The shape parameter of liposomes and DNA-lipid complexes determined by viscometry utilizing small sample volumes

Area of Science:

• Materials Science
• Biophysics
• Analytical Chemistry

Background:

• Accurate characterization of macromolecular shapes is crucial for understanding their behavior.
• Traditional viscometry methods often require large sample volumes, limiting their application.
• Quantifying the deviation of complex structures from perfect spheres is challenging.

Purpose of the Study:

• To introduce a novel minicapillary viscometer for precise shape determination.
• To demonstrate the instrument's capability with minimal sample volumes (<0.5 ml).
• To quantitatively assess the shape parameters (a/b ratio) of liposomes and DNA complexes.

Main Methods:

• Development and utilization of a minicapillary viscometer.
• Measurement of sample viscosity at low volume fractions (<0.1%).
• Calculation of the aspect ratio (a/b) for DPPC/DPPG multilamellar liposomes and DNA complexes.

Main Results:

• The calculated aspect ratio (a/b) for DPPC/DPPG liposomes was 1.14 (prolate ellipsoids).
• The aspect ratio for dioleoylpropyltrimethyl ammonium methylsulfate-DNA complexes was 3.7 (prolate) or 4.9 (oblate).
• The method allows quantitative shape deviation expression beyond two significant figures with <0.5 mg DNA.

Conclusions:

• The minicapillary viscometer offers a sensitive method for shape analysis of complex biological materials.
• The technique requires significantly reduced sample volumes and DNA quantities.
• This advancement enables precise quantitative shape characterization of liposomes and DNA complexes.