Alginate microparticles containing silver@hydroxyapatite functionalized calcium carbonate composites.

This paper focuses on the preparation and characterization of antibacterial alginate microparticles containing silver@hydroxyapatite functionalized calcium carbonate composites for tissue engineering. Microparticles were prepared by cross-linking a silver@composite sodium alginate dispersion with CaCl2. This method showed a very good silver efficiency loading and the presence of silver chloride nanoparticles was detected. Silver free microparticles, containing hydroxyapatite functionalized calcium carbonates and neat alginate microparticles were prepared as well. All microparticles were characterized for water absorption and for in vitro bioactivity by immersion in simulated body fluid (SBF). Finally, antimicrobial and antibiofilm activities as well as cytotoxicity were evaluated. Microparticles containing silver@composites exhibited good antimicrobial and antibiofilm activities against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Candida albicans, but exerted a certain cytotoxicity against the tested cell models (fibroblasts and osteoblasts). Microparticles containing hydroxyapatite functionalized calcium carbonates were found to be always less cytotoxic, also in comparison to neat alginate microparticles, proving that the presence of the inorganic matrices exerts a protective effect on microparticle cytotoxicity.

Alginate Microbeads Containing Halloysite and Layered Double Hydroxide as Efficient Carriers of Natural Antimicrobials.

The present paper describes the preparation and characterization of novel microbeads from alginate filled with nanoclay such as halloysite nanotubes (HNTs). HNTs were used as support for the growth of layered double hydroxide (LDH) crystals producing a flower-like structure (HNT@LDH). Such nanofiller was loaded with grapefruit seed oil (GO), an active compound with antimicrobial activity, up to 50% wt. For comparison, the beads were also loaded with HNT and LDH separately, and filled with the same amount of GO. The characterization of the filler was performed using XRD and ATR spectroscopy. The beads were analyzed through XRD, TGA, ATR and SEM. The functional properties of the beads, as nanocarriers of the active compound, were investigated using UV-vis spectroscopy. The release kinetics were recorded and modelled as a function of the structural characteristics of the nanofiller.

Ag/Ag3PO4 Nanoparticle-Decorated Hydroxyapatite Functionalized Calcium Carbonate: Ultrasound-Assisted Sustainable Synthesis, Characterization, and Antimicrobial Activity.

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.

Immobilization of Alendronate on Zirconium Phosphate Nanoplatelets.

Different amounts of sodium-alendronate (ALN) were loaded into layered zirconium phosphates of alpha and gamma type (αZP and γZP) by means of topotactic exchange reactions of phosphate with ALN. In order to extend the exchange process to the less accessible interlayer regions, ALN solutions were contacted with colloidal dispersions of the layered solids previously exfoliated in single sheets by means of intercalation reaction of propylamine (for αZP) or acetone (for γZP). The ALN loading degree was determined by liquid P-nuclear magnetic resonance (NMR) and inductively coupled plasma (ICP), and it was reported as ALN/Zr molar ratios (Rs). The maximum R obtained for γZP was 0.34, while αZP was able to load a higher amount of ALN, reaching Rs equal to 1. The synthesized compounds were characterized by X-ray powder diffractometry, scanning electron microscopy (SEM), solid-state NMR, and infrared spectroscopy. The way the grafted organo-phosphonate groups were bonded to the layers of the host structure was suggested. The effect of ZP derivatives was assessed on cell proliferation, and the results showed that after 7 days of incubation, none of the samples showed a decrease in cell proliferation.

Mixed Zirconium Phosphate Bis-Phosphonomethyl Glycine from Nanocrystalline α-Zirconium Phosphate: A Tailored Suite for Gold Nanoparticles.

