Towards Repairing Degenerated Intervertebral Discs using pH-Responsive Microgels

Degeneration of the intervertebral disc (DIVD) is a process that results in generation of interconnected voids within IVDs. The voids result in a loss of disc height and chronic low back pain. DIVD has a major adverse effect on society. The estimated cost of DIVD due to lost productivity in the US in 2004 was $USD 40 billion. Current spinal therapy for DIVD involves major surgical intervention with protracted recovery times. There is an urgent need for a minimally invasive DIVD treatment that restores disc height. In our 12 month feasibility study (GR/S75819/01) it was shown that injection of a pH-responsive microgel dispersion into a degenerated IVD could restore the disc height to normal values under biomechanical loads. Microgels are pH-responsive polymer colloid particles that expand when the particle charge increases. They can be triggered to form physical gels using pH within degenerated IVDs. This continuation proposal seeks to investigate the principles underpinning IVD load support by physically gelled microgels and extend the work to study covalently-linked microgel particle gels. This study seeks to deliver a set of design rules that will enable future clinical development of an injectable microgel repair system for DIVD.