Screws with a Twist

Screws with a Twist

Secrets of the Silkworm: Did you know that the silkworm was domesticated in China over 5,000 years ago? Legend has it that the Empress Lei Zhu was drinking tea under a tree when a cocoon fell into the hot beverage, unraveling silken threads to reveal the Bombyx caterpillar within. Silk making was a deeply guarded secret until 550 AD, until Christian monks successfully smuggled silkworms out of China in a hollow stick and introduced them to the rest of the world. Today, there are thousands of genetically inbred and engineered strains, all completely dependent on humans for survival! 

From Steel to Silk: Fractured bones are often held in place by metal screws and plates until they heal. Removing the metal carries unnecessary risks, which can be averted using biocompatible materials that are naturally absorbed into the body over time. Silk is strong, stable to high heat of sterilization and can be fashioned into “self-tapping” surgical screws that have been successfully tested in rats. The silk screws are “radiolucent” or invisible to x-rays, allowing the fracture to be monitored post-operation, without the impedance of metal. Best of all, silk protein is digested by natural enzymes and resorbed into the body within 4-8 weeks. Researchers hope to use silk screws in facial fractures, which number in several hundred thousand each year. 

Bench to Body: (1) Fill test tube with silk solution then freeze dry. (2) Use scissors or a blender to cut into small pieces. (3) Dissolve pieces in 1,1,1,3,3,3 hexafluoro-2-propanol (HFIP) in a syringe. (4) Inject dissolved silk into bone plate or screw blank moulds. (5) Place molds in methanol for 3–4 days (to convert silk protein into β-sheets). (6) Remove and allow to dry (fume hood for 1 week then 60 °C oven for 5 days), then autoclave for stability. (8) Machine using a mill, lathe or die to obtain desired geometry. Almost DIY, right? 🙂

REF: Perrone et al., 2014 Nature Communications

● Gary Ray R describes a different kind of biodegradable screw made of an iron alloy-ceramic composite. This material could be used for shoulder surgeries and degrades at a slower rate over 1-2 years.


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91 Responses to Screws with a Twist

  1. Surendra Rao says:

    Nice one thanks for information

  2. Rajini Rao says:

    Colin MacRae thanks! Wonderful  possibilities with silk. From your link: We can use silk as a substrate with materials such as magnesium and gold to generate a set of devices that are edible while being electronically active. This allows for edible RFID technologies that can be interfaced to food.

  3. Wow, great post, Rajini Rao! I’m inspired now – gotta get me some HFIP! Oh, and a fume hood. And an autoclave… Hey, I love collecting tools!

  4. Rajini Rao says:

    David Archer I have a fume hood and autoclave in my lab that you can borrow 🙂

  5. Rajini Rao Excellent! We could work out a swap maybe – I have a table saw (and a dado blade)… whaddaya think?

  6. Rajini Rao says:

    What a deal, David Archer ! 🙂

    One never knows when I may need a table saw handy, right? I’ve no idea what a dado blade is?

  7. Rajini Rao It’s a set of blades and spacer plates of a range of different thicknesses; precisely variable-width grooves in wood being the result.

    The first tests of silk screws have been done on rats? Those would be very, very tiny screws, with incredibly fine threads!

  8. Rajini Rao says:

    David Archer good to know, thanks for the explanation. Yes, these are tiny screws! The image shows an electron micrograph of one of them, the other is also a microscopic image of a tissue section with an embedded silk screw. I guess we should add a microscope to our DIY lab 🙂 

  9. Rajini Rao says:

    Words to live by, Peter Lindelauf .

    I won’t ask about your undergarments 🙂

  10. Rajini Rao says:

    OK, since you started it..have you heard about the two silkworms who had a race? They ended in a tie. 

  11. Gary Ray R says:

    Thanks for the reference Rajini Rao 

    I also did a post last year on; 

    Silkworms Genetically Altered to Produce Spider Silk

    I do like biomaterials.  

  12. I think this is within the grasp of the diy-er with a corporate mailing address. Autoclaves can be found in tattoo, piercing and body modification shops.

  13. Good information nice I have worked with silk fabric u know what they called for that dupion silk

  14. Dissolving silk into solution and casting it into shapes is new to me. Very interesting Rajini!

    I wish the titanium hardware spanning a three-level fusion in my back would melt away… 🙂

  15. Chad Haney says:

    Great post Rajini Rao, Silk has been used for sutures for a long time. What caught my eye about your post is that there are special enzymes to degrade the silk screws but silk sutures are non-absorbable. Hmm, I’ll have to investigate later. Back to grant writing for me.

