Diacetylenic lipids in the design of stable lipopolymers able to complex and protect plasmid DNA

Calcein release from DPPC liposomes by phospholipase A2 activity: Effect of cholesterol and amphipathic copolymers

In this study, we evaluated the impact of incorporating diblock and triblock amphiphilic copolymers, as well as cholesterol into DPPC liposomes on the release of a model molecule, calcein, mediated by exogenous phospholipase A2 activity. Our findings show that calcein release slows down in the presence of copolymers at low concentration, while at high concentration, the calcein release profile resembles that of the DPPC control. Additionally, calcein release mediated by exogenous PLA2 decreases as the amount of solubilized cholesterol increases, with a maximum between 18 mol% and 20 mol%. At concentrations higher than 24 mol%, no calcein release was observed. Studies conducted on HEK-293 and HeLa cells revealed that DPPC liposomes reduced viability by only 5% and 12%, respectively, after 3 hours of incubation, while DPPC liposome in presence of 33 mol% of Cholesterol reduced viability by approximately 11% and 23%, respectively, during the same incubation period. For formulations containing copolymers at low and high concentrations, cell viability decreased by approximately 20% and 40%, respectively, after 3 hours of incubation. Based on these preliminary results, we can conclude that the presence of amphiphilic copolymers at low concentration can be used in the design of new DPPC liposomes, and together with cholesterol, they can modulate liposome stabilization. The new formulations showed low cytotoxicity in HEK-293 cells, and it was observed that calcein release depended entirely on PLA2 activity and the presence of calcium ions.

Lipopolymers and lipids from lung surfactants in association with N-acetyl-l-cysteine: Characterization and cytotoxicity

In the present work, we obtained polymeric diacetylene liposomes that can associate N-Acetyl-l-Cysteine (NAC), a broad spectrum mucolytic. The reason for studying these formulations is that they could be applied in the future as NAC delivery systems, with a possible dose reduction but maintaining its effect. Liposomes used herein are obtained by a photopolymerization reaction, thus gaining stability and rigidity. Lipids belonging to lung surfactant were added in different ratios to the formulations in order to maximize its possible interaction with the lung tissue. Because of lipopolymer stability, the oral or nasal route could be appropriated. This formulation could efficiently transport NAC to exert its mucolytic activity and help in diseases such as cystic fibrosis, which has abnormal mucus production. Also, this type of treatment could be useful in other types of diseases, interacting with the mucus layer and making the lung tissue more permeable to other therapies. Formulations so obtained presented high levels of polymerization. Also, they present small hollow fibers structures with a high number of polymeric units. These types of arrangements could present advantages in the field of drug delivery, giving the possibility of a controlled release. Lipopolymers with lipids from lung surfactant associated with NAC are promising complexes in order to treat not only respiratory illnesses. The stability of the formulation would allow its inoculation through other routes such as the oral one, helping the reposition of NAC as an antioxidant drug. Finally, these formulations are non-toxic and easy to produce.

Growing a Nucleotide/Lanthanide Coordination Polymer Shell on Liposomes

Coating liposomes with a shell is a useful strategy to increase membrane stability and prevent leakage or fusion. Nucleotide/lanthanide coordination nanoparticles (NPs) are formed by a simple mixing at ambient conditions. Because some lipid headgroups contain lanthanide binding ligands, they may direct the growth of such coordination NPs. Herein, a gadolinium/adenosine monophosphate (Gd³⁺/AMP) shell was formed on liposomes (liposome@Gd³⁺/AMP) using lipids containing phosphoserine (PS) or cholinephosphate (CP) headgroups, while phosphocholine liposomes did not support the shell. Liposome binding Gd³⁺ is confirmed by transmission electron microscopy (TEM). The negatively charged CP and PS liposomes reversed to positive upon Gd³⁺ binding, while other metals such as Ca²⁺ and Zn²⁺ did not reverse the charge. Binding of Gd³⁺ did not leak the PS liposomes. Then, AMP was further added to cross-link Gd³⁺ on the liposome surface. A shell was formed as indicated by TEM, and the content inside the liposome remained for the PS liposomes. While adding Triton X-100 still induced leakage of the encapsulated liposomes, the shell protected the liposomes from leakage induced by ZnO NPs, suggesting a porous structure of the Gd³⁺/AMP shell which allowed penetration of Triton X-100 but not the larger ZnO NPs. This work provides a simple method to coat liposomes, and also offers a fundamental understanding of liposome adsorption of lanthanide ions.