Fractionation of Raw and Parboiled Rice Husks with Deep Eutectic Solvents and Characterization of the Extracted Lignins towards a Circular Economy Perspective.

In the present work, rice husks (RHs), which, worldwide, represent one of the most abundant agricultural wastes in terms of their quantity, have been treated and fractionated in order to allow for their complete valorization. RHs coming from the raw and parboiled rice production have been submitted at first to a hydrothermal pretreatment followed by a deep eutectic solvent fractionation, allowing for the separation of the different components by means of an environmentally friendly process. The lignins obtained from raw and parboiled RHs have been thoroughly characterized and showed similar physico-chemical characteristics, indicating that the parboiling process does not introduce obvious lignin alterations. In addition, a preliminary evaluation of the potentiality of such lignin fractions as precursors of cement water reducers has provided encouraging results. A fermentation-based optional preprocess has also been investigated. However, both raw and parboiled RHs demonstrated a poor performance as a microbiological growth substrate, even in submerged fermentation using cellulose-degrading fungi. The described methodology appears to be a promising strategy for the valorization of these important waste biomasses coming from the rice industry towards a circular economy perspective.

A Comparative Study on the Thermodynamics of Halogen Bonding of Group†10 Pincer Fluoride Complexes.

The thermodynamics of halogen bonding of a series of isostructural Group 10 metal pincer fluoride complexes of the type [(3,5-R2 -tBu POCOPtBu )MF] (3,5-R2 -tBu POCOPtBu =κ3 -C6 HR2 -2,6-(OPtBu2 )2 with R=H, tBu, COOMe; M=Ni, Pd, Pt) and iodopentafluorobenzene was investigated. Based on NMR experiments at different temperatures, all complexes 1-tBu (R=tBu, M=Ni), 2-H (R=H, M=Pd), 2-tBu (R=tBu, M=Pd), 2-COOMe (R=COOMe, M=Pd) and 3-tBu (R=tBu, M=Pt) form strong halogen bonds with Pd complexes showing significantly stronger binding to iodopentafluorobenzene. Structural and computational analysis of a model adduct of complex 2-tBu with 1,4-diiodotetrafluorobenzene as well as of structures of iodopentafluorobenzene in toluene solution shows that formation of a type I contact occurs.

On the parallelism between the mechanisms behind chromatography and drug delivery: the role of interactions with a stationary phase.

A huge number of studies and work in the drug delivery literature are focused on understanding and modeling transport phenomena, the pivotal point for a good device design. The rationalization of all phenomena involved is fundamental, but several concerns arise leaving many issues unsolved. In order to change the point of view we decided to focus our attention on the parallelisms between two fields that seem to be very far from each other: chromatography and drug release. Taking advantages of the studies conducted by many researchers using chromatographic columns we decided to explain all the phenomena involved in drug delivery considering sodium ibuprofen (IP) molecules as analytes and hydrogel as a stationary phase. In particular, we considered not only diffusion, but also drug-polymer interactions as adsorption on the stationary phase and drug-drug interactions as aggregation of analytes. The hydrogel investigated is a promising formulation made of agarose and carbomer 974p (AC) loaded with IP, a non-steroidal common anti-inflammatory drug. The self-diffusion coefficient of IP in AC formulations was measured by using an innovative method based on a magic angle spinning NMR spectroscopic technique to produce high resolution (liquid-like) spectra. This method (HR-MAS NMR) is used in combination with pulsed field gradient spin echo (PGSE) liquid-state techniques. The model predictions satisfactorily match with the experimental data obtained in water and the gel environment, indicating that the model presented here, despite its simplicity, is able to describe the key phenomena governing the device behavior and could be used to rationalize the experimental activity.

Dynamics and interactions of ibuprofen in cyclodextrin nanosponges by solid-state NMR spectroscopy.

