Giacomo Dacarro

Macroscopic silica monoliths, AgNP/SiO2 (d ∼ 1 cm, mass ∼ 100 mg), were synthesized with embedded silver nanoparticles (AgNPs, d = 36 nm). Differently from the published materials based on AgNPs intended for disinfecting water, in AgNP/SiO2, the AgNPs are not on the material surface but incorporated in the body of the monoliths, with the aim of avoiding the possible release to water even under mechanical solicitations. However, the synthesized silica materials are sufficiently porous to allow the diffusion of H2O, O2, and H+, obtaining the slow, sustained oxidation of the AgNPs and the release of trace quantities of Ag+. 1×, 10×, and 100× AgNP/SiO2 monoliths were prepared, corresponding to 0.01, 0.1, and 1.0% w/w Ag content, which release Ag+ in the 0.008−0.064 ppm range (after 24 h, 20 °C) when the monoliths are immersed in water. Increased Ag+ release is observed at 37 °C (0.17 ppm, 24 h) and in acidic-buffered pH, with 0.62 ppm at pH 4.0 after 24 h and 0.12 ppm at pH 5.5 after 24 h. The microbicidal effect of the monoliths was verified by immersion in planktonic suspensions of Escherichia coli and Staphylococcus aureus. Reduction of cell viability was observed after 5 h, which significantly increased at 24 h, correlating with the Ag concentration in the monoliths: 98.88, 99.61, and 99.78% viability reduction was found in the case of S. aureus with monoliths at 0.01, 0.1, and 1.0 % w/w Ag, respectively, and 99.96, 99.98, and 99.99% viability reduction in the case of E. coli with 0.01, 0.1, and 1.0% w/w Ag, respectively. Moreover, the AgNP/SiO2 monoliths also displayed similar antibacterial efficacy when sealed in small paper sachets, suggesting their use as handy point-of-use immersion devices, similar to tea bags.

A new active composite film intended for bread packaging is described here. The active film has the aim of prolonging bread’s shelf life while avoiding the use of nanoparticles that, with very few exceptions, are a type of material not allowed by regulatory agencies like EFSA (European Food Safety Agency) and FDA (US Food and Drug Administration) in food contact materials. Moreover, the increasing consumer demand for natural and wholesome products, possibly “clean label”, and packaged in natural, non-petroleum-based materials has been taken into consideration. Accordingly, precursor materials from renewable sources were used to prepare the active film: pectin from citrus peel (PEC) and carboxymethyl cellulose (CMC) were used as the matrix, with oleic acid (OA) as plasticizer. Moreover, the bread preservative calcium propionate (CaP) was used as the crosslinker, and also zeolite microparticles loaded with silver ions (AgZ) were added to the films as an additional antimold agent. This strategy allows us to avoid the addition to bread of the now commonly used preservatives ethanol and calcium propionate, moving the latter to the packaging. Permeance measurements revealed excellent barrier properties against O₂ and CO₂, while the typical high water vapor permeance of polysaccharide films was mitigated by the non-hydrophilic OA plasticizer. Moreover, the quantities of Ag⁺ and CaP released in bread are low and below the limits imposed by regulatory agencies. The antimold activity of the films is excellent, with Aspergillus niger, Penicillium janthinellum, and wild-type Penicillim molds reduction on bread in the 99.20–99.95% range for the films containing only CaP and in the 99.97–99.998% range for the films containing both CaP and AgZ. Finally, the rheological properties of the film-forming solutions were investigated, demonstrating their potential application as coatings on natural packaging materials for bread, such as paper.

