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Diatomaceous earth, or diatomite, is produced through the accumulation of diatom (Bacillariophyceae) skeletons (i.e. cell walls called frustules) made of amorphous silica. The porous, highly symmetrical structure and microscopic size of diatom cell walls make them ideal constituents of sensing devices and analytical chips. Here, we propose chemical methods to purify diatom frustules extracted from diatomaceous earth. Using photo deposition techniques, we grow gold nanoparticles on the surface of diatom skeletons and within the pores of the skeletons, where the size and density of nanoparticles can be controlled by changing the parameters of the synthesis. Resulting devices have an internal porous structure that can harvest molecules from a solution, and an external shell of gold nanoparticles that amplifies the electromagnetic field generated by the measurement laser in Raman or other spectroscopies. The combination of these effects enables the analysis of biological specimens, chemical analytes and pollutants in extremely low abundance ranges. The devices were demonstrated in the analysis of Bovine Serum Albumin in water with a concentration of 100 aM, and mineral oil with a concentration of 50 ppm. Keywords: Diatomite, Diatoms, Photo-deposition, Gold nanoparticles, SERS, Bio-sensors

Electroless deposition on patterned silicon substrates enables the formation of metal nanomaterials with tight control over their size and shape. In the technique, metal ions are transported by diffusion from a solution to the active sites of an autocatalytic substrate where they are reduced as metals upon contact. Here, using diffusion limited aggregation models and numerical simulations, we derived relationships that correlate the cluster size distribution to the total mass of deposited particles. We found that the ratio ξ between the rates of growth of two different metals depends on the ratio γ between the rates of growth of clusters formed by those metals through the linearity law ξ = 14(γ − 1). We then validated the model using experiments. Different from other methods, the model derives k using as input the geometry of metal nanoparticle clusters, decoded by SEM or AFM images of samples, and a known reference.

Porous silicon is a nano material in which pores with different sizes, densities and depths are infiltrated in conventional silicon imparting it augmented properties including biodegradability, biocompatibility, photoluminescence. Here, we realized porous silicon substrates in which the pore size and the fractal dimension were varied over a significant range. We loaded the described substrates with a PtCl(O,O'-acac)(DMSO) antitumor drug and determined its release profile as a function of pore size over time up to 15days. We observed that the efficacy of delivery augments with the pore size moving from small (~8nm, efficiency of delivery ~0.2) to large (~55nm, efficiency of delivery ~0.7). Then, we verified the adhesion of MCF-7 breast cancer cells on the described substrates with and without the administration of the antitumor drug. This permitted to decouple and understand the coincidental effects of nano-topography and a controlled dosage of drugs on cell adhesion and growth. While large pore sizes guarantee elevated drug dosages, large fractal dimensions boost cell adhesion on a surface. For the particular case of tumor cells and the delivery of an anti-tumor drug, substrates with a small fractal dimension and large pore size hamper cell growth. The competition between nano-topography and a controlled dosage of drugs may either accelerate or block the adhesion of cells on a nanostructured surface, for applications in tissue engineering, regenerative medicine, personalized lab-on-a-chips, and the rational design of implantable drug delivery systems. Display Omitted We realized porous silicon substrates with a varying pore size and fractal dimension.We loaded the substrates with an antitumor drug and determined its release profile over time.We verified the adhesion of MCF-7 cancer cells on the porous substrates.We decoupled the effects of nano-topography and drug delivery on cell adhesion.Large pore sizes boost drug release, large fractal dimensions accelerate cell adhesion.

