After administration of nanoparticle (NP) into biological fluids, an NP-protein complex is formed, which represents the "true identity" of NP in our body. Hence, protein-NP interaction should be carefully investigated to predict and control the fate of NPs or drug-loaded NPs, including systemic circulation, biodistribution, and bioavailability. In this review, we mainly focus on the formation of protein corona and its potential applications in pharmaceutical sciences such as prediction modeling based on NP-adsorbed proteins, usage of active proteins for modifying NP to achieve toxicity reduction, circulation time enhancement, and targeting effect. Validated correlative models for NP biological responses mainly based on protein corona fingerprints of NPs are more highly accurate than the models solely set up from NP properties. Based on these models, effectiveness as well as the toxicity of NPs can be predicted without in vivo tests, while novel cell receptors could be identified from prominent proteins which play important key roles in the models. The ungoverned protein adsorption onto NPs may have generally negative effects such as rapid clearance from the bloodstream, hindrance of targeting capacity, and induction of toxicity. In contrast, controlling protein adsorption by modifying NPs with diverse functional proteins or tailoring appropriate NPs which favor selective endogenous peptides and proteins will bring promising therapeutic benefits in drug delivery and targeted cancer treatment.

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Protein corona: a new approach for nanomedicine design.

The optical properties of various nanostructures have been widely adopted for biological detection, from DNA sequencing to nano-scale single molecule biological function measurements. In particular, by employing localized surface plasmon resonance (LSPR), we can expect distinguished sensing performance with high sensitivity and resolution. This indicates that nano-scale detections can be realized by using the shift of resonance wavelength of LSPR in response to the refractive index change. In this paper, we overview various plasmonic nanostructures as potential sensing components. The qualitative descriptions of plasmonic nanostructures are supported by the physical phenomena such as plasmonic hybridization and Fano resonance. We present guidelines for designing specific nanostructures with regard to wavelength range and target sensing materials.

https://www.mdpi.com/1424-8220/11/11/10907/pdf

Plasmonic nanostructures for nano-scale bio-sensing.

A fluorescence resonance energy transfer (FRET) biosensor based on graphene quantum dots (GQDs) and gold nanoparticles (AuNPs) for the detection of mecA gene sequence of Staphylococcus aureus.

Gold nanoparticles and nearby fluorophores interact via electromagnetic coupling upon light excitation We determine the distance and wavelength dependence of this coupling theoretically and experimentally via steady-state and time-resolved fluorescence spectroscopy For the first time, the fluorescence quenching of four different dye molecules, which absorb light at different wavelengths across the visible spectrum and into the near-infrared, is studied using a rigid silica shell as a spacer A comprehensive experimental determination of the distance dependence from complete quenching to no coupling is carried out by a systematic variation of the silica shell thickness Electrodynamic theory predicts the observed quenching quantitatively in terms of energy transfer from the molecular emitter to the gold nanoparticle The plasmonic field enhancement in the vicinity of the 13 nm gold nanoparticles is calculated as a function of distance and excitation wavelength and is included in all calculations Relativ

Distance and wavelength dependent quenching of molecular fluorescence by Au@SiO2 core-shell nanoparticles

Silver-Based Plasmonic Nanoparticles for and Their Use in Biosensing

Transverse surface plasmon resonances (SPR) in Au–Ag and Ag–Au core–shell structure nanowires have been investigated by means of quasi-static theory. There are two kinds of SPR bands resulting from the outer surface of wall metal and the interface between core and wall metals, respectively. The SPR corresponding to the interface, which is similar to that of alloy particle, decreases and shifts obviously with increasing the wall thickness. However, the SPR corresponding to the outer surface, which is similar to that of pure metal particle, increases and shifts slightly with increasing the wall thickness. A mechanism based on oscillatory surface electrons under coulombic attraction is developed to illuminate the shift fashion of SPR from bimetallic core–shell interface. The net charges and extra coulombic force in metallic wall affect the SPR energy and the shift fashion.

/pdf/surface-plasmon-resonance-from-bimetallic-interface-in-au-ag-x8d0w36aqq.pdf

Surface Plasmon Resonance from Bimetallic Interface in Au-Ag Core-Shell Structure Nanowires.

Plasmonic light absorption properties of three-layered Au–Ag bimetallic nanoshells are investigated using the quasi-static electricity and plasmon hybridization theory. Comparing with Au-dielectric-Au and Ag-dielectric-Au multilayer nanoshells, Au-dielectric-Ag multilayer nanoshells are demonstrated more suitable for triple-bands surface plasmon resonance (SPR). Calculation results indicated that the triple plasmon resonance in Au-dielectric-Ag multilayer nanoshells could be optimized by choosing appropriate geometrical dimensions of the inner gold sphere and outer silver shell. The corresponding physical mechanism has also been illustrated by analyzing the surface charge distribution and intercoupling of the polarization fields from different metal–dielectric interfaces. This triple-bands SPR in the bimetallic multilayer nanostructure provides potential for multiplex biosensing based on SPR absorption, surface enhanced fluorescence, and surface enhanced Raman scattering (SERS).

Optimization of Three-Layered Au-Ag Bimetallic Nanoshells for Triple-Bands Surface Plasmon Resonance

The core refractive index sensitivity of a gold nanotube was investigated by calculating the shift of local surface plasmon resonance (LSPR). It was found that the core refractive index sensitivity can be improved by reducing the wall thickness or the surrounding refractive index. The sensitivity increases exponentially with decreasing wall thickness, but increases linearly with decreasing surrounding refractive index. This multi-factor controlled sensitivity of gold nanotube enlarges the ability of optimizing the refractive index sensors. The physical origin of this tunable refractive index sensitivity of gold nanotube was also investigated based on the plasmon hybridization and repulsive effects on the restoring force of plasmon oscillation. This physical mechanism can be used for designing core–shell metallic nanostructures for effective LSPR chemical and biological sensing.

Improve the refractive index sensitivity of gold nanotube by reducing the restoring force of localized surface plasmon resonance

In this paper, we investigated the characteristics of band gaps and defect states in a locally resonant phononic crystal structure consisting of multiple square stubs deposited on both sides of a thin homogeneous plate Using the finite element method and supercell technique, we calculated the dispersion relationships and power transmission spectra of this structure, which agree well with each other This structure offers wide band gaps at extremely low frequencies Moreover, we investigated how the band gaps are affected by the distance between two adjacent square stubs, finding that acoustic band gaps are very sensitive to the distance between two adjacent square stubs, a property important for practical applications Based on this finding, we proposed a novel method to form phononic crystal structure defect: Defect bands can be induced by creating defects inside the original complete band gaps The frequency can then be tuned by changing the distance between two adjacent square stubs of the defect scatterer These results will help in fabricating devices, such as acoustic filters and waveguides whose band frequency can be modulated

Jian Zhu

Papers

Surface Plasmon Resonance from Bimetallic Interface in Au-Ag Core-Shell Structure Nanowires.

Optimization of Three-Layered Au-Ag Bimetallic Nanoshells for Triple-Bands Surface Plasmon Resonance

Improve the refractive index sensitivity of gold nanotube by reducing the restoring force of localized surface plasmon resonance

Band gap and defect state engineering in a multi-stub phononic crystal plate

The effect of inserted gold nanosphere on the local field enhancement of gold nanoshell