Preparation Of Icariin/Tio₂ Nanotube Composite Coating On Pure Titanium Surface And Drug-release Study

Objective:To improve the implant-osseointegration ability, the study formed the TiO₂ nanotubes by anodic oxidation and loaded the Chinese medicine with the advantage of bone induction to prepare the icariin/TiO₂ nanotube composite coating, then studied the drug-loading and drug-release kinetics to fabricate the excellent slow eluting drug/TiO₂ nanotube coatingMethods:1. After the preparation, the pure Ti was divided into pure Ti（PT） group and TiO₂ nanotube （NT） group. NT group was dealt with anodic oxidation. Selecting 5 samples from PT group and NT group, then observing the surface characteristic. The field-emission scanning electron microscopy（SEM）was used to analyse the surface topography. The atomic force microscopy（AFM） was used to quantify the surface roughness. The surface free energy was tested by the contact angle measuring device.2. Choosing 20 samples from PT group and NT group. The samples were soaked in icariin solutions with two different concentrations （10-3 mpl/ml and 2×10-3mol/ml）,then the samples were denoted as PT-10-3 group （10 samples）、PT-2×10-3 group （10 samples）、NT-10-3 group（10 samples）、NT-2×10-3 group（10 samples）. SEM was used to analyse the surface topography of the four groups.3. Selecting 5 samples from each （PT-10-3、PT-2×10-3、NT-10-3、NT-2×10-3）group. The samples were immersed in the PBS solution. The rinsing fluid was collected at the fast release stage （4 hours） at the interval of each hour and the slow release stage （14 days） at the interval of each day. The icariin concentrations were tested by high performance liquid chromatography. Later, the accumulative release amount curve and the accumulative release percentage curve were drawn to test loading and release characteristics.4. 15 samples were chosen from NT group and divided into icariin/TiO₂ nanotube （NT-ICA） group, mixture of icariin and Lactic-co-Glycolic Acid into TiO₂ nanotube （mixture PLGA/ICA-NT） group, coverage PLGA on the top of the film of icariin/ TiO₂ nanotube （coverage PLGA/ICA-NT） group. The loading and release characteristics of icariin were tested on each group.Results:1. The SEM images presented that PT showed irregularly smooth surface without any special structure. The NT layer showed uniformly controllable nanotubes with the diameter of 80 ± 10 nm. The AFM resulted that the roughness of PT group was 248.0 ±41.4nm,lower than that of NT group（405.8+53.6nm）（P<0.05）. The contact angle of NT group was 15.8 ± 4.2° , lower than that of PT group （46.3 ±5.4°）（P<0.05）. The NT had higher hydrophilicity.2. SEM images of PT-10-3、PT-2×10-3、NT-10-3 and NT-2×10-3 showed: The icariin loaded on Ti surface is less and was distributed like particles. While the TiO₂ nanotubes loaded more icariin and the icariin was distributed like gobbet. In addition,compared with the icariin/TiO₂ nanotube group soaked in the lower concentrated solution （NT-10-3 group）, more icarrin on the NT-2×10-3 group was uniformly distributed and could incorporate into nanotubes.3. The accumulative release amount curves of icariin-loaded nanotube groups （NT-10-3 and NT-2×10-3） were higher than that of icariin-loaded Ti groups （PT-10-3 and PT-2×10-3） in the initial 4 hours （burst release phase） and 14 days （entire release phase）. Hence, the nanotubes had greater loading capacity than the pure Ti. In the icariin-loaded nanotube groups, the NT-2×10-3 group showed higher accumulative release amount than that of NT-10-3 group and had greater loading capacity. Compared with icariin-loaded Ti groups （PT-10-3 and PT-2×10-3）, the icariin-loaded nanotube groups （NT-10-3 and NT-2×10-3） showed lower release speed and extending the release time. The characteristics were obvious in the burst release phase. The release time of NT-2×10-3 group was 9 days, longer than that of NT-10-3 group（6 days）. Therefore, the NT-2×10-3 group had greater drug-loading and drug-eluting abilities.4. The accumulative release amount followed the order: the mixture PLGA/ICA-NT group> coverage PLGA/ICA-NT group >NT-ICA group, so the PLGA had higher loading ability than that of TiO₂ nanotubes as drug carriers. The accumulative release amount of the mixture PLGA/ICA-NT group and the coverage PLGA/ICA-NT group were lower than that of NT-ICA group in the initial 4 hours,presumably showing better slow release characteristic in the burst phase. The release time of the mixture PLGA/ICA-NT group（10 days） and the coverage PLGA/ICA-NT group（12 days） was longer than NT-ICA group（9 days）. Hence, the PLGA showed better slow release characteristic compared with TiO₂ nanotubes especially in the burst phase.Conclusions:1. The pure Ti could be formed into uniformly controllable nanotubes by anodic oxidation. The roughness of NT group was higher than that of PT group. The contact angle of NT group was lower than that of PT group, which had higher hydrophilicity.2. The TiO₂ nanotubes could load more icariin than Ti. Compared with NT-10-3 group, more icariin on the icariin/TiO₂ nanotube group soaked in higher concentrated solutions （NT-2×10-3） was uniformly distributed and could incorporate into nanotubes.3. Compared with icariin-loaded Ti groups, the icariin-loaded nanotube groups had greater loading and slow release capacities, which could extend the release time.The icariin/TiO₂ nanotube group soaked in higher concentrated solution（NT-2×10-3）showed higher loading and extending the release time than the icariin/TiO₂ nanotube group soaked in 10-3mol/ml solution （NT-10-3）.4. The icariin/TiO₂ nanotube coating loaded with PLGA could improve the loading and release capacities. PLGA could extend the release time mainly in the burst phase. The mixture PLGA/ICA-NT group could enlarge the loading amount compared with the coverage PLGA/ICA-NT group. However, the coverage PLGA/ICA-NT group showed greater slow release capacity, which could extend the release time to 12 days.