Lactonic Sophorolipid Increases Surface Wettability of Poly-l-lactic Acid Electrospun Fibers

Abstract

The hydrophobicity of electrospun poly-Llactic acid (PLLA) fibers hinders their integration with surrounding tissue for a variety of applications. In this study, we increased PLLA fiber hydrophilicity by incorporating the natural surfactant, lactonic sophorolipid (LSL). PLLA+LSL fibers had similar fiber morphology but significantly greater surface wettability, which suggested LSL accumulation on the fiber surface. Differential scanning calorimetry results also suggested that LSL was phase separated from PLLA. Despite the altered surface wettability of these fibers, there was no change in fibroblast adhesion. Future studies may explore the use of this natural surfactant to deliver bioactive factors to enhance fibroblast adhesion.

A class of surfactants via PEG modification of the oleate moiety of lactonic sophorolipids: synthesis, characterisation and application

“…Our NMR spectroscopy assignment agrees with the prior literature on the structure of LSL. 30 Some impurities were observed on the proton and 13 C NMR spectra for LSL despite the claim by manufacturer to have a purity of 99%, however, we were unsuccessful in determining the structure of the impurity. It is further observed in mass spectrometry below and assumed to have a molecular ion mass of 467 g/mol.…”

“…While the proton peak "10" to which the PEG is attached was conspicuous resonating at 3.22 ppm, the proton peak 9 that bears the hydroxyl end overlapped with the protons of the surfactant sophorose group. 13 C and DEPT-135 spectra did not show the corresponding positions of these peaks ("9" and "10") but HSQC (Figure S4) correlated the 3.22 ppm proton with the 83.75 ppm carbon. Since the position of attack cannot be controlled, attack of PEG on the oxirane ring from both faces (above or below) is possible as shown in the supplementary information Figure S11, though NMR spectroscopy could not significantly differentiate them but it is assumed it is a 50:50 mix of both present in the product.…”

“…In order to remove traces of residual Adogen 464 (carried over from the epoxidation reaction) the product was purified by re-dissolution in ethyl acetate and passed through a narrow column packed with Amberlyst 15 ion exchange resin, followed by removal of the solvent in vacuo. Product identification was by IR spectroscopy, ESI mass spectrometry, CHN elemental analysis and 1 H and 13 C NMR spectroscopy, analysis and mass recovered summarised below for each surfactant.…”

“…12 SL surfactants have attracted commercial and academic interests for their applications in detergency, surface enhancement of electro spun fibre, bioremediation, enhanced oil recovery, medicine, home and personal care products and antimicrobial agents either as a single entity or in combination with rhamnolipids. [13][14][15][16][17][18] They are readily biodegradable, less toxic and have low cytotoxicity compared to other conventional non-ionic surfactants such as Triton-X100, pluronic L31 and polyoxyethylene lauryl ether. 19,20 Production yields for SLs can be up to 400 g L -1 depending on the strain of yeast used.…”

“…The reaction mixture was cooled and extracted with 250 mL ethyl acetate, the organic layer collected, dried over anhydrous magnesium sulphate, filtered and the solvent removed in vacuo to yield a fluffy hydroscopic product (7.49 g total product recovered, 99.2% yield). The product 10 was ground into powder and analysed by IR spectroscopy, ESI-MS, CHN elemental analysis and 1 H and proton-decoupled13 C NMR spectroscopy.…”