The preparation and characterisation of drug-loaded alginate and chitosan sponges

Sponges composed of sodium alginate and chitosan were prepared via a freeze drying process in order to assess the utility of mixed sponges as potential wound dressings or matrices for tissue engineering. Sponge preparation involved dissolving both polymers (either individually or mixed) in 1% acetic acid and freeze-drying the corresponding solutions. The mechanical properties of the sponges were assessed using texture analysis and the microstructure examined using scanning electron microscopy. The dissolution of a model drug (paracetamol) from the sponges was assessed as a function of polysaccharide composition. It was noted that the sponges had a flexible yet strong texture, as assessed macroscopically. Measurement of the resistance to compression ('hardness') indicated that the chitosan sponges were the 'hardest' while the alginate sponges showed the least resistance to compression, with all sponges showing a high degree of recovery. In contrast, the breaking force (tensile force) of the sponges were greatest for the single component systems, while the elongation prior to breaking was similar for each material. SEM studies indicated that the mixed systems had a less well-defined microstructure than the single component sponges. This was ascribed to the two polysaccharides interacting in aqueous solution via coulombic forces, leading to a more randomly ordered network being formed on freezing. Dissolution studies indicated that systems containing chitosan alone showed the slowest release profile, with the mixed systems showing a relatively rapid dissolution profile. The use of chitosan and alginates together, therefore, appears to allow the formulator to manipulate both the mechanical properties and the drug release properties of the sponges.

Effect of composition on the physicochemical properties and active substance release from gelatin-alginate sponge

The aim the study was physicochemically characterize and develop ability of the active substance (cefradine) from the implantable porous carriers. The drug delivery systems consisting of the gelatine and alginic acid sodium salt and glycerol (GL) or peanut oil (AO). Gelatin-alginate sponge was prepared by foamed components and next freeze-dried this foam. The composition of the sponges affected on the sorption ability and on the stability to proteolytic enzymes. Owing to porous structure obtained specific profile of active substance release.

Sodium alginate microspheres of metoprolol tartrate for intranasal systemic delivery: development and evaluation

Bioadhesive sodium alginate microspheres of Metoprolol tartrate (MT) for intranasal systemic delivery were prepared to avoid the first-pass effect, as an alternative therapy to injection, and to obtain improved therapeutic efficacy in the treatment of hypertension and angina pectoris. The microspheres (Ms) were prepared using emulsification--cross-linking method. The formulation variables were drug loading, polymer concentration, cross-linking agent concentration, and cross-linking time. The Ms were evaluated for characteristics, like particle size, incorporation efficiency, swelling ability, in vitro bioadhesion, in vitro drug release, and in vivo pharmacodynamic performance in rabbits against isoprenaline-induced tachycardia. Treatment of in vitro data to different kinetic equations indicated matrix-diffusion controlled drug delivery from sodium alginate Ms. Polymer concentration, cross-linking agent concentration, and cross-linking time influenced the drug release profiles significantly. In vivo studies indicated significantly improved therapeutic efficacy of MT from Ms with sustained and controlled inhibition of isoprenaline-induced tachycardia as compared with oral and nasal administration of drug solution.

Boar semen controlled delivery system: storage and in vitro spermatozoa release

Swine spermatozoa were encapsulated in barium alginate and protamine-barium alginate membranes to lengthen their preservation time and to provide a means of controlling their release. Precocious acrosome reactions and secondary anomalies were measured as indices of semen quality. These characteristics were observed for two forms of encapsulated spermatozoa when stored at 18 and 38 degrees C for 24 h and for semen diluted in a classical extender at both temperatures. The results indicate that encapsulation enhances semen preservation, providing protection against membrane damage upon dilution. The effect is even more evident at the higher temperature (38 degrees C), where cell metabolism is higher. An in vitro release test of spermatozoa showed a massive cell delivery from barium alginate capsules within 6 h, and a slow release from protamine-barium alginate capsules. The properties of spermatozoa 24 h after release did not differ from the semen stored at the same temperature in capsules, indicating that the release process does not impair semen quality.

