Influence of the ionic strength on the physicochemical properties of methotrexate-loaded chitosan polyelectrolyte complexes

Abstract Polyelectrolyte complexes (PECs) as drug delivery systems are widely explored since they are easily obtained by coacervation and biopolymers can be associated. However, particle distribution is a challenging critical parameter that has been infrequently focused. This work evaluated the effect of NaCl concentration on the physicochemical properties of PECs based on chitosan and hypromellose loaded with methotrexate. The particle size, zeta potential and polydispersity index (PdI) were determined by DLS, besides of drug entrapment efficiency (EE) and in vitro drug release profile determination. Particle size decreased while NaCl concentration rised, achieving a narrower size distribution of (345±79 nm) and PdI (0.285±0.067) with 200 mmol/L NaCl. The higher the NaCl concentration, the lower the zeta potential at acid pH. The EE was kept similar ((28.2±4.5) %) from 0 to 300 mmol/L NaCl, while 400 mmol/L NaCl impaired the drug entrapment. The addition of (200 and 300) mmol/L NaCl did not affect the drug release profile, but it was faster with (100 or 400) mmol/L. In conclusion, the addition of 200 mmol/L NaCl reduced particle size and PdI with no changes in the EE and drug release. Therefore, the ionic strength plays an important role on PECs development.

Evaluation of modified IAT with twoself-made low ionic-strength solutions / 中国输血杂志

【Objective】 To explore the clinical applications of low ionic strength salt solution polyethylene glycol (LISS-PEG) and low ionic strength salt solution bovine serum albumin (LISS-BSA) in the indirect antiglobulin test (IAT). 【Methods】 The common standard red blood cell(RBC) IgG irregular antibodies (anti-D, anti-M, anti-N, anti-S, anti-s, anti-Jka, anti-Jkb, anti-Fya, anti-Fyb, anti-Dia, anti-K) were reacted with RBCs with corresponding antigens in IAT with LISS-PEG and LISS-BSA modification for 5-minute and 10-minute incubations, and then compared the results with conventional IAT. One hundred of blood samples from patients presenting irregular antibodies of erythrocyte IgG were selected to observe the effect of these two self-made modification. The agglutination intensity was recorded by AABB scoring method. 【Results】 No difference was noticed in IAT intensity reaction between LISS-PEG 5-minute and 15-minute incubation (P>0.05), nor between 5-minute/15-minute LISS-BSA incubation and conventional IAT (P>0.05). However, LISS-PEG modification demonstrated a significant superiority over the conventional technique just after incubation with 5 minutes(P<0.05). 【Conclusion】 Using the self-made LISS-PEG as the enhancement medium allows not only reduced incubation time (5 minutes) but also increased intensity of the reaction, which shortens the cross-matching time for emergency blood transfusion and is worthy of popularization.

Microbial Adhesion of Salmonella Muenster, Salmonella Kentucky, Salmonella Newport and Salmonella Kiel: Effect of Ionic Strength on Physicochemical Surface Properties

Aims: The aim of this study was to investigate the ability of adhesion of different Salmonella’s serovars (S. Newport, S. Muenster, S. Kentucky and S. Kiel) isolated from food surfaces under two ionic strengths (0.1M; 0.001M), in order to understand the influence of environmental characteristics on their adhesion behaviour. Place and Duration of Study: Laboratory of bioprocesses and biointerfaces; Sciences and technologies Faculty (FST) between February 2015 and July 2015. Methodology: Physicochemical properties (hydrophobicity, electron donor- electron acceptor) of cells surfaces and substratum surface were determined using contact angle method. The adhesion of Salmonellastrains on glass was studied using optical microscope and Matlab program. Results: Salmonella strains showed similar cell surface physicochemical properties under low and high ionic strength except for S. Newport and S. Kentucky at low ionic strength. In addition, all Salmonella strains presented strong adhesion ability at low ionic strength (0,001M) especially for S. Newport and S. Kentuckyserovars. Conclusion: The results presented in this work could contribute to understand and control the microbial adhesion of Salmonella serovars to inert surface depending on environmental conditions.

