N-Adamantyl-1-Pentyl-4-Oxo-1,4-Dihydroquinoline-3-Carboxamide and N-(Adamantan-1-Yl)-2-(Alkyloxy)benzamide Derivatives as Fluorescent Probes for Selective CB2R Targeting
5 affiliations
- 1Department of Pharmacy-Pharmaceutical Sciences, , Via E. Orabona, 4, 70125 Bari, Italy; (G.R.M.); (G.G.); (M.M.); (F.M.); (A.L.); (M.M.); (M.G.P.); (N.A.C.)
- 2Centro Singular de Investigación en Química Biolóxica y Materiais Moleculares (CiQUS), , 15782 Santiago de Compostela, Spain (E.S.)
- 3Innopharma Screening Platform, BioFarma Research Group, Center for Research in Molecular Medicine and Chronic Diseases (CiMUS), , 15782 Santiago de Compostela, Spain; (J.B.); (M.I.L.)
- 4Department of Biosciences, Biotechnologies and Environment, , Via E. Orabona, 4, 70125 Bari, Italy;
- 5, National Research Council of Italy, 70126 Bari, Italy;
Abstract
Background/Objectives: The cannabinoid receptor subtype 2 (CB2R) is an increasingly important therapeutic and diagnostic target because of its involvement in inflammation-associated disorders, including cancer and neurodegenerative diseases. CB2R biology has traditionally been investigated using radioligands, whose broader application is limited by safety, regulatory, operational, and environmental constraints. Fluorescent ligands provide a complementary approach for real-time, high-resolution analysis of receptor expression and dynamics in living systems. This study aimed to develop structurally diverse fluorescent CB2R ligands as molecular tools for investigating receptor localization, trafficking, and signaling across imaging and cell-based platforms. Methods: Probe design was based on two complementary CB2R chemotypes: the 4-oxoquinolinone scaffold of the previously reported fluorescent ligands SM15 and VM7 and the salicylamide scaffold of the reference ligand CC48. These pharmacophores were conjugated to Cyanine 5 (Cy5), Cyanine 7 (Cy7), BODIPY-TR, 7-nitrobenzo-2-oxa-1,3-diazole (NBD), or 7-nitrobenzo-2-selena-1,3-diazole (Se-NBD), generating ligands with emission profiles spanning the green to near-infrared spectral regions. Compound 2, which showed the highest CB2R affinity among the new ligands (Ki = 143.4 nM) and negligible CB1R displacement at 1 µM, was characterized photophysically in organic and aqueous media and evaluated by flow cytometry in MCF7 and PANC-1 cancer cells, which display low and high CB2R expression, respectively. Results: Compound 2 retained nanomolar CB2R affinity and exhibited detectable fluorescence in organic solvents and aqueous buffer down to nanomolar concentrations. In flow cytometry experiments, its concentration-dependent fluorescence differentiated MCF7 from PANC-1 cells. Partial displacement by the CB2R reference ligand 13, particularly in PANC-1 cells, supported a receptor-specific component of the observed labeling. Conclusions: Compound 2 combines CB2R selectivity with robust fluorescence across chemically distinct environments and can distinguish cellular models with different receptor-expression levels. These findings establish compound 2 as a promising tool for CB2R detection and provide a rational basis for developing optimized fluorescent ligands for receptor imaging, target validation, and related translational applications.
Related
- 4-Diketopyrrole-2-carboxamide derivatives affecting HBV capsid assembly: structure-activity relationship around the GLP-26 scaffold.
