Ionic Strength Effects in Aqueous Solutions of Gelatin and Sodium Dodecylsulphate

Abstract

The interaction between the anionic surfactant sodium dodecylsulphate and the polyampholyte gelatin in aqueous solution has been studied by viscosity and fluorescence. Three different gelatin molecular iveights, a polydisperse gelatin and two fractionated samples derived from it, have been examined at two ionic strengths. On addition of sodium dodecylsulphate SDS, the viscosity of a low molecular weight fractionated (o.) gelatin increases smoothly with SDS concentration, unlike the polydisperse (standard) and high molecular zveight (HMW) fractionated gelatins which show maxima. The viscosity increase at the maximum increases with gelatin molecular weight. On addition of 0.1 M salt, the viscosities of the gelatin-surfactant mixtures are lower than the equivalent no-salt cases. Fluorescence studies suggest that the SDS micelles adsorbed onto these various gelatins under two different ionic strengths are remarkably similar.     

Bioactive microspheres produced from gelatin–siloxane hybrids for bone regeneration

In this study, we produced a novel microsphere with a hybridized composition of gelatin and siloxane which is bioactive and degradable for the applications in bone regeneration fields. A solution of gelatin organic and siloxane inorganic containing calcium chloride was formulated into microspheres in an oil bath mediated by a surfactant. Following the processes of hydration, gelation and solidification, well-shaped spherical particles were produced with sizes of a few to hundreds of micrometers (68 μm on average). The obtained microspheres were highly stable in an aqueous solution due to the in situ cross-linking of the siloxane with gelatin chains, which eliminated the additional cross-linking step generally used in pure gelatin. The hybridized microspheres exhibited rapid induction of apatite-like crystals on their surface with incubation in a simulated body fluid, suggesting an excellent bone bioactivity in vitro. It is considered that the newly developed organic–inorganic microspheres may be useful for the regeneration of skeletal defects.     

Preparation of Gelatin: Phenytoin Sodium Microsphers: An IN VITRO and IN VIVO Evaluation

Abstract

In this study phenytoin sodium microspheres were formulated with biodegradable acid-treated gelatin. The microspheres were subjected to in vitro and in vivo testing. The percent drug retained in the microspheres, as well as its release from the microspheres, was tested. In vitro data revealed a decrease in percent druq retained in the microspheres with an increase in addition of glutaraldehyde to the microsphere formulations. The statistically most consistent drug release was observed from formulations containing 10 g of gelatin and 2 g of phenytoin sodium. From this formulation the slowest release was observed when 5 ml of glutaraldehyde were added to the various formulations, whereas the fastest release was observed when no glutaraldehyde was added. In vivo studies consisted of administering phenytoin sodium in microsphere form and an aqueous solution v i a various routes of administration and determining phenytoin plasma concentration vs. time profiles in female Sprague Dawley Rats. Computer fitting of the in vivo data and subsequent statistical testing enabled comparison of the effect of microsphere formation and the effect of microsphere dose on selected pharmacokinetic parameters.     

Preparation of chitosan–hyaluronate double-walled microspheres by emulsification-coacervation method

Chitosan (CHS)−hyaluronate (HA) double-walled microspheres were prepared by emulsification-coacervation method. Tripolyphosphate (TPP) acted as ion crosslinker. The effects of oil/water volume ratio, surfactant, solution pH, TPP concentration, HA concentration, and emulsification time on microspheres fabrication and morphology were examined by Zeta (ζ) potential, Scanning electron microscopy (SEM) and Fourier-transform infrared spectrometry (FT-IR). It was found that TPP concentration, solution pH, surfactant and emulsification time were crucial factors for microspheres fabrication. Spherical microspheres with smooth surface were formed when TPP concentration was 8% or higher. The optimal pH for microspheres formation ranged from 6.0 to 7.0. As for surfactant, the microspheres obtained when span80 was applied alone were shapelier compared with those obtained when both span80 and tween80 were applied. With insufficient emulsification time, vacuous microcapsules, but not compact microspheres were formed. In addition, oil/water volume ratio and HA concentration also affected the microspheres morphology, but less importantly.     

