Designing, structural determination and biological effects of rifaximin loaded chitosan- carboxymethyl chitosan nanogel.

Due to the poor solubility and permeability of rifaximin (RFX), it is not effective against intracellular pathogens although it shows strong activity against most bacteria. To develop an effective mucoadhesive drug delivery system with a targeted release in bacterial infection site, RFX-loaded chitosan (CS)/carboxymethyl-chitosan (CMCS) nanogel was designed and systematically evaluated. FTIR, DSC, and XRD demonstrated that the nanogel was formed by interactions between the positively charged NH3+ on CS and CMCS, and the negatively charged COO on CMCS. RFX was encapsulated into the optimized nanogel in amorphous form. The nanogel was a uniform spherical shape with a mean diameter of 171.07 nm. It had excellent sustained release, strong mucin binding ability, and pH-responsive properties of quicker swelling and release at acidic pH. It showed low hemolytic ratio and high antioxidant activity. The present investigation indicated that the CS-nanogel could be potentially used as a promising bacterial responsiveness drug delivery system.

Bioadhesive pellets of astragalosides: preparation and adhesive evaluation based on the physical properties of wet mass / 药学学报

Bioadhesive preparation can be attached to specific sites to control drug release rate, increase drug concentration and increase efficacy, which is based on natural or synthetic polymer material. In this paper, based on the physical properties of wet mass, a method for screening adhesion formulation was proposed, which was different from conventional way of screening optimal formulation, and astragalosides loaded bioadhesive pellets were prepared by extrusion-spheronization method (extrusion speed 30 r·min-1, spheronization speed 808 r·min-1, spheronization time 7.5 min) based on this formulation screening method, small living animal imaging technology and mucin from porcine stomach model were used to evaluate the in vivo and invitro adhesiveness behaviour of the pellets. According to the relationship between the physical properties of wet mass and the formability and adhesiveness of bioadhesive pellets, five key physical properties hardness (Ha), adhesiveness (Ad), springiness (Sp), cohesiveness (Co), chewiness (Ch) were selected as the index of screening optimal formulation, therefore a comprehensive evaluation model was established, which based on principal component analysis, to did digital ranking for these proposed adhesion formulation, the optimal formulation was determined: microcrystalline cellulose: (chitosan∶Carbomer 940 = 2∶1), the adhesive material dosage accounted for 20% of the excipient dosage, and the ratio of drugs to excipients was 1 : 4. All animal experiments have been approved by Ethics Committee of Shanghai University of Traditional Chinese Medicine. The in vivo and in vitro adhesive evaluation results showed the pellets had a clear advantage in intestinal adhesion over normal pellets, its also proved the scientificity and reliability of the method of screening bioadhesive formulation.

Pectin-coated chitosan-LDH bionanocomposite beads as potential systems for colon-targeted drug delivery.

This work introduces results on a new drug delivery system (DDS) based on the use of chitosan/layered double hydroxide (LDH) biohybrid beads coated with pectin for controlled release in the treatment of colon diseases. Thus, the 5-aminosalicylic acid (5ASA), the most used non-steroid-anti-inflammatory drug (NSAID) in the treatment of ulcerative colitis and Crohn's disease, was chosen as model drug aiming to a controlled and selective delivery in the colon. The pure 5ASA drug and the hybrid material prepared by intercalation in a layered double hydroxide of Mg2Al using the co-precipitation method, were incorporated in a chitosan matrix in order to profit from its mucoadhesiveness. These compounds processed as beads were further treated with the polysaccharide pectin to create a protective coating that ensures the stability of both chitosan and layered double hydroxide at the acid pH of the gastric fluid. The resulting composite beads presenting the pectin coating are stable to water swelling and procure a controlled release of the drug along their passage through the simulated gastrointestinal tract in in vitro experiments, due to their resistance to pH changes. Based on these results, the pectin@chitosan/LDH-5ASA bionanocomposite beads could be proposed as promising candidates for the colon-targeted delivery of 5ASA, with the aim of acting only in the focus of the disease and minimizing side effects.