Michael Abazinge

Comparison of In Vitro and In Vivo Release Characteristics of Sustained Release Ofloxacin Microspheres

The sustained release nature of ofloxacin microspheres--to eradicate bacterial biofilm associated with chronic infections from sensitive strains of bacteria--was determined both in vitro and in vivo. Ofloxacin microspheres were prepared by emulsion solvent evaporation procedure using poly(glycolic acid-co-dl-lactic acid) (PLGA) as the biodegradable polymer. The microspheres were characterized by scanning electron microscopy, in vitro release in an incubator, and in vivo release in the rat subcutaneous model. The microspheres were highly spherical with a very smooth surface. Approximately 45% of the drug was released from microspheres in sizes of 125-250 microns and 250-425 microns in 2 days compared with approximately 22% from microspheres of size range 37-125 microns indicating that surface area of the microspheres did not control the kinetics of in vitro release. However, about 96% of the drug was released from the three different size ranges in 35 days. The in vitro release profile of microspheres of size range 125-250 microns is not significantly different from microspheres in sizes of 250-425 microns. The peak plasma level of ofloxacin in animals that received the drug suspension occurred within 2 hr and was higher than that of the microspheres that occurred by the end of the second day. The plasma of animals that received the free drug was depleted of ofloxacin by the end of the first day, but the drug was sustained above 0.5 microgram/mL in the plasma of animals that received the microspheres for about 3 weeks. The results suggest that biodegradable ofloxacin microspheres can be prepared that release the antibiotic in vivo for about 3 weeks. This should provide a means for continuous treatment of chronic infections in which bacterial biofilm can occur.The sustained release nature of ofloxacin microspheres - to eradicate bacterial biofilm associated with chronic infections from sensitive strains of bacteria - was determined both in vitro and in vivo. Ofloxacin microspheres were prepared by emulsion solvent evaporation procedure using poly(glycolic acid-co-dl-lactic acid) (PLGA) as the biodegradable polymer. The microspheres were characterized by scanning electron microscopy, in vitro release in an incubator, and in vivo release in the rat subcutaneous model. The microspheres were highly spherical with a very smooth surface. Approximately 45% of the drug was released from microspheres in sizes of 125-250 mum and 250-425 mum in 2 days compared with 22% from microspheres of size range 37-125 mum indicating that surface area of the microspheres did not control the kinetics of in vitro release. However, about 96% of the drug was released from the three different size ranges in 35 days. The in vitro release profile of microspheres of size range 125-250 mum is not significantly different from microspheres in sizes of 250-425 mum. The peak plasma level of ofloxacin in animals that received the drug suspension occurred within 2 hr and was higher than that of the microspheres that occurred by the end of the second day. The plasma of animals that received the free drug was depleted of ofloxacin by the end of the first day, but the drug was sustained above 0.5 mug/mL in the plasma of animals that received the microspheres for about 3 weeks. The results suggest that biodegradable ofloxacin microspheres can be prepared that release the antibiotic in vivo for about 3 weeks. This should provide a means for continuous treatment of chronic infections in which bacterial biofilm can occur.

In vitro and in vivo characterization of biodegradable enoxacin microspheres

The in vitro release and plasma concentration profiles of sustained release enoxacin microspheres intended for the treatment of bone and systemic infections due to sensitive strains of bacteria were investigated. Microspheres of enoxacin were prepared by using poly(glycolic acid-co-DL-lactic acid) (PLGA) by the emulsion solvent evaporation technique and characterized by in vitro release in an incubator, and in vivo release in the rat subcutaneous model. The microspheres were spherical in nature, and particle size range had a significant influence on the in vitro release. The enoxacin plasma concentration 2 h after the administration of treatments was two-fold higher in animals who received the free drug compared with those who received microspheres of size range 125-250 microm. The plasma of animals who received the free drug was depleted of enoxacin by the end of the first day. However, the plasma concentration of enoxacin in the animals who received microspheres was sustained above 0.5 microg/ml for about 8 days. The results show that biodegradable microspheres of enoxacin can be prepared which release the antibiotic in vivo for days following a subcutaneous administration. This should provide a means for the sustained treatment of infections due to sensitive strains of bacteria.

Morphology and Release Profiles of Biodegradable Microparticles Containing Rhamnolipid Biosurfactant

ABSTRACT In an effort to expand the technology of bioremediation of hydrophobic organic compounds, microencapsulation technology was investigated as a method of biosurfactant delivery to contaminated sites. Microparticles are composed of active or inactive materials encapsulated in a polymer coating designed for controlled release of the encapsulated substance. Surface morphology and release profiles of microparticles containing rhamnolipid biosurfactant were investigated for development of a controlled release bioremediation scheme. The evaluation was conducted under laboratory conditions with 45 mg/ml concentration of biosurfactant and a representative environmental medium; using artificial salt water (35 ppt) and deionized water medium as a control. The microparticles were prepared by the water–in–oil–in–water double emulsion solvent evaporation method. The surface morphology was examined after initial preparation, at 0, 15 and 31 days incubation, using light microscopy. Light microscopic images revealed smooth, spherical microparticles that degraded over time in the media. Results indicated that microparticle degradation occurred mostly in the salt water environment, suggesting that the presence of salts (Na+ and Cl− ions) in the water enhanced microparticle degradation. The deionized water environment achieved polymeric degradation that was similar to what was generally reported in the literature. Biosurfactant release was evaluated for polymer molecular weights (Mw) 40, 80, and 200 kDa, in salt water and deionized water media, each of which showed a high initial burst release of biosurfactant, followed by pulse releases that occurred over the 31 day period. The highest level of biosurfactant release of all the molecular weights tested occurred in the Mw 80 kDa. The release from Mw 40 kDa and Mw 200 kDa was not significantly different (P > 0.05). The results showed that this technology may be useful for enhancing bioremediation of residual hydrophobic organic contaminants (HOC) in estuarine and marine environments.

