λmax = k d Supplementary Figures

Transcription

1 Supplementary Figures a b HQ CCD Transmission Grating Beam splitting lens Color CCD Objective Sample Dark-field Condenser Raw data Gaussian fit c λmax = k d k = nm/pixel 53 nm 307 pixels d Supplementary Figure S1. Illustrations of single particle spectral measurement. (a) Device diagram of the high-throughput single-particle dark-field spectral microscope. (b) Typical spectral image of PNP probes absorbed on a glass slide surface. The scale bar is 10 µm. Notice that there is some overlap between zero- and first-order images from different particles. However, since the first-order streaks are always on the right side of the corresponding zero-order spots and have about the same peak-to-peak distance, the spectrum of almost every particle is readily derived. (c) By calibrating using a 53 nm laser, 1 pixel is found to correspond to nm. Gaussian fitting to the line graph of the first order image gives the location of the spectral intensity maximum in pixels. The spectral maximum in nm can subsequently be obtained.

2 a c Extinction µm 10 µm 50 µm 100 µm b Frequency (%) d λmax shift (nm) Aspect Ratio 100 µm 50 µm 10 µm Wavelength (nm) Time (min) Supplementary Figure S. Characterization of the prepared 55 7 nm AuNR-Ag nanoprobes with a 3 nm Ag shell optimized for dark-field imaging. (a) TEM image. (b) Aspect ratio distribution. Over 300 particles were counted. (c) Normalized extinction spectra of the PNP solution after adding 0, 10, 50 and 100 µm of Na S. (d) Time courses of Δλ max with the addition of 10, 50 and 100 µm of Na S obtained via UV-Vis measurement.

3 a Frequency (%) d Frequency (%) Cys & NaCl Cys & NaCl & NaS Δλmax (nm) b Frequency (%) Δλmax (nm) e Frequency (%) GSH & NaCl Frequency (%) Δλmax (nm) CSH & NaCl & NaS Δλmax (nm) c f Δλmax (nm) Δλmax (nm) NaS Cys & NaCl & NaS GSH & NaCl & NaS NaS Time (min) Supplementary Figure S3. Selectivity of AuNR-Ag nanoprobes in the presence of biothiols and NaCl at single-particle level. Distribution of single PNP spectral shifts after adding (a) 5 mm cysteine and 150 mm NaCl, (b) 5 mm glutathione and 150 mm NaCl, (c) 5 µm Na S, (d) 5 mm cysteine, 150 mm NaCl and 5µM Na S, and (e) 5 mm glutathione, 150 mm NaCl and 5 µm Na S. The averaged single PNP spectral shifts in the five cases are (a) 1.5 ±. nm, (b) 1.80 ±.46 nm, (c) ± nm, (d) ± 9.99 nm, and (e) ± nm, respectively. (f) Typical time-dependent spectral shifts of single PNPs with or without the addition of biothiols and NaCl. Thus the interference from biothiols and NaCl is negligible.

4 λmax shift (nm) C S,NP ( nm). Supplementary Figure S4. Calculated λ max shifts of a 55 7 nm AuNR-Ag nanoprobe as a function of the amount of sulfide consumed. The effective volume is designated to be µl, which is equivalent to the mean volume of sulfide ion diffusion in 1 s.

5 Supplementary Figure S5. Image processing procedures for retrieving single PNP spectra inside live-cells. Because the scattering intensities of the nanoprobe are much higher than that of cellular organelles, the zero-order (position) and first-order (spectrum) PNP images can be readily identified even in the raw image (a). Image qualities are obviously improved via background subtraction (b). The enlarged image is shown in (c). Comparing with the colour CCD image (d) leads to discrimination of redorange PNPs from white large intracellular organelles. The scale bar is 10 µm.

6 Supplementary Figure S6. Time dependent λ max fluctuation of two PNPs in the cytoplasm of a live HeLa cell in the absence of Na S. The standard deviations are.0 nm and. nm, respectively.

7 Supplementary Figure S7. Dark-field images of PNPs in live-cells. Original (a) and the enlarged (b) spectral images of PNPs inside live HeLa cells after background subtraction that correspond to the colour image (c) containing the two PNPs in Figure 5. The scale bar is 10 µm.

8 λmax (nm) a Probe 1 Probe Time (min) λmax (nm) b Time (min) Supplementary Figure S8. Measured and calculated time-dependent λ max shifts of the nanoprobes inside the cell. (a) Observed (hollow dots) and fitted (solid lines) time-dependent λ max shifts of the two PNPs, P1 and P, in Figure 5. (b) Simulated time-dependent λ max shifts of P1 (red) and P (green) if they were exposed to the same concentrations of sulfide. Solid circles, 100 nm; open triangles, 10 nm. Since the slopes for P1 and P are very different in a, the local sulfide concentrations experienced by P1 and P must be different.

