Related Experiment Video
Updated: May 2, 2026
Genetically-encoded Molecular Probes to Study G Protein-coupled Receptors
Published on: September 13, 2013
A high-affinity near-infrared fluorescent probe to target bombesin receptors
Ajay Shrivastava1, Haiming Ding, Shankaran Kothandaraman
1Department of Radiology, The Ohio State University, Columbus, OH, 43210, USA.
Purpose:
This study aimed to create new optical surgical navigation NIRF probes for prostate and breast cancers.
Procedures:
IR800-linker-QWAVGHLM-NH2 with linker = GSG, GGG, and G-Abz4 were synthesized and characterized. IC50 for bombesin receptors (BBN-R) in PC-3 prostate and T47D breast cancer cells, fluorescence microscopy in PC-3 cells, and NIRF imaging in mice PC-3 tumor xenografts were studied.
Results:
GGG, GSG, and G-Abz4 derivatives had IC50 (nM) for BBN-R+ PC-3 cells = 187 ± 31, 56 ± 5, and 2.6 ± 0.2 and T47D cells = 383 ± 1, 57.4 ± 1.2, and 3.1 ± 1.1, respectively. By microscopy the Abz4 derivative showed the highest uptake, was competed with by BBN, and had little to no binding to BBN-R- cells. In NIRF imaging the G-Abz4 probe was brighter than GGG probe in BBN-R+ tissues in vivo and tissues, tumors, and tumor slices ex vivo. Uptake could be partially blocked in BBN-R+ pancreas but not visibly in tumor.
Conclusions:
Linker choice can dominate peptidic BBN-R binding. The G-Abz4 linker yields a higher affinity and specific BBN-R binder in this series of molecules.
Insights
New near-infrared fluorescent (NIRF) probes were developed for surgical navigation in prostate and breast cancers. The G-Abz4 linker demonstrated superior binding affinity and specificity to bombesin receptors (BBN-R), enhancing probe performance.
Area of Science:
- Biomedical Engineering
- Chemical Biology
- Oncology
Background:
- Optical surgical navigation enhances tumor resection accuracy.
- Near-infrared fluorescence (NIRF) imaging offers deep tissue penetration for in vivo visualization.
- Bombesin receptors (BBN-R) are overexpressed in several cancers, including prostate and breast cancer, making them attractive targets for molecular imaging and therapy.
Purpose of the Study:
- To synthesize and characterize novel NIRF probes for optical surgical navigation.
- To evaluate the binding affinity and specificity of these probes to BBN-R in prostate and breast cancer cells.
- To assess the in vivo performance of the most promising probe using NIRF imaging.
Main Methods:
- Synthesis and characterization of IR800-linker-QWAVGHLM-NH2 probes with varying linkers (GSG, GGG, G-Abz4).
- In vitro evaluation of bombesin receptor (BBN-R) binding affinity (IC50) in PC-3 (prostate) and T47D (breast) cancer cells.
- Fluorescence microscopy in PC-3 cells and in vivo NIRF imaging in mice bearing PC-3 tumor xenografts.
Main Results:
- The G-Abz4 linker derivative exhibited the highest binding affinity (lowest IC50) to BBN-R in both PC-3 and T47D cells compared to GSG and GGG linkers.
- Fluorescence microscopy confirmed high cellular uptake of the G-Abz4 probe in BBN-R-positive cells, with specificity demonstrated by competition with bombesin and minimal binding to BBN-R-negative cells.
- In vivo NIRF imaging revealed that the G-Abz4 probe provided brighter signals in BBN-R-positive tissues compared to the GGG probe, with partial blocking observed in the pancreas but not visibly in tumors.
Conclusions:
- Linker selection significantly influences the binding characteristics of peptidic BBN-R targeting probes.
- The G-Abz4 linker confers enhanced affinity and specificity for BBN-R, making it a promising component for developing advanced NIRF imaging agents.
- These findings support the development of targeted NIRF probes for improved optical surgical navigation in BBN-R-expressing cancers.
