The materials used include calcium chloride
dihydrate (CaCl2·2H2O; Sigma-Aldrich, Japan),
sodium carbonate (Na2CO3, anhydrous; Sigma-Aldrich,
Germany), phosphate buffered saline (PBS buffer, tablets, 0.01 M;
Sigma, USA), fluorescein isothiocyanate-DEX [mol wt (MW): 10, 70,
and 500 kDa; Sigma, USA], rhodamine 6G (Rho6G) chloride (Sigma, England),
ethanol for spectroscopy (99.9%; Merck, Germany), Fluoresbrite calibration
grade 6.0 μm microspheres (Polysciences Inc., UK), and hydrochloric
acid fuming (37%, 0.05 M in all experiments; Merck, Germany). The
water used in all experiments was prepared via a Millipore Milli-Q
purification system and had a resistivity higher than 18.2 MΩ-cm.
Poly(N-isopropylacrylamide)-4-acryloylbenzophenone
(pNIPAM-ABP) was kindly provided by Dr. Leonid Ionov, Germany. Briefly,
pNIPAM-ABP was synthesized from 4-benzophenone acrylate (0.28 g, 1.12
mmol) and NIPAM (6 g, 51.57 mmol) dissolved in 30 mL of ethanol. The
mixture was purged with nitrogen for 30 min. The polymerization was
carried out at 70 °C under a nitrogen atmosphere with mechanical
stirring overnight. The cooled mixture was poured into 750 mL of diethyl
ether, and the precipitate was filtered and dried in vacuum at 40 °C.
dihydrate (CaCl2·2H2O; Sigma-Aldrich, Japan),
sodium carbonate (Na2CO3, anhydrous; Sigma-Aldrich,
Germany), phosphate buffered saline (PBS buffer, tablets, 0.01 M;
Sigma, USA), fluorescein isothiocyanate-DEX [mol wt (MW): 10, 70,
and 500 kDa; Sigma, USA], rhodamine 6G (Rho6G) chloride (Sigma, England),
ethanol for spectroscopy (99.9%; Merck, Germany), Fluoresbrite calibration
grade 6.0 μm microspheres (Polysciences Inc., UK), and hydrochloric
acid fuming (37%, 0.05 M in all experiments; Merck, Germany). The
water used in all experiments was prepared via a Millipore Milli-Q
purification system and had a resistivity higher than 18.2 MΩ-cm.
Poly(N-isopropylacrylamide)-4-acryloylbenzophenone
(pNIPAM-ABP) was kindly provided by Dr. Leonid Ionov, Germany. Briefly,
pNIPAM-ABP was synthesized from 4-benzophenone acrylate (0.28 g, 1.12
mmol) and NIPAM (6 g, 51.57 mmol) dissolved in 30 mL of ethanol. The
mixture was purged with nitrogen for 30 min. The polymerization was
carried out at 70 °C under a nitrogen atmosphere with mechanical
stirring overnight. The cooled mixture was poured into 750 mL of diethyl
ether, and the precipitate was filtered and dried in vacuum at 40 °C.