Lanthenide-Doped Nanophosphor labels for Protein Microarrays

Background: Conventional organic fluorescent labels are currently being employed for detection of query molecules on protein microarrays platform; however, they exhibit certain limitations like poor photo-stability, overlapped emission/excitation spectra, autofluorescence, limited sensitivity, rigorous sample preparation procedures and are expensive. Objective: Objective of this study was to develop new labels which can overcome the limitations associated with existing labels and can be used with existing microarrays setup. Nanophosphor labels seem to be the most promising nano-material, which could overcome most of these limitations. Yttrium oxide (Y2O3) doped with 1.5% Gadolinium (Gd) and 2% Europium (Eu) has a quantum efficiency of about 70%. The emission wavelength lies in red region (612 nm) and could be excited in green region (532 nm), therefore it could be employed with existing microarrays instrumentation setup. Method: Y2O3: Eu, Gd nanophosphor labels were synthesized by Pechini-type in situ polymerizable complex (IPC) method. Surface modification was done by modified Strober method, for their bioconjugation with proteins/antibodies via amine-carboxylic zero-length cross-linking mechanism. Results: Bovine Serum Albumin (BSA) and anti-BSA were bioconjugated with Y2O3: Eu, Gd nanophosphor labels and their application on reverse phase protein/antibody microarrays platform was demonstrated as a proof of concept. Specificity and limit of detection of Y2O3: Gd, Eu labels was determined on protein/antibody microarray platform using nanophosphors labeled Glutathione S-transferases (GST) and anti-GST. Conclusion: These novel nanophosphors-based labels have potential to overcome several limitations of existing labels and hence could be employed for the protein microarrays applications.