Magnetic nanogel polymer of bupivacaine for ankle block in rats

INTRODUCTION: In an effort of designing an alternative method for local nerve block, we demonstrated the possibility of inducing ankle block in the rat with intravenous (IV) injection of magnetic nanoparticles conjugated bupivacaine and application of a magnet at the ankle. METHODS: The anaesthetic effect of magnet-directed bupivacaine-associated MNPs (NIPAAM-MAA-bupivacaine) was tested in rat using paw withdrawal latencies from thermal stimuli on the hind paw. Thirteen (13) experimental animals were grouped into two; untreated left hind paw (control group) and test group with treated right hind paw. The morphology of the synthesised nanogel was analysed using scanning electron micrograph (SEM), chemical characterisation using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) and finally the in vivo drug release using UV spectroscopy. RESULTS: UV spectroscopy result show that, at 37 °C a sharp increase was observed from 24-72 h (40-75%) cumulative drug release at pH 5.3, a steady increase from 21-60% and 20-40% at pH 6.8 and 7.4m respectively. At 43 °C, a steady increase was observed at the three pH, 37-72%, 20-35% and 10-19% at pH 5.3, 6.8 and 7.4, respectively. It was shown also that drug release at higher pH (6.8 and 7.4) does not become significantly faster when temperature is high, compared to the release at a pH of 5.3. This depicts that the decreasing pH has more impact on the speed of the release of drug than increasing temperature. NMR and FTIR results displayed a comparable chemical structure as expected. The NMR peak displayed high purity of the final product. Morphology using SEM showed that the nanocomposite size is slightly greater than that of the nanogel, and the nanocomposite particles are nearly mono dispersed. Paw withdrawal latency highest peak of 15% was observed for NG/PU/30 at 40hours, and lowest peak for NG/30 at 50 h for the left paw. Group BU0.15 at 30 h shows the highest peak (20%) and NG/30 at 120 h shows the lowest peak for the right treated paw, which is significantly difference from the untreated left paw group (p< 0.0001). However, there wasn't a significant difference amongst NG/30, NG/Pub/15, or NG/Pub/60. CONCLUSIONS: The current study verifies the findings that we can induce ankle block in rat through IV injection administration of NIPAAM-MAA-bupivacaine complexes and the application of magnet at the ankle. We however suggest a lower temperature and pH for optimum release of this nanoanaesthetics, there is a probability of translating this mechanism to clinical practise.