Capability of Spectral Flow Cytometry for Resolving Fluorochromes with Highly Overlapping Spectra

Significance of the topic

Spectral flow cytometry offers comprehensive emission profiling across multiple lasers, enabling resolution of fluorochromes with overlapping spectra that cannot be separated by conventional compensation-based flow cytometry.

Objectives and overview of the study

This application note demonstrates the capability of the Agilent NovoCyte Opteon spectral flow cytometer to resolve fluorochromes with highly overlapping spectral profiles. Designed multicolor panels and pairwise combinations assess the limits of spectral unmixing and quantify spillover spreading effects.

Applied methodology and instrumentation

Fluorescently labeled human blood samples, PBMCs or compensation beads were prepared with standard staining and lysis protocols. Samples were acquired on the NovoCyte Opteon UVBYR spectral flow cytometer equipped with five excitation lasers (349 nm, 405 nm, 488 nm, 561 nm, 637 nm) and 70 detectors. Single-stained controls generated reference spectral signatures, which were used in mathematical unmixing algorithms to deconvolute multicolor data.

Used Instrumentation

• Agilent NovoCyte Opteon UVBYR spectral flow cytometer with five lasers and 70 fluorescence detectors

Main results and discussion

Similarity indices for tested fluorochrome pairs ranged from 0.08 to 1.00. Key observations include:

• BB515/FITC pair (Similarity Index 0.99) remained distinct despite nearly identical spectra.
• Higher spectral similarity correlated with increased spillover spreading error and reduced resolution.
• Complex panels excited by single lasers (405 nm, 561 nm, 637 nm) showed clear population separation after unmixing.

These findings confirm robust unmixing performance while underscoring the importance of minimizing spectral overlap during panel design.

Benefits and practical applications of the method

Spectral flow cytometry expands panel flexibility by allowing use of fluorochromes with overlapping emissions, reducing compensation requirements and enabling simultaneous quantification of more biomarkers. This approach benefits immunophenotyping, rare cell detection and high-throughput screening in research and clinical laboratories.

Future trends and possibilities of application

Emerging developments include integration of additional laser lines and detectors, machine learning–driven unmixing algorithms, novel dyes with unique spectral signatures, and high-dimensional multiplexing strategies. These advances will further increase analytical depth and throughput in cellular and molecular investigations.

Conclusion

The Agilent NovoCyte Opteon spectral flow cytometer effectively distinguishes fluorochromes with highly overlapping emission spectra through full-spectrum unmixing. While very high similarity increases spillover spreading, the system successfully resolved dyes with a similarity index up to 0.99. Careful panel design remains essential to optimize resolution and ensure accurate data interpretation.