Teriparatide loaded liposomes were produced by pre-forming hydrophobic peptidesurfactant ion pairs and then incorporating these into the lipidic thin-film to produce liposomes. A range of liposomes with different phospholipid composition was prepared and characterised for peptide loading, size distribution, and transition temperature. All further experiments were conducted at the highest HIP loading (1.4 mg of HIPs per 10 mg of phospholipids). The liposomes were comprised of DPPC (Tc = 41°C) and DSPC (Tc = 54°C) mixtures, ranging from a DPPC:DSPC molar ratio of 8:2 to pure DSPC (0:10) liposomes, thereby increasing the transition temperature . Table presents an overview of the different liposomal formulations and their physico-chemical properties. The two phospholipids (DSPC and DPPC) differ in the number of carbons in their fatty acid chain. Indeed, the increased carbon chain length of DSPC increases the transition temperature to 52 °C (pure DSPC), from 41 °C (pure DPPC) . Liposomes composed of different phospholipids combine into one phase with a single phase transition . Therefore, by preparing composite DPPC:DSPC liposomes the transition temperature of the resulting formulation may be tailored within the range of 41 -52 °C. Four different liposomal formulations were prepared with increasing DSPC content ranging from DPPC:DSPC ratios of 8:2 to pure DSPC. As expected, an increase in onset and peak transition temperature is observed with increasing DSPC content (Table ). Further, the incorporation of HIP into the liposomes resulted in a slight reduction of the transition temperature. Empty DSPC-2 liposomes presented a transition temperature onset of 40.9 ± 0.4 °C, whereas when incorporating HIPs a slight reduction in transition temperature was observed. A slight reduction of transition temperature upon incorporation of drug into the lipid bilayer has been well described in the literature, thus suggesting that the HIPs are located in the lipid bilayer of the liposomes . The desired transition temperature of the system is 43 -45 °C, slightly above physiological temperature. This will avoid premature release, while keeping the required temperature increase minimal, thus ensuring tolerability and avoiding tissue damage. Apart from the DSPC-2 formulation, all formulations present transition temperatures above physiological temperatures (37 -40 °C) while also accounting for disease (e.g. fever) and within or slightly above the target range of 43 -45 °C.