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Modulation of calcium phosphate formation by phosphatidate-containing anionic liposomes
E D Eanes1, A W Hailer, B R Heywood
1National Institute of Dental Research, Bethesda, MD 20892.
Calcified Tissue International
|October 1, 1988
Summary
Dioleoylphosphatidic acid (DOPA) in liposomes inhibited calcium phosphate formation. Even low DOPA concentrations significantly reduced or completely suppressed precipitation, suggesting a role in controlling biomineralization.
Area of Science:
- Biochemistry
- Materials Science
- Biomineralization
Background:
- Liposomes are versatile lipid vesicles used in drug delivery and biomimetic studies.
- Understanding factors influencing biomineralization is crucial for various applications, including bone regeneration and preventing pathological calcification.
Purpose of the Study:
- To investigate the effect of membrane-bound monoester phosphatidate anions, specifically dioleoylphosphatidic acid (DOPA), on calcium phosphate formation.
- To determine the inhibitory concentration of DOPA in liposomal membranes on mineral precipitation.
Main Methods:
- Liposomes were prepared with varying molar percentages of DOPA.
- Calcium phosphate precipitation was induced in metastable solutions using liposomes as potential nucleation sites.
- Transmission electron microscopy (TEM) was used to analyze the interaction between liposomes and mineral crystals.
Main Results:
- DOPA incorporation into liposomes did not initiate mineralization in metastable solutions.
- As little as 1 mole % DOPA measurably reduced precipitation, and 5 mole % completely suppressed it.
- DOPA-containing liposomes inhibited mineralization more effectively than other diester phosphate lipids like phosphatidylglycerol and phosphatidylinositol.
Conclusions:
- DOPA-containing lipid bilayers effectively inhibit extraliposomal calcium phosphate formation.
- Inhibition is likely due to the encapsulation of seed crystals within liposomes or blocking crystal growth sites.
- The unique charge and steric properties of DOPA's polar head group facilitate adherence to crystal surfaces, driving the inhibitory effect.