Fickian Mechanism Research Articles

Synthesis and physicochemical properties of pH-sensitive hydrogel based on carboxymethyl chitosan/2-hydroxyethyl acrylate for transdermal delivery of nobiletin

In this study, CmCHT-g-pHEA hydrogels were prepared by grafting 2-hydroxyethyl acrylate (2-HEA) onto carboxymethyl chitosan (CmCHT) using N, N′-methylenebis(acrylamide) (MBA) as a crosslinker. The physicochemical properties and in vitro drug release behavior of the CmCHT-g-pHEA hydrogels were studied. The hydrogels were synthesized by radical polymerization, and confirmed by FT-IR, 13C NMR, and 1H NMR analysis. The 3D network structure was characterized by scanning electron microscopy observation, and the water binding capacity of the hydrogels was measured by thermogravimetric analysis. The swelling ratio of the hydrogel was evaluated in pH buffer and increased at high pH. In addition, we confirmed that the gel network was stable using rheological analysis. The hydrogel with optimal viscoelasticity and gel fraction was selected, and nobiletin, which is known to be an effective acne treatment, was used as a model drug to test the drug-carrying properties of the gel. The mechanism of the release nobiletin from the CmCHT-g-pHEA hydrogel was verified to be a Fickian diffusion-based mechanism. In in vitro skin permeation experiments, the CmCHT-g-pHEA hydrogel improved the transdermal delivery of nobiletin. In conclusion, the newly synthesized CmCHT-g-pHEA hydrogel has potential applications as a pH-sensitive transdermal drug delivery system.

Assessment of the delivery of citronella oil from microcapsules supported on wool fabrics

Essential oils are complex, volatile liquid mixtures that can be extracted from various parts of plants. Their main characteristics are strong fragrance and biological properties. Studying the characteristics of oils along with the possibility of an interaction with textiles creates new possible uses of this material. However, when oil is applied to a textile substrate, it is necessary to develop an oil release model, while most of the works only explore the application procedure and the fixed oil durability against washes. Thus, this work reports the mechanism and kinetics of controlled release of microencapsulated citronella oil from wool. The microencapsulation was done by complex coacervation with gelatin and gum Arabic biopolymers as shell materials. Optical microscopy, scanning electron microscopy and Fourier-transform infrared spectroscopy were used to confirm the encapsulation. The microcapsules were then supported by foulard in wool, fixed on fabrics and evaluated by attenuated total reflection Fourier-transform infrared spectroscopy. The controlled release of citronella from the microcapsules deposited on the fabric was studied in vitro. The microcapsules formed had a multi-core structure, and when applied to wool they showed diffusion by a Fickian mechanism in the first release stage and on the second stage changed to non-Fickian kinetics. The controlled release indicates that the textile structure influences the release model due to an interaction between fabric and water.

A novel bilayer drug-loaded wound dressing of PVDF and PHB/Chitosan nanofibers applicable for post-surgical ulcers

A novel bilayer nanofibrous wound dressing, with enhanced mechanical properties is successfully fabricated. This membrane, consisted of polyvinylidenefluoride (PVDF) nanofibers for providing tensile strength and polyhydroxybutyrate/chitosan (PHB/CTS) nanofibers loaded with gentamicin with ability of controlled drug delivery, is a great choice for post-surgical ulcers. Mechanical properties showed dramatically improvement of tensile strength by addition of PVDF layer. Gentamycin release represented both an immediate and a sustained release of about 24 h and 1 week, respectively and release increment with increase of CTS ratio. Results also revealed that drug release in structures follow first order kinetic and Fickian release mechanism.

Microfluidics to determine the diffusive mass transfer of a low viscosity solvent into a high viscosity hydrocarbon

In this work, a microfluidic platform along with X-ray computerized tomography were employed to analyze diffusive mass transfer of a low viscosity solvent (hexane) into a high viscosity hydrocarbon (bitumen). T-shaped microfluidic channels were fabricated to measure the diffusion coefficient in significantly shorter times and lower sample volume compared with traditional methods. Semitransparent nature of bitumen facilitates the application of light transmission imaging during the time and relating intensities to solvent concentration. Diffusion mass transfer was studied with respect to Fickian and Single-File mass transfer mechanisms and corresponding equation was applied to calculate both constant and concentration dependent diffusion coefficients. The accuracy of Fickian mass transfer mechanism was confirmed with calculating values of fitting parameter (i.e. nw) in addition to superimposition of data for both techniques. The optimum values of constant diffusion coefficient for T-shaped microchannel and X-ray technique were 2 × 10−10 and 1.8 × 10−10 m2·s−1, respectively. Concentration dependent diffusion coefficients ranged from 1 × 10−12 to 3.6 × 10−10 m2·s−1 for the experiments that reveal constant mutual diffusion coefficient assumption can result in significantly high errors particularly at low and high solvent mass fractions.

