## 3 Results  
When SLM are tested directly as a liquid dispersion, the DSC curve shows one large conversion peak, mainly related to water evaporation, within which it is difficult to isolate a small lipid melting peak (Figure 1). According to the DSC curve, the TG curve can distinguish two stages of decomposition with mass loss, which correspond mainly to the loss of water and also to the decomposition of the other components of the dosage form (Figure 1). When SLM liquid dispersions are tested after removing water (in dry form), a single endothermic transition stage can be distinguished in the DSC curves (Figure 1 and Figure S1, presented in Supplementary Materials), without mass loss in the TG curves, which corresponds to the melting process of lipid-forming SLM matrices (for example, an endothermic transition in the SLM with Compritol matrix: onset temperature 71.9 \({}^{\circ}\)C, peak 78.5 \({}^{\circ}\)C). Figure 1: DSC and TG curves of SLM dispersions with Compritol: (A) without water evaporation and (B) after water evaporation, but before thermal analysis. Three different therapeutic substances were used in the development studies of solid lipid microspheres: cyclosporine A (CsA), indomethacin (Ind) and spironolactone (SPIR). The melting endotherms of pure drug substances are shown in Figure 2. They confirm the crystalline nature of Ind and SPIR, while the DSC thermograms and thermal behaviors of pure CsA, confirm the amorphous form of the drug substance. In general, the drug-loaded SLM DSC curves do not show particular variability relative to the placebo SLM curves. In the DSC curve of drug-loaded microparticles, only one strong endothermic peak around the melting point of the lipid was found, and the melting peak of the drug substance did not appear. The melting point of the lipid is slightly lower while the intensity of the peak remains almost unchanged. The lack of any endothermic CsA peaks in all tested SLM formulations, as seen in Figure 3, suggests a molecular interaction between the CsA and lipids or other SLM components and a molecular dispersion of the active substance in the lipid. Lipid microspheres (both with active substances and placebo SLM) are characterized primarily by the presence of an endothermic peak in the temperature range close to the melting point of the lipid forming the microsphere matrix (Figures 1-3). In SLM with  
Figure 3: (**a**) DSC and TG curves and (**b**) the zoom of: (A) F5-SLM dispersion with 2% of CsA, (B) F6-SLM dispersion with 5% of CsA, (C) the bulk CsA and (D in figure (**a**) and D in figure (**b**)) the bulk CsA peak converted to a CsA concentration in F6-SLM with 5% of CsA. Figure 2: DSC and TG curves of the tested drug substances: (A) cyclosporine A, (B) spironolactone and (C) indomethacin. Compritol, this is a sharp peak with a high intensity in the temperature range of 75-79 \({}^{\circ}\)C, while in SLM with stearic acid the intensity, shape and temperature range of the peak can be very different, depending on the tested formulation. If the melting peak of stearic acid is not deformed and shifted, it occurs at about 75 \({}^{\circ}\)C.  
Figure 3a shows the peak melting temperature plots of lipids in SLM with CsA obtained from the DSC experiments. All CsA-SLM thermographs show a decrease in the melting point of Compritol from 78.5 \({}^{\circ}\)C in placebo SLM to 76.1 \({}^{\circ}\)C in SLM with 1% of CsA and to 75.8 \({}^{\circ}\)C in SLM with 5% of CsA. The same effect was observed by [PERSON] et al. [15] in research on casts with glyceryl behenate and ibuprofen. This phenomenon was also observed in SLM with Ind (Figure 4a), where the lipid melting point decreased by 1 \({}^{\circ}\)C (from 78.5 to 77.5 \({}^{\circ}\)C) in SLM with 0.2% of Ind and in SLM with stearic acid. Thermal decomposition of the Ind and SLM with Ind takes place in one stage (Figure 4a). The difference between the temperature ranges corresponding to the decomposition of the pure drug and the dosage form results from and is dominated by the properties of the lipid in the SLM.