Enhanced osteogenic potential of human mesenchymal stem cells on electrospun nanofibrous scaffolds prepared from eri-tasar silk fibroin Niladri nath Panda, 1 Amit Biswas, 1 Krishna Pramanik, 1 Sriramakamal Jonnalagadda 2 1 Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela-769008, Odisha, India 2 Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, USciences, Philadelphia, Pennsylvania 19104 Received 22 April 2014; revised 9 July 2014; accepted 6 August 2014 Published online 00 Month 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.b.33272 Abstract: This study evaluated the mechanical properties and osteogenic potential of a silk fibroin scaffold prepared from a 70:30 blend of Eri (Philosamia ricini) and Tasar (Antheraea mylitta) silk, respectively (ET scaffolds). An electrospinning pro- cess was used to prepare uniformly blended, fibrous scaffolds of nanoscale dimensions, as confirmed by scanning and trans- mission electron microscopy (fiber diameter < 300 nm). Simi- larly prepared scaffolds derived from gelatin and Bombyx mori (BM) silk fibroin were used as controls. Mechanical testing and atomic force microscopy showed that the ET scaffolds had sig- nificantly higher tensile strength (1.83 6 0.13 MPa) and surface roughness (0.44 lm) compared with BM (1.47 6 0.10 MPa; 0.37 lm) and gelatin scaffolds (0.6 6 0.07 MPa; 0.28 lm). All scaf- folds were exposed to mesenchymal stem cells isolated to human chord blood (hMSCs) for up to 28 days in vitro. Alamar blue and alkaline phosphatase assay showed greater attach- ment and proliferation for both ET and BM scaffolds compared with gelatin. The ET scaffolds also promoted greater differen- tiation of the attached hMSCs as evidenced by higher expres- sion of RunX2, osteocalcin, and CD29/CD44 expression. ET scaffolds also showed significantly higher mineralization, as evidenced by glycosaminoglycan assay, alizarin red staining, and elemental analysis of crystalline composites isolated from the scaffolds. V C 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000–000, 2014. Key Words: bioactive material, stem cells, scaffolds, osteo- genesis, nanomaterials/nanophase How to cite this article: nath Panda, N, Biswas, A, Pramanik, K, Jonnalagadda, S. 2014. Enhanced osteogenic potential of human mesenchymal stem cells on electrospun nanofibrous scaffolds prepared from eri-tasar silk fibroin. J Biomed Mater Res Part B 2014:00B:000–000. INTRODUCTION Silk fibroins are biomaterials used extensively as surgical sutures for centuries. 1,2 More recently, they have found applications as scaffolds for tissue engineering 3–5 and as drug delivery systems. 6–8 The most comprehensively studied silks are those derived from the domesticated mulberry silk- worm [Bombyx mori (BM)], 5,9–11 selected species of spiders (Nephila clavipes 12–14 and Araneus diadematus). 15–18 Com- pared with most natural and synthetic biomaterials, silk fibroins are particularly attractive for load bearing applica- tions in bone remodeling because of their hypoallergenic, antimicrobial, and biodegradable characteristics. 19 Silk fibroins are known for their high mechanical strength and can serve as alternatives to load bearing implants prepared from composites of bioresorbable polymers with calcium salts. Two specific implants have been clinically used as osteoconductive fixation and consist of the MILAGRO or CALAXO screw. 20 A randomized controlled trial evaluating the use of both screws for anterior cruciate ligament recon- struction has showed intratunnel cyst formation, tunnel widening, and no evidence of tunnel ossification. 20 The CALAXO screw was recalled in 2007 because of postopera- tive complications. 21 Although B. mori is of particular interest, a main protein sequence consisting of the nonpolar amino acids glycine and alanine in this silk fibroin could limit cell growth and proliferation compared with other natural proteins such as collagen and gelatin. 22 Tasar silk fibroin, derived from Antheraea mylitta possess the RGD (arginine–glycine–aspar- tic acid) epitope in its backbone, and has been shown to be a better substrate for cell adhesion compared with collagen and silk derived from B. mori. 23 Tasar silk has a hydrophilic to hydrophobic amino acid ratio of 0.44 compared with only 0.28 for B. mori. 24 The higher hydrophilic ratio, although beneficial for cell adhesion, can be limiting with respect to mechanical strength and degradation time in vivo. This is due to the tendency of hydrophilic polymers to absorb water and swell, making them susceptible to increased hydrolytic chain scission. This limitation can be overcome in eri silk derived from Philosamia ricini, known to have an This article was published online on 30 August 2014. An error was subsequently identified. This notice is included in the online and print versions to indicate that both have been corrected on 25 October 2014. Correspondence to: S. Jonnalagadda (e-mail: s.jonnal@usciences.edu) V C 2014 WILEY PERIODICALS, INC. 1