Natalia concentration is about right. Beyond 0.5% DMSO, the DMSO begins to become toxic to the system because, as Adam points out it very easily penetrates barriers. Both the benefit and the problem to that is when it penetrates that barrier, it carries most everything with it.

Yi Xu's suggestion is a good one because you can now store you stock material in a -80 freezer and maintain integrity of the original materials. I'd aliquote it out, however into manageable volumes (e.g., 1 ml).

Please take Adam's warning very seriously. I was labeling live Human Blood Platelets with tritium to see if I could both keep the cells alive so they would aggregate normally, etc. I wanted to look at the Integrin (where the glycolytic tree was H3 labeled) binding with gel Electrophoresis. I was handling a high concentration solution of DMSO containing PPO (PolyPhenylOxizole), the fluorphore scintilant used in many of the radionuclide detection systems years back, to detect my proteins with gel Electrophoresis and subsequent autoradiography. Knowing the risks posed by DMSO, I was double gloved and everything, being certain not to be sloppy in any way, and there was a pin hole leak in my gloves. I found myself  dealing with systemic PPO exposure and needed to call the poison control hotline.

So while DMSO has some wonderful properties, please be very careful. Okay? People don't generally tell you stories like this because they are not making and using high concentrations. Also be ware that, since the colligative properties of DMSO vary significantly from water, pipetting accurate volumes is an issue at high concentration.

Hi Ellie, usually,  I make stock with high concentration using DMSO, and dilute them with water before infiltration into plant. Hope it is helpful for you. In addition, it depends on what chemicals you use?

DMSO is quite toxic easily penetrating human skin. usually less than 2% of DMSO should be used in cell assay.

I use a final volume of 0,2% of DMSO in cell cultures assay. This concentration is not toxic to the cells.

Natalia concentration is about right. Beyond 0.5% DMSO, the DMSO begins to become toxic to the system because, as Adam points out it very easily penetrates barriers. Both the benefit and the problem to that is when it penetrates that barrier, it carries most everything with it.

Yi Xu's suggestion is a good one because you can now store you stock material in a -80 freezer and maintain integrity of the original materials. I'd aliquote it out, however into manageable volumes (e.g., 1 ml).

Please take Adam's warning very seriously. I was labeling live Human Blood Platelets with tritium to see if I could both keep the cells alive so they would aggregate normally, etc. I wanted to look at the Integrin (where the glycolytic tree was H3 labeled) binding with gel Electrophoresis. I was handling a high concentration solution of DMSO containing PPO (PolyPhenylOxizole), the fluorphore scintilant used in many of the radionuclide detection systems years back, to detect my proteins with gel Electrophoresis and subsequent autoradiography. Knowing the risks posed by DMSO, I was double gloved and everything, being certain not to be sloppy in any way, and there was a pin hole leak in my gloves. I found myself  dealing with systemic PPO exposure and needed to call the poison control hotline.

So while DMSO has some wonderful properties, please be very careful. Okay? People don't generally tell you stories like this because they are not making and using high concentrations. Also be ware that, since the colligative properties of DMSO vary significantly from water, pipetting accurate volumes is an issue at high concentration.

0.5% DMSO may not be toxic to cells.

I attached a paper where the authors look at the mechanism of action of DMSO at various concentrations. It was a pretty interesting read, hope it helps!

I attach some additional papers along with some (possibly incoherent) comments specific to the three questions.

http://www.epa.gov/opprd001/inerts/dimethyl.pdf

http://biopublisher.ca/html-760-24-ijmvr

Although DMSO has been used for many years, it is one of the least understood chemicals that has been used in pharmaceuticals. There are many opinions floating around the web about DMSO and even some FDA conspiracy theories. With all of the misinformation that is available, it can be hard to make good decisions about the use of DMSO.

