Stabilized micelles as delivery vehicles for paclitaxel

Paclitaxel is an antineoplastic drug used against a variety of tumors, but its low aqueous solubility and active removal caused by P-glycoprotein in the intestinal cells hinder its oral administration. In our study, new type of stabilized Pluronic micelles were developed and evaluated as carriers for paclitaxel delivery via oral or intravenous route. The pre-stabilized micelles were loaded with paclitaxel by simple solvent/evaporation technique achieving high encapsulation efficiency of approximately 70%. Gastrointestinal transit of the developed micelles was evaluated by oral administration of rhodamine-labeled micelles in rats. Our results showed prolonged gastrointestinal residence of the marker encapsulated into micelles, compared to a solution containing free marker. Further, the oral administration of micelles in mice showed high area under curve of micellar paclitaxel (similar to the area of i.v. Taxol(®)), longer mean residence time (9-times longer than i.v. Taxol(®)) and high distribution volume (2-fold higher than i.v. Taxol(®)) indicating an efficient oral absorption of paclitaxel delivered by micelles. Intravenous administration of micelles also showed a significant improvement of pharmacokinetic parameters of micellar paclitaxel vs. Taxol(®), in particular higher area under curve (1.2-fold), 5-times longer mean residence time and lower clearance, indicating longer systemic circulation of the micelles.

Immobilization of saccharomyces cerevisiae in novel hydrogels based on hybrid networks of poly(ethylene oxide), alginate and chitosan for ethanol production

Hydrogel matrices were designed as hybrid networks of poly(ethylene oxide) (PEO) with natural polymers,alginate or chitosan by UV irradiation. The networks were formulated in the single-stage procedure inwhich the alginate or chitosan were added to the crosslinking reaction solution of PEO, and two-stage procedure,with additional chemical crosslinking of alginate or chitosan. Double-layer hydrogels composed of PEOhydrogel core with entrapped cells and outer natural hydrogel layer were also synthesized. The hydrogels werecharacterized by gel fraction yield and degree of equilibrium swelling as well as by rheological measurements.The production of ethanol by immobilized Saccharomyces cerevisiae was used to test the suitability of the synthesizedhybrid hydrogels to serve as carriers for cell immobilization. The presence of cells affected the mechanicalproperties and the structure of the polymer networks. The best system for immobilization was found to bethe PEO/alginate/Ca, which exhibited high mechanical strength (G′, 830; GF, 93; ESH2O, 15) without affectingthe metabolic functions of the cells. The maximum ethanol yield was 0.42 g/g corresponding to 82 % of thetheoretical yield.

Thermoresponsive Polyoxazolines as Vectors for Transfection of Nucleic Acids

Poly(2-oxazoline)s (POx) are an attractive platform for the development of non-viral gene delivery systems. The combination of POx moieties, exhibiting excellent biocompatibility, with DNA-binding polyethyleneimine (PEI) moieties into a single copolymer chain is a promising approach to balance toxicity and transfection efficiency. The versatility of POx in terms of type of substituent, copolymer composition, degree of polymerization, degree of hydrolysis, and chain architecture, as well as the introduction of stimuli-responsive properties, provides opportunities to finely tune the copolymer characteristics and physicochemical properties of the polyplexes to increase the biological performance. An overview of the current state of research in the POx-PEI-based gene delivery systems focusing particularly on thermosensitive POx is presented in this paper.