Trastuzumab-modified nanoparticles: optimisation of preparation and uptake in cancer cells.

Nanoparticles consisting of human serum albumin (HSA) represent a promising strategy for targeted drug delivery to tumour cells. The coupling of the antibody trastuzumab to HSA nanoparticles takes advantage of the capability of HER2-positive cells to incorporate substances binding to HER2. In our present study, we developed nanoparticles based on HSA which were covalently modified on their surface with thiolated trastuzumab. A special focus was on the optimisation of the thiolation procedure of the antibody under the aspect of an effective binding to particle surfaces. Different thiolation conditions were evaluated and the degree of antibody dimerisation was determined. We analysed the thiolated antibody by size exclusion chromatography (SEC) and identified the best thiolation procedure for the preparation of trastuzumab-conjugated nanoparticles. Over a storage period of 6 weeks the resulting particles were stable and physico-chemical properties such as size and zetapotential did not show any changes. Biological activity was confirmed under cell culture conditions: antibody-conjugated nanoparticles showed a specific targeting to HER2-overexpressing cells with cellular uptake by receptor-mediated endocytosis. These data provide the basis for the development of stable and biological active carrier systems for directed targeting of tumour cells using trastuzumab-conjugated HSA nanoparticles.