Antibacterial Activity Of Berberine Loaded Supramolecular Networks Constructed From Carboxymethyl ?-cyclodextrin Modified Montmorillonite

Supramolecularorganoclays networks were for the first time successfully synthesized through a cheap,environmental friendly and scalable approach.The antibacterial properties of the networks loaded with berberine were investigated toward E.coli and S.aureus by using colonies growth on agar plates,fluorescent microscopy images and bacterial growth curves based on optical densities.This study mainly includes the following two parts:1.Preparation,characterization and in vitro release of berberine-loaded supramolecular networks.Thesynthesis ofsupramolecularorganoclay networkswithout the need of additional excipients and under very mild conditions from silanegrafted montmorillonite and aqueouscarboxymethyl ?-cyclodextrin andcarbodiimide hydrochloride solutionsin the presenceof N-hydroxysuccinimide at room temperature.Thenetworkswas characterized by FTIR,TGA,XRDand FESEM.Berberine hydrochloride was chosen as the model drugfor examining its release from thesupramolecularorganoclay networks.Results: The successful grafting of carboxymethyl ?-cyclodextrin on thesilanegrafted montmorillonite was verified by FTIR studies.The FTIR spectrum of supramolecularnetworks not only exhibited all characteristic peaks of silanegrafted montmorillonite,but also showed typical cyclodextrin absorption features of the ring vibrations at 587,613 and 745 cm–1.The XRD patternof supramolecularnetworksshoweda shift of the d001 peak to lower values with expansion of basal spacing,indicatedthat carboxymethyl ?-cyclodextrin not only graftedon the surface of montmorillonite,but also efficiently intercalatedintothe laminates of MMT.Thermogravimetric analysis showed thatthe amount of carboxymethyl ?-cyclodextringrafted onto thesilanegrafted montmorillonite could be estimated to be 6.9 wt%.The uniquestructure of supramolecularnetworks was observedby field emission scanning electron microscopy.The supramolecular networks exhibitedloading capacity of27.8% BBHat 50°C for 5h with the pH increased from 2.0 to 7.0.BBH release behaviour from the CMCD–APTES–MMT supramolecular network was examined over a 120 h period with the initial BBH concentration of27.8?g/mLfor networks under simulated physiological conditions(PBS,pH 7.4,37 °C).BBH was released according to a two-step process with about 49.3% of the drug released in the first ~12 h,after which there wasa steady and controlled increase in release for up to 5 days.2.Antibacterial activity of berberine hydrochloride loaded supramolecular networks.The antibacterial activity of the drug loaded supramolecular networks and free drug were compared by the dilution plate method.Fluorescence microscopy was used to observe the uptake of berberine hydrochloride by bacteria,and investigateddose-dependent antibacterial activity ofdrug loaded supramolecular networks.UV spectrophotometry was used to determine the optical density of bacterial suspension at 600 nm,and to investigate the long term antibacterial activity of drug loaded supramolecular networks.Theinteraction between drug loaded supramolecular materials and bacteria was observed by field emission scanning electron microscopy.Results: Time-dependent antibacterial activity was observed and 600 ?g/mL of berberine hydrochloride loaded in the D-network maintained 98.45% inhibition towards E.coli and 250 ?g/mL of loading showed growth inhibition of 97.81% for S.aureus throughout 3 days,but the same dosage of the network containing no berberinehydrochloride hardly affected the growth of both bacterial strains.Our results suggest that supramolecularorganoclays networks,in the future,may function as promising antibacterial drug carrier systems to promote berberine delivery in E.coli and S.aureus.