Sodium Phosphate Buffer Solution Research Articles

Hydrophilic Polyacrylamide Gels Modified with Poly-N-vinylpyrrolidone

In modern medicine, there is a need to create biologically active polymer materials for the controlled release of drugs with improved characteristics compared to existing materials. Hydrogels are an ideal basis for creating such materials due to their high water content, excellent biocompatibility, and soft consistency, which is similar to that of body tissues. Therefore, this study aimed to develop and investigate hydrogels modified with poly-N-vinylpyrrolidone (PVP) for their potential use as drug carriers. A series of polyacrylamide gels (PAAGs) were synthesized, modified with PVP at concentrations of 0.3 wt.%, 0.5 wt.% and 1.0 wt.% relative to the weight of acrylamide. The synthesis was performed through free radical polymerization of acrylamide, N,N'-methylene-bis-acrylamide, and PVP in a sodium phosphate buffer solution (pH 8.0–8.5) in the presence of an oxidation-reduction initiation system (ammonium persulfate and N,N,N′,N′-tetramethylethylenediamine). The structural characteristics, water absorption, rheological, and sorption properties of these hydrogels were analyzed. IR spectroscopic analysis revealed that the incorporation of PVP into the PAAG structure leads to alterations in the hydrogen bonding of NH groups within the polymer matrix and changes in the skeletal chain, associated with varying contents of CH, CH<sub>2</sub>, CH<sub>3</sub> groups. Rheological studies demonstrated that PVP-modified hydrogels exhibit a reduction in viscosity by 22.4-35.3% compared to unmodified PAAGs, depending on the PVP content. Despite this decrease in viscosity, the structural stability remained sufficient for the hydrophilic matrix to function effectively in drug immobilization. The water absorption studies indicated absorption values ranging from 761.9 to 1059.8%. Sorption properties were assessed using the drug dacarbazine, revealing that increasing the PVP content in the hydrogel to 0.5 wt.% and 1.0 wt.% enhanced the sorption capacity of PAAGs by 21.1% and 27.1%, respectively. Thus, the synthesized hydrogel materials exhibit sorption capacity for dacarbazine and demonstrate high water absorption values, indicating that they are promising materials for use as drug carriers in medical practice; thus, they require further medical and biological research.

Electrolyte‐gated organic field‐effect transistors with high operational stability and lifetime in practical electrolytes

AbstractA key component of organic bioelectronics is electrolyte‐gated organic field‐effect transistors (EG‐OFETs), which have recently been used as sensors to demonstrate label‐free, single‐molecule detection. However, these devices exhibit limited stability when operated in direct contact with aqueous electrolytes. Ultrahigh stability is demonstrated to be achievable through the utilization of a systematic multifactorial approach in this study. EG‐OFETs with operational stability and lifetime several orders of magnitude higher than the state of the art have been fabricated by carefully controlling a set of intricate stability‐limiting factors, including contamination and corrosion. The indacenodithiophene‐co‐benzothiadiazole (IDTBT) EG‐OFETs exhibit operational stability that exceeds 900 min in a variety of widely used electrolytes, with an overall lifetime exceeding 2 months in ultrapure water and 1 month in various electrolytes. The devices were not affected by electrical stress‐induced trap states and can remain stable even in voltage ranges where electrochemical doping occurs. To validate the applicability of our stabilized device for biosensing applications, the reliable detection of the protein lysozyme in ultrapure water and in a physiological sodium phosphate buffer solution for 1500 min was demonstrated. The results show that polymer‐based EG‐OFETs are a viable architecture not only for short‐term but also for long‐term biosensing applications.

Probing Chemical Equilibrium in Frozen Sodium Phosphate Buffer Solution by 31P Solid-State NMR.