Effect of non-ionic surfactant concentration and type on the formation and stability of W/O/W multiple emulsions: Microscopic and conductometric evaluations

Abstract

W/O/W multiple emulsions with sodium salicylate as a model drug were prepared and evaluated for the effect of surfactant concentration and type on stability using microscopic and conductometric methods. Primary (W/O) emulsions were prepared with lipophilic surfactants (2-31% W/W relative to the oily phase). W/O/W emulsions were formed by mixing the primary emulsions with solutions containing 0.5 to 2% W/V hydrophilic surfactants. Optimum concentration of the lipophilic surfactant was 26% W/W. The optimum hydrophilic surfactant concentration was 1% W/V. Best stability was achieved with HLB 3.7 lipophilic and HLB 15.6 hydrophilic surfactants.     

Preparation and Evaluation of Mucin-Gelatin Mucoadhesive Microspheres for Rectal Delivery of Ceftriaxone Sodium

ABSTRACT

Soluble mucin (S-mucin) processed from the small intestines (ileal region) of freshly slaughtered pigs via homogenization, dialysis, centrifugation and lyophilization and its admixtures with type A gelatin were dispersed in an aqueous medium and used to formulate ceftriaxone sodium-loaded mucoadhesive microspheres by the emulsification cross-linking method using arachis oil as the continuous phase. The release profile of ceftriaxone sodium from the microspheres was evaluated in both simulated gastric fluid (SGF) without pepsin (pH 1.2) and simulated intestinal fluid (SIF) without pancreatin (pH 7.4). The microspheres were further evaluated as possible novel delivery system for rectal delivery of ceftriaxone sodium in rats. Release of ceftriaxone sodium from the microspheres in both release media was found to occur predominantly by diffusion following non-Fickian transport mechanism and was higher and more rapid in SIF than in SGF. The results obtained from this study may indicate that ceftriaxone sodium could be successfully delivered rectally when embedded in microspheres formulated with either type A gelatin alone or its admixtures with porcine mucin; hence providing a therapeutically viable alternative route for the delivery of this acid-labile third generation cephalosporin.     

Interaction between surfactants and gelatin in aqueous solutions

Abstract

The interaction between certain pairs of synthetic polymers and surfactants in aqueous solution has been studied widely. These systems are of inherent scientific interest and useful properties are imparted by both the polymer (rheological control, stability enhancement) and surfactant (lowering of surface tension, wetting). Here, rather than review the extensive field of synthetic polymer/surfactant systems a selective 'case study' is presented of one type of system, that of gelatin, the anionic surfactant sodium dodecylsulphate (SDS) and, ultimately, the same system in the presence of a competing (for the SDS) non-ionic surfactant. Results from a range of techniques are discussed, and their complementarity and distinctions highlighted. Extensive comparisons with other polymer/surfactant systems are made.     

Effect of a Surfactant on Absorption of AM Antibiotic from Non-Aqueous Parenteral Suspensions

Abstract

Attempts to modify the absorption of a monocyclic beta-lactam antibiotic from an oily suspension formulation were made by incorporation of the non-ionic surfactant sorbitan trioleate. Time to serum peak concentration was increased with increased level of surfactant and there anpeared to be more efficient clearance of the antibiotic from the depot with increase in level of surfactant in the formulation. The second effect may be explained in terms of the physical characteristics of the formulations whereas the alteration in time to serum peak concentrations may be due to an effect of the surfactant on transport of drug throuah tissue.     

In Vitro Dissolution Profile of Theophvlline Lorded Ethvl Cellulose Microspheres Preprred by Emulsificrtion Soluent Eurporrtion

Abstract

Theophylline was entrapped in ethyl cellulose microspheres by a water/oil/water emulsification-solvent evaporation method. Aqueous solution of drug was emulsified into a solution of ethyl cellulose in toluene, containing polyisobutylene as protective colloid, followed by emulsification of this primary emulsion into an external aqueous phase to form a water/oil/water emulsion. Microspheres was formed after solvent evaporation and precipitation of ethyl cellulose. In vitro dissolution profile and effect of polyisobutylene on it were studied.     

Studies on the Release of Theophylline from Polyvinylacetate Microspheres

Abstract

Polyvinylacetate microspheres containing theophylline were prepared by emulsification and solvent removal method. The release pattern of theophylline from the microspheres was found to be best explained by diffusion controlled process. The rates of release were found to be influenced by drug-polymer ratios, size of microspheres, concentration of surfactant used for the preparation of microspheres, and pH of the dissolution media.     

