Histidine‐Functionalized Diblock Copolymer Nanoparticles Exhibit Enhanced Adsorption onto Planar Stainless Steel

RAFT aqueous emulsion polymerization of isopropylideneglycerol monomethacrylate (IPGMA) is used to prepare a series of PGEO5MA46‐PIPGMAy nanoparticles, where PGEO5MA is a hydrophilic methacrylic steric stabilizer block bearing pendent cis‐diol groups. TEM studies confirm a spherical morphology while dynamic light scattering (DLS) analysis indicated that the z‐average particle diameter can be adjusted by varying the target degree of polymerization for the core‐forming PIPGMA block. Periodate oxidation is used to convert the cis‐diol groups on PGEO5MA46‐PIPGMA500 and PGEO5MA46‐PIPGMA1000 nanoparticles into the analogous aldehyde‐functionalized nanoparticles, which are then reacted with histidine via reductive amination. In each case, the extent of functionalization is more than 99% as determined by 1H NMR spectroscopy. Aqueous electrophoresis studies indicate that such derivatization converts initially neutral nanoparticles into zwitterionic nanoparticles with an isoelectric point at pH 7. DLS studies confirm that such histidine‐derivatized nanoparticles remain colloidally stable over a wide pH range. A quartz crystal microbalance is employed at 25°C to assess the adsorption of both the cis‐diol‐ and histidine‐functionalized nanoparticles onto planar stainless steel at pH 6. The histidine‐bearing nanoparticles adsorb much more strongly than their cis‐diol counterparts. For the highest adsorbed amount of 70.5 mg m–2, SEM indicates a fractional surface coverage of 0.23 for the adsorbed nanoparticles. The authors examine the adsorption of a series of sterically‐stabilized diblock copolymer nanoparticles onto a model stainless steel substrate using a quartz crystal microbalance. The adsorbed amount depends on both the mean diameter and the surface functionality of the nanoparticles. Introducing histidine groups via periodate oxidation and reductive amination leads to twice the adsorbed amount compared to cis‐diol groups.