Hongguo Xie

In Vitro and in Vivo characterization of alginate-chitosan-alginate artificial microcapsules for therapeutic oral delivery of live bacterial cells

Oral administration of artificial cell microcapsules entrapping live bacterial cells is a promising approach in disease therapy. However, the current technology of microcapsules limits this approach. In this study, alginate-chitosan-alginate (ACA) microcapsules entrapping live bacterial cells were prepared with the purpose of oral delivery for therapy, and their in vitro and in vivo properties were investigated. Genetically engineered Escherichia coli DH5 were used as the model bacterial strain. ACA microcapsules remained intact and stable in simulated gastrointestinal fluid and the entrapped bacteria cells survived and grew normally. Moreover, ACA microcapsules were more stable than alginate-polylysine-alginate microcapsules in the rat gastrointestinal tract, which was attributed to the enhanced resistance of the ACA microcapsules to enzymatic digestion. Therefore, these results reinforce the potential of ACA microcapsules for the therapeutic oral delivery of live bacterial cells.

Enhancement of Surface Graft Density of MPEG on Alginate/Chitosan Hydrogel Microcapsules for Protein Repellency

Alginate/chitosan/alginate (ACA) hydrogel microcapsules were modified with methoxy poly(ethylene glycol) (MPEG) to improve protein repellency and biocompatibility. Increased MPEG surface graft density (n(S)) on hydrogel microcapsules was achieved by controlling the grafting parameters including the buffer layer substrate, membrane thickness, and grafting method. X-ray photoelectron spectroscopy (XPS) model was employed to quantitatively analyze n(S) on this three-dimensional (3D) hydrogel network structure. Our results indicated that neutralizing with alginate, increasing membrane thickness, and in situ covalent grafting could increase n(S) effectively. ACAC(PEG) was more promising than ACC(PEG) in protein repellency because alginate supplied more -COO(-) negative binding sites and prevented MPEG from diffusing. The n(S) increased with membrane thickness, showing better protein repellency. Moreover, the in situ covalent grafting provided an effective way to enhance n(S), and 1.00 ± 0.03 chains/nm(2) was achieved, exhibiting almost complete immunity to protein adsorption. This antifouling hydrogel biomaterial is expected to be useful in transplantation in vivo.

Effect of surface wettability and charge on protein adsorption onto implantable alginate-chitosan-alginate microcapsule surfaces

Alginate-chitosan-alginate (ACA) microcapsules have been developed as a device for the transplantation of living cells. However, protein adsorption onto the surface of microcapsules immediately upon their implantation decides their ultimate biocompatibility. In this work, the chemical composition of the ACA membranes was determined using X-ray photoelectron spectroscopy (XPS). The surface wettability and charge were determined by contact angle and zeta potential measurements, respectively. Then, the effects of surface wettability and charge on bovine fibrinogen (Fgn) and gamma globulin (IgG) adsorption onto ACA microcapsules were evaluated. The results showed that ACA microcapsules had a hydrophilic membrane. So, the surface wettability of ACA microcapsules had little effect on protein adsorption. There was a negative zeta potential of ACA microcapsules which varies with the viscosity or G content of alginate used, indicating a varying degree of net negatively charged groups on the surface of ACA microcapsules. The amount of adsorbed protein increased with increasing of positive charge. Furthermore, the interaction between proteins and ACA microcapsules is dominated by electrostatic repulsion at pH 7.4 and that is of electrostatic attraction at pH 6.0. This work could help to explain the bioincompatibility of ACA microcapsules and will play an important role in the optimization of the microcapsule design.

