The US military’s race to make fake blood

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Its call sign was Morphine 1-2. In February 2007, the hulking dual-­rotor casualty evacuation helicopter had just flown three wounded soldiers to a field hospital in Balad, north of Baghdad, when another call came: an emergency mission to fly through an insurgent-controlled area in broad daylight. Typically, helicopters would be in a spot like this only at night, and with all lights turned off. As it passed near the city of Karmah, in the eastern side of Al-Anbar province, an insurgent fired a portable missile launcher. The tail gunner, who likely saw the shot roaring in, yelled for the pilot to make an evasive move. But the missile had already locked on, and the ensuing blast started a fire on board. After the pilot battled the failing machine for 58 agonizing seconds, Morphine 1-2 plunged to the ground. All seven crew members were killed.

它的呼号是“吗啡1-2”。2007年2月，这架庞大的双旋翼伤员撤离直升机刚将三名受伤士兵送往巴格达以北巴拉德的一家野战医院，就接到了另一个任务：在光天化日之下飞越叛乱分子控制区的紧急任务。通常情况下，直升机只会在夜间且关闭所有灯光的情况下进入这种区域。当它经过安巴尔省东部的卡尔马市附近时，一名叛乱分子发射了便携式导弹发射器。尾炮手可能看到了呼啸而来的炮弹，大声呼叫飞行员采取规避动作。但导弹已经锁定目标，随后的爆炸导致机上起火。在飞行员与失控的机器搏斗了58秒后，吗啡1-2号坠毁，机上七名机组人员全部遇难。

Why was the helo there in daylight? “It was getting blood and bringing it back. It was [on] what we call a ‘blood run,’ and [it’s] the highest of priorities besides casualty evacuation,” explains Lieutenant Commander Robert Murray, a Navy officer and program manager at DARPA, the Defense Advanced Research Projects Agency, who studied this incident as an intelligence officer. Today, a chronic shortage of blood in both the military and civilian worlds is fueling a race to develop synthetic alternatives. About 90% of preventable battlefield deaths are due to hemorrhage—bleeding that happens when a blood vessel ruptures—and it’s the leading cause of maternal deaths worldwide.

为什么直升机要在白天执行任务？“它当时正在运送血液并将其带回。这被称为‘血液运输任务’，除了伤员撤离外，这是最高优先级的任务，”美国国防高级研究计划局（DARPA）的海军军官兼项目经理罗伯特·默里中校解释道，他曾以情报官的身份研究过这起事件。如今，军事和民用领域长期存在的血液短缺正推动着合成替代品的研发竞赛。约90%的战场可预防死亡是由出血（血管破裂引起的失血）造成的，这也是全球孕产妇死亡的主要原因。

A study published in Transfusion in 2025 found that of 1.2 million trauma patients in the United States who potentially needed blood before reaching a hospital, just 1% received it. The shortage results in about 10,000 preventable deaths each year in the US, according to the American College of Surgeons. Globally, that figure is likely in the millions. One reason for the shortfall is that blood has a storage problem. Whole blood lasts only 35 days when refrigerated, so banks separate out components to stretch the timeline. But that’s an imperfect solution. The platelets that help wounds clot are typically stored at room temperature and last for a week or less.

2025年发表在《输血》杂志上的一项研究发现，在美国120万名在到达医院前可能需要输血的创伤患者中，只有1%的人得到了输血。据美国外科医生学会称，这种短缺每年在美国导致约10,000例可预防的死亡。在全球范围内，这一数字可能高达数百万。造成短缺的一个原因是血液存在储存问题。全血冷藏后只能保存35天，因此血库会将血液成分分离以延长保存时间。但这并非完美的解决方案。有助于伤口凝血的血小板通常储存在室温下，有效期仅为一周或更短。

Hospitals and the military freeze the red blood cells that carry oxygen, as well as the protein-rich plasma that restores volume and aids coagulation. Once thawed, though, both will spoil within days. “What happens if I don’t know when I’m going to be attacked? Well, thaw it and you let it expire, right?” Murray says. A JAMA study of combat injuries in Afghanistan suggests a magic number for someone who needs a transfusion: You have 36 minutes to get started. That’s why Murray—who, in addition to his military experience, has a PhD in physiology—is leading a DARPA effort to address blood’s battlefield problems.

医院和军队会冷冻携带氧气的红细胞，以及恢复血容量并辅助凝血的富含蛋白质的血浆。然而，一旦解冻，两者都会在几天内变质。“如果我不知道什么时候会受到攻击怎么办？那就解冻它，然后让它过期，对吧？”默里说。一项关于阿富汗战斗伤情的《美国医学会杂志》（JAMA）研究提出了一个针对需要输血者的“神奇数字”：你必须在36分钟内开始输血。这就是为什么除了军事经验外还拥有生理学博士学位的默里，正在领导DARPA的一项工作，以解决战场上的血液问题。

He’s in charge of a new $73 million dollar program called RAPIID (for “resuscitation and prevention of ischemia-induced dysfunction”). Its goal is to create shelf-stable versions of the three major transfusion constituents: plasma, platelets, and red blood cells. As it gets underway late this year, RAPIID picks up on decades of work to synthesize blood or help it last longer. Most recently, that includes a prior $47.5 million DARPA project called FSHARP (for “fieldable solutions for hemorrhage with bio-artificial resuscitation products”), in which researchers have demonstrated promising results in animals.

