Biomedical subjects

D J Burgess

Publications and source records attributed to D J Burgess.

At least 19 recordsLinked to original sources

PubMed2006

Profile of movement demands of national football players in Australia.

Descriptive data on game movement demands of contemporary players in the Australian National Soccer League (NSL, now the A League) are lacking. The purpose of this study was to profile movement demands of NSL games and specifically analyse distance covered, time in various speed categories (e.g., walking, jogging, striding, etc.), number of sprint speed efforts and overall mean player speed. Video tapes of 45 players from the 2002 to 2003 NSL season were analysed for whole- and half-game movement patterns and game statistics using Trak Performance software. Bivariate and ANOVA statistics were used for between game halves and positional comparisons. Results showed no changes to the frequency and speed of high intensity demands in both halves of the game. However, a 14% slower overall speed in the second half of the game when compared with the first half was attributed to fewer observations of the low intensity movements (9.0% less walking and 12.4% less jogging) and more stationary periods. Engagement in game events such as kicking and passing was also 11.2% less frequent in the second versus first half of games. Position-specific results of higher movement speeds of midfield players (7.2kmh(-1)), compared with defenders (6.1kmh(-1)), agree with previous results from international professional leagues. The results provide position-specific directions for future conditioning drills and benchmark fitness requirements in high level soccer players. The results also highlight the challenge to ensure consistency of second-half performances for elite level soccer players in Australia.

Adult↗

PubMed2003

Competitive interfacial adsorption of blood proteins.

The competitive adsorption of blood proteins is of great importance for the treatment of thrombosis using a colloidal drug delivery system. The aim of this study is to investigate competitive adsorption of albumin (BSA) and human immunoglobulin G (HIgG) against fibrinogen (Fb). The competitive adsorption of blood proteins was investigated using interfacial rheology at physiological pH. The influence of bulk concentration, temperature and pH on the interfacial adsorption of protein molecules was determined at the air/aqueous interface. As expected, the results indicated that increase in bulk concentration enhanced the interfacial adsorption. Structure and molecular weight of the protein molecules under investigation had influence on interfacial adsorption leading to a competition at the interface. HIgG is more flexible and surface active molecule than BSA. Thus, HIgG replaced BSA and Fb at the air/aqueous interface. In the presence of Fb, BSA adsorbed rapidly initially and then, was replaced by Fb at the interface. The kinetics of displacement of albumin at the interface was rather slow. In conclusion, the investigation of competitive adsorption of blood proteins may be useful biotechnologically, as it will provide useful information for the production of an antithrombogenic material, which will adsorb albumin rather than Fb.

Adsorption↗

PubMed2003

Co-delivery of IL-2 or liposomes augment the responses of mice to a DNA vaccine for pseudorabies virus IE180.

Recently we have demonstrated, with a DNA vaccine, that the immediate early protein (IE180) of pseudorabies virus provides a moderate level of protection in mice. In order to improve its immunogenicity and protective capacity, this IE180 DNA vaccine was delivered to C3H/HeJ mice either in combination with an IL-2 expressing plasmid or complexed with cationic liposomes. Co-delivery of the vaccine and IL-2 DNA by gene gun resulted in seroconversion in 5/5 of the vaccinated mice after a single administration, whereas two intramuscular (i.m.) injections were required to achieve seroconversion in all mice. Antibody and delayed-type hypersensitivity responses were augmented in mice, which received the DNA vaccine and the IL-2 gene compared to those of mice receiving the DNA vaccine alone. In addition, the time of death after challenge was significantly delayed in mice, which received the IL-2 gene. The proportion of surviving mice (40%), however, was similar to that obtained in mice which received the vaccine alone by gene gun. Liposome-mediated vaccine delivery also resulted in a higher rate of seroconversion when compared with that induced by the naked DNA vaccine. Thus, all vaccinated mice seroconverted after either two i.v. or three i.m. injections of the liposome/DNA complex, with 40 and 25% of these mice being protected against challenge, respectively. These data support that co-administration of the IE180 DNA vaccine with the IL-2 gene or delivery in liposomes are two effective approaches to increase its immunogenicity.