In Vitro Dissolution Behaviors of Diclofenac Sodium Enteric-Coated Tablets / 中国药学杂志

OBJECTIVE: To investigate and compare the dissolution behaviors of diclofenac sodium enteric-coated tablets from Beijing Novartis, Turkey Novartis and German Novartis respectively. METHODS: According to the dissolution test METHODS: in Chinese Pharmacopoeia, the dissolution curves of the preparations in various media were investigated. Whether the dissolution stage in acidic medium has influence on the dissolution behavior as well as the influence of the ionic strength of buffer medium were investigated. RESULTS: The dissolution curves of diclofenac sodium enteric-coated tablets in media of pH 1.0, 5.5, 6.0 and 6.8 could be used as the characteristic dissolution curves of the preparation. The dissolution behaviors of the three preparations after being dissolved in acidic medium for 2 h were similar; the dissolution behaviors were quite different without the dissoulution stage in acid medium; the larger the ionic strength of the buffer medium was, the faster the dissolution rate of the enteric coated tablets was. CONCLUSION: The dissolution behavior of diclofenac sodium enteric-coated tablets depends on the dissolution rates of the enteric coating and the tablet core. The RSD of the dissolution rate just after the formulation starts to dissolute is large; the dissolution phase in acidic medium and the ionic strength of the buffer medium has influence on the dissolution behavior. There is difference in the in vitro dissolution behaviors of diclofenac sodium enteric-coated tablets from manufacturers in different areas of the same group. This study may provide data support for the selection of multi-source reference preparations in the evaluation of generic drug conformance, and plays an important role in guiding the prescription screening and bioequivalence risk assessment.

Purification of inulinases by changing the ionic strength of the medium and precipitation with alcohols

ABSTRACT The present study evaluated the purification of inulinase by changing the ionic strength of the medium by addition of NaCl and CaCl2 followed by precipitation with n-propyl alcohol or iso-propyl alcohol. The effects of the concentration of alcohols and the rate of addition of alcohols in the crude extract on the purification yield and purification factor were evaluated. Precipitation caused an activation of enzyme and allowed purification factors up to 2.4-fold for both alcohols. The purification factor was affected positively by the modification of the ionic strength of the medium to 0.5 mol.L-1 NaCl before precipitation with the alcohol (n-propyl or iso-propyl). A purification factor of 4.8-fold and an enzyme yield of 78.1 % could be achieved by the addition of 0.5 mol.L-1 of NaCl to the crude extract, followed by the precipitation with 50 % (v/v) of n-propyl alcohol, added at a flow rate of 19.9 mL/min.

Effect of Ionic Strength on Stability of Methotrexate-loaded Dendrimer Nanoparticles / 医药导报

Objective To investigate the influence of ionic strength on the stability of the methotrexate-loaded dendrimer nanoparticles. Methods The influences of different ions (Na+,Cl-) and different concentrations of sodium chloride on the stability of the nanoparticles were studied. The particle size was measured by dynamic light scattering(DLS) and drug-loading content was determined by high-performance liquid chromatography (HPLC) in order to evaluate the stability. Results The Cl- was finally verified to play an important role in stabilizing the nanoparticles and the effective concentration of the sodium chloride was recommended to be below 1. 80% . Conclusion The recommended concentration (less than 1. 80% ) of the sodium chloride significantly improves the stability of the nanoparticles and benefits for long term storage.

Effects of Water Chemistry on Aggregation and Soil Adsorption of Silver Nanoparticles

OBJECTIVES: In this study, we investigated the influence of ionic strength and natural organic matter (NOM) on aggregation and soil adsorption of citrate-coated silver nanoparticles (AgNPs). METHODS: Time-resolved dynamic light scattering measurements and batch adsorption experiments were used to study their aggregation and soil adsorption behaviors, respectively. RESULTS: The aggregation rate of AgNPs increased with increasing ionic strength and decreasing NOM concentration. At higher ionic strength, the AgNPs were unstable, and thus tended to be adsorbed to the soil, while increased NOM concentration hindered soil adsorption. To understand the varying behaviors of AgNPs depending on the environmental factors, particle zeta potentials were also measured as a function of ionic strength and NOM concentration. The magnitude of particle zeta potential became more negative with decreasing ionic strength and increasing NOM concentration. These results imply that the aggregation and soil adsorption behavior of AgNPs were mainly controlled by electrical double-layer repulsion consistent with the Derjaguin-Landau-Verwey-Overbeek theory. CONCLUSIONS: This study found that the aggregation and soil adsorption behavior of AgNPs are closely associated with environmental factors such as ionic strength and NOM and suggested that assessing the environmental fate and transport of nanoparticles requires a thorough understanding of particle-particle interaction mechanisms.

