Most of the drugs are been delivered in DMSO as the carrier molecule. We all know that high DMSO concentrations may cause cytotoxicity. But does the rate of diffusion of DMSO (along with the drug) in cell culture medium also depend upon such factors as: 1. Speed of addition of drug, 2. Temperature of the medium, 3. Temperature of DMSO, 4. The location in the well where the drug is been actually dropped (along the sides or in the center)? If any or all of the above control the uptake of drug in DMSO by the cell line, then can someone explain to me how?
Dear Neha, since drug diffusion would propagate in radial direction, from purely mass transfer point of view starting from the center, it would have the most possible distribution pattern. In any case, It will certainly affect in the beginning more the cells in the center, but as Adam has pointed out very correctly, if the timescale at which you are looking for the effect is much longer than the timescale for diffusion, this point will become irrelevant!
First, I would refer to DMSO as a solvent and not as a "carrier molecule" - these are very different things... As to the diffusion of DMSO in a culture medium: certainly its rate will depend on temperature (faster at a higher temperature) and on the viscosity of the culture medium (slower diffusion if the viscosity is higher). As to the speed of drug addition and location: the best will be to use always the same speed and add in the center of the well in order to provide a more uniform distribution.
From the physical pont of view, you should also take into consideration external fields aciting on a system (take a closer look on Navier-Stokes eqations,), and chemical reactivity of a drug. The transport process should be extended from a single diffusion model - advection (N-S eq), adsorption and reactivity (depending on temperature and light exposition) are also important!.
For diffusion in vitro I would follow the direction that Pawel has indicated. In encapsulated cells diffusion is in the order of milliseconds to achieve equilibration. In tissues it takes minutes to achieve ~90% equilibration. If you need references search for publications including either Professor Sambanis or Professor Carpenter.
Svetlozar Velizarov....thanks for the correction. if i add the drug in the center of the well then would it not immediately affect the cells at the center ?
Dear Neha, since drug diffusion would propagate in radial direction, from purely mass transfer point of view starting from the center, it would have the most possible distribution pattern. In any case, It will certainly affect in the beginning more the cells in the center, but as Adam has pointed out very correctly, if the timescale at which you are looking for the effect is much longer than the timescale for diffusion, this point will become irrelevant!
Svetlozar and Adam..thanx for your inputs . I am looking for the effects generally after 72 hrs , when the drug is added at 6, 24, 48 hrs.
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