Effects of cellulose derivatives and poly(ethylene oxide)-poly(propylene oxide) tri-block copolymers (Pluronic)surfactants) on the properties of alginate based microspheres and their interactions with phagocytic cells

The goal of this study was to examine the phagocytosis of alginate based microspheres with different surface properties. Favorable interaction with macrophages is critical for uptake subsequent processing of the microspheres used for oral vaccine delivery. We examined the effects of size of alginate microspheres and hydrophobicity on cellular uptake. We also examined the toxicity of formulation components to phagocytic cells. Alginate microspheres were made by the emulsion-cross-linking technique. Five different formulations of microspheres were evaluated for size, hydrophobicity, cellular uptake and toxicity to macrophages. The formulations examined were: alginate alone (A), alginate with methylcellulose (AA) AA with Pluronic L61 (AA61), alginate with hydroxypropyl methylcellulose (AK3), and AK3 with Pluronic (L61 (AK3 61). Microspheres with without poly-L-lysine (PLL) coating were tested. The mean volume sizes of A, AA, AA61, AK3, AK3 61 microspheres (MS) were 11, 10.5, 3.8, 8.7 and 3.9 mocrom, respectively. After coating them with PLL the mean volume sizes were 10.4, 10, 3.7, 8.8 and 3.5 microm, respectively. Hydrophobicity of the microspheres was evaluated by measuring contact angle on a glass slide coated with the microspheres. The contact angles measured using a goniometer on A, AA, AA61, AK3, AK3 61 MS were 20, 34.8, 71, 29 and 80 degrees, respectively whereas those MS coated with PLL were 49.7, 55.8, 91, 48.25 and 84.4 degrees, respectively. Cellular uptake studies using flow cytometery revealed that AA61 MS coated with PLL were phagocytosed most often by mouse macrophages. There was no statistically significant difference in cellular uptake among those MS without PLL coating. Toxicity to macrophages was shown to depend on the ratio of microspheres to cells. These studies suggest that formulation can dramatically affect the physical characteristics of alginate MS in ways that can affect how they will interact with cells in the body when administered as a vaccine delivery system.

Characteristics of hyaluronate-hydroxyethyl acrylate blend gel and release of cationic amphiphilic solutes

Hyaluronate-hydroxyethyl acrylate blend gel (HA-PHEA) were prepared to modify the brittleness of hyaluronate gel (HA) and the characteristics of HA-PHEA gel were compared with those of HA and polyhydroxyethyl acrylate (PHEA) gels. These gels were high in water content and transparent. HA-PHEA gel was improved in viscoelastic properties due to the elasticity and the high affinity with water of PHEA, and the drying-swelling cycles became reversible. The effective charge densities theta of the gels estimated from membrane potentials were -0.002, -0.008 and 0 mol dm(-3) for HA-PHEA, HA and PHEA gels. Effects of electro- static and nonelectrostatic interactions on absorptions and releases were studied using sodium benzoate (NaBA) as an anionic solute, and methylene blue (MB), chlorpromazine (CPHCl) and benzethonium chloride (BZTCl) as cationic solutes, in which CPHCl and BZTCl are cationic amphiphilic solutes. The releases of MB, CPHCl and BZTCl from HA-PHEA and HA gels were suppressed comparing with those of NaBA. By adding salts, the releases of MB and CPHCl were enhanced but those of BZTCl were suppressed due to enhancement of the intra- and intermicelle formation. In the releases of the cationic solutes from HA-PHEA gel, electrostatic and nonelectrostatic interactions with HA were found to play important roles. Behaviors of the releases from HA-PHEA gel were found to possess the features of HA gel.

