Dear all,
I'm planning to transform Tetrahymena termophila with a plasmid, contaning GFP driven by a cadmium chloride inducible promoter.
As cadmium chloride is super toxic, mutagenic and a lot of other nasty things, I'm a bit worried about the disposal.
It is totally clear for me to dispose it in the heavy metal waste, I'll have to sterilize the culture first, because it's genetically modified.
For sterilization I see two options:
Autoclaving: This would be my methode of choice, but I'm concerned about the toxic fumes, which come along with that. So autoclaving is not an option.
Sodium hypochloride: This would be my other option. But does anyone know if the sodium hypochloride is able to react with the cadmium chloride and as well produce toxic fumes?
If anyone as an idea, I would be super grateful!
Cheers
According to toxicology literature, chelating agents like thiols (including cysteine, NAC [N-acetyl-cysteine, a cheap antioxidant] can help "remove" Cd (by binding it in aqueous solutions). However, being highly solubles, such agents are not going to be helpful.
In chemical systems, Cd2+ can react with thiourea (which is cheap) in the presence of NH3 (ammonia) to give the insoluble CdS (yellow ppt), yielding urea as a byproduct.
Therefore in theory, by supplying excess thiourea (which is also an antioxidant of sorts), you can isolate and concentrate aqueous Cd as a solid, and then carefully dispose it somewhere in a proper container.
http://www.hindawi.com/journals/tswj/2013/219840/
https://en.wikipedia.org/wiki/Cadmium_sulfide
Be careful that acidic conditions (see Wiki) promotes CdS dissolution. So will NH4OH (slightly).
Maybe put the solution through a 0.2 micron filter? The flow through would go in heavy metal waste. The filter would go to solid biohazardous waste.
What concentration are we talking about?
I would autoclave. Probably your exposure levels while handling the Cd powder, stocks or the complete medium are way higher than what you would get in the autoclave. By the way, what fumes? Also, if your media contains phosphates, the Cd will precipitate as soon as the autoclave warms up.
Heavy metals usually promote the decomposition of hypochlorite producing toxic fumes, so I would avoid it
After autoclaving or whatever method you use, you have to acid-wash your containers to remove remaining Cd. That's standard procedure when working with heavy metals. Also, if you decide to use hypochlorite, you need to rinse with water to remove any remaining bleach before adding any acid.
It's not much, around 10ug/ml, so in a ml culutre it would me 1mg. But anyway it's still tocix. I just don't want to risk anything.
I think I'll go with the idea Govinda had. I was thinkig about the same yesterday evening. It propaly will be the easiest and saftiest way to do it.
Thank you all very much!
Well, that's a concentration of 10ppm, which is quite high compared to maximum allowed values in drinking water (2000 times more).
In any case, at that concentration you should be able to use bleach. Just be careful not to mix it with acid waste (usual the heavy metal liquid waste is)
And btw, is it acceptable to eliminate a GMO by filtration?
I would check the regulations.Nonetheless, some of the Cd will be adsorbed to the biomass and technically more dangerous in terms of exposure to Cd: more equipment in contact with the solution, manipulation of the wet filter... and you need to decontaminate any glassware that has been in contact.
That's good to know! In my idea I would filter the medium and later autoclave the filters, but aso you say some of it may remain in the organisms. So thats probably as well not the best idea.
But if i safely can use bleach, that it shouldn't be a problem.
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