Fluorescent imaging agents

1. A cyclic intramolecularly quenched imaging agent comprising:

a) a first fluorophore chemically linked, directly or indirectly, to the C-terminus of a first cleavable oligopeptide and chemically linked, directly or indirectly, to the N-terminus of a second, optionally cleavable, oligopeptide;

b) a second fluorophore chemically linked, directly or indirectly, to the N-terminus of the first cleavable oligopeptide and chemically linked directly or indirectly, to the C-terminus of the second, optionally cleavable oligopeptide; wherein one of the fluorophores quenches the other fluorophore; and

c) optionally, at least one biological modifier chemically linked to the first or second oligopeptide or fluorophore.

2. The agent of claim 1 , represented by Formula IV:

wherein

ECO, independently, for each occurrence, is an enzymatically cleavable oligopeptide;

G is L-F-L;

F, independently, for each occurrence, is a fluorophore;

L, independently, for each occurrence, is a linker moiety or a bond;

M is a biological modifier;

K is L-N;

N is a non-fluorescent reporter;

n is an integer from 0 to 3; and

m is an integer from 0 to 3.

3. The agent of claim 1 , wherein F is a far-red or a near-infrared fluorophore.

4. The agent of claim 3 , wherein the fluorophore is a carbocyanine fluorophore.

5. The agent of claim 3 , wherein the fluorophore is an indocyanine fluorophore.

6. The agent of claim 1 , wherein the fluorophore is represented by the following general Formula VII:

or a salt thereof, wherein:

X is independently, for each occurrence, selected from the group consisting of C(CH 2 Y 1 )(CH 2 Y 2 ), O, S, and Se;

Y 1 and Y 2 are independently selected from the group consisting of H and a C 1 -C 20 aliphatic group optionally substituted with —OR*, N(R*) 2 or —SR*, wherein R* is H or alkyl;

W represents a benzo-condensed, a naphtho-condensed or a pyrido-condensed ring;

R 1 is selected from the group consisting of (CH 2 ) x CH 3 , (CH 2 ) n SO 3 − and (CH 2 ) n SO 3 H, wherein x is an integer selected from 0 to 6 and n is an integer selected from 2 to 6;

R 2 and R 3 independently are selected, for each occurrence, from the group consisting of H, carboxylate, carboxylic acid, carboxylic ester, amine, amide, sulfonamide, hydroxyl, alkoxyl, a sulphonic acid moiety and a sulphonate moiety;

R 4 is selected from the group consisting of (CH 2 ) x CH 3 , (CH 2 ) n SO 3 − and (CH 2 ) n SO 3 H, wherein x is an integer selected from 0 to 6 and n is an integer selected from 2 to 6; and

Q is selected from a group consisting of a heteroaryl ring substituted with a carboxyl group or 6-membered heteroaryl ring substituted with a carbonyl group.

7. The agent of claim 1 , wherein the fluorophore is represented by the general Formula VIII:

or a salt thereof, wherein:

X 1 and X 2 are independently selected, for each occurrence from the group consisting of C(CH 2 K 1 )(CH 2 K 2 ), O, S and Se;

K 1 and K 2 are independently selected from the group consisting of H, a C 1 -C 20 aliphatic group optionally substituted with —OR*, N(R*) 2 or —SR*; or K 1 and K 2 together form part of a substituted or unsubstituted carbocyclic, or heterocyclic ring;

Y 1 and Y 2 are each independently a benzo-condensed ring, a naphtha-condensed ring or a pyrido-condensed ring;

n 1 is 1, 2, or 3;

R 2 , R 11 and R 12 are independently selected from the group consisting of H, F, Br, Cl, C 1 -C 6 alkyl, C 1 -C 6 alkoxy, aryloxy, a nitrogen-containing heterocyclic ring, a nitrogen-containing heteroaromatic ring, a sulfonate, an iminium ion, or any two adjacent R 12 and R 11 substituents or R 2 and R 11 substituents, when taken in combination, form a 4-, 5-, or 6-membered substituted or unsubstituted carbocyclic ring, substituted or unsubstituted non-aromatic carbocyclic ring or a substituted or unsubstituted carbocyclic aryl ring, wherein the carbocyclic rings are each independently optionally substituted one or more times by C 1 -C 6 alkyl, halogen, or OR* or SR*;

R 1 and R 13 are (CH 2 ) x CH 3 , when x is an integer selected from 0 to 6; or R 1 and R 13 are independently (CH 2 )—SO 3 − or (CH 2 )—SO 3 H when n is an integer selected from 2 to 6;

R 3 , R 4 and R 5 are independently selected from the group consisting of H, carboxylate, carboxylic acid, carboxylic ester, amine, amide, sulfonamide, hydroxyl, alkoxyl, a sulphonic acid moiety and a sulphonate moiety;

Q is absent, or is selected from a carbonyl moiety or a substituted or unsubstituted C 1 -C 6 alkyl group, wherein 0-2 of the methylene groups of the alkyl group can optionally be replaced by NH, O or S, or a substituted or unsubstituted C 1 -C 6 carbocyclic, non-aromatic carbocyclic, heterocyclic or non-aromatic heterocyclic ring wherein the heterocyclic rings contains 1-2 heteroatoms;