Alginate/poly-L-lysine microparticles for the intestinal delivery of antisense oligonucleotides

PURPOSE

A microparticle carrier based on alginate and poly-L-lysine was developed and evaluated for the delivery of antisense oligonucleotides at the intestinal site. Formulations of oligonucleotide-loaded microparticles having differences in the carrier molecular weight and composition were characterized in vitro and in vivo.

METHODS

Polymeric microparticles were prepared by ionotropic gelation and crosslinking of alginate with calcium ions and poly-L-lysine. The loading of the antisense oligonucleotide into the microparticles was achieved by absorption in aqueous medium. The association capacity, loading and particle size of the microparticles were characterized. The in vivo performances of various formulations after intrajejunal administration were studied in rat and in dog models.

RESULTS

Microparticles had a sponge-like structure and an oligonucleotide loading of 27-35%. The composition of the medium affected the particle size and the in vitro release profiles. The oligonucleotide bioavailability after intrajejunal administration to rats in the presence of permeation enhancers was good for most of the tested systems. The application of microparticles in powder form compared to an equivalent suspension improved the intrajejunal bioavailability of the oligonucleotide (25% and 10% respectively) in rats. On the contrary, the intrajejunal administration to dogs resulted in poor oligonucleotide bioavailability (0.42%).

CONCLUSIONS

The formulation of antisense oligonucleotides within alginate and poly-L-lysine microparticles is a promising strategy for the oral application.

Time-programmed pulsatile release of dextran from calcium-alginate gel beads coated with carboxy-n-propylacrylamide copolymers

Time-programmed release of macromolecular drugs was achieved by utilization of calcium-alginate gel beads modified with coated copolymer layers. Modified calcium-alginate gel beads coated with poly(carboxy-n-propylacrylamide-co-dimethylacrylamide) [poly(CNPAAm-co-DMAAm)] (22.7 mol% of CNPAAm) of varying coating thickness from 25 to 125 microm were developed as drug carriers. Model macromolecular drugs used were fluorescein isothiocyanate (FITC)-labeled dextrans with different molecular weights ranging from 9400 to 145000. FITC-dextran release was strongly dependent on both copolymer coating thicknesses and the dextran molecular weights. Release of FITC-dextran (MW 9400) followed Fickian diffusion according to t(1/2) dependence, indicating that the drug diffusion is the main driving force for release of dextran MW 9400. Release of higher molecular weight FITC-dextrans (71,00 and 145,00) exhibited a burst-effect preceded by a preset lag time. These release profiles were governed by the dissociation of calcium ions from polyguluronate sequences in alginate molecules along with the diffusion of sodium ions into the gel bead core. This created osmotic pressure inside the gel, inducing breakage of the coated copolymer layer and accelerated drug release. Burst release of macromolecular drugs thus occurred after a certain lag period. The lag time was regulated by the copolymer coat thickness. A pulsatile release of FITC-dextran was demonstrated by combining a series of modified alginate gel beads in a single batch.

Behavior of alginate gel beads containing chitosan salt prepared with water-soluble vitamins

Alginate gel beads were prepared which contained weak acid salts of chitosan (Alg-CS) and water-soluble vitamins (e.g. ascorbic acid (AS)) and the behavior of the beads, uptake of bile acids was investigated in vitro. The Alg-CS beads rapidly took up bile acid and this phenomenon was observed for both hydrogel beads and dried beads. About 120 micromol of taurocholic acid was taken up into Alg-CS (1 g) prepared with orotic acid. Dried Alg-CS is the granule which can be made easily, and keeps the ability of CS salt, and all elements can be taken as a food. Therefore, Alg-CS could serve as a useful dietary agent for the prevention of hyperlipidemia.