Phosphate buffers are crucial for cryopreservative stability in pharmaceuticals, food processing, biomedical sciences, and biology. However, their freeze concentrates lack quantitative characterization, especially regarding the physicochemical properties of phosphate salt species in equilibrium at subzero temperatures. This study employs 31P solid-state NMR (ssNMR) to analyze frozen sodium phosphate (NaP) solutions, providing insights into phase composition, ionic strength, and pH. For the first time, we have directly quantified phosphate species in frozen NaP buffer, including crystallized disodium phosphate dodecahydrate (Na2HPO4·12H2O) content and the concentrations of H2PO4- and HPO42- in the freeze concentrate. This enabled the calculation of the pH as well as the ionic strength in the freeze concentrate. Trehalose effectively mitigated pH shifts in buffer solutions by preventing the selective crystallization of salt, a spectroscopic phenomenon not previously observed experimentally.

Highly efficient and reliable voltammetry food sensor for Tartrazine dye using a nanocomposite reformed electrode

Monitoring synthetic dyes in foodstuffs holds significant importance owing to their adverse effects on human health. A modified Sol-gel process was used for synthesizing mixed metal (Copper, Iron, and Nickel oxides) nanocomposites (NCs). Ternary metal NCs were characterized using FT-IR, FE-SEM, UV–Vis, and X-ray diffraction (PXRD and GID) studies. NCs (Cu/Fe/NiO) modified working electrode was fabricated for Voltammetric detection of Tartrazine dye in soft drinks. A wide concentration range (0–500 µM) was used for the Voltammetric sensing of Tartrazine dye. Voltammetric techniques like Linear Sweep Voltammetry (LSV), Differential Pulse Voltammetry (DPV), and Cyclic Voltammetry (CV) were used for the electrochemical characterization of dye. The sensor shows a good electrochemical oxidation peak in 0.1 M sodium phosphate buffer solution (pH 6.0) as a supporting electrolyte at a scan rate of 0.01 mV s−1. The impedance spectroscopy (IS) technique was applied to examine the working electrode–electrolyte interface and film resistance. A comparative study of the sensor was done with a bare glassy carbon electrode (GCE), and a Cu-wire electrode using the CV technique. The NCs modified working electrode shows a higher oxidative peak in comparison to bare GCE and Cu-wire electrodes for sensing dye. The effect of pH and scan rate on the electrochemical oxidation of Tartrazine was also examined. The lowest detection limit of Tartrazine was 0.010 µM. The fabricated working electrode shows high sensing capability for Tartrazine dye in natural and synthetic samples. The developed sensor proved to be cost-effective, and reliable for detecting food preservatives, additives, and coloring agents.

Structural and biophysical peculiarities of Nd2O3 doped borate bioglass

Different glasses with a variable composition of x Nd2O3.(46-x) B2O3.24.5 Na2O.26.5 CaO.2.6 P 2O5 (where X = 0–2.0 mol% of Nd2O3) were prepared and studied from the viewpoint of enhancing their bioactivities. All of the as-prepared glasses showed amorphous structures evidenced by the X-ray diffraction (XRD) patterns. On the other hand, XRD patterns of glasses soaked in sodium phosphate buffer solution revealed the formation of a variety of crystalline structures relevant to the formation of carbonated hydroxyapatite derivatives. According to the NMR data, the concentration of BO3 units increases at the expense of BO4 with increasing Nd2O3 content. Increasing of (BO3/BO4) molar ratio with increasing Nd2O3 plays the main role of enhancing the bioactivity of borate glasses. The percentage of BO3, BO4, and consequently N4 fraction (N4 =BO4/BO3+BO4) can simply be determined from the deconvolution process of FTIR and NMR spectra. A scanning electron microscope (SEM) and energy-dispersive x-ray (EDX) evaluation of the microstructures support the existence of crystalline HA after immersion. Both EDX and mapping of the sample after prolonged time intervals point to the homogeneity in the HA distribution of the studied sample.