In question one, you ask about the amount or concentration of DMSO that is safe to apply topically. I take this as though you plan to apply it to skin. This is a tricky question since DMSO acts as a permeabilizing agent and it's potential danger to the health of the subject to which it is applied is highly dependent upon the other chemicals present before, during, and after the time of application. DMSO itself does pose a certain health hazard since it disrupts lipid membranes and denatures proteins. But it also allows many other chemicals to pass through the stratum corneum that are very dangerous once they get across. This results in this question being nearly impossible to answer in a general way. But if you look at literature where DMSO is used for transdermal drug delivery, up to 5% is pretty common and THE FDA has approved a bladder treatment that is 50% DMSO. Personally, I'd recommend starting with a low concentration (say 2%) and working it up only if necessary. Of course, my recommendation is as arbitrary as they come and you should do thorough research of your own before making this decision. Don't make it lightly.

In question two, you ask about the other liquids that could be mixed with DMSO. Water is a good one. In fact, if you leave your DMSO exposed to air for very long, it will become ~67% DMSO with the balance being water adsorbed from the atmosphere. This reaction is exothermic, so if you apply very concentrated DMSO directly to your skin, you will feel a warming sensation. Also, water is definitely not toxic, so it is probably the best choice.

In question three, you ask about it getting watered down. Yes, it will get watered down which is exactly what you want. The capacity of the DMSO to move other chemicals through the stratus corneum will still be there but without causing irreversible tissue disorganization or excessive protein denaturation. I don't think other “carrier chemicals” will be necessary. You may want to add something to make the solution into a gel or other thixotropic solution. Emu oil may be okay since it's just fatty acids, but I would not recommend jojoba oil since it contains erucic acid, which is known to cause cardiac damage when taken by mouth (it does not normally cross the stratum corneum but will when mixed with DMSO). Remember, anything you put with the DMSO may as well be injected directly into your blood and or subcutaneously. Selection of the chemistry you use must be done carefully (even your plant extract could be dangerous). Permanent disability or death could be the result of using the wrong chemistry, not necessarily directly from the DMSO.

Best Regards!

I have used 10% concentration of DMSO for cell culture works. They have not been found to be lethal for the cells so far. But they are readily absorbed by the skin and may cause headache, itching or burning.

Good luck.

Hero, is a fortunate man...Ron Reiserer is right on the money with respect to DMSO. It likely one of the most useful and, yet, potentially dangerous compounds around. One must understand, this solvent is equally misable with water at any concentration based on its polarity while still being an Organic solvent. As Ron said, there is an incredible history to DMSO. Many years ago, this solvent was used to treat arthritis which was just known to be knee pain or elbow pain. The doc would rub it in...don't know if there was some kind of linament oil along with it and you felt better...and your breathe smells and tastes like licorice...that's how I knew I was contaminated with the DMSO as related in an earlier response... Some 20 years ago, there was a slight resurgence in using this compound for these reasons until folks realized the properties of DMSO as a 'fits all' solvent. Hence, you're using it for a stock solution at 100x or more. Because you can!

We all remember those early chemistry lessons that told us that like dissolves like. In this case, most everything is soluble in DMSO to include many, many fully non-polar molecules....since many of them have at least partial molar charges on their surfaces. What this means is, as long as your vial is absolutely uncontaminated and cannot 'leach' molecules from the vial it is stored in...hence, we store high concentration DMSO preps in brown glass vials. Then your solute must also be absolutely pure with chiral contaminants which could affect a very serious negative physiological response.

Nothing we do in science is "pure" save for Mathematics and even that isn't pure. As such, with our DMSO stock, we try to make as high a concentration of the stock and then aliquote it out so you are not opening and closing vial lids. Given that contaminant levels are generally constant, preparing a 100-250 X stock concentration allows you to get your small molecule concentration into you sample cocktail at 0.2% or lower in the DMSO solvent...consider that water is 55.5 Molar... without any adverse effects on your physiological system.

I had no trouble using it at high concentration. The caution, as stated above, is to be exceedingly cautious when adding your ligand to you experimental samples. Often times we generally don't take stock of the solvent concentrations when doing an experiment. Here is a situation where you must, and to your advantage, you can make high stock solutions which are stored.

Opinions vary about acceptable concentrations. What is most apparent is that what is considered acceptable is entirely circumstantial, rather than global.

The oploaded document may be helpful in your considerations.