Contents lists available at ScienceDirect Materials Science & Engineering C journal homepage: www.elsevier.com/locate/msec Biodegradable bead-on-spring nanofibers releasing β-carotene for bone tissue engineering Setareh Esmailian a , Shiva Irani a, ⁎ , Hadi Bakhshi b, ⁎ , Mojgan Zandi c a Department of Biology, School of Basic Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran b Macromolecular Chemistry II, University of Bayreuth, Universitätsstraße 30, 95440 Bayreuth, Germany c Department of Biomaterials, Iran Polymer and Petrochemical Institute, Tehran, Iran ARTICLE INFO Keywords: Bead-on-spring fibers, β-carotene Mesenchymal stem cells Osteogenic differentiation Biodegradable ABSTRACT Bead-on-string mats based on poly(lactide-co-glycolide) (PLGA) releasing β-carotene (βC) as a natural osteogen were fabricated and used for bone tissue engineering. Mesenchymal stem cells (MSCs) seeded on the scaffolds successfully differentiated to osteoblasts without using any a differential medium. The mats showed a small burst of β-carotene (24–27%) during the first day and a sustained slow release up to 21 days. The MTT and SEM results indicated good attachment and proliferation of MSCs on the scaffolds. Calcination of scaffolds and expression of RUNX2, SOX9, and osteonectin genes approved the differentiation of seeded MSCs to osteoblasts without using any external osteogenic differential agent. The scaffold loaded with 4% β-carotene not only induced the early phase of osteogenesis but also advanced the differentiation to the osteoblast maturation phase. Thus, these bead- on-string scaffolds can be used as a substrate for direct bone tissue engineering. 1. Introduction The appearance of beads on fibers is usually considered as a nega- tive defect during electrospinning process, whereas almost all of the researchers try to optimize the spinning conditions for fabricating uniform and smooth fibers. For example, lower mechanical properties have been reported for beaded mats due to the concentration of stress between the beads and fibers [1, 2]. However, the presence of beads on fibrous mats, known as bead-on-spring structure [3], can provide un- ique properties such as higher surface roughness and hydrophobicity [4–6], selective wettability [7, 8], encapsulating drugs or other bio- molecules for sustained release [1, 2, 9–12] as well as applicability in photonics [3] and microelectronics [13]. Recently, beaded nanofibers have attracted many interests as drug releasing scaffolds for tissue engineering application. The size of beads is in micro-range, bigger than that of the nanofibers, thus they can act as reservoirs for bioactive cues [1, 10]. Gaharwar et al. [2] have used a beaded fibrous mat of poly(ethylene oxide terephthalate-b-butylene terephthalate) loaded with dexamethasone for the osteogenic differ- entiation of human mesenchymal stem cells (hMSCs). The beads acted as reservoirs for the sustained release of dexamethasone. More recently, Ding et al. [14] studied the synergistic effect of dexamethasone release and surface nanoroughness of beaded nanofibers on the osteodiffer- entiation of rat bone marrow MSCs. Results showed that the gradual release of dexamethasone into the culture medium promoted the dif- ferentiation of cells to osteoblasts, while the surface nanoroughness played a supporting role. Li et al. [1] have also entrapped bovine serum albumin (BSA)-loaded dextran particles within bead-on-string nano- fiber scaffolds made of poly(lactide-co-glycolide) (PLGA) for tissue en- gineering. In vitro release data showed a more sustainable release pro- file with less initial burst release. Bioactive cues encapsulated within nanofibers might facilitate the appropriate environment for cell attachment and proliferation [15–17]. β-carotene (βC) is the most abundant precursor of vitamin A in the human diet found in dark green and orange fruits and vegetables [18, 19]. It is a natural antioxidant used for the treatment of cancer and cardiovascular diseases and osteoporosis [20]. Due to the conjugated double bonds, β-carotene is electrical activity [21, 22](Fig. 1a). The ability of β-carotene for the osteogenic differentiation of stem cells has been reported [23–25]. Consequently, it is expected that the en- capsulation of this bioactive component in scaffolds can facilitate the osteogenic differentiation of stem cells on them [26]. This study aims to fabricate bead-on-spring fibrous mats releasing β- carotene as scaffolds for bone tissue engineering with ability to self- differentiate MSCs to osteoblasts without adding any differential agent. Poly (lactide-co-glycolide) (PLGA) was chosen as an FDA-approved biodegraded polymer for fabricating the scaffolds due to its degrad- ability and no cytotoxicity [1, 27, 28]. The morphology and drug https://doi.org/10.1016/j.msec.2018.07.030 Received 11 December 2017; Received in revised form 13 June 2018; Accepted 12 July 2018 ⁎ Corresponding authors. E-mail addresses: s.irani@srbiau.ac.ir (S. Irani), hadi.bakhshi@uni-bayreuth.de (H. Bakhshi). Materials Science & Engineering C 92 (2018) 800–806 0928-4931/ © 2018 Published by Elsevier B.V. T