{"id":629,"date":"2016-06-17T11:35:33","date_gmt":"2016-06-17T15:35:33","guid":{"rendered":"https:\/\/www.bumc.bu.edu\/cancercenter\/?p=629"},"modified":"2016-06-17T11:35:57","modified_gmt":"2016-06-17T15:35:57","slug":"light-beams-and-dna-cages-could-deliver-drugs-to-just-the-right-spot","status":"publish","type":"post","link":"https:\/\/www.bumc.bu.edu\/cancercenter\/2016\/06\/17\/light-beams-and-dna-cages-could-deliver-drugs-to-just-the-right-spot\/","title":{"rendered":"Light Beams and DNA Cages Could Deliver Drugs to Just the Right Spot"},"content":{"rendered":"

June 7, 2016 | Written by: Neil Savage | Source: BU Research<\/a><\/p>\n

Getting drugs to go just where you want them inside the human body is no easy task, and using high doses of chemicals that are carried by the bloodstream to the wrong tissues or organs can lead to toxic side effects. That\u2019s why scientists have been working for years to figure out how to deliver much smaller doses to precise targets\u2014developing chemotherapy drugs that bind only to tumor cells, for instance. Now Boston University researchers have developed a new method that traps drugs or other molecules within tiny cages made of DNA, then releases them once they\u2019ve reached the right spot with a quick flash of light.<\/p>\n

\u201cBasically it\u2019s sort of a controlled drug release, and there wasn\u2019t a very good approach [to that] until now,\u201d says Xue Han, an assistant professor of biomedical engineering in Boston University\u2019s College of Engineering. \u201cWhat we did is to put these drugs physically inside a cage.\u201d<\/p>\n

Drugs are molecules, many of them big, with different areas on their surfaces that allow them to bind with receptors that have complementary areas, like puzzle pieces fitting together, allowing them to attach to and interact with a cell. The problem is that some cells have receptors that will take up a particular drug, even when they\u2019re not the cells that the drug is supposed to target. Scientists have traditionally dealt with this problem by adding small chemical groups to the surface of molecules so the receptor won\u2019t recognize it. Han, who is a Peter Paul Career Development Professor, says it\u2019s like sticking a tiny chemical hat on the drug to disguise it. For some small-molecule drugs, that can work well.<\/p>\n

But some drugs, such as proteins, are just so big that a tiny modification won\u2019t disguise it. \u201cA large protein wearing a small hat still looks like the same protein,\u201d she says.<\/p>\n

Her idea was to enclose the protein in a cage, hiding it completely from the receptors. \u201cThe thing that reacts with this drug will not see the drug,\u201d she says. \u201cIt will see a box.\u201d Han and her study co-authors, Richie Kohman, a former postdoctoral fellow in Han\u2019s lab, Susie Cha, a graduate student in biomechanical engineering, and Hengye Man, an associate professor of biology in the BU College of Arts and Sciences, described their method in a paper published in ACS Nanoletters<\/em><\/a> in March 2016.<\/p>\n

To make the box, they turned to a technique called DNA origami, named for the Japanese art of folding sheets of paper into complex shapes, which scientists have been using for the past decade. Scientists can create a strand of DNA with its nucleic acids arranged in the order they want. They heat up the strands to near boiling, then let them slowly cool, and the natural attraction and repulsion between the different nucleic acids causes the strands to bend and fold into a desired shape. Kohman, who is a biomaterials engineer, and Han used DNA origami to create an open-ended barrel about 50 nanometers wide, with a 20-nanometer cavity inside. \u201cThat\u2019s large enough to fit some big proteins inside,\u201d Han says.<\/p>\n

To keep their drugs in the enclosure, they left little bits of DNA hanging unattached inside the cage, then added more small molecules to act as tiny chains, binding to the drugs and holding them in place. The chains were designed so that a small jolt of energy from a beam of light would break them, setting the proteins free. Once the cage is in the right spot, the light snaps the chains and the drugs just drift out, winding up where they\u2019re wanted.<\/p>\n

The researchers tested their system using a fluorescent dye called Oregon Green, which is commonly used to tag proteins and other biological molecules. They trapped molecules of the dye inside the cages, then zapped them with low-power beams of ultraviolet light. After 40 seconds of exposure, almost all the dye had left the cages.<\/p>\n