Formulation and investigation of crushed puffed rice-chitosan-HPMC based polymeric blends as carrier for sustained stomach specific drug delivery of piroxicam using 3(2) Taguchi mathematical design studies

In the present experimental investigation an attempt has been made to assess the utility of Crushed Puffed Rice (CPR)-High Molecular Weight Chitosan (HMWCH)-Hydroxypropyl Methylcellulose K15M (HPMC K15M) as a polymeric carrier for the sustained stomach delivery of Piroxicam (PRX). A total of nine formulations were prepared by using 3 (2) Taguchi factorial design, physically blending drug and polymer(s) followed by encapsulation into hard gelatin capsules size 1. The prepared capsules were evaluated for various performance such as weight variation, drug contents, in vitro buoyancy and drug release in 0.1 M HCl. The effect of drug loading on in vitro performance of the formulations was also determined. Crushed puffed rice (CPR) remained buoyant for up to average time span of 06 hr as an unwetted irregular mass in 0.1 M HCl. However, when combined with HMWCH or HPMC K15M or HPMC K15M + HMWCH a low -density cylindrical raft type hydrogel was formed which remained buoyant for up to 12 hr and released up to 99% drug in a sustained manner from 8 to 12 hr following zero order release kinetics. It was also observed that drug release from drug + CPR matrices followed Fickian mechanism. Combination of CPR + HMWCH or HMWCH + HPMC K15M also follows Fickian mechanism. Obtained data from the research work suggests that CPR in combination with HMWCH or HPMC K15M or HPMC has sufficient potential to be used as a carrier for stomach specific delivery of gastric irritant drug like PRX.Soni et al., International Current Pharmaceutical Journal, April 2018, 6(11): 61-80http://www.icpjonline.com/documents/Vol6Issue11/01.pdf

Hyaluronic acid-modified betamethasone encapsulated polymeric nanoparticles: fabrication, characterisation, in vitro release kinetics, and dermal targeting.

Atopic dermatitis (AD) is a chronically relapsing eczematous skin disease characterised by frequent episodes of rashes, severe flares, and inflammation. Till date, there is no absolute therapy for the treatment of AD; however, topical corticosteroids (TCs) are the majorly prescribed class of drugs for the management of AD in both adults and children. Though, topical route is most preferable; however, limited penetration of therapeutics across the startum cornum (SC) is one of the major challenges for scientists. Therefore, the present study was attempted to fabricate a moderate-potency TC, betamethasone valerate (BMV), in the form of chitosan nanoparticles (CS-NPs) for optimum dermal targeting and improved penetration across the SC. To further improve the targeting efficiency of BMV and to potentiate its therapeutic efficacy, the fabricated BMV-CS-NPs were coated with hyaluronic acid (HA). The prepared NPs were characterised for particle size, zeta potential, polydispersity index (PDI), entrapment efficiency, loading capacity, crystallinity, thermal behaviour, morphology, in vitro release kinetics, drug permeation across the SC, and percentage of drug retained into various skin layers. Results showed that optimised HA-BMV-CS-NPs exhibited optimum physicochemical characteristics including finest particle size (< 300 ± 28nm), higher zeta potential (+ 58 ± 8mV), and high entrapment efficiency (86 ± 5.6%) and loading capacity (34 ± 7.2%). The in vitro release study revealed that HA-BMV-CS-NPs displayed Fickian diffusion-type mechanism of release in simulated skin surface (pH 5.5). Drug permeation efficiency of BMV was comparatively higher in case of BMV-CS-NPs; however, the amount of drug retained into the epidermis and the dermis was comparatively higher in case of HA-BMV-CS-NPs, compared to BMV-CS-NPs. Conclusively, we anticipate that HA-BMV-CS-NPs could be a promising nanodelivery system for efficient dermal targeting of BMV and improved anti-AD efficacy.