Animals↗

PubMed2002

In vivo evaluation of a dexamethasone/PLGA microsphere system designed to suppress the inflammatory tissue response to implantable medical devices.

The purpose of this research effort was to evaluate in vivo a newly developed dexamethasone/PLGA microsphere system designed to suppress the inflammatory tissue response to an implanted device, in this case a biosensor. The microspheres were prepared using an oil/water (O/W) emulsion technique. The microsphere system was composed of drug-loaded microspheres (including newly formulated and predegraded microspheres) and free dexamethasone. The combination of the drug and drug-loaded microspheres provided burst release of dexamethasone followed by continuous release from days 2-14. Continuous release to at least 30 days was achieved by mixing predegraded and newly formulated microspheres. The ability of our mixed microsphere system to control tissue reactions to an implant then was tested in vivo using cotton thread sutures to induce inflammation subcutaneously in Sprague-Dawley rats. Two different in vivo studies were performed, the first to find the dosage level of dexamethasone that effectively would suppress the acute inflammatory reaction and the second to show how effective the dexamethasone delivered by PLGA microspheres was in suppressing chronic inflammatory response to an implant. The first in vivo study showed that 0.1 to 0.8 mg of dexamethasone at the site minimized the acute inflammatory reaction. The second in vivo study showed that our mixed microsphere system suppressed the inflammatory response to an implanted suture for at least 1 month. This study has proven the viability of microsphere delivery of an anti-inflammatory to control the inflammatory reaction at an implant site.

Animals↗

PubMed2002

Dexamethasone/PLGA microspheres for continuous delivery of an anti-inflammatory drug for implantable medical devices.

The purpose of this research was to develop polylactic-co-glycolic acid (PLGA) microspheres for continuous delivery of dexamethasone for over a 1-month period, in an effort to suppress the acute and chronic inflammatory reactions to implants such as biosensors, which interfere with their functionality. The microspheres were prepared using an oil-in-water emulsion technique. The oil phase was composed of 9:1 dichloromethane to methanol with dissolved PLGA and dexamethasone. Some microspheres were predegraded for 1 or 2 weeks. Ten percent of polyethylene glycol was added to the oil phase in alternative formulations to delay drug release. The in vitro release studies were performed in a constant temperature (37 C) warm room, in phosphate-buffered saline at sink conditions. Drug loading and release rates were determined by HPLC-UV analysis. The standard microsphere systems did not provide the desired release profile since, following an initial burst release, a delay of 2 weeks occurred prior to continuous drug release. Predegraded microspheres started to release dexamethasone immediately but the rate of release decreased after only 2 weeks. A mixed standard and predegraded microsphere system was used to avoid this delay and to provide continuous release of dexamethasone for 1 month.

Anti-Inflammatory Agents↗

PubMed2001

Preparation and characterization of gelatin surface modified PLGA microspheres.

This study optimized conditions for preparing and characterizing gelatin surface modified poly (lactic-co-glycolic acid) (PLGA) copolymer microspheres and determined this system's interaction with fibronectin. Some gelatin microspheres have an affinity for fibronectin-bearing surfaces; these microspheres exploit the interaction between gelatin and fibronectin. PLGA copolymer microspheres were selected because they have reproducible and slow-release characteristics in vivo. The PLGA microspheres were surface modified with gelatin to impart fibronectin recognition. Dexamethasone was incorporated into these microspheres because dexamethasone is beneficial in chronic human diseases associated with extra fibronectin expression (eg, cardiovascular disease, inflammatory disorders, rheumatoid arthritis). The gelatin surface modified PLGA microspheres (prepared by adsorption, conjugation, and spray coating) were investigated and characterized by encapsulation efficiency, particle size, in vitro release, and affinity for fibronectin. The gelatin-coated PLGA microspheres had higher interaction with fibronectin compared with the other gelatin surface modified PLGA microspheres (adsorption and conjugation). Dexamethasone was released slowly (over 21 days) from gelatin surface modified PLGA microspheres.

