Poly-L-ornithine

Polymers of poly(L-ornithine) possessing varying contents of azobenzene groups, from 20% up to almost 100% [Scheme 5, VIII (n= 3)], were found to be essentially a-helical in HFP when the samples were kept in the dark. The CD spectra also exhibited a couplet of bands centered at about 320 nm, attributed to electronic interactions between the azo side chains in the trans configuration. Irradiation at 360 nm and the consequent trans—xis photoisomerization, abolished the side chain CD... 

A sample of poly(L-ornithine) containing 48 mol% azo units was found to adopt the a-helix structure in HFP/water = 1/1. In this solvent mixture, however, irradiation at 360 nm followed by irradiation at 460 nm produced the trans-cis photoisomerization of the azo moieties, but did not induce any change of the backbone conformation. When the surfactant sodium dodecyl sulfate was added to the HFP/water solvent mixture, the CD spectrum displayed an intense side chain CD couplet and a negative band at about 225 nm which was assigned to the presence of a P-structure. The CD bands were almost completely abolished upon trans-cis photoisomerization. 

Neural stem cells are known for their sensitivity to the environment. Jan and Kotov reported the differentiation of mouse embryonic neural stem cells on SWNT-polyelectrolyte multilayer thin films [poly(ethylene imine) PEI/SWNT, six layers], which were assembled layer by layer.111 The cells were successfully differentiated to neurons, astrocytes, and oligodendrocytes with a clear formation of neurites. Compared to the widely used poly(L-ornithine) (PLO) substrates, the six-layer PEI/ SWNT thin films exhibited similar properties in terms of biocompatibihty, neurites outgrowth, and the expression of neural markers.111... 

Satake I, Yang JT. Interaction of sodium decyl sulfate with poly(L-ornithine) and poly(L-lysine) in aqueous solutions. Biopolymers 1976 15 2263-2275. 

Preclinical Results Obtained with Particles. Poly-L-lysine and poly-L-Ornithine were used to generate particles that can entrap pDNA. The cationic polymers can be coupled to a targeting molecule such as galactose or mannose for enhanced delivery to the liver after intravenous or intraportal injections in mice [102-104]. Expression in other organs than the liver (for example, kidneys) is observed however, expression in the liver using these particles is dominant. Such particles are found to be more efficient and to persist for a longer time in the circulation than liposomes. Hepatic expression of the pDNA delivered by poly-L-Lysine particles can be found several months after delivery [105]. These promising formulations were not evaluated in humans. 

Yamamoto H, Nishida A, Takimoto T, Nagai A. 1990. Photoresponsive peptide and polypeptide systems. VIII. Synthesis and reversible photochromism of azo aromatic poly(L ornithine). J Polym Sci, Part A Polym Chem 28(1) 67 74. 

Poly-L-arginine(5), Poly-L-ornithine(6), a,P-Poly-aspartylhydrazide (7),... 

Abbreviation used CD, circular dichroism (Lys) , poly (L-lysine) (Orn)fj, poly (L-ornithine) NaDodS04, sodium dodecyl sulfate Na-DecS04, sodium decyl sulfate NaOctS04, sodium octyl sulfate Na-TetradS04, sodium tetradecyl sulfate NaHexadS04, sodium hexadecyl sulfate. 

Hiroynki, Yamamoto and Y7 Hirata, Gel properties as a hydrogel of crosslinked poly(L-ornithine) using organic cro.sslinking agents. Polymer Gels and Networks, 3 (1995) 71-84. 

Soluble polymer backbones that have been used to prepare these amphiphiles include poly(ethylenimine), poly(L-lysine), poly(L-ornithine) and glycol chitosan. These amphiphilic polymers either simply bear relatively low molecular weight hydrophobic pendant groups or in some cases possess additional hydrophilic substituents conjugated to the... 

Nead MA, McCance DJ. Poly-L-ornithine-mediated transfection of human keratonocytes. J Invest Dermatol 1995 105 668-671. 

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