(a) Au[(Gly-Tyr-Met)2B], (b) Au[(Gly-Tyr-TrCys)2B], (c) Au[(Gly-Trp-Met)2B], (d) Au[(Met)2B] and (e) Au[(TrCys)2B], in water and EMEM/-, each at a concentration of 100 μg/ml and at time point 0 and 2, 4 and 24 h of incubation at 37°C. Zeta potential To study changes in AuNP stability,
on the basis of electrostatic interaction, zeta potential measurements were performed. Due to the high salt content of EMEM/S+ and EMEM/S- media, measurements were performed only in HMPL-504 ic50 Milli-Q water. Measurements were taken just after preparation of AuNP suspensions (100 μg/ml), at initial time (T0) and 24 h after incubation under assay conditions. The five AuNP preparations used in this study, namely Au[(Gly-Trp-Met)2B], Au[(Gly-Tyr-TrCys)2B], Au[(Gly-Tyr-Met)2B], Au[(Met)2B] and Au[(TrCys)2B], showed zeta potentials of −31.6 ± 2.02, −37 ± 1.04, −36 ± 1.12, −39 ± 1.07 and −43.3 ± 1.13 mV, respectively (Table 2). All zeta potentials
were negative BYL719 and remained negative over time. Table 2 Physico-chemical properties of PBH-capped AuNPs (100 μg/ml) under different conditions over time Milli-Q water EMEM/S+ EMEM/S- T0 T24 MM-102 price T0 T0 T24 T0 T24 AuNP Size a Size Zeta b Size Size Size Size nm nm mV nm nm nm nm Au[(Gly-Trp-Met)2B] 148 ± 2 148 ± 1 −31.6 ± 2.0 242 ± 4 243 ± 6 233 ± 15 1,239 ± 26 Au[(Gly-Tyr-TrCys) 2 B] 143 ± 1 143 ± 1 −37 ± 1.4 261 ± 1 261 ± 2 251 ± 15 195 ± 2 Au[(Gly-Tyr-Met)2B] 591 ± 73 507 ± 65 −36 ± 1.1 987 ± 205 987 ± 207 407 ± 21 1,230 ± 8 161 ± 5 150 ± 12 203 ± 13 201 ± 9 Au[(Met)2B] 229 ± 23 228 ± 10 −39 ± 1.1 190 ± 13 190 ± 4 1568 ± 28 1,368 ± 25 38 ± 6 40 ± 3 27 ± 9 28 ± 3 Au[(TrCys)2B] 205 ± 1 205 ± 1 −43.2 ± 1.1 261 ± 3 260 ± 4 271 ± 23 908 ± 23 97 ± 3 T0 represents measurements directly after preparation and T24 measurements 24 h after incubation under cell exposure conditions (37°C, 5% CO2). Average values of three independent measurements are presented (mean ± SD). Bold emphasis is used to signal the most stable AuNP; DLS, dynamic light scattering. aHydrodynamic
size (Size); bzeta potential (Zeta) of AuNPs in Milli-Q water. DLS was used to measure the hydrodynamic diameters of NPs in Milli-Q water and in medium suspension (100 μg/ml). DLS measurements were taken just after suspension (T0) and after 24 h incubations (T24) under assay conditions. In water, all AuNP preparations formed agglomerates, Thiamet G showing characteristic maximum intensity hydrodynamic diameters of ≤200 nm (Table 2). The Au[(Gly-Tyr-Met)2B] also appeared as larger agglomerates, with a maximum intensity diameter of 591 nm at time 0, while Au[(Met)2B] presented an additional NP population of only 38 nm in diameter. Using the size distribution of the AuNPs in water as a reference, we observed an increase in hydrodynamic size for all the AuNP preparations when incubated in EMEM/S+ and EMEM/S-, but to different extents.