Shu Huei Yu

Nanoparticle-induced tight-junction opening for the transport of an anti-angiogenic sulfated polysaccharide across Caco-2 cell monolayers

Fucoidan has the ability to inhibit angiogenesis by human umbilical vein endothelial cells (HUVECs). However, a major clinical limitation is its poor oral availability because fucoidan is a hydrophilic macromolecule. In this study, an oversulfation reaction of fucoidan has been performed to enhance its anti-angiogenic activities. The synthesized, oversulfated fucoidan (OFD) was characterized by Fourier transform infrared spectroscopy. The oversulfate content of OFD was estimated to be 41.7% by using a BaCl2 gelatin method. Nanoparticles (NPs) composed of chitosan (CS) and OFD were prepared by a polycation-polyanion complex method. The mean particle sizes of prepared CS/OFD NPs were in the range of 172-265nm with a negative or positive surface charge, depending on the relative concentrations of CS to OFD used. The self-assembled NPs with pH-sensitive characteristics could be used as a pH-switched nanocarrier for oral delivery of the antiangiogenic macromolecule, OFD, in response to simulated gastrointestinal (GI) tract media. Evaluation of test NPs in enhancing the intestinal paracellular transport of OFD suggested that the NPs with a positive surface charge could transiently open the tight junctions between Caco-2 cells and thus increase the paracellular permeability. Tight-junction opening and restoration were examined by monitoring the redistribution of ZO-1 tight-junction proteins using confocal laser scanning microscopy (CLSM). The transported OFD significantly inhibits the tube formation of HUVECs via competitive binding of OFD and basic fibroblast growth factor (bFGF) to bFGF receptors (bFGFRs).

Thiol-Modified Chitosan Sulfate Nanoparticles for Protection and Release of Basic Fibroblast Growth Factor

A series of chitosan (CS) derivatives, the 6-O-carboxymethylchitosan (6-O-CC), 2-N sulfated 6-O-carboxymethylchitosan (N-SOCC) and the 2-N and 3,6-O sulfated 6-O-carboxymethyl chitosan (N,O-SOCC) were synthesized in this study. The chemical structures and the degrees of substituted carboxymethyl and sulfate groups of the synthesized compounds were respectively determined by FT-IR spectra and elemental analysis. N,O-SOCC displayed the highest protective efficiency for basic fibroblast growth factor (bFGF) as examined by the L929 fibroblast culture test and docking simulation. N,O-SOCC-4-thio-butylamidine (TBA) conjugates prepared by modification of N,O-SOCC with 2-iminothiolane were in situ cross-linkable. The degrees of thiol substitution of the 2-iminothiolane modified N,O-SOCC polymers were determined to be in the ranges of 45.9 +/- 3.7 and 415.6 +/- 12.5 micromol SH/g SOCC by quantifying the amount of thiol groups on the thiolated polymers with Ellmans reagent. The 2-iminothiolane modified N,O-SOCC and CS complex could be used for preparing nanoparticles by a polyelectrolyte self-assembly method, and the release of bFGF from the nanoparticles was successfully controlled. L929 fibroblast culture tests showed that the thiol modified N,O-SOCC/CS nanoparticles could effectively protect bFGF from inactivation over a 120 h period. The results of this study suggest that the thiol modified N,O-SOCC/CS nanoparticles may be useful as novel materials for specific delivery of bFGF with mitogenic activity.

Self-organized nanoparticles prepared by guanidine- and disulfide-modified chitosan as a gene delivery carrier

The use of membrane-permeable and intracellular reducible molecules for drug or gene delivery has gained increasing attention. In this work, chitosan (CS) was modified with extending arms consisting of disulfide spacers and arginine (Arg) residues (CS–SS–Arg) as a novel non-viral carrier for gene delivery. The chemical structure of synthesized CS–SS–Arg was characterized by proton nuclear magnetic resonance (1H-NMR) spectroscopy. Cleavage of disulfide spacers by glutathione (GSH) and dithiothreitol due to thiol-disulfide exchange reactions indicates that CS–SS–Arg is likely reducible in cytoplasm. The CS–SS–Arg was allowed to condense green fluorescent protein (GFP) DNA to form self-organized nanoparticles with a diameter of 130 nm and zeta potential of 35 mV. The DNA was released from CS–SS–Arg/DNA nanoparticles over time in the presence of GSH. Transfection studies by confocal laser scanning microscopy demonstrate that CS–SS–Arg/DNA nanoparticles had a 48-h delay of GFP expression in human embryonic kidney 293 (HEK 293) cells; however, the GFP expression level was higher and more sustainable than that of its unmodified CS counterpart. These analytical results suggest that the Arg-rich bioreducible CS–SS–Arg/DNA nanoparticles are promising as a carrier for gene delivery.

Preparation of fucoidan-shelled and genipin-crosslinked chitosan beads for antibacterial application.

