Hybrid scaffolds constituted by a mixture of conducting and biodegradable polymers have been obtained by the electrospinning technique. Specifically, poly(3-thiophene metyl acetate) (P3TMA) and a copolymer derived from L-leucine which bears ester, urea and amide groups (PEU-co-PEA) have been employed. Both polymers have been selected because of their intrinsic properties and their high solubility in organic solvents. The biodegradable polymer renders continuous and homogeneous microfibers in most of the electrospinning conditions tested, appearing as an ideal carrier for the polythiophene derivative.A spontaneous phase separation has been observed for concentrated solutions of PEU-co-PEA and P3TMA in chloroform:methanol mixtures. The dense phase results enriched on the conducting polymer and can be successfully electrospun giving rise to scaffolds with up to 90 wt-% of P3TMA. Morphologic observations have indicated that continuous and regular microfibers are attained despite the high conducting polymer content. P3TMA presents a high doping level and leads to stable electrospun scaffolds by the simple addition of a low percentage of a high molecular weight carrier. The resulting scaffolds are practically amorphous and thermally stable, presenting also a pronounced electrochemical response and being electrochemically active. Thus, the formation of polarons and bipolarons at specific positions, the ability to exchange charge reversibly and the electrical stability of hybrid PEUco-PEA/P3TMA electrospun scaffolds and P3TMA alone are practically the same.
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.
Purpose: Drug delivery to treat ocular diseases still is a challenge in ophthalmology. One way to achieve drug delivery that is investigated currently is topical administration of drug-loaded polymeric nanoparticles (NPs) that are able to penetrate ocular barriers. The purpose of this study was optimal preparation of NPs made from pseudo-proteins and evaluation of their ability to penetrate ocular tissues. Methods: Biodegradable NPs of various types were prepared by nanoprecipitation of pseudo-protein composed of l-leucine (L), 1,6-hexanediol (6), and sebacic acid (8) (8L6). Arginine-based cationic polyester amides 8R6 and comb-like polyester amide containing lateral PEG-2000 chains along with 8L6 anchoring fragments in the backbones were used to construct positively charged and PEGylated NPs. They were loaded with fluorescein diacetate (FDA) or rhodamine 6G (Rh6G) as fluorescent probes. Suspensions of the NPs were given to cultivated microglial cells and retinal pigment epithelial (RPE) cells as well as topically on eyes of C57BL/6 mice. Penetration of NPs into the eyes was checked by fluorescence analysis. Results: NPs were prepared, and their properties were characterized. Cultured microglial cells and RPE cells took up the NPs. After topical administration, penetration of NPs into the cornea of the eyes was clearly seen. Small amounts of fluorescent dyes were also found in the lens, the retina, and the sclera depending on the type of NPs. Conclusions: The results showed that the new NPs penetrate ocular tissues after topical administration and are internalized by the cells. This raises confidence that the NPs may be useful carriers of therapeutic agents for ocular delivery.
New biodegradable amino acid based biodegradable (AABB) ester polymers having a potential for constructing resorbable surgical and therapeutical devices were synthesized by solution step-growth polymerization (SGP) of bis-azlactones (BALs) with dip -toluenesulfonic acid salts of bis-(α-amino acid)-α,ω-alkylene diesters (TDADEs). Relatively low-molecularweight homopolymers-poly(ester amide)s with Mw within 2,800-19,600 Da (GPC in DMF) were obtained. To increase molecular weights of the goal AABB ester polymers two additional synthetic strategies were appliedeither activated diester such as dip -nitrophenyl sebacate was used as a comonomer of BAL, or alkylene diamine such as 1,6-hexamethylenediamine was used as a comonomer of TDADE. As a result high-molecular-weight AABB ester polymers with Mw up to 103,500 Da were synthesized depending on co-monomers' structure and mole ratios. All the BAL-based polymers obtained after SGP were practically[J1] amorphous. The thermograms (DSC) of the polymers made of the BAL F showed wide endotherms within 55-120 o C. These endotherms were assigned to melting hydrophobic domains formed by highly hydrophobic fragments-residues of phenylalanine-based bis-azlactone (BAL F) in the polymeric backbones. The obtained new BAL-based ester polymers substantially expands a family of AABB polymers destined for constructing resorbable surgical and pharmaceutical devices.
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