Alfonso Rodríguez-Galán

Synthesis and characterization of a family of biodegradable poly(ester amide)s derived from glycine

A series of aliphatic poly(ester amide)s derived from 1,6-hexanediol, glycine, and diacids with a variable number of methylenes (from 2 to 8) have been synthesized and characterized. Infrared spectroscopy shows that the studied polymers present a unique kind of hydrogen bond that is established between their amide groups. Thermal properties as melting, glass transition, and decomposition temperatures are reported. The data indicate that all the polymers are highly crystalline. Thus, different kinds of spherulites (positive and/or negative) were obtained depending on the preparation conditions and on the polymer samples. Moreover, all the polymers crystallized from dilute diol solutions as ribbonlike crystals where a regular folding habit and a single hydrogen bond direction could be deduced. A test of enzymatic hydrolysis was employed to assess the potential biodegradability of these polymers.

Studies on the biodegradation and biocompatibility of a new poly(ester amide) derived from L-alanine

A new poly(ester amide) derived from L-alanine has been synthesized and characterized. The polymer has good fiber- and film-forming properties, as well as other characteristics like thermal stability and solubility in chloroform, which enhance its processing facilities. Degradation studies show that both pH and temperature influence in the hydrolisis rate that takes mainly place through the ester linkages. Degradation was also studied by using different enzymes. Results indicated that papain was the most efficient of these, and that the hydrolysis to water-soluble products could be attained in a few days. Basal cytotoxicity was assayed using a mouse L929 fibroblast permanent cell line. The MTT viability test was performed with liquid extract of the material (50 days, 37°C). An attachment and proliferation screening study with intact material was also carried out. No cytotoxic responses were detected, in either assay, after a 24- and 48-h incubation period with the cells. After 72 h a slight cytotoxicity was detected in the polymer material, while a more significant one was detected in the material extract.

Study on the degradability of poly(ester amide)s derived from the α-amino acids glycine, and l-alanine containing a variable amide/ester ratio

Abstract Two series of poly(ester amide)s prepared from sebacic acid and different ratios of 1,12-dodecanediamine and a diamine that contains both α-amino acid residues and ester groups have been synthesized and characterized. In order to maintain hydrogen bonding interactions, two diamines with the same number of main chain atoms were selected. The series differ on the nature of the α-amino acid residue: glycine or l -alanine. The calorimetric analysis shows that melting temperatures increase as the amide/ester ratio does. Polymers derived from l -alanine show lower crystallinities and melting temperatures than those constituted by glycine units. Hydrolytic and enzymatic degradabilities of both series of poly(ester amide)s have also been studied. The ratio and nature of α-amino acid residues in the chemical repeat unit greatly affect the degradation rate.

Comparative studies on the degradability of poly(ester amide)s derived from L‐ and L,D‐alanine

The hydrolytic degradation of two poly(ester amide)s derived from sebacic acid, dodecanediol, and alanine in both the quiral L configuration and the racemic L,D mixture has been studied. The degradation was monitored by following the changes in intrinsic viscosity, mass loss, chemical constitution, and mechanical properties. The results show that these poly(ester amide)s degrade slowly at 37°C through the ester linkage. Little changes in the Youngs modulus of both samples were found at the beginning of the degradation process. Biodegradation has also been studied by using different enzymes. Papain was the most effective one, although the degradation rate was dependent on the stereochemical composition of the polymer.

Degradable poly(ester amide)s based on l-tartaric acid

Abstract A series of poly(ester amide)s with ester/amide group ratios ranging from 1 99 to 1 4 were obtained using 1,6-hexanediamine, 1,6-hexanediol and 2,3-di-O-methoxy- l -tartaric and succinic acids as building blocks. The ester linkages were introduced in pairs using as comonomer the diacid resulting from the esterification of 1,6-hexanediol with 2 mol of succinic anhydride. Polycondensastion reactions were carried out in solution at room temperature with the diamine activated as the N,N′-bis(trimethylsilyl) derivative and the two diacids as bis(pentachlorophenyl) esters. The prepared poly(ester amide)s have number average molecular weights in the range 10 000–40 000, display optical activity and are soluble in chloroform. These copolymers were found to be highly crystalline with melting points above 200°C and mechanical moduli comparable to those reported for the parent polyamide poly(hexamethylene-di-O-methyl- l -tartaramide). They were degraded by aqueous buffer of pH 7.4 at a rate that increased with the content of the copolymer in succinic acid units. 1H n.m.r. evidenced that no reactions other than those entailing the hydrolysis of the main chain ester bonds appear to take place at polymer degradation.