Anti-Inflammatory Agents↗

PubMed2001

Formulation and release characteristics of poly(lactic-co-glycolic acid) microspheres containing chemically modified protein.

Chemical modification of proteins may influence their formulation into and release from polymeric microspheres. Three chemical modifications of rat serum albumin (RSA) were effected on the amine groups of this protein: conjugation with a polyanion using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, intermolecular cross-linking using glutaraldehyde, and reductive alkylation using propyl aldehyde. The modified proteins had different physicochemical properties as well as improved encapsulation efficiencies compared with native RSA microspheres. The microspheres were incubated at 37 degrees C for over one month to investigate the influence of protein modification on the release profiles. Microsphere degradation accelerated from the ninth day of the release studies and this coincided with an increase in the release rates. The degradation rates of poly(lactic-co-glycolic acid) microspheres containing either native or cross-linked RSA were more rapid than those containing either heparin conjugated or propylated RSA. This was in agreement with the release data, since the release of the native and cross-linked RSA were more rapid than those of the other modified proteins. The release profiles of the RSA-heparin conjugates and the propylated RSA were approximately zero rather than first order between the tenth and thirtieth day of study. Chemical modification of protein may be a useful method to increase encapsulation efficiency and to decrease release rates of proteins that are to be used in microsphere formulations of potent therapeutic proteins.

Animals↗

PubMed2000

Effect of nonionic surfactant on transport of surface-active and non-surface-active model drugs and emulsion stability in triphasic systems.

The effect of surfactant concentration on transport kinetics in emulsions using surface-active (phenobarbital, barbital) and non- surface-active (phenylazoaniline, benzocaine) model drugs is determined. Mineral oil was chosen as the oil phase and the nonionic surfactant polyoxyethylene-10-oleyl-ether (Brij 97) was chosen as the emulsifier. Model drug transport in the triphasic systems was investigated using side-by-side diffusion cells mounted with hydrophilic dialysis membranes (molecular weight cutoffs 1 kd and 50 kd) and a novel bulk equilibrium reverse dialysis bag technique. Emulsion stability was determined by droplet size analysis as a function of time, temperature, and the presence of model drugs, using photon correlation spectroscopy. Mineral oil/water (O/W) partition coefficients and aqueous solubilities were determined in the presence of surfactant. The transport rates of model drugs in emulsions increased with an increase in Brij 97 micellar concentrations up to 1.0% wt/vol and then decreased at higher surfactant concentrations. The transport profiles of the model drugs appeared to be governed by model drug O/W partition coefficient values and by micellar shape changes at higher surfactant concentrations. Total transport rates of phenobarbital and barbital were faster than those of phenylazoaniline and benzocaine. Excess surfactant affected the transport rates of the model drugs in the emulsions depending on drug surface activity and lipophilicity.

Barbital↗

PubMed2000

Mathematical modeling of surface-active and non-surface-active drug transport in emulsion systems.