In this study, a fucoidan-shelled chitosan bead was developed with the purpose of oral delivery of berberine to inhibit the growth of bacteria. The cross-linking level and swelling property of the beads were affected by the pH value and the composition of the genipin/fucoidan combined gelling agent. The drug release of the berberine-loaded beads was faster in simulated gastric fluid (pH 1.2) than those in simulated intestinal fluid (pH 7.4). Furthermore, a nanoparticles/beads complex system was developed by incorporation of berberine-loaded chitosan/fucoidan nanoparticles in the fucoidan-shelled chitosan beads. The nanoparticles/beads complex served as a drug carrier to delay the berberine release in simulated gastric fluid, with an estimated lag time of 2 h. Our results showed that the berberine-loaded beads and nanoparticles/beads complex could effectively inhibit the growth inhibition of common clinical pathogens, such as Staphylococcus aureus and Escherichia coli, and have the advantage of continually releasing berberine to inhibit the growth of the bacteria over 24 h.

Free DOX and chitosan-N-arginine conjugate stabilized indocyanine green nanoparticles for combined chemophotothermal therapy.

Indocyanine green (ICG) is a FDA-approved near-infrared (NIR) cyanine dye used in medical diagnostics. However, the utility of ICG remains limited by its unstable optical property, and concentration-dependent aggregation and precipitation. A chitosan-arginine conjugate (CS-N-Arg) was developed to increase the stability of ICG in physiological buffer saline via formation of strong electrostatic interactions between ICG and CS-N-Arg. The CS-N-Arg/ICG complex prevented ICG from aggregation and precipitation, thus it could serve as a theranostic nanomaterial for image-guided photothermal cancer therapy. The CS-N-Arg/ICG NPs showed excellent photostability, clear fluorescent images, and rapid temperature rise under laser irradiation. Cell viability assay indicated that CS-N-Arg/ICG NPs could efficiently suppress the growth of doxorubicin (DOX) resistant breast cancer cell (MCF-7/ADR cells) under NIR photothermal treatments. In combination of DOX with CS-N-Arg/ICG NPs, a combined effect was observed in MCF-7/ADR breast cancer cells due to dual hyperthermia and chemical therapeutic effects. The present observations suggest that CS-N-Arg/ICG NPs can effectively deliver ICG molecules to MCF-7/ADR breast cancer cells and overcome DOX resistance in the cells by hyperthermia.

Tripolyphosphate Cross-Linked Macromolecular Composites for the Growth of Shape- and Size-Controlled Apatites

Bioactive composites that enable the formation of calcium phosphates have received increased attention over the last decade, in the development of osteoconductive biomaterials for orthopaedic applications. In this work, tripolyphosphate (TPP)-cross-linked chitosan/gelatin composites (TPP-CG) were prepared for the growth of shape- and size-controlled calcium phosphates on/in the composites. The mineralization pattern of the composites, after soaking in the Ca(OH)2 aqueous solution, clearly demonstrated oriented, needle-like nanocrystallites of calcium phosphates in the matrix with especially high Ca/P molar ratio (3.98) as detected by energy dispersive X-ray spectroscopy (EDX) analysis. Subsequent to mineralization in a simulated body fluid (SBF), the mineralized composites showed micro-scaled spherical aggregates deposited on the surface and granule-like nanocrystallites grew in the matrix. The Ca/P molar ratio (1.72) and X-ray diffraction pattern of the nanocrystallites grown in the composites were similar to those of hydroxyapatite (HAp). Osteoblastic differentiation of ROS cells cultured on the mineralized composites allowed an enhanced expression of the chosen osteogenic marker (alkaline phosphatase, ALPase). These results indicated that the composites mineralized with micro- and nano-scaled calcium phosphates with various structural features make them attractive for bone tissue engineering applications.

Hydrogel microspheres for stabilization of an antioxidant enzyme: Effect of emulsion cross-linking of a dual polysaccharide system on the protection of enzyme activity

Catalase is an antioxidant enzyme abundant in natural resources. However, the enzyme is usually inactivated by gastric acid and digestive enzymes after oral ingestion. In this study, carboxymethyl chitosan (CM-chitosan) and hyaluronic acid (HA) conjugate hydrogel microspheres have been prepared by an emulsion cross-linking technique to retain the activity of catalase in simulated gastrointestinal (GI) fluids. Cross-linking reduced the swelling capability and increased the resistance toward hyaluronidase digestion of prepared HA-CM-chitosan hydrogel microspheres. Catalase entrapped in the hydrogel microspheres exhibited superior stability over a wide pH range (pH 2.0 and 6.0-8.0) as compared to the native enzyme. The entrapped catalase was also protected against degradation by digestive enzymes. Following the treatments, the catalase-loaded microspheres, in contrast to native catalase, could effectively decrease the intracellular H2O2 level and protect HT-29 colonic epithelial cells against H2O2-induced oxidative damage to preserve cell viability. These results suggested that the HA-CM-chitosan hydrogel microspheres can be used for entrapment, protection and intestinal delivery of catalase for H2O2 scavenging.