar, in vitro, a liberação de flúor (F) de 4 materiais restauradores (3M-ESPE): KME cimento de ionômero de vidro convencional (CIV) (Ketak Molar Easymix); RX2- GIC modificado por resina (RMGIC) (Rely-X luting 2); VIT-RMGIC (Vitremer); -resina composta Z250 (controle negativo) (Filtek Z250). As amostras foram confeccionadas de acordo com as instruções do fabricante e colocadas em 10 mL de água destilada 37°C até as leituras, que foram feitas utilizando um eletrodo de íon seletivo de fluoreto de membrana líquida (Orion 710). A liberação de flúor foi avaliada a cada 6 h no primeiro dia e, diariamente durante 28 dias (d). Os resultados foram analisados estatisticamente usando ANOVA a dois critérios e teste de Tukey. A média e desvio padrão de liberação de F, valores (em ppm) foram: KME: 6 h- 0,34 ± 0,04; 24 h- 1,22 ± 0,30; 7 d- 0,29 ± 0,09; 14 d- 0,20 ± 0,04; 28 d- 0,16 ± 0,01; RL2: 6 h- 2,46 ± 0,48; 24 h- 12,33 ± 2,93; 7 d- 1,37 ± 0,38; 14 d- 0,80 ± 0,13; 28 d- 0,80 ± 0,21; VIT: 6 h- 0,98 ± 0,35; 24 h- 4,35 ± 1,22; 7 d- 0,66 ± 0,23; 14 d- 0,40 ± 0,07; 28 d- 0,39 ± 0,08; Z250: 6 h- 0,029 ± 0,001; 24 h- 0,024 ± 0,009; 7 d- 0,023 ± 0,004; 14 d- 0,025 ± 0,001; 28 d- 0,028 ± 0,001. Concluiu-se que RL2 liberou mais F do que os outros materiais em todos os períodos. A maior liberação de F ocorreu nas primeiras 24 h.

Simultaneous voltammetric determination of paracetamol and caffeine in pharmaceutical formulations using a boron-doped diamond electrode.

A simple and highly selective electrochemical method was developed for the single or simultaneous determination of paracetamol (N-acetyl-p-aminophenol, acetaminophen) and caffeine (3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione) in aqueous media (acetate buffer, pH 4.5) on a boron-doped diamond (BDD) electrode using square wave voltammetry (SWV) or differential pulse voltammetry (DPV). Using DPV with the cathodically pre-treated BDD electrode, a separation of about 550 mV between the peak oxidation potentials of paracetamol and caffeine present in binary mixtures was obtained. The calibration curves for the simultaneous determination of paracetamol and caffeine showed an excellent linear response, ranging from 5.0 x 10(-7)mol L(-1) to 8.3 x 10(-5)mol L(-1) for both compounds. The detection limits for the simultaneous determination of paracetamol and caffeine were 4.9 x 10(-7)mol L(-1) and 3.5 x 10(-8)mol L(-1), respectively. The proposed method was successfully applied in the simultaneous determination of paracetamol and caffeine in several pharmaceutical formulations (tablets), with results similar to those obtained using a high-performance liquid chromatography method (at 95% confidence level).

Flow injection amperometric detection of 2'-deoxyguanosine at a ruthenium oxide hexacyanoferrate modified electrode.

A ruthenium oxide hexacyanoferrate (RuOHCF) modified electrode was developed. Hydrodynamic voltammetry was employed to demonstrate the remarkable electrocatalytic activity toward the oxidation of 2'-deoxyguanosine. The RuOHCF modified electrode was used as amperometric detector for 2'-deoxyguanosine determination in a FIA apparatus. The influence of various experimental conditions was explored for optimum analytical performance, and at these experimental conditions, the method exhibited a linear response range to 2'-deoxyguanosine extending from 3.8 to 252 micromol L(-1) with detection limit of 94 nmol L(-1). Applications in DNA samples were examined, and the results for determination of 2'-deoxyguanosine were in good agreement with those obtained by HPLC analysis. Studies on the kinetics of the in vitro consumption of 2'-deoxyguanosine by acetaldehyde were also performed.

In-soil potassium sensor system.

A potentiometric sensor system based on potassium ion-selective electrodes was developed for agricultural purposes. Sensors were built using PVC ion-selective membranes over an inner solid contact prepared with graphite-epoxy composites. A copper plate was used as a reference electrode. A two-stage electronic circuit composed of current and voltage amplifiers was designed to interface the sensors to a distributed data acquisition system. Three ion-selective sensors and three off-the-shelf temperature sensors and their associated circuits were mounted in a PVC tube to set up a soil probe. The electronic controls were placed in an airtight box fixed at the upper part of the probe. The system was evaluated in the field, where the sensors presented sensibility within the range of 69-71 mV dec(-)(1). Extracts of soil samples were analyzed by a current flame photometry approach, and the results, compared with the probe measurements, showed a linear relationship (r (2) = 0.992 and 0.995, respectively, to 5 and 20 cm depths), which implies viability and instrumentation reliability for agricultural applications.

Use of a CO2 electrode to monitor fermentations that use xenobiotic compounds as source of carbon.

Bacterial strains were isolated from contaminated waters, mud or soils. They are capable of growing in mineral medium with different chemicals as carbon source, such as aliphatic or aromatic hydrocarbons and polychlorinated biphenyls (PCBs). Most of these strains tolerate high concentrations (up to 30% v/v) of the xenobiotic substrates. This is particularly important for the development of fermenting processes to treat effluents or residues with a high content of contaminating compounds. An ion-specific potentiometric electrode (CO2) has been developed to measure CO2 production continuously. When the different strains were incubated in a mineral medium and in the presence of the corresponding substrate, a parallel between growth, substrate consumption and CO2 production was found. The developed system is suggested as an efficient and economical alternative to evaluate the potential of biodegradation by different microorganisms.

Use of a CO2 electrode to monitor fermentations that use xenobiotic compounds as source of carbon

Bacterial strains were isolated from contaminated waters, mud or soils. They are capable of growing in mineral medium with different chemicals as carbon source, such as aliphatic or aromatic hydrocarbons and polychlorinated biphenyls (PCBs). Most of these strains tolerate high concentrations (up to 30 v/v) of the xenobiotic substrates. This is particularly important for the development of fermenting processes to treat effluents or residues with a high content of contaminating compounds. An ion-specific potentiometric electrode (CO2) has been developed to measure CO2 production continuously. When the different strains were incubated in a mineral medium and in the presence of the corresponding substrate, a parallel between growth, substrate consumption and CO2 production was found. The developed system is suggested as an efficient and economical alternative to evaluate the potential of biodegradation by different microorganisms.(AU)

Automatic microelectrode compensator (AMC).

A solid-state system designed for compensation of asymmetry potentials between microelectrodes, for bioelectric measurements, is described. Advantages over the manual compensator are the following: synchronic compensation of electrodes, application to automatized systems against aging effects in electordes, high speed, and elimination of general muisances of manual circuits. Besides, the system allows to measure digitally the polarization difference and resting membrane potential with precision of +/- 1 mV.