Mathematical models were developed for the prediction of surface-active and non- surface-active drug transport in triphasic (oil, water, and micellar) emulsion systems as a function of micellar concentration. These models were evaluated by comparing experimental and simulated data. Fick's first law of diffusion with association of the surface-active or complexation nature of the drug with the surfactant was used to derive a transport model for surface-active drugs. This transport model assumes that the oil/water (O/W) partitioning process was fast compared with membrane transport and therefore drug transport was limited by the membrane. Consecutive rate equations were used to model transport of non-surface-active drugs in emulsion systems assuming that the O/W interface acts as a barrier to drug transport. Phenobarbital (PB) and barbital (B) were selected as surface-active model drugs. Phenylazoaniline (PAA) and benzocaine (BZ) were selected as non- surface-active model drugs. Transport studies at pH 7.0 were conducted using side-by-side diffusion cells and bulk equilibrium reverse dialysis bag techniques. According to the surface-active drug model, an increase in micellar concentration is expected to decrease drug-transport rates. Using the Microsoft EXCEL program, the non-surface-active drug model was fitted to the experimental data for the cumulative amount of the model drug that disappeared from the donor chamber. The oil/continuous phase partitioning rates (k1) and the membrane transport rates (k2) were estimated. The predicted data were consistent with the experimental data for both the surface-active and non- surface-active models.

Algorithms↗

PubMed2000

Effect of cationic surfactant on transport of surface-active and non-surface-active model drugs and emulsion stability in triphasic systems.

A study was carried out to determine the effect of excess surfactant on transport kinetics in emulsions, using surface-active (phenobarbital, barbital) and non-surface-active (phenylazoaniline, benzocaine) model drugs (pH 7.0). Mineral oil was chosen as the oil phase, and the ionic surfactant cetyltrimethylammonium bromide (CTAB) was chosen as the emulsifier. The effect of nonionic surfactant Brij 97 on transport kinetics of these model drugs were determined by authors elsewhere. Model drug transport in the triphasic systems was investigated using side-by-side diffusion cells mounted with hydrophilic dialysis membranes (molecular weight cutoffs 1 kD and 50 kD) and a novel bulk equilibrium reverse dialysis bag technique. Emulsion stability was determined by droplet size analysis as a function of time, temperature, and the presence of model drugs using photon correlation spectroscopy. Mineral oil/water partition coefficients and aqueous solubilities were determined in the presence of surfactant. The droplet size of the CTAB-stabilized emulsion system is bigger than that of the Brij 97-stabilized system because of the relatively less dense interfacial packing of the cationic surfactant. CTAB forms a complex with the model drugs because of ionic interaction between CTAB and the aromatic and azo groups of the model drugs. This complexation is expected to increase emulsion stability and affect model drug transport kinetics. The transport rates of model drugs in emulsions increased with increases in CTAB micellar concentrations up to 0.5% w/v and then decreased at higher surfactant concentrations. Total transport rates of phenobarbital and barbital were faster than those of phenylazoaniline and benzocaine. Excess surfactant affected the transport rates of the model drugs in the emulsions depending on drug surface activity and lipophilicity. The transport profiles of the model drugs appeared to be governed by model drug oil/water partition coefficient values and by micellar shape changes at higher surfactant concentrations.

Barbital↗

PubMed1999

A novel in vitro release method for submicron sized dispersed systems.

Sink conditions are often violated when using conventional release methods for dispersed systems. A novel reverse dialysis bag method was designed to overcome this problem. Model drug transport rates from submicron emulsions obtained using the conventional diffusion cell method and this novel method were compared. In the side-by-side diffusion cell method, emulsions were placed in the donor chamber and surfactant/buffer solutions in the receiver chamber. In the novel dialysis bag method, emulsions were diluted infinitely in the donor phase and surfactant/buffer solutions were placed in the receiver phase (dialysis bags). Slow release rates and linear release profiles were obtained using the side-by-side diffusion cell method apparently due to limited model drug solubility in the donor chamber resulting in violation of sink conditions. Biphasic release profiles were obtained using the dialysis bag method apparently due to an initial rapid release of free and micellar solubilized model drug from the donor to the receiver chambers followed by slow release from the oil droplets. Using both release methods, an initial increase and latter decrease in release rates were observed with increase in surfactant concentration. The initial increase was considered to be due to a decrease in the model drug oil-in-water partition coefficients and the subsequent decrease in release rates was due to micellar shape change (spheres to rods) causing a decrease in diffusion rates. Sink conditions were violated using the side-by-side diffusion cell method but were maintained in the dialysis bag method since emulsions were diluted infinitely in the donor phase.

