Summary Background In vitro sunscreen tests are diffusively used to test both the sun protection factor (SPF) and the photo-stability of filters. Spectrophotometric measurements of the absorbance of ...ultraviolet radiations through a sunscreen applied on a suitable substrate allow a rapid evaluation of its protection factor both at short and long wavelength ultraviolet radiation (UVB and UVA). Objectives The objective of this study has been to demonstrate if Teflon can be adopted as substrate both for SPF evaluation and photo-stability tests. Moreover, we have investigated if there is a correspondence between in vitro SPF measurements and values reported by manufacturers on sunscreens. Material and methods Teflon has been used to perform several photo-stability tests by irradiating the filters with different wavebands and analyzing the combined effect of UV and infrared (IR) light. Similar analyses have been carried out using PMMA Plates, which is the standard substrate for UVA in vitro test. Results We have demonstrated that it is possible to establish a good correspondence between in vitro SPF and values reported by manufacturers on sunscreens. We have also verified that the in vitro /label SPF correlation curve depends on the quantity of product applied while this does not seem to be true for other parameters like Critical Wavelength and UVA ratio . With regard to photo-stability studies, our results indicate for the first time that IR irradiation may have a role on photo-degradation. Conclusions The results show that there is a good correlation between the in vitro SPF determined by the present method and the SPF reported by the manufacturer. The compatibility of the results obtained using Teflon and PMMA Plates demonstrates that Teflon can be utilized for both SPF determination and photo-stability tests.
Nanoporous gold can be exploited as plasmonic material for enhanced spectroscopy both in the visible and in the near-infrared spectral regions. In particular, the peculiar morphology of such a ...substrate leads to a higher field confinement with respect to conventional plasmonic materials. This property can be exploited to achieve extremely high sensitivity to the changes in environmental conditions, making it an interesting tool for the development of sensors and biosensors. Here, we compared the sensitivity of a plasmonic resonator made of nanoporous gold with a similar structure made of homogeneous gold. To assess the enhanced sensitivity the same stoichiometric quantity of dielectric material was deposited via Atomic Layer Deposition onto the two considered structures. Experimental results proved the higher sensitivity was achievable using nanoporous gold. In particular, such 3D nanoporous structures can be proposed as a promising sensing platform in the near-infrared with a sensitivity over 4.000 nm/RIU.
Aptamers that undergo conformational changes upon small-molecule recognition have been shown to gate the ionic flux through nanopores by rearranging the charge density within the aptamer-occluded ...orifice. However, mechanistic insight into such systems where biomolecular interactions are confined in nanoscale spaces is limited. To understand the fundamental mechanisms that facilitate the detection of small-molecule analytes inside structure-switching aptamer-modified nanopores, we correlated experimental observations to theoretical models. We developed a dopamine aptamer-functionalized nanopore sensor with femtomolar detection limits and compared the sensing behavior with that of a serotonin sensor fabricated with the same methodology. When these two neurotransmitters with comparable mass and equal charge were detected, the sensors showed an opposite electronic behavior. This distinctive phenomenon was extensively studied using complementary experimental techniques such as quartz crystal microbalance with dissipation monitoring, in combination with theoretical assessment by the finite element method and molecular dynamic simulations. Taken together, our studies demonstrate that the sensing behavior of aptamer-modified nanopores in detecting specific small-molecule analytes correlates with the structure-switching mechanisms of individual aptamers. We believe that such investigations not only improve our understanding of the complex interactions occurring in confined nanoscale environments but will also drive further innovations in biomimetic nanopore technologies.
Förster resonance energy transfer (FRET) between fluorescent dyes is a frequently applied technique for analyzing concentrations and conformations of biomolecules. Optimizing FRET by controlled ...dye-surface functionalization is an important requirement to develop sensors based on surface–biomolecule interactions. Here, we investigate the silanization of silica with aminosilanes ((3-aminopropyl)triethoxysilane, APTES) and their subsequent functionalization with commercial organic fluorophores (ATTO-550 and ATTO-647N) for controlling the fluorescence intensity and FRET interaction between the dyes. Owing to the growing application of aluminum in plasmonics and the possibility to enhance FRET with aluminum nanostructures, we used plasma-enhanced atomic layer deposition (PEALD) to cover aluminum layers with thin silica coatings (∼4 nm) as a prototypical system to apply and characterize our controlled APTES–dye functionalization procedure. Detailed spectroscopic and fluorescence imaging analyses were used to optimize the silanization, control the dye functionalization, and rule out aluminum-related fluorescence quenching. The optimized protocol was then used to attach both dyes on the same surface, which enabled efficient FRET. As PEALD is in principle applicable to different substrates, we believe that our controlled FRET-functionalization approach may be adaptable to many other surfaces and nanostructures and may become a useful tool to advance the development of fluorescence biosensors.
Nanofluidic channels in a membrane represent a promising avenue for harnessing blue energy from salinity gradients, relying on permselectivity as a pivotal characteristic crucial for inducing ...electricity through diffusive ion transport. Surface charge emerges as a central player in the osmotic energy conversion process, emphasizing the critical significance of a judicious selection of membrane materials to achieve optimal ion permeability and selectivity within specific channel dimensions. Alternatively, here we report a field-effect approach for in situ manipulation of the ion selectivity in a nanopore. Application of voltage to a surround-gate electrode allows precise adjustment of the surface charge density at the pore wall. Leveraging the gating control, we demonstrate permselectivity turnover to enhanced cation selective transport in multipore membranes, resulting in a 6-fold increase in the energy conversion efficiency with a power density of 15 W/m2 under a salinity gradient. These findings not only advance our fundamental understanding of ion transport in nanochannels but also provide a scalable and efficient strategy for nanoporous membrane osmotic power generation.
We demonstrate the generation of far-field propagating optical beams with a desired orbital angular momentum by using a smooth optical-mode transformation between a plasmonic vortex and free-space ...Laguerre–Gaussian modes. This is obtained by means of an adiabatically tapered gold tip surrounded by a spiral slit. The proposed physical model, backed up by the numerical study, brings about an optimized structure that is fabricated by using a highly reproducible secondary electron lithography technique. Optical measurements of the structure excellently agree with the theoretically predicted far-field distributions. This architecture provides a unique platform for a localized excitation of plasmonic vortices followed by its beaming.
The ability to monitor electrogenic cells accurately plays a pivotal role in neuroscience, cardiology and cell biology. Despite pioneering research and long-lasting efforts, the existing methods for ...intracellular recording of action potentials on the large network scale suffer limitations that prevent their widespread use. Here, we introduce the concept of a meta-electrode, a planar porous electrode that mimics the optical and biological behaviour of three-dimensional plasmonic antennas but also preserves the ability to work as an electrode. Its synergistic combination with plasmonic optoacoustic poration allows commercial complementary metal-oxide semiconductor multi-electrode arrays to record intracellular action potentials in large cellular networks. We apply this approach to measure signals from human-induced pluripotent stem cell-derived cardiac cells, rodent primary cardiomyocytes and immortalized cell types and demonstrate the possibility of non-invasively testing a variety of relevant drugs. Due to its robustness and easiness of use, we expect the method will be rapidly adopted by the scientific community and by pharmaceutical companies.
DNA swingarms enable the efficient and reliable translocation of multiple optical elements along a shared DNA origami track. Na Liu et al. demonstrate in their Research Article (e202213992) that the ...dynamic rearrangement of AuNPs with large leaps in space can be facilitated by swinging motion, which is substantiated by distinct optical response changes.
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