Bombarding Cancer: Biolistic Delivery of therapeutics using Porous Si Carriers

Neta Zilony1,2,*, Adi Tzur-Balter3,4*, Ester Segal4,5, Orit Shefi1,2

1Faculty of Engineering, Bar-Ilan University, Ramat-Gan 52900, Israel

2Bar-Ilan Institute of Nanotechnologies and Advanced Materials, Ramat-Gan, 52900, Israel

3The Inter-Departmental Program of Biotechnology, Technion – Israel Institute of Technology, Haifa 32000, Israel

4Department of Biotechnology and Food Engineering, Technion – Israel Institute of Technology, Haifa 32000, Israel

5Russell Berrie Nanotechnology Institute, Technion – Israel Institute of Technology, Haifa 32000, Israel

*These authors contributed equally to this work

Correspondence and requests for materials should addressed to O.S. (email: ) or to E.S. (email: ).

SUPPLEMENTARY DATA

Chemical characterization of fluorescently labeled PSi particles -

To confirm the chemical modification of fluorescently labeled PSi particles, the carriers were characterized by Attenuated Total Reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, before and following thermal hydrosilylation and Texas-red labeling. The spectrum of the freshly-etched PSi depicts bands characteristic of surface hydride species. Bands assigned to Si-Hx stretching modes at 2249 cm-1 (νSi-H3), 2113 cm-1 (νSi-H2), and 2098 cm-1 (νSi-H) are apparent. An additional band, associated with Si-H deformations, at 906 cm-1 is observed 1. Undecanoic acid-terminated PSi (u-PSi) displays bands characteristic of asymmetric and symmetric νCH2 stretching vibrations at 2924 cm-1 and 2850 cm-1, respectively. Furthermore, a strong band assigned to carboxylic acid νC=O stretching vibration at 1716 cm-1, and a combination band due to the νC=O stretching and δO-H deformation vibrations of carboxylic acid at 1411 cm-1 are observed 2, 3. 1-Ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride (EDC) is used to link the amines of the Texas red hydrazide (TRH) molecules to the carboxylic acid groups on the u-PSi scaffold, forming an amide bond. The FTIR spectrum of the PSi surface after treatment with EDC and TRH (TRH-PSi) exhibits a band of amide I at 1654 cm-1 (C=O stretching vibrations), indicative of covalent attachment of TRH to the Si scaffold (this band was not observed when EDC was omitted from the labeling procedure). In addition, the spectrum of TRH-PSi depicts new bands at 1300 cm-1 (asymmetric νSO2), 1382 cm-1 (asymmetric νSO2), 1461 cm-1 (aromatic νC=C and νC=N), 1497 cm-1 (aromatic νC=C), 1541 cm-1 (aromatic νC=C), 1599 cm-1 (aromatic νC=C) and 1816 cm-1 (aromatic C-H out-of-plane deformation vibrations), ascribed to the characteristic groups of TRH.

Supplementary Fig. S1. Attenuated Total Reflectance Fourier transform infrared (ATR-FTIR) spectra of PSi, before and following chemical modification and Texas-red labeling: freshly-etched PSi (PSi), undecanoic acid-terminated PSi (u-PSi), and Texas red-labeled PSi (TRH-PSi). Spectra are offset along the y-axis for clarity.

Cell viability assay measured 16h post biolistic delivery of MTX-loaded PSi microparticles -

In order to further validate the effect of the delivered MTX drug on the cancer cells, we have performed the viability assay 16 hours post bombardment, prior to cell multiplication which occurs approximately every 24 h. Indeed, at this time point a profound cell death of 50±6% is observed (Supplementary Fig. S1).

Supplementary Fig. S2. Cell viability measured 16h after biolistic delivery of MTX-loaded PSi microparticles, showing the normalized percentage of cells, compared to control plates (cells only, white bar), following biolistic delivery of neat PSi (gray bar) and drug-loaded PSi (black bar). Data are the average percentage ± S.D of 4 independent experiments,*p<0.0002.

References Cited

1.  Anglin E. J., Schwartz M. P.& Ng V. P., Perelman LA, Sailor MJ. Engineering the Chemistry and Nanostructure of Porous Silicon Fabry-Perot Films for Loading and Release of a Steroid. Langmuir,20:11264-11269 (2004)

2.  Alvarez S. D., Derfus A. M., Schwartz M. P., Bhatia S. N. & Sailor M. J. The Compatibility of Hepatocytes with Chemically Modified Porous Silicon with Reference to in Vitro Biosensors Biomatrials ,30:26-34 (2009).

3.  Schwartz M. P., Cunin F., Cheung R. W. & Sailor M. J. Chemical Modification of Silicon Surfaces for Biological Applications. Physica Status Solidi a-Applications and Materials Science, 202:1380-1384 (2005).