Super-hydrophobic (SH) surfaces are bio-inspired, nanotechnology artifacts which feature a reduced friction coefficient whereby they can be used for a number of very practical applications including, on the medical side, the manipulation of biological solutions. These surfaces can be combined with bio-photonic devices to obtain an integrated lab-on-a-chip system where, on a first stage, the SH surface would vehicle or transport the analytes of interest into a small area and, on a second stage, the bio-sensors would permit, in that area, the detection of the solute with the resolution of a single molecule. This novel diagnostic modality offers realistic possibilities for the early detection of cancers. Nevertheless, as it stands, the device still suffers from the severe disadvantage that the exact final position of the solute, upon evaporation, is unpredictable, and thus the localization and recognition of few molecules would be impractical. Conventional SH surfaces typically comprise micro pillars combined to form a regular hexagonal motif. Here, the periodicity of those pillars was broken introducing artificial gradients of wettability over the surface. In doing so, some regions are rendered more hydrophilic than others and, on account of this, a solute would preferentially target these hydrophilic regions upon evaporation. In this work, such non regular geometries were realized and used to condense diluted Rhodamine solutions in a small area. Randomly distributed silver nano aggregates, conveniently positioned upon the micropillars, permitted the identification of few molecules using enhanced Fourier transform infrared spectroscopy (FTIR) spectroscopy.

The study and the comprehension of the mechanism of cell adhesion and cell interaction with a substrate is a key point when biology and medicine meet engineering. This is the case of several biomedical applications, from regenerative medicine and tissue engineering to lab on chip and many others, in which the realization of the appropriate artificial surface allows the control of cell adhesion and proliferation.In this context, we aimed to design and develop a fabrication method of mesoporous (MeP) silicon substrates, doped with gold nanoparticles, in which we combine the capability of porous surfaces to support cell adhesion with the SERS capabilities of gold nanoparticles, to understand the chemical mechanisms of cell/surface interaction.MeP Si surfaces were realized by anodization of a Si wafer, creating the device for cell adhesion and growth. Gold nanoparticles were deposited on porous silicon by an electroless technique. We thus obtained devices with superior SERS capabilities, whereby cell activity may be controlled using Raman spectroscopy. MCF-7 breast cancer cells were cultured on the described substrates and SERS maps revealing the different expression and distribution of adhesion molecules were obtained by Raman spectroscopic analyses. Display Omitted designing and developing of a fabrication method of mesoporous (MeP) silicon substrates decorated with gold nanoparticlesthese devices are able to support cell adhesion and proliferation and simultaneously they works as SERS substratesSERS Raman analysis of cells cultured on MeP Si substrates provide indication about cells behaviour on them.

Recent progresses in nanotechnology fabrication gives the opportunity to build highly functional nano-devices. 3D structures based on noble metals or covered by them can be realized down to the nano-scales, obtaining different devices with the functionalities of plasmonic nano-lenses or nano-probes. Here, nano-cones decorated with silver nano-grains were fabricated using advanced nano-fabrication techniques. In fabricating the cones, the angle of the apex was varied over a significant range and, in doing so, different geometries were realized. In depositing the silver nano-particles, the concentration of solution was varied, whereby different growth conditions were realized. The combined effect of tip geometry and growth conditions influences the size and distribution of the silver nano grains. The tips have the ability to guide or control the growth of the grains, in the sense that the nano-particles would preferentially distribute along the cone, and especially at the apex of the cone, with no o minor concentration effects on the substrate. The arrangement of metallic nano-particles into three-dimensional (3D) structures results in a Surface Enhanced Raman Spectroscopy (SERS) device with improved interface with analytes compared to bi-dimensional arrays of metallic nanoparticles. In the future, similar devices may find application in microfluidic devices, and in general in flow chambers, where the system can be inserted as to mimic a a nano-bait, for the recognition of specific biomarkers, or the manipulation and chemical investigation of single cells directly in native environments with good sensitivity, repeatability and selectivity.

Silver nanoparticles (NPs) aggregates with an overall size in the nano meter range were fabricated employing non conventional electroless techniques. The structure of the aggregates was analyzed through direct SEM and AFM imaging; space-frequency based variables, including fractal dimension, were extracted in order to yield a quantitative measurement of the topography of the systems at study. These observations were explained within the framework of diffusion limited aggregation (DLA). DLA theory founds upon the paradigm that, in the limit of very fast chemical reactions, diffusion is the sole driving force that regulates the dynamics of aggregation of NPs. The mathematical model confirmed the experimental findings whereby the fractal dimension of the clusters is size dependent, that is, larger systems are more discontinuous than smaller. The model would also predict that, under certain conditions, a characteristic length exists beyond which the fractal dimension is constant. DLA theory is consistent and predictive in nature, and may be of valuable help in designing devices that utilize rough metal surfaces and the derived effects thereof, including SERS substrates.