Synthesis, swelling and adsorption studies of a pH-responsive sodium alginate–poly(acrylic acid) superabsorbent hydrogel

Polyacrylic acid grafted sodium alginate (SA-cl-PAA)-based hydrogel was synthesized by an aqueous polymerisation method. An acrylic acid (AA) monomer was grafted onto sodium alginate (SA) using N,N′-methylene-bisacrylamide (MBA) and potassium persulfate (KPS) as a crosslinker–initiator system. The impact of various parameters such as reaction time, the amount of solvent, pH, crosslinker amount, initiator concentration and monomer concentration on the swelling behavior of the synthesized hydrogel was investigated. We obtained a hydrogel with swelling percentage 41,298% which is quite high. Swelling studies were carried out under acidic (pH 2 buffer) and basic (pH 10 buffer) conditions and evaluated kinetically. The results revealed that the swelling process follows second order kinetics, and the water transport inside the hydrogel supports a Fickian mechanism. The swelling results also indicate that the swelling properties of the synthesized hydrogel showed an on- and off-switchable behavior under basic and acidic conditions, respectively. The synthesized hydrogel was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The hydrogel was used in the victoria blue R (VB) and rhodamine 6G (RG6) dye adsorption from wastewater. It was found that hydrogel adsorbed 95.8 and 99% of VB and RG6 (132 ppm), respectively, within 77 min. Adsorption of victoria blue is due to electrostatic interaction only, and removal of rhodamine 6G is explained on the basis of electrostatic interaction and hydrogen bonding.

E-beam radiation synthesis of xanthan-gum/carboxymethylcellulose superabsorbent hydrogels with incorporated graphene oxide

ABSTRACTIn this study the electron beam (e-beam) radiation synthesis in “paste-like condition” and characterization of the network structure of acrylic acid (AA) sodium salt/xanthan gum (XG)/carboxymethylcellulose (CMC) superabsorbent hydrogels incorporating graphene oxide (GO) was investigated. The effects of the AA concentration on gel fraction, sol-gel analysis, swelling degree and network parameters, as well as the relationship between these parameters and radiation dose was also established.Gel fraction exceeds 90%, and the p0/q0 ratio shows a moderate degradation process. The swelling kinetic data were used to determine, first the swelling degree, second the diffusion characteristics, and third the average molecular weight between crosslinks (Mc), as well as. The diffusion data revealed a Fickian mechanism transport, for each hydrogel compositions. The network parameters (Mc and ξ) increased with absorbed dose, while cross-linking density and the radiation-chemical yields were decreased.

A NOVEL APPROACH OF LOCUST BEAN GUM MICROSPHERES FOR COLONIC DELIVERY OF MESALAMINE

Objective: The objective of the present study was to formulate site-specific drug delivery of mesalamine using Locust bean gum.Methods: The core microspheres were prepared by ionic gelation method using CaCl2 solution and cross-linked with glutaraldehyde and were further coated with pH-sensitive polymer eudragit S-100(1.5-4.5 ml) to retard the drug release in the upper gastrointestinal environment (Stomach and small intestine). Microspheres were characterized by ftir spectroscopy, differential scanning calorimetry and evaluated by scanning electron microscopy (SEM), particle size analysis, entrapment efficiency and in vitro drug release studies in different simulated gastric fluids. Stability studies were carried out for one month at 40±2 °C/75±5% RH.Results: The SEM images revealed the surface morphology was rough and smooth for core and coated microspheres, respectively. The optimized batch (ILBG6) of core microspheres(for 7hr), coated microspheres and coated microspheres in presence of rat caecal contents (8%w/v) for 24hr exhibited 98.44±2.48, 73.58±3.49 % and 98.28±4.42 drug release, respectively. The drug release from all locust bean gum microsphere formulations followed higuchi kinetics. Moreover, drug release from Eudragit S-100 coated microspheres followed the korsmeyer-peppas equation with an fickian kinetics mechanism. Finally, stability studies suggested the change in entrapment efficiency and in vitro drug release of microspheres was minimal, indicating good stability of the formulation.Conclusion: The microspheres formed using natural polysaccharide locust beangum by ionic gelation method are capable of colon targeting the anti-inflammatory drug, mesalamine for the treatment of ulcerative colitis.