Enzymatic and biochemical characterization of Bungarus sindanus snake venom acetylcholinesterase

This study analyses venom from the elapid krait snake Bungarus sindanus, which contains a high level of acetylcholinesterase (AChE) activity. The enzyme showed optimum activity at alkaline pH (8.5) and 45ºC. Krait venom AChE was inhibited by substrate. Inhibition was significantly reduced by using a high ionic strength buffer; low ionic strength buffer (10 mM PO4 pH 7.5) inhibited the enzyme by 1. 5mM AcSCh, while high ionic strength buffer (62 mM PO4 pH 7.5) inhibited it by 1 mM AcSCh. Venom acetylcholinesterase was also found to be thermally stable at 45ºC; it only lost 5% of its activity after incubation at 45ºC for 40 minutes. The Michaelis-Menten constant (Km) for acetylthiocholine iodide hydrolysis was found to be 0.068 mM. Krait venom acetylcholinesterase was also inhibited by ZnCl2, CdCl2, and HgCl2 in a concentrationdependent manner. Due to the elevated levels of AChE with high catalytic activity and because it is more stable than any other sources, Bungarus sindanus venom is highly valuable for biochemical studies of this enzyme.(AU)

Nickel adsorption by variable charge soils: effect of pH and ionic strength

The effects of pH and ionic strength (I) on Ni adsorption in variable charge soils were evaluated by laboratory batch experiments. Experimental results fitted the Langmuir model. Maximum adsorption (Ads max) ranged from 260-2818 mg kg-1 (topsoil) to 532-1541 mg kg-1 (subsoil). Nickel affinity (K L) was higher in the subsoil samples (0.022-0.236 L kg-1) than in topsoil (0.003-0.049 L kg-1). Adsorption envelopes showed sharp increase in Ni adsorption (20-90 percent) in the 4.0-6.0 pH range. Nickel adsorption was affected by I and specific adsorption predominated in the 3.0-5.0 pH range, while above pH 5.0, it was adsorbed by electrostatic mechanisms. Negative values of free energy variation (ΔG) and the separation factor K R<1 indicated that Ni adsorption reaction was favorable and occurred spontaneously, especially when pH increase. Chemical and mineralogical soil attributes should be considered as criteria for selecting the areas for disposal of residues containing Ni to minimize the impact on the environment.

Oxidation of oxymyoglobin by poplar plastocyanins a and b.

Oxidation of oxymyoglobin [MbO2 (Fe2+)] by isoplastocyanins a (PCa) and b (PCb) was experimentally investigated and the corresponding redox reaction was modeled using the physicochemical parameters of the isoforms to study the effect of the dimorphism. The kinetic curve of oxidation of MbO2 (Fe2+) by oxidized PCa [PCa(Cu2+)] and PCb [PCb(Cu2+)] and the pH-dependence of the rate constant k1 were determined. In the range of pH 4.8-9.0, PCb reacts with higher k1, compared with PCa. For example, at pH 7.0, k1(PCb) = 4 × 102 M-1s-1, whereas k1(PCa) = 2 × 102 M-1s-1. The observed values of ΔE0 for the reaction pairs Mb-PCa and Mb-PCb were -304 mV and -319 mV, respectively. The effect of the ionic strength (µ) on the rate of the electron transfer was also studied. It was found that: (i) the net charge Z1 of PCa and PCb fully corresponds to that calculated by their primary structures and Z2 of Mb corresponds to that calculated by its titration curve; (ii) the ln k as function of √¯µ was similar for both PCa and PCb; (iii) the curve of the reaction PCb Mb (pH 7.0) was shifted towards higher values of k, in agreement with the larger net negative charge of PCb; and (iv) the character of the electrostatic interactions remained unchanged by a replacement of PCa by PCb and by the change of pH from 7.0 to 4.8.

