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Evaluation of Antibacterial Effects of Polyurethane-Cinnamomum zeylanicum Nanofiber Scaffolds against Clinical Isolates of Staphylococcus aureus

Background and Objectives: In recent years, infections caused by antibioticresistant strains of Staphylococcus aureus have become a major health issue. It has been suggested that the extract or essential oil of cinnamon tree has antibacterial properties. In this study, we investigated the antibacterial effects of polyurethane-cinnamon nanofibers against clinical isolates of S. aureus. Methods: Polyurethane-Cinnamomum zeylanicum nanofiber scaffolds were synthesized. Polyurethane nanofiber and cinnamon polymers were also used to prepare the scaffold under the electrospinning process. Infrared spectroscopy, electron microscopy and mechanical tensile test were utilized to assess the scaffolds. Minimum inhibitory concentration of the nanofiber against the bacteria was determined using the broth dilution method according to the Clinical & Laboratory Standards Institute guidelines. Results: The results of antibiogram test showed that all tested disks were susceptible to S. aureus. Diameter of growth inhibition zone for polyurethane-cinnamon 10% was 41 mm. Minimum inhibitory concentration of the nanofiber against S. aureus isolates was 0.02

electron microscope (SEM) was used to assess the morphology and topography of the scaffold. Twenty clinical isolates of S. aureus were obtained from the Baqiyatallah hospital in Tehran, Iran. Susceptibility of the isolates to the polyurethane-Cinnamomum zeylanicum nanofiber was assessed using the Kirby-Bauer test. S. aureus isolates were identified using catalase, coagulase, mannitol salt agar, production of deoxyribonuclease enzyme and bacitracin tests and sensitivity to novobiocin. After isolating the bacteria, a number of colonies was taken using a sterile loop and dissolved in sterile physiological serum. Turbidity was adjusted at 0.  (5).

RESULTS
In the Kirby-Bauer test, all strains were sensitive to the polyurethane-Cinnamomum zeylanicum nanofiber. Young's results show that by adding a polyurethane-darchine to a scaffold during electronics, it causes a slight decrease in tension and also a reduction in the Young's modulus ( Table 1). The diameter of growth inhibition around the disks was 41 mm ( Table 2) and MIC of the nanofiber was 0.02 µg/mL against S. aureus isolates. Mechanical tensile test was carried out to examine the mechanical properties (tensile strength) of the scaffold. The elasticity of the scaffold of polyurethane nanofiber alone and in combination with the cinnamon essential oil was 3.94% and 0.096%, respectively, indicating a linear deformation of the scaffold (Figure 1).

INTRODUCTION
Staphylococcus aureus is a normal flora of the nose, skin and digestive tract of some people. The bacterium causes various infections ranging from simple skin infections to life-threatening diseases, such as pneumonia, meningitis, endocarditis, toxic shock syndrome and septicemia. It is also one of the main causes of nosocomial infections, especially post-surgical ulcers. It is estimated that 500,000 people in American hospitals become infected with S. aureus every year (1). Various factors including hemolysines, surface antigens, exotoxins, exogenous enzymes, siderophore and staphylogensin are involved in virulence of this bacterium (2). Panton-Valentine leukocidin is an important virulence factor in almost all methicillin-resistant S. aureus strains, which plays a role in the spread of cutaneous infections by eliminating leukocytes (3). Currently, over 90% of S. aureus strains are resistant to penicillin, and resistance of these strains to semi-synthetic penicillins (methicillin, Nafcillin and oxacillin) is also increasing. Other antibiotics used for treatment of S. aureus infections include penicillin-like drugs such as carbapenems, sulbactam, cephalosporins and amoxicillin-clavulanic acid.
Medicinal herbs have various advantages over the chemical drugs namely less side effects, fewer risk of environmental pollution and widespread availability (4). Many studies have investigated the antibacterial activity of medicinal plants against various bacteria. In this study, we evaluated the inhibitory properties of polyurethane-Cinnamomum zeylanicum nanofiber scaffolds against S. aureus using the Kirby-Bauer test.

MATERIALS AND METHODS
Design and construction of nanoscaffolds consisted of two steps: solution preparation and setting up of an electrical apparatus.
Fourier-transform infrared spectroscopy was used to evaluate the scaffold's structure. Tensile testing was done to examine the tensile strength and scanning

CONCLUSION
Given the favorable results obtained in our study, the electrolytic polyurethanecinnamon nanofiber can be suggested as a potential antibacterial agent for the treatment of infections caused by S. aureus.