Characterization of self-assembled hybrid siloxane-phosphocholine bilayers

Exploring the utility of hybrid siloxane-phosphocholine (SiPC) liposomes as drug delivery vehicles

“…Hybrid SiPCs Cap-ValDS-PC 1, Cpc-ValDS-PC 2, Lau-ValDS-PC 3, Myr-ValDS-PC 4, Pal-ValDS-PC 6, and Ste-ValDS-PC 7 were synthesized as previously described. 34 The general procedures for the synthesis of lyso-PCs and hybrid SiPCs are included below. More detailed syntheses and complete spectroscopic characterization can be found in the ESI.…”

“…32 Furthermore, we have shown that these hybrid SiPCs also self-assemble into ULVs. 34 The sizes of vesicles formed from hybrid SiPCs were analyzed by DLS and the results are summarized in Table 3. Hybrid SiPCs were found to self-assemble into vesicles of $100 nm in diameter, with the exception of Cpc-ValDSPC (2), which was determined to be 168 nm in diameter and Lau-ValDSPC (3), which had a diameter of 364 nm.…”

“…It was not until 2017 that siloxane moieties were rst graed onto lipid structures with the express purpose of modifying the lipids' interfacial behaviour. [32][33][34] Siloxane-phospholipids (SiPCs) possessing identical lipid tail structures to biologically relevant lipid species self-assemble in aqueous media to form low dispersity, unilamellar vesicles (ULVs) that are on average 120 nm in diameter, unlike natural phosphocholines such as 1,2dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoylsn-3-glycerophosphocholine (DOPC), or 1-palmitoyl-2-oleoyl-snglycero-3-phosphocholine (POPC), which typically form larger (>200 nm) multilamellar liposomes. Hybrid SiPCs, possessing a siloxane fatty acid tail in the sn-2 position and an aliphatic fatty acid tail in the sn-1 position, self-assembled into ULVs or multilamellar vesicles (MLVs) depending on the chain length of the sn-1 fatty acid.…”

“…34 When palmitic acid (C 16 ), or stearic acid (C 18 ) were incorporated at the sn-1 position, SAXS analysis revealed the presence of MLVs as well as ULVs. 34 Liposomes derived from hybrid SiPCs generally do not exhibit any detectable thermotropic phase transitions between 5 C and 60 C. The exception to this was the SiPC, which had stearic acid in the sn-1 position and displayed a phase transition temperature at 17 C. The absence of phase transitions suggests that SiPC liposomes are comparable to liposomes composed of phosphocholines (PCs) such as POPC, DOPC with unsaturated fatty acids, or the archaebacterial PC 1,2-diphytanoyl-sn-glycero-3phosphocholine (DPhyPC). [35][36][37][38] The suitability of articial liposomes for drug delivery purposes is largely dependent on the specic release kinetics of the bilayer.…”

“…1 SiPCs and their capacities to spontaneously form ULVs or MLVs. 32,34 In this study, we examined the release of calcein from liposomes composed of hybrid siloxane-phosphocholines to ascertain the suitability of siloxane-phosphocholines as components in drug delivery systems; POPC, DPPC, and DPhPC were included as commercially available comparators. The release of calcein was carried out at pH 4.5, 7.5 and 10.5 to mimic the different physiological environments within the human body.…”