Investigating the selectivity of the targeting properties of trastuzumab-bound nanoparticles to HER2/neu positive cells in co-culture

Active targeting of tumor tissue represents an urgent goal in modern therapy. Ligand-modified nanocarriers serve as promising vehicles in the selective delivery of non-selective drugs to the tissue of interest. As such, it is not only important to ensure that the active targeting design of such nanocarriers causes an enhanced uptake by the designated target cells, but also to know to what extent it is more selective in the presence of non-target cells. The purpose of this study was to investigate the selectivity properties of human serum albumin based nanoparticles with trastuzumab covalently bound to the surface by a bifunctional polyethylene glycol linker. HER2/neu positive cells were cultivated in co-culture with non-target cells. Cell and nanoparticle interaction was analyzed by flow cytometry. Analytical difficulties in fluorescence detection when working with cross-linked albumin were identified and overcome. The selectivity of the designed targeting formulation was expressed as factor between fluorescence intensity of target cells to the fluorescence intensity of non-target cells after nanoparticle incubation. The target selectivity for these nanoparticle formulations was proven in co-culture setting, with selectivity factors of up to 100. Selectivity was found to be majorly time- and concentration-dependent, and most importantly in requirement of a minimum concentration. The importance of covalent linkage of the specific antibody to the nanoparticle surface and the usage of a polyethyleneglycol linker was once again highlighted in various control experiments.