Fabrication and Evaluations of Dual Crosslinked Mesalamine containing Pectin-Chitosan gel micro beads for controlled and targeted colon delivery

Objectives: The aim of the present work was to prepare and characterize mesalamine loaded microbeads (MLM) consisting of optimized ratios of chitosan and pectin polysaccharides using ionic gelation technique for management of inflammatory bowel disease. Methodology: Mesalamine loaded microbeads were prepared using ionotropic gelation method that was double cross linked with calcium chloride (3-6%, w/v) and sodium sulphate (2-4%, w/v) solutions. The formulation was optimized with the help of two levels and three factors factorial design method. The optimization parameters selected for formulation variables were viz., pectin-chitosan ratio, calcium chloride-sodium sulphate ratio and curing time. The prepared formulations were further characterized on the basis of particle size, shape, swelling index, entrapment efficiency, and percentage yield and in vitro drug release studies. The in vitro release studies using rat caecal content (2 and 4 % w/v) was also performed to simulate the human colonic condition. Results: The mean particle size, entrapment efficiency and percentage yield of MLM were ranged from 875.45 to 975.45 µm, 72.2 to 86.7% and 93.6 to 97.9% respectively. The swelling index of MLM formulations revealed lesser into acidic medium, while augmented swellings were found to be at pH 6.8 and 7.2 respectively. The swelling degree was found to be 7.34 to 13.88% into SIF at pH 6.8 whereas, intensely swelled was 16.24 to 46.02% into SCF at pH 7.2 during 8 h studies. In vitro drug release profile of MLM exhibited that only 1.28 to 4.42 drug was released at simulated gastric fluid (SGF, pH 1.2, 2 h), however optimum drug released was found into simulated intestinal fluid (SIF, pH 6.8, 3 h) i.e. 5.33 to 31.33% and into simulated colonic fluid (SCF, pH 7.2, 18 h) i.e. 32.13 to 87.12% correspondingly. Scanning electron microscopy (SEM) revealed that the microbeads were consisting of semispherical and wrinkled rough surfaces. Further, the rat caecal contents (2 and 4% w/v) release studies confirmed for complete polymeric degradation by colonic enzymes. The release kinetics and mathematical modeling studies carried out for optimized formulation shown that the optimized formulations were of non fickian mechanism (n=0.49 to 0.74) type governed by both diffusion and erosion controlled following Higuchi and Korsemeyer peppas model fittings. Conclusion: It can be concluded from the study that the optimized MLM formulations may be effective for colon targeting and treating inflammatory bowel disease.

Mesalamine-loaded mucoadhesive microsphere for colon drug delivery system: Effect of process variables and in vitro characterization

Objective: The main objective of this study is to formulate mucoadhesive microspheres for colon drug delivery with sodium alginate (ALG) core enriched with drug. Methods: The core microspheres of ALG were prepared by modified emulsification method followed by cross-linking with different concentration of CaCl2 at different stirring speed with constant drug-to-polymer ratio (1:3). The core microspheres were further coated with Eudragit S-100 using the solvent evaporation technique. Results: The microspheres (core and coated) were characterized by shape, size, surface morphology, size distribution, entrapment efficiency, and in vitro drug release studies. In vitro drug release showed that the optimized batch of core microsphere and coated microspheres exhibited 99.53% ± 0.39% and 89.22% ± 0.26%, respectively. The drug release from all formulations of mesalamine microsphere followed Higuchian Kinetics. Moreover, drug release from core and Eudragit S-100-coated microspheres followed Korsmeyer–Peppas equation with anomalous and Fickian kinetics mechanism, respectively. Stability study suggests that the degradation rate constant of mesalamine from Eudragit S-100-coated microsphere was found to be minimum 2 years shelf life of the formulation. On the basis of scanning electron microscopy, the core microspheres were formed slightly irregular in shape due to surface-attached crystals of the drug and coated mesalamine microspheres showed smooth surface and a smaller number of pores due to coating. Conclusions: It can be concluded that the appropriate combination of a pH-dependent polymer (Eudragit S-100) with a pH-independent polymer sodium ALG) was suitably adequately sustained the drug release from mesalamine microspheres.

