Challenges and opportunities for SERS in the infrared: materials and methods

In the wake of a global, heightened interest towards biomarker and disease detection prompted by the SARS-CoV-2 pandemic, surface enhanced Raman spectroscopy (SERS) positions itself again at the forefront of biosensing innovation. But is it ready to move from the laboratory to the clinic? This review presents the challenges associated with the application of SERS to the biomedical field, and thus, to the use of excitation sources in the near infrared, where biological windows allow for cell and through-tissue measurements. Two main tackling strategies will be discussed: (1) acting on the design of the enhancing substrate, which includes manipulation of nanoparticle shape, material, and supramolecular architecture, and (2) acting on the spectral collection set-up. A final perspective highlights the upcoming scientific and technological bets that need to be won in order for SERS to stably transition from benchtop to bedside

Silica Meets Tannic Acid: Designing Green Nanoplatforms for Environment Preservation

Hybrid tannic acid-silica-based porous nanoparticles, TA-SiO(2) NPs, have been synthesized under mild conditions in the presence of green and renewable tannic acid biopolymer, a glycoside polymer of gallic acid present in a large part of plants. Tannic acid (TA) was exploited as both a structuring directing agent and green chelating site for heavy metal ions recovery from aqueous solutions. Particles morphologies and porosity were easily tuned by varying the TA initial amount. The sample produced with the largest TA amount showed a specific surface area an order of magnitude larger than silica nanoparticles. The adsorption performance was investigated by using TA-SiO(2) NPs as adsorbents for copper (II) ions from an aqueous solution. The effects of the initial Cu(2+) ions concentration and the pH values on the adsorption capability were also investigated. The resulting TA-SiO(2) NPs exhibited a different adsorption behaviour towards Cu(2+), which was demonstrated through different tests. The largest adsorption (i.e., ~50 wt% of the initial Cu(2+) amount) was obtained with the more porous nanoplatforms bearing a higher final TA content. The TA-nanoplatforms, stable in pH value around neutral conditions, can be easily produced and their use would well comply with a green strategy to reduce wastewater pollution

A microfluidic platform to design nanostructures with improved multi-modal imaging properties

Nowadays, researchers are making many efforts in the medical field leading to new therapy and diagnosis methods exploiting opportunities given by nanotechnology innovation. For example, the combination of different imaging modalities can give the opportunity to obtain morphological and functional information simultaneously, providing a more accurate diagnosis. This advancement can be reached through the use of multimodal tracers and nanotechnology-based solutions allowing the simultaneous delivery of different diagnostic compounds and their safe administration for multimodal imaging acquisition. In this way is possible to protect the cargo molecules. Furthermore, a fundamental aspect is due to a proper design of the nanovectors used, correlating it with respect to the target purpose. Among different materials and processes available, nanoprecipitation is a consolidate method for polymeric nanoparticle production and its implementation in microfluidics can further improve the control over final product features accelerating its potential clinical translation. In this scenario, a Hydrodynamic Flow Focusing (HFF) approach is proposed and investigated as a production route to synthesis through a ONE-STEP process pegylated crosslinked Hyaluronic Acid NanoParticles (PEG-cHANPs). A feasibility study has been conducted to define the principal guidelines in terms of size and stability for the produced nanosystem. Based on the obtained results, a set of conditions has been elected as “gold conditions” and used in the following parts. To exploit the versatility of our microfluidic (µF) platform, the ONE-STEP process has been implemented to generate more complex structures with differents loaded agent. First, we have demonstrated that a homogeneous population of NPs with an average size of 140 nm is obtained and Gadolinium-based contrast agent (Gd-DTPA CA) and ATTO488 compounds are co-encapsulated simultaneously during the ONE-STEP process The results showed that the obtained architectures can be used as multimodal Magnetic Resonance Imaging (MRI)/Optical imaging probe. Furthermore, in accordance with the Hydrodenticity concept, a boosting of the T1 values is obtained with respect to the free Gd-DTPA. Thereafter, we have synthesized hybrid materials combining SiO2 and HA-PEG hydrogels loaded with Gd-DTPA as new MRI probes. Pre-synthetized SiO2 NPs have been added to the solvent phase during the ONE-STEP process. In this case, silica nanoparticles act as a templating agent, interfering with the nanoprecipitation step during the HFF. Resulting hybrid nanosystems have been characterized in terms of size, morphology and T1 values. Intending to develop new probes for combining MRI/Near-Infrared Fluorescence Imaging (NIRF), we explore the possibility to co-encapsulate Gd-DTPA and Indocyanine Green (ICG) in the ONE-STEP process for PEG-cHANPs production. ICG is the only NIRF dye approved by Food and Drug Administration, but its use is restricted by its low stability in biological media. Here we report a stability study of ICG regarding its interaction with the materials involved in PEG-cHANPs production and preliminary characterization of PEG-cHANPs loaded with ICG as Reactive Oxygen Species generators. Preliminary in-vitro tests with different cells lines have been conducted to evaluate the PEG-cHANPs-Gd-DTPA-ATTO488 behaviour for biological application

