Nanoparticle screen could speed up drug development
納米顆粒篩選加速藥物研發
Many scientists are pursuing ways to treat disease by delivering DNA or RNA that can turn a gene on or off. However, a major obstacle to progress in this field has been finding ways to safely deliver that genetic material to the correct cells.
很多科學工作者都在尋求通過傳遞可開啟或關閉基因的DNA或RNA來治療的方法。然而，在這一領域取得進展的一大障礙就是尋找安全傳遞遺傳物質到正確細胞的方法。
Encapsulating strands of RNA or DNA in tiny particles is one promising approach. To help speed up the development of such drug-delivery vehicles, a team of researchers from MIT, Georgia Tech, and the University of Florida has now devised a way to rapidly test different nanoparticles to see where they go in the body.
包覆RNA或DNA是一個有前景的途徑。為了加速這種藥物運載工具的研發，來自 MIT, Georgia Tech, 和 the University of Florida的研究團隊開發了一種快速測試不同納米顆粒在體內的去處的方法。
"Drug delivery is a really substantial hurdle that needs to be overcome," says James Dahlman, a former MIT graduate student who is now an assistant professor at Georgia Tech and the study's lead author. "Regardless of their biological mechanisms of action, all genetic therapies need safe and specific drug delivery to the tissue you want to target."
“藥物運載是需要攻克的難關，” James Dahlman，前MIT研究生、現Georgia Tech助理教授、文章的第一作者，說。“不管它們的生物作用機制如何，所有的基因療法都需要安全、特定的將藥物運載到靶組織的方式。”
This approach, described in the Proceedings of the National Academy of Sciences the week of Feb. 6, could help scientists target genetic therapies to precise locations in the body.
這一方式，發表在2月6號這周的 Proceedings of the National Academy of Sciences ，可以幫助科研工作者研發針對體內精確位置的基因療法。
"It could be used to identify a nanoparticle that goes to a certain place, and with that information we could then develop the nanoparticle with a specific payload in mind," says Daniel Anderson, an associate professor in MIT's Department of Chemical Engineering and a member of MIT's Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science (IMES).
“它可以用于確認去確定位置的納米顆粒，利用這些信息，我們接下來可以在理論上開發特定負載的納米顆粒，”Daniel Anderson，MIT化工系助理教授、MIT's Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science (IMES)的一員。
The paper's senior authors are Anderson; Robert Langer, the David H. Koch Institute Professor at MIT and a member of the Koch Institute; and Eric Wang, a professor at the University of Florida. Other authors are graduate student Kevin Kauffman, recent MIT graduates Yiping Xing and Chloe Dlott, MIT undergraduate Taylor Shaw, and Koch Institute technical assistant Faryal Mir.
文章的主要作者有Anderson; Robert Langer, the David H. Koch Institute Professor at MIT and a member of the Koch Institute; and Eric Wang, a professor at the University of Florida. Other authors are graduate student Kevin Kauffman, recent MIT graduates Yiping Xing and Chloe Dlott, MIT undergraduate Taylor Shaw, and Koch Institute technical assistant Faryal Mir。(2017-02-08)
Targeting disease
Finding a reliable way to deliver DNA to target cells could help scientists realize the potential of gene therapy—a method of treating diseases such as cystic fibrosis or hemophilia by delivering new genes that replace missing or defective versions. Another promising approach for new therapies is RNA interference, which can be used to turn off overactive genes by blocking them with short strands of RNA known as siRNA.
找到可靠的將DNA運載到靶細胞的方式可以幫助科研工作者們認識到基因療法--一種通過運載新的基因來囊腫性纖維化、血友病等疾病的方法--替代丟失或有缺陷的基因來治療的潛力。新療法的另一種有前景的實現方式是RNA干預，RNA干預通過用一小段RNA，即siRNA，來阻礙過于活躍的基因的表達。
Delivering these types of genetic material into body cells has proven difficult, however, because the body has evolved many defense mechanisms against foreign genetic material such as viruses.
運載這些基因材料到體內細胞中十分困難，畢竟人體進化出了很多防御機制來抵抗病毒等外來基因材料。
To help evade these defenses, Anderson's lab has developed nanoparticles, including many made from fatty molecules called lipids, that protect genetic material and carry it to a particular destination. Many of these particles tend to accumulate in the liver, in part because the liver is responsible for filtering blood, but it has been more difficult to find particles that target other organs.
為了避開這些防御機制，Anderson實驗室開發出了納米顆粒，其中很多從脂類制得，來保護基因材料，并攜帶其到目的地。這些顆粒中有許多都傾向于再肝臟積聚，這部分上因為肝臟負責過濾血液，但這樣就更難以發現瞄準其他器官的顆粒。
"We've gotten good at delivering nanoparticles into certain tissues but not all of them," Anderson says. "We also haven't really figured out how the particles' chemistries influence targeting to different destinations."
