Injectable Microgel Particles Could Enhance Tissue Repair

Building on recent research into doubly crosslinked microgels (DX microgels), scientists at the University of Manchester (UK) have developed a new class of DX microgels that are pH responsive. By linking these microgel particles together, the researchers believe that the resulting biomaterial could have application in minimally invasive soft- and load-bearing tissue repair. 

To produce the swellable, nanoscopic polymer particles, the researchers covalently linked pH-responsive singly crosslinked microgel particles together. According to the related abstract in the journal Soft Matter, "pH-triggered swelling of concentrated dispersions and free-radical coupling of the vinyl groups was used to prepare the DX microgels. The relationships between DX microgel composition and mechanical properties are investigated using dynamic rheology and swelling experiments. The DX microgels had storage modulus values of up to 20 kPa at a particle volume fraction (?_p) of 0.10. The yield strains (?*) could be varied between 5 and 65%. The ability to tune the mechanical properties of the DX microgels using the degree of functionalisation of the parent GM-functionalised microgel, ?_p and pH is demonstrated. We show that control of intra- and inter-particle crosslinking can be achieved using preparation conditions. The results are explained using a general relationship between the storage modulus and ?*."

This experiment has yielded the ability to link microgel particles together to form durable, elastic gels that can sustain permanent changes without fracturing. The resulting biomaterials have improved mechanical properties compared with the first generation of DX microgels as well, according to the researchers. They also demonstrate a long-term durability that is necessary for implantable use. 

Because of these features, the injectable microgels show promise for use in minimally invasive tissue repair, notably for treating degeneration of the intervertebral disc. "Degeneration of the intervertebral disc results in chronic back pain, which costs the country billions of pounds per anum and causes untold misery for sufferers and their families," says Tony Freemont, head of research at the school of biomedicine and coauthor of the paper. "We have been working for 25 years to identify methods for treating degeneration of the intervertebral disc."