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P800SO3-PEG: a renal clearable bone-targeted fluorophore for theranostic imaging

  • Wang, Haoran
  • Kang, Homan
  • Dinh, Jason
  • Yokomizo, Shinya
  • Stiles, Wesley R.
  • Tully, Molly
  • Cardenas, Kevin
  • Srinivas, Surbhi
  • Ingerick, Jason
  • Ahn, Sung
  • Bao, Kai
  • Choi, Hak Soo
Published Article
Biomaterials Research
Springer (Biomed Central Ltd.)
Publication Date
Oct 01, 2022
DOI: 10.1186/s40824-022-00294-2
PMID: 36183117
PMCID: PMC9526902
PubMed Central
  • Research Article


Background Due to the deep tissue penetration and reduced scattering, NIR-II fluorescence imaging is advantageous over conventional visible and NIR-I fluorescence imaging for the detection of bone growth, metabolism, metastasis, and other bone-related diseases. Methods Bone-targeted heptamethine cyanine fluorophores were synthesized by substituting the meso -carbon with a sulfur atom, resulting in a bathochromic shift and increased fluorescence intensity. The physicochemical, optical, and thermal stability of newly synthesized bone-targeted NIR fluorophores was performed in aqueous solvents. Calcium binding, bone-specific targeting, biodistribution, pharmacokinetics, and 2D and 3D NIR imaging were performed in animal models. Results The newly synthesized S-substituted heptamethine fluorophores demonstrated a high affinity for hydroxyapatite and calcium phosphate, which improved bone-specific targeting with signal-background ratios > 3.5. Particularly, P800SO3-PEG showed minimum nonspecific uptake, and most unbound molecules were excreted into the urinary bladder. Histological analyses demonstrated that P800SO3-PEG remained stable in the bone for over two weeks and was incorporated into bone matrices. Interestingly, the flexible thiol ethylene glycol linker on P800SO3-PEG induced a promising photothermal effect upon NIR laser irradiation, demonstrating potential theranostic imaging. Conclusions P800SO3-PEG shows a high affinity for bone tissues, deeper tissue imaging capabilities, minimum nonspecific uptake in the major organs, and photothermal effect upon laser irradiation, making it optimal for bone-targeted theranostic imaging. Supplementary Information The online version contains supplementary material available at 10.1186/s40824-022-00294-2.

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