“我們已經善于把納米顆粒運載到特定組織，但并非所有組織，”Anderson說。“我們也還沒有弄清顆粒的化學性質如何影響其瞄準的目標。”(2017-02-12)
To identify promising candidates, Anderson's lab generates libraries of thousands of particles, by varying traits such as their size and chemical composition. Researchers then test the particles by placing them on a particular cell type, grown in a lab dish, to see if the particles can get into the cells. The best candidates are then tested in animals. However, this is a slow process and limits the number of particles that can be tried.
為了發現有潛力的候選顆粒，Anderson實驗室通過改變粒徑、化學組成，開發了包含數千顆粒的庫。然后研究者將它們放置在特定細胞類型上，在培養皿中培養，來看顆粒是否可以長到細胞中。之后用表現最好的候選顆粒作動物實驗。然而，這是一個緩慢的過程，并且限制了可試驗的顆粒數量。
"The problem we have is we can make a lot more nanoparticles than we can test," Anderson says.
To overcome that hurdle, the researchers decided to add "barcodes," consisting of a DNA sequence of about 60 nucleotides, to each type of particle. After injecting the particles into an animal, the researchers can retrieve the DNA barcodes from different tissues and then sequence the barcodes to see which particles ended up where.
“我們的問題是我們能制造的顆粒數目比我們能測試的多太多，”Anderson說。為克服這個障礙，研究人員決定加入“條碼”，其由一段約60個核苷酸的DNA序列組成。在將顆粒注入到動物后，研究人員從各組織中回收DNA條碼，再測定條碼序列來弄清顆粒最終停留在哪。
"What it allows us to do is test many different nanoparticles at once inside a single animal," Dahlman says.
“這種方法允許我們在一個動物中同時測試多個不同納米顆粒，”Dahlman說。
Tracking particles
追蹤顆粒
The researchers first tested particles that had been previously shown to target the lungs and the liver, and confirmed that they did go where expected.
研究人員首先測試先前顯示把肺臟和肝臟作為目標的顆粒，確認它們是否去向期望的組織。
Then, the researchers screened 30 different lipid nanoparticles that varied in one key trait—the structure of a component known as polyethylene glycol (PEG), a polymer often added to drugs to increase their longevity in the bloodstream. Lipid nanoparticles can also vary in their size and other aspects of their chemical composition.
然后，研究人員篩選了30種不同脂類顆粒，它們只在一個關鍵特點上不同--那就是其成分聚乙二醇(PEG)的結構，聚乙二醇經常被加入到藥物中來延長其在血流中的壽命。脂類納米顆粒也可以改變其粒徑，和其他化學成分。
Each of the particles was also tagged with one of 30 DNA barcodes. By sequencing barcodes that ended up in different parts of the body, the researchers were able to identify particles that targeted the heart, brain, uterus, muscle, kidney, and pancreas, in addition to liver and lung. In future studies, they plan to investigate what makes different particles zero in on different tissues.
每個納米顆粒也用一個30DNA條碼標記。通過測序條碼最終在身體中的位置，除了肝臟和肺臟，研究人員還能夠發現指向心臟、腦、子宮、肌肉、腎臟和胰腺的顆粒。在未來的研究中，他們計劃研究使不同顆粒瞄準不同組織的機理。
The researchers also performed further tests on one of the particles, which targets the liver, and found that it could successfully deliver siRNA that turns off the gene for a blood clotting factor.
研究人員也在對其中瞄準肝臟的顆粒做進一步的研究，發現其可以順利地運載可以關閉凝血因子基因的siRNA。
Victor Koteliansky, director of the Skoltech Center for Functional Genomics, described the technique as an "innovative" way to speed up the process of identifying promising nanoparticles to deliver RNA and DNA.
Victor Koteliansky，Skoltech Center for Functional Genomics的負責人，評論這一技術是一種創新方式，加速了鑒別潛在的運載RNA和DNA的納米顆粒。
"Finding a good particle is a very rare event, so you need to screen a lot of particles. This approach is faster and can give you a deeper understanding of where particles will go in the body," says Kotelianksy, who was not involved in the research.
“找到一個優良的顆粒是極稀少的事件，因此你需要篩選很多顆粒。這一方法快速，可以使你更深入地理解顆粒將進入身體的哪個組織，”沒有參加這一研究的Kotelianksy說。
This type of screen could also be used to test other kinds of nanoparticles such as those made from polymers. "We're really hoping that other labs across the country and across the world will try our system to see if it works for them," Dahlman says.
這一篩選方法也可以用于測試其他種類的納米顆粒，例如由多聚物制備的納米顆粒。“我們非常希望國內外其他實驗室測試我們的系統對他們是否有效，”Dahlman說。(2017-02-12)