Kinetika Slow Release Pupuk Urea Berlapis Chitosan Termodifikasi

&lt;p&gt;During this time, the use of urea is not efficient, because about 40-70% of nitrogen in the fertilizer is not absorbed by plants. In order to increase the effectivity of nitrogen release in urea fertilizer, it needs to be coated with modified chitosan as slow releasing agent to form a hydrogel material by forming a cross linking with glutaraldehyde cross-linker.The aims of this research is to study the mechanism and the appropriate kinetic model of nitrogen release in slow releasing fertilizer of modified chitosan. This research was conducted by analyzing the ability of bio-hydrogel by calculating the percentage of swelling ratio and water retention of hydrogel and the nitrogen release in slow releasing fertilizer both in the soil and water. The experiments were conducted by varying the amount of urea used which 30 gram, 40 gram, 50 gram, 60 gram and 70 gram of urea fertilizer. The The release profile is then plotted on several models of diffusion kinetic such as zero order, first order, higuchi and korsmeyer peppas. The appropriate model of diffusion kinetic is chosen by the largest correction factor (R2).The results showed that nitrogen release of the slow releasing fertilizer in the soil with 50% urea content and the water followed korsmeyer peppas model with fickian mechanism. Nitrogen release in the soil with urea content of 30%, 40%, 60%, and 70% followed the korsmeyer peppas model with nonfickian mechanism.&lt;/p&gt;

Poly (methacrylic acid-co-acrylic acid)-grafted polyvinylpyrrolidone coated Magnetic nanoparticles as a pH-responsive magnetic Nano-carrier for controlled delivery of antibiotics

Objective(s): Pharmaceutical industries are leading to improved medications that can target diseases more effectively and precisely. Researchers have intended to reformulate drugs so that they may be more safely used in human body. The more targeted a drug is, the lower its chance of triggering drug resistance, a cautionary concern surrounding the use of broad-spectrum antibiotics. The aim of this paper is to introduce efficient drug delivery vehicles which can perform both targeted and controlled antibiotic release by synthesis of magnetic pH-responsive polymer. Materials and Methods: Iron oxide nanoparticles were synthesized by chemical co-precipitation technique and primary coated with 3-trimethoxysilylpropylamine (APTS). APTS coated MNPs was used in the reaction medium for synthesis of a pH-responsive poly (MAA-co-AAc)-grafted PVP. The prepared vehicle was characterized by TEM, XRD, FT-IR, TGA, DSC and elemental analysis. Drug loading, release, kinetics and mechanism of the system were evaluated.Results: The results for drug release showed that the release of antibiotics in pH 5.5 and 7.2 could be effectively sustained, while about 92 % of the drugs were released at pH 1.2. Considerations demonstrate the tendency of drug release by Fickian mechanism and diffusion controlled release.Conclusion: The results indicate that the prepared magnetic nano-carrier could be suitable for site-specific antibiotic delivery through oral administration.

Development and Evaluation of Controlled Release Formulation of Zidovudine Based on Microporous Osmotic Tablet Technology Using Fructose as Osmogen

The present work was aimed to develop and evaluate controlled porosity osmotic pump (CPOP) tablets of an anti HIV drug zidovudine to provide a uniform concentration of drug at absorption site. The formulations were prepared by wet granulation method using drug, various excipients, controlled release polymer hydroxylpropylmethyl cellulose(HPMCE5M LV) and osmogen (Fructose).The CPOP tablets consist of an osmotic core coated with a micro porous membrane made up of cellulose acetate(CA) which is incorporated with sorbitol as porogen. Prior to compression the prepared granules were evaluated for pre compression parameters such as angle of repose, bulk density, tapped density, Carr’s index and Hausner’s ratio. After compression the prepared granules were evaluated for thickness, coat thickness, hardness, weight variation, friability, drug content, diameter, in vitro drug release study and scanning electron microscopy (SEM) study. The release kinetics for different formulations were analyzed using zero order model equation, first order model equation, Higuchi model equation, Korsmeyer Peppas model equation and Hixson-Crowell equation. The optimized formulation of drug release was independent of pH, agitation intensity, but dependent on the osmotic pressure of the release media. Based on the in vitro dissolution profile optimized formulation ZF4 exhibited Fickian transport mechanism with a drug release of 97.83% in 16 hrs. FTIR and DSC study revealed that there was no interaction between drug and excipients. Formulations subjected to stability testing (at 40±2oC/75±5% RH) as per ICH guidelines for three months indicated stability with no significant changes in thickness, hardness, weight variation, friability drug content and dissolution profiles.

