IN THE PIPELINE: Unraveling Mystery Of Spider Web Silk
Some of the world's leading scientists are trying to untangle a chemical conundrum: what makes the silken web of a spider so strong, yet so light and forgiving?
"Spider silk is tougher per gram weight than steel," yet is lightweight, flexible and biodegradable, said spider-web researcher Paula Hammond, an associate professor of chemical engineering at the Massachusetts Institute of Technology.
While the properties of spider web silk have been well-known for centuries, man has only recently been able to replicate them. Now the military and corporate world are intrigued by potential applications like bulletproof clothing, human tendon replacement, medical surgery sutures, or even mountaineer's climbing ropes.
There have been many attempts at creating synthetic spider silk. One effort involved raising spiders in colonies to harvest their silk. But that failed because the critters are difficult to domesticate, being territorial and cannibalistic, Hammond said.
Other researchers have gathered spiders to collect their DNA, implanted it in goats, then harvested the spider silk protein from the goats' milk. That approach is being used by Nexia Biotechnologies Inc. (T.NXB) of Montreal, which has developed a product it calls BioSteel, based on recombinant spider silk proteins and using its own "transgenic goat technology."
Spiders spin their webs by secreting a fibrous protein as a fluid which forms into a solid - a process that is still being researched. Hammond said her group's work has created "first generation" spider silk material in the lab.
Hammond heads a team of five M.I.T. scientists that is taking a novel approach, breaking down the chemistry of spider silk to duplicate it in the lab in the form typical of synthetic polymers. The next step is to determine how changes in the chemical structures affect the physical properties of the spider silk.
The wrinkle in spider webs is that they have both a soft, elastic property used in the cross lines, as well as small, hard crystallite anchors that provide peripheral support. Some parts of the silk, such as the "dragline" that a spider uses to rappel from a ceiling, are known to combine components of both.
Hammond said the ultimate goal of the project is to create a system that makes it easy and economical to produce large quantities of material with the properties of spider silk, without being dependent on the vagaries of Mother Nature.
The second step in the project is to develop an appropriate method of "spinning" the material into forms needed for specific applications. Gareth McKinley, an M.I.T. professor of mechanical engineering, heads the "spinning" part of the project. Hammond said she estimates the team is currently about halfway through a five-year effort.
Hammond said using goats, the Nexia approach, has shown positive results. But she said it appears to be expensive, which may preclude the production volumes necessary to meet widespread demand.
Nexia declined to comment, but said in a July 17 press release that it is continuing to evaluate a variety of applications. The company said it is preparing clinical data to make a pre-market approval filing to the U.S. Food and Drug Administration for surgical sutures based on its spider-silk product BioSteel.
M.I.T.'s spider silk research effort, originally launched in concert with the National Aeronautics and Space Administration, is being conducted under the aegis of the U.S. Army's Institute for Soldier Nanotechnologies, a multifaceted effort aimed at creating technology that will outfit the foot solider of the future. It was officially launched at M.I.T. on May 22 with an initial $50 million in funding from the U.S. Army.
Chemical and textiles giant E.I. DuPont de Nemours & Co. (DD) is one of the backers of the project, both financially and intellectually, said Wayne Marsh, Ph.D., a chemist and research manager at the company.
DuPont gave M.I.T. a $35 million grant in 2000, and is collaborating on research in biotechnology and materials science with the Cambridge, Mass., university.
He said DuPont tried to figure out the spider silk conundrum on its own, but dropped the research about five years ago because "we weren't able to solve it." Still, the company can contribute equipment and expertise in textile making to the M.I.T. project.
"We've said that if it makes sense we would do the next step of scale up with them," Marsh said, and provide some of DuPont's expertise and spinning equipment.
Even if the M.I.T. researchers solve only certain aspects of such a delicate problem, it could help DuPont's commercial efforts.
"We may find it has properties that go into a film, or a membrane or composite" and therefore would be a component of a final product, Marsh said.
The Army has taken a shot of its own at solving the spider silk mystery.
Steve Arcidiacono , a microbiologist and researcher at the U.S. Army Natick Labs, in Natick, Mass., said that facility worked on spider web silk research for several years but hasn't done anything on it in the last year or so as other matters have assumed priority amid the war in Iraq.
"We were able to produce fibers that were similar to the natural spider silk but not exact duplicates" and it was on a very limited level, he said.
He said his researchers used a bacterial fermentation approach to producing the spider silk like proteins and showed promise, "but the problem was the bacteria didn't make very much of it for a variety of reasons we never quite figured out," although there was enough to do some tensile tests on in the lab.
"Our initial interest in silk was for ballistic protective items, such as vests and helmets," he said.
For now, such applications appear to be "pretty far away," he said, "although we see medical uses such as micro-sutures" for surgery, as some of the first applications of such material, Arcidiacono said.
