Temperature Dependent Gene Expression Induced by PNIPAM-Based Copolymers:  Potential of Hyperthermia in Gene Transfer

Abstract

The objective of this work was to obtain gene delivery vectors with high efficiency induced by application of local hyperthermia. As a building construct for the polyplex particles, block copolymers were used, in which one block represents poly(ethyleneimine) (PEI) and another block a statistical copolymer of poly(N-isopropylacryamide) (PNIPAM) and different hydrophilic monomers (acrylamide or vinylpyrrolidinone). The block copolymers were synthesizized by radical polymerization of the corresponding monomers directly onto PEI. The complexation of DNA with these copolymers led to small, charge neutral particles, which aggregated upon increasing the temperature from 37 degrees C to 42 degrees C. This aggregation was found to be responsible for the enhanced transfection efficiency of these formulations under hyperthermic conditions. Gene expression in cells treated by hyperthermia was found to be nearly 2 orders of magnitude higher in comparison to cells transfected at physiological temperature. The mechanism by which hyperthermia influences the gene transfection efficiency is proposed.

Temperature-Tunable Iron Oxide Nanoparticles for Remote-Controlled Drug Release

“…The final precipitate of nanoparticles was washed with 0.1 M tetramethylammonium hydroxide pentahydrate (TMAOH) solution and dispersed in 150 mL of 0.1 M TMAOH solution, resulting in the final iron oxide solution to be used for further modifications. The synthesis of the copolymer was carried out at rt following the previously published procedure by Zintchenko et al (15) through radical copolymerization of NIPAM with AAm in water using APS as initiator in the presence of branched PEI. For synthesis of the copolymer with the NIPAM to AAm ratio of 3:1, 1.02 g (9.02 mmol) of NIPAM and 0.213 g (3.01 mmol) of AAm were dissolved in 10 mL of Milli-Q water; 0.50 g (~0.02 mmol) of PEI was dissolved in 5 mL of Milli-Q water and added to the resulting solution of NIPAM and AAm.…”

“…Thus, Richard et al (14) have studied the tunability of LCST of poly (2-oxazoline)s by varying its composition and molecular weight. Moreover, Zintchenko et al (15) succeeded in the tuning of LCST in the range of 37°C-42°C of temperature-responsive polymers by using the copolymer polyethylenemine (PEI) as a cationic block and statistical copolymer of PNIPAM with the use of acrylamide (AAm) or vinylpyrrolidinone (VP) as a hydrophilic monomer.…”

Balancing protection and release of DNA: tools to address a bottleneck of non-viral gene delivery

“…When cooled below its LCST, PNIPAm reverts to the solution state to release the DNA (Hinrichs et al 1999;Kurisawa et al 2000). PNIPAm has also been grafted with proven gene carriers such as PEI and chitosan to impart responsive properties and improve transfection (Oupicky et al 2003;Sun et al 2005;Bisht et al 2006;Zintchenko et al 2006;Lavigne et al 2007).…”

Chemically Programmed Polymers for Targeted DNA and siRNA Transfection

“…The block copolymeric carrier consists of one PEI block conjugated to a block of statistical copolymer pNIPAM and different hydrophilic acrylamide or vinylpyrrolidone monomers synthesized by radical copolymerization. Depending on the amount of the hydrophilic moieties, the LCST can be adjusted between 37 and 42 C. These molecules were shown to aggregate under hyperthermic conditions, i.e., heating from 37 to 42 C, in this way enhancing the DNA transfection efficiency [144]. Griffiths et al quantified the temperature dependent conformational changes and the interaction between pNIPAM-graft-PEI copolymers by using small-angle neutron scattering (SANS) and pulse-gradient spin-echo NMR (PGSE-NMR).…”