Scanning electron microscopy
Three inserts were, after treatment according to the instillation
protocol described above, fixed using glutaraldehyde 2.5% (EM Grade
1.06 Polysciences). This was followed by incubation with increasing
concentrations of ethanol. After incubation in 100% ethanol, critical
point drying (CPD) was performed. The dry inserts where then sputtered
with gold particles as final preparation for scanning electron
microscopy. The same protocol was followed as Janssen et al. [9]