Chemical Conjugation of Cowpea Mosaic Viruses with Reactive HPMA-Based Polymers

Abstract

N-(2-Hydroxypropyl)methacrylamide (HPMA) co-polymers containing disulfide and carbonyl thiazolidine-2-thione (TT) reactive groups in their side-chains (pHPMA-TT) were used as reductively removable chemical modification of the surface of cowpea mosaic viruses (CPMV). CPMV was used in this study as a model particle for viral gene delivery. The co-polymer reaction with CPMV surfaces carried out in aqueous solution was evaluated by monitoring the changes in the weight-average molecular weight and hydrodynamic size of the viruses using light scattering methods. The reaction conditions were optimized. The surface modification of CPMV with pHPMA-TT under selected conditions (concentrations of a coating polymer (c p) and NaCl) has not influenced the size distribution of the viral particles. The uncharged polymers bound to the viral surface via biodegradable S–S bonds can be fully removed by the exchange reaction with reductive dithiothreitol. To achieve optimal covering of viral surfaces, the positively charged reactive polymers (with or without biodegradable S–S bonds) should be applied at low concentrations (c p=0.1–0.5 mg/ml) and in presence of NaCl (0.15 M).