  16. Rajini Rao says:

    Chad Haney good point..after all, silk protein (fibroin) should be degradable by enzymes. Wiki says, “Non-absorbable sutures are made of special silk or the synthetics polypropylene, polyester or nylon. Stainless steel wires are commonly used in orthopedic surgery and for sternal closure in cardiac surgery.” So I guess the answer resides in what is “special silk”. 

  17. Rajini Rao says:

    GOPIKRIN GOPS dupioni silk is gorgeous! I know that it is made with two (or more) cocoons, and has a shimmery uneven effect. 

  18. Chad Haney says:

    Maybe there are silkworms that eat McDonald’s special sauce and make special silk.

  19. Rajini Rao says:

    Chad Haney hah, that reminds me of the burger experiment..the one that never grew mold. 

  20. Rajini Rao says:

    Peter Lindelauf  pun silk is fantastic material. 

  21. Rajini Rao says:

    David Andrews that must be painful! Here’s wishing for progress in bioengineering bone.

  22. Screws from Silk are wow for me. In future, I think new type of engineering profession will evolve – Body Engineers 👍

  23. Chad Haney says:

    Rajini Rao the burger that didn’t mold was another myth that needed busting. Too many people didn’t understand what desiccation is.

  24. Rajini Rao says:

    Thanks for the link, Gary Ray R . What a brilliant idea to bioengineer spider silk into silkworms. Apparently it is really hard to “farm” spiders for their silk. 

  25. Rajini Rao says:

    Mandeep Singh body engineering sounds cool! We have biomedical engineering now, which is hugely popular at the undergraduate and PhD level. It’s all about engineering body parts from heart valves to robotic arms. 

  26. Chad Haney Exactly – the non-molding burger myth incorporates a kind of useless “magical thinking” about food. Which lives on in the GMO debate…  >..<

    OTOH, I once left a bagged and sealed half-loaf of Wonderbread on a sunny south windowsill for a week, and … nothing happened to it. It still appeared “fresh.”

  27. Chad Haney says:

    I don’t recommend biomedical engineering as an undergraduate degree. It’s too broad and won’t give you a strong foundation to build on. It’s really more useful as a graduate degree. Of course I’m biased because that’s what I did. I’m not just screwing with you.

  28. Rajini Rao says:

    I trust you not to spin an unlikely yarn, Chad Haney . 

  29. Rajini Rao says:

    David Archer my daughter read somewhere that bread goes stale faster in the refrigerator. Of course, I don’t store my bread in the fridge, but I wonder why that’s bad. 

  30. Chad Haney says:

    Rajini Rao, I read that too. So I store bread in the freezer and take out what I need a day or two before. Otherwise, some of the really nice bread from the bakery gets moldy in a few days before I can stuff it all into my face.

  31. Rajini Rao says:

    It’s only Neurospora crassa. Picking out the moldy stuff should be safe, as long as we get past the icky factor 🙂

  32. I knew that silk was a strong and versatile protein, but I had no idea it could be formed into a hard penetrator object like a screw. Thanks Rajini Rao !

  33. Gary Ray R says:

    I had to go look up bread getting stale faster in the fridge and these two sites seemed to have the best explanations.


    When heated up in the presence of moisture or water molecules, for instance placing the bread dough in the oven, the starch molecules weaken and allow water molecules to enter, or get in between the chains of the sugar molecules and join with them.  This swells the starch granule and begins to soften it up, making it oh so warm and squishy!  In the case of bread dough, the moisture can come from two sources, either the wheat protein in the bread itself or the water added to the mixture that makes up the dough.  Once cooling begins, the moment you take it out of the oven, the process begins to reverse itself and the starch molecules begin to “dry out” or crystallize and harden again, a process known as retrogradation.

    Why faster in the fridge?

    The leading theory is that the dehydration reaction, condensation, is the main mediator in the dehydration process in this case.  Whatever the mediator, the cause of the staleness is the same; water molecules detach themselves from the starch molecules and the starch molecules begin to take their original shape and harden again.  The cool temperatures of the refrigerator make the dehydration process happen more quickly, specifically, about six times as fast via the process listed above.

