Controllable stability of DNA-containing polyelectrolyte complexes in water-salt solutions

Area of Science:

• Materials Science
• Biochemistry
• Polymer Chemistry

Background:

• Polyelectrolyte complexes (PECs) are formed by interactions between oppositely charged polymers, such as DNA and synthetic polyamines.
• Understanding the stability of these PECs is crucial for their application in areas like drug delivery and gene therapy.
• The dissociation of PECs is influenced by environmental factors like pH and ionic strength.

Purpose of the Study:

• To investigate the dissociation of DNA-polycation complexes (PECs) under varying pH conditions.
• To determine the effect of polycation structure, specifically the type of amine groups, on PEC stability.
• To provide a basis for designing DNA-containing PECs with controllable stability for potential therapeutic applications.

Main Methods:

• Formation of PECs using DNA and various synthetic polyamines with different amine group structures.
• Dissociation studies conducted by adding low molecular weight electrolytes to PEC solutions at different pH values.
• Fluorescence quenching technique utilizing ethidium bromide to monitor DNA intercalation and PEC dissociation.

Main Results:

• Polycations with quaternary amine groups (e.g., poly(N-alkyl-4-vinylpyridinium) bromides) formed pH-independent PECs that were least stable to salt addition.
• Polycations with primary amine groups (e.g., poly-L-lysine hydrobromide, poly-L-arginine hydrochloride) formed the most stable PECs across a wide pH range.
• PECs with tertiary amine groups (e.g., poly(N,N-dimethylaminoethylmethacrylate)) or mixed amine groups (e.g., branched poly(ethylenimine)) exhibited moderate and pH-dependent stability.
• Quaternization of tertiary amine groups decreased PEC stability, as expected.
• A random copolymer of 4-vinylpyridine and N-ethyl-4-vinylpyridinium bromide formed pH-sensitive PECs, dissociating under conditions close to physiological.

Conclusions:

• The structure of amine groups in polycations is a critical determinant of DNA-polycation complex stability.
• Tailoring polycation composition, including the type and proportion of amine groups, allows for control over PEC stability.
• The pH-sensitive dissociation of certain PECs, particularly those formed by copolymers, holds promise for targeted DNA delivery to cells under physiological conditions.