A novel synthetic approach was investigated for the preparation of nanoplatelets of mixed zirconium phosphate bis-phosphonomethyl glycine, ZPGly, by the reaction of a gel of nanocrystalline α-type zirconium phosphate with N,N-bis-phosphonomethyl glycine, H3Gly. The syntheses were carried out in the absence of hydrofluoric acid by changing both the reagent relative amounts and temperature. An H3Gly/Zr molar ratio >2 did not significantly improve the degree of crystallinity of the materials, while an increase of temperature from 80 °C to 120 °C improved the crystallinity; the best result was obtained with H3Gly/Zr molar ratio = 2 and with a temperature reaction of 120 °C. The sample consisted of nanoplatelets with the size in the range 20-40 nm, and it was successfully exfoliated by treatment with a solution of methylamine. By treatment of the ZPGly colloidal dispersions with HAuCl4, a color change from white to red-violet was observed, indicating the formation of gold nanoparticles. The size and morphology of the gold particles were affected by the degree of crystallinity and, in turn, by the composition of the ZPGly support. As a matter of fact, large micrometric Au particles with a cubo-octahedral morphology were obtained by using the less crystalline ZPGly_R2-80 sample, while interconnected Au particles, with a size of about 16 nm, were obtained by using ZPGly_R2-120. The samples exhibited an absorption maximum in the visible region due to the surface plasmon resonance of gold nanoparticles.

Antimicrobial Oleogel Containing Sustainably Prepared Silver-Based Nanomaterials for Topical Application.

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 AgNO3 crystals, was detected. The composites showed good antimicrobial activity against the Gram-negative Pseudomonas aeruginosa and the Gram-positive bacteria Staphylococcus aureus and Staphylococcus epidermidis. Thus, they were formulated in an oleogel, obtained using fumed silica as a gelling agent. For comparison, oleogels containing AgNO3 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.

MgAl and ZnAl-Hydrotalcites as Materials for Cosmetic and Pharmaceutical Formulations: Study of Their Cytotoxicity on Different Cell Lines.

The knowledge about the effect of hydrotalcites (HTlcs), largely used in pharmaceutics, on non-malignant cell lines is limited. The effect of MgAl-HTlc-and ZnAl-HTlc- (NO3−/Cl−/CO32−) on the cell viability of HaCat, fibroblasts and HepG2 was studied by MTT assay. Cells were incubated either with HTlc suspensions in the culture media and with the supernatant obtained from the suspension being centrifuged. MgAl-HTlcs suspensions resulted in being cytotoxic. As SEM and TEM analyses showed the presence of sub-micrometric particles in all the MgAl-HTlc examined, it could be hypothesized that this fraction can be internalized into cells reducing the viability. MgAl-HTlc-NO3 is the most cytotoxic probably due to the additional effect of NO3− anions. ZnAl-HTlcs are cytotoxic, especially for HaCat and HepG2 cells (viability <60% at all the concentrations assayed). The effect is attributable both to the sub-micrometric fraction (identified by TEM) and to the high Zn2+ levels found in the culture medium by ICP-OES analysis, suggesting that ZnAl-HTlcs are less stable than MgAl-HTlc in the used media. The obtained results suggest that it is very important to perform ad hoc studies in order to evaluate HTlc safety before to be introduced in a formulation.

Overcoming Antibiotic Resistance: Playing the 'Silver Nanobullet' Card.

Enhancing the antibacterial activity of old antibiotics by a multitarget approach, such as combining antibiotics with metal nanoparticles, is a valuable strategy to overcome antibacterial resistance. In this work, the synergistic antimicrobial effect of silver nanoparticles and antibiotics, immobilized on a solid support, was investigated. Nanometric layered double hydroxides (LDH) based on Zn(II) and Al(III) were prepared by the double microemulsion technique. The dual function of LDH as an anionic exchanger and support for metal nanoparticles was exploited to immobilize both silver and antibiotics. Cefazolin (CFZ), a ß-lactam, and nalidixic acid (NAL), a quinolone, were selected and intercalated into LDH obtaining ZnAl-CFZ and ZnAl-NAL samples. These samples were used for the growth of silver nanoparticles with dimension ranging from 2.5 to 8 nm. Silver and antibiotics release profiles, from LDH loaded with antibiotics and Ag/antibiotics, were evaluated in two different media: water and phosphate buffer. Interestingly, the release profiles are affected by both the acceptor media and the presence of silver. The synergistic antibacterial activity of LDH containing both silver and antibiotics were investigated on gram-positives (Staphylococcus aureus and Streptococcus pneumoniae) and gram-negatives (Pseudomonas aeruginosa) and compared with the plain antimicrobials and LDH containing only antibiotics or silver.

