TNT is one of the most commonly used nitro aromatic explosives used for landmine and military purpose. Due to the significant detrimental effects, contamination of soil and groundwater with TNT is the major concern. Driven by the need to detect trace amounts of TNT from environmental samples, this article demonstrates for the first time a highly selective and ultra sensitive, cysteine modified gold nanoparticle based label-free surface enhanced Raman spectroscopy (SERS) probe, for TNT recognition in 2 pico molar (pM) level in aqueous solution. Due to the formation of Meisenheimer complex between TNT and cysteine, gold nanoparticles undergo aggregation in the presence of TNT via electrostatic interaction between Meisenheimer complex bound gold nanoparticle and cysteine modified gold nanoparticle. As a result, it formed several hot spots and provided a significant enhancement of the Raman signal intensity by 9 orders of magnitude through electromagnetic field enhancements. A detailed mechanism for termendous SERS intensity change has been discussed. Our experimental results show that TNT can be detected quickly and accurately without any dye tagging in lower pM level with excellent discrimination against other nitro compounds and heavy metals.

Prostate cancer is the second leading cause of cancer-related death among the American male population and the cost of treating prostate cancer patients is about $10 billion/year in the US. Current treatments are mostly ineffective against advanced stage prostate cancer disease and are often associated with severe side effects. Driven by the need, in this manuscript, we report multifunctional nanotechnology-driven gold nano-popcorn based surface enhanced Raman scattering (SERS) assay for targeted sensing, nanotherapy treatment and in-situ monitoring of photothermal nanotherapy response during the therapy process. Our experimental data show that in the presence of LNCaP human prostate cancer cell, multifunctional popcorn shape gold nanoparticle forms several hot spots and provides a significant enhancement of the Raman signal intensity by several orders of magnitude (2.5 × 10 9 ). As a result, it can recognize human prostate cancer cell in 50 cells level. Our results indicate that the localized heating that occurs during NIR irradiation is able to cause irreparable cellular damage of the prostate cancer cell. Our in-situ time dependent results demonstrates for the first time that by monitoring SERS intensity change, one can monitor photo thermal nanotherapy response during therapy process. Possible mechanisms and operating principle of our SERS assay have been discussed. Ultimately, this nanotechnology driven assay could have enormous potential applications in rapid, on-site targeted sensing, nanotherapy treatment and monitoring of nanotherapy process which is critical to providing effective treatment of cancer disease.

Despite the modern treatment processes, contamination of food, water and medical equipment by pathogenic bacteria is very common in this world. Since the last two decades, one of the most important and complex problems our society has been facing is that several human pathogens became resistant to most of the clinically approved antibiotics. Recent advancement in nanoscience and nanotechnology has expanded our ability to design and construct nanomaterials with targeting, therapeutic, and diagnostic functions. These multifunctional materials have attracted our attention to be used as the promising tool for selective bacteria sensing and therapy without the current drugs. This tutorial review provides the basic concepts and critical properties of the different nanostructures that are useful for the pathogen detection and photothermal applications. In addition, bio-conjugated nanomaterial based strategies have been discussed with the aim to provide readers an overview of exciting opportunities and challenges in this field.

We report size- and distance-dependent surface-energy transfer (SET) properties of gold nanoparticles for recognizing hepatitis C virus (HCV) RNA sequence sensitively and selectively (single-base mutations) in a homogeneous format. We have demonstrated that quenching efficiency increases by three orders of magnitude, as the particle size increases from 5 to 70 nm. Due to this extraordinarily high K(SV), nanoparticle SET (NSET) detection limit can be as low as 300 fM concentration of RNA, depending on the size of gold nanoparticle. We have shown that the distance-dependent quenching efficiency is highly dependent on the particle size and the distance at which the energy-transfer efficiency is 50 %, ranges all the way from 8 nm, which is very close to the accessible distance of conventional Förster resonance energy transfer (FRET), to about 40 nm by choosing gold nanoparticles of different diameters. Our result points out that dipole-to-metal-particle energy transfer and NSET models provide a better description of the distance dependence of the quenching efficiencies for 8 nm gold nanoparticle, but agreement is poor for 40 and 70 nm gold nanoparticles, for which the measured values were always larger than the predicted ones.

Cancer is the greatest challenge in human healthcare today. Cancer causes 7.6 million deaths and economic losses of around 1 trillion dollars every year. Early diagnosis and effective treatment of cancer are crucial for saving lives. Driven by these needs, we report the development of a multifunctional plasmonic shell–magnetic core nanotechnology-driven approach for the targeted diagnosis, isolation, and photothermal destruction of cancer cells. Experimental data show that aptamer-conjugated plasmonic/magnetic nanoparticles can be used for targeted imaging and magnetic separation of a particular kind of cell from a mixture of different cancer cells. A targeted photothermal experiment using 670-nm light at 2.5 W/cm2 for 10 minutes resulted selective irreparable cellular damage to most of the cancer cells. We also showed that the aptamer-conjugated magnetic/plasmonic nanoparticle-based photothermal destruction of cancer cells is highly selective. We discuss the possible mechanism and operating principle for the targeted imaging, separation, and photothermal destruction using magnetic/plasmonic nanotechnology.

Fluorescence imaging in biological sciences is hindered by significant depth-dependent signal attenuation and high fluorescent backgrounds. We have developed optically modulated near-IR-emitting few-atom Ag nanodots that are selectively and dynamically photobrightened upon simultaneous excitation with a secondary laser enabling high sensitivity image extraction to reveal only the demodulated fluorophores. Image demodulation is demonstrated in high background environments to extract weak signals from completely obscuring background emission.

Low level: The amount of arsenic in Bangladeshi well water and in bottled drinking water and Mississippi tap water are indicated by a dynamic light scattering (DLS) assay. Label‐free gold nanoparticles are used in a selective colorimetric assay (see picture) and in a highly sensitive DLS assay for the recognition of arsenic in concentrations as low as 3 ppt.

Breast cancer is the most common cancer among women and it is the second leading cause of cancer deaths in women today. The key to the effective and ultimately successful treatment of diseases such as cancer is an early and accurate diagnosis. Driven by the need, in this article, we report for the first time a simple colorimetric and highly sensitive two-photon scattering assay for highly selective and sensitive detection of breast cancer SK-BR-3 cell lines in 100-cells/ml level using multifunctional (monoclonal anti-HER2/c-erb-2 antibody and S6 RNA aptamers conjugated) oval shape gold nanoparticle based nanoconjugate. When multifunctional oval shape gold nanoparticles were mixed with breast cancer SK-BR-3 cell line, a distinct color change occurs and two-photon scattering intensity increases by about 13 times. Experimental data with HaCaT non-cancerous cell line, as well as with MDA-MB-231 breast cancer cell line clearly demonstrated that our assay was highly sensitive to SK-BR-3 and it was able to distinguish from other breast cancer cell line which expresses low levels of HER-2. The mechanism of selectivity and assay's response change, have been discussed. Our experimental results reported here open up a new possibility of rapid, easy and reliable diagnosis of cancer cell lines by monitoring the colorimetric change and measuring TPS intensity from multifunctional gold nanosystems.