Efficacy of lidocaine solid lipid nanoparticles for sciatic nerve blockade in rats

Objective To evaluate the efficacy of lidocaine solid lipid nanoparticles (L-SLNs) for sciatic nerve blockade in rats.Methods Lidocaine-loaded SLNs were prepared using high pressure homogenization.Ninety SPF male Wistar rats,weighing 220-280 g,were randomized into 6 groups (n =15 each) using a random number table:control group (group C),1％ L-SLN group (group L1-SLN),1％ lidocaine group (group L1),2％ L-SLN group (group L2-SLN),2％ lidocaine group (group L2),and blank SLN group (group SLN).In C,L1-SLN,L1,L2-SLN,L2 and SLN groups,normal saline,1％ lidocaine SLN,1％ lidocaine,2％ lidocaine SLN,2％ lidocaine and blank SLN (200 μl) were injected,respectively,around the sciatic nerve.Before sciatic nerve blockade (baseline) and at 10,20,30,60,120,180,240,300,360,420,480,540 and 600 min after blockade,the paw withdraw latency to a thermal stimulus was measured,and maximum possible effect (MPE) was calculated to reflect the degree of sensory block.Before sciatic nerve blockade and at 10,20,30,60,120 and 150 min after blockade,extensor postural thrust (EPT) of the hind limbs was detected to reflect the degree of motor block.The sciatic nerve at the injection site and the tissues around the site were obtained for observation of the pathological changes at 2 days and 1 and 4 weeks after blockade.Results Compared with the baseline value before blockade and group C,the MPE was significantly increased in at 10-30 min after blockade group L1,at 10-60 min after blockade in group L2,at 10-360 min after blockade in group L1-SLN,and at 10-540 min after blockade in group L2-SLN,and the EPT was decreased at 10-30 min after blockade in group L1,at 10-60 min after blockade in group L2 and group L1-SLN,and at 10-90 min after blockade in group L2-SLN.Compared with group L1,the MPE was significantly decreased at 10 min after blockade,no significant change was found at 20-30 min after blockade,and the MPE was increased at 60-360 min after blockade,and the EPT was increased at 10-30 min after blockade,and no significant change was found at the other time points in group L1-SLN.Compared with group L2,no significant change was found in the MPE at 10-30 min after blockade,the MPE was significantly increased at 60-540 minafter blockade,and the EPT was increased at 10-60 min after blockade,and no significant change was found at the other time points in L2-SLN group.In SLN,L1-SLN and L2-SLN groups,no pathological changes were found in the sciatic nerve at the injection site and the tissues around the site,and only mild inflammatory responses were observed.Conclusion L-SLNs can prolong the duration of block when applied for sciatic nerve blockade in rats and biocompatibility is good. Key words: Nanocapsules;  Lidocaine;  Nerve block;  Sciatic nerve