Surface-enhanced Raman scattering (SERS) is a widely used technique for drug detection due to high sensitivity and molecular specificity. The applicability and selectivity of SERS in the detection of ...specific drug molecules can be improved by gathering information on the specific interactions occurring between the molecule and the metal surface. In this work, multilayer gold-silver bimetallic nanorods (Au@Ag@AuNRs) have been prepared and used as platforms for SERS detection of specific drugs (namely promethazine, piroxicam, furosemide and diclofenac). The analysis of SERS spectra provided accurate information on the molecular location upon binding and gave some insight into molecule-surface interactions and selectivity in drug detection through SERS.
Most targeting strategies of anticancer drug delivery systems (DDSs) rely on the surface functionalization of nanocarriers with specific ligands, which trigger the internalization in cancer cells via ...receptor-mediated endocytosis. The endocytosis implies the entrapment of DDSs in acidic vesicles (endosomes and lysosomes) and their eventual ejection by exocytosis. This process, intrinsic to eukaryotic cells, is one of the main drawbacks of DDSs because it reduces the drug bioavailability in the intracellular environment. The escape of DDSs from the acidic vesicles is, therefore, crucial to enhance the therapeutic performance at low drug dose. To this end, we developed a multifunctionalized DDS that combines high specificity towards cancer cells with endosomal escape capabilities. Doxorubicin-loaded mesoporous silica nanoparticles were functionalized with polyethylenimine, a polymer commonly used to induce endosomal rupture, and hyaluronic acid, which binds to CD44 receptors, overexpressed in cancer cells. We show irrefutable proof that the developed DDS can escape the endosomal pathway upon polymeric functionalization. Interestingly, the combination of the two polymers resulted in higher endosomal escape efficiency than the polyethylenimine coating alone. Hyaluronic acid additionally provides the system with cancer targeting capability and enzymatically controlled drug release. Thanks to this multifunctionality, the engineered DDS had cytotoxicity comparable to the pure drug whilst displaying high specificity towards cancer cells. The polymeric engineering here developed enhances the performance of DDS at low drug dose, holding great potential for anticancer therapeutic applications.
The capability of montmorillonite as a matrix (MONT) to improve the photostability of photolabile drugs has been recently reported. Herein promethazine (PRO), which was chosen as a model drug because ...of its photodegradation mechanism, was intercalated into this inorganic matrix, and the effects on drug photoprotection were evaluated as well. The hybrid material (MONT-PRO) was successfully prepared with high drug loading and then was characterized by X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), and FTIR spectroscopy. The spectrophotometric measurements as a function of light exposure time showed that PRO intercalation into montmorillonite markedly improved the drug photostability because a 5-fold-slower degradation rate was determined compared to that measured for PRO in homogeneous solutions; nanosecond transient absorption measurements highlighted that the interaction with the inorganic matrix made negligible the photoionization process of the drug, and its efficiency in producing singlet oxygen was strongly reduced. The MONT-PRO intercalation compound could be easily formulated in gel or ointment media without losing its photostability.
The modification of amyloid fibrils cytotoxicity through exogenous nanomaterials is crucial to understand the processes controlling the role of protein aggregation in the related diseases. The ...influence of nanoparticles on amyloid stability yields great interest due to the small size and high surface area-to-volume ratio of nanoparticles. Various physico-chemical parameters play a role in the interaction of proteins and nanoparticles in solution, thus influencing the disaggregation of preformed fibrils. We have examined the influence of two kinds of metallic nanoparticles on lysozyme amyloid fibrils using a multi-technique approach and focalized their impact on cytotoxicity on human neuroblastoma cells (SH-SY5Y). In particular, fluorescence, infrared and circular dichroism spectroscopies, optical and atomic force microscopy experiments have been carried out; the results are analyzed to rationalize the effects of these complexes on neural cell viability. It is remarkable, that the fibrils in the presence of AuNPs, unlike fibrils alone or with AgNPs, do not generate a significant cytotoxic effect even at high concentration and an amyloid degradation effect is visible.
In this work a novel strategy is introduced to achieve thermally switchable emission from photon upconversion (UC) systems based on organic dyes. When these molecules were dissolved at low ...concentrations in phase-change media, a reversible, sharp, and nearly complete interconversion from blue upconverted emission to red luminescence was observed around the solid-to-liquid transition of the system. This result was rationalized in terms of dye aggregation, which selectively occurs in the solid state and dramatically enhances the inter-chromophoric energy transfer processes leading to UC. Notably, this behavior is extendable to different media and dyes, which allows an easy tuning of the switching temperature and emission colors. In addition, with proper selection of the phase-change medium, our strategy permits facile preparation of solid molecular materials showing photon UC at room temperature and even at sub-micromolar dye concentrations.
