RAMAN LABELS IN LIFE SCIENCES
Raman signals are proportional to concentration and are extremely robust (i.e. no energy transfer between labels such as in fluorescence). It is thus possible to mix a high number of Raman-based labels without affecting their spectral signatures and intensity, making them perfect candidates for simultaneous multicomponent analysis. They can be used in applications such as biomarker identification, protein interaction studies, immunological profiling and vaccine development, among others.
Modifying the Raman label
Modification of the dyes@CNT-COOH labels can easily be achieved through the carbodiimide-mediated amidation. The carboxylic acid group (-COOH) of the label is activated by carbodiimide and will couple with any primary amine (-NH2). On proteins and antibodies, primary amines are present in lysine residues and at the N-terminus of polypeptide chains and can react with the Raman label to form an amide bond. This ecofriendly and biocompatible reaction is done in water and is depticted below.
Biotin-Avidin interaction
Our Raman labels are also available with a biotin moetie. Biotin and avidin form the strongest non-covalent complex known between ligand and protein. As seen below, one avidin will bind 4 biotins with a binding constant (Kd) of 10-15 M. Many applications such as enzyme-linked immunosorbent assay, immunohistochemistry, protein arrays, and cell sorting amongst others, utilize this interaction. Kits can be purchased commercially to modify biotin or streptavidin. Our biotinylated Raman labels will attach to any streptavidin/avidin or anti-biotin modified antibody, receptor, or peptide allowing the detection of a target molecule by Raman spectroscopy.
Our Raman labels offer new properties compared to traditional fluorescent tags. For exemple, as illustrated below, multiple target molecules can be tagged on the same cell with unequivocal identification of each Raman label because there is no energy transfer between the labels and they offer quantitative analysis. This multiplexing capability reduces sample size, time of analysis and volume of reagent required. The very stable read-out signal of the Raman label also permits prolonged acquisitions, and repeated illumination of the same surface. For instance, one could follow a target over the course of weeks. Raman labels can also be used as non-specific labels since they readily penetrate the cell membrane.