The release behavior of brilliant blue from calcium-alginate gel beads coated by chitosan: the preparation method effect

The aim of this study is to reveal how the release behavior of a model drug (brilliant blue, BB) from chitosan coating calcium-alginate gel beads (CCAGB) was influenced by the preparation methods. The CCAGB were prepared by dropping alginate solution into CaCl(2)/chitosan solution (method 1(a)), or into chitosan solution then gelled by CaCl(2) (method 1(b)), or into CaCl(2) solution then coated by chitosan (method 2). Scanning electron microscopy was used for morphology observation, and elemental analysis was applied to determine the chitosan content bound on calcium-alginate gel beads (CAGB). Compared to CAGB, the dried CCAGB had poorer shape and rougher surface morphology especially in methods 1(a) and (b); moreover, CCAGB was found to be more instable in 0.9% NaCl and serious burst of beads occurred when high concentration of alginate (3.0 and 5.0% w/v) was used. The influence on BB release from the beads by chitosan coating was not only related to the chitosan density on bead surface, but also preparation method and other factors. Under un-dried bead state in method 1(a), the increase of chitosan content prolonged BB release in 0.9% (w/v) NaCl; while in method 2, the increase of chitosan concentration over 0.1% (w/v) (3.0% (w/v) alginate concentration was used) resulted in more serious burst of beads and hence facilitated BB release. Furthermore, in both methods 1(a) and 2, the increase of alginate from 1.5 to 3.0 or 5.0% (w/v) usually resulted in the significant burst of beads and accelerated BB release when 0.3 or 0.5% (w/v) chitosan was used for coating. Drying process greatly influenced BB release profile due to the destroying of alginate-chitosan film. The acceleration of BB release from CCAGB by drying process was more significant in the case of method 1 than of method 2.

Factors affecting protein release from alginate-chitosan coacervate microcapsules during production and gastric/intestinal simulation

A series of experiments was performed to evaluate the influence of a number of physico-chemical factors on the diffusion of a model protein, bovine serum albumin (BSA), from dried chitosan-coated alginate microcapsules. Diffusion of BSA was quantified during the microcapsule manufacture processes (gelation, washing, rinsing) and during incubation in conditions simulating the pH encountered during the gastric (0.1 N HCl; pH 1.5) and intestinal (200 mM Tris-HCl; pH 7.5) phases of digestion. Factors tested included alginate and chitosan concentration, calcium chloride (CaCl2) concentration in the gelation medium, loading rate, chitosan molecular mass and pH of the gelation medium. Microcapsule size and gelation time were altered in order to determine their effects on protein retention. Alginate and chitosan concentration significantly influenced BSA retention during microcapsule manufacture and acid incubation, as did calcium chloride concentration in the gelation medium (P<0.05). BSA retention during manufacture was not significantly altered by protein loading rate or pH of the encapsulation medium, however, protein retention during acid incubation decreased significantly with increasing protein loading rate and encapsulation medium pH (P<0.05). Microcapsules that were washed with acetone following manufacture demonstrated significantly increased protein retention during acid incubation (P<0.05). In microcapsules that had been acetone-dried to a point whereby their mass was reduced to 10% of that immediately following encapsulation, protein retention was over 80% following 24-h acid incubation vs. only 20% protein retention from non acetone-dried microcapsules. The presence of calcium in the neutral buffer medium significantly reduced BSA diffusion in a concentration-dependent manner (P<0.05).

Degradation of partially oxidized alginate and its potential application for tissue engineering

Alginate has been widely used in a variety of biomedical applications including drug delivery and cell transplantation. However, alginate itself has a very slow degradation rate, and its gels degrade in an uncontrollable manner, releasing high molecular weight strands that may have difficulty being cleared from the body. We hypothesized that the periodate oxidation of alginate, which cleaves the carbon-carbon bond of the cis-diol group in the uronate residue and alters the chain conformation, would result in promoting the hydrolysis of alginate in aqueous solutions. Alginate, oxidized to a low extent (approximately 5%), degraded with a rate depending on the pH and temperature of the solution. This polymer was still capable of being ionically cross-linked with calcium ions to form gels, which degraded within 9 days in PBS solution. Finally, the use of these degradable alginate-derived hydrogels greatly improved cartilage-like tissue formation in vivo, as compared to alginate hydrogels.

