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Metal nanoparticles (NPs) have recognized a growing importance in chemistry, electronics, optics, physics, and biology in the last decades. The possibility of tuning their unique properties varying dimension and morphology widely extends the range of possible applications. Several innovative chemical routes have been investigated to design shape-controlled synthesis to combine high-yield production with controllable and repeatable morphology. This chapter will focus on gold and silver NPs because of the easiness in synthesis control and of the large implementation in research and industrial applications. Synthesis methods, different morphologies and properties, and some of the possible applications will be discussed and reviewed. [ABSTRACT FROM AUTHOR]

Adhesion assays based on single molecule interactions are a useful option when discerning between avidity and affinity in complex systems. This is especially true for viral adhesion to living cells which typically involves a complex system of proteins working together to lead to productive infection. Here, we discuss assays that have been used to quantitatively study the adhesion of viral and cellular receptors including surface plasmon resonance, real time fusion assays involving viral fluorescent tags and single molecule force spectroscopy (SMFS). We highlight the advantages of SMFS over other methods, including its specificity, versatility and application to studying the adhesion of HIV-1 to human cells. We discuss how using SMFS with infectious virus and living cells allow us to distinguish the adhesion of HIV-1 surface protein, gp120, to its primary cellular receptor, CD4, from the adhesion of gp120 to its secondary co-receptor, CCR5. [ABSTRACT FROM AUTHOR]

Chemical cues and nano-topographies present on the surface or in the extracellular medium strongly influence the fate and adhesion of biological cells. Careful tuning of cell–matrix interaction via engineered surfaces, either attractive or repulsive, require non-invasive, long time monitoring capabilities and lay the foundation of sensing platforms for risk assessment. Aiming to assess changes underwent by biointerfaces due to cell–environment interaction (in particular nanotechnology products), we have developed hybrid cellular platforms allowing for time based dual assays, i.e., impedance/dielectric spectroscopy (IS) and Surface Plasmon Resonance (SPR). Such platforms comprising Flow Injection Analysis (FIA) have been advanced to assess the interaction between selected (normal and malignant) cells and nano-patterned and/or chemically modified surfaces, as well as the impact of engineered nanoparticles, revealed by the related changes exhibited by cell membrane, morphology, adhesion and monolayer integrity. Besides experimental aspects dealing with measurement set-up, we will emphasize theoretical aspects related to: dielectric modeling. Aiming for a quantitative approach, microscopic models on dielectric behavior of ensembles of interconnected cells have been developed and their capabilities will be outlined within the presentation. Assessment of affinity reactions as revealed by dielectric/impedance assays of biointerfaces. Modeling the dynamics of the impedance in relation to the ˵quality″ of cell layer and sensor's active surface, this study presents further developments of our approach described in Analytical Chemistry, 2002. Data analysis. This issue is related to the following basic question: Are there ˵simple″ Biosensing Platforms? When coping with cellular platforms, either in suspension or immobilized (on filters, adhered on surfaces or entrapped, e.g., on using set-ups) there is an intrinsic nonlinear behavior of biological systems related to cellular mechanisms involved in sensing, i.e., adaptation to stimuli. This should not mean that when coping with living cells, stray effects might not also corrupt the measurement itself, introducing distinct dynamics. Besides targeted/specific process, analytical platforms might exhibit additional ones due to ˵stray influences″ that could include the effect of, e.g.: supporting matrix, nonspecific binding and temperature variation. Stray processes interfere with the desired ones and the measured data could display a non-monotonous behavior. [ABSTRACT FROM AUTHOR]

This article considers some features of metal nanoparticle fabrication in polymer matrices by ion implantation. This technological approach is very promising for the development of optical composite materials. The polymer layers were irradiated by silver ions with high doses up to 1017 ion/cm2. Optical density spectra of these composites demonstrate that the silver nanoparticles exhibit unusually weak and wide plasmon resonance spectra. The formation of silver nanoparticles in carbonized polymers by ion irradiation is reviewed. Based on the Mie theory, optical extinction spectra for metal particles in polymer and carbon matrices are simulated and compared with optical spectra for complex silver core–carbon shell nanoparticles. [ABSTRACT FROM AUTHOR]

Some predictions concerning the technological expansion for the optoelectronic imaging systems for the screening potent xenobiotics are made based on the analysis of the state-of-the-art ˵multivariate″ array technology. Emphasis is placed on the multiparameter aspect of such systems performance, in particular, the additional value of the scattered light under surface plasmon resonance conditions when forming chemical images for composite multicomponent media using the multisensor arrays. [ABSTRACT FROM AUTHOR]

For the development of field sensor systems with enough sensitivity and selectivity we develop photonic biosensors based on evanescent wave detection. Two technologies have been implemented in parallel: a plasmonic sensor for multianalyte real-time evaluation and an integrated optical nanosensor fabricated with silicon microelectronics technology. Both devices can be use as portable analyzers and have demonstrated an excellent performance in the immunological determination of chemical pollutants and in the detection of single mutations in DNA strands. [ABSTRACT FROM AUTHOR]

A definition of the term "surface plasmon resonance (SPR)" is presented. It refers to a biophysical method for detecting binding of ligands for the immobilization of antigens on a sensor chip surface in real-time. The signals are generated in SPR-based assays when the binding of a molecule to the biosensor surface creates a change in refractive index.