Ambient ionization mass spectrometric analysis of human surgical specimens to distinguish renal cell carcinoma from healthy renal tissue.

Touch spray-mass spectrometry (TS-MS) is an ambient ionization technique (ionization of unprocessed samples in the open air) that may find intraoperative applications in quickly identifying the disease state of cancerous tissues and in defining surgical margins. In this study, TS-MS was performed on fresh kidney tissue (∼1-5 cm(3)), within 1 h of resection, from 21 human subjects afflicted by renal cell carcinoma (RCC). The preliminary diagnostic value of TS-MS data taken from freshly resected tissue was evaluated. Principal component analysis (PCA) of the negative ion mode (m/z 700-1000) data provided the separation between RCC (16 samples) and healthy renal tissue (13 samples). Linear discriminant analysis (LDA) on the PCA-compressed data estimated sensitivity (true positive rate) and specificity (true negative rate) of 98 and 95 %, respectively, based on histopathological evaluation. The results indicate that TS-MS might provide rapid diagnostic information in spite of the complexity of unprocessed kidney tissue and the presence of interferences such as urine and blood. Desorption electrospray ionization-MS imaging (DESI-MSI) in the negative ionization mode was performed on the tissue specimens after TS-MS analysis as a reference method. The DESI imaging experiments provided phospholipid profiles (m/z 700-1000) that also separated RCC and healthy tissue in the PCA space, with PCA-LDA sensitivity and specificity of 100 and 89 %, respectively. The TS and DESI loading plots indicated that different ions contributed most to the separation of RCC from healthy renal tissue (m/z 794 [PC 34:1 + Cl](-) and 844 [PC 38:4 + Cl](-) for TS vs. m/z 788 [PS 36:1 - H](-) and 810 [PS 38:4 - H](-) for DESI), while m/z 885 ([PI 38:4 - H](-)) was important in both TS and DESI. The prospect, remaining hurdles, and future work required for translating TS-MS into a method of intraoperative tissue diagnosis are discussed. Graphical abstract Touch spray-mass spectrometry used for lipid profiling of fresh human renal cell carcinoma. Left) Photograph of the touch spray probe pointed at the MS inlet. Right) Average mass spectra of healthy renal tissue (blue) and RCC (red).

Characteristic lipid profiles of canine non-Hodgkin's lymphoma from surgical biopsy tissue sections and fine needle aspirate smears by desorption electrospray ionization--mass spectrometry.

Canine non-Hodgkin's lymphoma (NHL) is a heterogeneous group of cancers representing approximately 15% of all canine cancers. Further, canine NHL mimics human disease in regards to histopathology and clinical behavior and could function as a comparative model. Diagnosis is currently performed by histopathological evaluation of surgical biopsy specimens and fine needle aspirate (FNA) cytology, an alternative and less invasive method for diagnosis. Desorption electrospray ionization - mass spectrometry (DESI-MS) imaging was performed on tissue sections of surgical biopsies and FNA smears. Mass spectra acquired from normal lymph nodes and NHL tumors were explored using multivariate statistics (e.g. principal component analysis). Tissue sections yielded a predicted sensitivity of 100% for normal and 93.1% for tumor. Further, preliminary results suggest B-cell and T-cell lymphoma can be discriminated (CV sensitivity of 95.5% and 85.7%, respectively). Normal and B-cell NHL FNA samples analyzed by DESI produced spectra that were similar to spectra obtained from surgical biopsies. FNA samples were evaluated using a PCA-LDA classification system built using tissue section data, exploring if the chemical information obtained from the different sample types is similar and whether DESI-MS performed on FNA samples is of diagnostic value. FNA prediction rate for normal (85.7%) and B-cell NHL (89.3%) indicated that DESI-MS analysis of FNA, not previously explored, could provide rapid preliminary diagnosis. Certainly, MS provides complementary molecular information to be used in conjunction with histopathology/cytology, potentially improving diagnostic confidence. The methodology outlined here is applicable to canine NHL, further supports canine models of human NHL, and translation to humans is envisioned.

Touch spray mass spectrometry for in situ analysis of complex samples.

Touch spray, a spray-based ambient in situ ionization method, uses a small probe, e.g. a teasing needle to pick up sample and the application of voltage and solvent to cause field-induced droplet emission. Compounds extracted from the microsample are incorporated into the sprayed micro droplets. Performance tests include disease state of tissue, microorganism identification, and therapeutic drug quantitation. Chemical derivatization is performed simultaneously with ionization.

Detection of strep throat causing bacterium directly from medical swabs by touch spray-mass spectrometry.

Strep throat causing Streptococcus pyogenes was detected in vitro and in simulated clinical samples by performing touch spray ionization-mass spectrometry. MS analysis took only seconds to reveal characteristic bacterial and human lipids. Medical swabs were used as the substrate for ambient ionization. This work constitutes the initial step in developing a non-invasive MS-based test for clinical diagnosis of strep throat. It is limited to the single species, S. pyogenes, which is responsible for the vast majority of cases. The method is complementary to and, with further testing, a potential alternative to current methods of point-of-care detection of S. pyogenes.