Morphology-induced hydrophobic behavior of electrospun polyhydroxyalkanoate membranes
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Morphology-induced hydrophobic behavior of electrospun polyhydroxyalkanoate membranes Maraolina Domínguez-Díaz1,3, Angel Romo-Uribe1*, Araceli Flores2 and Rodolfo Cruz-Silva3 1 Lab. De Nanopolimeros y Coloides, Instituto de Ciencias Físicas, Universidad Nacional Autonoma de Mexico, Cuernavaca Mor. 62210, MEXICO 2 Instituto de Estructura de la Materia, C.S.I.C., Serrano 119, 28006 Madrid, SPAIN 3 Centro de Investigación en Ingeniería y Ciencias Aplicadas, UAEM, Cuernavaca Mor. 62210, MEXICO * To whom correspondence should be addressed: [email protected] ABSTRACT Biodegradable poly(3-hydroxybutyrate) -PHB- and the copolymers with poly (3hydroxyvalerate) -PHB/HV, containing 5 and 12 mol% valerate (denoted PHB/5HV and PHB/12HV, respectively) were electrospun from chloroform solution at room temperature. The results showed that relatively low voltage and concentrations favored uniform filament formation in PHB, with filament diameters ranging from 3 to 7 micrometers. On the other hand, low molecular weight and low solution concentration favored uniform filament formation in the PHB/5HV copolymer. Strikingly, morphology of filaments and beads favored the membranes hydrophobic behavior; the membrane from PHB/12HV exhibited a water contact angle of 112°. In contrast, solution cast films from the PHAs exhibited water contact angles in the range of 65°. Analyses on the membranes morphology via scanning electron microscopy (SEM) revealed that filament diameter drives the degree of porosity and the hydrophobic behavior of the electrospun membranes. INTRODUCTION Polyhydroxybutyrate (PHB) is a naturally occurring polyester that accumulates in bacterial cells as a carbon and energy storage compound [1]. Poly(3-hydroxybutyrate) (PHB) and its copolymers with poly-3-hydroxyvalerate (PHBV) represent biodegradable and biocompatible materials [2] with great expectations in the biomedical field, e.g., surgical sutures, drug delivery, coating for cardiovascular implants, and scaffolding in tissue engineering [3]. However the intrinsic hydrophobic properties of PHAs restrict applications as cell colonizing materials. The surfaces of PHB and PHBV are quite inert and hydrophobic and have no physiological activity. This is unfavorable for adhered cell growth. Therefore, as for many polymer surfaces, the cytocompatibility should be improved by either chemical modification with functional groups or modification of the surface topography. Both parameters play an important role in the interaction between a biomaterial surface and cells [4]. Hence, it is important to develop methods to tune the hydrophobic behavior of PHAs. One method to change hidrophobicity is by chemical modification [5], for which is necessary to carry out functionalization and grafting reactions. Another route could be to modify the polymer’s surface. This can be achieved by, say, polymer electrospinning. Electrospinning is an effective technique to produce fibers by applying electrostatic forces to a polymer solutions thus
elongating the polymer chains and producing
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