Based on the data reported in many publications mentioning the drug loading of mesoporous silica nanoparticles (MSNs) since the drug precipitate as a crystalline form and requires separation. That was so confusing, and I want to discuss if this test is an actual test or a myth.
We have here a three mentioned scenarios
1- Measuring drug loading without washing MSNs after solvent evaporation or deposition or incipient witness method. So, why we measure drug loading, actually the drug loading efficiency should be 100%, and if there is a decrease in the drug content, that means only one thing "the preparation method was messy or inadequate preparation."
2- Measuring drug loading after washing with ethanol is inaccurate because ethanol will dissolve depending on drug solubility. Also, ethanol can dissolve amorphous and crystalline drugs, so there is no preferential separation.
3- Measuring drug loading after washing with water or water containing a minimum amount of ethanol. In this method, the drug is dissolved to the limit of drug solubility in water or the water-ethanol mixture.
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-What is useful to do with crystalline form is to measure the degree of crystallinity in loaded mesoporous silica.
-If there is a washing method you can suggest to separate crystalline form efficiently out of the loaded carrier, please discuss it.
Who said it ?
You need some other stable structural configuration!
Raman Micro-analysis is one, ()probably only one in your case(), of the best techniques to identify drug substance, as pesented in any of the input crystalline or amorphous form, or converted different polymorphic, hydrate or solvate forms, or salts and co-crystals, from local excipient carriers.
In your case, Raman response of silica is very weak, close to almost indetectable. This makes separating drug substance from its carrier easier-no cross comtanmination. However, mesoporous structure of silica would make measuring those drug substance a bit more difficult with good S/N ratio-DS inside pores, subject to the Raman response of drug substance. In summry, it is feasible to measure drug load in carriers.
Raman is an alternative characterization technique similar to DSC and XRD in testing crystallinity. Herein, I am arguing that washing is an actual method to separate the crystalline drug physically from the surface of MSNs for further testing as dissolution.
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