Release Rate In pH Research Articles

Structure and release properties of pyrethroid/sulfobutyl ether β-cyclodextrin intercalated into layered double hydroxide and layered hydroxide salt.

The aim of this study was to realize the intercalation of the pyrethroid pesticides beta-cypermethrin (BCT) and lambda-cyhalothrin (LCT) into ZnAl-layered double hydroxides (LDH) and NiZn-layered hydroxide salt (LHS). BCT (LCT)/SBECD-LDH and BCT (LCT)/SBECD-LHS hybrids were obtained with the aid of sulfobutyl ether β-cyclodextrin (SBECD) through one step method. The hybrids were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetry and differential thermal analysis (TGA/DTA). The hybrids based on LHS had larger basal spacing than those on LDH. The LDH-hybrids prepared in N-methylpyrrolidone (NMP) had larger basal spacing than those in ethanol. These results were discussed in terms of the matrix structure and solvent properties. The supramolecular structure of the hybrid was reasonably proposed. Furthermore, the release properties of BCT (LCT) from the hybrids were investigated and discussed in two media. The release rate in pH = 5.0 was slower than that in pH = 6.8. The accumulated release amount of pesticide in pH = 5.0 was lower than that in pH = 6.8. LHS-hybrids synthesized in ethanol exhibit a sustainable release property. These depend on the inclusion complexes’ arrangement and release medium. The release kinetic processes could be described by pseudo-second order and parabolic diffusion models. The release behavior can be controlled by adjusting the synthesis conditions and the releasing media. This provides the guidance for the application of SBECD and LDH (LHS) in pesticide formulation.

5-Aminosalicylic Acid Loaded Chitosan-Carrageenan Hydrogel Beads with Potential Application for the Treatment of Inflammatory Bowel Disease.

The aim of our work is to prepare mucoadhesive particles with biopolymers and 5-Aminosalicylic acid (5ASA) using the ionotropic gelation technique to ensure a controlled drug release at the colon level with potential applications in the treatment of intestinal bowel disease (IBD). The preparation of particles through the crosslinking of Chitosan (CS) with sodium tripolyphosphate (TPP) using different mass ratios and the influence of the k-Carrageenan (kCG) layer were studied. UV–VIS spectrometry was employed to assess encapsulation efficiency and drug release profile of 5ASA. The particles were investigated using FT-IR spectrometry for chemical characterization and the DLS results highlighted a monodisperse particle size distribution. The morphology of the polymeric beads was investigated using micro-computer tomography (µCT) and Scanning Electron Microscopy (SEM). Particles based on Chitosan and k-Carrageenan were able to incorporate and preserve 5ASA in an acidic and alkaline medium. The 5ASA loaded polymeric particles obtained after immersion for 1 h in kCG solution exhibited the lowest release rate in pH = 1.2. Biocompatibility studies performed on all of the particles displayed a good viability for the CCD 841 CoN cells and low cytotoxicity. All of the results have shown that these new biomaterials could be a versatile platform of targeted carriers with potential applications in inflammatory bowel disease treatment.

Development and characterization of pH-sensitive chondroitin sulfate-co-poly(acrylic acid) hydrogels for controlled release of diclofenac sodium

The aim of the current study was to prepare pH-sensitive chondroitin sulfate-co-poly(acrylic acid) hydrogels (CSPAA-hydrogels) for controlled release of diclofenac sodium. CSPAA-hydrogels were prepared by free radical polymerization technique where chondroitin sulfate (CS) was used as polymer; ethylene glycol dimethylacrylate (EGDMA) and acrylic acid (AA) were used as cross-linker and monomer. Various structural features of hydrogels were evaluated by FTIR, XRD, TGA, DSC, and SEM, which confirmed the synthesis and stability of developed structures. FTIR studies confirmed the successful grafting of acrylic acid on the backbone of chondroitin sulfate. XRD results showed that the high intensity crystalline peaks of drug were reduced by developed hydrogel, thus no interaction of drug and hydrogel contents was observed. Thermal analysis revealed that the developed hydrogel network was more stable thermally than its basic ingredients (chondroitin sulfate). Sporous structure of CSPAA hydrogels was confirmed by SEM, corresponding to high swelling of hydrogels. Dynamic swelling indicated high swelling of hydrogels at pH 7.4 as compared to pH 1.2, as a result, high in-vitro drug release was shown at pH 7.4. Similarly, the drug release rate in pH 7.4 medium was significantly higher than that pH 1.2 medium. Kinetic modelling including zero order, first order, Higuchi and Korsmeyer–Peppas models were applied to know the release mechanism of drug from fabricated hydrogels.

