Buffer solution

About: Buffer solution is a research topic. Over the lifetime, 6948 publications have been published within this topic receiving 112440 citations. The topic is also known as: pH buffer & buffer.

Multilayer films composed of phenylboronic acid-modified dendrimers sensitive to glucose under physiological conditions.

Abstract: Layer-by-layer (LbL) multilayer films were prepared using phenylboronic acid-modified poly(amidoamine) dendrimers and poly(vinyl alcohol) (PVA) in order to investigate the glucose sensitivity of the films. We used dendrimer derivatives modified with 3-carboxyphenylboronic acid (3CPBA-D) and 3-carboxy-5-nitrophenylboronic acid (3C5NPBA-D) to evaluate the effect of electron-withdrawing nitro groups on glucose sensitivity. PVA/3CPBA-D and PVA/3C5NPBA-D films were prepared on the surface of a quartz slide from PVA and 3CPBA-D or 3C5NPBA-D solutions at pH 7.0, 8.0, and 9.0 through boronate ester bonds. The dendrimer-based LbL films were stable at pH 7.0–9.0, whereas they decomposed in acidic media because of the instability of the boronate ester linkages. The pH threshold of decomposition was at pH 6.0–7.0 for both films. The PVA/3C5NPBA-D film was more stable than the PVA/3CPBA-D film in this range. Both films decomposed in response to glucose under physiological conditions (pH 7.4 buffer solution containing 150 mM NaCl at 37 °C), and the decomposition depended on the glucose concentration. The PVA/3C5NPBA-D film was more sensitive to glucose than the PVA/3CPBA-D film, probably due to the higher binding affinity of 3C5NPBA-D to glucose under physiological conditions. The higher response of the PVA/3C5NPBA-D film was explained by the electron-withdrawing effect of the nitro substituent on the phenylboronic acid ring. The results suggest that dendrimer-based LbL films could be used for glucose-triggered release systems.

pH-Triggered Drug Release Controlled by Poly(Styrene Sulfonate) Growth Hollow Mesoporous Silica Nanoparticles

Abstract: In the current report, hollow mesoporous silica (HMS) nanoparticles were successfully prepared by means of a hard-templating method and further modified with poly(styrene sulfonate) (PSS) via radical polymerization. Structural analysis, surface spectroscopy, and thermogravimetric characterization confirmed a successful surface modification of HMS nanoparticles. A hairy PSS was clearly visualized by high-resolution transmission electron microscopy measurement, and it is grown on the surface of HMS nanoparticles. The Brunauer-Emmett-Teller surface area and average pore size of HMS nanoparticles were reduced after surface modification because of the pore-blocking effect, which indicated that the PSS lies on the surface of nanoparticles. Nevertheless, the PSS acts as a "nano-gate" to control the release of curcumin which is triggered by pH. The drug-release profile of unmodified HMS nanoparticles showed a stormed release in both pH 7.4 and 5.0 of phosphate buffer saline buffer solution. However, a slow release (9.92% of cumulative release) of curcumin was observed at pH 7.4 when the surface of HMS nanoparticles was modified by PSS. The kinetic release study showed that the curcumin release mechanism from PSS@HMS nanoparticles followed the Ritger-Peppas kinetic model, which is the non-Fickian diffusion. Therefore, the PSS-decorated HMS nanoparticles demonstrate potential for pH-triggered drug release transport.

Effects of pH and Temperature on the Stability and Decomposition of N,N′N″-Triethylenethiophosphoramide in Urine and Buffer

Abstract: N,N',N"-Triethylenethiophosphoramide (thiotepa) was dissolved at 100 micrograms/ml in urine or in 0.1 M sodium acetate buffer and incubated at 37 degrees or 22 degrees. After 0, 15, 30, 60, 90, and 120 min of incubation, 0.1-ml samples were extracted into ethyl acetate and analyzed by gas-liquid chromatography (1.8-m X 2-mm column packed with 3% OV225 on 100/120 Supelcoport; oven at 180 degrees; injection port and nitrogen-phosphorus detector at 230 degrees). Thiotepa was more stable at 22 degrees than at 37 degrees and at pH 6 to 7 than at pH 4 to 5.5. After 2 hr of incubation at 37 degrees, thiotepa concentrations decreased by 40% at pH 5.0 but only 10% at pH 6 or 7. Although thiotepa concentrations declined as described above, alkylating activity, as assessed by p-nitrobenzyl pyridine reactivity, was stable at all temperatures and pHs tested. Partition coefficients of thiotepa degradation products into toluene, ethyl acetate, diethyl ether, and hexane were determined after 0 and 120 min of incubation in urine at pH 4.0. The extractability of alkylating activity into these organic solvents decreased dramatically after 120 min. Thiotepa degradation products were extracted from urine at pH 4.0 after 0, 30, 60, and 120 min incubation at 37 degrees and were separated by thin-layer chromatography. In addition to thiotepa (Rf 0.15), 3 degradation products possessing p-nitrobenzyl pyridine alkylating activity (Rf 0.35, 0.52, and 0.60) were observed during the course of incubation. The structures of the materials with Rf 0.35 and 0.52 were identified by mass spectrometry and indicated that thiotepa degradation occurs by successive addition of HCl molecules with opening of the aziridine rings and conversion to 2-chloroethyl moieties.