The success of gene therapy depends on safe and effective gene carriers. Despite being widely used, synthetic vectors based on poly(ethylenimine) (PEI), poly(l-lysine) (PLL), or poly(l-arginine) (poly-Arg) are not yet fully satisfactory. Thus, both improvement of established carriers and creation of new synthetic vectors are necessary. A series of biodegradable arginine-based ether-ester polycations was developed, which consists of three main classes: amides, urethanes, and ureas. Compared to that of PEI, PLL, and poly-Arg, much lower cytotoxicity was achieved for the new cationic arginine-based ether-ester polymers. Even at polycation concentrations up to 2 mg/mL, no significant negative effect on cell viability was observed upon exposure of several cell lines (murine mammary carcinoma, human cervical adenocarcinoma, murine melanoma, and mouse fibroblast) to the new polymers. Interaction with plasmid DNA yielded compact and stable complexes. The results demonstrate the potential of arginine-based ether-ester polycations as nonviral carriers for gene therapy applications.

Electrospun scaffolds from an amino acid containing poly(ester urea) (PEU) were developed as promising materials in the biomedical field and specifically in tissue engineering applications. The selected poly(ester urea) was obtained with a high yield and molecular weight by reaction of phosgene with a bis(α-aminoacyl)-α,ω-dioldiester monomer. The polymer having L-leucine, 1,6-hexanediol and carbonic acid units had a semicrystalline character and relatively high glass transition and melting temperatures. Furthermore it was highly soluble in most organic solvents, an interesting feature that facilitated the electrospinning process and the effective incorporation of drugs with bactericidal activity (e.g. biguanide derivatives such as clorhexidine and polyhexamethylenebiguanide) and enzymes (e.g. α-chymotrypsin) that accelerated the degradation process. Continuous micro/nanofibers were obtained under a wide range of processing conditions, being diameters of electrospun fibers dependent on the drug and solvent used. Poly(ester urea) samples were degradable in media containing lipases and proteinases but the degradation rate was highly dependent on the surface area, being specifically greater for scaffolds with respect to films. The high hydrophobicity of new scaffolds had repercussions on enzymatic degradability since different weight loss rates were found depending on how samples were exposed to the medium (e.g. forced or non-forced immersion). New scaffolds were biocompatible, as demonstrated by adhesion and proliferation assays performed with fibroblast and epithelial cells.

Synthetic cationic polymers are of interest as both nonviral vectors for intracellular gene delivery and antimicrobial agents. For both applications synthetic polymers containing guanidine groups are of special interest since such kind of organic compounds/polymers show a high transfection potential along with antibacterial activity. It is important that the delocalization of the positive charge of the cationic group in guanidine significantly decreases the toxicity compared to the ammonium functionality. One of the most convenient ways for incorporating guanidine groups is the synthesis of polymers composed of the amino acid arginine (Arg) via either application of Arg-based monomers or chemical modification of polymers with derivatives of Arg. It is also important to have biodegradable cationic polymers that will be cleared from the body after their function as transfection or antimicrobial agent is fulfilled. This chapter deals with a two-step/one-pot synthesis of a new biodegradable cationic polymer-poly(ethylene malamide) containing L-arginine methyl ester covalently attached to the macrochains in β-position of the malamide residue via the α-amino group. The goal cationic polymer was synthesized by in situ interaction of arginine methyl ester dihydrochloride with intermediary poly(ethylene epoxy succinimide) formed by polycondensation of di-p-nitrophenyl-trans-epoxy succinate with ethylenediamine. The cell compatibility study with Chinese hamster ovary (CHO) and insect Schneider 2 cells (S2) within the concentration range of 0.02-500 mg/mL revealed that the new polymer is not cytotoxic. It formed nanocomplexes with pDNA (120-180 nm in size) at low polymer/DNA weight ratios (WR = 5-10). A preliminarily transfection efficiency of the Arg-containing new cationic polymer was assessed using CHO, S2, H5, and Sf9 cells.

Abstract:A systematic study of fabricating nanoparticles (NPs) by cost-effective polymer deposition/solvent displacement (nanoprecipitation) method has been carried out. Five amino acid based biodegradable (AABB) ester polymers (four neutral and one cationic), four organic solvents miscible with water, and eight surfactants were tested for the fabrication of the goal NPs. Depending on the nature of the AABB polymers, organic solvents and surfactants, as well as on the fabrication conditions, the size (Mean Particle Diameter) of the NPs could be tuned within 42 ÷ 398 nm, the zeta-potential within 12.5 ÷ +28 mV. The stability (resuspendability) of the NPs upon storage (at room temperature and refrigerated) was tested as well. In Vitro biocompatibility study of the NPs was performed with four different stable cell lines: A549, HeLa (human); RAW264.7, Hepa 1-6 (murine). Comparing the NPs parameters, their stability upon storage, and the data of biological examinations the best were found: As the AABB polymer, a poly(ester amide) composed of L-leucine, 1,6-hexanediol and sebacic acid-8L6, as a solvent (organic phase-DMSO), and as a surfactant, Tween 20.

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