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Ciaffaglione V, Waghorn PA, Exner RM, Cortezon-Tamarit F, Godfrey SP, Sarpaki S, Quilter H, Dondi R, Ge H, Kociok-Kohn G, Botchway SW, Eggleston IM, Dilworth JR, Pascu SI. Structural Investigations, Cellular Imaging, and Radiolabeling of Neutral, Polycationic, and Polyanionic Functional Metalloporphyrin Conjugates. Bioconjug Chem 2021; 32:1374-1392. [PMID: 33525868 PMCID: PMC8299459 DOI: 10.1021/acs.bioconjchem.0c00691] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Over the past decade,
porphyrin derivatives have emerged as invaluable
synthetic building blocks and theranostic kits for the delivery of
cellular fluorescence imaging and photodynamic therapy. Tetraphenylporphyrin
(TPP), its metal complexes, and related derivatives have been investigated
for their use as dyes in histology and as components of multimodal
imaging probes. The photophysical properties of porphyrin–metal
complexes featuring radiometals have been a focus of our attention
for the realization of fluorescence imaging probes coupled with radioimaging
capabilities and therapeutic potential having “true”
theranostic promise. We report hereby on the synthesis, radiochemistry,
structural investigations, and preliminary in vitro and in vivo uptake studies on a range of functionalized
porphyrin-based derivatives. In pursuit of developing new porphyrin-based
probes for multimodality imaging applications, we report new functionalized
neutral, polycationic, and polyanionic porphyrins incorporating nitroimidazole
and sulfonamide moieties, which were used as targeting groups to improve
the notoriously poor pharmacokinetics of porphyrin tags. The resulting
functional metalloporphyrin species were stable under serum challenges
and the nitroimidazole and sulfonamide derivatives remained fluorescent,
allowing in vitro confocal studies and visualization
of the lysosomal uptake in a gallium(III) sulfonamide derivative.
The molecular structures of selected porphyrin derivatives were determined
by single crystal X-ray diffraction using synchrotron radiation. We
also investigated the nature of the emission/excitation behavior of
model functional porphyrins using in silico approaches
such as TD DFT in simple solvation models. The conjugation of porphyrins
with the [7-13] and [7-14] fragments of bombesin was also achieved,
to provide targeting of the gastrin releasing peptide receptor (GRPR).
Depending on the metal, probe conjugates of relevance for single photon
emission computed tomography (SPECT) or positron emission tomography
(PET) probes have been designed and tested hereby, using TPP and related
functional free base porphyrins as the bifunctional chelator synthetic
scaffold and 111In[In] or 68Ga[Ga], respectively,
as the central metal ions. Interestingly, for simple porphyrin conjugates
good radiochemical incorporation was obtained for both radiometals,
but the presence of peptides significantly diminished the radio-incorporation
yields. Although the gallium-68 radiochemistry of the bombesin conjugates
did not show radiochemical incorporation suitable for in vivo studies, likely because the presence of the peptide changed the
behavior of the TPP-NH2 synthon taken alone, the optical
imaging assays indicated that the conjugated peptide tags do mediate
uptake of the porphyrin units into cells.
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Affiliation(s)
- Valeria Ciaffaglione
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | - Philip A Waghorn
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Rüdiger M Exner
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | | | - Samuel P Godfrey
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | - Sophia Sarpaki
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | - Helena Quilter
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom.,Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom.,Centre for Sustainable and Circular Technologies, University of Bath, Bath, BA2 7AY, United Kingdom
| | - Ruggero Dondi
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | - Haobo Ge
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | - Gabriele Kociok-Kohn
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom.,Material and Chemical Characterisation (MC2), University of Bath, Bath, BA2 7AY, United Kingdom
| | - Stanley W Botchway
- Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Oxford, Didcot, OX11 0QX, United Kingdom
| | - Ian M Eggleston
- Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
| | - Jonathan R Dilworth
- Chemistry Research Laboratory, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Sofia I Pascu
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom.,Centre for Sustainable and Circular Technologies, University of Bath, Bath, BA2 7AY, United Kingdom
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