Supplementary materials

Copper (I) Oxide Nanoparticle and Tryptophan as its Biological Conjugate: A Modulation of Cytotoxic Effects

Mritunjoy Maitya, Sumit Kumar Pramanikb, Uttam Pala, Biswadip Banerjib, Nakul Chandra

Maiti*a

aDivision of Structural Biology and Bioinformatics and, bDivision of Chemistry;

CSIR-Indian Institute of Chemical Biology;

4, Raja S.C. Mullick Road, Kolkata, India-700032;

Fax: (+) 91 33 24723967; Tel: (+) 91 33 24995940

Absorption Spectra:

Absorption Spectra of tryptophan coated Cu2O nanoparticles given in figure S1. It shows that

the absorption band of Cu2O nanoparticle at ~ 470nm was disappeared and pecks at around

278 nm corresponding to tryptophan was appeared. Due to the presence of colloidal particles

of CuNP-Trp, there was a scattering in absorption spectra.

Figure S1

Absorption Spectra of Cu2O nanoparticles after 90 days kept in vacuum condition.

Figure S2

Stability study of CuNP-Trp conjugate in Dulbecco's Modified Eagle Medium (DMEM)

1.1 Absorption study

2 mg dry sample of CuNP-Trp was dispersed in 10 ml double distilled water. 200 l of the

prepared solution was added to 2 ml of DMEM (low glucose, pyruvate, no glutamine, and no

phenol red) and record the absorption spectra using DMEM as reference solvent. The

absorption spectrum is shown in figure S3. From the spectra it was shown that with the

increase of time interval the absorbance increases at 278 nm because of the release of some

tryptophan residues from the CuNPs surface. We have recorded the absorption for 48 hours.

Figure S3

1.2 X-ray diffraction study to confirm stability of the CuNPs-Trp

50 mg of dry CuNPs-Trp sample was dispersed in Dulbecco's Modified Eagle Medium and

incubated at 37oC for 96 hours. Subsequently the solution was centrifuged at 12000 rpm for

20 min and collected the sedimented particles. This was again dispersed in double distilled

water and centrifuge and repeated twice. Collected particle was dried at 50 oC for 6 hours and

XRD was taken from the dried sample (figure S4). The diffraction pattern was similar to the

original diffraction pattern (figure 3, main manuscript) except some attenuation of the peak

originated due to aromatic ring of the L-tryptophan. It confirmed that the CuNP-Trp in

biological medium was not highly unstable and the release of tryptophan occurred slowly.

Figure S4

X-ray diffraction Line Broadening Analysis (LBA)

Crystal size of Cu2O nanoparticles was determined using Scherrer formula:

d = (KCos x (180/

Where d : thickness of the crystallite in the direction perpendicular to the diffracting planes

(hkl) i.e. mean size of the crystalline domains, it may be smaller or equal to the particle size,

K = Scherrer constant, typical value is 0.9, but it changes with the actual shape of the

crystallite, : X-ray wavelength. Cu K radiation sources was used, = 1.54060Å : the

line broadening at half the maximum intensity (FWHM), was measured by fitting the raw

data (obtained by XRD) with Voigt function, OriginPro graph. Figure S5 displays the fitted

curve (red) and was 1.14397 radian at 2 ~36.709o. Using the obtained and Scherrer

formula obtained d value was 7.4049 nm.

The average size of the nanoparticles was estimated using Debye-Scherrer equation and

measuring the width of the (111) diffraction line of XRD patterns. X-ray diffracted data (the

major peak) was fitted with Voigt function to obtain the FWHM and was used in Debye-

Scherrer equation to derive the β. The estimated crystalline size of the powdered CuNPs was

~7 nm.

Figure S5

Figure S6: Size distribution profiles of CuNPs (A) and CuNP-Trp (B) suspended in water.

Solutions of the nanoparticles were prepared by the dispersing the particles in water (1mg/ 10

ml water). It was diluted to ~55μg/ml to yield an optimum scattering intensity for DLS

measurements on a Malvern Zetasizer Nano ZS90 (Malvern instruments Ltd., UK)

instrument equipped with a He-Ne laser of 633nm. The experiment was carried out at 25 oC.

The scattered light from the sample was detected by a photomultiplier tube placed at 90° to

the incident laser beam. The measured diameter of the CuNPs was 95 nm and the value was

127 nm for the conjugate.

A

B

Figure S7. Expanded TEM images (from Figure 5) of individual particle of CuNPs and its

conjugate with L-tryptophan

CuNPs CuNP-Trp