Supporting Information

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1 Supporting Information Wiley-VCH Weinheim, Germany Physicochemical Properties of Protein-Coated Gold Nanoparticles in Biological Fluids and Cells before and after Proteolytic Digestion** Munish Chanana,* Pilar Rivera_Gil, Miguel A. Correa-Duarte, Luis M. Liz-Marzµn, and Wolfgang J. Parak* anie_ _sm_miscellaneous_information.pdf

2 Supplementary Information A B C Figure S1: Transmission electron microscopy (TEM) images of A) Au@BSA, B) Au@Insulin and C) Au@b-LG NPs. The NPs were dispersed in H 2 O at ph 7.4 and purified before TEM characterization. The scale bar corresponds to 100 nm. Figure S2: NP concentration dependent cell viability of 3T3 mouse embryonic fibroblasts for various protein coated NPs performed after 24 hours incubation via a metabolic assay. The values are an average over 3x2 independent tests and were normalized to the values recorded for the control experiments (no NPs). The solid lines are exponential fits to the respective data. Although there are significant error bars, the main parameter of these curves, the point of inflection, the so called EC50 value can be clearly extracted. The slope of the curve at the point of the curve at the point of inflection is much steeper than the error bar per concentration interval, and thus the point of inflection is well determined. The concentrations of Au@BSA, Au@β-LG and Au@insulin corresponding to the EC50 value are 2.98 µm, 1.81 µm and 0.07 µm, respectively. Figure S3: A droplet of a highly concentrated Au@BSA NP dispersion (2 µm, i.e. 2µmol NPs/L), exhibiting a gold shimmer when looked from a certain angle. The NP drop is sitting next to a water droplet (left panel), which were then mixed (right panel), showing the recovery of the red color of the gold NPs. Please note the golden shimmer also on the edge of the merged drops (right panel).

3 Figure S4: Time-dependent fluorescence release of in 3T3-fibroblasts. 3T3-fibroblasts were treated with TRITC labeled NPs (c = 25 nm) and confocal laser scanning microscopy (CLSM) images were recorded at the same position after an incubation time of 30 minutes (A, left panel) and 4 hours (B, right panel). The images are an overlay of the fluorescence (red, false colors) and transmission channel. The images below show the marked regions (ROI) at higher magnification (only the fluorescence channel, scale bar 37 µm). The dotted distribution of the internalized NPs, indicating vesicular compartments, is typical for endocytosis.

4 Figure S5: Time-dependent fluorescence release of in 3T3-fibroblasts. Depicted are confocal laser scanning microscope images of 3T3 embryonic mouse fibroblasts incubated with NPs. The left image shows an overlay of the fluorescence (green, false colors) and transmission channel. The images on the right panel show the marked regions at 2x higher (right up) and 3x higher (right down) magnification (only the fluorescence channel). Also here, the dotted patterns are clearly visible, which indicate endocytotic vesicles, suggesting NP uptake over an endocytotic pathway. Figure S6: UV-Vis spectra of NPs at different salt concentrations after an incubation time of 3 days. The NP concentration decreases in the dispersions, since a fraction of NPs phase separates from the solution and climbs the glass walls of the vial, which can be clearly seen from the red shimmer on the glass wall and the lighter color of the right-hand side dispersions in Figure 5a (see main article). A possible explanation for this observation is the charge screening induced by the salt. The hydrophobic protein-protein interactions between the protein-coated NPs increase, [1] making them slightly hydrophobic and interface active, thereby leading to phase separation and adsorption of a small fraction of the NPs at the airwater interface. This effect is known as salting-out of proteins and can vary from protein to protein, but usually occurs at high salt concentrations in the case of pure proteins. [2] The LSPR absorption maximum at 525 nm does not reveal any spectral shift, indicating no agglomeration of the NPs in the dispersions.