Hydroxypropyl-β-Cyclodextrin (HBC) Multicomponent Complexation and pH independent controlled release delivery system to Improved Dissolution and oral Bioavailability of Ondansetron HCI

Abstract: The objective of this study was to develop pH independent controlled release matrix tablets of Ondansetron HCl by using Multi component Complexation technique, Methocel K100M as release retarding materials and HP β-cyclodextrin was selected as release modulators. Ondansetron is weakly basic drug and their salts shows pH-dependent solubility that may show drug release problems at higher pH of small intestine. Incorporation of weakly basic drugs, exhibiting pH dependent solubility, into oral controlled release delivery systems shows pH dependent release profiles. In the present investigation, an attempt was made to pH-solubility dependence of drug and dissolution enhancement was attained by inclusion complex of Ondansetron with HP- β-cyclodextrin at 1:1 (drug: β-CD) molar ratio and then prepared complex hydroxyl propyl methyl cellulose controlled released matrix tablets. The in vitro drug release studies were carried out in pH1.2 buffer for 2 hrs and then in pH 6.8 phosphate buffer up to 24 hrs. The formulated matrix tablet F4 (without complexation) was very slow and drug is not released completely from matrix tablets in 6.8 pH phosphate buffer. The matrix tablets prepared using HP β- cyclodextrin with PVP (F8) showed a superior dissolution rate and good dissolution profile that was comparable to without complexation of Ondansetron HCl. Dissolution results showed pH independent controlled and almost complete release behavior of Ondansetron HCl up to 24 hrs time period. The drug release mechanism of the HPMC matrix tablets was found to be quasi Fickian mechanism. These results suggested that the oral bioavailability of Ondansetron HCl was significantly improved by Multi component Complexation strategies. Key word: Ondansetron HCl, pH independent controlled drug delivery, Hydroxypropyl-β- cyclodextrin, Multi component complexes.

Preparation and evaluation of chitosan-based nanogels/gels for oral delivery of myricetin

A novel nanogel/gel based on chitosan (CS) for the oral delivery of myricetin (Myr) was developed and evaluated comprehensively. The particle size of the obtained Myr-loaded CS/β-glycerol phosphate (β-GP) nanogels was in the range of 100–300nm. The rheological tests showed that the sol-gel transition happened when the nanogels were exposed to physiological temperatures, and 3D network structures of the gelatinized nanogels (gels) were confirmed by Scanning Electron Microscopy. Myr was released from CS/β-GP nanogel/gel in acidic buffers via a Fickian mechanism, and this release was simultaneously accompanied by swelling and erosion. Moreover, the nanogel/gel exhibited no cytotoxicity by MTT assay, and the oral bioavailability of Myr in rats was improved with an accelerated absorption rate after Myr was loaded into CS/β-GP nanogel/gel. In summary, all of the above showed that CS/β-GP nanogel/gel was an excellent system for orally delivering Myr.

Floating mucoadhesive alginate beads of amoxicillin trihydrate: A facile approach for H. pylori eradication

This study investigates the design of sunflower oil entrapped floating and mucoadhesive beads of amoxicillin trihydrate using sodium alginate and hydroxypropyl methylcellulose as matrix polymers and chitosan as coating polymer to localize the antibiotic at the stomach site against Helicobacter pylori. Beads prepared by ionotropic gellation technique were evaluated for different physicochemical, in-vitro and in-vivo properties. Beads of all batches were floated for >24h with a maximum lag time of 46.3±3.2s. Scanning electron microscopy revealed that the beads were spherical in shape with few oil filled channels distributed throughout the surfaces and small pocket structures inside the matrix confirming oil entrapment. Prepared beads showed good mucoadhesiveness of 75.7±3.0% to 85.0±5.5%. The drug release profile was best fitted to Higuchi model with non fickian driven mechanism. The optimized batch showed 100% Helicobacter pylori growth inhibition in 15h in in-vitro culture. Furthermore, X-ray study in rabbit stomach confirmed the gastric retention of optimized formulation. The results exhibited that formulated beads may be preferred to localize the antibiotic in the gastric region to allow more availability of antibiotic at gastric mucus layer acting on Helicobacter pylori, thereby improving the therapeutic efficacy.

