Potential c-myc antisense oligonucleotide carriers: PCl/PEG/PEI and PLL/PEG/PEI.

In this work, positively charged, micelle-forming polymers were synthesized and used as a model vector to deliver antisense oligodeoxynucleotide (ASODN) into melanoma cells. Polymers and polymer/ASODN complexes were characterized by DLS according to size, charge, and critical micelle concentration. Nanosize and spherical complexes were observed by AFM. Complexes did not reveal significant toxicity to melanoma cells. Antiproliferative effect of the complexes was observed by immunocytochemical staining and estimated as 56.8% with N/P:9. High amount of apoptosis and very small amount of necrosis were estimated. According to the results, these positively charged polymers forming micelle-like structures seem promising as ASODN carriers.

Polyethylenimine Modified and Non-Modified Polymeric Micelles Used for Nasal Administration of Carvedilol.

This study evaluates the ability of polyethylenimine-modified and non-modified polymeric micelles to enhance permeation through the nasal mucosa for a highly hydrophobic model drug. Carvedilol was loaded into polyethylenimine-modified and non-modified micelles by direct dissolution. Formulations were characterised by critical micelle concentration, micelle particle size and distribution, zeta potential, morphological structure and entrapment efficiency. The drug entrapment efficiency was determined to be as high as 77.14%, while micelle particle sizes and zeta potentials were within the range of 140.0-279.9 nm and (- 40.6)-(+ 25.9) mV, respectively. In vitro studies showed 100% release of carvedilol from micelles in 120 hours. Ex vivo permeation studies showed that the drug in polyethylenimine non-modified micelles passed more efficiently than the drug in polyethylenimine modified micelles. These results demonstrated that polyethylenimine modified micelles did not significantly affect the permeation of the drug when compared to polyethylenimine non-modified micelles. On the contrary, the drug in poly(L-lactide)-block-methoxy poly(ethylene glycol)5000 micelles, the polyethylenimine non-modified micelles, showed the highest permeation rate through bovine nasal mucosa. In conclusion, poly(L-lactide)-block- methoxy poly(ethylene glycol)5000 polymeric micelles maybe useful as novel drug carriers that increase the permeation through the nasal mucosa.

In vitro transfection of HeLa cells with temperature sensitive polycationic copolymers.

In this study, we investigated different types of polyethyleneimine (PEI) and their block copolymers with N-isopropylacrylamide (NIPA) as temperature-sensitive polycationic non-viral vectors for transfection of HeLa cells in cell culture media. First carboxyl-terminated poly(NIPA) was synthesized and then copolymerized with PEIs branched or linear and with two different molecular weights (2 and 25 kDa). Addition of PEI units to the poly(NIPA) chains increased the LCST values up to body temperature. Zeta potentials of the copolymers were significantly lower than the corresponding PEI homopolymers. A green fluorescent protein expressing plasmid was used as a model. Complexes of this plasmid both with PEIs and their copolymers were formed. The zeta potentials of these complexes were between -3.1 and +21.3. Higher values were observed for the complexes prepared with branched and higher molecular weight PEIs. Copolymerization caused a profound decrease in the positive charges. Particle sizes of the complexes were in the range of 190-1235 nm. Using high polymer/plasmid ratios caused aggregation. The smallest complexes were obtained with the copolymer prepared with branched PEI with 25-kDa molecular weight. Copolymers were able to squeeze plasmid DNA more at the body temperature. Cytotoxicity was observed with PEIs especially with the branched higher molecular weights. Copolymerization reduced the cytotoxicity. The best in vitro DNA uptake efficiency (70%) was achieved with the complex prepared with poly(NIPA)/PEI25B. However, poly(NIPA)/PEI25L was the most successful vector for an effective gene expression without any significant toxicity.

Observation of phase transition of thermo-responsive poly(NIPA)-PEI block copolymers by STM.

N-isopropylacrylamide (NIPA) homopolymers having carboxylic acid-end groups were synthesized by using mercaptoacetic acid (MAA) as the chain transfer agent. Polymerization was achieved in ethanol using azobisisobutyronitrile (AIBN) as the initiator. Average molecular weight of the homopolymer estimated by titration was 1958. This carboxylic acid-ended poly(NIPA) was then copolymerized with polyethylenimine (PEI, M(W)-2000) using a water soluble carbodiimide (EDAC). With respect to carboxyl-ended poly(NIPA), the block copolymers exhibited a pH dependent-temperature sensitivity and higher LCST values in acidic pH. Scanning tunneling microscopy (STM) images of both the homopolymer and the copolymer were obtained at 25 and 45 degrees C with tip-sample bias voltages of up to 800 mV and tunneling currents approximately 1 nA. These images showed that STM can be used to visualize both the formation of copolymer chains and their structure, and also their stimuli-responsive behavior.