A new nanocomposite-based screen-printed graphene electrode for sensitive and selective detection of 8-hydroxy-2′-deoxyguanosine

8-Hydroxy-2′-deoxyguanosine (8-OHdG) is a crucial marker used to appraise the degree of endogenous oxidative DNA damage in the human body. For routine clinical analysis, a simple, rapid, cost-effective, reliable, selective, sensitive, and portable approach is exceedingly required. In this work, we first reported on the fabrication of an electrochemical sensor based on poly(L-methionine) and gold nanoparticle-modified screen-printed graphene electrode (poly(L-Met)/AuNPs/SPGE) for the sensitive and selective detection of 8-OHdG in the presence of uric acid at a normal level in urine, which is the major interference when using square wave voltammetry. Sodium phosphate buffer solution containing sodium chloride and sodium dodecyl sulfate was used as the supporting electrolyte for specific detection of 8-OHdG. The oxidation peaks of 8-OHdG and uric acid can be obviously separated. Under optimal conditions, the linearity between the anodic peak current and the 8-OHdG concentration was obtained within the range of 1–50 µM, and the limit of detection (3SD/Slope) and limit of quantification (10SD/Slope) were found to be 92 and 306 nM, respectively. This fabricated sensor was successfully applied to determine the 8-OHdG concentration in biological fluid samples with good selectivity, sensitivity, reliability, reproducibility, accuracy, and precision. The promising results demonstrated that this proposed methodology could be useful for medical personnel in diagnosing the disease risk from 8-OHdG levels at an early stage.

A New Electrochemical Sensor Based on Carbon Black Modified With Palladium Nanoparticles for Direct Determination of 17α‐Ethinylestradiol in Real Samples

AbstractElectrochemical sensors to quantify concentrations of emerging pollutants have attracted great attention from the industry and scientific community. Nanomaterials such as carbon black have been applied in sensors to identify substances that are toxic to the environment and human health due to their excellent electroanalytical properties. The aim of the study was to develop a novel electrochemical sensor for the endocrine disruptor hormone determination. To our knowledge, for the first time the synthesis of material based on carbon black containing immobilized palladium nanoparticles, with the application for the hormone ethinylestradiol, is reported in the literature. The material was synthesized, characterized, and applied to the determination in tap water and human urine of the synthetic hormone 17α‐ethinylestradiol (EE2), which is currently considered an emerging pollutant. The morphology, structure and electrochemical performance of the sensors were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). Differential pulse voltammetry (DPV) in sodium phosphate buffer solution at pH 5.0 allowed the generation of a method to quantify the concentration of 17α‐ethinylestradiol in a linear range of 0.5–119.0 μmol L−1, obtaining 81.0 nmol L−1 of calculated limit of detection (LOD). The system was efficient in detecting 17α‐ethinylestradiol in real urine samples and showed no interferences for ascorbic acid, uric acid, progesterone, and dopamine. It is noteworthy that the results obtained showed good recovery values, considering that the urine samples were not previously treated or pre‐concentrated, which suggests the development of an electrochemical sensor that works in situ and in real time to monitor relevant substances in the control clinical and environmental, with the possibility of point‐of‐care analyses.

Crosslinking Efficacy and Cytotoxicity of Genipin and Its Activated Form Prepared by Warming It in a Phosphate Buffer: A Comparative Study.

The aim of the present study was to compare the acute and cumulative cytotoxicity of intact (n-GE) and warmed genipin (w-GE), while investigating the differences in crosslinking capabilities of these two genipins by rheological and mechanical tests. The n-GE solution was prepared by dissolving genipin powder in a sodium phosphate buffer solution. The w-GE solution was prepared by warming the n-GE solution at 37 °C for 24 h. The mechanical tests for chitosan (CH)/genipin gels showed the crosslinking rate of w-GE was much greater than that of n-GE up until 6 h after preparation, whereas the degree of crosslinking of CH/n-GE gels became higher at 12 h. The ISO 10993-5 standard method, which is established specifically for evaluating cumulative cytotoxicity, determined equivalent IC50 for w-GE (0.173 mM) and n-GE (0.166 mM). On the other hand, custom-made cytotoxicity tests using a WST-8 assay after 1 h of cultivation showed that the acute cytotoxicity of w-GE was significantly higher than that of n-GE at concentrations between 0.1–5 mM. The acute cytotoxicity of w-GE should be taken into consideration in its practical uses, despite the fact that the much faster crosslinking of w-GE is useful as an effective cross linker for in-situ forming gels.