PH-sensitive thiamethoxam nanoparticles based on bimodal mesoporous silica for improving insecticidal efficiency.

In this study, we synthesized pH-sensitive thiamethoxam-3-(2-aminoethylamino) propyl-bimodal mesoporous silica (P/Thi-NN-BMMs) nanoparticles (NPs). We used this bimodal mesoporous silica (BMMs) mesoporous material as a carrier based on the principle of free radical polymerization. The size of the P/Thi-NN-BMMs NPs was about 891.7 ± 4.9 nm, with a zeta potential of about −25.7 ± 2.5 mV. X-ray powder diffraction analysis, N2-sorption measurements and thermogravimetric analysis indicated that thiamethoxam (Thi) was loaded into the pores of the mesoporous structure and that the mesopore surface was coated with polyacrylic acid (PAA). The loading rate of P/Thi-NN-BMMs was about 25.2%. The controlled-release NPs had excellent anti-photolysis performance and storage stability. The NPs showed significant pH sensitivity, and the Thi release rate in pH 10.0 phosphate buffer was higher than those in pH 7.4 and pH 3.0 phosphate buffers. We described the sustained-release curves according to the Weibull model. The relative toxicity of P/Thi-NN-BMMs against peach aphid was 1.44 times that of commercial Thi. This provides a promising instrument for effective insect control and environment protection.

Preparation of chitosan functionalized end‐capped Ag‐NPs and composited with Fe3O4‐NPs: Controlled release to pH‐responsive delivery of progesterone and antibacterial activity against pseudomonas aeruginosa (PAO‐1)

In this work, functionalized chitosan end‐capped Ag nanoparticles (NPs) and composited with Fe3O4‐NPs was prepared as pH‐responsive controlled release carrier for gastric‐specific drug delivery. The structure of prepared material was characterized by FE‐SEM, XRD, EDS and FT‐IR analysis. The loading behavior of the progesterone onto this novel material was studied in aqueous medium at 25°C and their release was followed spectrophotometrically at 37°C in seven different buffer solutions (pH 1.2, 2.2, 3.2, 4.2, 5.2, 6.2 and 7.2) to simulate intestine and gastric media which experimental results reveal more release rate in pH 1.2 (gastric medium) with respect to other buffers. This observation is attributed to dependency of the CS‐IMBDO‐Ag‐Fe3O4‐NPs and progesterone structure with buffer pH that candidate this new material as prospective pH‐sensitive carrier for gastric‐targeted drug delivery. On the other hand, the antibacterial properties of this material against gram‐negative bacterium pseudomonas aeruginosa (PAO‐1) in agar plates was studied and accordingly based on broth micro dilution the minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) with respect to standard CLSI in different concentrations of CS‐IMBDO‐Ag‐Fe3O4‐NPs was calculated. The results reveal that MIC and MBC values are 50 and 1250 μg/mL, respectively. In addition, extracts of Portulaca oleracea leaves was prepared and its antibacterial activity in single and binary system with CS‐IMBDO‐Ag‐Fe3O4‐NPs as synergies effect against PAO‐1 was tested and results shown that these materials have significant synergistic effect for each other.