揭开蛛网之谜
世界上一批顶尖的科学家正在试图解开一个化学上的秘密：是什么东西使柔软光亮的蜘蛛网如此有力，然而却又如此轻巧？
蛛网研究人士、麻省理工学院(Massachusetts Institute of Technology)化学工程副教授保拉?哈蒙德(Paula Hammond)说，按每克重量测算，蜘蛛网的强度要胜于钢材，但又异常轻巧、富有弹性并可降解。
虽然蜘蛛网的属性早已为人熟知，但人类只是到了最近才能够复制它们。现在军方和企业界对蜘蛛网的潜在应用前景非常著迷，这些应用包括了譬如防弹衣、人体肌腱替换、医疗外科手术缝合或登山运动人士用的爬绳等各个方面。 生产合成蛛丝的尝试不胜枚举，其中之一就是成群地饲养蜘蛛。但哈蒙德说，这个办法不灵，因为蜘蛛属于占山为王式的地盘性物种并且还残食同类，这种小东西难以驯养。
另外一些研究人员则通过提取蜘蛛的脱氧核糖核酸(DNA)，将其植入山羊体内，然后从山羊奶中采集蛛丝蛋白质。加拿大蒙特利尔的公司Nexia Biotechnologies Inc. (T.NXB)就使用这种方法。该公司基于蛛丝蛋白质重组体及其'转基因山羊技术'，开发了一种名为BioSteel的产品。
蜘蛛织网时，会分泌出一种纤维性流体蛋白质，然后固化──人们仍在探索这一过程的机理。哈蒙德说，她的研究小组已经在实验室发明了'第一代'蛛丝材料。
哈蒙德领导的5位麻省理工学院科学家采用了一个新方法。他们分解蛛丝的化学成分，然后以合成聚合物的典型办法进行复制。下一步就是判定化学结构的变化如何影响蛛丝的物理性能。
蛛网别致的地方在于，在蛛丝交叉的地方有柔软且富有弹性的物质，在提供周边支撑的地方也有细小的微晶系缚物。一部分蛛丝，譬如蜘蛛从屋顶下落时使用的蛛丝，同时包含有两种成分。
哈蒙德称，她们的最终目标是建立一个体系，使大量生产蛛丝属性的材料变得容易并且能够赚钱，而不必依靠自然界的神奇力量。
该项目'纺织'部分的负责人、麻省理工学院机械工程教授格加雷思?麦金利(Gareth McKinley)说，她们的第二步是要开发合适的方法，将蛛丝似的材料'纺织成'具体应用时需要的形式。哈蒙德估计她们的5年工作计划进程已经完成了一半。
哈蒙德说，Nexia采用山羊体的方法已取得了积极的效果。但她认为这种方法代价过于昂贵，难以进行大批量生产来满足广泛的需求。
Nexia拒绝发表评论，但该公司在7月17日的新闻稿中称，公司将继续研究各种应用的可能性。公司称，正在准备临床数据，准备就其蛛丝产品BioSteel用于外科手术缝合向美国食品和药物管理局(U.S. Food and Drug Administration)提出上市前申请。
麻省理工学院的蛛丝研究计划原来是和美国国家航空及太空总署(National Aeronautics and Space Administration)一道发起的，现得到了美国陆军的军人微技术研究院(Institute for Soldier Nanotechnologies)的资助。该项目5月22日在麻省理工学院正式发起，美国陆军的首批资助资金达5,000万美元。
化工和纺织品巨头杜邦公司(E.I. DuPont de Nemours & Co., DD)的化学师和研究经理韦恩?马什(Wayne Marsh)称，杜邦也是该项目的支持者之一，该公司提供了财力和人力资助。
杜邦公司2000年向麻省理工学院提供了3,500万美元赞助，在生物科技和材料科学领域同这家位于马萨诸塞州剑桥的大学进行合作。
他说，杜邦曾试图独自揭开蛛丝之秘，但5年前放弃了这项研究，原因是他们无法解决这个难题。不过，该公司现在能够向麻省理工学院的研究项目提供设备以及在纺织技术方面的专长。
马什说，公司已表示，如果有价值，公司愿意进行下一步的批量生产工作，并提供杜邦的部分专长和纺织设备。
即便麻省理工学院的研究人员只是解决了这个复杂问题的某些方面，也将对杜邦公司将蛛丝技术商业化的努力有所帮助。
马什称，他们可能会发现某些属性可以融入薄膜或合成物中，进而可以成为最终产品的一部分。 在探究蛛丝之秘方面军方也不示弱。
美国陆军实验室Natick Labs的微生物学家和研究人员史蒂夫?阿西迪亚科诺(Steve Arcidiacono)称，他们对蛛丝的研究已经进行了几年，但过去一年多没有行动，原因是伊拉克战争使其他项目获得了优先权。
他说，他们能够制造出类似天然蛛丝的纤维，但不能完全复制，并且研究程度有限。
他表示，他们的研究人员用细菌发酵办法制造出类似于蛛丝的蛋白质，成果令人鼓舞，但问题是细菌生产的蛋白质不多，其中缘由他们也不是特别清楚，尽管他们的产品足够在实验室进行拉力测试。 他说，他们对蛛丝的最初兴趣是想将之用于防护衣和头盔等抗冲击的装备上。
阿西迪亚科诺称，尽管蛛丝已经可以初步用于外科手术缝合，但目前来看军事上的应用还很遥远。
