Supplementary Materialsfor

Nanostructured TiO2 Catalyzed Oxidations of Caffeine and Isocaffeine and their Cytotoxicity and Genotoxicity towards Ovarian Cancer Cells

Xiaoxi Huang1, Anandarup Goswami1,2, Xiaoxin Zou1,2, Stephanie Hayes1, Vatsal Shah3, Tamara Minko3, Zhimin Tao1,2*, Tewodros Asefa1,2,4*

1Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610Taylor Road, Piscataway, New Jersey 08854, USA

2 Department of Chemical and Biochemical Engineering, Rutgers, The State University of NewJersey, 98 Brett Road, Piscataway, New Jersey 08854, USA

3Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 160Frelinghuysen Road, Piscataway, New Jersey 08854, USA

4 The Institute for Advanced Materials, Devices and Nanotechnology (IAMDN), Rutgers, The State University of New Jersey, 607 Taylor Road, Piscataway, New Jersey 08854, USA

*To whom correspondence should be addressed. E-mail: (T.A.) ; (Z.T.)

Table S1. Results obtained after linear curve-fitting that passes through zero of the graphs of the sum of intensities of each individual band of caffeine or isocaffeine in different solvents vs. concentration. (In the case of caffeine in all the solvents and isocaffeinein PBS, the absorbance of peaks in the ranges of 205-210 nmwas beyond the maximum measurable absorbance on the UV-Vis instrument, and they are thus not included).

Compound / Solvent / Wavelength ranges / Curve-fitting results
Caffeine / Water / 225-235 nm / S225-235=0.055[caffeine] (r20.99)
270-275 nm / S270-275=0.0564[caffeine] (r20.99)
PBS / 225-235 nm / S225-235=0.055[caffeine] (r20.99)
270-275 nm / S270-275=0.0567[caffeine] (r20.99)
Ethanol / 225-235 nm / S225-235=0.0527[caffeine]+0.2776 (r20.99)
270-275 nm / S270-275=0.0524[caffeine]+0.0586 (r20.99)
Isocaffeine / Water / 205-210 nm / S205-210=0.1085[caffeine] (r20.97)
235-240 nm / S235-240=0.0416[isocaffeine] (r20.99)
265-270 nm / S265-270=0.0518[isocaffeine] (r20.99)
PBS / 235-240 nm / S235-240=0.0402[isocaffeine] (r20.99)
265-270 nm / S265-270=0.0499[isocaffeine] (r20.99)
Ethanol / 205-210 nm / S205-210=0.0605[caffeine] + 0.8933(r20.97)
235-240 nm / S235-240= 0.042[isocaffeine]+0.3062 (r20.99)
265-270 nm / S265-270=0.0439[isocaffeine]+0.0621 (r20.99)

1H NMR characterization: 10mM caffeine and 10 mM isocaffeine were prepared in D2O, and their 1H NMR spectra were run with Varian VNMRS (500 MHz). The oxidized caffeine and isocaffeine products were lyophilized and then re-dissolved in D2O before their 1H NMR spectra were obtained with the same instrument. The results are shown in Figures S4 - S9.

Figure S4.1H NMR spectra of caffeine in D2O.

FigureS5.1H NMR spectra of isocaffeine in D2O.

Figure S6.1H NMR spectra of caffeine and oxidized caffeine in D2O, chemical shift () from 4.3 to 0.0 ppm

Figure S7.1H NMR spectra of caffeine and oxidized caffeine in D2O,with from 9.0 to 7.0 ppm.

Figure S8.1H NMR spectra of isocaffeine and oxidized isocaffeine in D2O, in the range of 4.1 to 0.0 ppm.

Figure S9.1H NMR spectra of isocaffeine and oxidized isocaffeine in D2O, measured in the range of 9.0 to 7.0 ppm.

ESI-MSspectral analysis: 200μM caffeine or isocaffeine was prepared, and 0.5mg/mL P25 TiO2 nanoparticles was added into each solution. The mixture was kept stirring under UV irradiation for 6hto undergo photocatalytic oxidations, followed by centrifugation to remove the nanoparticles. After addition of 1% acetic acid to the supernatant, their electrospray ionization-mass spectrometry (ESI-MS) was performed on the samples(in positive ion mode) to get their mass spectra. The spectra areshown in Figures S10andS11 andthe results are summarized in Table S2.

Figure S10. ESI-MS spectraof caffeine after oxidation for 6h with UVirradiation in the presence of P25 TiO2nanoparticles.

Figure S11. ESI-MS spectraof isocaffeine after oxidation for 6hwith UV irradiation in the presence of P25TiO2 nanoparticles.

TableS2. Possible products of caffeine and isocaffeine after oxidation (continued on the next page).

m/z / Molecular ion / Possible oxidized product of caffeine / Possible oxidized product of isocaffeine
115 / 114 / /
143 / 142 / /
165 / 164 / Likely associated with the Na+-adduct of the species with m/z = 143
175 / 174 / / Not Observed
187 / 186 / /
211 / 210 / / Not Observed
225 / 224 / other isomers / other isomers
other isomers / other isomer
247 / 246 / Likely associated with the Na+-adduct of the species with m/z = 224

TableS3. Possible products of caffeine and isocaffeine after oxidation (continued).

m/z / Molecular Ion / Possible oxidized product of caffeine / Possible oxidized product of isocaffeine
269 / 268 / + other isomers / + other isomers
+ other isomers / + other isomers

Commercially available P25 TiO2nanoparticles (Degussa/Evonik): The P25 TiO2nanoparticles used in this study were purchased from Degussa/Evonik). It is worth noting here that P25 TiO2 is among the most commonly studied semiconducting materials in areas ranging from photocatalysis to dye-sensitized solar cells [1, 2].Its structural features can be found in several published worksinvolving P25 TiO2 that were reported by us [1, 2] and others [3-5](e.g., Figure S12) as well as from the company’s (Degussa/Evonik’s) and many other web-sites [6].

Figure S12. Field emission scanning electron microscope (FE-SEM) image of P25 TiO2nanoparticles (Scale bar = 200 nm).

Reference and Notes (for Supplementary Materials)

  1. Ahmed S, Du Pasquier A, BirnieDP (2011) Improving microstructured TiO2 photoanodes for dye sensitized solar cells by simple surface treatment.Adv Energy Mater1: 879-887
  2. Ahmed S, Du Pasquier A, BirnieDP, AsefaT (2011)Self-assembled TiO2 with increased photoelectron production and improved conduction and transfer: enhancing photovoltaic performance of dye-sensitized solar cells. ACS Appl Mater Interfaces 3: 3002-3010
  3. Deiana C, Fois E, Coluccia S, MartraG (2010)Surface structure of TiO2 P25 nanoparticles: infrared study of hydroxy groups on coordinative defect sites.J Phys Chem C114: 21531-21538
  4. Hurum DC, Agrios AG, GrayKA (2003) Explaining the enhanced photocatalytic activity of Degussa P25 mixed-phase TiO2 using EPR.J Phys Chem B107: 4545-4549
  5. Yu J, Yu H, ChengB, Zhou M, Zhao X(2006) Enhanced photocatalytic activity of TiO2 powder (P25) by hydrothermal treatment.J Mol Catal A: Chem 253:112-118

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