Two different formulations of cyclodextrin nanosponges (CDNS), obtained by polycondensation of ß-cyclodextrin with ethylenediaminetetraacetic acid dianhydride (EDTAn), were treated with aqueous solutions of ibuprofen sodium salt (IbuNa) affording hydrogels that, after lyophilisation, gave two solid CDNS-drug formulations. 1H fast MAS NMR and 13C CP-MAS NMR spectra showed that IbuNa was converted in situ into its acidic and dimeric form (IbuH) after freeze-drying. 13C CP-MAS NMR spectra also indicated that the structure of the nanosponge did not undergo changes upon drug loading compared to the unloaded system. However, the 13C NMR spectra collected under variable contact time cross-polarization (VCT-CP) conditions showed that the polymeric scaffold CDNS changed significantly its dynamic regime on passing from the empty CDNS to the drug-loaded CDNS, thus showing that the drug encapsulation can be seen as the formation of a real supramolecular aggregate rather than a conglomerate of two solid components. Finally, the structural features obtained from the different solid-state NMR approaches reported matched the information from powder X-ray diffraction profiles.

The Role of Drug-Drug Interactions in Hydrogel Delivery Systems: Experimental and Model Study.

To address the increasing need for improved tissue substitutes, tissue engineering seeks to create synthetic, three-dimensional scaffolds made from polymeric materials able to incorporate cells and drugs. The interpretation of transport phenomena is a key step, but comprehensive theoretical data is still missing and many issues related to these systems are still unsolved. In particular, the contribution of solute-solute interactions is not yet completely understood. Here, we investigate a promising agar-carbomer (AC) hydrogel loaded with sodium fluorescein (SF), a commonly used drug mimetic. The self-diffusion coefficient of SF in AC formulations was measured by using high resolution magic angle spinning NMR spectroscopy (HR-MAS NMR). Starting from experimental data, a complete overview on SF transport properties is provided, in particular a mathematical model that describes and rationalizes the differences between gel and water environments is developed and presented. The hydrogel molecular environment is able to prevent SF aggregation, owing to the adsorption mechanism that reduces the number of monomers available for oligomer formation at low solute concentration. Then, when all adsorption sites are saturated free SF molecules are able to aggregate and form oligomers. The model predictions satisfactorily match with experimental data obtained in water and the gel environment, thus indicating that the model presented here, despite its simplicity, is able to describe the key phenomena governing device behavior and could be used to rationalize experimental activity.

Drug-Polymer Interactions in Hydrogel-based Drug-Delivery Systems: An Experimental and Theoretical Study.

In drug-delivery systems, drug transport is a key step, but the interpretation of the transport mechanism is still controversial. Here, we investigated a promising hydrogel library loaded with the anticonvulsant drug ethosuximide (ESM). The self-diffusion coefficient of ESM was measured using two methods: a direct and advanced measurement with a pulsed field gradient spin-echo (PFGSE) method, using an NMR spectrometer equipped with high-resolution magic angle spinning (HR-MAS) probe, and an indirect one based on fitting in vitro drug-delivery data. Starting from the experimental data a mathematical model without fitted parameters was developed and all the phenomena involved, that is, adsorption and diffusion, were considered. At low drug concentrations, adsorption prevails and consequently the diffusivity in the gels is lower than that in water. At high drug concentrations, where all adsorption sites are saturated, the diffusion in the gels is similar to that in a water solution. This study may pave the way for better device design.

Polydisperse methyl ß-cyclodextrin-epichlorohydrin polymers: variable contact time (13)C CP-MAS solid-state NMR characterization.

The polymerization of partially methylated ß-cyclodextrin (CRYSMEB) with epichlorohydrin was carried out in the presence of a known amount of toluene as imprinting agent. Three different preparations (D1, D2 and D3) of imprinted polymers were obtained and characterized by solid-state (13)C NMR spectroscopy under cross-polarization magic angle spinning (CP-MAS) conditions. The polymers were prepared by using the same synthetic conditions but with different molar ratios of imprinting agent/monomer, leading to morphologically equivalent materials but with different absorption properties. The main purpose of the work was to find a suitable spectroscopic descriptor accounting for the different imprinting process in three homogeneous polymeric networks. The polymers were characterized by studying the kinetics of the cross-polarization process. This approach is based on variable contact time CP-MAS spectra, referred to as VCP-MAS. The analysis of the VCP-MAS spectra provided two relaxation parameters: T CH (the CP time constant) and T 1ρ (the proton spin-lattice relaxation time in the rotating frame). The results and the analysis presented in the paper pointed out that T CH is sensitive to the imprinting process, showing variations related to the toluene/cyclodextrin molar ratio used for the preparation of the materials. Conversely, the observed values of T 1ρ did not show dramatic variations with the imprinting protocol, but rather confirmed that the three polymers are morphologically similar. Thus the combined use of T CH and T 1ρ can be helpful for the characterization and fine tuning of imprinted polymeric matrices.

Anomalous diffusion of Ibuprofen in cyclodextrin nanosponge hydrogels: an HRMAS NMR study.

Ibuprofen sodium salt (IP) was encapsulated in cyclodextrin nanosponges (CDNS) obtained by cross-linking of ß-cyclodextrin with ethylenediaminetetraacetic acid dianhydride (EDTAn) in two different preparations: CDNSEDTA 1:4 and 1:8, where the 1:n notation indicates the CD to EDTAn molar ratio. The entrapment of IP was achieved by swelling the two polymers with a 0.27 M solution of IP in D2O, leading to colourless, homogeneous hydrogels loaded with IP. The molecular environment and the transport properties of IP in the hydrogels were studied by high resolution magic angle spinning (HRMAS) NMR spectroscopy. The mean square displacement (MSD) of IP in the gels was obtained by a pulsed field gradient spin echo (PGSE) NMR pulse sequence at different observation times t d. The MSD is proportional to the observation time elevated to a scaling factor α. The α values define the normal Gaussian random motion (α = 1), or the anomalous diffusion (α < 1, subdiffusion, α > 1 superdiffusion). The experimental data here reported point out that IP undergoes subdiffusive regime in CDNSEDTA 1:4, while a slightly superdiffusive behaviour is observed in CDNSEDTA 1:8. The transition between the two dynamic regimes is triggered by the polymer structure. CDNSEDTA 1:4 is characterized by a nanoporous structure able to induce confinement effects on IP, thus causing subdiffusive random motion. CDNSEDTA 1:8 is characterized not only by nanopores, but also by dangling EDTA groups ending with ionized COO(-) groups. The negative potential provided by such groups to the polymer backbone is responsible for the acceleration effects on the IP anion thus leading to the superdiffusive behaviour observed. These results point out that HRMAS NMR spectroscopy is a powerful direct method for the assessment of the transport properties of a drug encapsulated in polymeric scaffolds. The diffusion properties of IP in CDNS can be modulated by suitable polymer synthesis; this finding opens the possibility to design suitable systems for drug delivery with predictable and desired drug release properties.

Synthesis and characterization of a hyper-branched water-soluble ß-cyclodextrin polymer.

A new hyper-branched water-soluble polymer was synthesized by reacting ß-cyclodextrin with pyromellitic dianhydride beyond the critical conditions that allow the phenomenon of gelation to occur. The molar ratio between the monomers is a crucial parameter that rules the gelation process. Nevertheless, the concentration of monomers in the solvent phase plays a key role as well. Hyper-branched ß-cyclodextrin-based polymers were obtained performing the syntheses with excess of solvent and cross-linking agent, and the conditions for critical dilution were determined experimentally. A hyper-branched polymer with very high water solubility was obtained and fully characterized both as for its chemical structure and for its capability to encapsulate substances. Fluorescein was used as probe molecule to test the complexation properties of the new material.

Unravelling structural information from complex mixtures utilizing correlation spectroscopy applied to HSQC spectra.

