Guiying Li

Adsorptive decolorization of methylene blue by crosslinked porous starch.

Crosslinked porous starch (CPS) was prepared by two steps. Native starch was crosslinked with epichlorohydrin and then CPS was prepared by hydrolyzing the crosslinked starch with α-amylase. As a biodegradable and safe adsorbent, CPS was used to remove methylene blue (MB) from the aqueous solution based on its characterizations, including surface area, pore volume and scanning electron microscopy (SEM). The results indicate that the adsorption capacity of CPS is much higher than native starch and relatively higher than porous starch. The effects of the initial concentration of MB, the time and temperature on the adsorption capacity were investigated. The pseudo-first-order kinetic model provides a better correlation of the experimental data in comparison with the pseudo-second-order model. The equilibrium adsorption data are well described by the Langmuir isotherm model with a maximum adsorption capacity of 9.46mg g(-1). The adsorption of MB on CPS is endothermic and spontaneous in nature. The thermodynamics data are in good agreement with physical adsorption mechanism.

Thermo- and pH-sensitive ionic-crosslinked hollow spheres from chitosan-based graft copolymer for 5-fluorouracil release

Thermo- and pH-sensitive ionic-crosslinked hollow spheres from self-assembly of chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAM) for controlled release of 5-fluorouracil were studied. CS-g-PNIPAM aggregated into core-shell micelles with collapsed PNIPAM as the core and CS as the shell at the temperature above LCST. Ionic crosslinking reagent sodium tripolyphosphate (TPP) was used to crosslink the shell to form hollow spheres after cooling to room temperature. The size of hollow spheres was manipulated by changing pH or temperature of the environment. The CS-g-PNIPAM hollow spheres with plenty of inner cavities showed high loading capacity for 5-fluorouracil due to the polymer-drug interactions. Release of 5-fluorouracil from nanoparticles was accelerated at the temperature above LCST ascribed to the destruction of polymer-drug interactions and the decrease of particles size. Changing pH or ionic strength deformed the structure hollow spheres, which led to the increase of drug release. These hollow nanoparticles with environmentally sensitive properties are expected to be utilized in the field of intelligent drug delivery.

pH-sensitive polyelectrolyte complex micelles assembled from CS-g-PNIPAM and ALG-g-P(NIPAM-co-NVP) for drug delivery.

In this paper, pH-sensitive polyelectrolyte complex micelles assembled from two oppositely charged graft copolymers chitosan-g-poly(N-isopropylacrylamide) (CS-g-PNIPAM) and sodium alginate-g-poly(N-isopropylacrylamide-co-N-vinyl-pyrrolidone) [ALG-g-P(NIPAM-co-NVP)] were prepared for controlled release of 5-fluorouracil (5-FU). The polyelectrolyte complex micelles showed a narrow size distribution with core-shell structure, where the core formed from positively charged CS and negatively charged ALG by electrostatic interactions. The hydrogen bonding interactions between micelles and 5-FU improved the drug loading. Changing temperature or pH, a controlled drug release was observed. Glutaraldehyde, as a chemical cross-linking agent, was used to improve the micelles stability and decrease the initial burst release. Cytotoxicity assays showed that drug-loaded micelles retained high cell inhibition efficiency in Hela cells. These novel complex micelles with environmentally sensitive properties are expected to be useful in the field of intelligent drug delivery system.

Polymeric hollow spheres assembled from ALG-g-PNIPAM and β-cyclodextrin for controlled drug release

In this paper, thermo-sensitive polymeric hollow spheres assembled from sodium alginate-graft-poly(N-isopropylacrylamide) (ALG-g-PNIPAM) and β-cyclodextrin (β-CD) were prepared for controlled release of 5-fluorouracil (5-FU). In aqueous solutions, β-CD and PNIPAM formed rod-like segments through inclusion complexation interactions and sodium alginate acted as coil segments, which resulted in the formation of hollow structures. The size and wall thickness of assemblies increased with the increase of β-CD in mixtures. The lower critical solution temperature (LCST) of hollow spheres varied in the range of 35-37°C. The hollow spheres exhibited high drug loading efficiency for 5-FU due to the hydrophilic cavities. The initial composition of mixtures, temperature and pH had a significant effect on the inclusion ability and drug release. Increasing temperatures above the LCST or decreasing pH to acidic conditions, a more rapid release rate was observed.

Synthesis of thermo-sensitive polyelectrolyte complex nanoparticles from CS-g-PNIPAM and SA-g-PNIPAM for controlled drug release

In this paper, thermo-sensitive polyelectrolyte complex nanoparticles assembled from chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAM) and sodium alginate-graft-poly(N-isopropylacrylamide) (SA-g-PNIPAM) were prepared for entrapment and release of 5-fluorouracil (5-FU). The morphology and size of the nanoparticles were observed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The polyelectrolyte complex nanoparticles showed a narrow size distribution. The hydrogen bonding interactions between nanoparticles and 5-FU, which was determined by fourier-transformed infrared spectroscopy (FTIR), increased drug loading. Glutaraldehyde, as a cross-linking agent, reinforced the nanoparticle structure and decreased the burst drug release. When changing temperature, pH, or ionic strength, a sustained and controlled drug release was observed. The novel complex nanoparticles with environmentally sensitive properties are expected to be useful in the field of intelligent drug delivery system.

