Small molecule dye for molecular imaging and photothermal therapy
Disclosed is a small molecule dye for use in imaging in the near-infrared window, namely between 1000 nm-1700 nm wavelength. The present dyes are also useful for photoacoustic imaging and photothermal therapy. The dyes have a structure of a D-A-D (donor-acceptor-donor) fluorescent compound core and side chains rendering the compounds water soluble and easily conjugated to hydrophilic polymers and/or targeting ligands. Further disclosed is compound, CH1055 that can be PEGylated, conjugated to a targeting ligand, or conjugated to taurine. Key steps utilized to assemble the core structure of the target included a cross-Suzuki coupling reaction, iron reduction and N-thionylaniline induced ring closure. Four carboxylic acid groups were introduced into the donor-acceptor-donor (D-A-D) type fluorescent compound to impart a certain aqueous solubility and to allow facile conjugation to targeting ligands.
1. A near-infrared-II fluorophore represented by
wherein:
A and B are independently selected from the group consisting of
and
X and Y are each independently selected from the group consisting of S and Se;
Z is independently one of N and P; and
R1, R2, R3, and R4 are each independently of the formula -alkyl-linker, wherein “alkyl” is —(CH 2 )n-, further wherein n is between 1 and 14, inclusive, and further wherein “linker” is selected from the group consisting of sulfonic, phosphonic, carboxyl, hydroxyl, NHS-ester, maleimide, amine, —SH, sulfonic acid and hydrazide.
2. The fluorophore of claim 1 , wherein R1, R2, R3, and R4 are each lower alkyl acid.
3. The fluorophore of claim 1 having the structure
4. A near-infrared-II fluorophore represented by the following:
wherein
A and B are independently selected from the group consisting of
and
X and Y are each independently selected from the group consisting of S and Se;
Z is independently one of N and P; and
R1, R2, R3, and R4 are each one of
(i) -alkyl-polymer, wherein “alkyl” is —(CH 2 ) n —, further wherein n is between one of 1 and 14, inclusive, and further wherein “polymer” is a polymer of the group consisting of ethylene glycol (EG), methacrylic acid (MA), 2-hydroxyethyl methacrylate (HEMA), ethyl acrylate (EA), 1-vinyl-2-pyrrolidinone (VP), propenoic acid 2-methyl ester (PAM), monomethacryloyloxyethyl phthalate, (EMP) and ammonium sulphatoethyl methacrylate (SEM), having the formula -alkyl-polymer;
(ii) a radical consisting of the group of —(CH 2 ) 2 C(═O)—NH(CH 2 ) 2 SO 3 H—NH(CH 2 )SO 3 H and
(iii) R1, R2, and R3 are each lower alkyl acid, and R4 is of the formula
wherein “lower alkyl” has a structure of a 6 carbon chain and “peptide” has a structure of an Fv fragment, a single-chain Fv, a diabody, or an affibody molecule.
5. The fluorophore of claim 4 , wherein R1, R2, R3, and R4 are each —(CH 2 ) 2 C(═O)—NH—(CH 2 ) 2 SO 3 H.
6. The fluorophore of claim 4 , wherein R4 “peptide” is an antibody molecule.
7. The fluorophore compound d of claim 4 , wherein R4 “peptide” is an affibody molecule.
8. The fluorophore of claim 7 , wherein “peptide” has the sequence of SEQ ID NO: 1.
9. The fluorophore of claim 4 having a peak fluorescent emission at about 1100 nm.
10. A near-infrared-II compound represented by the following:
wherein:
X and Y are independently selected from the group consisting of: S, and Se;
Z is N or P; and
R1, R2, R3, and R4 are each independently one of
wherein n is an integer ranging from 1 to 100,
and
11. A complex comprising a compound as recited in claim 10 , wherein Formula II is defined by R1, R2, R3, and R4 (b)
or (c)
said complex further comprising at least one serum protein selected from the group consisting of: human serum albumin, and bovine serum.
12. The of claim 10 , wherein R1, R2, R3, and R4 are each
13. A method for imaging a biological structure in a tissue, said method using an NIR-II dye and comprising steps of:
(a) introducing the dye into a tissue and allowing the dye to bind to a structure within the tissue;
(b) exposing the dye, bound to the biological structure, to NIR light;
(c) detecting NIR-II light emitted from the dye as a result of the NIR light provided in step (b); and
(d) constructing an image from the emitted light in step (c) using a detector sensitive to NIR-II light,
wherein said dye has the structure
wherein
X and Y are each independently selected from S and Se;
Z is N or P; and
R1, R2, R3, and R4 are each independently of the formula “-benzyl-alkyl-linker,” wherein alkyl is —(CH 2 ) n — further wherein n is between 1 and 4, inclusive, and “linker” is selected from the group consisting of carboxyl, hydroxyl, NH-ester, maleimide, amine, —SH, sulfonic acid or hydrazide.
14. A method of claim 13 wherein R1, R2, R3, and R4 are each one of the formula
wherein W is —(CH 2 ) m — where m is 1 to 10;
and
15. The method of claim 13 , wherein the NIR light is provided by an excitation wavelength between 650 and 1000 nm from a laser.
16. The method of claim 13 , wherein the biological structure is within a living subject and said NIR-II dye is linked to an affibody molecule.
17. The method of claim 13 , wherein the biological structure is a blood vessel, tumor or a lymph node.
18. The method of claim 13 , comprising a step of conjugating the of Formula II to a targeting ligand.
19. The method of claim 18 , wherein the targeting ligand is an affibody molecule.
20. The method of claim 19 , wherein the targeting ligand is specific to an EGFR.
21. The method of claim 13 , wherein the biological structure is greater than 3 mm below an external surface of a subject.
22. The method of claim 13 , wherein the biological structure is in a subject being evaluated for head and neck cancer, melanoma, or breast cancer.
23. The method of claim 13 , wherein the image is constructed with an InGaAs camera.
24. The method of claim 13 , wherein constructing the image comprises using a longpass filter at wavelength between 1000 and 1400 nm.
25. The method of claim 13 , wherein the dye is injected intravenously in a living mammal.
26. The method of claim 25 wherein blood vessels are imaged with dye circulating through said mammal.
27. The method of claim 13 , wherein the dye is further used for image-guided tumor surgery.
28. A method of imaging a subject comprising administering a compound having the structure
wherein the sequence Ac-Cys-Val-Asp . . . represents an affibody sequence.
29. The method of claim 28 further comprising a step of removing cells bound to the compound, while imaging the structure.
30. The method of claim 28 further comprising a step of applying photothermal heating of tissue which has taken up the compound and is thereafter irradiated at a site of interest by a near-infrared light source.
31. The method of claim 28 further comprising a step of applying acoustic emission for NIR photoacoustic imaging.