Influence of TiO₂ Nanoparticles Incorporated into Elastomeric Polyesters on their Biocompatibility In Vitro and In Vivo

Abstract

Polymer-matrix nanocomposites are an emerging group of biomaterials with enhanced mechanical characteristics and biological performance. Nanocomposites containing ceramic nanofillers embedded in a thermoplast or thermoset polymer matrix are an interesting group of materials in which desirable stiffness and biocompatibility can be achieved. However, many of these systems are rather stiff materials of limited elongation and, thus, application. Therefore, thermoplastic elastomers (TPE), as materials of high flexibility with wide range of stiffness and physical properties [1][2][3] represent interesting materials, especially for soft-tissue applications. [4] Novel materials, namely poly(aliphatic/aromatic-ester)s (PED) of segmented (multiblock) structure (hard/soft segments) have been synthesized by El Fray and Slonecki [5] and extensively investigated for biomedical applications. [6][7][8] PEDs are composed of semicrystalline poly(butylene terephthalate) (PBT) or poly(ethylene terephthalate) (PET) hard segments [9] and unsaturated dimer of linoleic acid (DLA) soft segments. PEDs can be synthesized without the use of thermal stabilizers, which are often irritants, due to the excellent oxygen and thermal stability of the soft segment (DLA) component. This feature is especially important if the material is intended for biomedical application. PED copolymers are biocompatible in vitro and in vivo and, when specially modified with active molecules, they show antibacterial properties. [10] In addition, their structure and properties can be modified with nanometer-size ceramic particles of hydroxyapatite [11] or nanocrystalline TiO 2 . [12] The materials showed impressive increases in mechanical properties, of up to 100% in tensile strength and 300% in elongation, compared to the neat (nanoparticle-free) polymer, thus resembling silicone elastomer in tensile stress (8 MPa) and strain (900%). Hydrolytic degradation studies showed that small amounts (from 0.2 up to 0.4 wt.-%) of TiO 2 nanoparticles can effectively control the material's susceptibility to degradation. [13] More importantly, PED modified with TiO 2 showed no hydroxyapatite precipitation from simulated body fluid (SBF), [14] which is an important indication for potential soft tissue implants (undesired calcification can be overcome).In this work, we present the results of in vitro and in vivo tests of these new elastomeric materials containing nanocrysFibroblasts proliferation and apoptosis as well as tissue response after implantation of elastomers containing nanocrystalline TiO 2 were investigated in the present in vitro and in vivo study. Materials investigated were soft poly(aliphatic/aromatic-ester) multiblock thermoplastic elastomers with poly(ethylene terephthalate) (PET) hard segments and dimerized linoleic acid (DLA) soft segments, respectively, containing 0.2 wt% TiO 2 nanoparticles. An investigation of the influence of TiO 2 nanoparticles incorporated into polymeric material on in vitro biocompatibility revealed enhanced cell proliferation and dimini...

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Transparent and flexible films of new segmented polyurethane nanocomposites incorporated by NH2-functionalized TiO2 nanoparticles

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