I have prepared some polymeric microspheres from chitosan and PCL. However while performing in vitro degradation study, I found difficulties in both above mentioned methods. Here I am mentioning one-by-one possible methods and their drawback I faced and will appreciate if anyone can give a better and doable solution for the below-mentioned methods?
1) By change in weight of microsphere:
Literature has told to take a certain amount of polymeric microspheres in a tube and incubate with different physiological solutions for a pre-determined period. Then to remove the microspheres from the tube, wash it with d.H2O and re-weigh it. Then to calculate the % of weight loss
(degradation)= Initial weight (W0)- weight at that time (Wt)/W0 X 100
The problem I faced: While washing the microspheres with water at a pre-determined period and centrifugation to settle all the microspheres as pellet and other buffers and water as supernatant, there is a chance of microsphere loss during discarding the supernatant of the washing step. You can't be careful enough because PCL is a hydrophobic polymer and it won't form sticky clot at the bottom of centrifuge tube after coming in contact with water. So, when the last portion of the supernatant is about to leave the tube mouth, it will carry some microspheres with it. So, thereby reducing the original weight of the test sample. So there is no meaning of doing a degradation study if I already got the Wt
For degradation study ,you must make a pellete of your powdered sample with 6mm diameter as per standard then you will do the degradation study
To overcome the limitations of traditional methods for measuring weight loss and size changes in your PCL microsphere degradation study, consider adopting alternative analytical techniques. Molecular weight analysis via GPC/SEC can reveal subtle changes in polymer chain scission. Thermal analysis methods such as DSC and TGA provide comprehensive data on thermal properties and degradation behavior. Spectroscopic techniques, including FTIR and NMR, are effective for monitoring chemical structure changes. Additionally, microscopy techniques like SEM and AFM offer detailed visualizations of surface morphology and structural alterations. These advanced methods collectively offer a more precise and comprehensive understanding of polymer degradation.
Two methods:
Do you have access to a particle size analyzer (for example Bettersizer)? This will give you average particle size and particle size distribution. This will provide information on how the distribution changes with time.
Alternatively, prepare the materials with incorporation of a dye molecule. As the micropspheres degrade, dye will be released. You can remove portions over time, centrifuge or filter to get rid of intact microspheres, then take UV-Vis to determine release.