The first use of statistical correlation spectroscopy to extract chemical information from 2D-HSQC spectra, termed HSQC correlation spectroscopy (HSQCcos), is reported. HSQCcos is illustrated using heparin, a heterogeneous polysaccharide, whose diverse composition causes signals in HSQC spectra to disperse. HSQCcos has been used to probe the chain modifications that cause this effect and reveals hitherto unreported structural details. An interesting finding was that the signal for position 2 of trisulfated glucosamine [N-, 3-O-, and 6-O-sulfated] (A*) is bifurcated, owing to the presence of A* residues in both the "normal" antithrombin binding site and also at the nonreducing end of the molecule, which is reported in intact heparin for the first time. The method was also applied to investigating the environment around other rare sequences/disaccharides, suggesting that the disaccharide; 2-O-sulfated iduronic acid linked to 6-O-sulfated N-glucosamine, which contains a free amine at position 2, is adjacent to the heparin linkage region. HSQCcos can extract chemically related signals from information-rich spectra obtained from complex mixtures such as heparin.

Are natural deep eutectic solvents always a sustainable option? A bioassay-based study.

The traditional use of organic solvents in various branches of industry is being rethought as these compounds very often display high volatility, toxicity and lipophilicity (related to the ability to interact with biological membranes). More recently, developments in the field of Green Chemistry are focusing on the design of more sustainable and cost-effective solvent alternatives like Ionic Liquids (ILs), bio-based solvents and natural deep eutectic solvents (NADESs). The present study aimed at performing an ecotoxicological screening of 15 NADESs using an extensive set of marine and freshwater bioassays, based on different endpoints as the following: immobilization of the crustacean Daphnia magna, growth inhibition of Raphidocelis subcapitata and of Phaeodactylum tricornutum, larval development alterations on the serpulid Ficopomatus enigmaticus and bioluminescence inhibition of Aliivibrio fischeri. What emerged was a general absence of toxicity of all samples. However, both algal assays showed a certain degree of biostimulation, up to over 100% growth increase in respect to controls with 8 out of 15 compounds tested with Raphidocelis subcapitata. Despite NADESs-induced negligible toxicity effects to invertebrates, encouraging their labelling as "sustainable" solvents, the liability of their intentional or accidental release into aquatic systems may represent a serious risk in terms of ecosystem functioning impairments.

Construction and use of a library of bona fide heparins employing 1H NMR and multivariate analysis.

In contrast to most pharmaceutical agents, the major anticoagulant agent, heparin, lacks a uniquely defined chemical structure. It is an inherently structurally varying, poly-disperse polymer, rendering quality control problematic. Structural modifications introduced during manufacture and the presence of possible contaminants are dangers. The comparison of any heparin test sample to a library of bona fide, but intrinsically variable heparins, is limited fundamentally to measuring the degree of similarity between them. A general approach for constructing a suitable illustrative heparin library employing (1)H NMR and multivariate analysis, is proposed and examples shown. Heparin samples contaminated with non-N-acetylated, persulfated, non-glycosaminoglycan carbohydrates (10%) were detected, some of which would not be easily detected under current regulatory guidelines. The ability to identify contaminated heparin is fundamentally dependent on the contents of the library, which should contain all the 'normal' variability within 'heparin'. Oversulfated chondroitin sulfate can be detected (∼5%) (using components 1 and 2, but is detectable at 3% using additional components, e.g. 1 and 5) analysing the full spectrum and at <1% if only the N-acetyl region is used. Signals arising from oxidation during the manufacturing processes can also be found. The design, properties and limitations of this approach are discussed. Assembly of such a library of market heparin can be termed the 'Current Statistical Definition of Heparin' (CSDH) and will form the basis of future quantitative methods.

Inclusion complexes of tricyclic drugs and ß-cyclodextrin: Inherent chirality and dynamic behaviour.

