The Role of the pH in the Impregnation of Spherical Mesoporous Silica Particles with L-Arginine Aqueous Solutions.

In the context of the development of carriers for amino acids delivery, Spherical Mesoporous Silica Particles (SMSP), characterized by particles size ranging from 0.15 µm to 0.80 µm and average pore diameter of 2.4 nm, were synthesised and loaded with L-arginine (ARG), a basic amino acid involved in several physiological processes. The loading was performed using water as a solvent through the wet impregnation method (with a final arginine content of 9.1% w/w). The material was characterized before and after impregnation by means of X-Ray Diffraction (XRD), nitrogen sorption analysis, Field Emission Scanning Electron Microscopy (FESEM) and Fourier Transform Infrared (FT-IR) spectroscopy. SMSP are shown to suffer degradation upon impregnation, which dramatically affects their porosity. To elucidate the role of the pH of the ARG impregnating solution (originally set at pH ≈ 11) on SMSP degradation, the loading was performed under different pH conditions (5 and 9) keeping constant the ARG concentration. The impregnation performed with acidic solution did not modify the carrier. All samples displayed ARG in amorphous form: zwitterionic species were present in SMSP impregnated at basic pH whereas positive protonated species in that impregnated at acidic pH.

Whey Proteins-Zinc Oxide Bionanocomposite as Antibacterial Films.

The use of toxic crosslinking agents and reagents in the fabrication of hydrogels is a frequent issue which is particularly concerning for biomedical or food packaging applications. In this study, novel antibacterial bionanocomposite films were obtained through a simple solvent casting technique without using any crosslinking substance. Films were made from a flexible and transparent whey protein matrix containing zinc oxide nanoparticles synthesised via a wet chemical precipitation route. The physicochemical and functional properties of the ZnO nanoparticles and of the composite films were characterised, and their antibacterial activity was tested against S. epidermidis and E. coli. The synthesised ZnO nanoparticles had an average size of about 30 nm and a specific surface area of 49.5 m2/g. The swelling ratio of the bionanocomposite films increased at basic pH, which is an appealing feature in relation to the absorption of chronic wound exudate. A n-ZnO concentration-dependent antibacterial effect was observed for composite films. In particular, marked antibacterial activity was observed against S. epidermidis. Overall, these findings suggest that this novel material can be a promising and sustainable alternative in the design of advanced solutions for wound dressing or food packaging.

Valorization of Byproducts of Hemp Multipurpose Crop: Short Non-Aligned Bast Fibers as a Source of Nanocellulose.

Nanocellulose was extracted from short bast fibers, from hemp (Cannabis sativa L.) plants harvested at seed maturity, non-retted, and mechanically decorticated in a defibering apparatus, giving non-aligned fibers. A chemical pretreatment with NaOH and HCl allowed the removal of most of the non-cellulosic components of the fibers. No bleaching was performed. The chemically pretreated fibers were then refined in a beater and treated with a cellulase enzyme, followed by mechanical defibrillation in an ultrafine friction grinder. The fibers were characterized by microscopy, infrared spectroscopy, thermogravimetric analysis and X-ray diffraction after each step of the process to understand the evolution of their morphology and composition. The obtained nanocellulose suspension was composed of short nanofibrils with widths of 5-12 nm, stacks of nanofibrils with widths of 20-200 nm, and some larger fibers. The crystallinity index was found to increase from 74% for the raw fibers to 80% for the nanocellulose. The nanocellulose retained a yellowish color, indicating the presence of some residual lignin. The properties of the nanopaper prepared with the hemp nanocellulose were similar to those of nanopapers prepared with wood pulp-derived rod-like nanofibrils.

Amino groups modified SBA-15 for dispersive-solid phase extraction in the analysis of micropollutants by QuEchERS approach.

In the analysis of contaminants in food products, sample preparation is performed by proper adsorbents, whose choice is crucial to eliminate matrix interference. In this work we modified SBA-15 adsorbents by functionalization with (3-aminopropyl)-triethoxysilane (SBA-15-APTES) and N-[3-(trimethoxysilyl)propyl]aniline (SBA-15-AN) aiming to use them for the first time in the clean-up step of a QuEChERS (quick, easy, cheap, effective, rugged and safe) extraction of micropollutants from strawberry, a sugar rich fruit. After physico-chemical characterization by nitrogen adsorption, infrared spectroscopy and thermogravimetric analysis, the adsorption capabilities of SBA-15 sorbents and possible interaction mechanisms were studied at different pH (2.1-8.5) for glucose, sucrose and fructose at concentrations characteristic of those found in strawberries. The performance of the two SBA-15 sorbents was compared with that of commercial PSA (primary secondary amine), usually proposed in QuEChERS protocols. Both SBA-15 materials exhibit up to 30% higher adsorption than PSA, suggesting their possible QuEChERS application. Synthesized SBA-15 adsorbents were hence used as innovative dispersive sorbents in the QuEChERS extractions of 13 PAHs and 14 PCBs from strawberry. For PCBs, SBA-15-AN provides better matrix removal than PSA and comparable extraction recoveries around 90%. For PAHs, the use of SBA-15-AN has the advantage of lower relative standard deviation (7%) than PSA (19%).

