## 1 Introduction  
Organ failure due to infection, injury or disease is a major health care issue that places enormous burden on the national economy. Restoration of structure and function of these tissues is essential for maintenance of quality of life. Current strategies include transplantation of grafts, mechanical devices and artificial prostheses. However, neither of these options result in satisfactory long-term outcomes. Tissue engineering is a promising strategy that attempts to create functional tissues by implanting synthetic or natural biomaterials that eventually are replaced by host tissue [1]. Strategies promoting tissue regeneration include cell-based approaches (involving transplantation of autologous/allogeneic cells [2; 3; 4], use of biological molecules including growth factors, DNAand polysaccharides [5; 6; 7; 8], as well as scaffold-based tissue engineering approaches [9; 10; 11; 12; 13]. Currently, complex 3D tissue constructs are being engineered by culturing specific cell types in microenvironments that mimic the biochemical and mechanical aspects of natural extracellular matrix. Foremost among the list of requirements of implanted tissue engineered scaffold is its cytocompatibility. Beyond this basic requirement, the scaffolds need to be conducive to cell attachment, migration, proliferation, differentiation and maintenance of cell phenotype [14; 15; 16; 17]. Synthetic resorbable polyesters are a popular choice in scaffold fabrication because they offer control over mechanical properties, degradation rates and micro/nano architecture [18; 19]. Polycaprolactone (PCL) is relatively inexpensive aliphatic polyester with good solubility and exceptional blend-compatibility that lends itself to a variety of fabrication methods. Electrospinning is a versatile scaffold fabrication technique that consistently reproduces the submicron diameter fibers from polymer solutions. In addition to rendering the morphology similar to native ECM (extracellular matrix) the process is readily scalable; allows control over fiber diameter [20; 21], porosity [22; 23; 24] and alignment [25; 26]. While most in vitro and in vivo studies using electrospun PCL have used ethanol disinfection prior to cell culture or implantation in animals, clearly this is inadequate for clinical translation for tissue-engineered product. Our previous study found that conventional methods of sterilization (autoclave, EtO) of low melting electrospun PCL scaffolds resulted in loss of fibrous architecture whereas peracetic acid (PA) at 1000 ppm preserved scaffold morphology [27]. PA is available as an equilibrium mixture of acetic acid and hydrogen peroxide and has been extensively used in the food industry because of its high potency and low residual toxicity. PA is effective at low concentrations, low temperatures and degrades into nontoxic end products (water, oxygen and carbon dioxide) and can be safely disposed of without affecting the environment. PA is among the list of Food and Drug Administration (FDA)-cleared sterilants cleared by the FDA for the processing of reusable medical and dental devices [28]. Unlike physical methods of sterilization (radiation and heat), an inherent issue using a chemical sterilant (liquid or gas) is the adsorbed residuals that need to be completely eliminated. Ethylene oxide (EtO), an effective chemical sterilant, is known for its adsorption onto polymeric surfaces and leave residuals that are both cytotoxic and carcinogenic. Extensive aeration (up to 12 h) at 50-60 \({}^{\circ}\)C is necessary to completely remove all EtO residues [29] and is a part of standard operating procedures. Having introduced PA previously, we focused on evaluating its adsorption potential and cytotoxic effects on electrospun PCL (ePCL) scaffolds. To the best of our knowledge, this is the first study to evaluate the biological effects of PA sterilization on ePCL scaffolds and compare it against a commercially available polystyrene scaffold (Alvetex(tm)).