Synthesis, Crystal Structure, and Antibacterial Properties of Silver-Functionalized Low-Dimensional Layered Zirconium Phosphonates.

New insoluble layered zirconium phosphate carboxyaminophosphonates (ZPs), with the general formula Zr2(PO4)H5[(O3PCH2)2N(CH2)nCOO]2·mH2O (n = 3, 4, and 5), have been prepared and characterized. The crystal structure for n = 3 and 4 samples was determined ab initio from X-ray powder diffraction data. The structure for n = 3 was monoclinic in space group C2/c with the following unit cell parameters: a = 34.346(1) Å, b = 8.4930(2) Å, c = 9.0401(2) Å, and ß = 97.15(1)°. The structure for n = 4 was triclinic in space group P1̅ with the following unit cell parameters: a = 17.9803(9) Å, b = 8.6066(4) Å, c = 9.0478(3) Å, α = 90.466(3)°, ß = 94.910(4)°, and γ = 99.552(4)°. The two structures had the same connectivity as Zr phosphate glycine diphosphonate (n = 1), as previously reported. By intercalation of short amines, these layered compounds were exfoliated in single lamella or packets of a few lamellae, which formed colloidal dispersions in water. After a thorough characterization, the dispersed lamellae were functionalized with Ag nanoparticles, which were grown in situ on the surface of exfoliated lamellae. Finally, their antimicrobial activity was tested on several Gram-positive and Gram-negative bacteria. All of these systems were found to be active against the four pathogens most frequently isolated from orthopedic prosthetic infections and often causative of nosocomial infections. Interestingly, they were found to express powerful inhibitory activity even against bacterial strains exhibiting a relevant profile of antibiotic resistance such as Staphylococcus aureus ATCC 700699.

Hydroxyapatite Functionalized Calcium Carbonate Composites with Ag Nanoparticles: An Integrated Characterization Study.

In the present work, composite materials very promising for biomedical and pharma-ceutical applications were investigated. They are composed of silver nanoparticles (Ag NPs) in a matrix constituted of calcium carbonate functionalized with hydroxyapatite (HA-FCC). The composites were obtained by different synthesis methods, starting from a mixture of the silver acetate with HA-FCC (using adsorption or mixing in wet conditions methods) and then treating them by exposure to visible light or calcination to promote the silver reduction; a synthetic procedure based on ultrasound-assisted reduction with NaBH4 or citrate was also carried out. The characterization by X-ray photoelectron spectroscopy and reflected electron energy loss spectroscopy analysis also involved the reference sample of HA-FCC matrix. Then the morphology of the Ag NPs and the crystalline structure of HA-FCC were studied by transmission electron microscopy and X-ray diffraction, respectively. To assess the effectiveness of the different methods on silver reduction, the Auger parameters α' were calculated and compared. The use of this methodology based on the Auger parameter is neither trivial nor ordinary. We demonstrate its validity since the different values of this parameter allow to identify the oxidation state of silver and consequently to evaluate the formation yield of metallic Ag NPs in the HA-FCC matrix and the effectiveness of the different reduction methods used.

Solid State Photoreduction of Silver on Mesoporous Silica to Enhance Antifungal Activity.

A solid-state Ultraviolet-photoreduction process of silver cations to produce Ag0 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 AgNO3, 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 Ag0 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 Ag0. 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, Aspergillus niger. 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.

Bioinspired Reactive Interfaces Based on Layered Double Hydroxides-Zn Rich Hydroxyapatite with Antibacterial Activity.