Piroxicam Loading onto Mesoporous Silicas by Supercritical CO2 Impregnation.

Piroxicam (PRX) is a commonly prescribed nonsteroidal anti-inflammatory drug. Its efficacy, however, is partially limited by its low water solubility. In recent years, different studies have tackled this problem and have suggested delivering PRX through solid dispersions. All these strategies, however, involve the use of potentially harmful solvents for the loading procedure. Since piroxicam is soluble in supercritical CO2 (scCO2), the present study aims, for the first time, to adsorb PRX onto mesoporous silica using scCO2, which is known to be a safer and greener technique compared to the organic solvent-based ones. For comparison, PRX is also loaded by adsorption from solution and incipient wetness impregnation using ethanol as solvent. Two different commercial mesoporous silicas are used (SBA-15 and Grace Syloid® XDP), which differ in porosity order and surface silanol population. Physico-chemical analyses show that the most promising results are obtained through scCO2, which yields the amorphization of PRX, whereas some crystallization occurs in the case of adsorption from solution and IWI. The highest loading of PRX by scCO2 is obtained in SBA-15 (15 wt.%), where molecule distribution appears homogeneous, with very limited pore blocking.

Bispyrene Functionalization Drives Self-Assembly of Graphite Nanoplates into Highly Efficient Heat Spreader Foils.

Thermally conductive nanopapers fabricated from graphene and related materials are currently showing great potential in thermal management applications. However, thermal contacts between conductive plates represent the bottleneck for thermal conductivity of nanopapers prepared in the absence of a high temperature step for graphitization. In this work, the problem of ineffective thermal contacts is addressed by the use of bifunctional polyaromatic molecules designed to drive self-assembly of graphite nanoplates (GnP) and establish thermal bridges between them. To preserve the high conductivity associated to a defect-free sp2 structure, non-covalent functionalization with bispyrene compounds, synthesized on purpose with variable tethering chain length, was exploited. Pyrene terminal groups granted for a strong π-π interaction with graphene surface, as demonstrated by UV-Vis, fluorescence, and Raman spectroscopies. Bispyrene molecular junctions between GnP were found to control GnP organization and orientation within the nanopaper, delivering significant enhancement in both in-plane and cross-plane thermal diffusivities. Finally, nanopapers were validated as heat spreader devices for electronic components, evidencing comparable or better thermal dissipation performance than conventional Cu foil, while delivering over 90% weight reduction.

Supercritical Solvent Impregnation of Different Drugs in Mesoporous Nanostructured ZnO.

Supercritical solvent impregnation (SSI) is a green unconventional technique for preparing amorphous drug formulations. A mesoporous nanostructured ZnO (mesoNsZnO) carrier with 8-nm pores, spherical-nanoparticle morphology, and an SSA of 75 m2/g has been synthesized and, for the first time, subjected to SSI with poorly water-soluble drugs. Ibuprofen (IBU), clotrimazole (CTZ), and hydrocortisone (HC) were selected as highly, moderately, and poorly CO2-soluble drugs. Powder X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, nitrogen adsorption analysis, and ethanol extraction coupled with ultraviolet spectroscopy were employed to characterize the samples and quantify drug loading. Successful results were obtained with IBU and CTZ while HC loading was negligible, which could be related to different solubilities in CO2, drug size, and polarity. Successful SSI resulted in amorphous multilayer confinement of the drug. The mesoNsZnO-IBU system showed double drug loading than the mesoNsZnO-CTZ one, with a maximum uptake of 0.24 g/g. Variation of contact time during SSI of the mesoNsZnO-IBU system showed that drug loading triplicated between 3 and 8 h with an additional 30% increment between 8 h and 24 h. SSI did not affect the mesoNsZnO structure, and the presence of the adsorbed drug reduced the chemisorption of CO2 on the carrier surface.

Nanostructured ZnO as Multifunctional Carrier for a Green Antibacterial Drug Delivery System-A Feasibility Study.

The physico⁻chemical and biological properties of nanostructured ZnO are combined with the non-toxic and eco-friendly features of the scCO2-mediated drug loading technique to develop a multifunctional antimicrobial drug delivery system for potential applications in wound healing. Two nanostructured ZnO (NsZnO) with different morphologies were prepared through wet organic-solvent-free processes and characterized by means of powder X-ray diffraction, field emission scanning electron microscopy (FESEM), and nitrogen adsorption analysis. The antimicrobial activity of the two samples against different microbial strains was investigated together with the in vitro Zn2+ release. The results indicated that the two ZnO nanostructures exhibited the following activity: S. aureus > C. albicans > K. pneumoniae. A correlation between the antimicrobial activity, the physico⁻chemical properties (specific surface area and crystal size) and the Zn2+ ion release was found. Ibuprofen was, for the first time, loaded on the NsZnO carriers with a supercritical CO2-mediated drug impregnation process and in vitro dissolution studies of the loaded drug were performed. A successful loading up to 14% w/w of ibuprofen in its amorphous form was obtained. A preliminary drug release test showed that up to 68% of the loaded ibuprofen could be delivered to a biological medium, confirming the feasibility of using NsZnO as a multifunctional antimicrobial drug carrier.