Fabrication of robust poly l-lactic acid/cyclic olefinic copolymer (PLLA/COC) blends: study of physical properties, structure, and cytocompatibility for bone tissue engineering

Abstract

Poly (l-lacticacid) (PLLA) is an FDA approved material for bone tissue engineering but its inherent brittleness and low melting ability are major challenges for its large-scale commercial applications. This challenge can be overcome by making its blends. This study reports blends of PLLA with a relatively new class of polymer i.e. cyclic olefinic copolymer and their miscibility, thermal behavior, morphology, crystallinity, degradability, and excellent biocompatibility is evaluated. Blends were prepared by taking 5–30 weight percent COC with PLLA matrix using solvent casting method. Scanning electron microscopy (SEM) images revealed that PLLA/COC form miscible blends up to 5–20 wt% of COC. FTIR, XRD, and differential scanning calorimetry (DSC) data showed that addition of COC to PLLA resulted in decrease in crystallinity along with formation of new α′-crystalline phase which coexists with inherent α-phase of PLLA in the blends. The transformation of α′-form is due to the presence of Van der Waals forces of interactions of the polymer chain moieties between PLLA and COC. Interestingly, PLLA/COC blends exhibited superior mechanical properties in relation to the pure PLLA. Compressive modulus values for PLLA/COC 10wt% increased 117% as compared to pure PLLA. PLLA/COC blends at 10 wt% have maximum ultimate tensile strength, modulus, and toughness ~ 123%, 67.8% and, 18.87% respectively. PLLA/COC blends showed increased swelling and degradation results as compared to PLLA. PLLA/COC blends exhibited excellent cytocompatibility over PLLA with preosteoblast (MC3T3-E1) and bone marrow stem cells (BMSc) cell lines suggesting possible candidate for Bone Tissue Engineering.

Keywords

• Poly l-lactide
• Cyclic olefinic copolymer
• Blends
• Tensile and compressive strength
• Crystallinity
• Cytotoxicity