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Probes for 19F Magnetic Resonance Imaging: PERFECTA

PERFECTA is not available in the US.

Introduction

19F Magnetic Resonance Imaging (19F MRI) is gaining momentum as a powerful diagnostic modality among currently available noninvasive bioimaging techniques.1 The absence of endogenous organic 19F signals in living tissues allows for in vivo visualization of exogenous fluorinated probes with improved signal-to-noise ratios, affording colored “hot spots” that are complementary to the anatomical information given by standard 1H MRI techniques.2 Among the issues that hamper 19F MRI clinical applications, there are a limited number of suitable fluorinated probes that do not suffer from drawbacks such as chemical shift artefacts due to the presence of more than one resonance frequency, long body retention times, and persistency in the environment.3

Developed by the Pierangelo Metrangolo group, the superfluorinated molecular probe PERFECTA (807982) represents a great advance in this field. Its high number of chemically equivalent 19F atoms produce a single and intense resonance peak with adequate spectral properties (i.e. relaxation times and sensitivity) for in vivo use in addition to minimal cytotoxicity and efficient cell uploading.4 Furthermore, PERFECTA’s molecular structure can be easily modified, yielding several asymmetrically substituted derivatives and thus opening up a plethora of new possible applications in the field of multimodal imaging platforms and theranostics.5

PERFECTA (suPERFluorinatEdContrasT Agent)

Advantages

19F MRI offers unique opportunities to image diseases and track cells and therapeutic agents in vivo. Despite its great diagnostic potential, there is only a limited set of commercially available fluorinated probes with satisfactory imaging performance and acceptable biocompatibility.

PERFECTA (acronym for suPERFluorinatEdContrasT Agent) is a new, highly fluorinated molecular probe that overcomes several existing gaps in 19F MRI technique.4 Its main advantages are listed below:

  1. Stable, crystalline solid
  2. 36 equivalent fluorine atoms per molecule
  3. Easily formulated in water using, e.g., 4% egg yolk lecithin and 4% safflower oil

The resulting homogeneous, cloudy, and off-yellow nanoemulsions exhibit excellent properties for in vivo clinical imaging, such as the following:

  1. High probe content (75 mg/mL, 1.61 × 1021 19F atoms/mL)
  2. High monodispersity (average droplet size = 140-220 nm; PDI < 0.2)
  3. Long shelf-life: 7 weeks at 4 °C; 6 weeks at r.t.
  4. Long-term stability (> 1 month) in biological fluids at 37 °C
  5. A single, very sharp and intense 19F NMR resonance peak (-73.5 ppm)
  6. Promising relaxation times: T1 < 640 ms; T2 > 180 ms

Representative Application

Optimized procedure for emulsion preparation:

  1. Dissolve egg yolk lecithin (4% w/v) in water.
  2. To this freshly prepared aqueous solution, add safflower oil (4% w/v).
  3. Heat the emulsion at 80 °C.
  4. In a separate sealed vessel, heat crystalline PERFECTA at 80 °C until completely melted.
  5. Add the hot emulsion to the melted fluorinated probe.
  6. Perform several cycles of heating and sonication, resulting in the final homogeneous, cloudy, off-yellow emulsion.

Thank you to the Metrangolo lab for contributing this Technology Spotlight!

Materials

     
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