Carboxymethyl cellulose/graphene oxide bio-nanocomposite hydrogel beads as anticancer drug carrier agent

Biodegradable carboxymethyl cellulose/graphene oxide (CMC/GO) nanocomposite hydrogel beads as a drug delivery system were prepared via physically crosslinking with FeCl3·6H2O for controlled release of anticancer drug doxorubicin (DOX). The π-π stacking interaction between DOX and GO resulted in higher loading capacity and controlled release of the DOX loaded from CMC/GO nanocomposites hydrogel. The release profile of DOX from hydrogel beads at pH 6.8 and 7.4 indicated it’s strongly pH dependence. Interaction between GO and DOX with H-bonding could be unstable under acidic conditions which resulted in faster drug release rate in pH 6.8. The formation of GO nanoparticles in the hydrogels was confirmed using X-ray diffraction (XRD), and the chemical structure and morphology of the prepared CMC/GO nanocomposite hydrogel beads were characterized using Fourier transform infrared spectroscopy (FT-IR), SEM and Transmission electron microscopy (TEM). In addition, swelling behavior of nanocomposite hydrogels was investigated in PBS solution.

Preparation of targeting nanoparticles loaded with fluorouracil and its uptake test by SGC-7901 gastric carcinoma cells

Objective:To prepare fluorouracil nanoparticles and evaluate its drug release properties in vitro and its uptake effect by SGC-7901 gastric carcinoma cells.Methods:The fluorouracil nanoparticles were prepared by emulsification-solvent evaporation method,by using polyethylene glycol monomethyl ether-polylactic glycolic acid-polylysine-(valine-arginine-glycineaspartic acid-glutamic acid)cyclic peptides as a carrier.The preparation was optimized by orthogonal design with particle diameter and encapsulation efficiency as evaluation indexes.The uptake efficiency of the nanoparticles by SGC-7901 gastric carcinoma cells was investigated.Results:The nanoparticles prepared by optimal technology were spherical with a diameter of(172.9± 2.3)nm and encapsulation efficiency of(75.31±1.91)%.The in vitro cumulative drug release rate in pH 7.4phosphate buffer during 192h was(58.63±2.47)%.The nanoparticles could effectively be taken by SGC-7901 gastric carcinoma cells.Conclusion:The targeting nanoparticles loaded with fluorouracil possess the properties of high encapsulation efficiency and particles of small diameter.They could enhance the uptake of fluorouracil by SGC-7901 gastric carcinoma cells.

Study on the preparation of genipin crosslinked chitosan microspheres of resveratrol and in vitro release

Resveratrol has attracted considerable public and scientific attention because of its beneficial effects on human health. In this study, resveratrol was encapsulated into chitosan microspheres for improving the stability and evaluating the ability of controlled release. Chitosan microspheres were prepared by using an emulsification-crosslinking method, and specifically, a natural extraction genipin was used as crosslinking agent for pursuit better physiological compatibility. Factors which influence on the shape and dispersity of microspheres were investigated to optimize the preparing process of resveratrol loaded genipin-chitosanmicrospheres. The optimum condition was obtained and the prepared resveratrol loaded genipin-chitosanmicrospheres were characterized by many technical instruments. Entrapment efficiency of resveratrol in genipin-chitosanmicrospheres is up to 87.6 %, and loading capacity is 7.9 %. The in vitro release rate in pH 3.6 buffer solution reached to 33.8 % within 72 h, but was lower in pH 7.4 buffer solution.

