NMR systems for in vivo detection of analytes
This invention relates generally to NMR systems for in vivo detection of analytes. More particularly, in certain embodiments, the invention relates to systems in which superparamagnetic nanoparticles are exposed to a magnetic field and radio frequency (RF) excitation at or near the Larmor frequency, such that the aggregation and/or disaggregation of the nanoparticles caused by the presence and/or concentration of a given analyte in a biological fluid is detected in vivo from a monitored RF echo response.
1. A method for assessing the presence or concentration of an analyte contained in a body fluid of a mammal in-vivo using a nuclear magnetic resonance system, the method comprising the steps of:
(a) implanting partially or completely a sensor of the nuclear magnetic resonance system within the mammal's body, the sensor comprising structure defining a sample volume and a port, the sample volume containing magnetic particles, and the port allowing the analyte to enter the sample volume and preventing, partly or completely, the magnetic particles from leaving the sample volume, the extent of aggregation of the magnetic particles being indicative of the presence or concentration of the analyte in the sample volume;
(b) calculating a Larmor frequency within the sample volume or a portion thereof;
(c) applying a probe radiofrequency pulse sequence at or near the Larmor frequency to part or all of the sample volume from a reader positioned outside the mammal's body in the presence of a magnetic field to induce echo radiofrequency signals; and
(d) assessing the presence or concentration of the analyte from the echo radiofrequency signals.
2. The method of claim 1 , wherein the magnetic particles are paramagnetic.
3. The method of claim 1 , wherein the magnetic particles are superparamagnetic.
4. The method of claim 1 , wherein the magnetic particles are functionalized with one or more binding moieties that bind to one or more target analytes.
5. The method of claim 4 , wherein at least one of the one or more binding moieties comprises at least one of an amino group, a carboxyl group, a sulfhydryl group, an amine group, an imine group, an epoxy group, a hydroxyl group, a thiol group, an acrylate group, or an isocyano group.
6. The method of claim 4 , wherein at least one of the one or more binding moieties comprises at least one of an amino acid, a nucleic acid, an oligonucleotide, a therapeutic agent, a metabolite of a therapeutic agent, a peptide, a polypeptide, a protein, a carbohydrate, a polysaccharide, a virus, or a bacteria.
7. The method of claim 1 , wherein at least one of the magnetic particles comprises a polymer matrix coating.
8. The method of claim 1 , wherein the magnetic particles have an average particle size of between about 1 nm and 5 μm.
9. The method of claim 1 , wherein the sensor comprises a magnetic field detector for detecting the strengths of a magnetic field within or adjacent to the sample volume, and a transmitter for transmitting a signal indicative of the strength of the magnetic field; and wherein the reader comprises a receiver for receiving the signal indicative of the strength of the magnetic field.
10. The method of claim 1 , wherein the sensor comprises a transmitting antenna for transmission of data received from a logic circuitry to the reader.
11. The method of claim 10 , wherein the logic circuitry is used to calculate the Larmor frequency of water within the sample volume or a portion thereof.
12. The method of claim 1 , wherein the sensor comprises a radiofrequency identification (RFID) emitter for emitting radiofrequency signals.
13. The method of claim 1 , wherein the sensor comprises a radiofrequency coil for applying the radiofrequency pulse sequence to the sample volume in the presence of the magnetic field.
14. The method of claim 13 , wherein the radiofrequency coil acts as a sensing radio frequency coil and an excitation radiofrequency coil.
15. The method of claim 1 , wherein the reader comprises a radiofrequency coil for applying the radiofrequency pulse sequence to the sample volume in the presence of the magnetic field and a logic circuitry for calculating the Larmor frequency of water within the sample volume or a portion thereof.
16. The method of claim 15 , wherein the radiofrequency coil acts as a sensing radio frequency coil and an excitation radiofrequency coil.
17. The method of claim 15 , further comprising a logic circuitry for determining a nuclear magnetic resonance parameter influenced by the analyte within the sample volume.
18. The method of claim 17 , wherein the nuclear magnetic resonance parameter is T 2 .