Litmus › BLI vs SPR for VHHs
Binding Kinetics · Nanobodies

BLI vs. SPR for VHH Binding Kinetics: Which to Run?

VHHs (nanobodies) are small — typically 12–15 kDa — which makes precise kinetic resolution harder on any platform. Here's how the two main techniques compare, and when each one is the right call.

~15 kDa typical VHH size
SPR what Litmus runs
The Comparison

BLI and SPR, side by side

Bio-Layer Interferometry (BLI)
Surface Plasmon Resonance (SPR)
Throughput: High — disposable biosensors run in parallel with no microfluidics, good for screening large VHH panels quickly.
Throughput: Lower — injections typically run serially over a single flow cell, better suited to a shortlist than a full screen.
Sensitivity: Less sensitive to bulk refractive index shifts, but resolution can suffer on very small analytes or weak binders.
Sensitivity: Higher resolution for sub-nanomolar affinities and fast kinetics — generally the more precise read on a small VHH.
Sample use: Lower reagent consumption per run given disposable tips — useful when VHH supply is limited.
Sample use: Slightly higher consumption from regeneration cycles, though modern chips need only micrograms.
Surface reuse: Disposable biosensors avoid regeneration entirely — no carryover risk between samples.
Surface reuse: Requires regeneration optimization on a reusable chip, adding method-development time up front.
Best for: Primary screening of large VHH panels, where speed and throughput matter more than resolution.
Best for: Confirmatory kinetics on a shortlist, or any decision that depends on kon/koff — not just KD.
The Litmus Take

VHHs' small size makes precise kinetic resolution harder on either platform, but once you've narrowed to a shortlist, SPR's sensitivity generally makes it the better choice for the kon/koff/KD data that drives affinity maturation and SAR decisions. BLI stays useful upstream if you already have panel-scale screening to do first. Litmus's network runs SPR for this kind of confirmatory kinetics work.

Next Step

Ready for SPR on your shortlist?

Get an SPR Assay Quote 5–7 days Scope your request — target, analyte, and expected affinity range SPR Assay Service 5–7 days Full spec sheet, AI-ready output format, and use cases

Have a VHH shortlist ready?

Start your request in the Litmus platform — tell us your target and analyte, and a qualified lab will confirm surface chemistry and turnaround.

Get an SPR Quote →

Or email us directly. No spam, ever.