This work is focused on the preparation and multi-technique characterization of potentially biocompatible reactive interfaces obtained by combining layered double hydroxides (LDHs) and hydroxyapatite (HA). Antimicrobial and osteoinductive metallic ions as Zn2+ and Ga3+ were chosen as intralayer constituents of LDH to obtain ZnAl and ZnAlGa systems. These LDHs, exchanged with dihydrogenphosphate anions, promoted the precipitation of HA on the LDH surface yielding HA@LDH composites. X-ray diffraction quantitative analysis, through the Rietveld refinement method, coupled with elemental analysis and micro-Raman spectroscopy showed the formation of a mixed Ca-Zn HA phase. Scanning electron microscopy revealed that HA, in the presence of LDH, grew preferentially along its a-axis, thus crystallizing mainly in the form of flake crystals. LDH and HA@LDH composites showed antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa at not cytotoxic concentrations for human osteoblasts (hFob 1.19), especially when Ga cations were present in the LDH structure. The effect of the presence of HA in the composites on the bone-bonding ability and on human osteoblast proliferation was also investigated. The HA seemed to reduce the toxicity of the LDH toward human osteoblast while did not affect the bone-bonding ability. This multidisciplinary study provides the bio-chemical, structural characterization of new LDH and HA@LDH composites, evaluating also their bioactivity to be potentially applicable to titanium-based prostheses.

Biofunctionalization of Poly(lactide-co-glycolic acid) Using Potent NorA Efflux Pump Inhibitors Immobilized on Nanometric Alpha-Zirconium Phosphate to Reduce Biofilm Formation.

Polymeric composites, where bioactive species are immobilized on inorganic nanostructured matrix, have received considerable attention as surfaces able to reduce bacterial adherence, colonization, and biofilm formation in implanted medical devices. In this work, potent in-house S. aureus NorA efflux pump inhibitors (EPIs), belonging to the 2-phenylquinoline class, were immobilized on nanometric alpha-zirconium phosphate (ZrP) taking into advantage of acid-base or intercalation reactions. The ZrP/EPI were used as filler of poly(lactide-co-glycolic acid) (PLGA) to obtain film composites with a homogeneous distribution of the ZrP/EPI fillers. As reference, PLGA films loaded with ZrP intercalated with thioridazine (TZ), that is recognized as both a NorA and biofilm inhibitor, and with the antibiotic ciprofloxacin (CPX) were prepared. Composite films were characterized by X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The ability of the composite films, containing ZrP/EPI, to inhibit biofilm formation was tested on Staphylococcus aureus ATCC 29213 and Staphylococcus epidermidis ATCC 12228, and it was compared with that of the composite loaded with ZrP/TZ. Finally, the antibacterial activity of CPX intercalated in ZrP was evaluated when used in combination with ZrP/EPI in the PLGA films.

Effects of Titanium Dioxide Nanoparticles on Porcine Prepubertal Sertoli Cells: An "In Vitro" Study.

The increasing use of nanomaterials in a variety of industrial, commercial, medical products, and their environmental spreading has raised concerns regarding their potential toxicity on human health. Titanium dioxide nanoparticles (TiO2 NPs) represent one of the most commonly used nanoparticles. Emerging evidence suggested that exposure to TiO2 NPs induced reproductive toxicity in male animals. In this in vitro study, porcine prepubertal Sertoli cells (SCs) have undergone acute (24 h) and chronic (from 1 up to 3 weeks) exposures at both subtoxic (5 µg/ml) and toxic (100 µg/ml) doses of TiO2 NPs. After performing synthesis and characterization of nanoparticles, we focused on SCs morphological/ultrastructural analysis, apoptosis, and functionality (AMH, inhibin B), ROS production and oxidative DNA damage, gene expression of antioxidant enzymes, proinflammatory/immunomodulatory cytokines, and MAPK kinase signaling pathway. We found that 5 µg/ml TiO2 NPs did not induce substantial morphological changes overtime, but ultrastructural alterations appeared at the third week. Conversely, SCs exposed to 100 µg/ml TiO2 NPs throughout the whole experiment showed morphological and ultrastructural modifications. TiO2 NPs exposure, at each concentration, induced the activation of caspase-3 at the first and second week. AMH and inhibin B gene expression significantly decreased up to the third week at both concentrations of nanoparticles. The toxic dose of TiO2 NPs induced a marked increase of intracellular ROS and DNA damage at all exposure times. At both concentrations, the increased gene expression of antioxidant enzymes such as SOD and HO-1 was observed whereas, at the toxic dose, a clear proinflammatory stress was evaluated along with the steady increase in the gene expression of IL-1α and IL-6. At both concentrations, an increased phosphorylation ratio of p-ERK1/2 was observed up to the second week followed by the increased phosphorylation ratio of p-NF-kB in the chronic exposure. Although in vitro, this pilot study highlights the adverse effects even of subtoxic dose of TiO2 NPs on porcine prepubertal SCs functionality and viability and, more importantly, set the basis for further in vivo studies, especially in chronic exposure at subtoxic dose of TiO2 NPs, a condition closer to the human exposure to this nanoagent.

