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  • The use of isothermal titration calorimetry and molecular dynamics to show variability in DNA transfection performance.

The use of isothermal titration calorimetry and molecular dynamics to show variability in DNA transfection performance.

Acta biomaterialia (2012-10-13)
Olga Samsonova, Serghei Glinca, Adam Biela, Christian Pfeiffer, Eyas Dayyoub, Damla Sahin, Gerhard Klebe, Thomas Kissel
ABSTRACT

The mechanism causing variability in DNA transfection efficacy for low-molecular-weight pDMAEMA (poly(2-(dimethylamino)ethyl methacrylate) and pDMAEMA-b-pHEMA (poly(2-(dimethyl amino)ethylmethacrylate)-block-poly(2-hydroxyl methacrylate)) has so far remained unclear, apart from the evidence of beneficial effects of the pHEMA grafting. This study has explicitly characterized the electrostatically driven self-assembly process of linear polymethacrylate polymers with DNA-generating nanocarriers for efficient gene transfection. Isothermal titration calorimetry (ITC) showed clear differences in binding-heat profiles of homo-polycationic and pHEMA grafted polymers with DNA. Polyethylene imine, a branched polycationic polymer of 25kDa with high transfection potential that has previously been successfully used in transfection experiments, demonstrated a heat flow profile that was partly identical to pDMAEMA-b-pHEMA. Computational molecular dynamics (MD) simulated the folding process of polymer in water from a linear to a coiled state: homo-pDMAEMA and pHEMA grafts reduced their overall positive charge accessibility upon folding, down to 45% and 63%, respectively. The homo-pDMAEMA formed the globular conformation more preferably than pHEMA grafts, thus impeding electrostatic interaction with DNA. These findings substantiate the known disadvantage of low-molecular-weight linear polymers compared to higher-molecular-weight polymers in transfection performance; here we have disclosed the ability of a non-cationic chain elongation to be beneficial for the self-assembly process. The combination of MD and ITC has proved to be a suitable approach for carrier-payload interaction studies and may be used to predict the efficacy of a polymer as a nanocarrier from the flexibility of its structure.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Poly(2-hydroxyethyl methacrylate), BioReagent, powder, suitable for cell culture
Sigma-Aldrich
Poly(2-hydroxyethyl methacrylate), average Mv 1,000,000
Sigma-Aldrich
Poly(2-hydroxyethyl methacrylate), average Mv 20,000
Sigma-Aldrich
Poly(2-hydroxyethyl methacrylate), average Mv 300,000, crystalline