3D Printed Pharmacological Implants

I recently got a 3D printer, and so now I've turned into one of those goons who makes a lot of plastic tchotchkes. While researching the IR transparencies of various 3D printer filaments, I found out that you can get PCL filament (https://www.fabbaloo.com/blog/2016/6/24/the-unusual-properties-of-pcl-3d-printer-filament). PCL (polycaprolactone) is a biodegradable polyester (previously commercially available as polymorph). It melts around 60C, so it prints at a relatively low temperature.

Where this gets more interesting is that PLC degrades harmlessly in the body. It breaks into subunits of hydroxylcaproic acid, which is converted to acetyl-CoA, enters the citric acid cycle, and is excreted (https://openwetware.org/wiki/PCL_Biomaterials_by_Katie_Kwan).

There has already been some work in building implantable PrEP delivery systems (http://www.croiconference.org/sessions/long-acting-biodegradable-subcutaneous-implant-tenofovir-hiv-prep). My thinking on the matter is that a good 3D printer should be able to print an implant, either with containers inside it with the drug in them, or using filament that has been pre-mixed with the drug. Depending on the properties of the drug, either the PLC could be melted and mixed with the drug, or they could both be dissolved in e.g. chloroform and then the solvent evaporated off. By changing the shape and density of the implant, the release rate can be altered, and there ends up being no need to remove it, as it gets naturally degraded.

It could also be used to print a "sabot" for something that is an awkward shape to implant, and then gradually decay away, leaving the implant in place. In combination with titanium oxide, it can also be used to produce bioactive surfaces that promote cell attachment, particularly for bone cells. However, that work[1] was done with electrospinning rather than 3D printing.

[1] Antibacterial and Bioactive Surface Modifications of Titanium Implants by PCL/TiO 2 Nanocomposite Coatings
A. Sandeep Kranthi Kiran, T.S. Sampath Kumar 1, Rutvi Sanghavi, Mukesh Doble, and Seeram Ramakrishna

Comments

  • I don't know what to call it.,, resolution? But basically, how small of a detail can you print? Could you make like nm size pores?
  • With my printer, I certainly couldn't print nm features, and as it decayed, they'd open up anyway. Home 3D printers are more on the 0.5mm resolution level.

    I'd be going more for a bulk object, just solid material that released as it dissolved, and possibly designed to be put in with a large needle.
  • edited November 12
    In prototyping scenarios, I often use 3D printing to create enclosures for electronics. PCL could be used as a casing for implantable electronic assemblies to soften edges (although the underlying components would need to be biocompatible, considering the PCL degrades).

    I've also read about attempts to create conductive polymers with POSS/PLC inundated with ~5% graphene by weight:
    [https://www.sciencedirect.com/science/article/pii/S0021979714005773].

    A material with those properties (that is easier to make) could be used to make something like implantable PCB traces. It would be difficult to implant (you'd need something like an endoscope) but the traces could be used to connect energy harvesting devices in active areas of the body:
    [https://www.sciencedirect.com/science/article/pii/S2352431616301092]
    With aesthetic or functional implants in another part of the body.

    Potential issues:
    >difficulty
    >graphene *might* be toxic
    >3D printed filament is porous, which may invite infection (especially considering you can't autoclave and it might react with alcohol)

    Fun to think about, though. Nice topic.
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