**2.1 Characterization of nanoparticles**

Commercial SiO2 size 0.007µ (S-3051), ZnO/6% Al doped <50nm(677450), and Al2O3 <50nm (544833) were purchased from Sigma Aldrich. As comparison, single walled Carbon Nanotubes (CNO, 704121) from Sigma Aldrich was used. Nanoparticles, characterized by manufacturer, were dispersed in Milli-Q water and/or PBS (137 mM NaCl, 2.7 mM KCl, 8.45 mM Na2HPO4, 1.47 mM KH2PO4 pH 7.3) and sonicated on ice for 10 min. The hydrodynamic sizes of the particles were analyzed by Dynamic Light Scattering (DLS).

DLS measurements were performed using an ALV/DLS/SLS-5022F system (ALV-GmbH, Langen Germany) and a HeNe laser at 632.8 nm with 22 mW output power. The scattering angle was 90 and the temperature 22C. For temperature stabilizing purposes, samples were placed in a thermostat bath (22C) for at least 10 minutes prior to the measurements. Samples were diluted in Milli-Q water or PBS. Ultrasonication of two different kinds was performed to decrease the degree of agglomeration; either an ultrasonic bar homogeniser (Sonoplus HD 2200, Bandelin electronics, Germany) was used or samples were placed in an ultrasonic bath (USC300T, VWR, Sweden). The viscosity of PBS was set to 0.9782 mPa's by linear interpolation between tabulated values for 20C (0.911) and 25 C (1.023) (Hackley & Clogston, 2007).

Data analysis was performed using a nonlinear fit model via ALV-Regularized Fit (ALV-Correlator Software Version 3.0. using ALV-Regularized in nonlinear fit model http://www.alvgmbh.de/).
