Metal-Enhanced Fluorescence of Phycobiliproteins from Heterogeneous Plasmonic Nanostructures

Abstract

We report here the use of plasmonic metal nanostructures in the form of silver island films (SiFs) to enhance the fluorescence emission of five different phycobiliproteins. Our findings clearly show that the phycobiliproteins display up to a 9-fold increase in fluorescence emission intensity, with a maximum 7-fold decrease in lifetime when they are assembled as a monolayer above SiFs, as compared to a monolayer assembled on the surface of amine-terminated glass slides of the control sample. The study was also repeated with a thin liquid layer of the phycobiliproteins sandwiched between two glass substrates (and a SiFs and a glass substrate) clamped together. Similarly, the results show a maximum 10-fold increase in fluorescence emission intensity coupled with a 2-fold decrease in lifetime of the phycobiliproteins in the SiF-glass setup as compared to the glass control sample, implying that near-field enhancement of phycobiliprotein emission can be attained both with and without chemical linkage of the proteins to the SiFs. Hence, our results clearly show that metal-enhanced fluorescence (MEF) can potentially be employed to increase the sensitivity and detection limit of the plethora of bioassays that employ phycobiliproteins as fluorescence labels, such as in fluoro-immunoassays where the assay can be tethered on the surface of SiFs, and also in flow cytometry where analytes in the liquid phase could potentially flow through channels coated with SiFs without actually being attached to the silver.

Interactions of Photosystem I with Plasmonic nanostructures

“…[5,32]. The preparation of SIF was performed as described in paper of Chowdhury et al [33]. Figure 1a shows an AFM image of a SIF structure as used for the described experiments.…”

Fluorescence Studies into the Effect of Plasmonic Interactions on Protein Function

“…The preparation of the SIF was performed as described in Chowdhury et al [42] AFM characterization shows size distributions ranging from 200-400 nm in width and 20-550 nm in height (Supporting Information, Figure SI1). The PSI-SIF sample was prepared by placing the diluted PSI sample between an untreated and the SIF-coated coverslip, which was placed on the back side of the sample with respect to the incident beam.…”

Nanoantenna enhanced emission of light-harvesting complex 2: the role of resonance, polarization, and radiative and non-radiative rates

“…As the fluorophore spends less time in the excited state, the photostability will increase and thus a higher number of photons can be detected before irreversible photobleaching occurs. 27,28 To date only a few studies on emission enhancement of lightharvesting complexes have been reported using chemically synthesized metal nanostructures such as silver island films, 29,30 gold, [31][32][33] and silver nanoparticles. 34 In most studies the individual contributions of excitation and QY changes to the total fluorescence enhancement have not been disentangled.…”