DNA condensation for gene therapy as monitored by atomic force microscopy

Area of Science:

• Biophysics
• Molecular Biology
• Biochemistry

Background:

• DNA condensation is crucial for gene delivery systems.
• Polylysine (PL) is a common agent for DNA condensation.
• Glycoproteins like asialoorosomucoid (AsOR) can be used to target gene delivery.

Purpose of the Study:

• To investigate DNA condensation using polylysine (PL) and PL attached to glycoproteins.
• To determine the optimal conditions for DNA condensation with PL-glycoprotein complexes.
• To evaluate the effect of these complexes on gene expression.

Main Methods:

• Atomic Force Microscopy (AFM) was employed to measure DNA condensation.
• Various molecular weights of PL and glycoproteins (AsOR, OR) were used.
• Lysine:nucleotide (Lys:nt) ratios were systematically varied.
• Gene expression enhancement was assessed in mouse liver models.

Main Results:

• 10 kDa PL covalently attached to AsOR at Lys:nt ratios of 5:1 or higher yielded optimal DNA condensation, forming toroids and short rods (300-400 nm).
• Partial DNA condensation was observed with 10 kDa PL-AsOR at lower ratios (1.6:1, 3:1) and with 4 kDa PL at higher ratios (≥3:1).
• PL alone or PL attached to orosomucoid (OR) showed minimal DNA condensation.
• AsOR-PL complexes enhanced mouse liver gene expression 10- to 50-fold compared to PL alone.

Conclusions:

• Covalent attachment of PL to AsOR significantly improves DNA condensation efficiency compared to PL alone or PL-OR.
• The 10 kDa PL-AsOR complex at high Lys:nt ratios is a promising candidate for effective gene delivery vehicles.
• AsOR-PL complexes demonstrate superior gene delivery capabilities, evidenced by substantial gene expression enhancement in vivo.