Benzocaine↗

PubMed1998

Mathematical modelling of drug transport in emulsion systems.

Two mathematical models for the prediction of drug transport in triphasic (oil, water and micellar) emulsion systems as a function of micellar concentration have been developed and these models were evaluated by comparing experimental and simulated data. Fick's first law was used to derive a transport model for hydrophilic drugs, assuming that the oil/water (o/w) partitioning process was fast compared with membrane transport and therefore drug transport was limited by the membrane. Consecutive rate equations were used to model transport of hydrophobic drugs in emulsion systems assuming that the o/w interface acts as a barrier to drug transport. Benzoic acid and phenol were selected as hydrophilic model drugs. Phenylazoaniline and benzocaine were selected as hydrophobic model drugs. Transport studies at pH 3.0 and 7.0 were conducted using side-by-side diffusion cells. According to the hydrophilic model, an increase in micellar concentration is expected to decrease drug transport rates. The effective permeability coefficients (Peff) of drugs were calculated using an equation relating Peff and the total apparent volume of drug distribution (determined experimentally using drug/membrane permeability and partition coefficient values). The hydrophobic model was fitted to the experimental data for the cumulative amount of model drug in the receiver cells using a weighted least-squares estimation program (PCNONLIN). The oil/continuous phase partitioning rates (k1) and the membrane transport rates (k2) were estimated. The goodness of fit was assessed from the correlation coefficients of plots of predicted versus experimental data. The predicted data were consistent with the experimental data for both the hydrophilic and hydrophobic models.

Aniline Compounds↗

PubMed1998

Influence of interfacial rheological properties of mixed emulsifier films on the stability of water-in-oil-in-water emulsions.

The purpose of this study was to investigate the influence of mixtures of the emulsifiers Span 80, 83 and 85 and Tween 80 on multiple emulsion stability. An oscillatory ring-surface rheometer was used to measure interfacial elasticity at the oil-aqueous interface. Multiple emulsions were prepared via a two-step emulsification process and stability was evaluated by investigation of drug transport from freshly prepared and eight-day-old emulsions by use of a dialysis method. Photomicrography and droplet-size analysis of multiple emulsions were also conducted. Spans 80 and 83 were appreciably elastic (683.10+/-29.13 mNm(-1) and 1128.09+/-14.81 mNm(-1), respectively at 5% w/v) when present at the mineral oil-aqueous interface whereas Span 85 and Tween 80 were not (11.10+/-3.88 mNm(-1) (5% w/v) and 0 (0.1-5% w/v) respectively). The interfacial elasticities of Spans 80 and 83 decreased in the presence of Tween 80 in the aqueous phase; this was attributed to co-adsorption of Tween 80 at the interface or aqueous-phase solubilization of the Spans within mixed micelles, or both. Drug-transport studies indicated that drug release on storage was lower from water-in-oil-in-water (w/o/w) emulsions prepared with 5% w/v Span 80 or 83 and 0.1% w/v Tween 80 than from emulsions prepared with 5% w/v Spans 80 or 83 and 1% w/v Tween 80. Photomicrography and droplet-size analysis indicated the same trend-emulsions containing a higher percentage of Tween 80 were less stable. The relatively stable w/o/w emulsions (e.g. 5% w/v Spans 80 or 83 and 0.1% w/v Tween 80) contained a large number of multiple droplets for up to eight weeks of storage whereas the relatively unstable w/o/w emulsions (e.g., 5% w/v Span 85 and 0.1% w/v Tween 80 and 5% w/v Spans and 1% w/v Tween 80) contained mostly simple droplets after only one week of storage. The mean volume/weight droplet size decreased on storage with breakdown of these w/o/w emulsions to simple oil-in-water emulsions. There was a positive correlation between the interfacial elasticity and emulsion stability data. Mixed emulsifiers giving higher film strength, as quantified by interfacial elasticity measurements, resulted in more stable w/o/w emulsions.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1998

Influence of protein emulsifier interfacial properties on oil-in-water emulsion stability.

