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.

KEYWORDS:

• bioremediation
• optimization
• PCL microparticles
• rhamnolipid biosurfactant

ACKNOWLEDGEMENTS

This research was supported by Florida A&M University Environmental Sciences Institute, Title III Programs and NOAA ECSC Grant No. NA17AE164.

Notes

^a FN = formulation number. Those highlighted in pink were chosen for further investigation.

^b VIP = volume of internal phase.

^c VEP = volume of external phase.

^d %Yield = 100 (c/a + b); where a = weight of PCL in mg used for preparation of the microparticles; b = weight of RhBS (present in internal phase of primary emulsion); c = weight in mg of microparticles obtained.

^e Mean ± SD.