Novel poly(amido-amine)-based hydrogels as scaffolds for tissue engineering

Biodegradable and biocompatible amphoteric poly(amido-amine) (PAA)-based hydrogels, containing carboxyl groups along with amino groups in their repeating unit, were considered as scaffolds for tissue engineering applications. These hydrogels were obtained by co-polymerising 2,2-bisacrylamidoacetic acid with 2-methylpiperazine with or without the addition of different mono-acrylamides as modifiers, and in the presence of primary bis-amines as crosslinking agents. Hybrid PAA/albumin hydrogels were also prepared. The polymerisation reaction was a Michael-type polyaddition carried out in aqueous media. The PAA hydrogels were soft and swellable materials. Cytotoxicity tests were carried out by the direct contact method with fibroblast cell lines on the hydrogels both in their native state (that is, as free bases) and as salts with acids of different strength, namely hydrochloric, sulfuric, acetic and lactic acid. This was done in order to ascertain whether counterion-specific differences in cytotoxicity existed. It was found that all the amphoteric PAA hydrogels considered were cytobiocompatible both as free bases and salts. Selected hydrogels samples underwent degradation tests under controlled conditions simulating biological environments, i.e. Dulbecco medium at pH 7.4 and 37 degrees C. All samples degraded completely and dissolved within 10 d, with the exception of hybrid PAA/albumin hydrogels that did not dissolve even after eight months. The degradation products of all samples turned to be non-cytotoxic. All these results led us to conclude that PAA-based hydrogels have a definite potential as degradable matrices for biomedical applications.     

Biodegradable composite films based on waste gelatin

Gelatin, a naturally occurring polymer, is currently used in various applications comprising manufacturing of pharmaceutical products, x-ray and photographic films development and food processing. However, gelatin scraps generated in the different manufacturing processes may constitute a concern for the environment. Basically speaking, waste disposal deriving from plastics based on synthetic as well as semisynthetic polymeric materials, is becoming an increasingly difficult problem for their unfavorable volume-to-weight ratio and extremely wide variability of type, shape and composition of post consume plastic items that hinder the way to a general unique option for a simple and economically feasible management. As a partial solution to the global issue of plastic waste, in recent years much interest has been devoted to the formulation of environmentally degradable plastic items. Biodegradable mulching films were formulated from blends and composites based on waste gelatin and other natural waste such as sugarcane bagasse or synthetic materials such as PVA. Also, crosslinked films were produced using external or inherent crosslinker. The films were produced either by casting method or spraying on soil surface. The composites were submitted to biodegradation trials. The results showed that the films were biodegradable and the crosslinking could delay and predeterminate their biodegradation rate and extent.     

Solvent induced structural transitions in a liquid crystalline polyester

Quenched nematic films of a liquid crystalline polyester were crystallized either thermally or by solvent induced crystallization, and their structural organization was analyzed. All techniques show that the thermal crystallization transforms part of the nematic phase into a crystalline one, the remaining part leaving unchanged. By contrast, the solvent induced crystallization does transform a part of the nematic phase into a crystalline phase, leaving the residual part in a much more disordered state resembling the amorphous state.     

Multifunctional polymeric materials for biomedical applications

The work performed by our research group during the last few years in the area of bioerodible-biodegradable polymers as designed to the formulation of systems for the controlled delivery of drugs and as specific sorbents of uraemic toxins is broadly reviewed. In particular, attention has been focused on the strategies adopted in the preparation of functional polymers containing hydroxyl or carboxyl groups, suitable to establish specific bonding and non-bonding interactions with conventional and proteic drugs.     

Multiblock copolymers of ε–caprolactone and ethylene glycol containing periodic side‐chain carboxyl groups: Synthesis,characterization, and nanoparticle preparation

Multiblock copolymers containing periodically spaced side‐chain carboxyl groups were obtained by a two‐step synthesis involving the preparation of ABA triblock prepolymers of ε‐caprolactone (A blocks) and ethylene glycol (B block) followed by chain extension to ABA_n multiblock copolymers by reaction with pyromellitic dianhydride (PMDA). NMR analysis demonstrated the incorporation of PMDA in polymer chain and revealed the possibility of PMDA units to exist in two isomers, cisoid and transoid forms. Chain extension resulted in the incorporation of free carboxylic groups in polymer backbone and in an almost twofold increase of molecular weight. Thermal analysis indicated that the presence of PMDA residues interferes with the formation of crystalline phases by the chain‐extended polymers. The polymers were found to slowly degrade in buffer solution at 37 °C. Further, the carboxylated polymers can be processed into nanoparticulates by nanoprecipitation. Depending on the selected organic solvent, the particulate was constituted by either a monodispersed nanoparticles with average size of 150 nm or a bimodal distribution centered at about 100 nm and 7 μm. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3800–3809     

Optically active vinyl polymers containing fluorescent groups—7: The distribution of monomeric units in cationically prepared copolymers of 9-vinylcarbazole and (−)menthyl vinyl ether

u.v. Absorption, ¹H-NMR, fluorescence emission and circular dichroism spectra together show clearly that stereoregular copolymers obtained cationically from 9-vinylcarbazole and (?)menthyl vinyl ether have significant block-like character. In contrast to results for related optically active copolymers, plots of circular dichroism absorption intensity versus copolymer composition exhibit a pronounced maximum corresponding to a molar composition 20% 9-vinylcarbazole, 80% (?)menthyl vinyl ether. This maximum does not correspond, as expected, with the presence of isolated carbazole units in a chiral polymer environment.     

Nuclear magnetic resonance spectra and structure of some alkyl vinyl sulphides

The NMR spectra of eight alkyl vinyl sulphides have been analyzed and the parameters compared with those obtained from an analogous series of oxygen derivatives. It is shown that a definite parallelism exists between chemical shifts and H? H coupling. Difference in absolute values have been explained by mesomeric interaction involving the ability of sulphur to accommodate a decet of electrons in its valence shell. By analogy with alkyl vinyl ethers, it is possible to predict a similar correlation between the spectral characteristics and relative reactivity of vinyl sulphides in cationic polymerization.     

Polymerization of mixtures of alkyl methacrylates or alkyl acrylates with 4-methyl-1-pentene by Ziegler-Natta catalyst

Mixtures of methyl methacrylate (MMA) and 4-methyl-1-pentene (4MP)(molar ratio MMA/4MP = 3–0.1) have been subjected to polymerization by VOCl₃/Al(C₂H₅)₃. The amorphous polymeric products, extractable with boiling methanol up to 75%, consist mainly of MMA monomeric units (～80%). The composition of the product was almost independent of the starting MMA/4MP ratio. Comparison of these results with thoseof homopolymerization experiments shows that the presence of MMA drastically reduces the polymerization rate of 4MP. Moreover, 4MP is polymerized with rather low stereospecificity in the presence of MMA. Fractionation by solvent extraction of the unchanged polymeric products as well as of hydrolyzed samples seems to exclude the formation of random copolymers, suggesting to us that the polymerization of the two monomers takes place by different mechanisms. On taking into account these data and analogous data obtained with 4MP and alkyl acrylates or tert-butyl methacrylate, is it suggested that, contrary to what has previously been proposed, the MMA polymerization by Ziegler-Natta catalysts does not take place at the same centers which polymerize 4MP; moreover a coordinated anionic mechanism for MMA polymerization does not seem to be very probable.     

Optisch aktive Kohlenwasserstoff-Polymere mit aromatischen Seitenketten. 7. Mitt. Synthese und Eigenschaften der Copolymeren von aromatischen Vinylmonomeren mit Chiral-α-Olefinen

Ohne Zusammenfassung