Using a lanthanide tagged nanobody to visualise Glial fibrillary acidic protein by secondary ion mass spectrometry
Lanthanide-labelled antibodies have been widely used for multiplex imaging of proteins directly from tissue using two approaches, imaging mass cytometry (IMC) and variants of secondary ion mass spectrometry (SIMS). Here we show the same approach can be taken using SIMS, but utilising lanthanide-labelled nanobodies instead. Nanobodies offer several advantages over conventional antibodies for antigen tagging, owing to their small size (12-15 kDa), high stability, and solubility. Their reduced molecular size enables greater diffusion through tissue, facilitating access to target sites and allowing them to reach regions that may be less accessible to larger antibodies. This enhanced accessibility can promote more effective localisation and increase binding to target antigens. In the work presented here, we produced a lanthanide-tagged nanobody and assessed its efficacy and compatibility with mass spectrometry imaging (MSI). We showed successful detection of Glial fibrillary acidic protein (GFAP) in tissue by correlating MSI of a lanthanide-tagged anti-GFAP nanobody with immunofluorescence microscopy imaging (IF). The use of nanobodies is an excellent alternative to current antibody tagging methods for SIMS and IMC.