Supporting Information:
Ionic Functionalization of Hydrophobic Colloidal Nanoparticles to Form Ionic Nanoparticles with Enzyme-like Properties
Yuan Liu†, Daniel L. Purich§, Cuichen Wu†, ‡, Yuan Wu‡, Tao Chen‡, Cheng Cui†, Liqin Zhang†, Sena Cansiz†, Weijia Hou†, Yanyue Wang†, Shengyuan Yang† and Weihong Tan*, †, ‡ †
Center for Research at Bio/Nano Interface, Department of Chemistry and Department of Physiology and Functional Genomics, Health Cancer Center, UF Genetics Institute and McKnight Brain Institute, University of Florida, Gainesville, Florida 32611-7200, United States. ‡Molecular Science and Biomedicine Laboratory, State Key Laboratory of Chemo/Bio-Sensing and Chemometrics, College of Biology and College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China. §Department of Biochemistry and Molecular Biology, College of Medicine, University of Florida, Gainesville, Florida 32610-0245, United States.
Figure S1. IR spectroscopy of dopamine and FePt before (OA/OAm) and after ligand exchange with dopamine.
Figure S2. IR spectra of 3, 4-DHCA and FePt before (OA/OAm) and after ligand exchange with 3, 4-DHCA.
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Figure S3. IR spectra of 4-ATP and CdSe before (myristic acid (MA)) and after ligand exchange with 4-ATP.
Figure S4. IR spectra of 4-MCBA and CdSe before (MA) and after ligand exchange with 4-MCBA.
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Figure S5. ζ-potential measurement for FePt-Dopamine showing positive surface charge, and FePt-3, 4DHCA showing negative surface charge in water.
Figure S6. ζ-potential measurement for Pd-4-ATP showing positive surface charge, and Pd-4-MCBA showing negative surface charge in water.
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Figure S7. NMR results of ligands released from Fe3O4 before and after ligand exchange. The purple line shows 3, 4-DHCA and FeCl3; the dark green line shows ionized Fe3O4 NPs (after ligand exchange) capped with 3, 4-DHCA dissolved by HCl (1.2 M); the light green line shows Fe3O4 NPs (before ligand exchange) capped with oleic acid dissolved by HCl (1.2 M); the red line shows oleic acid and FeCl3. All of the samples were dissolved in d-methanol for NMR tests. To prepare the samples, hydrophobic Fe3O4 NPs (before ligand exchange) capped with oleic acid and hydrophilic Fe3O4 NPs (after ligand exchange) capped with 3, 4-DHCA were dissolved by HCl (1.2M) via sonication. The mixtures were dried by air blow and further degassing with schlenk line. Because both oleic acid and 3, 4-DHCA can be dissolved in methanol, the ligand residue including FeCl3 was dissolved in d-methanol for NMR tests. To better compare the characterization of ligands released from Fe3O4 NPs, two parallel samples (Oleic acid with FeCl3 in d-methanol and 3, 4-DHCA with FeCl3 in d-methanol) were prepared. From the NMR results, a near quantitative ligand exchange was achieved, indicating a high degree of ligand exchange.
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Calculation of concentration of nanozymes Number of FePt nanoparticles Average size of FePt
d = 3.2 nm
Density of FePt:
ρ = 14 g/cm
Concentration of aqueous FePt solution:
C = 3.5 μg/μL
Mass of one FePt nanoparticle is = ρ ∙ ∙ π ∙ = 2.4 × 10"#$ g *
Concentration of aqueous FePt in number: C%&'() = +&'() = 1.46 × 10# /μL &'()
For each catalytic reaction, 5 µL (V) of FePt nanoparticles were added to a 200 µL volume of TMB
solution. Thus the total number of FePt nanoparticles is N = C%&'() ∙ V = 7.3 × 10#, and the
concentration of FePt 0E 2 is given by
N3 = 6.02 × 10 mol"# V678 = 5 + 200 = 205 μL
N 0E 2 = N3 :V = 5.9 × 10"< mol/L 678
For Fe3O4, 10 µL of Fe3O4 nanoparticles were added to a 200 µL volume of TMB solution each time. Average size of Fe3O4
a> ?@ = 14.9 nm
Density of Fe3O4:
ρ> ?@ = 5 g/cm
Concentration of aqueous Fe3O4 solution:
C> ?@ = 2.5 μg/μL
Similarly, the concentration of Fe3O4 is AE> ?@ B = 1.2 × 10"C mol/L S6 / S16
For Pd, 10 µL of Pd nanoparticles were added to a 200 µL volume of TMB solution each time. Average size of Pd
d = 4.2 nm
Density of Pd:
ρ = 11.9 g/cm
Concentration of aqueous Pd solution:
C = 2.0 μg/μL
Similarly, the concentration of Pd is 0E 2 = 3.4 × 10"< mol/L For CdSe, 20 µL of CdSe nanoparticles were added to a 300 µL volume of TMB solution each time. Average size of CdSe
d* D = 4.5 nm
Density of CdSe:
ρ* D = 5.8 g/cm
