I prepared a 1% PVA, and dissolved 500 mg of PCL in 5 ml of DCM. Then I introduced the PCL solution into PVA while stirring at 2000 rpm for 2 hours, after which i place it on magnetic stirrer to evaporate the DCM. But instead of having the microspheres in dispersed form they clump together only few microsphres form.
Dear Stella,
The fabrication of microspheres can be, more or less, complex !
To arrive to the final goals, we need to consider an important number of parameters : selection of polymer (PCL) of adequate molecular weights; specific (co)solvents or non-solvents, the choice of optimal viscosity of (PCL) solutions; typical emulsifiers/stabilisants and their percentage; parameters of processing (speed & time of emulsification, temperature, time, methods for the removing organic solvents, separation/purification, etc.).
Looking at your experimental conditions, it is not very clear what was the volume of “water” phase, i.e. of sol of 1% PVA. In the case of biopolyesters (PLA, PCL, etc.) in many, many cases it was experimentally perceived the aggregation of microspheres or microcapsules in the step of removing of solvents (here DCM). Please take in consideration that the aggregation of microspheres could be more frequent where we are using concentrated emulsions/dispersions, at long time for the evaporation of solvents and where the speed of mixing is not adequate, and so on…
Firstly, please verify if the dimension of “oil” droplets in your emulsion is OK (e.g., by optical microscopy). Based on my experience, I will suggest preparing the emulsion and then, to add it in a higher volume of demineralized /distilled water, while using a gentle stirring during the step of removing of solvents (DCM). In some conditions it's better to use higher temperature for the removing of DCM, in the idea to do shorter the process. It is also possible to use more diluted solutions of PCL in DCM…
Good luck in your R&D works and best regards,
Marius
PS: For eventual help:
http://oaji.net/pdf.html?n=2017/5165-1500287063.pdf
https://onlinelibrary.wiley.com/doi/pdf/10.1002/jps.22777
https://www.researchgate.net/publication/257414873_Drug_release_system_of_ibuprofen_in_PCL-microspheres
https://www.tandfonline.com/doi/full/10.1080/02786826.2016.1234707
https://doi.org/10.4028/www.scientific.net/AMM.695.191
Dear Marius,
thank you for your suggestions, in fact I have applied some of them and i 'm getting improved result from what i had earlier. I believe with time it will become perfect.
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