Ultrathin calcinated films on a gold surface for highly effective laser desorption/ ionization of biomolecules

Abstract

A nanoscale calcinated silicate film fabricated on a gold substrate for highly effective, matrix-free laser desorption ionization mass spectrometry (LDI-MS) analysis of biomolecules. The calcinated film is prepared by a layer-by-layer (LbL) deposition/calcination process wherein the thickness of the silicate layer and its surface properties are precisely controlled. The film exhibits outstanding efficiency in LDI-MS with extremely low background noise in the low-mass region, allowing for effective analysis of low mass weight samples and detection of large biomolecules including amino acids, peptides and proteins. Additional advantages for the calcinated film include ease of preparation and modification, high reproducibility, low cost and excellent reusability.

What is claimed is: 
     
         1 . A nanoscale film, comprising:
 a sublayer; and   a nanoscale metallic layer with low heat conductivity on the sublayer.   
     
     
         2 . The film of  claim 1 , wherein the metallic layer is a calcinated silicate film. 
     
     
         3 . The film of  claim 2 , wherein the nanoscale calcinated silicate film comprises a plurality of alternating layers of poly(allylatnine hydrochloride) (PAH) and sodium silicate solution. 
     
     
         4 . The film of  claim 3 , wherein the sublayer is gold (Au), platinum (Pt), silver (Ag), aluminum (Al) and/or stainless steel. 
     
     
         5 . The film of  claim 3 , wherein the sublayer is a thin layer of gold. 
     
     
         6 . The film of  claim 5 , wherein the thin layer of gold has a thickness of approximately 10 to 2000 nm. 
     
     
         7 . The film of  claim 4 , wherein the thin layer of gold has a thickness of approximately 46 nm 
     
     
         8 . The film of  claim 3 , wherein the plurality of alternating layers of PAH and sodium silicate solution has a thickness of approximately of 2-50 nm. 
     
     
         9 . The film of  claim 5 , wherein the thin layer of gold is fabricated by e-beam deposition of a layer of gold onto a slide. 
     
     
         10 . The film of  claim 9 , wherein the slide is a stainless steel tape and/or a glass slide. 
     
     
         11 . The film of  claim 10 , further comprising a layer of Chromium (Cr) on the glass slide, and wherein the layer of Chromium acts as an adhesion layer before deposition of the gold layer, which enhances the stability of the layer of gold (or film) on the substrate. 
     
     
         12 . The film of  claim 5 , wherein the plurality of alternating layers of poly(allylamine hydrochloride) (PAH) and sodium silicate solution onto the layer of gold by a layer-by-layer deposition process, spraying coating, dipping coating, and/or chemical deposition. 
     
     
         13 . A calcinated silicate film, comprising:
 a layer by layer deposition of poly(allylamine hydrochloride) PAH and sodium silicate (water glass) on a gold surface.   
     
     
         14 . A method of forming a calcinated silicate film comprising:
 placing a sublayer onto a stainless steel tape and/or glass slide;   alternately depositing poly(allylamine hydrochloride) PAH and a sodium silicate solution onto a surface of the sublayer; and   calcinating the alternately deposited layers of PAH and sodium silicate solution.   
     
     
         15 . The method of  claim 14 , wherein the sublayer is gold (Au), platinum (Pt), silver (Ag), aluminum (Al) and/or stainless steel. 
     
     
         16 . The method of  claim 15 , wherein the sublayer is a thin layer of gold. 
     
     
         17 . The method of  claim 14 , wherein the PAH has a concentration of approximately 1 mg/mL with a pH of approximately 8.0, and the sodium silicate solution has a concentration of 22 mg/mL, with a pH of approximately 9.5. 
     
     
         18 . The method of  claim 16 , further comprising immersing the gold layer (or substrate) in a 5 mM 3-MPA ethanol solution overnight, followed by extensive rinsing with ethanol and DI water. 
     
     
         19 . The method of  claim 14 , wherein the PAH and sodium silicate solution are alternately deposited by spray bottles with a rinse with DI water between each spray. 
     
     
         20 . The method of  claim 16 , further comprising alternately depositing approximately 15 to 20 layers of PAH and sodium silicate solution onto the thin gold layer. 
     
     
         21 . The method of  claim 20 , wherein the PAH and sodium silicate solution has a thickness of approximately 2-50 nm. 
     
     
         22 . The method of  claim 14 , wherein the step of calcinating the alternately deposited layers of PAH and sodium silicate solution is performed in a furnace by heating to 450° C. at a rate of 17° C. per min and brought to room temperature after 4 hours. 
     
     
         23 . The method of  claim 16 , wherein the step of depositing the poly(allylamine hydrochloride) (PAH) and sodium silicate (water glass) on the gold-covered stainless steel tape (SST) is a layer by layer deposition (LbL). 
     
     
         24 . The method of  claim 14 , wherein the thickness of a glassified layer is controlled at 1 nm resolution. 
     
     
         25 . The method of  claim 14 , wherein a 15-layer film after calcination has an average thickness of approximately 20 nm. 
     
     
         26 . The method of  claim 14 , further comprising controlling the thickness and surface properties of the film to enable effective ionization of a variety of target molecules. 
     
     
         27 . The method of  claim 14 , further comprising introducing a tailoring surface property to the calcinated nanofilm by silylation chemistry, desalting, sample preconcentration and/or selective capture of analytes. 
     
     
         28 . The method of  claim 14 , further comprising performing matrix-free laser desorption ionization mass spectrometry (LDI-MS) and/or surface-assisted laser desorption ionization (SALDI-MS) analysis of biomolecules with the calcinated silicate film. 
     
     
         29 . The method of  claim 14 , further comprising integrating the calcinated silicate film with microfluidic, microarray chip, and/or optical methods. 
     
     
         30 . The method of  claim 14 , further comprising integrating SPR techniques (including SPR spectroscopy and SPR imaging) with mass spectrometry (including MALDI or SALDI-MS) on the calcinated silicate film. 
     
     
         31 . The method of  claim 30 , wherein the SPR technique and mass spectrometry (MS) operate on an orthogonal detection principle, and is performed for different analytical purposes. 
     
     
         32 . The method of  claim 30 , wherein a combination of SPR sensor with SALDI-MS facilitates the analysis of biomolecular recognition and interaction on SPR sensor chips. 
     
     
         33 . The method of  claim 30 , wherein SALDI-MS is used for direct identification of retained biomolecules on the calcinated silicate film. 
     
     
         34 . The method of  claim 30 , further comprising combining a microarray technique with SPR imaging and SALDI-MS to promote high throughput analysis, and providing not only quantitative but also identification information for the target molecules.