Natural gums and modified natural gums as sustained-release carriers

Although natural gums and their derivatives are used widely in pharmaceutical dosage forms, their use as biodegradable polymeric materials to deliver bioactive agents has been hampered by the synthetic materials. These natural polysaccharides do hold advantages over the synthetic polymers, generally because they are nontoxic, less expensive, and freely available. Natural gums can also be modified to have tailor-made materials for drug delivery systems and thus can compete with the synthetic biodegradable excipients available in the market. In this review, recent developments in the area of natural gums and their derivatives as carriers in the sustained release of drugs are explored.

Preparation of cross-linked sodium alginate microparticles using glutaraldehyde in methanol

Polymeric sodium alginate microparticles were prepared by precipitating sodium alginate in methanol, followed by cross-linking with glutaraldehyde. The extent of cross-linking was controlled by the time of exposure to glutaraldehyde. The topology of microparticles was characterized by scanning electron microscopy (SEM), which indicated smooth surfaces. The equilibrium swelling experiments were carried out in water to observe the effect of cross-linking and drug loading for better utility of microparticles. It was found that swelling decreased, but drug loading increased, with an increase in cross-linking of the matrix.

Polycation-coated polyanion microspheres of urease for urea hydrolysis

Urease (EC 3.5.1.5) was immobilized within polyanionic carboxymethylcellulose/alginate (CMC/Alg) microspheres coated with a cationic polysaccharide, chitosan (C). Coating with chitosan improved the mechanically durability of the polyanionic microspheres, as well as increased enzyme immobilization yield [approximately 0.4 mg.mL-1 gel]. The effects of chitosan coating and CMC/Alg ratio on the water uptake and spherical morphology of the microspheres were investigated. The optimal pH of urease was not extensively affected by the immobilization procedure. However, the optimal temperature of urease activity increased upto 60 and 65 degrees C within CMC/Alg and C(CMC/Alg) microspheres, respectively, while the optimum for the free enzyme was 50 degrees C. The half life (t1/2) and deactivation rate constant (kd) of free urease were 79 min and 8.77 x 10(-3) min-1, respectively, whilst the t1/2 and kd values of urease within polyanion and polycation-coated polyanion microspheres were 142 min and 4.88 x 10(-3).min-1, and 179 min and 3.87 x 10(-3).min-1, at 80 degrees C, respectively. While the activation energy of the hydrolysis reaction of free urease was found to be 11.86 kJ.M-1.dm-3, it increased to 18.91 and 20.02 kJ.M-1.dm-3, for the immobilized urease within CMC/Alg and C(CMC/Alg) microspheres, respectively. The free enzyme exhibited K(m) and Vmax values of 2.85 mM.dm-3 and 31.9 mM.dm-3.s-1.g-1p-1, respectively, whilst the K(m) and Vmax for urease within polyanion and polycation-coated polyanion microspheres were 3.94 mM.dm-3 and 73.4 mM.dm-3.s-1.g-1.p-1, and 4.22 mM.dm-3 and 81.4 mM.dm-3.s-1.g-1.p-1, in the same order. C(CMC/Alg) microspheres showed a nearly stable urease activity of around 80-85% of the initial maximum activity, after the first 100 minutes.

[The effect of the microenvironment of the liver tissues on the dynamic resorption of hemostatic resorbable materials and of adhesive compositions]

In experiment there was studied up the cells and tissues reaction on implantation of hemostatic alginate material "Gram-1", "hemostatic gauze" preparation, fibrinous glue composition and sulfoacrylate adhesive glue MK-3.

