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Volume 6, Issue 4 (Suppl)

J Material Sci Eng, an open access journal

ISSN: 2169-0022

Materials Congress 2017

June 12-14, 2017

June 12-14, 2017 Rome, Italy

Materials Science and Engineering

World Congress on

Nanoplasmonic upconverting nanoparticles as orientation sensors for single particle microscopy

Shuang F Lim, Kory K Green

and

Janina Wirth

North Carolina State University, USA

Statement of the Problem:

Protein-DNA interactions are the center of many important biological pathways including DNA

replication, transcription, recombination, and repair. Dynamic movements of proteins on DNA include jumping, hopping and quasi-

1D curvilinear movement during which the protein maintains continuous DNA contact (Fig. 1). While some work has been done

on translational motion of proteins on DNA, the 3D rotational motion of the proteins on DNA, is less explored, due to limitations

in current nanoprobes. Recent studies have shown that rare earth upconverting nanoparticles (UCNP) offer an attractive alternative

method for tracking orientation due to their inherent excitation polarization dependence. UCNPs are excited in the near infrared

and fluoresce via anti-stokes emission in the visible energy range (400‒800 nm), making them attractive for use in biological settings

due to their low-energy excitation photon energy. UCNPs are excellent fluorescent probes, as they have no blinking, bleaching,

or fluorescence background due to their near infrared excitation. These properties allow dynamic molecular interactions to be

tracked continuously in real time. By coating disk-shaped UCNPs with a metal layer (NP-UCNP), they gain a large anisotropy in the

fluorescence yield if illuminated with polarized light. This fluorescence anisotropy of the NP-UCNP probe renders them as excellent

orientation probes in both linear and 3D tracking.

Methodology & Theoretical Orientation:

We have designed and demonstrate proof of concept of single particle orientation

and rotation tracking of NP-UCNP probes. We apply 1) predictive modeling to design and optimize NP- UCNPs for anisotropic

fluorescence intensity with orientation, 2) performcorrelated structural and optical single nanoparticle spectroscopy of nanofabricated

NP-UCNPs to validate model predictions, and 3) analyzed the diffusional characteristics of a single NP-UCNP tumbling in solution

between coverslip and slide to confirm that the orientation dependent fluorescence of the single NP-UCNP can be used to track single

molecules.

Findings:

It was found that the shape asymmetry of the UCNP itself contributes strongly to the orientation and excitation polarization

dependence of the emission intensity. The presence of a gold shell enhances the intensity contrast between flat and edge orientations.

We analyzed a particle tumbling in solution to show that the diffusional constant of a single particle can be determined.

Conclusion & Significance:

The proposed new orientation sensitive platform based on NP-UCNP probes that can be coupled to

proteins has wide-ranging applications in the future analysis and compilation of protein dynamics in any biological system. This

model will open new opportunities for the biomedical research community to develop novel technologies for early diagnosis, control,

and treatment of a wide-range of human diseases.

J Material Sci Eng 2017, 6:4(Suppl)

DOI: 10.4172/2169-0022-C1-068