Multifunctional plasmonic micro/nanobeads for sensitive suspension array assay and mass spectrometry analysis.

Plasmonic micro/nanobeads exhibit unique physicochemical properties attributed to their localized surface plasmon resonance (LSPR), enabling use in sensitive suspension array assays and matrix-assisted laser deposition/ionization mass spectrometry (MALDI-MS) analysis. Herein, we report a facile method for the preparation of magnetic plasmonic micro/nanobeads by the combination of Shirasu porous glass (SPG) membrane emulsification and polydopamine (PDA)-assisted in-situ reduction. The magnetic responsiveness properties endowed by doped FeO nanoparticles result in easy and complete separation of unwanted components during the preparation and bio-reaction processes. In addition, the coverage degree of the plasmonic shell can be flexibly controlled. As a result of the significant metal-enhanced fluorescence effect, as-prepared plasmonic microbeads enable the sensitive detection of alpha-fetoprotein (AFP) and deoxyribonucleotide (DNA) in suspension array with detection limits of 0.11 ng mL and 1.65 fmol mL, respectively, 8.6 times and 2 orders of magnitude higher than unmodified microbeads. Furthermore, as-prepared plasmonic nanobeads can be used as a matrix for MALDI-MS to allow the detection of low molecular weight biological molecules. As little as 0.2 pmol of proline and serine can be detected in a sample as small as 0.5 μL. This work provides a general strategy for the design of multifunctional plasmonic micro/nanomaterials that will help promote further advancements in sample analysis.