Amitriptyline (AMT) and cyclobenzaprine (CBZ) are tricyclic drugs used as antidepressant and muscle relaxant, respectively. They show inherently chirality, i.e. they are chiral due to the lack of any symmetry element. As they are used as racemic mixture, diastereomeric inclusion complexes are formed via encapsulation in homochiral ßCD. In this work we show that a suitable combination of NMR methods easily provides details on the chiral recognition, geometry of complexation, rotational dynamics and spatial proximity of selected atom pairs. In particular, we show that 13C NMR can be used to unambiguously assess chiral recognition, demonstrating a higher performance over 1H NMR. The mole fraction of the bound drug and the association constant can be worked out through diffusion experiments, whereas the combination of non-selective, selective and bi-selective relaxation spectra gave insights into the rotational motion of the complexed drug and the spatial proximity of selected proton pairs. The toolkit here proposed provides a thorough characterization of CD/drug inclusion complexes from a physicochemical point of view. This can constructively complement the conventional pharmacological and pharmacokinetic experiments, and can shed light on the understanding of CD/drug formulations.

An Integrated Approach to Optimizing Cellulose Mercerization.

An integrated approach, based on quantitative transmission mode powder X-ray diffraction (PXRD) combined with multivariate statistical analysis, has been applied to cellulose obtained from three different sources to correlate the mercerization degree and crystallinity with the cellulose type, temperature, and reaction time. The effects of the experimental conditions on the two outcomes were studied by design of experiments (DoE) and surface responding analysis (SRA) combined with principal component analysis (PCA). SRA showed a marked influence of the type of cellulose (wood cellulose from the kraft vs. sulfite process, WCK vs. WCS) on the conversion of cellulose I to cellulose II (CII%) during mercerization. A counterintuitive simultaneous effect of temperature and cellulose type was also highlighted. The data elaboration in the form of response surface plots provided an easy predictive tool for the optimum conditions to maximize the conversion. The simulation reported for WCK showed maximum conversion (96%) at 70 °C in 24 h with 18%wt NaOH.

TEMPO-Nanocellulose/Ca2+ Hydrogels: Ibuprofen Drug Diffusion and In Vitro Cytocompatibility.

Stable hydrogels with tunable rheological properties were prepared by adding Ca2+ ions to aqueous dispersions of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-oxidized and ultra-sonicated cellulose nanofibers (TOUS-CNFs). The gelation occurred by interaction among polyvalent cations and the carboxylic units introduced on TOUS-CNFs during the oxidation process. Both dynamic viscosity values and pseudoplastic rheological behaviour increased by increasing the Ca2+ concentration, confirming the cross-linking action of the bivalent cation. The hydrogels were proved to be suitable controlled release systems by measuring the diffusion coefficient of a drug model (ibuprofen, IB) by high-resolution magic angle spinning (HR-MAS) nuclear magnetic resonance (NMR) spectroscopy. IB was used both as free molecule and as a 1:1 pre-formed complex with ß-cyclodextrin (IB/ß-CD), showing in this latter case a lower diffusion coefficient. Finally, the cytocompatibility of the TOUS-CNFs/Ca2+ hydrogels was demonstrated in vitro by indirect and direct tests conducted on a L929 murine fibroblast cell line, achieving a percentage number of viable cells after 7 days higher than 70%.

Innovative applications of waste cooking oil as raw material.

The consideration towards waste cooking oils is changing from hazardous waste to valuable raw material for industrial application. During the last 5 years, some innovative processes based on the employment of recycled waste cooking oil have appeared in the literature. In this review article, the most recent and innovative applications of recycled waste cooking oil are reported and discussed. These include the production of bioplasticizers, the application of chemicals derived from waste cooking oils as energy vectors and the use of waste cooking oils as a solvent for pollutant agents.

Evidence of superdiffusive nanoscale motion in anionic polymeric hydrogels: Analysis of PGSE- NMR data and comparison with drug release properties.

