Electrospun cellulose acetate fiber mats containing asiaticoside or Centella asiatica crude extract and the release characteristics of asiaticoside Orawan Suwantong a , Uracha Ruktanonchai b , Pitt Supaphol a, * a Technological Center for Electrospun Fibers and The Petroleum and Petrochemical College, Chulalongkorn University, Pathumwan, Bangkok, Thailand b National Nanotechnology Center, Thailand Science Park, Klong Luang, Phathumthani, Thailand article info Article history: Received 24 February 2008 Received in revised form 12 July 2008 Accepted 14 July 2008 Available online 19 July 2008 Keywords: Topical/transdermal drug delivery Wound dressing Electrospinning abstract Ultra-fine cellulose acetate (CA; M w z 30,000 Da; degree of acetyl substitution z 2.4) fiber mats con- taining asiaticoside (AC) from the plant Centella asiatica L. either in the form of pure substance (PAC) or a crude extract (CACE) were fabricated by electrospinning. Incorporation of either PAC or CACE (40 wt.% based on the weight of CA) in the neat CA solution (17% w/v in 2:1 v/v acetone/dimethylacetamide) did not affect the morphology of the obtained fibers, as both the neat and the herb-loaded CA fibers were smooth. The average diameters of these fibers ranged between 301 and 545 nm. Determination of the release characteristics of AC from the herb-loaded CA fiber mats was carried out by the total immersion and the transdermal diffusion through a pigskin method in acetate or phosphate buffer solution that contained methanol (hereafter, A/B/M or P/B/M medium) at either 32 or 37  C, respectively. In the total immersion method, the maximum amounts of the AC released from the PAC- and the CACE-loaded CA fiber mats into the A/B/M medium were w24 and w10% (based on the weight of the specimens), while those of the AC released into the P/B/M medium were w26 and w12%, respectively. Considerably lower values were, however, obtained when the materials were placed on top of a piece of pigskin. Lastly, the herb-loaded CA fiber mats released no substance that was harmful to normal human dermal fibroblasts, rending their potential for use as topical/transdermal or wound dressing patches. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Electrospinning (e-spinning) is a process by which ultra-fine fibers with diameters in the micrometer down to nanometer range can be fabricated. This process involves the application of a strong electric field across a conductive capillary attaching to a polymer liquid-containing reservoir and a collector [1,2]. When the electric field exceeds a critical value where the Coulombic repulsion of the accumulated charges overcomes the surface tension of the polymer droplet at the tip of the capillary, a charged jet is ejected. During its flight to the collector, the charged jet thins down and, simulta- neously, dries out or solidifies, leaving ultra-fine fibers on the collector [3]. Ultra-fine fibers obtained from this process exhibit various interesting characteristics (e.g., high surface area to mass or volume ratio, high density of micro- or nanometer-sized pores of the non-woven mat, and vast possibilities for surface functionali- zation). These unique properties render electrospun (e-spun) fibers as excellent candidates for various biomedical applications, e.g., scaffolding materials for cell/tissue culture [4–6], wound-dressing materials [7,8], and carriers for topical/transdermal delivery of drugs [9–13]. Cellulose acetate (CA) is the acetate ester of cellulose, the primary structural component of cell walls of green plants and is one of the most common biopolymers on earth [14]. Ultra-fine CA fiber mats and regenerated cellulose membrane have been prepared by e-spinning. The most suitable solvent system for producing e-spun CA fibers was 2:1 v/v acetone/dimethylacet- amide (DMAc) mixture, which allowed the resulting CA solutions (i.e., 12.5–20 wt.%) to be e-spun into fibers with average diameters ranging between w100 nm and w1 mm [15]. In another report [16], a mixed solvent of acetone/water with the water content in the range of 10–15 wt.% was used to produce the e-spun CA fibers with average diameters being w2 mm. In yet another report [17], 3:1:1 v/ v/v acetone/dimethylformamide (DMF)/trifluoroethylene (TFE) was used to prepare a CA solution that resulted in the e-spun fibers with diameters ranging from w200 nm to w1 mm. Among various applications, e-spun CA fiber mats have been developed as carriers for topical/transdermal delivery of drugs [11–13]. Taepaiboon et al. [11] developed e-spun CA fiber mats as carriers for topical/transdermal delivery of all-trans retinoic acid or vitamin A acid (Retin-A) and a-tocopheral or vitamin E (Vit-E) from CA solutions in 2:1 v/v acetone/DMAc containing Retin-A and Vit-E in the amount of 0.5 and 5 wt.% (based on the weight of CA), respectively. E-spun CA fiber mats as carriers for topical/trans- dermal delivery of four different non-steroidal anti-inflammatory * Corresponding author. Fax: þ66 2215 4459. E-mail address: pitt.s@chula.ac.th (P. Supaphol). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2008.07.020 Polymer 49 (2008) 4239–4247