Extracting Sweetening and Bioactive Compounds From Stevia Rebaudiana Using Cellulase Enzyme

This study was conducted to find out the sweetener and bioactive compounds in the Stevia plant’s enzyme extract and its antioxidant and antibacterial effect. The enzyme extract was used in a ratio of 1:15 (w: v) with the use of sodium phosphate buffer solution (pH=4) in an equal mixing ratio with the enzyme. Extraction was carried out at 55°C with a time of 25 minutes to extract and determine steviol glycosides using HPLC. Stevioside and Rebaudioside-A (5.101 and 3.027 mg/g) were obtained, respectively. The study showed that Stevia contains high amounts of phenols and flavonoids (83.052 and 71,765) mg/ml, respectively. The enzyme extract gave an antioxidant activity of 71.367% compared to BHT which gave an activity of 77.267%. It gave the highest inhibitory activity against Bacillus subtilis, which was 14 mm, followed by Staphylococcus aureus and E. coli. The bioactive compounds were diagnosed by GC-MS and contained important bioactive compounds such as Hydroxydehydrostevic acid (steviol), 1,2-Benzenediol, 4-Ethylcatechol, 9-Octadecenamide, (Z)-, Isosteviol methyl ester, gamma-Sitosterol.

Kinetics of the release of brilliant green from nanoporous polylactide obtained by a crazing mechanism

Structurally variable nanoporous polylactide (PLA) films containing brilliant green (BG) as a functional antiseptic additive have been obtained by a crazing mechanism. The in vitro release of BG from the porous PLA films into a sodium phosphate buffer solution at 37 °C has been examined by spectrophotometry.

The influence of sodium phosphate buffer on the stability of various proteins: Insights into protein-buffer interactions

Present study delineates the effects of sodium phosphate buffer (PBS) solutions on the stability of various proteins including lysozyme (Lys), bromelain (BM), hemoglobin (Hb), and human serum albumin (HSA). Different spectroscopic methods such as UV–visible, steady state fluorescence, temperature dependent fluorescence spectroscopy, Fourier transforms infrared spectroscopy (FTIR), circular dichroism (CD) spectroscopy and dynamic light scattering (DLS) show that PBS buffer protects protein structures. Efficacy of PBS stabilization from external additive factors follows order as lysozyme > BM > Hb. The thermal stability of HSA in PBS buffer solution was not detected, since no distinct and clear fluorescence transition was observed. However, results from other biophysical techniques reveal the native structure of HSA stabilized in presence of PBS. Moreover, increasing concentration of PBS also provides structural stabilization of HSA. This confirms the potentiality of PBS buffer as protecting agents for the proteins/enzymes. However, in case of Hb structure perturbed with the addition of higher concentrations of PBS. Our study confirms that efficacy of protein stabilization depends on type and concentration of buffer used. The present study is very useful for providing the alternative media to replace traditional volatile organic compounds or expensive modern solvents for biochemical applications.

A Sensitive and Optimized HPLC-FLD Method for the Simultaneous Quantification of Hydroxychloroquine and Its Two Metabolites in Blood of Systemic Lupus Erythematosus Patients.

Quantification of hydroxychloroquine (HCQ) and its two metabolites desethylchloroquine and desethylhydroxychloroquine in human blood can provide insight into the pharmacokinetic/pharmacodynamic characteristics of HCQ for the treatment of systemic lupus erythematosus (SLE), which is crucial for the optimization of the therapy. A simple, sensitive and optimized high performance liquid chromatography with fluorescence detection method has been developed and validated for the simultaneous determination of HCQ and its two metabolites in human blood. After addition of internal standard chloroquine, the blood sample was deproteinized with 2-fold acetonitrile and separated on an YMC-Triart C18 column (250×4.6mm, 5μm) with a mobile phase of 20mM sodium phosphate buffer solution containing 0.25% triethylamine (pH8.0)-acetonitrile (60:40, v/v). The analytes were detected by using fluorescence detection at an excitation and emission wavelength of 337 and 405nm, respectively. The method was linear over the range of 3-3000ng/mL for all three analytes and the chromatographic run time was 9min. The values for intra- and inter-day precisions were ranged from 1.3 to 7.3. This method was successfully applied to quantify the concentrations of HCQ and its two metabolites in blood of 92 SLE patients.