The purpose of this study was to determine whether the interfacial properties of emulsifier films could be related to emulsion stability and therefore be used as stability predictors using Bovine serum albumin (BSA) as a model oil-in water (o/w) emulsifier. Soybean o/w emulsions were prepared by ultrasonication, emulsion droplet interfacial charge was determined by microelectrophoresis, droplet size distribution was measured using an Accusizer, and centrifugal stress was studied using an ultracentrifuge. Real time, thermal kinetic, and centrifugal stress accelerated stability tests were performed. Stability data obtained from centrifugal stress tests followed the same trends as real time stability data and these data were in general agreement with stability predictions made based on interfacial properties. The thermal kinetic accelerated tests were not predictive of stability, because emulsion breakdown was rapid and did not allow differentiation between the emulsions. Emulsion stability increased with an increase in emulsifier concentration (emulsions prepared at 2% w/v BSA had not cracked at 60 days, whereas those prepared at 0.1% w/v had cracked-by 30 days), increase in ionic strength (emulsions prepared at an ionic strength of 1 mM had cracked by 60 days, whereas those prepared at an ionic strength of 10 mM had cracked by 90 days), and decrease in temperature (emulsions prepared at 37 and 60 degrees C had cracked by 5 days, whereas those prepared at 5 and 25 degrees C had not cracked at 60 days). There was no significant change in stability for emulsions prepared at pH 5.3 and pH 7.4. The addition of dextran sulfate improved emulsion stability, whereas the addition of acacia decreased stability. Emulsions prepared with BSA alone cracked by 90 days, those prepared with BSA and acacia cracked by 30 days, and those prepared with BSA and dextran sulfate had not cracked at 90 days. Interfacial properties were useful in predicting emulsion stability.

Drug Stability↗

PubMed1997

Preparation and stabilization of heparin/gelatin complex coacervate microcapsules.

The aims of this study are to optimize conditions for the preparation, stabilization, and harvesting of heparin/gelatin microcapsules prepared by complex coacervation. Microelectrophoresis and dry coacervate weight were used to determine the optimum conditions of pH and ionic strength for maximum heparin/gelatin coacervate yield. Heparin/gelatin microcapsules were formed by complex coacervation in the presence and absence of poly(1-vinyl-2-pyrrolidone) (PVP), which was used as a stabilizer. The microcapsules were collected using a spray-drying technique. Microcapsule particle size was analyzed using an AccuSizer optical sizer. Optimized conditions for maximum coacervate yield were pH 2.6, ionic strength 10 mM, and a 1:2 heparin/gelatin A ratio. PVP stabilized the heparin/gelatin coacervate droplets and reduced droplet aggregation during spray-drying. The mean particle diameter of the spray-dried coacervate droplets was lower in the presence of PVP and was unaffected by PVP concentration (in the range 0.5-2.0% w/w). Heparin/gelatin microcapsules, prepared under conditions optimized for maximum coacervate yield, were stabilized without the use of chemical cross-linking agents. Stabilization was achieved by a combination of the addition of PVP and spray-drying.

Drug Carriers↗

PubMed1997

Effect of cationic surfactant on transport of model drugs in emulsion systems.

