In the context of the extensive use of engineered nanomaterials (ENMs) in consumer products, industrial applications and nanomedicine, there is an important need of new methods for an exhaustive characterization of their physicochemical properties. Among them, surface hydrophobicity is considered as a key factor to be controlled, in particular for nanomedicine applications1,2. The proposed study demonstrates the proof-of-concept of an inexpensive characterization process, enabling the sorting of ENMs according to their hydrophobicity and surface charge, together with the classical characterization of size and shape. The detection platform is based on the use of a surface modified through plasma polymer and layer-by-layer polyelectrolyte deposition in order to generate areas of tuned surface properties to bind ENMs selectively by hydrophobic forces and electrostatic interactions. The key advantages of such a device is the decrease of time and assay costs thanks to the all-in-one characterization process and the multiplexing that could replace the use of different methods and expensive equipment to give equivalent results. In this way, the full characterization of NP could be expanded in all the areas covering NP-related applications.
Surface Enhanced Raman Spectroscopy is a powerful analytical technique that combines the excellent chemical specificity of Raman spectroscopy with the good sensitivity provided by the enhancement of the signal observed when a molecule is located on (or very close to) the surface of suitable nanostructured metallic materials. The availability of cheap, reliable and easy to use SERS substrates would pave the road to the development of bioanalytical tests that can be used in clinical practice. SERS, in fact, is expected to provide not only higher sensitivity and specificity, but also the simultaneous and markedly improved detection of several targets at the same time with higher speed compared to the conventional analytical methods. Here, we present the SERS activity of 2-D plasmonic crystals made by polymeric pillars embedded in a gold matrix obtained through the combination of soft-lithography and plasma deposition techniques on a transparent substrates. The use of a transparent support material allowed us to perform SERS detection from support side opening the possibility to use these substrates in combination with microfluidic devices. In order to demonstrate the potentialities for bioanalytical applications, we used our SERS active gold surface to detect the oxidation product of apomorphine, a well-known drug molecule used in Parkinson’s disease which has been demonstrated being difficult to study by traditional HPLC based approaches.
This paper describes a new multiplexed label-free biosensor. The detection technology is based on nanostructured gold-polymer surfaces. These surfaces support surface plasmon resonance modes that can be probed by a miniaturized optical setup. The optical characterization of the sensing chip shows the sensitivity and the limit-of-detection to refractive index changes. Moreover, by studying the progressive adhesion of molecular monolayers of polyelectrolytes, the decay of the plasmonic mode electric field above the surface has been reconstructed. A multiplexed label-free biosensing device is then described and characterized in terms of sensitivity, lateral resolution, and sensitivity to a model biological assay. The sensitivity in imaging mode of the device is of the order of 10 −6 refractive index units, while the measured lateral resolution is 6.25 μm within a field of view of several tenths of mm 2 , making the instrument unique in terms of multiplexing capability. Finally, the proof-of-concept application of the technology as a point-of-care diagnostic tool for an inflammatory marker is demonstrated.
A procedure for fabricating nanopatterned surfaces at the sub-500 nm scale comprising a hexagonal close packed array of bioadhesive gold nanoareas in a protein resistant matrix (PEO-like polymer), has been optimized. The surfaces were characterized by AFM analysis and their interaction with amino functionalised gold nanoparticles as models were investigated. The AFM images show the crystalline arrangement of nanopattern array and the localized adsorption of the H2N-Au nanoparticles in the bioadhesive nanoareas. A Surface Plasmon Resonance imaging (SPRi) system was used to assess the detection performances of these surfaces when employed as a transduction platform for studying biomolecule interactions. The investigated surfaces showed an enhancement of the affinity reaction efficiency with respect to the non structured surfaces. The obtained preliminary results show that nanostructuring the surfaces improve the binding site accessibility of the immobilized biological probes without significantly modifying the native biomolecule conformation.