in vivo chemistry

Cytotoxic Gold Nanoparticles

In a new AOP from Nature Chemistry, Vincent Rotello’s group report a new way of killing cells. There system uses gold nanoparticles (AuNPs) as the core, and attached to the core is a diaminohexane group. The diaminohexane fragment is sheathed from the cell by cucurbit[7]uril (CB[7]).

Once the AuNPs enter the cell they can be triggered to expose its cytotoxic diaminohexane appendages by introducing 1-adamantylamine (ADA); ADA outcompetes the diaminohexane for CB[7].

The paper shows some very nice chemistry and it does a nice job selling the point that their gold nanoparticles are toxic to cells. However, I am worried when they say they are “exploring this strategy in vivo…” as the current generation of their system seems indiscriminate. But, I always enjoy being proven wrong.

Link to paper: Recognition-mediated activation of therapeutic gold nanoparticles inside living cells
Other recent papers by Vincent Rotello

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By October 13, 2010 4 comments in vivo chemistry

Why is High Fructose Corn Syrup so bad for you?

Is high fructose good for you or bad for you?

How many of you said bad?  Leads to obesity, right?  Gotta stay away from HFCS, right? That’s what ‘everyone’ says, right?

Consider: The sugar we call ‘table sugar’ is sucrose: a disaccharide: a molecule of glucose and a molecule of fructose (two monosaccharides) covalently bonded to each other.  Sucrose is broken into fructose and glucose by enzymes within living organisms (like humans).  Humans don’t use sucrose for energy, first we break it into glucose and fructose and metabolize the monosaccharides for energy.  So we ingest sucrose, digest it to glucose and fructose, then use the monosaccharides for energy.

One molecule of sucrose becomes 1 molecule of glucose and 1 molecule of fructose.  That means that sucrose is digested to a 50/50 mixture of fructose and glucose.

Consider: High fructose corn syrup is a straight mixture of unbonded glucose and fructose.  There are two common types of HFCS: HFCS 55 and HFCS 42.  HFCS 55 is ~55% fructose and ~42% glucose.  HFCS 42 is ~42% fructose and ~53% glucose.

So what’s the difference?

Sucrose becomes a 50/50 mixture of fructose and glucose.  HFCS 55 is a 55/42 mixture of fructose and glucose.  Chemically, there’s no difference between fructose from sucrose and fructose from HFCS.  Our bodies can’t tell the difference between fructose from sucrose or fructose from HFCS.  We’ve been fretting so much about a 5% difference between the fructose content in the two sweeteners.

If our body can’t tell the difference, and the percent content of fructose is essentially the same, why is HFCS so much worse for us than ‘natural,’ or ‘organic’ sugar?

It’s not.

HFCS is no worse for us, and causes no more obesity than table sugar.  Once ingested, table sugar and HFCS are metabolized by our bodies in exactly the same way.

So what’s the problem?  Well, the problem is sugars (both sucrose and HFCS) are in EVERYTHING.  Too much sugar (again, either from sucrose or from HFCS) IS bad for us, and will lead to higher caloric intake, and eventually weight gain.  So the problem is too much sugar – not too much HFCS, and the solution is to eat less sugars overall – not to ban HFCS from everything.

But that’s not what ‘everyone’ is saying.  And the court of public opinion can be quite harsh.  So harsh, in fact, that the HFCS manufacturers are attempting to rebrand.  No longer will we find HFCS on the ingredient list.  Now, we will see ‘Corn Sugar.’  This means the same thing.  It’s the same 55/43 mixture of fructose to glucose, but they’re rebranding to move away from the negative associations.

What do you think?  Good idea or bad idea?  Should we just ban HFCS/Corn Sugar?  Should we regulate the amount of sweetener that’s allowed to be in a Suggested Serving Size?  Do you agree with the decision by the HFCS manufacturers?

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By September 14, 2010 39 comments in vivo chemistry, science news

A Chemist Doing Biology

My postdoctoral research has just begun (started 1.5 months ago) and it will heavily rely on using mice. Thus far I have imaged, dissected, injected, xenografted, castrated, you name it and I’ve already done it or will be doing it to mice. As chemists we are sheltered from the bloody side of science. Sure some chemists on the biological side may have done cell culture or a gel here and there, but most chemists don’t handle things that bite you while your injecting the nanoparticles you made to monitor the progress of the cancer you gave them weeks earlier. Because of this I will be making a series of posts tagged a Chemist Doing Biology chronicling my adventures into Biology.

Brief background: I am a Chemist not a Biologist, my PhD was equal measures of nuclear/radio-chemistry, materials chemistry, organic synthesis, and electronic circuit design (sigh). My new research group is all chemists even though we are in the Pharmacology department. My first task in the group, take the graduate student’s Gd-encapsulated nanoparticles and inject them into mice. Then extract the lymph nodes and get ICP-AES data. A daunting task for a chemist to accomplish, especially with no biologists in the group or anyone having in vivo experience.

Fortunately, I found a happy biology graduate student willing to take her research time to teach me how to do the injection/dissection of the poor mice. When the day arrives, the chemistry graduate student and I whisk the biologist down to the animal cages. We gown up, bring our nanoparticles and chemical reagents in a box, we show the biologist the mice and proceed to the procedure room. We give the mice anesthesia, hand the biologist our nanoparticles and hope for the best. It is at this moment where the disconnect between hardcore Biologists and hardcore Chemists becomes evident.

Biologist, “Can you hand me the syringe?”

Chemists, “They don’t keep the syringes in the procedural room?”

Biologist, “No. Where are your surgical tools, I thought you wanted to extract the lymph nodes?”

Chemists, “I thought you would bring the surgical equipment since you were going to show us how to dissect?”

Biologist, “That’s not how it works. All my mice are immune compromised, so I don’t want to risk using my equipment with wild type mice.”

Mitch to the chemistry grad student in my best postdoc voice, “Well, you better go find some equipment if you want to get your experiment done today.”

Grad student flies out in search of a miracle. I do my best to laugh off the situation with the biologist. The biologist is taking it well, but I was definitely embarrassed. After 10 minutes the chemistry graduate student returns with syringes, needles, scissors, and cutting blades.

Biologist picks up scissors, “These are not surgical scissors, these are to cut paper I can’t use these.” Looks at our cutting blades, “Is that a box cutter? That definitely won’t work on something as small as a mouse. You’re going to have to order real surgical equipment.”

Although that day went horribly wrong at least we learned what would be needed for the next attempt. Last month we used our new surgical tools and performed the dissection of the mice as we originally planned with the biologist. The data from that experiment is amazing and compliments the graduate student’s in vitro work beautifully. The paper is already done and waiting for the PI to submit to Angew.

Next Time: My first tail vein injection and the story of the fainting biologist.


By July 6, 2010 10 comments in vivo chemistry