(277g) Electrospun Silk with Selenium Nanoparticles for Antibacterial Skin Applications

Stanley Chung¹, Thomas J. Webster^1-3
1. Department of Chemical Engineering, Northeastern University, Boston, MA
2. Department of Bioengineering, Northeastern University, Boston, MA
3. Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia 

Skin infections have accelerated in the past decade, often caused by Staphylococcus aureus, the leading cause of skin and soft tissue infections (SSTI). In addition, strains of S. aureus are developing resistance to most conventional antibiotic treatment options. Antibiotic resistance is a growing epidemic and is estimated by the Centers for Disease Control and Prevention to cost $20 billion annually in excess health costs and $35 billion in other societal costs. Thus, it is evident that new strategies are needed to combat this growing public health threat.

Selenium is a novel chemistry in biomedical applications and has shown beneficial properties for reducing bacterial infections. In particular, selenium nanoparticles have shown good antibacterial properties that selectively inhibit bacteria while maintaining mammalian cell growth.¹ In addition, the selenium nanoparticle coating process developed in this lab is facile and versatile, allowing researchers to deposit selenium nanoparticles as an antibacterial additive to a variety of biomaterials.^2,3 

Silk has been shown to possess many beneficial properties for skin regeneration by promoting collagen synthesis, re-epithelialization, wound healing, atopic dermatitis alleviation, and scar reduction. In particular, electrospun silk possesses morphology similar to that of native extracellular matrix in the body and is especially suitable for skin tissue engineering applications. Unfortunately, silk has also been shown to promote bacterial growth. Here, it is proposed that the combination of two biomaterials, selenium nanoparticles and silk, as a nanocomposite scaffold will promote healthy skin cell growth while reducing the bacterial load.

Silk fibroin was extracted from Bombyx mori silk worms and resuspended in formic acid at a concentration of 8% (w/v) for electrospinning. After electrospinning the silk scaffolds, selenium nanoparticles were deposited onto the silk scaffolds. In vitro skin cell viability and activity were then assessed by MTS assay (Promega) with passage 3-12 human dermal fibroblasts while S. aureus activity was assessed by an ATP assay (Promega). In all experiments, the control group comprised of cells seeded onto polystyrene tissue culture flasks. All experiments were conducted in at least triplicates and N=3.

Recent results on the cellular activity associated with electrospun nanocomposite scaffolds will be presented. Briefly, results show a statistically significant reduction in metabolic activity of S. aureuswhile promoting the metabolic activity of human dermal fibroblasts; for both the MTS and the ATP assay, addition of selenium nanoparticles further enhanced the response of the cells as compared to the control (p<0.05 for silk samples without nanoparticles and p<0.01 for silk samples with nanoparticles as compared to the control). Further studies involving microscopy and qPCR will elucidate the mechanism of action by which this bactericidal activity is achieved.

Acknowledgement:

We acknowledge the funding provided by Northeastern University.

References:

1. Tran, P. A. & Webster, T. J. Selenium nanoparticles inhibit Staphylococcus aureus growth. Int. J. Nanomedicine 6,1553 (2011).

2. Wang, Q., Larese-Casanova, P. & Webster, T. J. Inhibition of various gram-positive and gram-negative bacteria growth on selenium nanoparticle coated paper towels. Int. J. Nanomedicine 10,2885 (2015).

3. Wang, Q., Mejía Jaramillo, A., Pavon, J. J. & Webster, T. J. Red selenium nanoparticles and gray selenium nanorods as antibacterial coatings for PEEK medical devices. J. Biomed. Mater. Res. Part B Appl. Biomater. (2015).