Painless injection skin patches
Many medicines are administered by injection, but syringes are very costly and needles are unpleasant at the best of times. Ryan Donnelly from the School of Pharmacy at Queen's University in Belfast has come up with an alternative way to deliver injectable drugs using skin patches. He spoke to Chris Smith.
Ryan - On the surface of each of these patches we have arrays of tiny needles called micro-needles. These are less than a millimetre in height. Whenever we press them into the skin, they don't cause any pain or bleeding, but they swell in the fluid in our skins. This allows us to deliver medicines from an attached patch containing the medicine and the medicine can then be absorbed or have a local effect in the skin.
Chris - How big are these patches?
Ryan - We can make them from 1 square centimetre to the size of a postage stamp, right up to 25 square centimetres, depending on the medicine we may wish to deliver and how much we want to deliver.
Chris - What sorts of things can you put on to the patches? Will they take any kinds of medicines or vaccinations?
Ryan - By and large, they will. Once we modify their properties to tailor them to the medicine we wish to deliver. Obviously, there is a lot of interest at the minute about actually making vaccination safer in the developing world. There are around about 2 million healthcare workers in the world injured per year by needlestick injuries. Very often, needles aren't disposed of properly, which can cause problems for people just by coming into contact with them and whatever diseases might be on them from other people. So, we now have something that is self-disabling in that when it's pressed into the skin, it swells, and it becomes soft. So that when we take it out of the person's skin, it could never be stuck into somebody else.
Chris - Can it work in reverse as well because, you mentioned people getting needlestick injuries - one of the reasons needles are also used is to take blood out of people. Can your patches as well as putting drugs into people take fluid out of people for analysis?
Ryan - Yes. What's known is that the concentration of medicines in our fluid of our skin is imbalanced with the concentration in our blood. And because our micro-needles work by swelling in this fluid, we also extract whatever is in the fluid. So, it could be a way of doing monitoring without taking blood from a person and this might be particularly useful in premature babies, for example, who are generally on a lot of medicines, need a lot of monitoring, but have a limited volume of blood, and very fragile bodies.
Chris - So, you better tell us, what are these things made of, if you can, without blowing your patent?
Ryan - Sure. We have made these micro-needles from a polymer, plastic type material. It's actually the same stuff as is used in the adhesive in some toothpaste to keep the active ingredients on your teeth for longer, and also in denture adhesives.
Chris - How do you actually make the needles? Tell us about the structure of them.
Ryan - Yes. So, what we do is we take a little mould that we've used a laser to engineer. So, the laser drills holes in a piece of silicon and we then take a gel that we've made from this denture adhesive material. We cast it into the mould by either using a vacuum or a centrifuge and then allow the water to dry off. That then forms the micro-needles which are hard in the dry state, but rapidly taken fluid to form a jelly-like material, very similar to a soft contact lens.
Chris - And if I wanted to impregnate them with a vaccine or something, how would you do that?
Ryan - What we would do is we would simply take a conventional and flexible patch like the transdermal nicotine patches, for example, and we would put our vaccine or our medicine into that and then simply apply that to the upper surface of the micro-needles. Such that when they swell, they open up a pathway for the medicine to move down through into the skin where it can be either absorbed by the circulation in the skin or target the immune presenting cells in the skin, and therefore, have a potent immune response for vaccination purposes.
Chris - And does it work? Have you got some tests showing that you can immunise people with this?
Ryan - We have evaluated it in a range of different pre-clinical studies, including suitable animal models, and we've done safety studies in people. All of these investigations indicate that this would be a technology that will have many benefits. The key point of course is to be able to go from a lab scale to an industrial scale. I'm very pleased to tell you that the Biotechnology and Biological Sciences Research Council have recently awarded us 3 quarters of a million pounds to scale up the manufacture of the micro-needles.