In vivo evaluation of a novel alginate dressing

Alginate dressings are currently used in the management of epidermal and dermal wounds, and provide a moist environment that leads to rapid granulation and reepithelialization. However, a cytotoxic effect on proliferation of fibroblasts and residual material with inflammation in healing wounds have been reported recently. We have developed a new alginate dressing (AGA-100), which does not have an inhibitory effect on proliferation of fibroblasts. The purpose of this study was to evaluate the new alginate dressing with respect to wound healing in full- and partial-thickness pig wounds and with respect to biodegradation following implantation into rabbit muscle. Kaltostat and Sorbsan, both well-established commercial dressings, were used as control. The closure rate of full-thickness wounds treated with AGA-100 was significantly higher on day 15 compared with that with Kaltostat and Sorbsan. Reepithelialization rate of partial-thickness wounds treated with Sorbsan was statistically significantly lower on day 3 than those with the other two dressings. As to dressing debris remained in the healing wound, a large amount of foreign debris was noted in all the full-thickness wounds treated with Kaltostat or Sorbsan, while only about one-third of wounds treated with AGA-100 showed a little dressing debris. AGA-100 implanted into the muscle of rabbits was bioresorbed completely within 3 months. Therefore, dressing residue in AGA-100-treated full-thickness wounds might be fully absorbed in a few months. In conclusion, it is shown that our newly developed AGA-100 possesses superior properties compared with typical alginate dressings.

Biodegradable alginate microspheres as a delivery system for naked DNA

Sodium alginate is a naturally occurring polysaccharide that can easily be polymerized into a solid matrix to form microspheres. These biodegradable microspheres were used to encapsulate plasmid DNA containing the bacterial beta-galactosidase (LacZ) gene under the control of either the cytomegalovirus (CMV) immediate-early promoter or the Rous sarcoma virus (RSV) early promoter. Mice inoculated orally with microspheres containing plasmid DNA expressed LacZ in the intestine, spleen and liver. Inoculation of mice with microspheres containing both the plasmid DNA and bovine adenovirus type 3 (BAd3) resulted in a significant increase in LacZ expression compared to those inoculated with microspheres containing only the plasmid DNA. Our results suggest that adenoviruses are capable of augumenting transgene expression by plasmid DNA both in vitro and in vivo.

Lipid grafts of egg-box complex: a new supramolecular biovector for 5-fluorouracil delivery

An attempt was made to improve the pharmacokinetic behaviour of 5-fluorouracil (5-FU) by incorporating it into lipoprotein imitating synthetic carrier 'supramolecular biovector (SMBV)' which is an important prerequisite for achieving its better therapeutic performance against cancer. The polysaccharide core of SMBVs was prepared by ionotropic gelation technique by cross-linking polyguluronate units in the alginate molecules with calcium ions to form so called 'egg-box structure'. The formulation and process variables were optimized to obtain particles of nanometer size range. Hydrophobization was carried out by fatty-acylation on the surface followed by phospholipid coating. Palmitoyl polyethylene glycol (p-PEG) was anchored to impart stealth behaviour. The scanning electron microscopy showed discrete spheres of average diameter 748 nm. Polydispersity was estimated to be 0.37. Overall zeta potential was -21.3 mV. The drug loading capacity and encapsulation efficiency was found to be 10.0% and 97.9%, respectively. The release from drug solution (AP) followed zero-order kinetics. Higuchi release pattern was obtained for egg-box complex cores (AP1) while first-order pattern was followed for fatty acylated (AP2) and lipid coated cores before (AP3) and after p-PEG anchoring (AP4). The amount of drug liberated in 24 h was in the order AP > AP1 > AP2 > AP4 > AP3. The release pattern obtained was a combined effect of drug diffusion through egg-box matrix as well as partitioning in hydrophobic layer and p-PEG layer around the SMBV. The stability study showed negligible leakage and no appreciable change in particle size upon storage at different temperatures which is an indication of good stability of SMBV formulation. The plasma clearance data revealed increase in circulation half-life of drug and bioavailability. Tissue distribution data obtained was a result of competitive uptake of formulations from tissue macrophages and lymphatics depending upon its surface characteristics and residence period in vascular system. The enhanced delivery of drug to lymphatics and improvement in its half-life render SMBVs useful for control of metastasis and tumour growth.