Novel PLGGE graft polymeric micelles for doxorubicin delivery

Novel poly{(lactic acid)-co-[(glycolic acid)-alt-(L-glutamic acid)]}-g-monomethyl poly(ethylene glycol) (PLGGE) micelles were prepared and used as carriers for anti-tumor drug delivery. Three PEGylated PLGG copolymers (PLGGE2000, PLGGE1100 and PLGGE500) were characterized by XRD, TG and DSC. The critical micelle concentrations (CMCs) of the amphiphilic copolymers were 1.04, 0.55 and 0.13 μg/mL, respectively. The TEM, AFM and DLS measurements revealed that the micelles were homogeneous spherical nanoparticles with the diameters ranged from 50 to 150 nm when THF was used as solvent in the preparation of the micelles. Interestingly, extended cylindrical micelles were obtained using CHCl3 as solvent. The micelles could trap doxorubicin (DOX) in the core with the highest drug loading content up to 23.7%. The mean diameter of drug loaded micelles was much bigger than that of blank micelles. The in vitro drug release of the micelles was diffusion-controlled release within the first 36 h and initial burst release was not obvious. However, after 36 h, the release rate in pH 5.0 was faster than that in pH 7.4 due to the degradation. The PLGGE micelles were nontoxic to both NIH 3T3 fibroblasts and HepG2 cells. The in vitro cytotoxicity against HepG2 cells demonstrated that the drug loaded micelles exhibited high inhibition activity to cancer cells. CLSM observation of HepG2 cells showed that DOX released from the micelles could be delivered into cell cytoplasm and cell nuclei. PLGGE micelles are potential promising carriers for anti-tumor drug delivery.

Polymer excipients enable sustained drug release in low pH from mechanically strong inorganic geopolymers

Improving acid resistance, while maintaining the excellent mechanical stability is crucial in the development of a sustained and safe oral geopolymer dosage form for highly potent opioids. In the present work, commercially available Methacrylic acid–ethyl acrylate copolymer, Polyethylene-glycol (PEG) and Alginate polymer excipients were included in dissolved or powder form in geopolymer pellets to improve the release properties of Zolpidem, herein acting as a model drug for the highly potent opioid Fentanyl. Scanning electron microscopy, compression strength tests and drug release experiments, in gastric pH 1 and intestinal pH 6.8 conditions, were performed. The polymer excipients, with an exception for PEG, reduced the drug release rate in pH 1 due to their ability to keep the pellets in shape, in combination with the introduction of an insoluble excipient, and thereby maintain a barrier towards drug diffusion and release. Neither geopolymer compression strength nor the release in pH 6.8 was considerably impaired by the incorporation of the polymer excipients. The geopolymer/polymer composites combine high mechanical strength and good release properties under both gastric and intestinal pH conditions, and are therefore promising oral dosage forms for sustained release of highly potent opioids.

Micellar carrier based on methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) block copolymers bearing ketone groups on the polyester block for doxorubicin delivery

Block copolymers of Methoxy poly(ethylene glycol)-block-poly(epsilon-caprolactone) bearing ketone groups (MPEG-b-P(CL-co-OPD)) are synthesized and evaluated for its potential to form micelles containing doxorubicin (DOX), a representative anticancer drug, by using an in vitro method based on membrane dialysis to emulate drug release in vivo. The (1)H NMR spectra of the prepared block copolymers in D(2)O solution exhibit peaks due to the P(OPD-co-CL) in decreased intensity, indicates that the polymers form micelle particles containing the hydrophilic segments in their external parts. The CMC of the copolymer decrease with an increase in the content of ketone groups in the hydrophobic chain. Drug-free and drug-loaded solutions of structurally related copolymers indicate the polymeric aggregation into micellar-type constructs. The size of the drug-loaded micelles is found to be larger than corresponding drug-free micelles. The release rate of MPEG-b-PCL micelles is faster than MPEG-b-P(OPD-co-CL) micelles in pH 7.4 buffered solution and they have a similar release rate in pH 5.0 buffered solution. This study, therefore, confirms the potential of a novel functional block copolymers, Methoxy poly(ethylene glycol)-block-poly(epsilon-caprolactone) bearing ketone Groups, for the formation of polymeric micelles for drug delivery.

