PSI - Issue 43

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Author name / Structural Integrity Procedia 00 (2022) 000 – 000

72 This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under the responsibility of MSMF10 organizers. Komal P. Malla et al. / Procedia Structural Integrity 43 (2023) 71–76

Keywords: electronspun polymer blend, nano-hydroxyapatite, morphology, mechanical properties, microdeformation behavior

1. Introduction Recently, composites of biopolymers and bioceramics have attracted increasing attention in the scientific community for their use as scaffolds in bone tissue engineering (BTE). Among others, polycaprolactone (PCL), poly L-lactic acid (PLLA), and gelatin (GEL) are the most studied biopolymers because of their nontoxicity, excellent biocompatibility, and biodegradable nature (Shuai et al., 2020; Scaffaro et al., 2017). Furthermore, the US Food and Drug Administration (FDA) has approved PCL and PLLA for clinical use in humans (Remya et al., 2013; Su et al., 2014; Zhang et al. 2019). For decades, the scaffolds of these biopolymers have been used in various biomedical applications such as bone tissue engineering, medication delivery transporters, implant coatings, 3D printing composites, and orthopaedics for restorations and revivals of bone cells, despite their weak mechanical properties (Ba Linh et al., 2013; Nithya and Sundaram, 2015; Shitole et al., 2019). Nevertheless, it has been shown by two independent groups of authors that bulk samples of PLA/PCL blends with optimized morphology may exhibit both high stiffness and toughness (Bai et al., 2013; Fortelny et al., 2019). Therefore, there have been numerous studies to enhance the mechanical properties of these scaffolds by incorporating different filler materials, i.e., various synthetic and biomaterials such as chitosan, bioglass, minerals, ceramic materials, etc. (Hossan et al., 2015). Among the various members of calcium phosphate, due to its bioactive and biocompatible nature nano-hydroxyapatite (nano HAp) is extensively used as a filler to enhance the mechanical properties and osteoconductivity of scaffolds for BTE (Shuai et al., 2020). Several procedures have been devised to fabricate such scaffolds, including electrospinning, which was also used in this study. HAp has been already frequently used as filler in electrospun scaffolds, also in the form of nanosized powder (Ito et al., 2005; Hezma et al., 2017). However, the HAp used is almost nearly synthetic in nature and not biobased. In the past few decades, several studies have attempted to explain the mechanical behavior of HAp-blended electrospun binary composite scaffolds of PCL/PLLA, PCL/GEL, and PLLA/GEL (Hossan et al., 2015; Andersson et al., 2014; Sánchez - Arévalo et al., 2017; Selezneva et al., 2018). However, the micromechanical behavior of nano HAp-incorporated ternary blends of PCL/PLLA/GEL scaffold has not been studied yet. Therefore, in this work, we aim to fabricate non-woven fibrous scaffolds with different volume fraction percentages of nano-HAp/TFE suspension blended into ternary composite mixtures of PCL/PLLA/GEL by electrospinning technique and to study the effect of filler addition on the micromechanical behavior after tensile testing of the scaffold fibers. 2. Preparation and Morphology of the Scaffolds The scaffolds are ternary biopolymer blends composed of polycaprolactone (PCL), poly-L-lactic acid (PLLA), gelatin, and vitamin D3 filled with different volume fraction percentages (maximum 12 %) of nano-hydroxyapatite (nano-HAp) (more information about the materials is given in Malla et al. (2020)). The nano-HAp used in this study was extracted from ostrich femur bones by thermal decomposition method in our earlier studies (Malla et al., 2020). All the polymers were dissolved in 2,2,2-trifluoroethanol (TFE) under magnetic stirring to obtain a 10 % (w/v) solution of each polymer separately. The 5 % (w/v) nano-HAp/TFE suspension was prepared separately and blended into the above polymer mixture, then magnetically stirred to obtain the nano-HAp-blended polymer solutions. The solutions were used for electrospinning of randomly oriented fibrous scaffolds collected in a rotatory drum. For details of the electrospinning process and further information on the scaffolds see Malla et al. (2022). For comparison solution cast films of about 0.3 mm thickness were prepared from the solutions as described above. The morphology and allocation of the randomly oriented nanofibers of the scaffolds before and after the tensile test were examined by using scanning electron microscopy (SEM, FEI Quanta 650 ESEM-FEG, accelerating voltage: 15 kV). For this, cut scaffold samples were attached to SEM stubs using double-sided conductive adhesive