Aqueous-based microcapsules are detected primarily in gut-associated dendritic cells after oral inoculation of mice

We previously found that aqueous-based microencapsulation enhanced virus-specific humoral immune responses after oral inoculation of mice. However, the mechanism by which microencapsulation enhances immunogenicity remains unclear. We found that spermine-alginate microcapsules were detected primarily in gut-associated dendritic cells (i.e. CD11c/CD18+, Ia+, CD11b-, CD45R-) after oral inoculation of adult mice. Microencapsulation may enhance immunogenicity by involving antigen presenting cells which are more efficient than those recruited during natural infection.

Immobilisation of whole bacterial cells for anaerobic biotransformations

Anaerobically grown cells of Escherichia coli were immobilised within a range of entrapment matrices and packed into a column under standard conditions, and the ability of the immobilised cells to reduce nitrite (0.5 mM) was measured at a range of flow rates using sodium formate (20 mM) as the electron donor for nitrite reduction. A flow-rate/activity plot was constructed for each flow-through reactor and RA1/2 values (residence time corresponding to 50% nitrite removal) calculated for each reactor type. Cells immobilised in flat and hollow-fibre membranes were the most effective (RA1/2 = 0.35 h and 0.47 h respectively), with cells entrapped by dialysis membrane (1.53 h), alginate beads (1.93 h), Hypol foam (2.31 h) and polyacrylamide gel (50% nitrite not removed at maximum residence time tested: 4.9 h) performing progressively less effectively. Cells grown as a biofilm on a range of support materials were also tested in comparable packed-bed reactors. Cell loss from these supports was extensive and contributed to poor performance of the reactors despite high initial biomass loadings (RA1/2 values using raschig rings, coke and activated-carbon supports: 1.6 h, 2.3 h and 1.0 h respectively). Biofilms grown on Pharmacia microcarrier supports and used in packed and also fluidised beds were more stable and the performance of these reactors was superior to that of biofilm reactors using other supports, and comparable to that of the membrane reactors (RA1/2 values for Cytoline 2, Cytopore 2 and Cytodex 3: 0.76 h, 0.56 h, 0.68 h respectively).

An evaluation of the local reaction and biodegradation of calcium sodium alginate (Kaltostat) following subcutaneous implantation in the rat

Kaltostat swabs were implanted subcutaneously in rats to evaluate their biodegradability and ability to evoke local tissue reactions. Implant sites were evaluated after 24 h and after 7 days, 28 days and 12 weeks. Histological sections showed no noticeable degradation of the Kaltostat within the 3 month observation period, contrary to some published reports. Following subsidence of a modest foreign body reaction, implants became embedded in thin fibrous sheaths which were infiltrated with vascular channels and fibroblasts. This study demonstrates that Kaltostat fibres are well tolerated following subcutaneous implantation in the rat model and present no obvious toxic risk or contraindication to their use as wound dressings or as haemostatic agents in general surgery.

An investigation into the effect of cimetidine pre-treatment on raft formation of an anti-reflux agent

It is now becoming common practice to co-administer H2-receptor antagonists and anti-reflux agents in the treatment of reflux oesophagitis. The mechanism by which anti-reflux agents achieve flotation requires a small amount of gastric acid to be present in the stomach. This study investigated whether an anti-reflux agent would remain effective after the decrease in acid secretion produced by a typical clinical dosage regimen of cimetidine (400 mg q.d.s., 7 days). Gastric distribution and residence of a meal and an anti-reflux agent were assessed in 12 normal subjects using gamma scintigraphy. The area under the gastric and fundal emptying curves demonstrated that Liquid Gaviscon (sodium alginate compound) had a significantly greater gastric residence than the meal, both during the control period and after cimetidine pretreatment, and that the majority of the Gaviscon was located in the fundus. The distribution of Gaviscon into the fundus was not affected by cimetidine pretreatment. Cimetidine pre-treatment slightly, but not significantly, increased the time for half the meal and the Gaviscon to empty from the stomach. The results suggest that the mechanism of action of Liquid Gaviscon is not compromised by concurrent H2-antagonist therapy.