Superhydrophobic surfaces were fabricated comprising cylindrical micro-pillars arranged in a regular hexagonal lattice. These structures are hierarchical in that the pillars incorporate, on the top, nanoporous silicon films. In sight of the superhydrophobicity of the system, the devices retain the ability of manipulating and concentrating diluted biological solutions, while, on account of the nanoporous films, they would efficiently filter the biological content of such solutions. The major advance, here, is the simultaneous use of the properties above, and thus important applications are envisioned where extremely small quantities of bio-markers are efficiently extracted from serum and analyzed employing conventional and well assessed spectroscopy techniques. Ultra low concentrated small Rhodamine molecules were here efficiently analyzed using FTIR spectroscopy techniques, thus demonstrating that these devices are effective.

The detection of a few molecules in a highly diluted solution is of paramount interest in fields including biomedicine, safety and eco-pollution in relation to rare and dangerous chemicals. Nanosensors based on plasmonics are promising devices in this regard, in that they combine the features of high sensitivity, label-free detection and miniaturization. However, plasmonic-based nanosensors, in common with general sensors with sensitive areas on the scale of nanometres, cannot be used directly to detect molecules dissolved in femto- or attomolar solutions. In other words, they are diffusion-limited and their detection times become impractical at such concentrations. In this Article, we demonstrate, by combining super-hydrophobic artificial surfaces and nanoplasmonic structures, that few molecules can be localized and detected even at attomolar (10−18 mol l−1) concentration. Moreover, the detection can be combined with fluorescence and Raman spectroscopy, such that the chemical signature of the molecules can be clearly determined.

Exosomes are very small vesicles that are shed from a variety of cell types. They are present in body fluids comprising blood, urine and ascites, and they hold the potential to serve as indicators in the diagnosis, prognosis and surveillance of a variety of health conditions. In consideration of this, there is broad interest worldwide in deriving and understanding their biochemical composition. Here, small drops of solutions containing exosomes, isolated from either healthy (CCD841-CoN) or tumor (HCT116) colon cells, were manipulated using super-hydrophobic surfaces (SHSs) decorated with nano-geometry based photonics structures. SHSs are surfaces with superior properties, including a reduced friction coefficient, on account of which they can be used to control diluted solutions of biological or medical interest. The combination of this technology with optical resonance phenomena, open up terrific opportunities in the detection, analysis or characterization of biological compounds. Therefore, exosomes were conveniently concentrated and conveyed onto the Surface Enhanced Raman Spectroscopy (SERS) active areas of the substrate, whereby they were analyzed and characterized with extreme precision. Results indicate a difference in the concentration of some biological compounds, and namely: exosomes derived from healthy cells exhibit higher intensities of the peaks corresponding to lipids vibrations, while exosomes extracted from tumor cell lines exhibit a richer RNA content.

Micro and nano-patterned devices were fabricated which disclose the possibility of concentrating, localizing, detecting and thus analyzing with unprecedented accuracy few molecules (at the limit a single molecule) of biological and medical interest. Important applications are envisioned where proteins poorly concentrated in blood are detected thus (early) revealing the appearance of diseases. The major advance of the paper is that it combines micro/nano-fabrication and spectroscopical nano-optics based techniques to study and individualize the biomolecules at study. Super hydrophobic surface would concentrate the diluted solution into a small area whereas spectroscopical nano-optics techniques would gather the molecular/chemical information of the residual solute. Fluorescence and SERS techniques were used to analyze Rhodamine molecules initially highly diluted (10^-^1^8M).