Formation of thermo-sensitive polyelectrolyte complex micelles from two biocompatible graft copolymers for drug delivery

Thermo-sensitive polyelectrolyte complex (PEC) micelles assembled from two biocompatible graft copolymers chitosan-g-poly(N-isopropylacrylamide) (CS-g-PNIPAM) and carboxymethyl cellulose-g-poly(N-isopropylacrylamide) (CMC-g-PNIPAM) were prepared for delivery of 5-fluorouracil (5-FU). The PEC micelles showed a narrow size distribution with core-shell structure, in which the core formed from positively charged CS and negatively charged CMC by electrostatic interactions and the shell formed from thermo-sensitive PNIPAM. The synthesized PEC micelles have lower critical solution temperatures (LCST) in the region of 37°C, which is favorable for smart drug delivery applications. The hydrogen bondings between PEC micelles and 5-FU increased the drug loading. Changing temperature, pH or ionic strength, a sustained and controlled release was observed due to the deformation of PEC micelles. Adding glutaraldehyde, a chemical crosslinking reagent, was an efficient way to reinforce the micelles structure and decrease the initial burst release. Cytotoxicity assays showed that drug-loaded PEC micelles retained higher cell inhibition efficiency in HeLa cells.

Thermo-sensitive complex micelles from sodium alginate-graft-poly(N-isopropylacrylamide) for drug release.

Polymer micelles with environmentally sensitive properties have potential applications in biomedicine. In this paper, thermo-sensitive complex micelles assembled from biocompatible graft copolymers sodium alginate-graft-poly(N-isopropylacrylamide) (SA-g-PNIPAM) and divalent metal ions were prepared for controlled drug release. The polymer micelles had core-corona structure, which was constituted by metal ions (Ba(2+), Zn(2+), Co(2+)) cross-linked sodium alginate as the core and thermo-sensitive PNIPAM chains as the corona. Formation of polymer micelles was determined by Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The polymer micelles were observed as regular spheres with good polydispersity and excellent performance on drug encapsulation and release ability. The cumulative release of 5-fluorouracil (5-FU) from micelles was controlled by pH, ionic strength or temperature of surroundings. The superior properties of sensitive polymer micelles induced by metal ions are expected to be utilized in controlled drug delivery systems.

Stimuli-sensitive hollow spheres from chitosan-graft-β-cyclodextrin for controlled drug release.

In this paper, sensitive polymeric hollow spheres self-assembled from chitosan-grafted-β-cyclodextrin (CS-g-CD) and sodium tripolyphosphate (TPP) were prepared for controlled release of doxorubicin (DOX). The assemblies were formed by electrostatic interactions between positively charged amino group in CS-g-CD and negatively charged phosphate in TPP. The hollow spheres with diameters about 100nm were confirmed by transmission electron microscopy (TEM) and laser particle analyzer. The microspheres with hollow cavity were beneficial to improve the drug loading capacity for DOX with entrapment efficiency above 60%. The cumulative release of DOX from CS-g-CD/TPP hollow microspheres increased with the decrease of pH and the increase of temperature or ionic strength. At 37u2009°C and pH 5.2, the maximum drug release was above 90% with a continuous release rate. In-vitro cytotoxicity tests indicate that drug loaded hollow spheres exhibited evidently inhibition against cancer cells. These sensitive polymeric hollow spheres are expected to be used in biomedical field as potential carrier.

Sensitive complex micelles based on host-guest recognition from chitosan-graft-β-cyclodextrin for drug release

In this paper, pH-sensitive complex micelles were developed based on the host-guest recognition from chitosan-graft-β-cyclodextrin (CS-g-CD) and benzimidazole-terminated poly(ε-caprolactone) (BM-PCL) for controlled drug release. The formation and characterization of complex micelles were confirmed by fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and laser particle analyzer. The size of complex micelles was about 200nm with the core formed by BM-PCL/β-CD and the shell composed of chitosan. Doxorubicin (DOX), a model anticancer drug, was effectively loaded into the complex micelles via hydrophobic interactions. The encapsulation efficiency of DOX was up to 75%. The release of DOX from complex micelles was suppressed at neutral pH solutions due to the stability of micelles but accelerated at acidic solutions and high temperatures. These sensitive complex micelles might possess potential applications as intelligent nanocarriers for anticancer drug delivery.

Supramolecular assembly of poly(β-cyclodextrin) block copolymer and benzimidazole-poly(ε-caprolactone) based on host-guest recognition for drug delivery

A well-defined double hydrophilic poly(β-cyclodextrin)-containing diblock copolymer PEG-b-PCD was synthesized by atom transfer radical polymerization (ATRP). Complex micelles with defined core-shell structure were formed based on the host-guest interactions between poly(β-cyclodextrin) block copolymer and benzimidazole modified poly(ε-caprolactone) (BM-PCL). The hydrophobic PCD/BM-PCL resided in the core of micelles, while the hydrophilic poly(ethylene glycol) (PEG) chains acted as the micelles shell. The micelles exhibited regular spheres with diameter of about 255nm. The drug loading efficiency of micelles for doxorubicin (DOX) was high due to the hydrophobic core containing poly(β-CD) and PCL. The in vitro release demonstrated that DOX-loaded polymer micelles exhibited an enhanced sustained manner after an initial burst release. The release of drugs was accelerated as the pH reduced from 7.0 to 2.0 and the temperature increased from 25 to 37°C. These results indicate that the complex micelles have potential applications in controlled drug delivery.