Ivis lumina xr imager

Fluorescence images were acquired immediately after labelling on live islets in the medium placed in 0.5 mL test tubes using an IVIS Lumina XR imager (Perkin Elmer, Waltham, MA, USA) with the following parameters: exposure time 2 s, aperture four, excitation at 745 nm, emission filter at 810–875 nm. Regions of interest (ROI) of the same size were drawn over each sample. The optical signal from the ROI (average radiance) was expressed in arbritrary units normalized to the signal of islets labelled by endocytosis. Data were compared to the signal of PIs after endocytosis, which was performed with each microporation experiment (and was considered as a standard). Data could not be directly compared between different experiments due to possible variations in geometry setting. A standard photograph in the visible part of the light spectrum was acquired for co-registration of the optical signal.

Optical images were acquired on an IVIS Lumina XR imager (PerkinElmer, USA) with an exposure time of 1 min, an open aperture and an open emission filter. A photographic image was acquired for anatomical co-registration of the signal. Luciferase expression of each set of cells was confirmed using BLI. Isolated MSCs (0.6 × 10⁵ − 1 × 10⁶) were placed into a six-well plate and imaged for 1 min after the addition of 10 μl of d-luciferin (30 mg/ml). The MSC recipients were examined before and after intravenous administration of d-luciferin dissolved in sterile PBS (at a dose of 15 mg) in a time series lasting 14 min. The bioluminescent colour-coded images were superimposed on the photographic images and analysed using the Living Image software package (PerkinElmer, USA). Signal intensity was assessed as photons per second per square centimetre per steradian (p/s/cm²/sr) from the area containing the scaffold. The area under the curve (AUC) was calculated from each time course in order to minimise the variability in d-luciferin administration among the measurements. The bioluminescence examination was performed at the same time points as the MRI experiments; one animal was monitored for 16 months.