Wednesday, May 18, 2011

PolyVivo Emulsions


I performed a brief experiement on one of these which may be helpful to you. I dissolved AK09 (B#1) as 1% w/v in 50 ml water and emulsified with a homogenizer (IKA T25 Basic) with homogenization ~9000RPM I added 100ul of 10% PLGA (Resomer RG503H Boeinger Ingelheim) plus ~0.1% nile red dye (fluorescent tracer) dissolved in dichloromethane. I let this continue to homogenize for about 1 minute then pulled out. The 1% AK09 solution vissually forms bubbles (like soap water) and I pipetted a small amount of the solution out onto a microscope slide and imaged using a BX51(Olympus) microscope under TRITC fluorescence mode and obtained the attached picture. As you can see emulsion microparticles (little red droplets, in this case ~10-20um in size) can be obtained using AK09 via this method.

As for making microparticles there is going to be a wide range of sizes you can make based on homogenization speed (rule of thumb, faster is smaller but there is such thing as too fast), surfactant concentration, surfactant type (diblock and triblock copolymers will have different micelle sizes and these sizes will also depend on surfactant concentration), polymer solvent type (solvents interact differently with water and some prefer evaporation versus extraction). Inevitably with all emulsion type there will be a bit of loss as some polymer will ppt out to rapidly/slowly and not be microparticles but this method will generally yield a fair amount of microparticles. I encourage you to check out a paper where they make a couple of different PLGA microparticle sizes. Here they use traditional non-degradable surfactants but the concepts are still similar. (H. Jeffery, S.S. Davis, D.T. O'Hagan, The preparation and characterisation of poly(lactide-co-glycolide) microparticles. I: Oil-in-water emulsion solvent evaporation, International Journal of Pharmaceutics, Volume 77, Issues 2-3, 15 November 1991, Pages 169-175.) The primary advantage here is typically whatever surfactant you use will inevitibally end up adherent to the external part of your microparticle as it forms inside the micelle so with polyvivo surfactants you would theoretically end up with microparticles covered with with polyvivo polymer.

I would suggest preparing and using polyvivo surfactant solution pretty much immediately as you need it. If you can't use it soon store in a refrigerator but after a few days in water the properties may change some as the polyvivo degrades.
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