I am trying to prepare polymeric microcapsules via. a W/O/O emulsion synthesis process. So my technique essentially begins with formation of a W/O1 emulsion system formed by homogenization where the O1 phase is DCM (dichloromethane) in which the polymer PCL(polycaprolactone) is dissolved. A low HLB value surfactant is being used for the synthesis of this system to give water in oil droplet configuration.
Then this system is being put into another O2 phase essentially silicone oil with addition of a high HLB value surfactant and homogenized to form a W/O1/O2 assembly. So the idea is the DCM would eventually evaporate and lead to formation of polymeric spheres (particles) encapsulating the water moeity inside and these spheres remain suspended in the silicone oil phase. (The turbid appearance of the system is a manifestation of these freely suspended particles, which is otherwise clear).
Post synthesis, we try to wash these particles with suitable solvent to remove the silicone oil and collect these particles by centrifugation or other separation technique like filtration. But the particles stick to each other and form a paste kind of substance. After that, on trying to disperse the particles in an aqueous phase they don't disperse into finer particles as they were once in the silicone oil system and hence our particle analysis are way off from the expected values. So how can I overcome this problem. Is there a need to alter my selection of surfactants/reagents or is it the procedure that requires any modification?
why you do not use w/o/w emulsion to get the particles dispersed in water after DCM evaporation?
W/O1/O2 or W/O emulsion as the continuous phase you've is "Oily Phase" In this case, I suggest you adding a blend of surfactants, one with high HLB and another one with low HLB. The choice of surfactants will be according to their HLBs which should be calculated. On the other hand, you can use in addition to the blend of 2 surfactants, one more surfactant with low HLB too. Take into your consideration, the method of preparation of multiple emulsion.
Good Luck!
I do not believe the problem is surfactant system, rather the silicon oil which is difficutlt or not possible to remove fully.
but there're many emulsion systems containing silicone oil or its derivatives such as dimethicone or simethicone. I think the problem is in the choice of surfactants and the method of preparation (the sequence of addition). He also should take into his consideration the calculation of the required HLB of a blend of ingredients to be emuslified and HLB of the emulsifiers.
Thanks to Dr.Sobisch and Ahmed for your respective inputs. Firstly to Dr. Sobisch query of why not using W/O/W method- well I am actually trying to synthesize polymeric drug carriers using emulsification technique and literature shows that the initial "burst release" of carriers synthesized via. W/O/W is higher as compared to that of W/O/O which is undesirable and hence the choice. And yes silicone oil is a problem, but people have reported that proper washing with PET ether etc. removes it.
Secondly to Ahmed, I am using Span80 (HLB~4) in my first emulsion phase, and Tween80 (HLB~15) for the second emulsion phases, both non-ionic surfactants just to be safe with not altering/denaturing the drug/protein being encapsulated. Also I have to make these particles as small as possible, so don't want to go for Pluronics etc. And since ionic surfactant is not an option for oil in oil dispersion, which surfactant/combination of surfactants (non-ionoic), can give me a good result? Can you give me a particular name, besides the HLB value.
Once again, thanks for your help!!
- Badges
- Science topic
- Similar topics
- Chemistry, Organic
- Organic