Sc7640 sputter coater

SEM was used to see if the polymer materials were composed of discrete monodisperse particles, and it was performed using a Philips XL30 electron microscope. The samples were prepared by putting the polymer powder on a carbon tab mounted onto an SEM stub, which was then coated with Platinum for 180 s at 12 mA and 2.2 kV using an Emitech SC7640 sputter coater. The average size of the polymer particles was calculated by taking the area of 100 particles from a SEM image and then taking the average area of the particles exploiting ImageJ software.

Bacteria were grown as above and after washing in PBS fixed in 2.5% (v/v) glutaraldehyde in PBS for 24 hours. Fixative was removed by two washes in PBS. 50 μl of the sample was added to a glass coverslip treated with Poly-L-Lysine for 10 minutes. A secondary fixation was carried out in 1% (w/v) osmium tetroxide for 90 minutes. Samples were washed in deionised water several times followed by subsequent 30 minute washes in 30%, 50%, 70% and 90% (v/v) ethanol. Two final 30 minute washes in 100% analytical grade ethanol were performed. The slides were washed in 3:1 ethanol/hexamethyldisilazane (HMDS) for 30 minutes followed by 1:3 ethanol/HMDS for 30 minutes and finally 100% HMDS for 30 minutes (twice). Excess HDMS was removed and allowed to air dry overnight. Slides were mounted and sputter coated in gold (Emitech SC7640 sputter coater, 90 seconds, 20 mA Au). Bacteria were viewed on a Hitachi S3000H Scanning electron microscope with an accelerating voltage of 10 kV.

The morphology of the electrospun fibres was analysed by Field Emission Gun Scanning Electron Microscopy (FEGSEM, LEO 1530VP, LEO Elektronenmikroskopie GmbH, Oberkochen, Germany). Prior to observation, the fibrous mats were cut into small pieces (0.3 cm × 0.3 cm), stuck on aluminium stubs by carbon adhesive tapes and then coated using a palladium/gold sputter coater for 90 s (Emitech SC7640 Sputter Coater, Polaron, Laughton, United Kingdom) to produce a conductive surface. The average diameter of the fibres was determined by processing the FEGSEM images using ImageJ (Version 1.52c, National Institute of Heath, Bethesda, MD, USA). Up to 60 fibres were analysed for each type of sample.