A type of esophageal stent coating was investigated, which consists of one 5-fluorouracil (5-FU)-containing ethylene-vinyl acetate (EVA) copolymer layer and one drug-free EVA protective layer. The amount of 5-FU permeated through the protective layer (100 μm) is thousands of times lower than that of 5-FU released from the drug-loaded layer, indicating that the coating releases drug molecules in a unidirectional fashion. The barrier of the protective layer can be attributed to a tiny flux of 5-FU through the EVA film. In vitro release profiles of the stent coatings with various drug contents were investigated in pH 6.5 phosphate buffer solution. The results show that, the burst effect is not obvious for the coatings with 20-50% of 5-FU and the release profiles can be characterized by a first faster release rate phase followed by a decrease in release rate. The release data in the early and late stages can all be well fitted with zero-order kinetics, and the possible reasons for the release profiles were discussed. The rate of 5-FU permeation through porcine esophageal mucosa from the coatings can be adjusted by changing drug content of the coatings. The increase of drug content of the coatings significantly leads to the decrease of the maximum elongation, maximum tensible strength and maximum tear strength, and the increase of the modulus of elasticity. The coatings with 20-60% of drug attached to a stent can endure repeated binding and liberation via a stent introducer.

The drug percolation thresholds of 5-fluorouracil-loaded ethylene-vinyl acetate stent coatings were estimated to characterize their drug release behavior and mechanical properties. The stent coatings were prepared using 5-fluorouracil (5-FU) as antitumor drug and ethylene-vinyl acetate (EVA) as matrix forming material in different ratios. In vitro release assays were carried out exposing only one side of coating to pH 6.5 PBS. Based on the release profiles, the drug percolation thresholds were estimated as 0.21 of total porosity (corresponding to ca. 32%, w/w of the drug), which is in approximately agreement with the atomic force microscopy (AFM) result. Based on the coating tensible break strength and tear break strength data, the mechanical percolation thresholds of drug were obtained as 39.7±0.3 and 37.5±1.4% (w/w) of drug content, respectively.

Star-shaped block copolymers consisting of non-toxic poly(ethylene glycol) and biodegradable polycaprolactone ((PEG5K-PCL)4) were synthesized by ring-opening polymerization of the e-caprolactone monomer with hydroxyl-terminated 4-armed PEG as initiator. These biodegradable, amphiphilic star block copolymers showed micellization and sol-gel transition behaviors in aqueous solution with varying concentration and temperature. In the dilute aqueous solutions of star block copolymers, micellization behavior occurred over specific concentration. The 1,6-diphenyl-1,3,5-hexatriene (DPH) solubilization method was used to determine the critical micellization concentration (CMC) of star block copolymers. The obtained micelle size increased with increasing hydrophobic PCL block length. In high-concentration solutions, the star block copolymers showed temperature-sensitive sol-gel transition behavior. The morphology of the micelle and gel was investigated by atomic force microscopy (AFM). As a result, the micelles showed a core-corona spherical structure at concentration near CMC, while the gel showed a mountain-chain-like morphology picture. It was proposed that with increasing the micelle concentration the worm-like micelle clusters formed firstly and the gel was constructed by the packing of micelle clusters.

Chitosan-g-PCL-b-MPEG copolymers of various compositions were successful synthesized via a protectiongraft-deprotection procedure, by the esterification of phthaloyl-protected chitosan (PHCS) with MPEG-b-PCL-COOH, which was synthesized from MPEG and e-caprolactone and carboxylated by maleic anhydride. The chemical structure of the chitosan-g-PCL-b-MPEG was characterized by Fourier transform infrared and NMR spectroscopy. The chitosan-g-PCL-b-MPEG was obtained as amphoteric hybrid with amino polysaccharide backbone and amphiphilic MPEG-b-PCL side chain. Their crystallinity and aggregation behavior in aqueous solution were also investigated.

We present herein a novel method of pIII-based antibody phage display using Hpd3cells—bacterial cells bearing the genome of a gene-III-lacking helper phage (VCSM13d3). A high level of single-chain variable fragments (scFvs) was displayed in the consequent phagemid particles using Hpd3cells to rescue the phagemid encoding scFv-pIII. Hpd3cells considerably improved the specific enrichment factor when used for constructing an immunized antibody library. In addition, using Hpd3cells could overcome pIII resistance and can contribute to the efficient enrichment of specific binding antibodies from a phage display library, thereby increasing the chance of obtaining more diverse antibodies specific for target antigens.