N. Lee, et al.
DyesandPigments171(2019)107721
Fig. 2. (A) Concentration-dependent SERS spectra of DPA-TAM-AuNPs in the range of 0–100 μM of Zn2+. (B) A calibration curve of the vibrational band intensities at
1174 cm−1 and a linear fitting result for the 0–100 μM regions. (C) The SERS spectra of DPA-TAM on AuNPs in the presence of various metals. (D) Histogram of the
SERS relative intensity at 1174 cm−1. The concentrations of DPA-TAM and metal ions are 200 nM and 60 μM, respectively.
was purified over silica gel using a mobile phase (n-Hexane/EA (v/v,
1:2) as the eluent to yield DPA-TAM (0.241 g, 86%). Mp 78 °C. IR
(neat): νmax 3364.2, 2927.4, 1579.4, 1470.5, 1357.6, 1295.0, 1238.1,
1174.4, 1060.7, 941.1, 828.3, 795.5, 755.0, 714.5, 656.6 cm−1 1H
NMR (CDCl3): δ 8.64 (d, J = 4.69 Hz, 2H), 7.75 (t, J = 7.90 Hz, 2H),
7.39-7.23 (m, 10H), 6.96 (d, J = 9.21 Hz, 2H), 6.87 (d, J = 9.21 Hz,
4H), 5.05 (s, 4H), 3.30 (s, 12H). 13C NMR (MeOH-d6): δ 158.3, 157.7,
155.9, 150.5, 141.3, 140.3, 139.1, 129.3, 128.0, 124.3, 123.0, 114.2,
113.8, 57.7, 40.7. ESI-MS calc. for C35H36ClN5 [M-Cl]+ 526.30, found
526.40. HRMS (FAB) calc. for C35H36ClN5 [M-Cl]+ 526.2971, found
526.2973.
final concentration range between 0 and 3.5 mM was added into the
DPA-TAM solution (10 μM, in ethanol). The mixtures were stabilized for
15 min at 25 °C and then checked by the UV–Visible spectrometer.
For the SERS measurements, 1 μL of the Zn2+ solution (6 mM in
water) was added to 99 μL of the resultant mixture (DPA-TAM-AuNPs).
Subsequently, the 100 μL mixture of DPA-TAM-AuNPs (containing
200 nM of DPA-TAM) and Zn2+ (containing 60 μM final concentration)
was sonicated for 30 s and remained stablized for 30 min at room
temperature, and then the SERS spectra of the {Zn2+-DPA-TAM}-
AuNPs complex with a volume of 100 μL were obtained using a Raman
spectrometer.
2.5. DFM and confocal Raman intracellular imaging of Zn2+
2.3. Preparation of AuNPs and DPA-TAM-AuNPs
SERS spectra were examined using AuNPs prepared according to
Lee and Meisel scheme [24]. The DPA-TAM solution (1 μL, 20 μM in
ethanol) and the AuNP solution (98 μL) were mixed into a 1.5 mL tube,
subsequently sonicated for 30 s, and remained stable for 15 min at
25 °C. The DPA-TAM-coated AuNPs should be immediately prepared
before each of the experiments. The interfacial behavior of DPA-TAM
on AuNPs were examined by SERS with respect to [Zn2+].
Human cervical cancer HeLa cells were obtained from the Korean
cell line bank (KCLB No. 10002). Daphnia magna were cultured in M4
media and HeLa cells were cultured in Dulbecco's Modified Eagle
Medium (DMEM) treated with fetal bovine serum (FBS, 10% (v/v))
purchased from WelGene (Seoul, Korea) and penicillin-streptomycin
(1% (v/v)) at 37 °C in a 5% CO2 atmosphere incubator.
HeLa cells were seeded onto the glass bottom in confocal dishes at a
density of 5 × 104 cells in 2 mL of DMEM medium and incubated
24 h at 37 °C. The cells were washed with pH 7.4 PBS solution, and then
added 2 mL of fresh DMEM (containing 100 μM final concentration of
Zn2+) to the confocal dish, incubated overnight. HeLa cells were
2.4. UV–Visible and SERS detection for Zn2+
For the monitoring of UV–Visible spectra, the Zn2+ solution in the
3