Removal of sulfanilamide by tailor-made magnetic metal-ceramic nanocomposite adsorbents

Three tailor-made magnetic metal-ceramic nanocomposites, obtained from zeolite A (ZA1 and ZA2) and a natural clinoptilolite (LB1), have been used as adsorbents to remove sulfanilamide (SA), a sulfonamide antibiotic of common use, from water.A patented process for the synthesis of nanocomposites has been suitably modified to maximize the efficiency of the SA removal, as well as to extend the applicability of the materials.The role played by the main process parameters (kinetic, pH, initial concentration of SA) has been characterized. The significant effect of the pH on the SA removal has been explained identifying two possibly coexisting mechanisms of SA adsorption, based on polar and hydrophobic interactions, respectively.The adsorption kinetics have been in all cases described by the pseudo second-order model. The adsorption isotherms obtained with ZA1 have been satisfactorily described by the Langmuir model, suggesting a monolayer adsorption of SA on the magnetic nanocomposites resulting from a uniform surface energy. The isotherms obtained with LB1 could be described by a more complex approach, deriving by the additive superposition of Langmuir and Sips models.In order to ensure an effective removal of the antibiotic and a proper recycle of the magnetic adsorbents, a sustainable regeneration procedure of the exhausted adsorbent has been developed, based on the treatment with a dilute solution of NaOH

Magnetic clustering of weakly interacting Ni-ions in Ni-exchanged zeolites

Divalent Nickel cations were incorporated in two commercial zeolites (Na-A zeolite and Na-X zeolite) by a process of ionic exchange marginally affecting structure, morphology and porosity of the host materials, as verified by XRD, HRTEM and physisorption measurements. Comparable amounts of magnetic ions were introduced (4.80 wt.% in Na-A zeolite and 6.20 wt.% in Na-X zeolite), as checked by AAS and TGA. Magnetic measurements were done between 2 and 300 K using a SQUID magnetometer up to 70 kOe. The initial susceptibility follows the Curie-Weiss law with Curie temperatures θ of 10.3 and 11.5 K. The effective magnetic moments on Ni2+ ions suggest almost complete quenching of the angular momentum. No long-range magnetic order is found below θ; however, FC/ZFC magnetization curves indicate the formation of superparamagnetic clusters of magnetic ions with blocking temperature of about 6.5 K in both zeolites. Cluster size, average number of clustered ions, effective anisotropy of clusters are evaluated. A comprehensive picture of all magnetic effects taking place over the whole temperature range is drawn by combining magnetic, structural and morphological dat

Bioinspired hybrid eumelanin-TiO2 antimicrobial nanostructures: the key role of organo-inorganic frameworks in tuning eumelanin's biocide action mechanism through membrane interaction

Hybrid TiO2/eumelanin nanostructures showed a peculiar biocide mechanism against Gram(−) bacteria, based on the ROS action, produced by eumelanin degradation under visible light irradiation, and the interactions with external bacterial membranes