Near Critical Carbon Dioxide Sorption Induced Crystallization in PET

Near critical carbon dioxide sorption equilibria at 50°C and pressures up to 40 atms are analyzed and interpreted on the basis of the multiple sorption mechanisms possible in a glassy amorphous and semi crystalline polymer. Varying the penetrant-polymer testing temperature and external pressure it is possible to meet the full range of possible sorption behavior, from ideal Fickian diffusion to limiting relaxation controlled kinetics. Low sorption levels of low-pressure gases are attained through an ordinary Fickian mechanism. At higher gas pressures, however, higher penetrant sorption levels induce polymer relaxation affecting the final sorption behavior. A highly interacting solvent, as Carbon Dioxide in near critical conditions, leads to anomalous sorption ranging from relaxation controlled Fickian diffusion to limiting Case II and diffusion controlled relaxation, at high solvent uptakes (sorption from high activity vapor or from liquid phases). Generally, swelling has been observed to be accompanied by a solvent induced crystallization as detected by means of High pressure Differential Scanning Calorimeter (DSC) and Wide Angle Xray Scattering (WAXS).

Controlled release of microencapsulated citronella essential oil on cotton and polyester matrices

Microencapsulated finishes are an important element in the development of new textiles. In this context, a large area to be explored is microencapsulation of essential oils in textiles. This technique offers the possibility of developing new products with many advantages over traditional fabrics, as traditional finishing may be ineffective for reasons related to uncontrolled release of the active principle while microencapsulation aims to achieve increased duration of the finishing effect. However, many studies present only the application of microcapsules in a textile but do not report how the release of the encapsulated material occurs or the influence of the textile matrix. This paper reports the mechanism and kinetics of controlled release of microencapsulated citronella oil in cotton and polyester. The microencapsulation was done by complex coacervation with gelatin and gum Arabic as shell materials. The resulting microcapsules were analyzed by optical microscopy, scanning electron microscopy, thermogravimetric analysis, and dynamic light scattering. They were then applied in cotton and polyester and evaluated by attenuated total reflection Fourier-transform infrared spectroscopy. Finally, the controlled release of citronella from the microcapsules deposited on the fabrics was studied in vitro. It was found that the release was directly influenced by the type of fiber: the microcapsules in polyester showed diffusion by a Fickian mechanism, while a non-Fickian kinetic model fit for the modified cotton. Comprehension of such controlled release processes is fundamental for achieving and developing more durable finishing effects.

Development and Evaluation of a Novel Intranasal Spray for the Delivery of Amantadine

The aim of this study was to develop and characterize an intranasal delivery system for amantadine hydrochloride (AMT). Optimal formulations consisted of a thermosensitive polymer Pluronic® 127 and either carboxymethyl cellulose or chitosan which demonstrated gel transition at nasal cavity temperatures (34 ± 1°C). Rheologically, the loss tangent (Tan δ) confirmed a 3-stage gelation phenomena at 34 ± 1°C and non-Newtonian behavior. Storage of optimized formulation carboxymethyl cellulose and optimal formulation chitosan at 4°C for 8 weeks resulted in repeatable release profiles at 34°C when sampled, with a Fickian mechanism earlier on but moving toward anomalous transport by week 8. Polymers (Pluronic® 127, carboxymethyl cellulose, and chitosan) demonstrated no significant cellular toxicity to human nasal epithelial cells up to 4 mg/mL and up to 1 mM for AMT (IC50: 4.5 ± 0.05 mM). Optimized formulation carboxymethyl cellulose and optimal formulation chitosan demonstrated slower release across an in vitro human nasal airway model (43%-44% vs 79 ± 4.58% for AMT). Using a human nasal cast model, deposition into the olfactory regions (potential nose-to-brain) was demonstrated on nozzle insertion (5 mm), whereas tilting of the head forward (15°) resulted in greater deposition in the bulk of the nasal cavity.