Phosphorus availability in a low pH highly weathered soil as affected by added salts / Disponibilidade de fósforo num solo ácido afetada pela aplicação de sais

Concentration and identity of cations and anions in the soil solution may affect soil P reactions and thus P availability. The magnitude of these reactions was evaluated in this research after application of various salts to a highly weathered low pH soil. Chloride, nitrate, and sulfate salts of Na, NH4, K, Ca, Mg, Sr, or Cu were added to the soil after addition of 360mg P/kg trying to simulate ion concentrations around granules of fertilizers in the soil. Thirty days later, P was determined in the soil solution (Pli) and on the solid phase (Psi). The soil samples of some treatments were leached with water and three days later a new soil solution was displaced. Separate addition of all salts increased Pli, except NaCl at the lowest rate. The increase of Pli was highly associatcd with amount of native cations displaced to the soil solution by the applied salts. Salt solubility, concentration, and sometimes identity of cation and anion also influenced Pli. Some salts decreased Psi, but this was not correlated with any soil property measured. The effects caused by salts on Pli and Psi disappeared after leaching the soil samples.

A concentração eletrolítica e o tipo de cations e anions da solução do solo podem afetar as reações do fósforo com possíveis reflexos na disponibilidade de P aos vegetais. Nessa pesquisa quantificou-se o efeito de vários sais nos valores das determinações analíticas que afetam a disponibilidade de fósforo. Sais de nitrato, cloreto e sulfato foram aplicados a amostras de um alfisol ácido após a aplicação de 360mg P/kg, simulando concentrações que ocorrem no solo ao redor de grânulos de fertilizantes. Fósforo lábil (Psi) e P na solução do solo (Pli) foram determinados após 30 dias de incubação, antes e depois de percolar água pelo solo. Todos os sais aumentaram a concentração de P na solução do solo, exceto a menor dose de NaCl. O aumento do Pli foi correlacionado com a quantidade de cations originalmente no solo deslocados para a solução do solo. Solubilidade, concentração, e a espécie dos cations e anions aplicados também exerceram efeito no Pli. Alguns sais diminuíram o Psi porém esse decréscimo não se correlacionou com nenhuma determinação efetuada. A percolação de água eliminou os efeitos ocasionados pelos sais nos valores de fósforo.

Effects of pH and ionic strength of release media on in vitro drug released from carboxymethyl konjac glucomannan pellets / 中成药

AIM:To study the effects of pH and ionic strength of release media on in vitro berberine hydrochloride(BH)released from carboxymethyl konjac glucomannan(CMKGM)pellets and to evaluate its characteristics.METHODS:The CMKGM pellets were prepared by ionotropic gelation with BH as the model drug.In vitro drug release,dynamic swelling and erosion percent of the pellets were studied respectively in release media with different pH(pH 1.0、pH 5.0、pH 6.8、 pH 7.4)or different ionic strength(pH 6.8 PBS with 2、4、6、8 g/L NaCl).The amount of BH released were confirmed in different equation to evaluate BH release mechanism of the pellets.RESULTS:With the increased of pH value or the decreased of ionic strength of the release media,the swelling ratio and erosion percent of the pellets increased,the BH release rate increased.The release of BH in HCl solution was film-controlled and exhibited zero order kinetic equation;the release of BH in PBS was non-Fickian release that coupled diffusion and erosion of the pellets matrix,exhibited Peppas equation.CONCLUSION:The swelling ratio and erosion percent of CMKGM pellets is related to pH and ionic strength of the release media,which influence BH released and release mechanism of the pellets.

Erythrocyte stability under imposed fields.

Lysis of erythrocytes offers an unique opportunity to probe the fine structure of the bilayer as a function of its state of energization. Critical monitoring of the volumes, ion fluxes and related measures in erythrocytes exposed to a variety of milieu and treatments showed that one can critically distinguish the nature of the prelytic perturbations and the proximate forces actually responsible for the disruption of the membranes among surface charge density, elastic energy etc.

INCREASED SENSITIVITY OF MN TYPING FOR BLOODSTAINS USING A LOW IONIC STRENGTH SOLUTION / 中国法医学杂志

The absorption-elution test using low ionic strength solution (LISS) has been compared with the test using normal saline in MN typing of 258 bloodstain samples stored 1 to 6 years. The accuracy rate was 94.57％ using LISS method. The present study indicated that the LISS method is more sensitive than tests carried out in normal saline.