- Near-infrared fluorescent clip-guided navigation in robot-assisted thoracoscopic esophagectomy for esophageal cancer: a single-center feasibility study
- Caspofungin-Based Red-Emissive Probes for Fluorescent Imaging of Pathogenic Fungi
- Hemicyanine-Based Wash-Free Near-Infrared Fluorescent Probe for Imaging Amyloid-β Aggregates in Alzheimer’s Disease
- Evaluation of a Novel Fluorescent Marker for Continuous Live Imaging of Preimplantation Embryos
BibTeX
@article{musillo2026nadamantyl1pentyl4oxo14dihydroquinoline3carboxamide,
title = {{N-Adamantyl-1-Pentyl-4-Oxo-1,4-Dihydroquinoline-3-Carboxamide and N-(Adamantan-1-Yl)-2-(Alkyloxy)benzamide Derivatives as Fluorescent Probes for Selective CB2R Targeting}},
author = {Gabriella Rosanna Musillo and Giovanni Graziano and Mariachiara Mammone and Francesco Mastropasqua and Maria Majellaro and Claudia Gioè-Gallo and Jose Brea and Maria Isabel Loza and Anselma Liturri and Morena Miciaccia and Maria Grazia Perrone and Angela Stefanachi and Matilde Colella and Domenico Alberga and Eddy Sotelo and Nicola Antonio Colabufo and Marialessandra Contino and Carmen Abate},
journal = {Pharmaceuticals (Basel, Switzerland)},
year = {2026},
month = oct,
doi = {10.3390/ph19101582},
url = {https://europepmc.org/article/PMC/PMC13708458},
note = {CC BY},
}
RIS
TY - JOUR
TI - N-Adamantyl-1-Pentyl-4-Oxo-1,4-Dihydroquinoline-3-Carboxamide and N-(Adamantan-1-Yl)-2-(Alkyloxy)benzamide Derivatives as Fluorescent Probes for Selective CB2R Targeting
AU - Gabriella Rosanna Musillo
AU - Giovanni Graziano
AU - Mariachiara Mammone
AU - Francesco Mastropasqua
AU - Maria Majellaro
AU - Claudia Gioè-Gallo
AU - Jose Brea
AU - Maria Isabel Loza
AU - Anselma Liturri
AU - Morena Miciaccia
AU - Maria Grazia Perrone
AU - Angela Stefanachi
AU - Matilde Colella
AU - Domenico Alberga
AU - Eddy Sotelo
AU - Nicola Antonio Colabufo
AU - Marialessandra Contino
AU - Carmen Abate
PY - 2026
DA - 2026/10/01
JO - Pharmaceuticals (Basel, Switzerland)
DO - 10.3390/ph19101582
UR - https://europepmc.org/article/PMC/PMC13708458
AB - Background/Objectives: The cannabinoid receptor subtype 2 (CB2R) is an increasingly important therapeutic and diagnostic target because of its involvement in inflammation-associated disorders, including cancer and neurodegenerative diseases. CB2R biology has traditionally been investigated using radioligands, whose broader application is limited by safety, regulatory, operational, and environmental constraints. Fluorescent ligands provide a complementary approach for real-time, high-resolution analysis of receptor expression and dynamics in living systems. This study aimed to develop structurally diverse fluorescent CB2R ligands as molecular tools for investigating receptor localization, trafficking, and signaling across imaging and cell-based platforms. Methods: Probe design was based on two complementary CB2R chemotypes: the 4-oxoquinolinone scaffold of the previously reported fluorescent ligands SM15 and VM7 and the salicylamide scaffold of the reference ligand CC48. These pharmacophores were conjugated to Cyanine 5 (Cy5), Cyanine 7 (Cy7), BODIPY-TR, 7-nitrobenzo-2-oxa-1,3-diazole (NBD), or 7-nitrobenzo-2-selena-1,3-diazole (Se-NBD), generating ligands with emission profiles spanning the green to near-infrared spectral regions. Compound 2, which showed the highest CB2R affinity among the new ligands (Ki = 143.4 nM) and negligible CB1R displacement at 1 µM, was characterized photophysically in organic and aqueous media and evaluated by flow cytometry in MCF7 and PANC-1 cancer cells, which display low and high CB2R expression, respectively. Results: Compound 2 retained nanomolar CB2R affinity and exhibited detectable fluorescence in organic solvents and aqueous buffer down to nanomolar concentrations. In flow cytometry experiments, its concentration-dependent fluorescence differentiated MCF7 from PANC-1 cells. Partial displacement by the CB2R reference ligand 13, particularly in PANC-1 cells, supported a receptor-specific component of the observed labeling. Conclusions: Compound 2 combines CB2R selectivity with robust fluorescence across chemically distinct environments and can distinguish cellular models with different receptor-expression levels. These findings establish compound 2 as a promising tool for CB2R detection and provide a rational basis for developing optimized fluorescent ligands for receptor imaging, target validation, and related translational applications.
SN - 1424-8247
ER -