Layered double hydroxides are still out in the bloom: Syntheses, applications and advantages of three-dimensional flower-like structures.

Layered double hydroxides (LDHs) have received great attention for years in numerous fields. Controlled and flexible layer composition, as well as the vast assortment of possible anionic guests, and easy adaptability for multipurpose applications, have been some of the many reasons behind their extraordinary success. However, versatility does not only involve the composition or the dimensions of the crystals but also their morphology. Aside from conventional hexagonal, flat structures, three-dimensional assemblies have been reported with architectures closely resembling those of flowers. The possibility of interconnecting the LDH nanosheets in rosette-like geometries has arisen the interest in finding new ways to control, modulate, and guide the particle growth obtaining hierarchical structures to be adapted to specific targets. This review is focused on describing the different strategies implemented to build flower-like assemblies, and on investigating their applications, looking for specific advantages of the use of a three-dimensional architecture over a bi-dimensional one.

Iridium-Doped Nanosized Zn-Al Layered Double Hydroxides as Efficient Water Oxidation Catalysts.

Layered double hydroxides (LDHs) are an ideal platform to host catalytic metal centers for water oxidation (WO) owing to the high accessibility of water to the interlayer region, which makes all centers potentially reachable and activated. Herein, we report the syntheses of three iridium-doped zinc-aluminum LDHs (Ir-LDHs) nanomaterials (1-3, with about 80 nm of planar size and a thickness of 8 nm as derived by field emission scanning electron microscopy and powder X-ray diffraction studies, respectively), carried out in the confined aqueous environment of reverse micelles, through a very simple and versatile procedure. These materials exhibit excellent catalytic performances in WO driven by NaIO4 at neutral pH and 25 °C, with an iridium content as low as 0.5 mol % (∼0.8 wt %), leading to quantitative oxygen yields (based on utilized NaIO4, turnover number up to ∼10,000). Nanomaterials 1-3 display the highest ever reported turnover frequency values (up to 402 min-1) for any heterogeneous and heterogenized catalyst, comparable only to those of the most efficient molecular iridium catalysts, tested under similar reaction conditions. The boost in activity can be traced to the increased surface area and pore volume (>5 times and 1 order of magnitude, respectively, higher than those of micrometric materials of size 0.3-1 µm) estimated for the nanosized particles, which guarantee higher noble metal accessibility. X-ray absorption spectroscopy (XAS) studies suggest that 1-3 nanomaterials, as-prepared and after catalysis, contain a mixture of isolated, single octahedral Ir(III) sites, with no evidence of Ir-Ir scattering from second-nearest neighbors, excluding the presence of IrO2 nanoparticles. The combination of the results obtained from XAS, elemental analysis, and ionic chromatography strongly suggests that iridium is embedded in the brucite-like structure of LDHs, having four hydroxyls and two chlorides as first neighbors. These results demonstrate that nanometric LDHs can be successfully exploited to engineer efficient WOCs, minimizing the amount of iridium used, consistent with the principle of the noble-metal atom economy.

Antibacterial Properties of a Novel Zirconium Phosphate-Glycinediphosphonate Loaded with Either Zinc or Silver.

