Carbohydrate Polymers 85 (2011) 111–119 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Electrospinning alginate-based nanofibers: From blends to crosslinked low molecular weight alginate-only systems Christopher A. Bonino a , Melissa D. Krebs b , Carl D. Saquing a , Sung In Jeong b , Kimberly L. Shearer a , Eben Alsberg b,c , Saad A. Khan a,∗ a Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC, United States b Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States c Department of Orthopaedic Surgery, Case Western Reserve University, Cleveland, OH, United States article info Article history: Received 20 October 2010 Received in revised form 12 January 2011 Accepted 1 February 2011 Available online 26 February 2011 Keywords: Biomaterials Nanotechnology Nanofibers Electrospinning Alginate Pluronic surfactant abstract We report here preparation of nanofibers containing alginate using two different molecular weights (MWs): 37 kDa and 196 kDa. Low MW alginates are attractive for in vivo tissue scaffolds where degrada- tion and clearance from the body are desirable, whereas higher MW alginates are amenable for topical use as wound coverage because of its better mechanical properties. We use polyethylene oxide (PEO) as a carrier material to aid in electrospinning, and relate the solution properties, including entanglement concentration, relaxation time, conductivity, and surface tension, to their ability to be electrospun. In addition, we examine an FDA-approved, nonionic surfactant as a route to enhancing the alginate–PEO ratio (>80:20), and less toxic alternative to Triton X-100 surfactant. Finally, alginate-only nanofibers that are also water-insoluble are obtained by crosslinking the electrospun fibers with calcium and subse- quently removing the PEO and surfactants by soaking the nanofibers in water. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction Electrospun nanofibers are promising materials for biomedical applications, such as drug delivery, wound dressings, and tissue scaffolds. Nanofibrous mats have high surface areas and tunable morphologies, which can influence cell proliferation and behavior (Chew, Wen, Dzenis, & Leong, 2006). Additionally, the abundance of polymers and polymer blends that can be electrospun provide researchers many options for tailoring the mechanical and bio- logical properties for their desired application. Several synthetic polymers, such as poly(-caprolactone), polylactide, and polygly- colide, have been electrospun for use as tissue scaffolds (Liang, Hsiao, & Chu, 2007). However, one drawback of fibers made from these polymers is the use of cytotoxic organic solvents during fab- rication, which would require thorough washing and/or solvent evaporation treatments on the mats prior to use with cells. Nat- ural, water-soluble polymers are an attractive alternative, as they are readily soluble in aqueous media because of their hydrophilic nature, and have low immunogenicity (Lee, Jeong, Kang, Lee, & Park, 2009). ∗ Corresponding author. Tel.: +1 919 515 4519; fax: +1 919 515 3465. E-mail address: khan@eos.ncsu.edu (S.A. Khan). Sodium alginate is a water-soluble, biocompatible polysac- charide that is used in drug delivery (Augst, Kong, & Mooney, 2006), wound dressings (Hashimoto, Suzuki, Tanihara, Kakimaru, & Suzuki, 2004), and tissue engineering (Alsberg, Anderson, Albeiruti, Rowley, & Mooney, 2002). Ionically crosslinked alginate gels are biodegradable, a property which can be tuned by changing the com- position and MW of the polymer chains. Alginate is composed of blocks of -d-mannuronic acid (M) and -l-guluronic acid (G). Only the G blocks in alginate can be crosslinked with divalent cations (e.g., Ca 2+ )(Smidsrod & Skjakbraek, 1990). When used in vivo, ion- ically crosslinked alginate degrades when the calcium ions are exchanged with other ions in the body, such as Na + (Shoichet, Li, White, & Winn, 1996). As such, the variation in the M to G ratio, based on the alginate source, can provide one avenue to control the degradation. However, compared to the composition of algi- nate, modification of the polymer MW is a more exploitable route to controlling in vivo degradation. Alginate chains can be shortened to lower MWs by exposure to gamma-irradiation. Low radiation doses (<8 Mrad) create chain scissions of the glycosidic bonds between the M and the G blocks, with minimal effects on the block content and length (Alsberg et al., 2003). When used as tissue scaffolds, ioni- cally crosslinked low MW alginate (<50 kDa) degrades more quickly than higher MW. Shorter degradation times may be more optimal for some tissue regeneration applications that want to match tissue formation with polymer degradation rate (Alsberg et al., 2003). One 0144-8617/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbpol.2011.02.002