5 Experimental Section Chemicals: HAuCl 4*3H 2O ( 99.9%), sodium citrate dihydrate (> 99%), human insulin recombinant (91077C), bovine serum albumin (BSA), β- Lactoglobulin (β-lg), ovalbumin from chicken egg white and tetramethylrhodamine isothiocyanate (TRITC) were purchased from Sigma Aldrich. DQ-Ovalbumin (Ova-DQ) was purchased from Invitrogen. All chemicals were used as received. Milli-Q grade water was used in all preparations. Synthesis of Au@Protein NPs: Citrate coated gold NPs (Au@citrate) with an average particle size of ~ 15 nm were synthesized by the Turkevich method. [3] The NPs were then coated with proteins by a simple ligand exchange process as previously reported. [4] For this, a proteincitrate solution was first prepared, by dissolving 10 mg of a protein in 10 ml of 0.1 % citrate solution. The ph of the solution was adjusted to 7-8 with NaOH. Subsequently, the protein-citrate solution was added dropwise to 90 ml of citrate coated gold NPs ([Au] = 0.5 mm) under vigorous stirring. The mixture was stirred for 24 hours at room temperature. Finally, the protein coated gold NPs (Au@protein) were purified via 5-fold centrifugation (10000g, 30 min), concentrated ([Au 0 ] ~ mm) and stored at ph 9 at 4 C. Synthesis of Au@Protein-F NPs: Fluorescent labelled Au@Protein NPs were synthesized using two different methods, namely route a, where a pre-labelled protein such as the Ova-DQ was directly employed to coat the Au@citrate NPs and route b, where the pre-synthesized Au@Protein NPs, such as Au@BSA or Au@Insulin were labelled with TRITC. In particular, for the synthesis of Au@Ova-DQ, protein-citrate solution was first prepared, by dissolving 1 mg of Ova-DQ and 9 mg of ovalbumin in 10 ml of 0.1 % citrate solution. The ph of the solution was adjusted to 7-8 with NaOH. Subsequently, the protein-citrate solution was added dropwise to 90 ml of citrate coated gold NPs ([Au 0 ] = 0.5 mm) under vigorous stirring and the reaction mixture was stirred for 24 hours. For the synthesis of Au@BSA-TRITC for instance, 10 mg of TRITC were first dissolved in 300 µl of DMF and then added to 10 ml of a sodium carbonate buffered ([Na 2CO 3] = 0.1M) and concentrated dispersion of Au@BSA NPs ([Au 0 ] = 12 mm). The mixture was stirred for 24 h at room temperature. All Au@Protein-F NPs were purified via centrifugation (10000 g, 30 min) and the centrifugation steps were repeated until no fluorescence was measured in the discarded supernatants. Sterilization of Au@Protein NPs: Prior to any biological experiments, all Au@Protein NPs dispersions were sterilized via filtration through 0.22 µm steril syringe filters (cellulose acetate filters). First, the ph of the dispersions was adjusted to ph 8-9 and filtered under steril conditions (flow bench, autoclaved equipment and vials). Then the vials were sealed under the flow bench and the dispersions were centrifuged for minutes at rcf (8000 rpm). The supernatant was replaced by steril (autoclaved) water, the dispersions were vigorously vortexed and centrifuged again. (For fluorescence labeled NPs, this process was repeated until no fluorescence in the supernatant was measured). The pellet was dispersed in a very small amount of steril water, giving NP concentrations in µm range. This final NP dispersion was then diluted in DMEM culture media to the desired concentrations according to the experimental requirements. Determination of Au NP Concentrations: The concentration of Au NPs was determined via UV-Vis spectrometry, using the Lambert-Beer law (E(λ) = ε(λ)*l*c) taking the extinction values E(λ) at λ = 525 nm i.e. at the LSPR maximum and the extinction coefficient ε(λ) = 4*10 8 M -1 cm -1 for gold NPs with an average diameter of 15 nm, according to report published by Qun Huo et al. [5] A concentration of 1µM Au NPs (number of NPs/volume) correspond to a concentration of ca. 100 mm elemental gold (Au 0 ) Cell Viability Test: For cell viability tests, 3T3 embryonic fibroblasts were seeded with a density of 1.5x10 4 cells/well in 96-well-plates with a final volume of 100 µl growth medium (DMEM or DMEM-F 12Ham s, respectively supplemented with10% FBS, 1% L-glutamine, and 1% penicillin/streptomycin) and incubated for 24 hours in an incubator (37 C, 5% CO 2). Subsequently, various Au@Protein(-F) NPs at different concentrations were given to the cells. For this, highly concentrated NP dispersions in growth medium (usually with [NP]> 2 µm) were applied and simply diluted to reach lower concentrations. In control experiments the medium was replaced by fresh medium, without addition of NPs. After the incubation time of 24 hours with NPs, the cells were washed with PBS and a solution out of 10% Resazurin solution + 90% growth medium was added to the each well (total 100 µl/well). After incubation time of 3 hours with Resazurin, fluorescence spectra of the solutions was measured, using spectrofluorometer from Jovin Yvon with a 96-well plate reader, by exciting the solutions at 560 nm and recording the emitted fluorescence in the range nm. The fluorescence values were corrected by subtracting the background measured between nm, averaged over the number of measurements per sample (3x2) and normalized with the values obtained for control measurements. Plotting the normalized fluorescence values vs. log of concentrations gives the dose response curve (sigmoidal curve), from which the EC50 (LD50) value can be obtained. Confocal Laser Microscopy Measurements: For confocal microscopy experiments, 3T3 cells were treated with fluorescent labeled NPs (Au@Ova-DQ or Au@BSA-R NPs). Cells in the absence of NPs (control) were also imaged to control the effect of light on the cells over the time lapses. Immediatelly after addition of the NPs, the same cell position was imaged over time with a confocal laser microscope (LSM 510 META from Zeiss) attached to an incubator that provides an atmosphere of 37 C and 5% CO 2. Cells were observed with a 63x immersion oil objective (N.A. 1.4) at 0, 1, 2, 4 and 8 h. After 1 h, the cell medium was changed to remove the extracellular NPs. All optical parameters that could influence the fluorescence signal (i.e. exposure time, laser irradiation, pinhole, etc.) were maintained constant during the whole experiment. Further Characterization Techniques: All NP dispersions were characterized by means of the following characterization techniques: Transmission electron microscopy (TEM) was carried out with a JEOL JEM 1010 transmission electron microscope operating at an acceleration voltage of 100 kv. For this, purified and diluted dispersions of all types Au NPs were simply casted on TEM grids (ca µl) and dried under ambient conditions. UV-vis-NIR spectra were measured with a Cary 5000 UV-Vis-NIR spectrophotometer. ζ-potential values were determined through electrophoretic mobility measurements using a Malvern Zetasizer Nano ZS Zen3600 by taking the average of five measurements, each consisting of 70 runs. Dynamic light scattering (DLS) measurements were also performed on a Malvern Zetasizer Nano ZS, by taking the average of 5 measurements of each 15 runs. ph measurements were performed with Crison Micro ph-2000 ph-meter. The photographs were recorded with a Sony DSC-W350 digital camera. [1] W. Melander, C. Horváth, Archives of Biochemistry and Biophysics 1977, 183, 200. [2] T. Arakawa, S. N. Timasheff, Biochemistry 1984, 23, [3] J. Turkevich, P. C. Stevenson, J. Hillier, Discussions of the Faraday Society 1951, 55. [4] a)m. S. Strozyk, M. Chanana, I. Pastoriza-Santos, J. Pérez-Juste, L. M. Liz-Marzán, Advanced Functional Materials 2012, 22, 1436; b)m. Chanana, M. A. Correa-Duarte, L. M. Liz-Marzán, Small 2011, 7, [5] X. Liu, M. Atwater, J. Wang, Q. Huo, Colloids and Surfaces B: Biointerfaces 2007, 58, 3.