9 a b c d λmax (nm) negative control probe 3 probe 4 probe 5 probe 6 e Time (min) Supplementary Figure S9. Real-time detection of endogenous H S in live-cells. Dark-field colour images (a, c) and the corresponding background-subtracted spectral images (b, d) for endogenous H S imaging in HepG cells without (a, b) and with (c, d) the pretreatment of human insulin. The scale bar is 10 µm. (e) The observed (hollow dots) and fitted (solid lines) time-dependent λ max shifts of PNPs in the HepG cells without adding sulfide sources (negative control), without insulin pretreatment (probe 3 and 4) and with the pretreatment of human insulin (probe 5 and 6). The large difference in the initial λ max values of probe 5 and 6 is attributed to the variation in aspect ratios or Ag shell thicknesses of the AuNRs, but that has no effect on Δλ max measurements.

10 Supplementary Notes Supplementary Note 1: relationship between PNP λ max shift and amount of sulfide consumed The general expression for the refractive index change induced LSPR shift can be obtained from the literature, 3,56 Δλmax m Δn 1 exp( d /ld), (S1) where m is the sensitivity factor (in nm per refractive index unit (RIU)), Δn is the reaction induced refractive index change, d is the effective adsorbate layer thickness and l d is the characteristic EM-fielddecay length. The refractive index change resulting from the chemical reaction is determined by the molar fraction of the produced Ag S, f = C S,NP / (C Ag.0 - C S,NP ), where C S,NP and C Ag,0 are the concentrations of consumed sulfide species and total Ag atoms for each nanoprobe. Then the refractive index change can be described by the follow equation, Δ n = [( 1-f ) n + f n ] n = f ( n n ) Ag S Ag Ag S Ag Ag 0 = ( n n ) C /( C -C ) (S) Ag S Ag S,NP Ag, S,NP where n Ag and n AgS are the refractive index of bulk Ag and Ag S, respectively. By substituting equation S into equation S1, the Ag S fraction dependent LSPR shift can be written as, Δλ m [1 exp( d / l )( ] n n ) C /( C -C ) (S3) max d Ag S Ag S,NP Ag, S,NP 0 For the AuNR-Ag nanoprobes used in this study (L = 54.5 nm, D = 7 nm and Ag shell d thickness is about 3 nm), the total amount of Ag atoms on the surface of an individual PNP, N Ag,0, is about mole. After designating an effective volume arbitrarily (e.g. the mean diffusion volume of sulfide ion in 1 s in this study), we can calculate the LSPR shift as a function of the amount of sulfide based on equation S3 (Supplementary Fig. S3), where the sensitivity factor and characteristic EM-field-decay length were 3400 RIU and 30 nm according to a previous report. 57

11 Supplementary Note : Kinetic spectral analysis for silver-sulfide reaction on the PNP surface Because the concentration of dissolved oxygen in biological systems is generally in the sub-mm range and is much higher than sulfide needed for Ag S formation on the PNP surface, the reaction between solid silver and sulfide in the presence of excessive oxygen can be reduced to a pseudo first-order reaction, dc dt Ag S = k ( CS,eff -CAg S) obs (S4) where k obs is the observed reaction rate constant, C AgS is the concentration of consumed sulfide species and Cs, eff is the effective concentration of sulfide species surrounding the nanoprobe. Cs, eff is determined based on the Freundlich absorption relationship Cs, eff = KC (1/p) S,0, where both K and p are temperature and system related constants. 47,58 Since the Ag S formed on the surface of the Ag shell of the PNP might hinder the diffusion of the sulfide species on the active Ag atom sites, the observed Ag S formation reaction rate constant should be corrected as k obs A-a C = k A Ag S (S5) where A is a pre-exponential Arrhenius factor, a is the site hindrance factor related to Ag S generated on the PNP surface, and k is the actual reaction rate constant. So, equation S4 becomes dc dt Ag S A-a CAg S = k ( CS,eff -CAg S) A a = k (1 - CAg S) ( CS,eff -CAg S) A (S6) Because at the end of the reaction, the reaction rate equals to zero, dc AgS /dt = 0 and C AgS = C Ag,0 /, we have A/a = C Ag,0 /, so we can get dc dt Ag S A-a CAg S = k ( CS,eff -CAg S) A CAg,0 = k ( -CAg S ) ( CS,eff -CAg S ) CAg,0 (S7)

12 By integration with the initial condition that C AgS = 0 when t = 0, equation S7 gives the following results, C AgS C dc Ag S = C 0 Ag,0 Ag,0 0 ( -CAg S) ( CS,eff -CAg S) Ag,0 Ag,0 Ag S S,eff ( Ag S) ln( ) CAg,0-CS,eff CAg,0 CS,eff-CAg S t kdt C C -C C f C = = kt (S8) (S9) By plotting f(c AgS ) versus time t according to the experimental data, the actual reaction rate constant k can be estimated from the slope by least-squares regression. Subsequently, the theoretical kinetic spectral shift curve can be calculated for each concentration of sulfide species. Supplementary References 56. Willets, K.A. & Van Duyne, R.P. Localized surface plasmon resonance spectroscopy and sensing. Annu. Rev. Phys. Chem. 58, (007). 57. Jung, L.S., Campbell, C.T., Chinowsky, T.M., Mar, M.N. & Yee, S.S. Quantitative interpretation of the response of surface plasmon resonance sensors to adsorbed films. Langmuir 14, (1998). 58. Freundlich, H. Colloid and Capillary Chemistry. (Methuen, London, 196).