Brain-targeted Nasal Temperature-sensitive In Situ Hydrogels Of Tetrandrine For Treatment Of Rat Brain Injury Induced By Microwave

Objective:To prepare the nasal temperature-sensitive in situ hydrogels?ISGs?of tetrandrine for the treatment of rats with brain damage induced by microwave.Methods:Tetrandrine dissolved well in aqueous solution of pH 5.0-5.5.Poloxamer407 and 188 were as the ISG matrix.Phase transition temperature and gelation time were used to optimize the formulation.And the best penetration enhancer was evaluated by the transdermal test with isolated sheep nasal mucosa.The properties such as viscosity,rheology and in vitro release were evaluated,and the release mechanism of the optimal formulation was fitted with different mathematics model.The ciliary toxicity of tetrandrine ISGs was investigated by oscillation of toad palate mucosa in vitro.Rats model of brain injury induced by microwave was established.The therapeutic effects of tetrandrine ISGs were evaluated by behavioral study,pathological examination based on HE slices and ultrathin sections.The effect of tetrandrine ISGs on the mRNA expression of calcium channel subtype was investigated by qPCR.Brain targeting index?BTI?was calculated by pharmacokinetics and brain tissue distribution using liquid chromatography-mass spectrometry?LC-MS?,and the brain targeting of nasal ISGs was further verified by the small animal in vivo imaging.Results:The content determination of tetrandrine was established by HPLC.And the optimal formulation of tetrandrine ISGs included 24%Poloxamer 407,4%Poloxamer 188,2%HP-?-CD as the best penetration enhancer and the final adjustment of pH is 5-5.5.In nasal cavity,the adhesion of ISGs with nasal mucosa is favorable for drug absorption.Release of tetrandrine ISGs in vitro was in accordance with the Higuchi equation and the stability was good.Viscosity modulus of tetrandrine ISGs plays a dominant role at low temperature and it behaves as fluid state.Phase transition can be observed at nasal temperature,showing a semisolid gel state.The ciliary toxicity test of toad palate in vitro proved that the nasal preparation had no ciliary toxicity.Tetrandrine ISGs of 10,20 mg/kg could significantly shorten the escape latency,increase the number of crossings.In the open field test,tetrandrine ISGs of 10,20 mg/kg could significantly increase the total movement distance in the arena,average velocity,and the ratio of central distance to total distance.Behavioral experiments showed that tetrandrine ameliorated the impairment of spatial memory and spontaneous exploratory behavior caused by microwave.Tetrandrine ISGs of 10,20 mg/kg can significantly improve the damage of hippocampal neurons,synapses and blood vessels induced by microwave.Tetrandrine may exert its pharmacodynamics by inhibiting the expression of the mRNA of Cav1.2,Cav1.3,Cav2.2and Cav2.3.Compared with intragastric?i.g.?,intranasal?i.n.?administration has a shorter peak time and a lower bioavailability with T_max of 8.4±0.89 h for i.g.and 4.8±1.09 h for i.n.BTI of nasal administration was 2.26.In vivo imaging of small animals further demonstrates that the nasal temperature-sensitive ISGs can achieve brain targeting.Conclusion:The formulation and preparation technology of tetrandrine-loaded temperature-sensitive nasal ISGs are reasonable,safe,stable and brain-targeting,which provide a new choice for the treatment of brain injury caused by microwave.