The exciton dynamics in semiconductor nanocrystals can be strongly affected by coupling the nanocrystals to organic ligands. A deeper understanding of the interactions in semiconductor–organic hybrid ...systems is important for the design of functional devices. In the present work, the interactions between CdS quantum dots and bithiophene molecules have been investigated. In particular, the photophysical behavior of CdS nanocrystals has been investigated in n-heptane in the presence of increasing bithiophene concentration by use of steady-state and time-resolved measurements. Bithiophene is a well-known electron donor (or hole acceptor), and it has a good affinity with CdS surface for the presence of sulfur atoms. The nanocrystal luminescence was efficiently quenched upon addition of increasing concentration of the thiophene derivative, and modifications in the emission decay profiles of CdS were observed; the analysis of luminescence data suggests that quenching is mainly due to static interaction able to modify the dynamics of the exciton states of the hybrid nanomaterials. The transient absorption measurements enable to detect the bithiophene radical cation upon CdS excitation, thus revealing the occurrence of an efficient hole transfer process from the nanocrystals to the organic ligand, for which a quantum efficiency of 36% has been measured. The dependence of transient signal on bithiophene concentration and the formation of tetrathiophene intermediates indicate that CdS exciton states are able to photosensitize the polymerization of bithiophene after the hole transfer processes. The data indicate that in the investigated system the decay of charged species is not determined by back-reactions.
Oleogels containing silica-silver-based nanomaterials were prepared to be used as potential antimicrobial treatment for preventing and curing skin infections. Fumed silica was used as a bifunctional ...excipient able to offer support to silver-based nanoparticle growth and act as a gelling agent for oleogel formulation. First, silica-silver composites were prepared following a sustainable method by contact of fumed silica and silver nitrate in the presence of ethanol and successive UV irradiation. The composites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), ATR FT-IR spectroscopy and UV-Vis spectrophotometry. The presence of 8-20 nm spherical nanoparticles, in addition to the silica aggregates and AgNO
crystals, was detected. The composites showed good antimicrobial activity against the Gram-negative
and the Gram-positive bacteria
and
. Thus, they were formulated in an oleogel, obtained using fumed silica as a gelling agent. For comparison, oleogels containing AgNO
were prepared according to two different formulative techniques. The silica-silver-based oleogels showed good antimicrobial activity and did not show cytotoxic effects for fibroblasts and keratinocytes.
Silver nanoparticles are usually prepared by the reduction of silver cations through chemical and non-sustainable procedures that involve the use of reducing chemical agents. Therefore, many efforts ...have been made in the search for sustainable alternative methods. Among them, an ultrasound-assisted procedure could be a suitable and sustainable method to afford well-dispersed and nanometric silver particles. This paper describes a sustainable, ultrasound-assisted method using citrate as a reducing agent to prepare silver@hydroxyapatite functionalized calcium carbonate composites. For comparison, an ultrasound-assisted reduction was performed in the presence of NaBH4. The composites obtained in the presence of these two different reducing agents were compared in terms of nanoparticle nature, antimicrobial activity, and cytotoxic activity. The nanoparticle nature was investigated by several techniques, including X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, UV–Vis spectroscopic measurements, and X-ray photoemission spectroscopy. Nanoparticles with a predominance of Ag or Ag3PO4 were obtained according to the type of reducing agent used. All composites were tested for antimicrobial and antibiofilm activities against Gram-positive and Gram-negative (Staphylococcus aureus and Pseudomonas aeruginosa, respectively) bacteria and for cytotoxicity towards human skin keratinocytes and human fibroblasts. The nature of the nanoparticles, Ag or Ag3PO4, and their predominance seemed to affect the in vitro silver release and the antimicrobial and antibiofilm activities. The composites obtained by the citrate-assisted reduction gave rise to the best results.
A solid-state Ultraviolet-photoreduction process of silver cations to produce Ag
nanostructures on a mesoporous silica is presented as an innovative method for the preparation of efficient ...environmental anti-fouling agents. Mesoporous silica powder, contacted with AgNO
, is irradiated at 366 nm, where silica surface defects absorb. The detailed characterization of the materials enables us to document the silica assisted photo-reduction. The appearance of a Visible (Vis) band centered at 470 nm in the extinction spectra, due to the surface plasmon resonance of Ag
nanostructures, and the morphology changes observed in transmission electron microscopy (TEM) images, associated with the increase of Ag/O ratio in energy dispersive X-ray (EDX) analysis, indicate the photo-induced formation of Ag
. The data demonstrate that the photo-induced reduction of silver cation occurs in the solid state and takes place through the activation of silica defects. The activation of the materials after UV-processing is then tested, evaluating their antimicrobial activity using an environmental filamentous fungus,
. The treatment doubled inhibitory capacity in terms of minimal inhibitory concentration (MIC) and biofilm growth. The antimicrobial properties of silver-silica nanocomposites are investigated when dispersed in a commercial sealant; the nanocomposites show excellent dispersion in the silicon and improve its anti-fouling capacity.
Chitosan films containing mesoporous SBA-15 supported silver nanoparticles (AgNPs) were prepared to be applied as a potential wound dressing material. First SBA-15-silver nanoparticle (SBA-15-Ag) ...composite materials were prepared by a controlled annealing process without the use of organic solvents and reagents. The SBA-15-AgNPs were characterized in detail by X-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy which evidenced the presence of uniformly distributed silver nanostructures inside the silicate pores. UV-vis spectra of the sample showed a band at 430 nm characteristic of the surface plasmon resonance of silver nanoparticles with a diameter below 10 nm and X-ray photoemission spectra confirmed the formation of metal-nanoparticles on the silicate template. Then SBA-15-Ag was used to prepare chitosan films which were characterized in detail. In particular, they showed good hydration properties, water vapor transmission rate and mechanical properties. After hydration films exhibited good antimicrobial activity against both Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus epidermidis and S. aureus) bacteria.
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