醫用植入設備 一個甜美的想法

Medical implants.

醫用植入設備。

A sweet idea.

一個甜美的想法。

Researchers are trying to harness glucose-the body's own fuel-to power implantable gadgets such as pacemakers.

研究人員正試圖利用葡萄糖-人體自身的燃料-作爲像起搏器這樣的可植入設備的能源

LIKE any other electrical device, a pacemaker needs a power source. Since the first permanent pacemaker was installed in 1958, manufacturers of implantable medical devices (IMDs) have tinkered with many different ways of supplying electricity to their products. A variety of chemical batteries have been tried, as well as inductive recharging schemes and even plutonium power cells that convert the heat from radioactive decay into electricity. Plutonium-powered pacemakers still turn up from time to time in mortuaries and hospitals, and a failure to dispose of them properly keeps America's Nuclear Regulatory Commission busy handing out citations to unsuspecting hospitals.

和其他所有的電子設備一樣，一個起搏器同樣需要能源。自從1958年第一個永久起搏器被植入後，可植入醫療設備的製造商就在不斷嘗試爲其產品提供電能的各種方法。嘗試了各種化學電池以及感應充電計劃，甚至是將放射衰變的熱能轉換爲電能的鈈電源單元格。現在，鈈電源起搏器還是時不時的出現在停屍房和醫院中，並且使得美國核管理委員忙於忙於處罰那些疏於妥善處理鈈電源起搏器的醫院。

Today, non-rechargeable lithium-based batteries are common. Used in many cardiological and neurological implants, they provide between seven and ten years of life. That is more than enough: the speed of medical progress is such that by the time the battery has run down it is generally time to replace the whole device with a newer model in any case.

如今，不可充電的鋰電池較爲普遍。應用在心臟病和神經源性疾病的移植設備中，一般能夠提供7年到10年的使用時間。這麼長的使用時間顯得綽綽有餘：醫學發展的速度意味着等到設備的電量用光就到了用一個更先進的型號來替換整個設備的時候。

But that has not dissuaded researchers from continuing to seek perfection, in the form of a compact, perpetual energy source which does not require external recharging. Now, several researchers are closing in on just such a solution using glucose, a type of sugar that is the main energy source for all cells in the body.

然而這並沒有阻止研究人員繼續尋找完美的，緊湊型的永久能源，從而使得這些移植設備不再需要外部充電。現在，幾個研究人員正在接近一個能夠提供這樣能源的方法，使用葡萄糖，即爲人體所有細胞提供主要能源的一種糖。

Many other ideas have been tried down the years. The kinetic energy of the human body, for example, has long been harnessed to power watches, and should also be enough to keep a pacemaker ticking. Temperature differences between the body and the ambient air mean that thermoelectric couples can generate useful quantities of juice. A properly tuned device could capture background radio-frequency energy and rectify it into small amounts of usable power.

這些年還有許多其他想法也被嘗試。比如，很久以前人體動能就用來爲手錶提供能量，這種動能也足夠維持起搏器的運轉。人體與外部環境的溫差意味着熱電偶能夠產生一定數量能量。一個適當調諧裝置能夠捕獲北京射頻能量並且將其轉換成少量可用能源。

Although all these ideas have been shown to work in theoretical tests on lab benches, they all suffer from the same handicap: intermittent operation. Unconscious patients, for instance, generate little kinetic energy. Sitting in a warm room reduces the power available from thermocouples. And radio waves are common but not ubiquitous. These are serious drawbacks for an IMD that may be responsible for keeping someone alive.

儘管這些想法在實驗的理論測試中運轉正常，但是他們都有一個同樣的缺陷：間歇運行。例如，處於昏迷的患者產生的人體動能很少。處於溫暖的房間中會減少熱電偶產生的可用能量。另外射頻很常見，但是也不是處處可見。這些問題對於維持生命的可移植醫療設備來說都是十分嚴重的缺陷。

Power in the blood.

血液中的能量。

A glucose-powered implant would solve such problems. Glucose is continuously delivered throughout the body by its circulatory systems. A sugar-powered device would therefore have access to a constant supply of fuel, and could be implanted almost anywhere.

而一個葡萄糖供能的移植設備可以解決這些問題。葡萄糖由人體的循環系統被源源不斷的輸送到人體各處。一個糖分供能的設備因此能夠取得持續供給的能量並且幾乎可以在任何位置進行移植。

One approach, which has been employed by Sameer Singhal, a researcher at the CFD Research Corporation in Alabama, involves the same enzymes that break down glucose within a living cell. Using carbon nanotubes, he and his colleagues immobilised two different enzymes on the electrodes of a fuel cell, where they generated electricity by freeing electrons from glucose. At present, only two of the 24 available electrons in a single glucose molecule can be harnessed, but refinements to the technology should boost that number.

就職於Alabama的CFD Research Corporation的研究人員Sameer Singhal所使用的方法涉及利用酶將活細胞中的葡萄糖分解。利用碳納米管，他和他的同事在燃料電池的電子上找到了2種不同的酶，在燃料電池中他們通過釋放葡萄糖的電子來產生電能。現在，在一個葡萄糖分子中的24個可用電子中只有2個可以利用，但是對這項技術的後續完善應該會使得可以利用的電子數量有所增加。

Dr Singhal has implanted prototype devices into live beetles. Fitted with a fuel cell about the size of a penny, the bionic bugs were able to generate over 20 microwatts (20 millionths of a watt) during a two-week trial.

Singhal博士將設備原型移植進了甲蟲活體。放入了一個一便士大小的能量池，這些甲蟲在2周實驗期內產生了20微瓦（一瓦特的百萬分之二十）。

That is only around a fifth of the power that a pacemaker requires, but Dr Singhal reckons that a human-sized version of his cell would be able to deliver enough juice. There is a catch, though: a process called biofouling, in which foreign objects implanted in the body become encrusted with proteins and tissue. That could render Dr Singhal's device inoperable after only a few months. Equally worrying are the enzymes, which tend to break down over time. Losing enzymes means losing power.

這只是一個起搏器所需能量的15分之一，但是Singhal博士認爲人類體積大小的細胞量能夠產生足夠的能量。這裏有個欠缺點：被稱做生物污垢的過程，即被移植進人體的外來物會嵌入蛋白質和組織中。這會使得Singhal博士的設備在移植後的幾個月內便無法使用。同樣使人擔憂的是酶，這種物質隨着時間的推移會被分解。而丟失酶就意味着丟失能量。

Rahul Sarpeshkar, an electrical engineer at the Massachusetts Institute of Technology, has a solution to both these problems. In a paper published on June 12th in Public Library of Science, Dr Sarpeshkar and his colleagues describe building a glucose fuel cell which uses a platinum catalyst that does not degrade over time.

一位MIT的電子工程師Rahul Sarpeshkar有個方法可以解決這兩個問題。6月12號發表於Public Library of Science的一篇論文中，Sarpeshkar博士和他的同事證實用鉑催化劑打造的葡萄糖能量池，其效果不會隨着時間被削弱。

The downside is that platinum is a less efficient catalyst than the enzymes used by Dr Singhal, and so Dr Sarpeshkar's cell works less well. But it might be able to generate enough electricity to run the next generation of ultra-low-power IMDs.

該方法的缺點是鉑催化劑與Singhal博士所用的酶相比效率不高，因此，Sarpeshkar博士的能量池運轉效果不好。但是它也許能夠生產足夠的電能來運轉下一代超低功耗的可移植醫療設備。

Dr Sarpeshkar also has a novel solution to the biofouling problem: implant the fuel cell in the cerebrospinal fluid (CSF) surrounding the brain. Although the CSF has only half the glucose concentration of the bloodstream, it is virtually free of the proteins and cells which would foul a device implanted in other areas of the body, and thus its life would be greatly extended.

另外，Sarpeshkar博士還有一個針對於生物燃料問題的新型解決方法：在大腦周圍的腦脊液（CSF）中植入能量池。儘管腦脊液僅含有體液中葡萄糖濃度的一半，但是這樣做幾乎可以使其免於植入人體其他部位而被蛋白質和細胞包圍的命運，因此使其使用壽命大大延長。

Other approaches could yield more energy. Some soil-dwelling bacteria have evolved to deposit the electrons from glucose oxidation onto iron molecules, which allows researchers to trick them into living on the anode of a fuel cell. A colony of microbes like these, properly isolated from the host's immune system, might be coerced into trading electrons for nutrients from the bloodstream. The bacteria can renew their own enzymes, so such a system should last indefinitely. But the idea of implanting a bacterial colony into a patient might be a tricky one to get past medical regulators-not to mention public opinion.

其他一些方法則需要更多的能量。用一些土壤細菌將葡萄糖氧化過程所產生的電子安置在鐵分子上，這樣研究人員就可以誘使這些細菌存活在能量池的陽極上。像這樣的克隆微生物，與寄主的免疫系統相分離，可能被迫的用電子與體液交換營養成分。細菌可以重新激活他們自身的酶，因此這樣的系統能夠永久的持續下去。然而將細菌克隆體移植進病人的身體這種想法可能無法通過醫療監管人員的監管，就更不要說公衆輿論了。

A better idea might be to retrain some of the body's own cells to do the work. Just as an outdated procedure called a cardiomyoplasty involved severing a seldom-used upper-back muscle and wrapping it around the heart to assist in pumping blood, muscle fibres might be retrained to crank an electromechanical generator. Such a setup would be capable of producing enough electricity to drive even the most power-hungry of devices, like artificial hearts.

一個更好的想法可能是將一些人體自身的細胞進行再培訓來完成這個工作。正如一個已過時的手術，叫做心肌成形術，將較少用到的上背部肌肉切斷並將它包絡再心臟周圍來協助心臟輸送血液，肌肉纖維也許可以經過在訓練後來驅動機電發電機。這樣的方法能夠產生足夠的電能來驅動哪怕是最耗費能源的設備，比如人造心臟。

The energy density of lithium batteries has come a long way in the past few decades, but the chemical reaction on which they rely will never be able to match the energy available from the metabolisation of glucose. The chemical energy in a gram of glucose is nearly half the amount available from petrol, a famously energy-dense fuel. With a bit of refinement, sugar could prove a very sweet solution for powering the next generation of IMDs.

在過去的幾十年間，鋰電池的能量密集度取得了長足的發展，但是鋰電池所依賴的化學反應永遠也無法產生與葡萄糖代謝所產生的能量相匹敵的數量。一克葡萄糖所含有的化學能量相當於半克汽油能產生的能量，原油是衆所周知的能源密集型燃料。再經過一點優化，糖就有可能爲下一代可移植醫療設備的能源問題提供一個十分完美的解決辦法。