Polaron e5000 sputter coater

SEM assessed the morphological changes of bacteria after ZnO-NP treatment. Briefly, 1 mL of KPC suspension (10⁸ CFU/mL) was used for mixing with 1 mL of ZnO-NPs to reach a final concentration of 0.5 mg/L, followed by cultivation overnight at 37 °C. Two controls (negative control with only KPC with medium and positive control with KPC treated with the antibiotic impenem) were prepared in salt-free lysogeny broth medium alone. After the incubation, the samples were washed with normal saline by centrifugation at 1500× g and then fixed with 2.5% glutaraldehyde at 4 °C for 2 h, followed by washing with phosphate buffer (pH = 7.2). The samples were post-fixed in 1% osmium tetroxide, followed by dehydration through an ascending ethanol series, critical point drying, and coating with Au–Pd (80:20) using a Polaron E5000 sputter coater, Quorum Technologies, Laughton, UK. The samples were checked at an accelerating voltage of 25 kV in FEI Quanta 250 using an SE detector [17 (link),18 (link)].

Scanning electron microscopy (SEM) (Philips XL30 field emission SEM, Amsterdam, The Netherlands) was used to evaluate the printing resolution and the scaffold morphology. Before the analysis, the samples were coated with 95% gold and 5% palladium (Polaron E5000 Sputter Coater, Quorum Technologies, Laughton, UK). The printing resolution was observed by measuring the layer thickness. The printing resolution was set to 0.1 mm.

To characterise the internal microstructures of the GelMA hydrogels, the crosslinked hydrogel samples were frozen at −80 °C and then lyophilised. The dried samples were frozen at −20 °C and cross-sectioned, then coated with 95% gold and 5% palladium by Polaron E5000 Sputter Coater (Quorum Technologies, Lewes, UK), and images were taken by using a Philips XL30 field emission SEM (Amsterdam, The Netherlands). ImageJ software was used to measure pore size based on scanning electron microscopy (SEM) images.

The morphological structure of the composites was viewed under SEM (Zeiss EVO HD, Jena, Germany). Triplicates of each sample group were cut into ~5 mm squares, mounted on stubs, and coated with 95% gold and 5% palladium (Polaron E5000 Sputter Coater, Quorum Technologies, Laughton, UK). The images of each sample were viewed at the central position of magnifications 500× and 5000×; the fibre diameter was measured and captured using the Zeiss EVO HD in-built software (i.e. Zen 2.5, version 1).

The surface morphology of the modified ESM samples was studied using a SEM instrument (Zeiss EVO HD, Jena, Germany) operated with an accelerating voltage of 10 kV and working distance (WD) of 8.3 ± 1 mm. The 14 mm circular modified samples were fixed on conductive carbon tapes and coated with 95% gold and 5% palladium using Polaron E5000 Sputter Coater (Quorum Technologies, Laughton, UK). Images of the samples at magnification of 5000× were taken to visualize the samples (modified protocol adapted from Dubey et al. [27 (link)]).

The AgNP morphology was assessed by means of an SEM instrument (Zeiss EVO HD with eBruker EBSD, Jena, Germany) operated with an accelerating voltage of 10 kV and working distance (WD) of 8.3 ± 1 mm. The 14 mm circular modified samples were fixed on conductive carbon tapes and coated with 95% gold and 5% palladium using a Polaron E5000 Sputter Coater (Quorum Technologies, Laughton, UK). Images of the samples at magnifications of 100k, 30k, and 5k× were taken to visualise the samples. The AgNP average size was calculated using ImageJ software (https://imagej.net/ij/download.html, 23 March 2024). At least 50 nanoparticles were selected from different acquired images.