R 6 is selected from the group consisting of H, a substituted or unsubstituted C 20 aliphatic group, a substituted or unsubstituted aryl, a substituted or unsubstituted alkylaryl, wherein R 6 is optionally substituted with halogen, OR*, N(R*) 2 or SR*, when Q is absent, a carbonyl group, a substituted or unsubstituted C 1 -C 6 alkyl group, wherein 0-2 of the methylene groups of the alkyl group are replaced by NH, O or S, or a substituted or unsubstituted C 1 -C 6 carbocyclic, non-aromatic carbocyclic, heterocyclic or non-aromatic heterocyclic ring wherein the heterocyclic rings contains 1-2 heteroatoms; or

R 6 is H, when Q is a carbonyl; and

R 7 is selected from the group consisting of H, a substituted or unsubstituted C 1 -C 20 aliphatic group, a substituted or unsubstituted aryl, a substituted or unsubstituted alkylaryl, wherein R 7 is optionally substituted with halogen, OR*, N(R*) 2 or SR*; or

R 6 and R 7 , taken together form a 4-, 5-, 6- or 7-membered heterocyclic or non-aromatic heterocyclic ring optionally substituted with halogen, OR*, N(R*) 2 or SR*; or

NR 6 , Q and CHR 7 together form a substituted or unsubstituted or heterocyclic or non-aromatic heterocyclic ring system wherein the rings contain 1 or 2 heteroatoms, wherein rings are optionally substituted with —OR*, N(R*) 2 or —SR*; and

W is absent or is a group selected from the group consisting of —SO 2 NR 6 -Q-CHR 7 —, —O—, —COO—, and —CONH—;

h=0-70; k=0 or 1; d=0-12; m=0-12; p=0-12;

Z is a N, O or S nucleophile functionality moiety or is, or contains a functionality capable of reacting with N, O or S nucleophiles; and

each R* is independently H or C 1-20 alkyl.

8. The agent of claim 2 , wherein L comprises a moiety selected from the group consisting of an amido bond, amino-polyethylene glycol-carboxylic acid, amino-polyethylene glycol azide, diaminoPEG, cysteic acid, glutamic acid, aminocaproic acid, ethylenediamine, propylenediamine, spermidine, spermine, hexanediamine, and a diamine-amino acid.

9. The agent of claim 1 , wherein the biological modifier has a molecular weight from about 10 kDa to about 35 kDa.

10. The agent of claim 1 , wherein the biological modifier is selected from the group consisting of polyethylene glycol, methoxypolyethylene glycol, branched polypropylene glycol, polypropylene glycol, a graft copolymer of poly-lysine and methoxypolyethyleneglycol, a fatty acid, a lipid, a phospholipid, an amino acid, a peptide, a carbohydrate, a dextran, a sulfonate and a polysulfonate, glutamic acid, cysteic acid, naphthylalanine, phenylalanine, diphenylpropylamine, 4,4-diphenylcyclohexanol, glucosamine, mannosamine, galactosamine, arginine, lysine, homolysine and leucine.

11. The agent of claim 1 , wherein the biological modifier is covalently linked to the enzymatically cleavable peptide at a position that is not between two amino acids covalently linked to a fluorophore or a quencher.

12. The agent of claim 1 , wherein the biological modifier is covalently linked to the enzymatically cleavable oligopeptide through an acyl moiety.

13. The agent of claim 1 , wherein the biological modifier is covalently linked to the enzymatically cleavable oligopeptide by a 3+2 cycloaddition reaction between an azide moiety chemically linked to the biological modifier and an alkyne moiety chemically linked to an N-terminus of the enzymatically cleavable oligopeptide or wherein the biological modifier is chemically linked to the enzymatically cleavable oligopeptide by a 3+2 cycloaddition reaction between an alkyne moiety chemically linked to the biological modifier and an azide moiety covalently linked to the N-terminus of the enzymatically cleavable oligopeptide.

14. The agent of claim 1 , wherein the biological modifier is covalently linked to the enzymatically cleavable oligopeptide by an amide coupling reaction or a thiol coupling reaction between the biological modifier and the C-terminus of the enzymatically cleavable oligopeptide.

15. The agent of claim 1 , wherein the enzymatically cleavable oligopeptide is cleavable by at least one enzyme selected from the group consisting of a cathepsin, a matrix metalloprotease, a peptidase, a carboxypeptidase, a glycosidase, a lipase, a phospholipase, a phosphatase, a phosphodiesterase, a sulfatase, a reductase, and a bacterial enzyme.

16. The agent of claim 2 , wherein N is a radioisotopic metal selected from the group consisting of copper, gallium, indium, technetium, yttrium, and lutetium.

17. The agent of claim 2 , wherein N is a therapeutic radiopharmaceutical.

18. An intramolecularly-quenched imaging agent represented by Formula V:

wherein

X 1 * independently, at each occurrence, is X-L-;

X is an amino acid residue;

L is a linker moiety or a bond; and

F, independently, at each occurrence, is a fluorophore.

19. An intramolecularly-quenched imaging agent represented by Formula VI:

wherein

X 1 *, independently, at each occurrence, is X-L-;

X is an amino acid residue;

L is a linker moiety or a bond;

F, independently, at each occurrence, is a fluorophore.

20. The agent of claim 18 , wherein the agent has a molecular weight from about 2 kDa to 60 kDa.