Excess surfactant present in emulsions can influence the rates of transport of incorporated drugs by micellar solubilization, alteration of the partitioning process and by drug-surfactant complexation. Cetyltrimethylammonium bromide (CTAB), a cationic surfactant was selected to investigate these phenomena as it forms relatively stable mineral oil-water (O-W) emulsions and has the potential for ionic interaction. Phenylazoaniline, benzocaine, benzoic acid and phenol were chosen as model drugs for this study. The emulsion critical micelle concentration (CMC) for CTAB determined using a combination of a membrane equilibrium technique and surface-tension measurement was 1.0% w/v in 10% v/v% O-W emulsion systems. Ionic interaction between model drugs and surfactants and drug hydrophobicity affected their transport rates in the emulsion systems. The transport rates of the lipophilic drugs (benzocaine and phenylazoaniline) and the ionized hydrophillic drug (benzoic acid, pH 7.0) in the emulsion systems increased with increasing CTAB concentration up to 0.5% w/v micellar concentration and then decreased at higher concentrations. The rate of transport of phenol was not affected by the presence of micellar phase. Ionic interaction between surfactant and model drugs affected transport rates of model drugs in emulsion systems. The micellar phase was considered to affect the overall transport rates of model drugs.

Biological Transport↗

PubMed1996

Effect of nonionic surfactant on transport of model drugs in emulsions.

PURPOSE: To investigate the influence of excess surfactant on transport kinetics in emulsions, using phenylazoaniline (PAA), benzocaine, benzoic acid and phenol as model drugs. Mineral oil was chosen as the oil phase and the nonionic surfactant, polyoxyethylene oleyl ether (Brij 97) as the emulsifier. METHODS: Model drug transport in emulsions was investigated using side by side diffusion cells mounted with hydrophilic dialysis or hydrophobic membranes. A novel method, involving a combination of a membrane equilibrium technique and surface tension measurement (Wilhelmy plate method), was developed to determine surfactant critical micelle concentration (CMC) in the presence of O/W emulsions. Emulsion stability was determined by droplet size analysis as a function of time, temperature and dilution using photon correlation spectroscopy and a light blockage technique. Model drug mineral oil/water partition coefficients and aqueous solubilities were determined in the presence of surfactant. RESULTS: The emulsion CMC value was used to calculate micellar phase concentration. The transport rates of PAA and benzocaine in emulsions increased with increase in Brij 97 micellar concentrations up to 1.0% w/v and then decreased at higher surfactant concentrations. The transport rates of the more hydrophilic compounds, benzoic acid (ionized form, pH 7.0) and phenol, were not affected by the presence of micellar phase. CONCLUSIONS: Excess surfactant affected the transport rates of the model drugs in the emulsions depending on drug lipophilicity. Transport rates measured using side by side diffusion cells appeared to be governed by model drug partitioning rates from the oil to the continuous phases and by membrane type.

Benzoates↗

PubMed1996

Novel technology for the preparation of sterile alginate-poly-l-lysine microcapsules in a bioreactor.

The purpose of this study was to develop a method that may be suitable for the commercial manufacture of sterile alginate-polylysine-alginate microcapsules in a bioreactor. A Turbotak atomizing device in conjunction with a Bellco Bioreactor was used to prepare sterile microcapsules. Aseptic procedures were followed using sterilized equipment and materials. Sodium alginate solution was sprayed into calcium chloride solution using the Turbotak, with nitrogen as the atomizing gas. The resultant gelled alginate microcapsules were coated with polylysine and alginate to produce alginate-poly-l-lysine microcapsules. In-process contamination of the atomizing gas and microcapsules was investigated using modified USP sterility tests. Microcapsule size was determined using a light blockage technique (Accusizer) which measures both number and volume weighted mean diameters. The microcapsules prepared passed a modified USP sterility test, and the Bellco Bioreactor was found to minimize the possibilities of environmental contamination and therefore enhanced operator safety. The flow rate of the atomizing gas was determined to significantly alter number and volume weighted mean microcapsule diameters. Statistical analysis indicated that the number weighted mean diameters in conjunction with the volume weighted mean diameters can be used to detect batch-to-batch changes in microcapsule diameters. In conclusion, the modified Bellco Bioreactor offers a novel approach for producing sterile alginate-polylysine microcapsules on a laboratory scale.

Alginates↗