他负责一个名为RAPIID（意为“复苏与预防缺血诱导的功能障碍”）的新项目，预算为7300万美元。其目标是创造出三种主要输血成分的常温储存版本：血浆、血小板和红细胞。随着该项目于今年晚些时候启动，RAPIID将承接数十年来合成血液或延长其保存时间的研究成果。最近，这包括DARPA之前一个名为FSHARP（意为“用于出血的生物人工复苏产品的实地解决方案”）的4750万美元项目，研究人员已在该项目中展示了令人鼓舞的动物实验结果。

KaloCyte techs use a device called a tangential flow filtration machine to process unencapsulated hemoglobin. After processing, the hemoglobin is concentrated and then freeze-dried to make it shelf-stable. With RAPIID trials for the different components occurring in parallel, the goal is to have bags of dried blood products deployed in the field by 2029. That puts Murray in the position of a conductor coordinating an orchestra of clinical trials with the FDA, while also sourcing the paraphernalia that goes along with transfusions—everything from combat-durable storage bags to tests that could check how much artificial blood a patient already has.

KaloCyte的技术人员使用一种称为切向流过滤机的设备来处理未封装的血红蛋白。处理后，血红蛋白被浓缩并冷冻干燥，使其能够常温储存。随着RAPIID针对不同成分的试验并行进行，目标是在2029年前将袋装干燥血液产品部署到战场。这使得默里处于指挥官的位置，协调与美国食品药品监督管理局（FDA）进行的各项临床试验，同时还要采购输血所需的配套设备——从耐战的储存袋到可以检测患者体内已有多少人造血液的测试工具，应有尽有。

Getting it all done will be tough, but the military is feeling the pressure to address its shortage. Blood drives may not deliver in time after a mass-casualty event, and a JAMA study of combat injuries in Afghanistan suggests that if the injured person needs a transfusion, the magic number is 36 minutes. “If something is survivable—and generally we classify most all hemorrhage as survivable—[you’re] almost guaranteed to survive if you get the blood before that 36-minute mark,” Murray says. After that, the chance of survival “starts to drop precipitously.”

完成这一切将非常困难，但军方正感受到解决短缺问题的压力。在大规模伤亡事件发生后，献血活动可能无法及时提供血液，而一项关于阿富汗战斗伤情的JAMA研究表明，如果伤者需要输血，神奇数字是36分钟。“如果伤情是可以存活的——通常我们将几乎所有的出血都归类为可存活——如果你能在36分钟内得到输血，你几乎肯定能活下来，”默里说。在那之后，生存几率“开始急剧下降”。

In the mission to make portable, shelf-stable blood components, plasma is the low-hanging fruit. Researchers have known how to isolate and freeze-dry plasma, the yellowish liquid that makes up 55% of whole human blood, since the late 1930s. On the battlefields of World War II, its mix of water, salts, and thousands of types of proteins helped restore blood volume in wounded soldiers—and to some degree controlled bleeding. In the 1960s, the US abandoned freeze-dried plasma because it carried a risk of transmitting hepatitis to recipients from infected donors.

在制造便携式、常温储存血液成分的任务中，血浆是相对容易实现的目标。自20世纪30年代末以来，研究人员就已经知道如何分离和冷冻干燥血浆，这种淡黄色液体占人体全血的55%。在第二次世界大战的战场上，它所含的水、盐和数千种蛋白质的混合物帮助受伤士兵恢复了血容量，并在一定程度上控制了出血。20世纪60年代，美国放弃了冷冻干燥血浆，因为它存在将肝炎从受感染捐赠者传播给接受者的风险。

But screening, testing, and drying techniques improved, and starting in 2010, the US military launched a yearslong effort to rebuild its capacity for producing these products. Over the past two years, the FDA has allowed two types of freeze-dried plasma to be used in emergencies by the US military—and one can even be used by civilians. As for platelets, efforts at extending their life date back to the 1950s, but they haven’t seen a ton of success. Bioengineers have, for example, attempted to attach the membranes of platelets to synthetic particles. The most successful project comes from a company called Cellphire, which freeze-dries actual human platelets. The product has shown safety and efficacy in humans in clinical trials, but its dependence on donors.

但随着筛查、检测和干燥技术的改进，美国军方从2010年开始启动了一项为期多年的计划，以重建其生产这些产品的能力。在过去两年中，FDA已批准两种冷冻干燥血浆供美军在紧急情况下使用，其中一种甚至可供平民使用。至于血小板，延长其寿命的努力可以追溯到20世纪50年代，但并未取得太大成功。例如，生物工程师曾尝试将血小板膜附着在合成颗粒上。最成功的项目来自一家名为Cellphire的公司，该公司对真实的人类血小板进行冷冻干燥。该产品在临床试验中已显示出对人体的安全性和有效性，但它仍依赖于捐赠者。