I have a query to ask. I have synthesized two types of mesoporous silica nanoparticles with same pore size and loaded them with drugs. But to my amazement, drug loading was MORE in the one with LESS total surface area and less in the one with higher surface area. Another thing that happened is while doing drug release, the release was faster from the one with less drug loaded particle (when calculated in percent terms), what could possibly be the reason for it? Could it be the channel length or wall thickness issue?
Any help will be highly appreciated.
Thanks. :)
Hi Wei,
I synthesized sba 15 and kit 6, size unknown but surface area of sba was 100m2 more than kit, yes loading was done more than 3 times and yes I did Calcine them.
Hi Wei.
I assume you are loading the drug into the pores by imbibing drug solutions, then evaporating the solvent. If that is the case, there are a few things to consider that might help (hopefully, assuming you haven't considered them already).
First, make sure there is little or no drug on the outer surfaces of the silica particles (outside, rather than in the pores). Drug on the outer surface can pose a potential problem, especially if you are trying to supersaturate. While the drug in the pores must dissolve before diffusing out of the pores and into the bulk receiving medium, anything on the surface may not fully dissolve, especially as the bulk concentration approaches the drug solubility, and may actually act as precipitation sites to hinder supersaturation. (if that is your goal).
This can also affect your determined loading efficiency... any drug in the form of particles on the surface will show up in extractions. Make sure you know what is in the pore vs. not in the pore. If you have equipment, porosimetry before and after loading is the best way. DSC can also help somewhat 9but is not as definitive), since entrapped particles often show a broad endotherm below the nominal melting temp of the pure drug (as opposed to a sharp melting peak for pure crystalline forms). The problem is that the DSC is not quantitatively accurate enough to characterize the amount of drug in the pores. (Also, if there is residual solvent, that can affect the DSC.)
Second, if the silica with higher surface area also contains smaller pores, the ability of the liquid to enter the pores may change. Again, this may translate into more drug on the particle surface (inter-granular spaces), which could poison supersaturations during dissolution experiments.
I hope this helps. Good luck!
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