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Abstract:
In 2002, Robert Langer proposed that new polyester for tissue engineering should have good mechanical properties followed by: covalent bonding (as crosslinking) and hydrogen-bonding interactions; and should be elastic like rubber materials due to three-dimensional network structure. Considering these hypotheses, a polyester made of glycerol and citric acid was designed in this work. Poly(glycerol citrate) should be attractive for tissue engineering because both glycerol and citric acid, taking part in natural human metabolic pathways; and due to the reactant's functionality, 3D networks should be produced easily. Moreover, the reagents are cheap, available, and often used in the food and pharmaceutical industries. In this work, poly(glycerol citrate) was synthesized and then used with PLA for creating porous nonwovens by electrospinning. Produced materials were tested for possible application in the field of tissue engineering. The obtained materials have properties similar to collagen fibers, but still, require refinement for medical applications.

Keywords:
electrospinning, poly(glycerol citrate), polylactide, tissue engineering

Abstract:
This study was conducted as a first step in obtaining eco-friendly fibres for medical applications using a synthesised oligomer poly(glycerol succinate) (PGSu) as an additive for synthetic poly(L-lactic acid) (PLLA) and poly (L-lactide-co-caprolactone) (PLCL). The effects of the oligomer on the structure formation, morphology, crystallisation behaviour, and mechanical properties of electrospun bicomponent fibres were investigated. Nonwovens were investigated by means of scanning electron microscopy (SEM), wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and mechanical testing. The molecular structure of PLLA fibres is influenced by the presence of PGSu mainly acting as an enhancer of molecular orientation. In the case of semicrystalline PLCL, chain mobility was enhanced by the presence of PGSu molecules, and the crystallinity of bicomponent fibres increased in relation to that of pure PLCL. The mechanical properties of bicomponent fibres were influenced by the level of PGSu present and the extent of crystal formation of the main component. An in vitro study conducted using L929 cells confirmed the biocompatible character of all bicomponent fibres.

Keywords:
poly(glycerol succinate), plasticiser, eco-friendly polymer, electrospinning, hyperbranched polyester

Abstract:
Two types of poly(glycerol sebacate) (PGS) prepolymers were synthesized and electrospun with poly(l-lactic acid) (PLA), resulting in bicomponent nonwovens. The obtained materials were pre-heated in a vacuum, at different times, to crosslink PGS and investigate morphological and structural dependencies in that polymeric, electrospun system. As both PGS and PLA are sensitive to pre-heating (crosslinking) conditions, research concerns both components. More interest is focused on the properties of PGS, considering further research for mechanical properties and subsequent experiments with PGS synthesis. Electrospinning of PGS blended with PLA does not bring difficulties, but obtaining elastomeric properties of nonwovens is problematic. Even though PGS has many potential advantages over other polyesters when soft tissue engineering is considered, its full utilization via the electrospinning process is much harder in practice. Further investigations are ongoing, especially with the promising PGS prepolymer with a higher esterification degree and its variations.

Keywords:
electrospinning, degradable polymers, synthesis, structure, crosslinking