NMR device for detection of analytes
This invention relates generally to detection devices having one or more small wells each surrounded by, or in close proximity to, an NMR micro coil, each well containing a liquid sample with magnetic nanoparticles that self-assemble or disperse in the presence of a target analyte, thereby altering the measured NMR properties of the liquid sample. The device may be used, for example, as a portable unit for point of care diagnosis and/or field use, or the device may be implanted for continuous or intermittent monitoring of one or more biological species of interest in a patient.
1. A device for measuring the NMR relaxation rate of protons in a blood sample, the device comprising:
(a) a reader configured to receive a signal from the blood sample, the reader comprising (i) one or more permanent magnets defining a magnetic field, (ii) an RF excitation coil for transmitting an RF excitation to the blood sample, (iii) an RF coil configured to detect an NMR relaxation response produced by exposing the blood sample to the magnetic field and the RF excitation, (iv) an electrical element in communication with the RF coil, the electrical element configured to amplify, rectify, transmit, and/or digitize the signal corresponding to the NMR relaxation response, and (v) a display for indicating the NMR relaxation rate of the protons in the blood sample;
(b) a support defining a well holding the blood sample comprising magnetic particles and having the RF coil disposed about the well, the RF coil configured to detect an NMR relaxation response produced by exposing the blood sample to a bias magnetic field created using the one or more permanent magnets and the RF excitation; and
(c) a removable cartridge sized for convenient insertion into and removal from the device and having a compartment comprising one or more populations of magnetic particles.
2. The device of claim 1 , wherein the well and the RF coil are configured to provide a filling factor of at least about 0.1.
3. The device of claim 1 , wherein the well has a volume of less than about 300 μL.
4. The device of claim 1 , wherein the well and the RF coil are configured such that the volume circumscribed by the RF coil is less than about 300 μL.
5. The device of claim 1 , wherein the RF coil has a characteristic dimension from about 10 μm to about 1000 μm.
6. The device of claim 1 , further comprising a tube for holding the blood sample, the tube having a varying cross section.
7. The device of claim 1 , wherein the bias magnetic field has a strength of from about 0.45 Tesla to about 7 Tesla.
8. The device of claim 1 , further comprising a display for indicating a physical property of the blood sample.
9. The device of claim 8 , wherein the physical property is the viscosity of the blood sample.
10. A method for measuring the NMR relaxation rate of protons in a blood sample, the method comprising:
(a) placing the blood sample in a device of claim 1 , the device comprising a support defining a well holding a blood sample comprising magnetic particles and having an RF coil disposed about the well, the RF coil configured to detect an NMR relaxation response produced by exposing the blood sample to a bias magnetic field created using one or more magnets and an RF excitation;
(b) contacting the blood sample with the magnetic particles in the presence of the bias magnetic field;
(c) exposing the sample to an RF excitation; and
(d) following step (c), detecting an NMR relaxation response produced by the protons in the blood sample.
11. The method of claim 10 , further comprising, on the basis of step (d), measuring a physical property of the blood sample.
12. The method of claim 11 , wherein the physical property is the viscosity of the blood sample.
13. The method of claim 10 , wherein the well and the RF coil are configured to provide a filling factor of at least about 0.1.
14. The method of claim 10 , wherein the well has a volume of less than about 300 μL.
15. The method of claim 10 , wherein the well and the RF coil are configured such that the volume circumscribed by the RF coil is less than about 300 μL.
16. The method of claim 10 , wherein the RF coil has a characteristic dimension from about 10 μm to about 1000 μm.
17. The method of claim 10 , further comprising a tube for holding the liquid sample, the tube having a varying cross section.