    Bread goes stale about six times faster in the refrigerator then when kept at room temperature

    Does Refrigeration Really Ruin Bread?

  34. Rajini Rao says:

    Six times faster! I’m glad that I have a nice bread bin on the kitchen counter top Gary Ray R . Thanks for figuring this out for us. Checking out your links now 🙂

  35. Rajini Rao says:

    Peter Lindelauf that’s a question worth pundering, I won’t beat around the mulberry bush there. 

  36. Refrigeration by nature is desiccating. Any moisture that comes in contact with the coils is removed from the environment

  37. Mary T says:

    Wonderful post, Rajini Rao :).  I shouldn’t tell this on myself, but I usually have eaten the whole loaf of bread before I have to make a decision about how to store it!

  38. Rajini Rao says:

    That’s the best solution Mara Rose 😀

  39. Rajini Rao says:

    You mean ♫ pupa goes the wee silk ♫ Peter Lindelauf ?

  40. Rajini Rao says:

    Peter Lindelauf I went down the worm hole with that one, and looked up Mulberry Bush on Wiki. Apparently, “a variant of this rhyme is Nuts in May” which seems appropriate for us, don’t you think? 

  41. Won’t there be an immune reaction triggered by the silk protein?

  42. Chad Haney says:

    Johannes Riecke, silk has been used in sutures for a long time. No immune reaction for most people.

  43. Chad Haney says:

    Peter Lindelauf, our neighbor’s have a mulberry tree. I’m not a big fan because they make a mess and Ana thinks it’s her job to eat all the mulberries on our side of the fence.

  44. Chad Haney oh, I see. Thx

  45. Rajini Rao says:

    Johannes Riecke the paper said that the silk screws were biocompatible and had minimum inflammatory reaction. Our library link is down at the moment, or I would have looked up the paper again to see if they had anything more to say about this. 

  46. The way to un-stale bread is to microwave it over a cup of water.

    Or if you are working with buns and so on, take a paper napkin, wet it and lay in on top and microwave.

    Hot steamy buns… Yummy… 😛

  47. Chad Haney says:

    Peter Lindelauf, they taste pretty good too. I just don’t want my dog eating 4 handfuls.

  48. Rajini Rao says:

    Thanks for that cut and dried method, Irreverent Monk 🙂 Will give it a try.

  49. Mara Rose

    Ahh, another baked goods aficionado! When I was a kid and visited my grandparent in Taiwan – they lived 2 doors away from a bakery. Everyday, 4pm, I’d be there, spending my money… 🙂

  50. Chad Haney says:

    Rajini Rao and Johannes Riecke, the authors don’t even use the word immune in the article. So I think there is a mild inflammatory response for some people but no true immune response, i.e., anaphylaxis.

  51. Paul M says:

    This has been a really good thread.

  52. Chad Haney says:

    You might even say it’s silky smooth.

  53. Richard Lee says:

    Rajini Rao Love this article and hope the silk can be used more effectively to cure people……or let the spider to bite patients as the self-cure of spider-man….   🙂

  54. Rajini Rao says:

    Perhaps one day science will be stranger than fiction Richard Lee, but I’ll pass on the bite for now 😀

  55. Always intriguing, the repurposing of ancient materials and technologies. As the saying goes, there’s no spool like an old spool!

  56. This is a little annoying. I’ve had hundreds of bugs drop into my coffee over the years, and I haven’t discovered a useful fiber yet. 😦

    The bit about making surgical screws from silk is amazing. From luxury fabric to medical hardware is a pretty wide range of utility.

  57. Rajini Rao says:

    Haha, J Bennett ! You know I’m a dedicated scientist but I’d still like my coffee sans bugs 🙂

  58. korinエミ says:

    thanks for your post

  59. Larry Mayer says:

    Might be too early to rule out Anna, Phil Axis, as silk allergies (to fabric) are known.

  60. Good!!!!! : I don’t know even about them much

  61. Domesticated is an interesting way of saying exploited and manipulated, and further exploited. It is rather disgusting what happens to these creatures.