A novel compound consisting of a zirconium phosphate-glycinediphosphonate (ZPGly) has recently been introduced. This 2D-structured material forming nanosheets was exfoliated under appropriate conditions, producing colloidal aqueous dispersions (ZPGly-e) which were then loaded with zinc (Zn/ZPGly) or silver ions. Silver ions were subsequently reduced to produce metallic silver nanoparticles on exfoliated ZPGly nanosheets (Ag@ZPGly). In the search for new anti-infective materials, the present study investigated the properties of colloidal dispersions of ZPGly-e, Zn/ZPGly, and Ag@ZPGly. Ag@ZPGly was found to be a bactericidal material and was assayed to define its minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) on the five most prevalent pathogens of orthopaedic implant infections, namely: Staphylococcus aureus ATCC25923, Staphylococcus epidermidis RP62A, Enterococcus faecalis ATCC29212, Escherichia coli ATCC51739, and Pseudomonas aeruginosa ATCC27853. MIC and MBC were in the range of 125-250 µg/mL and 125-1000 µg/mL, respectively, with E. coli being the most sensitive species. Even colloidal suspensions of exfoliated ZPGly nanosheets and Zn/ZPGly exhibited some intrinsic antibacterial properties, but only at greater concentrations. Unexpectedly, Zn/ZPGly was less active than ZPGly-e.

Zirconium Carboxyaminophosphonate Nanosheets as Support for Ag Nanoparticles.

A layered insoluble inorganic-organic solid, namely zirconium phosphate glycine-N,N-bismethylphosphonate, was used to prepare dispersions of nanosheets to support active metals such as metallic silver nanoparticles and zinc ions. Zr phosphate-phosphonate microcrystals were first exfoliated with methylamine to produce a stable colloidal dispersion and then the methylamine was removed by treatment with hydrochloric acid. The obtained colloidal dispersion of Zr phosphate-phosphonate nanosheets was used to immobilize silver or zinc cations, via ion exchange, with the acidic protons of the sheets. The layered matrix showed a great affinity for the metal cations up taking all the added cations. The treatment of the dispersions containing silver ions with ethanol yielded metal silver nanoparticles grafted on the surface of the layered host. The samples were characterized by X-ray powder diffraction, elemental analysis transmission electron microscopy, and selected samples were submitted to antimicrobial tests. The nanocomposites based on Ag nanoparticles showed good bactericidal properties against the bacterial reference strain Staphylococcus epidermidis (S. epidermidis).

Polydopamine Nanoparticle-Coated Polysulfone Porous Granules as Adsorbents for Water Remediation.

Water purification technologies possibly based on eco-sustainable, low cost, and multifunctional materials are being intensively pursued to resolve the current water scarcity and pollution. In this scenario, polysulfone hollow porous granules (PS-HPGs) prepared from scraps of the industrial production of polysulfone hollow fiber membranes were recently introduced as adsorbents and filtration materials for water and air treatment. Here, we report the functionalization of PS-HPGs with polydopamine (PD) nanoparticles for the preparation of a new versatile and efficient adsorbent material, namely, PSPD-HPGs. The in situ growth of PD under mild alkaline oxidative polymerization allowed us to stably graft PD on polysulfone granules. Enhanced removal efficiency of ofloxacin, an antibiotic drug, with an improvement up to 70% with respect to the pristine PS-HPGs, and removal of Zn(II) and Ni(II) were also observed after PD modification. Remarkably, removal of Cu(II) ions with an efficiency up to 80% was observed for PSPD-HPGs, whereas no adsorption was found for the PD-free precursor. Collectively, these data show that modification with a biocompatible polymer such as PD provides a simple and valuable tool to enlarge the field of application of polysulfone hollow granules for water remediation from both organic and metal cation contaminants.

Nano-hybrid electrospun non-woven mats made of wool keratin and hydrotalcites as potential bio-active wound dressings.

In this work, nano-hybrid electrospun non-woven mats made of wool keratin combined with diclofenac loaded hydrotalcites (HTD) were prepared and characterized as potential drug delivery systems and scaffolds for fibroblast cell growth. Nano-hybrid electrospun non-woven mats showed a good adaptability to wet skin, effortlessly conforming to the three-dimensional topography of the tissue. Nanosized HTD exercised an overall reinforcing action on the electrospun non-woven mats since the nanohybrid samples displayed a reduced swelling ratio and a slower degradation profile compared to keratin-based nanofiber non-woven mats containing free diclofenac, without negative effects on drug release. The cell viability test indicated a decreased toxicity of the drug when loaded into nanofibers and confirmed the biocompatibility of keratin/HTD electrospun non-woven mats; moreover, a controlled diclofenac release within the first 24 hours does not compromise the fibroblast cell growth in a significant manner.