Supporting Information
Metal Nanoparticle-Loaded Microgels with Selective Permeability
for Direct Detection of Small Molecules in Biological Fluids
Dong Jae Kim,† Tae Yoon Jeon,† Youn-Kyoung Baek,‡ Sung-Gyu Park,‡ Dong-Ho Kim‡,*
and Shin-Hyun Kim†,*
†Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of
Science and Technology (KAIST), Daejeon, 305-701 Republic of Korea
‡Advanced Functional Thin Films Department, Korea Institute of Materials Science (KIMS),
Changwon, Gyeongnam, 641-831 Republic of Korea
Figure S1. Gold nanoparticles used for the SERS measurements. Transmission electron
microscopy (TEM) images of gold nanoparticles with an average diameter of 38 nm,
synthesized using the sodium citrate reduction method.
Figure S2. (a-c) Confocal microscopy images of microgels dispersed in an aqueous solution
containing fluorescein isothiocyanate (FITC)-tagged dextran having the molecular weights
denoted in each panel. (a) Microgels prepared from 10 w/w% PEGDA were permeable to
dextran with a Mw of 40,000 g mol–1 and impermeable to dextran with a Mw of 70,000 g
mol–1. (b) Microgels prepared from a 30 w/w% PEGDA solution were permeable to dextran
with a Mw of 20,000 g mol–1 and impermeable to dextran with a Mw of 40,000 g mol–1. (c)
Microgels prepared from 70 wt% PEGDA were permeable to dextran with Mw of 10,000 g
mol–1 and impermeable to dextran with a Mw of 20,000 g mol–1.
Figure S3. Confocal microscopy images of microgels dispersed in a mixture of rhodamine B
isothiocyanate (RITC)-tagged dextran with a Mw of 10,000 g mol–1 and FITC-tagged dextran
with a Mw of 20,000 g mol–1. RITC-tagged dextran with a hydrodynamic diameter of 5 nm
selectively infused into microgel, whereas FITC-dextran with a diameter of 7 nm was
excluded.
Figure S4. (a–c) Series of confocal microscopy images of microgels dispersed in aqueous
solution of sulforhodamine B (a), RITC-tagged dextran with a Mw of 10,000 g mol–1 (b),
FITC-tagged dextran with a Mw of 20,000 g mol–1 (c). The images were collected at the
indicated times after the introduction of the dye solutions.
Figure S5. (a–c) Optical microscopy images of monodisperse microgels in hexadecane (a),
water (b), and air (c). (d) Scanning electron microscopy (SEM) image of the dried microgels.
Figure S6. Raman spectra of the microgels immersed in water or the dried particles in air, in
the absence of analytes.
Figure S7. (a) Raman spectra of benzenethiol (BT), measured using the wet microgel, dried
particles, or surrounding solution at a concentration of 0.1 mM. (b) Raman spectra of BT,
measured from the centers of five arbitrarily selected microgels dispersed in 0.01 mM
aqueous solutions of the analyte.
Figure S8. The Raman spectra of rhodamine 6G (R6G), measured from the centers of five
arbitrarily selected microgel samples dispersed in 1 mM aqueous solutions of the analyte.
Figure S9. (a, b) Optical microscopy image of microgel and Raman spectra of 1 mM R6G
measured at four different locations denoted in (a). A focal plane for Raman measurement
was in middle of the microgel. (c, d) Optical microscopy images of microgel and Raman
spectra of 1 mM R6G, taken at three different positions of focal plane denoted in the
schematic in (a). Raman spectra were all measured from the center of microgel.
Figure S10. (a) Raman spectra of 10-6 M R6G measured at wet microgel containing different
gold nanoparticle (AuNP) concentration, where the Raman spectra were acquired at the
centers of microgels. (b) Raman spectra of 10-6 M R6G measured from four different
positions, in a microgel containing 2 wt% AuNP, denoted in the inset.
Figure S11. Raman spectra of rhodamine 6G over the range 580–640 cm–1, measured using
the wet microgel (left) and dried particles (right), where the microgels are immersed in
aqueous solutions of rhodamine 6G having a variety of concentrations prior to measurement.
Figure S12. (a-c) Optical microscopy images of microgels: the microgel dispersed in water (a)
is completely dried (b), and then re-dispersed in water after 2 days (c). (d) Raman spectra of 1
mM R6G, measured using original microgel (Initial) and rehydrated microgels (Re-swollen
1-3). Raman intensities are all comparable.
Figure S13. Microgels prepared with magnetic nanoparticles may be concentrated using an
external magnetic field.
Figure S14. Raman spectra of 0.1 mM benzenethiol, measured in the presence of gold
nanoparticles dispersed in milk or water. The Raman signal intensity collected in the milk
sample was much smaller than the signal intensity collected from water.