The Characterization of Chitosan-ZnO Nanoparticles Modified Screen-Printed Copper Electrodes as the Analytical Sensor

Characteristics of chitosan-ZnO-modified screen-printed copper electrodes showed good sensitivity as a sensor which characterized by using cyclic voltammetry. The copper electrode was prepared for the sensitivity testing before being used as a sensor substrate material, the tests carried out in sodium phosphate buffer solution (BSP), the use of BSP as a standard test in this study.

English

Pesticides are identified as hazardous contaminants due to high toxicity and persistence in the environment. In this context, it is necessary to monitor these pollutants in the environment in situ, with the use of low cost analytical techniques and of quick response. Biosensors are presented as a complementary analytical tool to more complex techniques, such as chromatography. The present work aims to develop, in a simple and low cost way, an amperometric biosensor for the detection of simazine in aqueous samples from the inhibition of the enzyme peroxidase extracted from the pinto bean (Phaseolus vulgaris L.). For the development of the biosensor, the enzyme peroxidase was extracted in sodium phosphate buffer solution, of pH 6.0, and pre-purified by ammonium sulfate precipitation 40% (w / v) salt saturation to 50.0 ml of the protein extract. Peroxidase was characterized by electrophoresis and immobilized on silica-titanium oxide, synthesized by the sol-gel method in the proportions of 70% / 30% respectively. The biosensor showed linearity in the concentration range between 1.0 and 6.0 μgL-1 of simazine (R2 = 0.989) in the potential range 0.20 V to 0.30 V vs Ag / AgCl by the square wave voltammetry technique. The curve was obtained in the presence of 2.0 mgL-1 phenol and 3% H2O2 (v / v)), where the current density signal decreased in the presence of successive additions of the simazine inhibitor. The biosensor was applied to a standard simazine-fortified sample and detected the presence of simazine at the concentration of 35.05 μgL-1. Even showing a relative percentage error of 12.63%, when compared with the result of the analysis by high performance liquid chromatography, the biosensor is useful to monitor the presence or absence of the simazine pesticide in the solution. Key words: Simazine, Biosensor, Carioca beans (Phaseolus vulgaris L.).

Effect of combination of electrolyte and buffer on electrical production in fuel cell microbial system withPseudomonas sp.in molasses substrate

MFC is a bio-electrochemical system driving an electric current by using high-energy bacteria and oxidants. This research aimed to investigate the effect of electrolyte and buffer on electrical production using Pseudomonas sp. In Molasses substrate. The method in this research was the double compartment that consist of anode and cathode chambers. Both were related by salt bridge. This study showed that the addition of a combination of KMnO4electrolyte solution with sodium phosphate buffer solution obtained a maximum potential difference of 0.67 V. The result also revealed that the combination of KMnO4electrolyte solution with Potassium Phosphate Buffer solution produced a 1.44 mA maximum current with power density of 660.82 mW/m2.

Phosphorus removal mechanisms from domestic wastewater by membrane capacitive deionization and system optimization for enhanced phosphate removal

Membrane capacitive deionization (MCDI) is an emerging technology for effective removal of charged pollutants from the water sources including domestic wastewater. In this work, a lab-scale MCDI system was employed to investigate its feasibility for effective phosphorus removal from domestic wastewater. The effect of phosphate equilibrium reactions on the ion sorption behaviour was studied in sodium phosphate buffer solution at typical pH range maintained in a real domestic raw wastewater effluent (between 6.5 and 8.5). The results demonstrated that phosphate equilibrium system has positive impact on the degree of inorganic phosphorus (P) adsorption capacity in aqueous solution. In addition, the ion selectivity of P over other co-existing anions (Cl-, SO42-) were experimentally studied using a synthetic wastewater solution. And it was found that the preferential electrosorption sequence of the competitive anions is: Cl-> SO42- > P, while the initial ion concentration order in the synthetic feed solution is: Cl- 1.90 mM> P (0.40 mM)> SO42- (0.32 mM). The experiments with diverse operating conditions revealed that the optimal adsorption of inorganic phosphorus over chloride and sulphate can be achieved in some extent with slower flow rates and higher applied potentials (less than 1.23 V).

