10Translation of the findings in basic science and clinical research into routine practice is hampered 11 by large variations in human phenotype. Developments in genotyping and phenotyping, such as 12 proteomics and lipidomics, are beginning to address these limitations. In this work, we developed 13 a new methodology for rapid, label-free molecular phenotyping of biological fluids (e.g., blood) 14 by exploiting the recent advances in fast and highly efficient multidimensional inverse Laplace 15 decomposition technique. We demonstrated that using two-dimensional T1-T2 correlational 16 spectroscopy on a single drop of blood (<5 μL), highly time-and patient-specific ´molecular 17 fingerprint´ can be obtained in minutes. Machine learning techniques were introduced to 18 transform the NMR correlational map into user-friendly information for point-of-care disease 19 diagnostic. The clinical utilities of this technique were demonstrated through the direct analysis 20 of human whole blood in various physiological (e.g., oxygenated/deoxygenated states) and 21 pathological (e.g., blood oxidation, hemoglobinopathies) conditions. (145 words) 22 23 Keywords: rapid phenotyping of blood, 2D NMR correlational spectroscopy, machine learning, 24 disease diagnostic and monitoring.
Introduction
1High-resolution nuclear magnetic resonance (NMR) spectroscopy is a powerful and attractive 2 technique in biochemistry (e.g., for structural protein analysis 1 , characterizing metabolomics 3 responses in biological samples 2-4 ) and inorganic chemistry 5 . However, high-resolution NMR 4 systems are large, expensive and incompatible with in-situ or portable applications. There is an 5 increasing demand for low field portable NMR system for use in food sciences 6 , oil-gas 6 exploration 7 , and point of care clinical testing [8][9][10] . In high field NMR, biochemical information is 7 typically detected and encoded in the frequency domain ("chemical shift"), in which the spectral 8 resolution scale with respect to the external magnetic field. This reduces its portability and limit 9 its downstream application in a large scale manner.
10However, biochemical and biophysical information (e.g., molecular rotational, diffusional 11 motion) can also be encoded in the relaxation times frame, namely the longitudinal (T1) and 12 transverse (T2) using a portable low field NMR system. In addition, molecular information in the 13 time-domain can be inversely decoded with the availability of fast and reliable Laplace inversion 14 algorithm 7,11 . This can provide parallel information that is not available in the traditional NMR 15 frequency domain based spectra.
16In recent years, significant advances in NMR system miniaturization 8,12-14 (e.g., electronic 17 console 12,13,15,16 , radio-frequency probe 9,10,17-19 , microfluidic-based chip 20,21 ) utilizing small foot-18 print permanent magnetic (<1 Tesla) for one-dimensional NMR relaxometry on water-proton 19 (e.g., spin-spin relaxation (T2-relaxation)) have been widely applied for point-of-care medi...