Fluorogenic Hyaluronan Nanogels Track Individual Early Protein Aggregates Originated under Oxidative Stress.

Proteins are broadly versatile biochemical materials, whose functionality is tightly related to their folding state. Native folding can be lost to yield misfolded conformations, often leading to formation of protein oligomers, aggregates, and biomolecular phase condensates. The fluorogenic hyaluronan HA-RB, a nonsulfonated glycosaminoglycan with a combination of polyanionic character and of hydrophobic spots due to rhodamine B dyes, binds to early aggregates of the model protein cytoplasmic glyceraldehyde-3-phosphate dehydrogenase 1 from Arabidopsis thaliana (AtGAPC1) since the very onset of the oligomeric phase, making them brightly fluorescent. This initial step of aggregation has, until now, remained elusive with other fluorescence- or scattering-based techniques. The information gathered from nanotracking (via light-sheet fluorescence microscopy) and from FCS in a confocal microscope converges to highlight the ability of HA-RB to bind protein aggregates from the very early steps of aggregation and with high affinity. Altogether, this fluorescence-based approach allows one to monitor and track individual early AtGAPC1 aggregates in the size range from 10 to 100 nm with high time (∼10-2 s) and space (∼250 nm) resolution.

Investigation of the impact of additive manufacturing techniques on the acoustic performance of a coiled-up resonator.

Acoustic metamaterials (AMMs) offer innovative solutions for physics and engineering problems, allowing lighter, multiphysics, and sustainable systems. They are usually studied analytically or numerically and then tested on prototypes. For this reason, additive manufacturing (AM) techniques are a popular way of quickly realising AMMs' innovative geometrical designs. However, AM parameters are often standardised without considering the specific issues of each AMM geometrical shape, leading to a possible mismatch between the analytical (or numerical) and experimental results. In this study, a simple AMM-a coiled-up resonator-has been produced with different AM technologies [fused deposition modeling (FDM), stereolithography (SLA), and selective laser melting and materials (polylactic acid, polyethylene terephthalate glycol, resin, flexible resin, and stainless steel). The sound absorption performance of these samples has been measured in two research labs in Italy and compared with the analytical and numerical calculations. This permitted the identification of the best combinations of AM technologies, their setup, and materials matching the expected results. The SLA/resin combination performed better overall; however, cheaper and more easily manageable samples made with FDM and polyethylene terephthalate glycol can achieve the same acoustic performance through the optimal AM printing setup. It is expected that this methodology could also be replicated for other AMMs.

Influence of thermal deformations on sound absorption of three-dimensional printed metamaterials.

Acoustic metamaterials (AMMs) are designed with complex geometrical shapes to obtain unconventional sound-absorbing performances. As additive manufacturing is particularly suited to print complex structures in a more straightforward and controllable way, AMMs often exploit three-dimensional (3-D) printing techniques. However, when exposed to different temperature conditions, such structures can be affected by geometrical deformations, especially when they are polymer-based. This can cause a mismatch between the experimental data and the expected theoretical performance; therefore, it is important to take thermal effects into account. The present paper investigates the influence of thermal deformations on the sound absorption of three geometries: a coplanar spiral tube, a system with double coiled resonators, and a neck-embedded resonator. Measurements were performed on each 3-D printed specimen in the impedance tube after the samples had been placed in a climate chamber to modify the temperature settings (T = 10-50 °C). Numerical models, validated on the measurements, were employed to quantify the geometrical deformation of AMM structures through a multiphysics approach, highlighting the effects of thermal stress on the acoustic behavior. The main outcomes prove that the frequency shifts of sound absorption peaks depend on temperature configurations and follow exponential regressions, in accordance with previous literature on polymeric materials.

Static quenching upon adduct formation: a treatment without shortcuts and approximations.

Luminescence quenching is a process exploited in transversal applications in science and technology and it has been studied for a long time. The luminescence quenching mechanisms are typically distinguished in dynamic (collisional) and static, which can require different quantitative treatments. This is particularly important - and finds broad and interdisciplinary application - when the static quenching is caused by the formation of an adduct between the luminophore - at the ground state - and the quencher. Due to its nature, this case should be treated starting from the well-known law of mass action although, in specific conditions, general equations can be conveniently reduced to simpler ones. A proper application of simplified equations, though, can be tricky, with frequent oversimplifications taking to severe errors in the interpretation of the photophysical data. This tutorial review aims to (i) identify the precise working conditions for the application of the simplified equations of static quenching and to (ii) provide general equations for broadest versatility and applicability. The latter equations can be used even beyond the sole case of pure quenching, i.e., in the cases of partial quenching and even luminescence turn-on. Finally, we illustrate different applications of the equations via a critical discussion of examples in the field of sensing, supramolecular chemistry and nanotechnology.

A Selective Ratiometric Fluorescent Probe for No-Wash Detection of PVC Microplastic.

Microplastics (MP) are micrometric plastic particles present in drinking water, food and the environment that constitute an emerging pollutant and pose a menace to human health. Novel methods for the fast detection of these new contaminants are needed. Fluorescence-based detection exploits the use of specific probes to label the MP particles. This method can be environmentally friendly, low-cost, easily scalable but also very sensitive and specific. Here, we present the synthesis and application of a new probe based on perylene-diimide (PDI), which can be prepared in a few minutes by a one-pot reaction using a conventional microwave oven and can be used for the direct detection of MP in water without any further treatment of the sample. The green fluorescence is strongly quenched in water at neutral pH because of the formation dimers. The ability of the probe to label MP was tested for polyvinyl chloride (PVC), polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polystyrene (PS), poly methyl methacrylate (PMMA) and polytetrafluoroethylene (PTFE). The probe showed considerable selectivity to PVC MP, which presented an intense red emission after staining. Interestingly, the fluorescence of the MP after labeling could be detected, under excitation with a blue diode, with a conventional CMOS color camera. Good selectivity was achieved analyzing the red to green fluorescence intensity ratio. UV-Vis absorption, steady-state and time-resolved fluorescence spectroscopy, fluorescence anisotropy, fluorescence wide-field and confocal laser scanning microscopy allowed elucidating the mechanism of the staining in detail.