Interaction of insulin with anionic phospholipid (DPPG) vesicles

Area of Science:

• Biochemistry and Biophysics
• Materials Science
• Pharmacology

Background:

• Protein-lipid interactions are vital for drug efficacy.
• Biocompatible liposomes, such as 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) vesicles, are used for drug delivery.
• Understanding insulin's interaction with lipids is crucial for developing effective insulin formulations.

Purpose of the Study:

• To investigate the interaction between insulin and DPPG lipid anionic vesicles.
• To confirm insulin entrapment within DPPG liposomes.
• To elucidate the molecular mechanisms underlying insulin-lipid complex formation.

Main Methods:

• Steady-state emission spectroscopy at room temperature (300 K).
• Temperature-dependent and time-resolved spectroscopy.
• Molecular dynamics simulations.
• Dynamic light scattering (DLS) and zeta potential measurements.

Main Results:

• A novel broad peak between 400-500 nm, attributed to tyrosine phosphorescence, was observed in the insulin-DPPG complex.
• This phosphorescence serves as a signature for insulin entrapment within the liposomes.
• Molecular dynamics revealed increased tyrosine rigidity within the lipid layer, supported by DLS and zeta potential data confirming insulin attachment to anionic DPPG liposomes.

Conclusions:

• Insulin can be successfully entrapped into DPPG liposomes.
• Tyrosine phosphorescence is a reliable indicator of insulin-liposome interaction.
• The study provides molecular insights into insulin-lipid complexation, relevant for drug delivery systems.