Phenanthrene Emulsification and Biodegradation Using Rhamnolipid Biosurfactants and Acinetobacter calcoaceticus In Vitro

ABSTRACT The ability of biosurfactants and Acinetobacter calcoaceticus to enhance the emulsification and biodegradation of phenanthrene was investigated. Phenanthrene is a polycyclic aromatic hydrocarbon that may be derived from various sources, for example incomplete combustion of petroleum fuel, and thus it occurs ubiquitously throughout the environment. In order to assess the efficacy of a biosurfactant microparticle system, emulsification assays and in vitro biodegradation studies were conducted. Emulsification assays were carried out to assess the stability of phenanthrene emulsions. Emulsion stability was determined by the height of the emulsion layer (Emulsification Index) and turbidity. In vitro biodegradation tests were done to estimate phenanthrene degradation from an aqueous system by A. calcoaceticus supplemented with encapsulated (ERhBS) and nonencapsulated biosurfactants (NERhBS). Results show that phenanthrene emulsifications were stabilized after 48 h with NERhBS and remained stable for 72 additional hours. Phenanthrene emulsifications were stabilized with ERhBS after 216 h and remained stable for an additional 96 h. A. calcoaceticus alone and supplemented with rhamnolipid biosurfactant were able to biodegrade 10 to 50 mg L−1 of phenanthrene within 250 h. When supplemented with NERhBS, A. calcoaceticus degraded phenanthrene significantly faster than when nonsupplemented or supplemented with ERhBS. Addition of exogenous biosurfactants was considered to be a major factor driving the direct correlation between decreasing phenanthrene concentration in the system and increasing bacterial biomass.

Poly ε -Caprolactone Microparticles Containing Biosurfactants: Optimization of Formulation Factors

ABSTRACT The objective of this research was to optimize the formulation factors and evaluate the release profiles of ϵ -polycaprolactone microparticles containing rhamnolipid biosurfactant (RhBS). Microparticles were prepared by a water-in-oil-in-water emulsion solvent evaporation technique. Optimization was studied through the effects of the volumes and concentrations of the internal and external phases of the microparticles on percent yield, particle size, encapsulation efficiency, and biosurfactant loading. Manipulation of the formulation factors yielded microparticles that were statistically the same size and generally classified as small. An increase in the volume of the internal phase above 1 ml caused a general decrease in yield and encapsulation efficiency and an increase in biosurfactant loading. When the volume of the external phase increased above 50 ml, decreases in percent yield and encapsulation efficiency and increases in biosurfactant loading were observed. Formulations with the highest encapsulation efficiencies and percentage yield and the lowest biosurfactant loading efficiencies were selected for further evaluation in release studies. Release studies were conducted in 15 and 32 ppt artificial seawater and deionized water. After 30 days microparticle formulations gradually released 80% to 100% of the encapsulated RhBS in all release media, with no significant differences in release rates in the different release media.

Use of Chicken Manure Extract for Biostimulation and Enhancement of Perchlorate Rhizodegradation in Soil and Water Media

ABSTRACT The influence of biostimulation using dissolved organic carbon (DOC) on rhizodegradation of perchlorate and plant uptake was studied under greenhouse conditions using soil and hydroponic bioreactors. One set of bioreactors planted with willow (Salix babylonica) plants was spiked with 300 mg L−1 DOC in the form of chicken manure extract, whereas a second set was not treated with DOC. A similar experiment without willow plants was run in parallel to the planted bioreactors. The planted soil bioreactors amended with DOC reduced perchlorate from 65.85 to 2.67 mg L−1 in 21 days for humic soil (95.95% removal) and from 68.99 to 0.06 mg L− 1 for sandy loam (99.91% removal) in 11 days. Nonplanted DOC treated soil bioreactors achieved complete perchlorate removal in 6 and 8 days for humic and sandy loam, respectively. Both planted and nonplanted soil bioreactors without DOC removed > 95% perchlorate within 8 days. Planted soil bioreactors respiked with perchlorate reduced perchlorate to nondetectable levels in 6 days. Hydroponics experiment amended with DOC reduced perchlorate from approximately 100 mg L− 1 to nondetectable levels within 7 to 9 days. Hydroponic bioreactors without DOC had low perchlorate removal rates, achieving 30% removal in 42 days. Leaf samples from sandy loam soil bioreactors without DOC had four times perchlorate phytoaccumulation than the DOC-treated plants. Similar results were obtained with the nonplanted bioreactors. Persistence of perchlorate in solution of planted hydroponic bioreactors without DOC amendment suggested that natural DOC from the plant exudates was not enough to biostimulate perchlorate reducing microbes. The hydroponic bioreactor study provided evidence that DOC is a limiting factor in the rhizodegradation of perchlorate.