Factors influencing the erosion rate and the drug release kinetics from organogels designed as matrices for oral controlled release of a hydrophobic drug

Abstract

This article proposes solid-like systems from sunflower oil structured with a fibrillar network built by the assembly of 12-hydroxystearic acid (12-HSA), a gelator molecule for an oil phase. The resulting organogels were studied as oral controlled release formulations for a lipophilic drug, Efavirenz (EFV), dissolved in the oil. The effects of the gelator concentration on the thermal properties of the organogels were studied by Differential Scanning Calorimetry (DSC) and showed that drug incorporation did not change the sol–gel–sol transitions. The erosion and drug release kinetics from organogels under conventional (filling gelatin capsules) or multiparticulate (beads obtained by prilling) dosage forms were measured in simulated gastric and intestinal fluids. EFV release profiles were analyzed using model-dependent (curve-fitting) and independent approaches (Dissolution Efficiency DE). Korsmeyer–Peppas was the best fitting release kinetic model based on the goodness of fit, revealing a release mechanism from organogels loaded with EFV different from the simple drug diffusion release mechanism obtained from oily formulations. From organogels, EFV probably diffuses through an outer gel layer that erodes releasing oil droplets containing dissolved EFV into the aqueous medium.     

Prolonged Release Multiple Emulsion Based System Bearing Rifampicin: In Vitro Characterisation

Abstract

Multiple emulsions containing rifampicin were prepared and evaluated for in vitro characterisation. The effect of pH of internal and external aqueous phase on in vitro release profile of rifampicin from multiple emulsions were studied. The partition coefficient of rifampicin between internal aqueous phase (at variable pH) and liquid paraffin (oily phase) was estimated and its effect on the release profile was elucidated.     

Engineering of poly(ε-caprolactone) microcarriers to modulate protein encapsulation capability and release kinetic

Drug delivery applications using biodegradable polymeric microspheres are becoming an important means of delivering therapeutic agents. The aim of this work was to modulate the microporosity of poly(ε-caprolactone) (PCL) microcarriers to control protein loading capability and release profile. PCL microparticles loaded with BSA (bovine serum albumin) have been de novo synthesized with double emulsion solvent evaporation technique transferred and adapted for different polymer concentrations (1.7 and 3% w/v) and stabilizer present in the inner aqueous phase (0.05, 0.5 and 1% w/v). SEM (scanning electron microscope) and CLSM (confocal laser scanning microscope) analysis map the drug distribution in homogeneously distributed cavities inside the microspheres with dimensions that can be modulated by varying double emulsion process parameters. The inner structure of BSA-loaded microspheres is greatly affected by the surfactant concentration in the internal aqueous phase, while a slight influence of polymer concentration in the oil phase was observed. The surfactant concentration mainly determines microspheres morphology, as well as drug release kinetics, as confirmed by our in-vitro BSA release study. Moreover, the entrapped protein remained unaltered during the protein encapsulation process, retaining its bio-activity and structure, as shown through a dedicated gel chromatographic analytical method.     

Chitosan Microspheres Prepared by Emulsification and Ionotropic Gelation

Abstract

An attempt was made to prepare chitosan microspheres by an emulsion-phase separation technique but without the usual use of glutaraldehyde as a cross-linking agent. Instead, ionotropic gelation was employed in a w/o emulsion. The effect of formulation factors was examined. The results showed that microspheres so formed were spherical, free-flowing, and had smooth surfaces. The rate of addition of counterions was important. Gelation of chitosan droplets should take place before the destabilizing effect of the counterions occurred. This effect is associated with the increase in aqueous phase volume when the counterion solution is incorporated.     

