High-Contrast Luminescent Immunohistochemistry Using PEGylated Lanthanide Complexes

Area of Science:

• Biomedical imaging
• Molecular pathology
• Nanotechnology

Background:

• Immunohistochemistry (IHC) offers high resolution but suffers from limited contrast due to probe brightness and tissue autofluorescence.
• Autofluorescence in biological tissues significantly hinders the sensitivity of conventional fluorescent imaging techniques.

Purpose of the Study:

• To enhance imaging contrast in immunohistochemistry by developing novel high-density labeled lanthanide probes.
• To overcome the limitations of autofluorescence and improve the detection of low-abundance biomarkers in tissue sections.

Main Methods:

• High-density labeling of long-lifetime lanthanide complexes, specifically seven europium complexes conjugated to an eight-arm hydrophilic poly(ethylene glycol) (PEG) linker.
• Utilizing time-gated imaging to minimize background autofluorescence and amplify signal from the lanthanide probes.
• Demonstrating compatibility with tyramide signal amplification (TSA) for further signal enhancement.

Main Results:

• Achieved signal amplification and improved water solubility (up to 10 mg/mL) of the lanthanide probes due to PEGylation.
• Enhanced contrast by 2-fold for human epidermal growth factor receptor 2 (HER2) in FFPE tissues and 3-fold for cytokeratin 18 (CK18) in frozen sections.
• Successfully visualized biomarkers with improved sensitivity and reduced background noise.

Conclusions:

• The developed high-density labeled lanthanide probes combined with time-gated imaging significantly improve IHC contrast and sensitivity.
• This approach offers a promising strategy for the sensitive detection of low-abundance biomarkers in complex tissue environments.
• The method holds potential for advancing diagnostic capabilities in pathology and molecular imaging.