Medical drugs sometimes cause more damage than they cure. One solution to this problem is to put the drugs inside a capsule, protecting them from the body - and the body from them - until they can be released at just the right spot. There are lots of ways to trigger this release, including changing temperature, acidity, and so on. But triggers can come with their own risks - burns, for example. Now, researchers in California have designed what could be a harmless trigger to date: shining near-infrared light (NIR) on the drug in the capsule.
药物有时造成的损害要大于治疗效果。解决这个问题的一个方法是将药物放入胶囊中，保护它们不受身体的伤害（身体也不受药物的伤害），直到它们能够在正确的位置释放出来。有很多方法可以触发这种释放，包括改变温度、酸度等。但触发器可能会带来自身的风险，例如烧伤。现在，加利福尼亚的研究人员已经设计出一种迄今为止可能是无害的触发器：对胶囊药物进行近红外光（NIR) 照射。
The idea of using light to liberate the drug in the capsule isn't new. Researchers around the globe have developed polymers and other materials that begin to break down when they absorb cither ultraviolet (UV) or visible light. But tissues also readily absorb UV and visible light, which means the drug release can be triggered only near the skin, where the light can reach the capsule. NIR light largely passes through tissues, so researchers have tried to use it as a trigger. But few compounds absorb NIR well and go through chemical changes.
利用光线释放胶囊中的药物并不是什么新鲜事。全球的研究人员已经开发出当它们吸收紫外线或可见光时，就会开始分解的聚合物和其他材料。但是，组织也很容易吸收紫外线和可见光，这意味着药物释放只能在皮肤附近触发，在那里光线可以到达胶囊。近红外光主要通过组织，因此研究人员尝试将其作为触发器。但很少有化合物能很好地吸收近红外并经历化学变化。
That changed last year when Adah Almutairi, a chemist at the University of California, San Diego, reported that she and her colleagues had designed a polymer that breaks down when it absorbs NIR light. Their polymer used a commercially available NIR-absorbing group called o-nitrobenzyl (ONB). When they catch the light, ONB groups fall off the polymer, leading to its breakdown. But ONB is only a so-so NIR absorber, and it could be poisonous to cells when it separates from the polymer.
去年，加州大学圣地亚哥分校的化学家Adah Almutairi报告说，她和她的同事设计了一种聚合物，这种聚合物在吸收近红外光时会分解。聚合物使用了一种市面有售的近红外吸收基团，称为邻硝基苄基（ONB）。当它们捕捉到光线时，ONB基团从聚合物上脱落，导致聚合物分解。但ONB只是一种一般的近红外吸收剂，当它从聚合物中分离出来时，可能对细胞有毒。
So Almutairi and her colleagues reported creating a new material for capsules that's even better. This one consists of a long chain of compounds called cresol groups linked in a polymer. Cresol contains reactive components that make it highly unstable in its polymeric form, a feature Almutairi and her colleagues use to their advantage. After polymerizing the cresols, they cap each reactive component with a light-absorbing compound called Bhc. When the Bhcs absorb NIR light, the reactive groups are exposed and break the long polymer into two short chains. Shining additional light continues this breakdown, potentially releasing any drugs in the capsule. What's more, Almutairi says, Bhc is 10 times better at absorbing NIR than is ONB and is not poisonous to cells.
因此，Almutairi和她的同事报告称，他们发明了一种更好的胶囊新材料，由一种长链化合物组成，称为甲酚基团，连接在聚合物中。甲酚含有活性成分，在聚合物形式中高度不稳定，Almutairi和她的同事利用了这一特性。甲酚聚合后，他们用一种称为Bhc的吸光化合物覆盖每个活性成分。当Bhc吸收近红外光时，活性成分暴露并将长聚合物断裂为两条短链。额外的光照会继续这种分解，可能释放出胶囊中的任何药物。而且，Almutairi说，Bhc吸收NIR的能力是ONB的10倍，对细胞无毒。
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