Studies on the degradability of a poly(ester amide) derived from L-alanine, 1,12-dodecanediol and 1,12-dodecanedioic acid

Abstract A new aliphatic poly(ester amide) derived from l -alanine has been synthesized and characterized. Degradability in different media has been studied and compared with BIOPOL, a well-known biodegradable polymer. The new poly(ester amide) shows a hydrolytic degradation that takes place through the ester linkage and an enzymatic degradation that strongly depends on the type of enzyme. Thus, proteolytic enzymes such as papain and proteinase K are the most effective ones. Biodegradation by microorganisms from soils and activated sludges has also been evaluated. Results indicate that BIOPOL degrades faster with microorganisms than the new polymer does.

Study on the degradability of poly(ester amide)s related to nylons and polyesters 6,10 or 12,10

A series of random poly(ester amide)s with different chemical compositions and derived from sebacoyl dichloride, 1,6-hexanediamine and 1,6-hexanediol was synthesized and characterized. In addition, a poly(ester amide) with equal ratio of 1,12-dodecanediamine and 1,12-dodecanediol units was prepared. All these poly(ester amide)s were obtained by interfacial polymerization with high yields. Thermal behavior, mechanical properties, crystallinity and degradability were studied and compared with the parent polyesters (6,10 and 12,10) and nylons (6,10 and 12,10). The new poly(ester amide)s were hydrolyzable, the degradation rate depending on the ester/amide ratio and the methylene content of the diol or diamine units. On the contrary, they were not degraded with proteolytic enzymes. This observation contrasts with the behavior of related poly(ester amide)s that include α- amino acid units in their composition.

Poly(ester amide)s derived from 1,4-butanediol, adipic acid and 6-aminohexanoic acid. Part II: composition changes and fillers

BAK poly(ester amide)s differing in the amide/ester ratio have been synthesized and characterized, considering spectroscopic data and both thermal and mechanical properties. Degradability under different media (water at 70 °C, acid or enzymatic catalysis at 37 °C) has also been studied by evaluating the changes in intrinsic viscosity, in the NMR spectra and in the surface texture of samples. The use of chain extenders, such as hexamethylene diisocyanate and 1,3-butadiene diepoxide, has been investigated and the optimal reaction conditions are reported here. Changes on mechanical properties due to the incorporation of biodegradable reinforces have also been evaluated. Finally, the synthesis and determination of thermal properties of related poly(ester amide)s constituted by glutaric or succinic acid instead of adipic acid have been investigated.

Biodegradable free-standing nanomembranes of conducting polymer:polyester blends as bioactive platforms for tissue engineering

The present study reports the fabrication of free-standing nanomembranes with semiconducting and biodegradable properties. Nanomembranes have been prepared by spin-coating mixtures of a semiconducting polythiophene derivative, poly(3-thiophene methyl acetate), and a biodegradable polyester, poly(tetramethylene succinate). Both the roughness and thickness of the nanomembranes, which ranged from 3 to 20 nm and from 20 to 80 nm, respectively, were precisely controlled through the spin-coater speed and the solvent evaporation properties. Nanomembranes made of conducting polymer/polyester blends, which are able to retain the properties of the individual polymers, are stable in air and in ethanol solution for more than one year, facilitating their manipulation. Enzymatic degradation essays indicated that the ultra-thin films are biodegradable due to the presence of the aliphatic polyester. Interestingly, adhesion and proliferation assays with epithelial cells revealed that the behavior of the blend as cellular matrix is superior to that of the two individual polymers, validating the use of the nanomembranes as bioactive substrates for tissue regeneration.

Poly(ester amide)s derived from 1,4-butanediol, adipic acid and 1,6-aminohexanoic acid: characterization and degradation studies

The commercial biodegradable copolymer BAK 1095 has been studied by means of spectroscopy, X-ray diffraction and calorimetry. Degradability has been evaluated in different media (hydrolytic at distinct temperatures and pHs, and enzymatic) by evaluating the changes in intrinsic viscosity, in the NMR spectra, in mechanical properties and in the surface texture of samples. In addition, a new poly(ester amide) with a regular distribution of the monomers implied in BAK 1095 has also been synthesized and its characteristics compared with the reference polymer.