| Drug delivery systems had numerous advantages compared with conventional dosage forms, such as improve therapeutic effect, reduce toxicity and improve patient compliance, by delivering drugs at a controlled rate over a period of time to the site of action. In the field of drug delivery nanofibers have gained incresing attentions because they presents several advantages:relatively easy drug entrapment during the process of electrospinning, obtaining of high loadings if so desired, stability and preservation of drug/growth factor activity, high surface area (which enhances drug release) and specific morphology which can be easily controlled. However the study about prodrug delivery system which was prepared from activity group of drug grafted onto the nonafibers and by which the drug release is controlled through both a chemical bond breaking and specific morphology of the structure is hardly found out. The supramolecular structure of bacterial cellulose produced by acetobacter xylinum is known to be different from plant cellulose even though the chemical structure is similar. BC has been attracting attention as a raw material for preparation of advanced materials, due to its advantageous properties that is imparted by the fine network structure. BC is a promising and fine biocompatible material suitable for medical device.These advantageous rendered BC an attractive material for use in devising intelligent drug-delivery systems with efficient in vivo performance.This study explored the potential of a novel conjugate from BC and Ibuprofen for application in drug-delivery systems by the ester bond breaking. The results of FT-IR analysis revealed that Ibuprofen had been successfully grafted onto the cellulose fibers and showed a direct symbol of the ester band via the esterification reaction. Morphological analysis revealed that the characteristic nano-and micro-fibril network of BC was maintained and totally in BC-IBU conjugates. DSC analysis and TG suggested that the thermal stability of the conjugate was suitable for the applications of drug-delivery system. The results of the drug-release in vitro studies suggest that the conjugates were pH-responsive behavior, which resulted in a lower in vitro drug-release rate in neutral solution compared to acidic and alkaline solution. The preliminary findings revealed that BC-IBU had a potential exploitable value as components in a controlled delivery system.Hybrid hydrogels of bacterial cellulose nanofiber and sodium alginate (BC/SA) was synthesized for application in drug delivery systems. The stimulus-responsive swelling properties and its stimulus-responsive drug release behaviors of the BC/SA hydrogels, using Ibuprofen as a model drug, were investigated in vitro. With addition of BC nanofiber, BC/SA hybrid hydrogels presented a more stable and precise the microstructure. Compared with pure SA hydrogels, the swelling properties of BC/SA hybrid hydrogels not only maintained pH-responsive property but also effectively enhanced electro-responsive property. The swelling ratio was less than8times compared with its dry weight at acidic conditions (pH=1.5) and it increased to more than13times when the pH value increased to11.8, which might be related to the ionization of SA in higher pH conditions. The hybrid hydrogels also showed an increasing swelling ratio from8times to14times its dry weight under an increasing applied voltage (0-0.5V). Effected by pH-responsive swelling behaviours, the drug release rate of BC/SA hybrid hydrogels in vitro was quite depended on pH value, i.e. fast in neutral or alkaline media but slow in acidic media. The drug release could also be enhanced in the presence of electric stimulus when compared with passive release. The releasing rate was dependent on the applied electric strength. Furthermore, the drug release profiles was interpreted based on Peppas’ semi-empirical equation that showed under pH and applied electric field the mechanism of drug release was characteristic for an anomalous transport, which can be regarded as a superposition of both Fickian diffusion and case-Ⅱ transport (swelling and erosion controlled drug release).A novel hybrid hydrogels based on BC/SA incorporated with MWCNTs was successfully prepared as a controlled drug release system. Swelling studies showed that the BC/SA/MWCNTs hybrid hydrogels had pH-responsive and electro-responsive swelling behavior, in which drug release was based on the response of the system to environmental changes. In vitro, hybrid hydrogels system exhibited a pH-sensitive drug release behaviors with varying pH. This was because the drug release was mainly affected by the pH-induced protonation and deprotonation of SA. Meanwhile, the drug release could be enhanced in the presence of electric stimulus when compared with the passive release, and it was found to be dependent on the applied electric strength. The combination stimuli-release studies demonstrated that the electric-enhanced releasing behaviours had selectivity for the pH value of the condition, i.e. fast in neutral media but slow in acidic and alkaline media. Pulsatile patterns of drug release were observed as electric stimulus was switched on and off. The pulsatile drug release studies indicated that embedded MWNTs as a conductive additive could effectively increased the electro-sensitivity of BC/SA/MWCNTs hybrid hydrogels. Furthermore, the pulsatile drug release studies also demonstrated that the pulsatile release behaviors were affected by the pH value. Only in neutral condition, drug release from BC/SA/MWCNTs hybrid hydrogels showed a significant pulsatile characteristic. Such systems therefore had the potential to contribute as a novel platform for pH-responsed gastrointestinal drug delivery or triggered by electric signal to get on-demand drug release. |
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