Release characteristics and in vitro–in vivo correlation of pulsatile pattern for a pulsatile drug delivery system activated by membrane rupture via osmotic pressure and swelling

This study attempted to characterize the influence of core and coating formulations on the release profiles to establish in vitro/in vivo correlations of pulsatile pattern for a pulsatile drug delivery system activated by membrane rupture based on three core tablet formulations (A-core: HPMC 50+4000 cps, B-core: E10M, and C-core: K100M) coated with various thicknesses of a semipermeable ethylcellulose membrane plasticized with HPMC 606 (Pharmacoat 606) at different ratios with/without adding various amounts of water to dissolve it in the coating solution. Drug release behaviors were investigated using apparatus II in four media of pH 1.2 solution, pH 6.8 buffer, deionized water, and a NaCl solution rotated at 75, 100, and 150 rpm. Pilot studies of the in vivo pharmacokinetics were conducted as well for comparison with the in vitro results. Results demonstrated that drug release from the three kinds of core tablets in deionized water increased with an increasing stirring rate, and decreased with an increasing viscosity grade of HPMC used in the core formulations. A significant promotion of drug release from core tablets was observed for the three levels of NaCl media in comparison with that in deionized water. Results further demonstrated that a slightly slower release rate in pH 1.2 solution and a faster release rate in pH 6.8 buffer than that in deionized water were observed for the A-core and B-core tablets, with the former being slower than the latter. However, similar release rates in the three kinds of media were observed for C-core tablets, but they were slower than those for the A- and B-core tablets. Dissolution of coated tablets showed that the controlling membrane was ruptured by osmotic pressure and swelling which activated drug release with a lag time. The lag time was not influenced by the pH value of the release medium or by the rotation speeds. The lag time increased with a higher coating level, but decreased with the addition of the hydrophilic plasticizer, Pharmacoat 606, and of the water amount in the coating solution. The lag time also increased with a higher concentration of NaCl in the medium. The release rate after the lag time was determined by the extent of retardation of gelation of HPMC in the core tablet based on the ionic strength of the medium. Results of the three pilot crossover studies for the exemplified pulsatile systems indicated that the lag time for the in vivo plasma profile was well correlated with that determined from the in vitro release profile in pH 1.2 solution and the in vivo release rate was better reflected by that performed in pH 6.8 buffer.

Effect of CaF2 Content on Rate of Fluoride Release from Filled Resins

Information on the time-dependent release of fluoride from filled resins containing fluoride particles as a function of particle content and solution pH is limited. This study characterized the fluoride ion release from filled resins containing CaF2 particles as a function of filler content and pH. Urethane dimethacrylate and triethylene glycol dimethacrylate resins were used to make filled-resin disks containing 9.09, 23.08, or 33.33 mass% CaF2 filler. Fluoride ion release for the 9.09 mass% concentration was independent of pH. Increasing the filler content from 9.09 to 33.33 mass% increased the fluoride release rate in pH 4.0 buffer solution, because of greater surface degradation. Fluoride ion release from disks stored in pH 6.0 buffer solutions occurred mainly by diffusion from disk surfaces, while fluoride release from disks in pH 4.0 buffers was controlled by diffusion from disk surfaces and degeneration of the resin matrix, which exposed more CaF2 particle surface area.

Preparation and Evaluation of Beads Made of Different Calcium Alginate Compositions for Oral Sustained Release of Tiaramide

ABSTRACTThis study was undertaken to develop a sustained-release formulation of tiaramide (TAM), a nonsteroidal anti-inflammatory drug with a short half-life, using alginate of different chemical compositions. Alginate gel beads containing TAM were prepared using a gelation of alginate with calcium cations. Bead performance was evaluated in vitro for different dissolution media and beads were also subjected to coating. TAM release was dependent both on its solubility in dissolution medium and the guluronate residue content of the alginate used. The release rate was in the following order: in pH 1.2 < pH 6.8 < water. The fast release rate in pH 1.2 is the result of the high solubility of TAM in acidic medium. Beads based on alginate rich in guluronate residue had the lowest release rate, which can be attributed to the compact structure formed by guluronate residues through cooperative interaction with calcium ions. Alginate beads were administered to beagle dogs, and pharmacokinetic parameters (mean residence time [MRT], tmax, Cmax, and A UC) were calculated. In vivo results were in good agreement with in vitro dissolution characteristics. Beads with high guluronate content gave the best controlled results. In addition, coated beads showed a more satisfactory sustained-release pattern. Calcium alginate appears to be a potential carrier for controlling drug release rate, even for water-soluble drugs such as TAM.