Adsorption and removal dynamics of polymeric micellar nanocarriers loaded with a therapeutic agent on silica surfaces†
Obtaining a better understanding of the adsorption behavior of polymeric nanomedicines is important to properly assess their distribution and fate and to develop successful strategies for minimizing their distribution in the environment. In this study, the adsorption and removal dynamics of a model polymeric nanomedicine of systematically varied sizes – levofloxacin loaded poly(ethyleneglycol-b-ε-caprolactone) – on and from silica surfaces are investigated using a quartz crystal microbalance with dissipation (QCM-D). For all the sizes of the nanomedicine investigated (90 nm, 110 nm, 149 nm, 174 nm, 207 nm, and 305 nm), the adsorbate mass on the silica followed a roughly exponential trend with respect to time during the exposure stage, suggesting first-order adsorption kinetics. The adsorption rate constant decreased with the increasing particle size. Furthermore, we have developed a modified Leveque equation to describe the mass transport and adsorption behavior of the nanoparticulate dispersion inside the QCM-D chamber. The derivation involved the application of a bipolar coordinate system to the continuity, Navier–Stokes, and convective–diffusion equations. The adsorption rate constants calculated using the derived equation were found to match the experimental results well. The derived equation is important not only in the field of environmental science but also in many other fields as QCM-D is heavily used to characterize the dynamic adsorption behavior of various types of materials including polymers, proteins, and nanoparticles.