(a) General scheme of preparation of MBMs using the LbL method: co-precipitation of SNARF-1-D (purple) into porous CaCO₃ cores (yellow); LbL assembly of microcapsule shell around the cores (only three layers of negatively charged polymer, three layers of positively charged polymer and final biocompatible layer are depicted); and dissolution of cores. (b) SEM image of porous CaCO₃ cores with incorporated SNARF-1-D. (c) Prepared MBMs under confocal laser scanning microscope LSM 700. (d) Examples of fluorescence spectra of microencapsulated SNARF-1-D with varying pH. (e) Calibration curve of MBMs containing SNARF-1-D with varying pH was built based on median values (emphasized by larger dark blue points); original values are also depicted (smaller light blue points).

Visualization of MBMs and pH measurements in zebrafish embryos.

(a) Images of MBMs in the intestine of a zebrafish embryo, combined green (587 nm) and red (627 nm) channels. (b) Images of MBMs in brain ventricle of a zebrafish embryo, combined green (587 nm) and red (627 nm) channels. (c) pH in cerebrospinal fluid monitored by MBMs under control and heat shock conditions with respective original images of MBMs in the brain ventricle of the same individual. Blue indicates control conditions; orange indicates heat shock exposure. * indicates a statistically significant difference from the control with p-value < 0.05.

General scheme of optical system in confocal laser scanning microscope LSM 700 used for in vivo pH measurements with implanted MBMs.