Prussian Blue nanoparticles (PBnps) are now popular in nanomedicine thanks to the FDA approval of PB. Despite the numerous papers suggesting or describing the in vivo use of PBnps, no studies have been carried out on the formation of a protein corona on the PBnp surface and its stabilizing role. In this paper, we studied qualitatively and quantitatively the corona formed by the most abundant protein of blood, human serum albumin (HSA). Cubic PBnps (41 nm side), prepared in citric acid solution at PB concentration 5 × 10⁻⁴ M, readily form a protein corona by redissolving ultracentrifuged PBnp pellets in HSA solutions, with C_HSA ranging from 0.025 to 7.0 mg/mL. The basic decomposition of PBnp@HSA was studied in phosphate buffer at the physiological pH value of 7.4. Increased stability with respect to uncoated PBnps was observed at all concentrations, but a minimum C_HSA value of 3.0 mg/mL was determined to obtain stability identical to that observed at serum-like HSA concentrations (35–50 mg/mL). Using a modified Lowry protocol, the quantity of firmly bound HSA in the protein corona (hard corona) was determined for all the C_HSA used in the PBnp@HSA synthesis, finding increasing quantities with increasing C_HSA. In particular, an HSA/PBnp number in the 1500–2300 range was found for C_HSA 3.0–7.0 mg/mL, largely exceeding the 180 HSA/PBnp value calculated for an HSA monolayer on a PBnp. Finally, the stabilization brought by the HSA corona allowed us to carry out pH-spectrophotometric titrations on PBnp@HSA in the 3.5-9-0 pH range, revealing a pKa value of 6.68 for the water molecules bound to the Fe³⁺ centers on the PBnp surface, whose deprotonation is responsible for the blue-shift of the PBnp band from 706 nm (acidic solution) to 685 nm (basic solution).

Microbial infection diseases are a major threat to human health and have become one of the main causes of mortality. The search for novel antimicrobial strategies is an important challenge for the scientific community, considering also the constant increase of antimicrobial resistance and the rise of new diseases. Among the new strategies to combat microbial infections, the photothermal effect seems to be one of the most promising. Hyperthermia is an effective and broad spectrum strategy for the removal of microbial infections. Among all of the strategies to reduce the diffusion of microbial infections, the preparation of antimicrobial surfaces seems of primary importance. In many cases, in fact, an infection can be diffused through surfaces just by touching them, or by inoculating microbes through an internalizable device, such as an implant, a prosthesis, or a catheter. In this review, we will summarize the recent advances in the preparation of photothermal antibacterial surfaces.

Detecting and quantifying micro- and nanoplastics (MNPs) in the environment is a crucial task that needs to be addressed as soon as possible by the scientific community. Many analytical techniques have been proposed, but a common agreement on analytical protocols and regulations still has to be reached. Nanomaterial-based techniques have shown promising results in this field. In this review, we focus on the recent results published on the use of plasmonic noble metal materials for the detection of MNPs. Plasmonic materials can be exploited in different ways due to their peculiar optical end electronic properties. Surface plasmon resonance, plasmon enhanced fluorescence, UV–Vis spectroscopy, and surface enhanced Raman scattering (SERS) will be considered in this review, examining the advantages and drawbacks of each approach.

A new dual mode antibacterial surface based on photothermally active Prussian blue nanoparticles and intrinsically antibacterial silver nanoparticles.

Surface-enhanced Raman scattering (SERS) is becoming widely used as an analytical tool, and the search for stable and highly responsive SERS substrates able to give ultralow detection of pollutants is a current challenge. In this paper we boosted the SERS response of Gold nanostars (GNS) demonstrating that their coating with a layer of silver having a proper thickness produces a 7-fold increase in SERS signals. Glass supported monolayers of these GNS@Ag were then prepared using simple alcoxyliane chemistry, yielding efficient and reproducible SERS chips, which were tested for the detection of molecules representative of different classes of pollutants. Among them, norfloxacin was detected down to 3 ppb, which is one of the lowest limits of detection obtained with this technique for the analyte.

In this paper, we report on the preparation of Imidazole-functionalized glass surfaces, demonstrating the ability of a dinuclear Cu(II) complex of a macrocyclic ligand to give a “cascade” interaction with the deprotonated forms of grafted imidazole moieties. In this way, we realized a prototypal example of an antimicrobial surface based on a supramolecular approach, obtaining a neat microbicidal effect using low amounts of the described copper complex.