  62. Of course, but we must protected them, is our responsability.

  63. Rajini Rao says:

    deborah rabbit white Domestication is to “tame an animal, especially by generations of breeding, to live in close association with human beings as a pet or work animal and usually creating a dependency so that the animal loses its ability to live in the wild”. Humans have been domesticating animals for thousands of years. We have all benefitted from this practice in innumerable ways that we take for granted. It’s likely that the clothes we wear, the food we eat, and the comforts we enjoy can be traced back to the exploitation of many animals, including humans. 

  64. Richard Healy z_8!_$8,”uux

  65. Yes, I know.

     It is that I strive towards being an abolitionist in animal rights, which does not exclude humans, as we are animals. I do not see any reason for the exploitation of any being to suit our needs especially when we are (assuming so)  the more intelligent species, and can change our habits, especially when we see the error (as we have done several times in history), and can come up with better solutions.

     I do not expect many to understand my position, and even expect many to scoff and laugh at my position. That is fine. I am ok with that.

     I mention what I see when I see it because if I do not, I feel complicit in the perpetuation of the problematic ideologies.

  66. Mary T says:

    Threadjack:  Speaking of mulberries….In Central Asia, mulberries are used to make Arak, the local moonshine, which is then kept in petrol containers and offered to guests mixed in Tang, to mask the awful taste.  Peter Lindelauf Just a thought for your extra mulberries, ha :).

  67. Chad Haney says:

    So deborah rabbit white, do you forsake all modern medicine? If you or a loved one is ill and require surgery or medicine what do you do? Modern medicine cannot move forward without animal research. Modern medicine is built upon decades of research that involves animals, including humans. We go through extraordinary measures to work as humanely as possible. Research animals are often treated better than humans in the third world.

  68. Rajini Rao says:

    deborah rabbit white I am not laughing or scoffing at your position because I love animals too, as do most on this thread, and we will do everything to minimize pain and suffering. The problem with your comment is that it it is out of context. I don’t know you: perhaps you are a life long vegan who does not wear leather, owns no animal products in your home, has vinyl covers on your car seats, has never been vaccinated, rejects modern medicine, does not eat candy colored with cochineal dyes, etc. (I can come up with a hundred more!). But if not, then picking on the silk worm for your grandstanding would not be logical. Yes, it is cruel that pupae are destroyed and larvae killed to make silk, so your point is well-taken.

    However, I do write about science and if you are squeamish about anything I write, I suggest that you don’t read my posts in the future so you don’t continue to feel badly about such topics.  

  69. So, You are writing that it is wrong of me to mention it?

    The things mentioned above sound a like judgement passing. I am not passing judgment. just as your posts are illuminating and educating, I am only pointing out more facts.

    I was not grandstanding.

     I tried to explain that I just feel I have to mention what I see when I see it.

    I do it on everything in my stream, I was truly not picking on anything.

     I am not for one minute unaware of the history of other being use, I know very well what is in vaccinations, make up, and foods, products in general, and especially since having a child I spend a great deal of time researching nearly everything she touches or eats, and I do not own a car, and have not for 10 years. Not because I am superior but because it works for me so far, to be able to do without.

     I also meant that when my position is scoffed or laughed at that I truly am not bothered as I do not expect everyone to understand and/or feel the same. It took a very long time for me to be where I am.

     Once upon a time I was a biology major; I brain tanned hides, I knew how to boil food from the inside out stomach of an ungulate, I grew up with horn burning, tail docking, gelding, butchering. I am not sheltered.  I am not perfect living plant based, doesn’t mean elitism, or perfection, it means doing the best that one can do. Am I hypocrite? Likely at sometime or another. Who has not been?

     I meant no harm, I mean no harm. I suggested that maybe there are other ways rather than continuing using of other beings, especially in light of new science showing every day more and more creature sentience, and ability to suffer; which  know is also discovered through animal exploitation.

    We can not change what has been done, we can change what we will do.

  70. great explanation & details.. thanks

  71. Rabbia Ahsan says:

    Rajini Rao Great output from you.. Impressive

  72. Praful Mehta says:

    thanks friend good information

  73. HaDi Kazemi says:

    Very beautifull you say it, good luck.

  74. Great one Rajini. Being an orthopod I look forward to the day this is practical. If the industry allows that is!

  75. Rajini Rao says:

    I hope so too, Deva 🙂 Thanks for doing what you do, Doc! 

  76. Very interesting Rajiniji

  77. Nice history, and thank you for silk make information…

  78. Good collection..thanks for sharing

  79. Valuable messages. Thanks Rajini Rao

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