Concentration of aqueous CdSe solution:
C* D = 3.5 μg/μL
Similarly, the concentration of CdSe is 0E* D 2 = 0.9 × 10"F mol/L Calculation of the initial velocity and kinetic parameters of nanozyme. G=H∙I∙J I = GKH ∙ J
The length of cuvette is 0.2 cm. The extinction coefficient (S7) of oxidized TMB product at 652 nm is HFL = 3.9 × 10 M "# cm"# The initial velocity was determined by νOPOQ =
R0S2 RT
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UOPOQ
I# − I = = ∆T
G#K G H ∙ J − KH ∙ J = 1 ∙ G# − G = 12820 × 10"C ∙ G# − G X ∆T ∆T ∆T H∙J νOPOQ = 1
UOPOQ
=
R0S2 YZ[\ 0]2 = RT ^Z + 0]2
^Z + 0]2 ^Z 1 1 = + YZ[\ 0]2 YZ[\ YZ[\ 0]2 _`abcd =
^Z YZ[\
ROPQdefdcQ =
1
YZ[\
YZ[\ = _f[Q 0g2 A refers to the absorbance of oxidized TMB product at 652 nm. ε refers to the extinction coefficient of oxidized TMB product at 652 nm. h refers to the optical path length in the cuvette. c refers to the concentration of oxidized TMB product. νinit refers to the initial velocity of TMB oxidation. [S] is the TMB substrate concentration. Vmax is the maximum rate. [E] is the nanozyme concentration. kcat is the turnover number which means the maximum number of substrate molecules converted to product per enzyme molecule per second. Km is the Michaelis constant. It is the substrate concentration at which the reaction rate is
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ijkl .
Figure S8. UV/Vis absorbance of TMB (colorless) and oxidized TMB product (blue).
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Figure S9. pH dependent relative peroxidase activity of ionic nanoparticles. To determine the relative peroxidase activity, FePt-dopamine (5 µL, 3.5 mg/mL), FePt-3, 4-DHCA (5 µL, 3.5 mg/mL), Fe3O4dopamine(10 µL, 2.5 mg/mL), Fe3O4-3, 4-DHCA (10 µL, 2.5 mg/mL), Pd-4-ATP (10 µL, 2 mg/mL), or Pd-4MCBA (10 µL, 2 mg/mL) was added to 200 µL of TMB solution (1.5 mM) with different pH values. Absorbance (652 nm) was taken at 15 min and normalized.
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Figure S10. Plot of maximal velocity versus total nanozyme (FePt) concentration.
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Figure S11. Peroxidase activity of amino terminal FePt with oxygen and argon saturated TMB solution (absorbance at 652 nm). To monitor the peroxidase activity, 5 µL of FePt (3.5 mg/mL) nanoparticles were added to a 200 µL volume of standard TMB solution (1.5 mM, pH=3).
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Figure S12. Optical absorption spectra of CdSe stabilized with different ligands in different solvents. The black curve shows the absorption spectrum for CdSe capped with the original myristic acid ligands in hexane. The red curve shows the absorption spectrum for CdSe capped with 4-ATP in water. The blue curve shows the absorption spectrum of CdSe capped with 4-MCBA in water.
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Figure S13. Peroxidase activity of CdSe-4-ATP and CdSe-4-MCBA. To monitor the peroxidase activity of CdSe, 20 µL of CdSe-4-ATP (3.5 mg/mL) and CdSe-4-MCBA (3.5 mg/mL) were added to separate 300 µLTMB solutions (1.5 mM, pH=3). Absorbance (652 nm) was measured at different times.
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Figure S14. Peroxidase activity of CdSe-4-ATP at different conditions (no H2O2 added): a is TMB solution only (1.5 mM), b is TMB (1.5 mM, pH=3) with added CdSe-4-ATP (20 µL, 3.5 mg/mL) after 11 hours of illumination, c is TMB (1.5 mM, pH=3) with added CdSe-4-ATP (20 µL, 3.5 mg/mL) in the dark for 11 hours, d is TMB (1.5 mM, pH=7) with added CdSe-4-ATP (20 µL, 3.5 mg/mL) after 11 hours of illumination, e is TMB (1.5 mM, pH=11) with added CdSe-4-ATP (20 µL, 3.5 mg/mL) after 11 hours of illumination. All of the TMB volumes are 200 µL.
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Figure S15. A control experiment was conducted under different conditions (no H2O2 added) for CdSe-4MCBA: a is TMB solution only (1.5 mM), b is TMB (1.5 mM, pH=3) with CdSe-4-MCBA (20 µL, 3.5 mg/mL) after 11 hours of illumination, c is TMB (1.5 mM, pH=3) with added CdSe-4-MCBA (20 µL, 3.5 mg/mL) in the dark for 11 hours, d is TMB (1.5 mM, pH=7) with added CdSe-4-MCBA (20 µL, 3.5 mg/mL) after 11 hours of illumination, e is TMB (1.5 mM, pH=11) with added CdSe-4-MCBA (20 µL, 3.5 mg/mL) after 11 hours of illumination. All TMB volumes are 200 µL.
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