Injectable in situ forming chitosan-based hydrogels for curcumin delivery

AbstractIn this paper, a series of injectable in situ forming chitosan-based hydrogels were prepared by chemical crosslinking of chitosan and genipin with the cooperation of ionic bonds between chitosan and sodium salts at room temperature. Four hydrogels (A, B, C, and D) were obtained by mixing chitosan, genipin and a sodium salt of trisodium phosphate (Na3PO4·12H2O), sodium sulfate (Na2SO4), sodium sulfite (Na2SO3), or sodium bicarbonate (NaHCO3) and examined for their characteristics, morphology, and rheological properties. Their cell viability assays exhibited low toxicity and the localized in situ gel formation was detected after subcutaneous injections in rat. Curcumin which possesses many pharmaceutical potentials but has low bioavailability, was chosen as a drug model. In vitro curcumin release profiles exhibit sustained release properties with initial burst release for all hydrogels with about 3 to 6 times higher cumulative release than other gel controls. The results of this study demonstrate that our hydrogels have a potential as local curcumin carriers.n

Effect of Lipolysis on Drug Release from Self-microemulsifying Drug Delivery Systems (SMEDDS) with Different Core/Shell Drug Location

The objective of this study is to investigate the effect of lipolysis on the release of poorly water-soluble drug from SMEDDS in the perspective of drug core/shell location. For this purpose, four SMEDDS formulations with various core/shell properties were developed based on long-chain lipid or medium-chain lipid as well as different surfactant/oil ratios. Poorly water-soluble drugs, hymecromone and resveratrol, were significantly solubilized in all SMEDDS formulations and the diluted microemulsions. Fluorescence spectra analysis indicated that hymecromone was mainly located in the shell of microemulsions, while resveratrol was located in the core. The effect of lipolysis on the release rates of drugs with different core/shell locations were investigated by a modified in vitro drug release model. For the drug located in the shell, hymecromone, the release profiles were not affected during the lipolysis process and no significant differences were observed among four formulations. For the drug located in the core, resveratrol, the release rates were increased to various degrees depending on the extent of digestion. In conclusion, the drug core/shell location plays an important role for determining the effect of lipolysis on drug release from SMEDDS formulation.

Permeability changes of the cell-contained microcapsules visualized by confocal laser scanning microscope.

Microencapsulation of recombinant cells is a novel means for gene therapy. However, one of the major concerns is the relationship between the permeability of microcapsule and cell growth. Many studies have focused on the permeability of empty microcapsule, but little is known about the effect of the cell growth on the permeability of a cell-contained microcapsule. A combination of fluorescence labeled protein and confocal laser scanning microscope (CLSM) provides the information about the permeability changes during the cell growth. A decrease of membrane permeability was detected on the 14th day. Meanwhile, membrane surface protein fouling was also investigated. A significant increase of membrane surface protein content was detected on the 21st day. In order to study the effect of the permeability changes on the cell viability, the membrane of cell-contained microcapsules with different permeability was set up by incubating gel beads in poly-L-lysine for 5 and 30 min, respectively, to mimic the bovine serum albumin cutoff, and a retard of cell growth was found in 7 days culture. These results showed that the protein fouling of the microcapsule membrane caused by the cell growth may be an important factor to influence cell viability.

ArticleMaterials ScienceIn situ forming chitosan-based hydrogel as a lung sealant for biological lung volume reduction

Biological lung volume reduction (BLVR) using lung sealant has received more attention recently as a new non-surgical approach to emphysema treatment. Many tissue sealants have been studied but only a few have been proposed for BLVR. In this work, we prepared in situ forming chitosan-based hydrogels (CSG) using covalent cross-linking of chitosan and genipin in the cooperation of ionic interaction between chitosan and sodium orthophosphate hydrate (Na3PO4·12H2O) and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and rheological methods. CSG showed short gelation time (8xa0min), high swelling ratio (>100xa0%) and non-toxicity (3T3 mouse fibroblast cell viability >80xa0%) under physiological conditions. The application of lung sealant for BLVR was tested in a Chinese dog and evaluated by chest computed tomography. After 3xa0weeks of the installation of CSG in bronchopulmonary segment, the gel formation was detected at a localized region of bronchi and the local atelectasis occurred. Our findings indicate that this chitosan-based hydrogel is a promising new candidate for use as a lung sealant for BLVR.