For the liposomal formulations at low teriparatide content (Figure ), liposomal vesicles may still be present, and the appearance of globular shaped systems as well as small rods of high contrast were found. Similar observations were made with high concentration of PEGylated phospholipids . The appearance of mixed micelles was attributed to an increasing presence of free SDS originating from unentrapped HIPs. The appearance of thread-like micelles as present in Figure is typically observed in the solubilisation of lipid membranes by surfactants, prior to formation of shorter threads with increasing concentrations (Figure ) . The zeta potential of all four liposomal formulations was measured and the decrease from +0.4 mV (empty liposomes) to up to -11.7 ± 2.1 mV (high HIP liposomes) attributed to the presence of SDS, further concurring with the observations. While increasing peptide concentration through addition of larger volumes of HIP dispersion results in a more heterogenous lipid-based formulation presenting not only liposomes but also mixed micelles, all formulations present a thermo-responsive character with comparable transition temperatures. Overall, teriparatide release form the lipid-based formulations was shown to be temperature-dependent thus providing a first proof-of-concept of the suitability of thermo-responsive liposomes for pulsatile delivery. Similarly, Che et al. recently described a biomimetic bone structure coated with polydopamine and loaded with thermo-sensitive (DPPC) liposomes containing calcein and teriparatide for local bone regeneration. The authors demonstrate a pulsatile release of teriparatide over 14 days in an in vitro assay and in vivo bone regeneration. Nevertheless, the teriparatide loading within the thermo sensitive liposomes was not reported and thus it remains unknown if the system would be suitable to produced therapeutically relevant teriparatide levels .