Bacterial imaging agents and methods of using same

1. A bacterium targeting agent having an absorption and emission maximum between about 600 nm and about 900 nm, wherein the agent is represented by formula (I):

or a salt thereof, wherein:

Z is a bacterium targeting moiety comprising:

(a) a positively charged moiety having the formula:

(b) an aliphatic, aromatic or heteroaromatic moiety, each of which is optionally substituted; and

(c) one or more anions as needed to provide a charge-neutral compound;

L is, independently for each occurrence, a linker moiety comprising a diradical of a moiety selected from the group consisting of glycine, alanine, β-alanine, —NH—(CH 2 ) n —C(═O)— where n=1-8, 4-aminomethylbenzoic acid, cysteic acid, glutamic acid, amino-polyethylene glycol-carboxylic acid, amino-polyethylene glycol amine, ethylenediamine, propylenediamine, spermidine, spermine, hexanediamine, and a diamine-amino acid;

Q is selected from a group consisting of substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, C 1 -C 18 alkyl, alkenyl, alkynyl, alkoxy, or thioalkyl group, or is absent;

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

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 C 1 -C 20 aliphatic group optionally substituted with L-M;

M, independently for each occurrence, is hydrogen or a chemical modifying moiety.

2. A bacterium targeting agent of formula (IV):

F-(L) n -(Z) m   (IV)

or a salt thereof, wherein:

n=1-8

m=1, 2, 3, or 4

F is a near infrared fluorochrome having an absorption and emission maximum between about 600 nm and about 900 nm;

L is a linker comprising a diradical of a moiety selected from the group consisting of glycine, alanine, β-alanine, —NH—(CH 2 ) n —C(═O)— where n=1-8, 4-aminomethylbenzoic acid, cysteic acid, glutamic acid, amino-polyethylene glycol-carboxylic acid, amino-polyethylene glycol amine, ethylenediamine, propylenediamine, spermidine, spermine, hexanediamine, and a diamine-amino acid; and

Z represents independently for each occurrence a bacterium targeting moiety comprising:

(a) a positively charged moiety having the formula:

(b) an aliphatic, aromatic, heteroaromatic, or PEG moiety, each of which is optionally substituted; and

(c) one or more anions as needed to provide a charge-neutral compound.

3. The agent of claim 1 , wherein M is selected from the group consisting of a hydrogen, alcohol, sulfonate, polysulfonate, cysteic acid, sulfonamide, sulfoxide, sulfone, carboxylate, ketone, phosphonate, phosphate; iminodiacetate, ethylenediamine tetraacetic acid, diethylenetriamine pentaacetic acid, tetraazacyclododecane tetraacetic acid, an amino acid, polyamino acid, oligo ethylene glycol, polyethylene glycol, amine, quaternary ammonium ion, sugar, glucosamine, galactosamine, mannosamine, polyethylene glycol (PEG), alkoxy polyethylene glycol, branched polypropylene glycol, polypropylene glycol, a graft copolymer of poly-lysine and methoxypolyethyleneglycol, peptide, lipid, fatty acid, palmitate, phospholipid, phospholipid-PEG conjugate, carbohydrate, iron oxide nanoparticle, naphthylalanine, phenylalanine, 3,3-diphenylpropylamine, taurine, phosphonate, phosphate, carboxylate and polycarboxylate.

4. The agent of 1 , wherein the chemical modifier(s) M reduce the nonspecific cell membrane permeability of the agent.

5. One of the following agents or a salt thereof:

6. A pharmaceutical composition suitable for administration to a subject, comprising an agent of claim 1 and a pharmaceutically acceptable excipient.

7. A method of imaging bacterium infection in a subject, comprising:

(a) administering an agent of claim 1 to a subject;

(b) detecting the presence of the agent; and

(c) producing an image representative of bacterium infection, thereby imaging bacterium infection.

8. The agent of claim 1 , wherein the bacterium targeting agent has an affinity for bacterial cell surfaces; and wherein the bacterium targeting agent's affinity for bacterial cell surfaces is greater than the bacterium targeting agent's affinity for healthy mammalian cell surfaces.

9. The agent of claim 2 , wherein the bacterium targeting agent has an affinity for bacterial cell surfaces; and wherein the bacterium targeting agent's affinity for bacterial cell surfaces is greater than the bacterium targeting agent's affinity for healthy mammalian cell surfaces.

10. A bacterium targeting agent that is a compound represented by Formula VII:

or a salt thereof, wherein:

X is one of the following:

(a) —(C 1 -C 6 alkylene)-C(O)N(R 5 )—Y-(substituted heterocyclyl containing one quaternary ring nitrogen atom)-A;

(b) —(C 1 -C 6 alkylene)-C(O)N(R 5 )—Y-(substituted heterocyclyl containing two quaternary ring nitrogen atoms)-(A) 2 ; or

n is 1, 2, 3, or 4;

A is a monvalent anion or absent;

Y is one of the following:

(a) ψ-alkylene-C(O)N(R 5 )-arylene-alkylene-; or

(b) ψ-heteroalkylene-C(O)N(R 5 )-alkylene-C(O)N(R 5 )-arylene-alkylene-;

ψ is a bond to the amide nitrogen atom;

Z is

R 1 and R 3 each represent independently alkyl or alkylene-SO 3 − M + ;

R 2 and R 4 each represent independently for each occurrence methyl, ethyl, or propyl;

R 5 represents independently for each occurrence hydrogen, methyl, ethyl, or propyl; and

M is a monovalent cation or absent.

11. The agent of claim 10 , wherein X is —(C 1 -C 6 alkylene)-C(O)N(R 5 )—Y-(substituted heterocyclyl containing two quaternary ring nitrogen atoms)-(A) 2 .

12. The agent of claim 10 , wherein the substituted heterocyclyl containing two quaternary ring nitrogen atoms is one of the following:

13. The agent of claim 10 , wherein Y is ψ-CH 2 —C(O)N(H)-phenyl-(C 1 -C 4 )alkylene-.

14. The agent of claim 10 , wherein Y is one of the following:

15. The agent of claim 10 , wherein R 1 is alkyl.

16. The agent of claim 10 , wherein R 3 is alkylene-SO 3 − M + .

17. The agent of claim 1 , wherein the diamine-amino acid is selected from the group consisting of homolysine, lysine, ornithine, diaminobutyric acid and diaminopropionic acid, succinic acid, glutaric acid, suberic acid, adipic acid, amide, triazole, urea and thiourea.

18. The agent of claim 2 , wherein the diamine-amino acid is selected from the group consisting of homolysine, lysine, ornithine, diaminobutyric acid and diaminopropionic acid, succinic acid, glutaric acid, suberic acid, adipic acid, amide, triazole, urea and thiourea.