【作者】 刘娅；

【导师】 孙建军； 孔维佳；

【作者基本信息】 华中科技大学 ， 耳鼻咽喉科学， 2008， 博士

【摘要】 【目的】探索载药电极在离体环境和内耳的药代动学规律;研究该电极对人工耳蜗植入后听觉电生理的影响,评价其对内耳形态学方面的影响。【方法】内参法建立地塞米松的高效液相色谱检测方法。离体药物释放试验采用厚薄两种载有2%地塞米松的硅胶片,以人工外淋巴为释放液,模拟人类内耳液体环境进行半年内定期取样,高效液相色谱法检测药物度。在体药代动力学试验向豚鼠耳蜗植入载有2%或10%地塞米松的硅胶电极,一周内定期取外淋巴液,同法检测样品内的药物浓度。听觉电生理学研究先对豚鼠畸变产物耳声发射刺激声频率比值f2/f1进行优化,设置检测参数;然后向鼓阶植入空白电极和载有2%地塞米松的电极,检测术后半年内听性脑干反应的阈值和畸变产物耳声发射,比较两组动物术后听力的变化。组织学研究对术后耳蜗行石蜡切片,H&E、TNF-alpha染色,光镜下评价术后一月耳蜗的形态及特异性染色的强度。【结果】1.本文使用的地塞米松的高效液相色谱检测方法具有可靠性。离体药物释放试验证明半年内两种厚度的硅胶均能持续释放地塞米松,较厚硅胶所达到的药物浓度稍高于较薄硅胶,两者的释放特点符合零级代代动力学规律和Higuchi释放模式。2.在体药代动力学试验证明,两种不同浓度的地塞米松电极在耳蜗的达峰时间均为半小时,随后内耳的药物浓度迅速降低,术后1天至1周的时间内相对稳定。3.听力学研究显示听性脑干反应与畸变产物耳声发射的结果具有一致性;两组动物在电极植入后一周的时间内以出现全频急性和继发性听力下降;术后一周到半年载药电极组的听力有一定程度的恢复,而空白电极组的听力恢复不明显;此听力变化尤以8-16kHz为著。4.组织学观察发现电极植入一月后内耳的螺旋器形态较非手术耳差(P = 0.031),鼓阶内出现新生组织。听力较佳耳的螺旋器形态优于听力较差耳,耳蜗第2回的TNF-alpha染色略浅于后者;载药电极组的鼓阶内的新生组织TNF-alpha特异染色的细胞数较空白电极组少,第2回螺旋器及耳蜗外侧壁结构的特异性着色较后者浅。【结论】离体和在体条件下载药硅胶电极的释药性能具有一致性,电极能够持续释放地塞米松,载药量较多的电极在稳定期的药物浓度略高于载药量较少的电极,前者的持续释药时间将长于后者。向耳蜗内植入电极对听力有损伤作用;载有地塞米松的人工耳蜗电极对能促进术后听力的恢复。电极释放的地塞米松能抑制TNF-alpha特异的炎性细胞,减轻内耳术后的炎症反应。更多还原

【Abstract】 Aim: To study the pharmacokinetics of the drug-releasing silicone electrode in vitro and in vivo. To evaluate the effect of the drug-releasing electrode on hearing and the histological effect on the cochlea.Methods: The assessment of dexamethasone was established by high-performance liquid chromatography with internal standard. Two sizes of silicone piece containing 2% dexamethasone were used in the in vitro study, the 1 mL-chamber and 160μL-capillary were designed as releasing container, and artificial perilymph was used as releasing medium; sampling was scheduled in the duration of half year in the study in vitro. In the pharmacokinetic study in vivo, silicone electrodes containing 2% or 10% dexamethasone was implanted into the cochlea of guinea pigs; samples were taken from cochlea apex 1 week postoperatively. All the samples were analysed by high-performance liquid chromatography. Before the hearing study the stimulus ratio f2/f1 was optimized for distortion otoacoustic emission (DPOAE). Then silicone electrodes containing 2% dexamethasone or without dexamethasone were implanted into the cochlea of guinea pigs, auditory brainstem response (ABR) and DPOAE were regularly measured half year postoperatively. The results were compared with Mann Whitney U test. In the histological study, paraffin slices were prepared with the unoperated cochlea and the cochlea 1 month post operation. H&E staining and TNF-alpha staining were carried out. For assessment 2 criterions were established - the hearing level and the type of the electrode. Morphology and staining of the cochlea were classified objectively.Results: The assessment of dexamethasone by high-performance liquid chromatography was reliable. Stable drug concentration could be achieved in the in vitro study, the result from the chamber group and the capillary group was comparable, fitted well to the zero-order pharmacokinetics and the Higuchi model. In the pharmacokinetic study in vivo, the maximal concentration was achieved by both of the 2 types of silicone electrode (containing 2% or 10% dexamethasone) half hour postoperatively, then the concentration decreased rapidly; the drug concentration in the inner ear was relatively stable from the 1st day to the 1st week after surgery. The concentration of the 10% dexamethasone electrode group was a little higher than the 2% dexamethasone electrode group. In the functional study, the result of ABR and DPOAE measurement was consistent. All the implanted ears exhibited an immediate hearing loss just at the end of the operation and an increasing hearing loss within the 1st week post operation. From the 1st week to the half year the hearing level of the dexamethasone group recovered significantly, whereas the placebo group showed no significant recovery. This chagne of hearing took place throughout all the frequencies, whereas most apparent at 8-16 kHz. In the histological study there was new connective tissue in the scala tympani of the implanted cochlea, and the organ of Corti was destructed significantly compared with the unoperated cochlea (p=0.031). In the group with better hearing level, the morphology of the organ of Corti was better than that of the group with worse hearing level. In the DEXA group, the TNF-alpha expression in the cells of the new connective tissue as well as in the 2nd turn was less than that of the placebo group.Conclusion: The pharmacokinetics of the in vitro and in vivo study is consistent; the silicone electrode can steadily release dexamethasone; the electrode containing more dexamethasone can achieve the concentration a little higher than the electrode containing less dexamethasone, and the releasing time of the former is longer than the latter. Cochlear implant can induce hearing loss and the drug-releasing electrode can conserve the hearing level postoperatively. The morphology of the cochlea and the TNF-alpha staining has relationship with the hearing level. Dexamethasone can potentially reduce the TNF-alpha specific cells and alleviate the inflammation after cochlear implantation.更多还原