Optical-ruler-based distance measurements are essential for tracking biomolecular processes in a wide range of analytical biochemical applications. The normally used Förster resonance energy transfer (FRET) ruler is not useful for investigating distance-dependent properties when distances are more than 10 nm. Driven by this limitation, we have developed a long-range surface-enhanced Raman spectroscopy (SERS) optical ruler using oval-shaped gold nanoparticles and Rh6G dye-modified rigid, variable-length double-strand DNAs. The bifunctional rigid dsDNA molecule serves as the SERS-active ruler. Our experimental results show that one can tune the length of the SERS ruler between 8 and ∼18 nm by choosing the size of the oval-shaped gold nanoparticles. A possible mechanism for our observed distance-dependent SERS phenomenon is discussed using the Gersten and Nitzan model. Ultimately, our long-range SERS molecular rulers can be an important step toward understanding distance-dependent biological processes.

Despite intense efforts, Alzheimer’s disease (AD) is one of the top public health crisis for society even at 21st century. Since presently there is no cure for AD, early diagnosis of possible AD biomarkers is crucial for the society. Driven by the need, the current manuscript reports the development of magnetic core-plasmonic shell nanoparticle attached hybrid graphene oxide based multifunctional nanoplatform which has the capability for highly selective separation of AD biomarkers from whole blood sample, followed by label-free surface enhanced Raman spectroscopy (SERS) identification in femto gram level. Experimental ELISA data show that antibody-conjugated nanoplatform has the capability to capture more than 98% AD biomarkers from the whole blood sample. Reported result shows that nanoplatform can be used for SERS “fingerprint” identification of β-amyloid and tau protein after magnetic separation even at 100 fg/mL level. Experimental results indicate that very high sensitivity achieved is mainly due to the strong plasmon-coupling which generates huge amplified electromagnetic fields at the “hot spot”. Experimental results with nontargeted HSA protein, which is one of the most abundant protein components in cerebrospinal fluid (CSF), show that multifunctional nanoplatform based AD biomarkers separation and identification is highly selective.

Second harmonic generation (SHG) imaging using near infrared laser light is the key to improving penetration depths, leading to biological understanding. Unfortunately, currently SHG imaging techniques have limited capability due to the poor signal-to-noise ratio, resulting from the low SHG efficiency of available dyes. Targeted tumor imaging over nontargeted tissues is also a challenge that needs to be overcome. Driven by this need, in this study, the development of two-photon SHG imaging of live cancer cell lines selectively by enhancement of the nonlinear optical response of gold nanocage assemblies is reported. Experimental results show that two-photon scattering intensity can be increased by few orders of magnitude by just developing nanoparticle self-assembly. Theoretical modeling indicates that the field enhancement values for the nanocage assemblies can explain, in part, the enhanced nonlinear optical properties. Our experimental data also show that A9 RNA aptamer conjugated gold nanocage assemblies can be used for targeted SHG imaging of the LNCaP prostate cancer cell line. Experimental results with the HaCaT normal skin cell lines show that bioconjugated nanocage-based assemblies demonstrate SHG imaging that is highly selective and will be able to distinguish targeted cancer cell lines from other nontargeted cell types. After optimization, this reported SHG imaging assay could have considerable application for biology.

This paper reports for the first time the development of a large-scale SERS substrate from a popcorn-shaped gold nanoparticle-functionalized single walled carbon nanotubes hybrid thin film for the selective and highly sensitive detection of explosive TNT material at a 100 femtomolar (fM) level.

Gold nanotechnology driven recent approach opens up a new possibility for the destruction of cancer cells through photothermal therapy. Ultimately, photothermal therapy may enter into clinical therapy and as a result, there is an urgent need for techniques to monitor on time tumor response to therapy. Driven by the need, in this article we report nanoparticle surface energy transfer (NSET) approach to monitor photothermal therapy process by measuring the simple fluorescence intensity change. Florescence intensity change is due to the light-controlled photothermal release of ssDNA/RNA via dehybridization during therapy process. Our time dependent results show that just by monitoring fluorescence intensity change, one can monitor photothermal therapy response during therapy process. Possible mechanism and operating principle of our NSET assay have been discussed. Ultimately, this NSET assay could have enormous potential applications in rapid, on-site monitoring of photothermal therapy process, which is critical to providing effective treatment of cancer and MDRB infections.