FT-IR measurement of emulsified cationic DMAEMA-MMA adsorption to calcium alginate

The rate of adsorption of aqueous emulsions of DMAEMA-MMA copolymers to calcium alginate substrates was examined using ATR FT-IR spectroscopy. This work was undertaken as part of the development of a hybrid artificial pancreas. Aqueous DMAEMA-MMA copolymer emulsions containing < 25 mol% DMAEMA were slowly adsorbed to calcium alginate substrates; emulsions of 50 mol% DMAEMA-MMA copolymer were adsorbed rapidly to calcium alginate gels. The adsorption of 50 mol% DMAEMA-MMA copolymer emulsions to calcium alginate gels was attributed to electrostatic rather than simple van der Waals' attractive forces.

Effect of time of dosing relative to a meal on the raft formation of an anti-reflux agent

Gamma scintigraphy was used in twelve healthy volunteers to establish whether the time of dosing of Liquid Gaviscon relative to a meal influenced its therapeutic action. Indium-113m labelled Liquid Gaviscon was administered to fasted subjects, 30 min after a technetium-99m labelled meal or immediately before ingestion of the meal. The time for 50% of the Gaviscon to empty from the stomach was 0.36 +/- 0.13 h, 3.10 +/- 0.31 h and 0.68 +/- 0.04 h (s.e.m.), respectively. The preparation was found to empty rapidly from the fasted stomach and could not be floated on a meal consumed subsequently. For raft formation to occur, Liquid Gaviscon should be taken 30 min after a meal.

Kinetic behavior and interaction of bacampicillin in alginic acid solution at neural pH region

Stabilization of bacampicillin (BAPC) in suspension was examined by the addition of alginic acid (Alg). BAPC formed a slightly water-soluble adduct (BAPC-Alg) with Alg, in which BAPC and Alg were presumed to be linked by ionic bonding. However, the suspension of this chemically stable adduct showed a lability to a suspension of BAPC alone; chemically very unstable particles of BAPC base were deposited in the suspension. In contrast, when BAPC-Alg adduct was suspended in 1.0% Alg solution at the same pH region, the precipitation of the particles of BAPC base were not observed. This stabilization is supposed to be due not only to the chemical stability of the adduct, but also to an inhibition of the deposition of an unstable BAPC base particles by Alg.

[Chemico-physical property and bile acid binding capacity of several antacids]

Liquid alginate (Gaviscon) binds small amount of bile acids. At pH 7 its viscosity (at low shear rate) is higher than that of other antiacids. High viscosity reduces the diffusion rate of bile salts and glucose and this property can play a role in the treatment of gastro-esophageal and duodeno-gastric refluxes.

Use of 111In-labeled alginate to study the pH dependence of alginic acid anti-esophageal reflux barrier

Mixtures of alginic acid and antacid, when given orally, react with gastric acid to form a viscous barrier (raft) which floats on the surface of the gastric contents. 111In was used to label magnesium alginate in order to study the effect of gastric acidity on the extent of formation of the raft. In vitro, acid concentrations less than 0.05 N diminished raft formation. In vivo, raft formation was significantly better in normal subjects who ingested dilute acid with the labeled alginate/antacid than in subjects who ingested the labeled alginate/antacid with plain water. Gastric emptying of the labeled alginate was also slowed by the presence of acidified gastric contents. These results suggest that the formation of an effective alginic acid antireflux barrier requires acidic gastric contents.