| It has been gradually recognized and utilized that surface nanostructures of biomaterials have important effects on their biological properties. Controlled or modified nano-featured surfaces could modulate the interaction between tissues and materials. When biomaterial was implanted into human body, the first reaction was the selective adsorption of protein in blood and tissue fluid onto the surfaces of materials. Therefore, it is significant to study the adsorption and release behaviors of protein on the nanostructure surface of materials. In addition, nanotechnology has attracted wide attention and achieved great progress in the field of life science and medicine. The study on inorganic nano-material, especially the nano-porous materials, brings new opportunity to drug delivery.The porous anodic alumina (PAA) membranes are typical self-assembly nano-porous arrays materials with relatively long-range ordered nano-porous structure. Owing to the large-area and ordered nano-porous structure on its surface, it is also suitable for serving as carrier for controlled drug release.In this study, we took advantage of the structural features of the nano-porous anodic alumina and designed highly ordered nano-pore arrays with different pore sizes. Then the effects of these nano-porous structures on the adsorption and release behaviors of bovine serum albumin (BSA) and bovine fibrinogen (BF) were investigated in detail. The micromorphology and components of the PAA samples before and after adsorbing protein were characterized by field emission scanning electron microscopy (FESEM) and fourier transform infrared spectroscopy (FT-1R). respectively. The protein adsorption and release behaviors were measured by using the bicinchoninic acid (BCA) protein assay method. Langmuir fitting curve was used to simulate protein adsorption isotherm model. Fickian theorem was used to simulate protein release mechanism. Meanwhile, the loading and release behaviors of gentamicin on the surface of PAA were investigated as well. UV-vis was used to detect the loading and release behavior of gentamicin on PAA. Fickian theorem was used to simulate gentamicin release mechanism. Higuchi equation and Double Phase Reaction Kinetics Model were used to imitate the gentamicin adsorption model.The obtained results were described as follows:(1) The adsorption studies indicated that the adsorption quantities of BSA on PAA increased as time goes from0to6h and reached the maximum at5h with an initial BSA concentration of500μg/ml. Meanwhile, the adsorption quantities of BSA increased with the addition of the pore size of PAA (PAA25-PAA75) and reached the maximum on PAA75. The saturated adsorption quantities of PAA25, PAA50, PAA65and PAA75were15.53,23.02.28.48and30.31μg/ml respectively. In addition, the adsorption quantities of BSA on flat Al reached the maximum after4h with saturated adsorption quantities of14.3μg/cm2. In order to determine the best adsorption concentration, BSA with different initial concentration (including0.1,0.5,1.0.1.5and2.0mg/ml) was used. The results indicated that the initial concentration of BSA reached about1.5mg/ml. the adsorption capacity did not clearly enhance and the saturated adsorption quantities were38.8μg/cm2on surface of PAA75.(2) The adsorption studies of BF indicated that the adsorption behavior of BF was similar to the adsorption behavior of BSA. The adsorption quantities of flat Al. PAA25and PAA50reached saturation at5h. They were26.23,37.37and43.83μg/cm2. respectively. PAA65and PAA75reached saturated adsorption at4h and the adsorption quantities were49.72and50.97μg/cm2. In order to determine the best adsorption concentration, BF with different initial concentration (including0.1,0.5,1.0,1.5and2.0mg/ml) was used. The results indicated that the initial concentration of BF reached about1.0mg/ml. the adsorption quantities did not significantly increase and the saturation adsorption quantities were60.3μg/cm2(3) The release research of BSA and BF indicated that the protein release process was divided into two stages, burst release and slow release. More than89%and90%of BSA and BF were released from the surface of flat Al within6h in a burst release manner, respectively. While the release of BSA from PAA have a relatively slow and sustained manner. No more than55%of BSA was release from PAA sample within72h. and no significant difference of release rate was observed among PAA sample. In addition, significant differences have been observed between the releases of BF and BSA. With the pore sizes increase, the BF release rate gradually decreased. The release rates were79.8%,73.4%,66.4%and63.1%, respectively. The Fickian diffusion research shown that the protein release rate was regulated by specific surface area of PAA and concentration of protein. (4) The loading research of gentamicin on PAA indicated that the loading quantity of gentamicin into the nanopores of PAA was significantly enhanced as compared to the flat Al. With the increasing size of pore (PAA25-PAA75), the loading quantities increased and reached the maximum on PAA75. The maximum loading quantities was198.8μg/cm2on PAA75with an initial concentration of300μg/ml. The release profile of gentamicin shown that more than92.5%of gentamicin was rapidly released from the surface of flat Al within6h. while only about72.5%,75.8%,73.3%and77.9%of gentamicin was released from the PAA25-PAA75in a sustained and slow manner within96h. respectively. In addition, When PAA samples with gentamicin were daubed by gelatin, the release time of gentamicin was added to144h with the release amount of63.6%,64.0%,67.7%and68.4%from PAA25to PAA75, respectively. The Fickian diffusion research shown that the gentamicin release rate was related to the pore size of PAA and concentration of gentamicin. The release kinetics of gentamicin corresponded to the Double Phase Reactions Kinetics Model, which was consisting of two stages:fast release and slow release. |
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