Synthesis, 68Ga-radiolabeling, and preliminary in vivo assessment of a depsipeptide-derived compound as a potential PET/CT infection imaging agent

Biomed Res Int. 2015:2015:284354. doi: 10.1155/2015/284354. Epub 2015 Jan 28.

Abstract

Noninvasive imaging is a powerful tool for early diagnosis and monitoring of various disease processes, such as infections. An alarming shortage of infection-selective radiopharmaceuticals exists for overcoming the diagnostic limitations with unspecific tracers such as (67/68)Ga-citrate or (18)F-FDG. We report here TBIA101, an antimicrobial peptide derivative that was conjugated to DOTA and radiolabeled with (68)Ga for a subsequent in vitro assessment and in vivo infection imaging using Escherichia coli-bearing mice by targeting bacterial lipopolysaccharides with PET/CT. Following DOTA-conjugation, the compound was verified for its cytotoxic and bacterial binding behaviour and compound stability, followed by (68)Gallium-radiolabeling. µPET/CT using (68)Ga-DOTA-TBIA101 was employed to detect muscular E. coli-infection in BALB/c mice, as warranted by the in vitro results. (68)Ga-DOTA-TBIA101-PET detected E. coli-infected muscle tissue (SUV = 1.3-2.4) > noninfected thighs (P = 0.322) > forearm muscles (P = 0.092) > background (P = 0.021) in the same animal. Normalization of the infected thigh muscle to reference tissue showed a ratio of 3.0 ± 0.8 and a ratio of 2.3 ± 0.6 compared to the identical healthy tissue. The majority of the activity was cleared by renal excretion. The latter findings warrant further preclinical imaging studies of greater depth, as the DOTA-conjugation did not compromise the TBIA101's capacity as targeting vector.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Infective Agents / chemistry
  • Anti-Infective Agents / pharmacology
  • Depsipeptides / chemistry*
  • Escherichia coli / drug effects
  • Escherichia coli Infections / diagnosis
  • Fluorodeoxyglucose F18 / chemistry
  • Gallium Radioisotopes / chemistry*
  • Heterocyclic Compounds, 1-Ring / chemistry
  • Isotope Labeling / methods
  • Male
  • Mice
  • Mice, Inbred BALB C
  • Muscles / microbiology
  • Positron-Emission Tomography / methods
  • Radiopharmaceuticals / chemistry*
  • Tomography, X-Ray Computed / methods

Substances

  • Anti-Infective Agents
  • Depsipeptides
  • Gallium Radioisotopes
  • Heterocyclic Compounds, 1-Ring
  • Radiopharmaceuticals
  • Fluorodeoxyglucose F18
  • 1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid