Video transcript: How do microneedles deliver drugs?

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October 2013

Dr Ryan Donnelly, from the School of Pharmacy at Queen's University Belfast.

Video shows scaled up model of microneedles, then Dr Donnelly shows his jelly-like microneedles to the camera

This a scale model of our micro needles. Obviously this is made out of plaster cast and is about 6 cms high normally a micro needle could be 600 micron metres high just greater than half a millimeter in height and instead of being made from plaster cast it's made from a hydrogel forming material. So this is essentially a similar material to what soft contact lens are made from so it is hard in the dry state, can penetrate the skin but it rapidly then takes in fluid from the viable skin and swells to form a more jelly like material and it's through this jelly that we can either deliver medicines or pick up bio markers and medicines that are already in the person body from monitoring purposes and if we insert these into a person's skin it feels like a cat's tongue or a little piece of Velcro or an emery board. There is no pain and no bleeding.

Video shows the traditional process of injecting using a normal needle with disposable gloves

If we consider first of all the advantages of micro needles as compared to a conventional hypodermic syringe then we have the minimally invasive nature of the micro needles so we are no longer now having a device that will cause pain and potentially bleeding and could actually be stuck into another person either on purpose or by accident so we don't have the issue of disposal that we would have with a conventional needle and syringe. If we think of micro needles as an alternative to conventional oral administration of medicine from tablets to capsules we now have the opportunity to improve the bio availability of macro molecules like peptides and proteins but also to control the administration of a whole range of drugs over several days and this could be particularly important in elderly patients for examples who are on numerous medicines and often struggle to remember to take their tablets.

Video shows the microneedles under an electronic microscope, then a print at much higher magnification showing an unused and used microneedle. Then he shows more images of the microneedles piercing the skin when in use, again, at very high magnification

It is vitally important that we are able to visualise micro needles because clearly our eye cannot see them they are on such a small scale. In this first image we see a light micro graph of our micro needles that are gold coated prior to scanning electronic microscopy imaging and we can see the individual micro structures and the base plate upon which they are formed. Our next image shows a scanning electron micrograph of a single micro needle penetrating through the stratum corneum which is the outer most barrier layer of our skin and once our micro needles are in the skin they will rapidly take up skin interstitial fluid to form these discrete hydrogel bulbs and that is what we see in our next image. So even though our micro needles become soft when inserted into skin through the uptake of fluid what we can see here is a micro needle that has been removed from the skin and this indicates that we can remove the micro needles completely intact and we do not deposit any polymeric material behind in the skin and this is what our final two images show so these are the micro needles inserted into the skin of my former phd student Martin Garland in our final image then we see a 3D rendered image of the entire array of 361 micro needles inserted into Martin's skin so we can study the depth of insertion of every single micro needle and this will be important as we follow up and try to develop methods of patient application that are reliable and can be done in the same way by every patient every time.



Produced with Queen's University Belfast

Microneedle images (c) R. Donnelly

Blood capillaries, injection and disposal videos from www.sciencephoto.com.