Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2013 Feb 5;85(3):1431-9.
doi: 10.1021/ac302422k. Epub 2013 Jan 15.

Magnetic nanoparticle mediated enhancement of localized surface plasmon resonance for ultrasensitive bioanalytical assay in human blood plasma

Liang Tang  1 , Justin Casas, Meenakshi Venkataramasubramani
Affiliations

Magnetic nanoparticle mediated enhancement of localized surface plasmon resonance for ultrasensitive bioanalytical assay in human blood plasma

Liang Tang et al. Anal Chem. .

Abstract

We demonstrate that Fe(3)O(4) magnetic nanoparticle (MNP) can greatly enhance the localized surface plasmon resonance (LSPR) of metal nanoparticle. The high refractive index and molecular weight of the Fe(3)O(4) MNPs make them a powerful enhancer for plasmonic response to biological binding events, thereby enabling a significant improvement in the sensitivity, reliability, dynamic range, and calibration linearity for LSPR assay of small molecules in a trace amount. Rather than using fluorescence spectroscopy or magnetic resonance imaging, this study marks the first use of the label-free LSPR nanosensor for a disease biomarker in physiological solutions, providing a low cost, clinical-oriented detection. This facile and ultrasensitive nanosensor with an extremely light, robust, and low-cost instrument is attractive for miniaturization on a lab-on-a-chip system to deliver point-of-care medical diagnostics. To further evaluate the practical application of Fe(3)O(4) MNPs in the enhancement of LSPR assay, cardiac troponin I (cTnI) for myocardial infarction diagnosis was used as a model protein to be detected by a gold nanorod (GNR) bioprobe. MNP-captured cTnI molecules resulted in spectral responses up to 6-fold higher than direct cTnI adsorption on the GNR sensor. The detection limit (LOD) was lowered to ca. 30 pM for plasma samples which is 3 orders lower than a comparable study. To the best of our knowledge, this marks the lowest LOD for a real plasma protein detection based on label-free LSPR shift without complicated instrumentation. The observed LSPR sensing enhancement by Fe(3)O(4) MNPs is independent of nonspecific binding.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Synthesis and biofunctionalization of Au nanorods to construct a specific LSPR sensor. A: Scanning electron microscopy, size distribution and aspect ratio of Au nanorods demonstrating a longitudinal plasmonic peak at 650 nm. Inset: characteristic absorption spectrum of Au nanorod showing dominant surface plasmon resonance in the longitudinal direction (LSPR). B: Surface modification of CTAB capped gold nanorod (GNR-CTAB) by phase transfer ligand exchange to functionalize the nanoparticle with carboxyl group. DDT: dodecanthiol; MUDA: 11-mercaptoundecanoic acid. C: Absorption spectra of Au nanorod before and after MUDA coating to functionalize the nanoparticle surface with carboxyl terminals for antibody immobilization.
Figure 2
Figure 2
Synthesis, characterization and application of Fe3O4 superparamagnetic nanoparticle (NP) in LSPR assay. A: TEM image of Fe3O4 magnetic nanoparticle. Inset: black aggreates of MNPs in the suspension under magetic field. B: Hysterisis measurement. C: Schematic of MNP mediated nanoSPR assay on gold nanorod. D: Absoption spectra of Fe3O4 MNPs (blue) and antibody-MNP bioconjugates (inset). There are minimal interference with the plasmonic bands of Au nanorod (red).
Figure 3
Figure 3
Enhancement of LSPR response by magnetic nanoparticle. A: Representative absorption spectra of gold nanorod bioprobes before and after specific binding of cTnI antigen at 10 ng/ml (330 pM) with (dashed) and without (dotted) functional magnetic nanoparticles. B: Comparison of the longitudinal SPR red-shift in response to respective cTnI concentrations in the sensing range with (red) and without (blue) magnetic nanoparticle respectively (inset: summary of enhancement percentage by MNPs at various concentrations).
Figure 4
Figure 4
Schematic showing bioseparation of target molecules from blood plasma by functional Fe3O4 magnetic nanoparticles (MNPs), followed by MNP mediated nanoSPR assay. The application of MNP results in an enhancement of the LSPR shift at peak absorption wavelength. * schematic for illustration only.
Figure 5
Figure 5
Effect of the magnetic nanoparticle enhanced LSPR on sensitivity, dynamic range, and reliability of cTnI assay in 40% diluted human blood plasma. A: Standard curve of LSPR shift as a function of cTnI concentrations without MNPs. B: Standard curve calibration for MNP enhanced LSPR assay, showing an improved linear relationship between the cTnI concentrations and the LSPR shift resulting from specific binding of Fe3O4 MNP-cTnI conjugates. The LSPR responses are amplified by up to 6 fold.
Figure 6
Figure 6
High specificity of the LSPR assay for cTnI detection in plasma samples. Application of functional Fe3O4 magnetic nanoparticle results in signal amplification of the LSPR shift caused by specific cTnI binding only, with minimal effect on the nonspecific binding and background noise.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Mie G. Ann.Phys. 1908;25:377–445.
    1. Willets KA, Van Duyne RP. Annu.Rev.Phys.Chem. 2007;58:267–297. - PubMed
    1. Lee KS, El Sayed MA. J.Phys.Chem.B. 2006;110:19220–19225. - PubMed
    1. Jain PK, Lee KS, El Sayed IH, El Sayed MA. J.Phys.Chem.B. 2006;110:7238–7248. - PubMed
    1. Link S, El Sayed MA. Annu.Rev.Phys.Chem. 2003;54:331–366. - PubMed

Publication types