Molecular interactions between DPPC and morphine derivatives: a DSC and EPR study.

Area of Science:

• Pharmacology
• Biophysics
• Materials Science

Background:

• Liposomes, particularly dipalmitoyl phosphatidylcholine (DPPC) liposomes, are crucial drug delivery systems.
• Understanding drug-liposome interactions is vital for optimizing drug efficacy and stability.
• Morphine derivatives are widely used analgesics with varying pharmacokinetic profiles.

Purpose of the Study:

• To investigate the interaction between morphine and its derivatives (codeine, N-methyl-morphine, N-methyl-codeine) and DPPC liposomes.
• To elucidate the impact of these interactions on liposome membrane dynamics.
• To characterize the binding sites of morphine derivatives within the liposome structure.

Main Methods:

• Differential scanning calorimetry (DSC) for thermal analysis of liposome-drug interactions.
• Electron paramagnetic resonance (EPR) spectroscopy to probe molecular mobility within liposomes.
• Dynamic light scattering (DLS) for determining liposome size distribution.
• Spectrophotometry for quantifying entrapped drug concentrations.

Main Results:

• Morphine and its derivatives primarily interact with the polar head groups of DPPC liposomes.
• These interactions lead to a notable decrease in the mobility of the liposome's polar head groups.
• Codeine and N-methyl-codeine exhibited a more pronounced reduction in head group mobility compared to morphine and N-methyl-morphine.

Conclusions:

• Morphine derivatives interact with the lipid head groups of DPPC liposomes, influencing membrane fluidity.
• The observed decrease in head group mobility suggests potential alterations in liposome stability and drug release kinetics.
• Differential effects among derivatives highlight the importance of chemical structure in drug-liposome interactions.