Technology for more controlled drug delivery could be produced hundreds of times faster than with existing methods thanks to new research.
Scientists at Cambridge University have developed a faster process for manufacturing microcapsules — tiny spheres filled with drugs, pesticides or other substances — that also enables more precise control over when their contents are released.
The researchers have used microfluidics — where chemicals are combined in tiny sub-millimetre channels — to create droplets of a mixture that spontaneously assembles into capsules. These can then be broken down with light, heat or changes in pH.
‘Microfluidics has a very high frequency of generating those droplets and therefore capsules,’ PhD student Jing Zhang, lead author on the research, told The Engineer.
‘Currently I’ve only been doing a frequency of 300 to 3,000 droplets per second but it could go up to 100,000 droplets per second easily.’ Conventional methods produce around a couple of hundred microcapsules per second, she added.
Microcapsules are used to slowly release drugs inside the body, disperse pesticides over crops, add flavours or nutrients to food and even to release sealants in manufacturing processes.
The shell of the capsules either degrades over time or is broken down mechanically to release the contents. But the capsules produced through Cambridge’s method are more susceptible to other stimuli and so the release can be coordinated.
This could be particularly useful in manufacturing complex structures such as aircraft, where sealants usually need to be applied to parts one small area at a time to ensure a precise enough fit, said Zhang. ‘Potentially we could apply a signal and all the glue would be released in one go.’
The method could also make it easier to encapsulate biological cells without damaging them because, instead of being inserted into a capsule, the shell is built around them.
Traditional microcapsule shells require physical force to break on demand because of the stronger covalent bonds between their molecules. In the new capsules they are joined with weaker hydrogen bonds that are more susceptible to other stimuli.
To create the capsules, the microfluidic system mixes oil and water to produce thousands of water droplets all the same size.
The contents of the capsule and chemicals that form its shell are dissolved in the droplet and spontaneously assemble at the interface between the water and the oil.
The shell itself is constructed from barrel-shaped molecules containing a copolymer and a gold nanoparticle. The specific chemicals used create a more stable structure than previous designs but separate when heat or light are applied, degrading the shell.
The research group, under Prof Chris Abell and Dr Oren Scherman in the Department of Chemistry, are now talking to potential industrial users of the microcapsules to determine how they could be manufactured for specific applications.