Biomimic Light Trapping Silicon Nanowire Arrays for Laser Desorption/Ionization of Peptides

Abstract

This article describes a low cost method of generating silicon nanowire arrays that have similar structure and light trapping ability as moth-eye for matrix-free laser desorption/ionization mass spectrometry analysis of small molecules without matrix peak interference. The nanowire array is produced by combining low cost nanosphere lithography and metal nanoparticle-assisted chemical etching of silicon. Owing to their excellent light trapping ability over broad spectral range, silicon nanowire arrays can absorb incoming laser light efficiently, and convert laser energy to heat, which allows efficient desorption/ionization of intact peptide/proteins without matrix. Compared to existing matrixfree substrate such as porous silicon substrates, the biomimic silicon nanowire arrays are better in terms of lower laser energy, structural tunability, and low spatial resistance.

Vertical SiNWAs for biomedical and biotechnology applications

“…65 Due to the non-adhesiveness of PEG hydrogels toward proteins, proteins were selectively immobilized on the pre-modied SiNWAs regions to create protein micropatterns. 67,68 Compared with other conventional LDI-MS substrates, the SiNWAs exhibit several advantages, such as excellent light trapping ability over a broad wavelength range, high efficiency of light-to-heat conversion to desorb/ionize analytes (such as proteins and peptides), large surface area to allow for the retention of analytes, and an open interwire space to allow the ionized analytes to leave, making them good substrates for the LDI-MS analysis of small biomolecules. Immunobinding assays between IgG and anti-IgG and between IgM and anti-IgM that were performed on the micropatterned SiNWAs emitted stronger uorescent signals and exhibited higher sensitivities compared with those performed on smooth silicon substrates.…”

Surface-assisted laser desorption/ionization mass spectrometry using ordered silicon nanopillar arrays

“…However, the inltration of analytes into the pores in some instances can cause loss in signal intensity due to attenuation of the laser signal. 32,33 DIOS has been under extensive investigation as to which factors contributed to efficient desorption/ionization. 34,35 Factors such as surface area, optical absorption, thermal conductivity, as well as pH levels and solvent contribution, have all been studied in the context of the mechanisms involved in the desorption and protonation of the analyte molecules.…”

“…40,41 Furthermore, the MACE reaction mechanism allows for the introduction of cracks and pores to the fabricated structures to increase the surface area by manipulating the concentration of the oxidizing agent in the reaction solution as described by Chiappini et al 41 In the investigation described by Wang et al, arrays of hexagonally arranged silicon nanowires fabricated through gold-catalyzed MACE and nanosphere lithography were used for SALDI-MS to detect a group of small peptides. 33 The authors used silicon nanowire arrays with 200 nm diameter, 2000 nm length, and an aspect ratio of 10. Furthermore, the inter-nanowire spacing was determined to be in the range of 400 nm.…”

“…In this paper, we adapted the fabrication strategy described by Wang et al 33 but used Ag as a catalyst instead of Au since Ag has been shown to have similar catalytic properties to Au in the context of the MACE reaction and is cheaper. 41 We also focused on fabricating and using nanostructures with low aspect ratios and lengths similar to what is typically used in DIOS as opposed to the high aspect ratio structures described by Wang et al 33 Our approach resulted in cylindrical pillars with aspect ratios <10 which we term silicon nanopillars (SiNPs). We explored the exibility of ordered SiNP formation via MACE and investigated the inuence of nanopillar length, aspect ratio and porosity on desorption/ionization performance and efficiency.…”

Optical properties of “black silicon” formed by catalytic etching of Au/Si(100) wafers

“…[8][9][10][11][12][13][14] In addition to Ag, Au metal has been used as catalyst in fabricating Si nanostructures. [15][16][17][18][19][20][21][22] To the best of our knowledge, however, no detailed systematic study on the nanostructure properties of catalytic-etched Au/Si surfaces has been performed.…”