Studies On The Nasal Delivery Of Rotigotine Micelle-loaded Thermosensitive In Situ Gel

Objective:In this study,the dopamine agonist Rotigotine was used as a model drug to construct a polymer micelle-loaded thermosensitive gel composite system for nasal administration,in order to enhance the solubility of the drug,prolong the residence time,and increase the concentration of the drug in the brain tissue,thereby improving brain targeting.Methods:Rotigotine-loaded polymer micelles were prepared by solvent evaporation method using m PEG-PLGA as carrier.The initial concentration of polymer in organic phase,volume ratio of organic phase to water phase and drug loading ratio were investigated.Based on the particle size and encapsulation efficiency,the rotigotine polymer micelles were optimized by a single factor method.Rotigotine-loaded polymer micelles were further incorporated into poloxamer 407 and poloxamer 188 liquid gelling system by cold method.The effects of drugs and their excipients on gelation temperature were investigated.The gelation temperature was used as the index,the micelle-loaded thermosensitive gel was optimized by the star point design-effect surface method.The p H value and the rheological properties（phase transition temperature,gel strength and complex viscosity）were evaluated.The in vitro release behavior was investigated by the diffusion cell method.The rabbit nasal mucosa was used to examine the nasal mucosal permeability of the prescription.SD rats were used as the research object,and the in vivo pharmacokinetic evaluation of the rotigotine micelle nasal administration group,the micelle-loaded thermosensitive gel nasal administration group and the rotigotine solution intravenous group were conducted.The distribution of the drugs in the cerebrum,cerebellum,olfactory bulb and striatal tissue was evaluated for brain targeting of nasal administration.The stability of the preparation was investigated via influential factors test,accelerated test and centrifugation test.The nasal cilia toxicity and long-term irritation of the nasal mucosa were evaluated by the toad model and the rat mucosal tissue section.Results:The average particle size,encapsulation efficiency,and drug loading of the rotigotine-loaded polymer micelles were（88.62±1.47）nm,（93.5±0.79）%,and（19.9±0.60）%,respectively.The optimal micelle-loaded thermosensitive gel contained 22%P407 and 2%P188 with a gelation temperature of about 32.3°C and a p H of 5.186.The cumulative percent release of polymer micelles and micelle-loaded thermosensitive gels were 75.1%and 52.9%,respectively.Compared with the solution group,the cumulative release rate was slow,and the micelle-loaded thermosensitive gels had better sustained release effect.Ex vivo permeation of rotigotine solution,polymer micelles and micelle-loaded thermosensitive gel through the rabbit nasal mucosa showed that 200.06,532.60 and 393.54μg·cm^-2drug permeated after 6 h.The steady-state permeation rates of rotigotine micelles and micelle-loaded thermosensitive gels were 3.51 and 2.48 times,respectively,of the rotigotine solution.The formulation conformed to the Higuchi diffusion equation.In vivo,the MRT of the micelle and micelle-loaded thermosensitive gel nasal administration was 1.43 times and 1.79 times that of the intravenous.After nasal administration,the AUC in each brain tissue was significantly greater than that in the intravenous group（p<0.05）,the total drug concentration in the olfactory bulb is highest.The bioavailability of rotigotine micelle-loaded thermosensitive gel was 84.6%,and bioavailability in the olfactory bulb,cerebrum,cerebellum and striatum was276.6%,170.5%,166.5%and 184.4%,respectively.The drug targeting index（DTI）in each brain tissue after nasal administration was greater than 1,among them,the olfactory bulb has the best targeting.The direct transport percentage（DTP%）of the micelle-loaded thermosensitive gel in the olfactory bulb,cerebrum,cerebellum and striatum were 69.39%,50.35%,49.15%,and 54.09%,respectively.The stability test suggests that the formulation should be stored and transported at low temperature and from exposure to strong light.The preparation had no obvious damage to the cilia movement and pathological structure of rat nasal mucosa.Conclusion:In this study,the p H value and gelation temperature of the rotigotine micelle-loaded thermosensitive gels are within the nasal cavity requirement range.The preparation has a certain sustained release effect,and the permeability of the nasal mucosa was well.The drug can be directly transported to the brain through the nasal route,and it can improve the brain targeting.The drugs and excipients have no obvious side effects on the nasal cilia and rat nasal mucosa,and are safe for nasal administration.Thus,the composite system has proven to be a potential application prospect as a rotigotine nasal-brain delivery system.