The dye was a small molecule. To see if the scheme would work with larger proteins, the researchers trapped two other kinds of molecules. One was a protein derived from cow\u2019s blood. The other was streptavidin, a molecule used to bind drugs to cancer cells. After about a minute of low-level light exposure, most of the proteins had escaped the cages.<\/p>\n

Finally, to check that the process didn\u2019t repress the biological activity of the molecules, they tried the technique on a small molecule called glutamate that affects the activity of brain cells. They added the caged glutamate to a culture of brain cells, hit them with a brief burst of light, then measured how the flow of calcium in the brain cells had changed. Just a 1 millisecond flash of light was enough to release the glutamate and increase calcium activity in the cells.<\/p>\n

It\u2019s that finding that has Han most excited. She studies neuroscience, and is looking for ways both to understand the activity of brain cells and to deliver drugs that can affect that activity. For instance, there are certain molecules being studied that might slow the progression of Parkinson\u2019s disease, if they can be delivered to the right spot. \u201cI\u2019m really interested in all these neuropeptide hormones. There are so many of them in the brain,\u201d Han says. \u201cWe know peptide hormones are very important. We just don\u2019t know how they work.\u201d<\/p>\n

One difficulty with any drug treatment for brain disorders, including cancer, is getting the drug past the blood-brain barrier. While that barrier prevents most molecules from moving out of the bloodstream and into brain cells, there are certain ones that pass easily, and it might be possible to use them to carry caged molecules to the brain. That could mean delivering the drug directly to the brain of a Parkinson\u2019s patient without having to stick a needle into it.<\/p>\n

One question will be how to get light to these cages if they\u2019re deep in the body. That\u2019s something other people are still working on, Han says. Though the experiment used ultraviolet light, it might work better to use infrared light, which can penetrate tissue fairly deeply and is less likely to damage cells than ultraviolet. Chemists have already created molecular changes that break under infrared light. It might also be possible to shine light into certain areas by using an endoscope to carry it to cavities within the body.<\/p>\n

Of course, any use in humans would require approval from the US Food and Drug Administration, which would require years of testing. But for lab studies involving cells in petri dishes, the technique could be used almost immediately, Han says. In fact, the potential uses, from basic research to treating neurological diseases to fighting cancer, could turn out to be many, she says. \u201cI think it has very broad applications.\u201d<\/p>\n

Han\u2019s research was funded by the National Institutes of Health, the Pew Foundation, the Alfred P. Sloan Foundation, and BU\u2019s Department of Biomedical Engineering.<\/p>\n","protected":false},"excerpt":{"rendered":"

June 7, 2016 | Written by: Neil Savage | Source: BU Research Getting drugs to go just where you want them inside the human body is no easy task, and using high doses of chemicals that are carried by the bloodstream to the wrong tissues or organs can lead to toxic side effects. That\u2019s why […]<\/p>\n","protected":false},"author":11679,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/www.bumc.bu.edu\/cancercenter\/wp-json\/wp\/v2\/posts\/629"}],"collection":[{"href":"https:\/\/www.bumc.bu.edu\/cancercenter\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bumc.bu.edu\/cancercenter\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bumc.bu.edu\/cancercenter\/wp-json\/wp\/v2\/users\/11679"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bumc.bu.edu\/cancercenter\/wp-json\/wp\/v2\/comments?post=629"}],"version-history":[{"count":3,"href":"https:\/\/www.bumc.bu.edu\/cancercenter\/wp-json\/wp\/v2\/posts\/629\/revisions"}],"predecessor-version":[{"id":632,"href":"https:\/\/www.bumc.bu.edu\/cancercenter\/wp-json\/wp\/v2\/posts\/629\/revisions\/632"}],"wp:attachment":[{"href":"https:\/\/www.bumc.bu.edu\/cancercenter\/wp-json\/wp\/v2\/media?parent=629"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bumc.bu.edu\/cancercenter\/wp-json\/wp\/v2\/categories?post=629"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bumc.bu.edu\/cancercenter\/wp-json\/wp\/v2\/tags?post=629"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}