## 3 Results
If they were birefringent, one would see higher order interference colors (such as orange and blue). Confocal fluorescence microscopy was used to demonstrate the internal entrapment of model active agent compounds within the core-shell particles. Capsules synthesized with rhodamine 110 and/or Nile Red fluorescent dye encapsulated in the interior were washed and subsequently examined. Figure 7 shows the entrapment of Nile Red fluorescent dye within the oil-interior of the emulsion-derived microcapsules. The liposome-derived core-shell microcapsules display the ability to entrap both hydrophobic (Nile Red dye) and hydrophilic (rhodamine 110) compounds, as is shown in Figure 8A,B, respectively, as well as in the overlay of both images shown in Figure 8C  
Due to concerns that the CaCO\({}_{3}\) shells would degrade too slowly given that calcite has a rather low solubility and is notorious for clogging up industrial pipelines, etc., a preliminary study of the degradation potential of these particles was performed, the results of which are shown in Figure 9. The emulsion-derived microcapsules degrade readily in a pH-dependent manner, enabling a triggered release of active agent. The microcapsules exposed to the acidic (pH 4) environment for 15 \(s\) experienced severe degradation of the CaCO\({}_{3}\) shell in the form of large gaping holes. The microcapsules exposed to pure water (pH = 6.8) for 2 min experienced degradation as well, but the dissolution of the mineral was unevenly distributed around the microcapsule, and seemed to preferentially etch the \"grain boundaries\" of what appears to be remnants of the coalesced precursor particles. A remnant colloidal texture has been observed in PILP formed films before (as well as in biominerals) [42; 45]. The overall amount of shell degradation appears to be similar for both conditions, but it is important to note that the microcapsules exposed to neutral pH required 8 times the exposure time, and that the degradation in pH 4 conditions appears to be a uniform thinning, whereas at pH 6.8 it exhibited a more asymmetric degradation. Figure 6: X-ray diffraction (XRD) analysis of the CaCO\({}_{3}\) shells of liposome-derived microcapsules. The XRD pattern display peaks characteristic of calcite. The theta values are slightly larger than expected for pure calcite due to magnesium ion incorporation (which is smaller than calcium ion, and thus reduces the lattice dimensions). The mineral coating does not contain significant amounts of vaterite or aragonite, as evidenced by the absence of peaks at their characteristic high intensity locations of 20 = 25.0\({}^{\circ}\) and 45.9\({}^{\circ}\), respectively. Figure 7: Confocal fluorescence microscopy of microcapsules from CaCO\({}_{3}\)-coated emulsion droplets with Nile-Red fluorescent dye entrapped within the oily interior of the emulsion. Confocal fluorescence images are shown to the left (**A**,**C**), while the right images (**B**,**D**) show an overlay with the bright-field images. The high intensity of the fluorescence suggests that the entrapment of the active agent was very successful, as seen in both a large collection of particles in (**A**), as well as in individual microcapsules shown at higher magnification in (**C**). The fluorescence corresponds to the interior of the microcapsules for the cluster (**B**) and the individual microcapsules (**D**) when overlapped with their respective bright-field images. Figure 8: Confocal fluorescence microscopy demonstrating the entrapment capability of the CaCO\({}_{3}\)-coated liposomes. Rhodamine 110 and Nile Red dyes were used as model hydrophilic and hydrophobic entrapment agents, respectively. (**A**) Rhodamine 110 is a hydrophilic fluorescent dye that would be expected to reside in the water interior of the microcapsule. The bright ring around the particles suggests that some of the dye may also bind to the charged headgroup of the liposome or be incorporated into the shell during the PILP process.