Sulfur Capacity of Sodium Phosphate Buffer Solution

Sulfur Capacity of Sodium Phosphate Buffer Solution

Effect of Pharmaceutical Excipients on Cloud Point of Amphiphilic Drug Venlafaxine Hydrochloride Solutions

One of the characteristics of amphiphilic drug which may be a disadvantage is the phase separation or clouding phenomenon on heating which depends upon the nature, structure and concentration of the amphiphile, pressure, presence of additives, etc. The effect of various types of pharmaceutical excipients such as hydrotropes and β-cyclodextrin on the cloud point (CP) behaviour of amphiphilic drug venlafaxine hydrochloride (VFN) in sodium phosphate buffer sodium phosphate buffer (pH 6.7) solutions have been investigated in the present study. The anionic hydrotropes (sodium benzoate and sodium salicylate) increase the CP of VFN, when added in low concentrations, whereas at high concentration, decrease it. Cationic and non-ionic hydrotropes increase the CP of VFN solution at all the concentration. β-cyclodextrin behave like simple sugar is found to decrease the CP of the drug solutions at all concentrations. The thermodynamic parameters are also evaluated: where ΔG° is found to be negative and ΔH° and TΔS° values are negative as well as positive depending upon type and nature of hydrotropes. Based upon the result, storing formulations at temperatures significantly higher than the cloud point may result in phase separation and instability.

Development and Validation of an HPLC Method for the Simultaneous Determination of Flurbiprofen and Chlorhexidine Gluconate

Flurbiprofen (FBP) is a strong nonsteroidal anti-inflammatory drug which has analgesic, antipyretic and anti-inflammatory effects. Chlorhexidine gluconate (CHG) is a potent antibacterial agent. Nowadays, FBP and CHG as a combination are used in some pharmaceutical products. In this study, an analysis method was developed for the simultaneous determination of FBP and CHG using high performance liquid chromatography (HPLC) technique. During analysis, Agilent Poroshell 120 EC-C18 column was used as stationary phase with a guard column having the same properties. Sodium phosphate buffer solution (100 mM, pH 2.5) and acetonitrile were used as mobile phase. The chromatography was performed by gradient elution at a flow rate of 0.5 mL min−1. Analytes were detected at 248 nm using a diode array detector (DAD). The developed method was validated according to United States Pharmacopoeia. It was found to be linear in the concentration range between 1 and 25 ppm. Determination coefficient was 0.9999 for FBP and CHG. The developed method was applied successfully for HPLC analysis of commercial pharmaceutical products including FBP and CHG.

Interactions of glycine with aqueous solutions of sodium phosphate buffer at T = (288.15, 293.15, 298.15, 303.15, 308.15, 310.15, 313.15, 318.15, 323.15 and 328.15) K: Volumetric and UV absorption studies

Interactions of glycine with sodium phosphate buffer have been investigated by volumetric and UV absorption studies. Densities have been measured for glycine in water of pH=(1.00, 7.40 and 13.40) and in 0.1M, 0.5M and 1M aqueous sodium phosphate buffer (NaPB) solutions as a function of concentration at T=(288.15 to 328.15) K and at pH=(1.00, 7.40 and 13.40) by using digital density meter. Apparent molar volumes (V∅) and partial molar volumes (V2o) obtained from these density data have been used to calculate partial molar volumes of transfer (∆trV2o) from water to aqueous sodium phosphate buffer solutions, which are positive for zwitterionic and deprotonated form of glycine. Interaction coefficients have been obtained from McMillan-Mayer's approach. Effect of temperature on these thermodynamic properties have been studied by determining the partial molar expansibilities (∂V2o/∂T)P at infinite dilution and their second order derivative (∂2V2o/∂T2)P at different temperatures and at pH=(1.00, 7.40 and 13.40). Hydration number (nH) of glycine at pH7.40 have been determined from the V2o data. The results have been rationalized in terms of various interactions taking place in these systems. Further, absorption spectra have also been recorded for the present system with the help of UV–visible spectrophotometer at 298.15K which is helpful in interpreting the possible molecular interactions between glycine and NaPB.