Development and Characterization of Self-Microemulsifying Drug Delivery System of Tacrolimus for Intravenous Administration

Tacrolimus (FK 506), a poorly soluble immunosuppressant is currently formulated in nonaqueous vehicle containing hydrogenated castor oil derivative for intravenous administration. Hydrogenated castor oil derivatives are associated with acute anaphylactic reactions. This proposes to overcome the problems of poor aqueous solubility of the drug and the toxicity associated with currently used excipients by the development of a new parenterally acceptable formulation using self-microemulsifying drug delivery system (SMEDDS). Solubility of FK 506 in various oils, surfactants, and cosurfactants was determined to identify SMEDDS components. Phase diagrams were constructed at different ratios of surfactants: cosurfactant (K_m) to determine microemulsion existence area. Influence of oily phase content, K_m, aqueous phase composition, dilution, and incorporation of drug on mean globule size of microemulsions was studied. SMEDDSs were developed using ethyl oleate as oily phase and Solutol HS 15 as surfactant. Glycofurol was used successfully as a cosurfactant. Developed SMEDDS could solubilize 0.8% (wt/wt) FK 506 and on addition to aqueous phase could form spontaneous microemulsion with mean globule size < 30 nm. The resulting microemulsion was iso-osmotic, did not show any phase separation or drug precipitation even after 24 h, and exhibited negligible hemolytic potential to red blood cells.     

Preparation Methods of Biodegradable Microspheres on Bovine Serum Albumin Loading Efficiency and Release Profiles

The solvent evaporation and multiple phase methods for preparing poly-(d, l) lactide microspheres of bovine serum albumin (BSA) were compared. The effects of poly (vinyl alcohol) concentration and external aqueous phase temperature on the loading efficient of BSA microspheres prepared by multiple phase emulsion method were evaluated as well. The BSA loading efficient of microspheres by multiple phase emulsion method was much higher than that by solvent evaporation method. The high aqueous solubility of BSA contributes to the low loading efficieny in the solvent evaporation method, suggesting that this method is inappropriate for proteins with high water solubility. The loading efficieny of microspheres, whcih were prepared by multiple phase emulsion method, increased with PVA concentration but decreased with external aqueous phase temperature. The burst phenomenon of release profiles of microspheres was influenced by poly (vinyl alcohol) concentrations and the external aqueous phase temperature. Considering the duration sustained release, 0.5% w/v of poly (vinyl alcohol) is most appropriate among the concentrations tested for preparing BSA microspheres by multiple phase emulsion method.     

Microencapsulation of Sulfadiazine with Cellulose Acetate Pethalate

Abstract

Microencapsulation of a relatively insoluble drug sulfadiazine was carried out by allowing drops of' a suspension of the drug in an aqueous cellulose acetate phthalate solution to fall into an acetic acid hardening solution. Spherical microcapsules could readily be obtained when a surfactant polyoxyethylene 20 sorbitan monooleate was added to the suspensior. Increased drug concentration in the suspension yielded larger microcapsules with shorter disintegration times. The incorporation of viscosity agents into the suspension yielded microcapsules with altered disintegration times     

Emulsion Spray-Drying for the Preparation of Albumin-Loaded PLGA Microspheres

The purpose of this work was to study the encapsulation of bovine serum albumin (BSA) in polylactide-co-glycolide (PLGA) microspheres using an emulsion/spray-drying method. Albumin was dissolved in an aqueous phase (w) in the presence of surfactant and emulsified in an organic phase containing the polymer (o). To stabilize the emulsion, different types of surfactant (Pluronic® F68, Pluronic F127, sodium oleate, dioctylsulfosuccinate) were added to the aqueous phase. The w/o emulsion was spray-dried to obtain BSA-loaded PLGA microspheres. The effect of type of surfactant on microsphere characteristics was evaluated. The microspheres were characterized for their morphology by scanning electron microscopy (SEM) and granulometric analysis; drug content determination and in vitro dissolution tests were performed. Results showed that the emulsion/spray-drying method is suitable for obtaining small microparticles (2-5 μm) characterized by high drug payloads (70%-80% encapsulation efficiency). The type of surfactant affects the microsphere shape and BSA release behavior.     

Adsorption of Gelatin at Solid-liquid Interfaces

Abstract

The adsorption of acid processed gelatin on to silica has been studied from the aqueous solution of gelatin at room temperature (25 °C). Various adsorption and kinetic parameters have been evaluated, such as the adsorption coefficient, rate constants for the adsorption and desorption, and diffusion constants and the effects of different factors on the extent of adsorption have been studied such as the pH of the solution, presence of inorganic salts and solvents, and temperature of the reaction medium.