温度敏感原位凝胶中药物的扩散行为温度敏感原位凝胶中药物的扩散行为

环境敏感凝胶对外界物理或化学条件的微小变化发生响应的性质在药物控制释放领域得到广泛应用.原位凝胶(in situ gel)是指高分子材料的溶液因温度1,2]、离子强度3]或pH4]的改变而在用药部位发生相转变,形成的半固体制剂.由于完美地融合了液体与凝胶制剂的优点,该药物传递系统近年来已逐步发展成为环境敏感凝胶最受瞩目的分支.

Diffusion behaviors of drugs in thermosensitive in situ gels

AimTo study the diffusion behaviors of drugs in thermosensitive in situ gels, and provide valuable information for designing such delivery systems. MethodsA free diffusion model was used to evaluate the effects of concentration, the property of drugs, as well as the gel compositions on the diffusivity of drugs. ResultsDrug transport through the aqueous channels of the gel followed Fickian mechanism, and no significant influence on the diffusivity was observed when the drug concentration was lowered from 5% to 0.25%. The diffusion coefficients of propranolol, timolol maleate, and salbutamol sulfate were 0.91, 1.32, and 3.30×10-6 cm²·s^-1, respectively. The flux of hydrophilic drug was 3.6 fold faster than that of the lipophilic one implied the latter partitioned into the hydrophobic micellar core, and consequently the diffusion was retarded. The diffusivity was decreased with increased poloxamer and sodium hyaluronate concentration, due to the distorted aqueous channels and higher microviscosity. ConclusionThe result suggested that sustained release could be achieved for the thermosensitive in situ gel by incorporating lipophilic drug or increasing polymer concentration.