Nanostructure initiator mass spectrometry NIMS

The ionization methods reported for IMS included MALDI [41,76-80], Secondary Ion Mass Spectrometry (SIMS) [19, 81-86], Matrix-enhanced (ME)-SIMS [87, 88], Desorption Electrospray Ionization (DESI) [89-99], Nanostructure Initiator Mass Spectrometry (NIMS) [100-102], Atmospheric Pressure Infrared MALDI Mass Spectrometry (AP-IR-MALDI-MS) [103], Laser Ablation-inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) [104-106], Laser Desorption Postionization (LDPI) [107], Laser Ablation Electrospray Ionization Mass Spectrometry (LAESI) [108, 109], and Surface-assisted Laser Desorption/ioniza-tion Mass Spectrometry (SALDI) [110-112], Another method was called probe electrospray ionization (PESI) that was used for both liquid solution and the direct sampling on wet samples. 

Patti G, Woo H, Yanes O, Shriver L, Thomas D, Uritboonthai W, Apon J, Steenwyk R, Manchester M, Siuzdak G (2010) Detection of carbohydrates and steroids by cation-enhanced nanostructure-initiator mass spectrometry (NIMS) for biofluid analysis and tissue imaging. Anal Chem 82 121-128. doi 10.1021/ac9014353... 

Siuzdak and coworkers have recently introduced another nanoscale methodology which advances the capabilities of desorption/ionization mass spectrometry, termed nanostructure initiator mass spectrometry (NIMS) [51]. NIMS consists of a nanostructured surface composed of roughly 10-nm pores with initiator materials such as fluorinated siloxanes embedded within the structure. The analyte is adsorbed to the NIMS surface. Subsequent laser irradiation results in a rapid surface heating that causes the initiator to vaporize from the clathrates, which in turn desorbs the analyte [51]. This approach allows the analysis not only of small molecules but also of large molecules, including peptides and proteins, unlike DIOS-MS. The device used for sample preparation via spray deposition, as weU as representative spectra of vitamin D3 and testosterone, are shown in Figure 9.4 [52]. 

Figure 3.11 summarizes such key experimental points. As a first point, we have to choose the appropriate ionization method for the detection of small metabolites, we have alternative choices other than MALDI, such as secondary ion mass spectrometry (SIMS) [15], nanostructure-initiator mass spectrometry (NIMS) [20,21], desorption/ionization on silicon (DIOS) [22], nanoparticle-assisted laser desorptiopn/ ionization (nano-PALDI) [23], and even laser desorption/ionization (LDI) [24,25]. We consider that MALDI is stiU the most versatile method, particularly due to the soft ionization capability of intact analyte. However, other methods each have unique advantages for example, SIMS and nano-PALDI have achieved higher spatial resolution than conventional MALDI-IMS, and above aU, these mentioned alternative methods are all matrix-free methods, and thus can exclude the interruption of the matrix cluster ion. Next, if MALDI is chosen, experimenters should choose a suitable matrix compound, solvent composition, and further matrix application method for their target analyte. All these factors are critical to obtain sufficient sensitivity because they affect efficiency of analyte extraction, condition of cocrystallization, and, above all, analyte-ionization efficiency. In addition, based on the charge state of the analyte molecule, suitable MS polarity (i.e., positive/ negative ion detection mode) should be used in MS measurement. Below, we shall describe the key experimental points for MALDI-IMS applications of representative metabolites. 

Affinity mass spectrometry 9 Atmospheric pressure mass spectrometry 4 Desorption/ionization mechanism 2 Enzymatic activities measurement 6 Mass Spectrometry Imaging (MSI) 5 Mass-spectrometry detection 3 Nanostructure-initiator mass spectrometry (NIMS) 5 Porous silicon based mass spectrometry 9... 

Four of the most commonly used desorption/ionization methods for MSI are secondary ion mass spectrometry (SIMS), desorption electrospray ionization (DESI), matrix-assisted laser desorption/ionization (MALDI), and laser ablation (LA) with post-ionization. Other desorption/ionization approaches such as laser desorption/ionization (LDI) see Chapter 9, (12)), desorption/ionization on silicon (DIOS) (13), electrospray ionization (ESI) (14), and nanostructure-initiator mass spectrometry (NIMS) (15, 16) also have great potential in MSI. Importantly, many mass spectrometers equipped with a MALDI ion source can be used with related ionization processes such as LDI, DIOS, LA, and laser-NIMS. Erequently, a specific ion source arrangement is optimized for a specific mass analyzer for example, MALDI is often interfaced to a time-of-flight (TOF) mass analyzer (described below) although it can also be used with ICR-based instruments. 

Patti, G.J., Shriver, L.P., Wassif, C.A., Woo, H.K., Urithoonthai, W, Apon, J., Manchester, M., Porter, F.D. and Siuzdak, G. (2010) Nanostructure-initiator mass spectrometry (NIMS) imaging of brain cholesterol metaholites in Smith-Lemh-Opitz syndrome. Neuroscience 170, 858-864. 

Woo, H.K., Northen, T.R., Yanes, O., Siuzdak, G. (2008) Nanostructure-initiator mass spectrometry a protocol for preparing and applying NIMS surfaces for high-sensitivity mass analysis. Nature Protocols, 3,1341-1349. 

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