[[File:Bio-layer interferometry wavelength shift due to analyte binding.gif|thumb|Figure 3]]
'''Bio-layer interferometry (BLI)''' is a modernoptical biosensing technology that analyzes biomolecular interactions in real-time without the need for fluorescent labeling.<ref>{{Cite book|last=David.|first=Apiyo,|url=http://worldcat.org/oclc/988866146|title=Handbook of Surface Plasmon Resonance.|date=2017|publisher=Royal Society of Chemistry|isbn=978-1-78801-139-6|oclc=988866146}}</ref> Alongside [[Surface plasmon resonance|Surface Plasmon Resonance]], BLI is one of few widely available [[Label-free quantification|label-free]] biosensing technologies, a detection style that allows for a higher volume of information to be obtained in a quicker amount of time compared to traditional processes.<ref>{{Cite journal|last=Syahir|first=Amir|last2=Usui|first2=Kenji|last3=Tomizaki|first3=Kin-ya|last4=Kajikawa|first4=Kotaro|last5=Mihara|first5=Hisakazu|date=2015-04-24|title=Label and Label-Free Detection Techniques for Protein Microarrays|url=http://dx.doi.org/10.3390/microarrays4020228|journal=Microarrays|volume=4|issue=2|pages=228–244|doi=10.3390/microarrays4020228|issn=2076-3905}}</ref> The technology relies on the phase shift-wavelength correlation created between interference patterns off of two unique surfaces on the tip of a biosensor.<ref>{{Cite journal|last=Müller-Esparza|first=Hanna|last2=Osorio-Valeriano|first2=Manuel|last3=Steube|first3=Niklas|last4=Thanbichler|first4=Martin|last5=Randau|first5=Lennart|date=2020-05-27|title=Bio-Layer Interferometry Analysis of the Target Binding Activity of CRISPR-Cas Effector Complexes|url=http://dx.doi.org/10.3389/fmolb.2020.00098|journal=Frontiers in Molecular Biosciences|volume=7|doi=10.3389/fmolb.2020.00098|issn=2296-889X}}</ref> BLI has significant applications in quantifying binding strength, measuring protein interactions, and identifying properties of reaction kinetics, such as rate constants and reaction rates.<ref>{{cite journal|last1=Rich|first1=Rebecca L|last2=Myszka|first2=David G|date=1 February 2007|title=Higher-throughput, label-free, real-time molecular interaction analysis.|journal=Analytical Biochemistry|volume=361|issue=1|pages=1–6|doi=10.1016/j.ab.2006.10.040|pmid=17145039}}</ref>
The binding between a [[Ligand (biochemistry)|ligand]] immobilized on the biosensor tip surface and an analyte in solution produces an increase in [[optical thickness]] at the biosensor tip, which results in a [[wavelength]] shift, Δλ (Figure 3), which is a direct measure of the change in thickness of the biological layer. Interactions are measured in real time, providing the ability to monitor binding specificity, rates of association and dissociation, or concentration, with high precision and accuracy.<ref>{{Cite book|url=https://www.worldcat.org/oclc/1012492391|title=Handbook of surface plasmon resonance|date=2017|others=R. B. M. Schasfoort|isbn=978-1-78801-028-3|edition=2|___location=Cambridge, England|oclc=1012492391}}</ref>
