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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.

Diatom shells are a natural, theoretically unlimited material composed of silicon dioxide, with regular patterns of pores penetrating through their surface. For their characteristics, diatom shells show promise to be used as low cost, highly efficient drug carriers, sensor devices or other micro-devices. Here, we demonstrate diatom shells functionalized with gold nanoparticles for the harvesting and detection of biological analytes (bovine serum albumin—BSA) and chemical pollutants (mineral oil) in low abundance ranges, for applications in bioengineering, medicine, safety, and pollution monitoring. Electronic supplementary material The online version of this article (10.1186/s11671-018-2507-4) contains supplementary material, which is available to authorized users.

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.

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 ability to manipulate matter to create non-conventional structures is one of the key issues of material science. The understanding of assembling mechanism at the nanoscale allows us to engineer new nanomaterials, with physical properties intimately depending on their structure. This paper describes new strategies to obtain and characterise metal nanostructures via the combination of a top-down method, such as electron beam lithography, and a bottom-up technique, such as the chemical electroless deposition. We realised silver nanoparticle aggregates within well-defined patterned holes created by electron beam lithography on silicon substrates. The quality characteristics of the nanoaggregates were verified by using scanning electron microscopy and atomic force microscopy imaging. Moreover, we compared the experimental findings to molecular dynamics simulations of nanoparticles growth. We observed a very high dependence of the structure characteristics on the pattern nanowell aspect ratio. We found that high-quality metal nanostructures may be obtained in patterns with well aspect ratio close to one, corresponding to a maximum diameter of 50 nm, a limit above which the fabricated structures become less regular and discontinuous. When regular shapes and sizes are necessary, as in nanophotonics, these results suggest the pattern characteristics to obtain isolated, uniform and reproducible metal nanospheres.

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.

Surface-enhanced Raman scattering (SERS) substrates were fabricated using electro-plating and e-beam lithography techniques. Nano-structures were obtained comprising regular arrays of gold nanoaggregates with a diameter of 80 nm and a mutual distance between the aggregates (gap) ranging from 10 to 30 nm. The nanopatterned SERS substrate enabled to have better control and reproducibility on the generation of plasmon polaritons (PPs). SERS measurements were performed for various proteins, namely bovine serum albumin (BSA), myoglobin, ferritin, lysozyme, RNase-B, α-casein, α-lactalbumin and trypsin. Principal component analysis (PCA) was used to organize and classify the proteins on the basis of their secondary structure. Cluster analysis proved that the error committed in the classification was of about 14%. In the paper, it was clearly shown that the combined use of SERS measurements and PCA analysis is effective in categorizing the proteins on the basis of secondary structure.

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).