Polymeric hydrogels are promising candidates for drug delivery applications, thanks to their ability to encapsulate, transport and release a wide range of chemicals. The successful application of these materials requires a deep understanding of the mechanisms governing solute transport at the nanoscale and its impact on release kinetics. In this work, we investigate the translational diffusion of ibuprofen loaded in anionic agarose-carbomer (AC) hydrogels by 1H high resolution magic angle spinning (HR-MAS) NMR spectroscopy, and compare it to its macroscopic release kinetics. The analysis of the experimental NMR data provides the first evidence of superdiffusion for ibuprofen in AC hydrogels. Superdiffusive transport is observed in the majority of our samples, especially those with the smallest mesh size (7 nm) and highest ibuprofen concentrations (90-120 mg/mL). This outcome is rationalized in terms of heavy-tailed distributions of spatial displacements (Lèvy flights) and of waiting times, which depend on the nanoscopic structural heterogeneity of the gels and the strong but reversible association between ibuprofen and the agarose matrix.

Improving the recycling technology of waste cooking oils: Chemical fingerprint as tool for non-biodiesel application.

Samples of sunflower Waste Cooking Oils (WCOs) subjected to several cycles of frying were treated with water under four different combinations of temperature and pH. Several aspects of the chemical composition of edible, non-treated and processed samples was determined by three different analytic techniques: headspace Solid-Phase Microextraction (HS-SPME) coupled with gas-chromatography (GC), 1H NMR spectroscopy and ESI-MS spectrometry. Thus, a characteristic chemical fingerprint of each sample was derived and proposed as useful set of tools for the optimization of recycling of WCOs. On the basis of the presented results, a mini-plant for the production of bio-lubricants and bio-solvents with a circular economy approach was designed and herein described.

NMR Metabolomics for Stem Cell type discrimination.

Cell metabolism is a key determinant factor for the pluripotency and fate commitment of Stem Cells (SCs) during development, ageing, pathological onset and progression. We derived and cultured selected subpopulations of rodent fetal, postnatal, adult Neural SCs (NSCs) and postnatal glial progenitors, Olfactory Ensheathing Cells (OECs), respectively from the subventricular zone (SVZ) and the olfactory bulb (OB). Cell lysates were analyzed by proton Nuclear Magnetic Resonance (1H-NMR) spectroscopy leading to metabolites identification and quantitation. Subsequent multivariate analysis of NMR data by Principal Component Analysis (PCA), and Partial Least Square Discriminant Analysis (PLS-DA) allowed data reduction and cluster analysis. This strategy ensures the definition of specific features in the metabolic content of phenotypically similar SCs sharing a common developmental origin. The metabolic fingerprints for selective metabolites or for the whole spectra demonstrated enhanced peculiarities among cell types. The key result of our work is a neat divergence between OECs and the remaining NSC cells. We also show that statistically significant differences for selective metabolites characterizes NSCs of different ages. Finally, the retrived metabolome in cell cultures correlates to the physiological SC features, thus allowing an integrated bioengineering approach for biologic fingerprints able to dissect the (neural) SC molecular specificities.

Transport Properties of Ibuprofen Encapsulated in Cyclodextrin Nanosponge Hydrogels: A Proton HR-MAS NMR Spectroscopy Study.

The chemical cross-linking of ß-cyclodextrin (ß-CD) with ethylenediaminetetraacetic dianhydride (EDTA) led to branched polymers referred to as cyclodextrin nanosponges (CDNSEDTA). Two different preparations are described with 1:4 and 1:8 CD-EDTA molar ratios. The corresponding cross-linked polymers were contacted with 0.27 M aqueous solution of ibuprofen sodium salt (IP) leading to homogeneous, colorless, drug loaded hydrogels. The systems were characterized by high resolution magic angle spinning (HR-MAS) NMR spectroscopy. Pulsed field gradient spin echo (PGSE) NMR spectroscopy was used to determine the mean square displacement (MSD) of IP inside the polymeric gel at different observation times td. The data were further processed in order to study the time dependence of MSD: MSD = f(td). The proposed methodology is useful to characterize the different diffusion regimes that, in principle, the solute may experience inside the hydrogel, namely normal or anomalous diffusion. The full protocols including the polymer preparation and purification, the obtainment of drug-loaded hydrogels, the NMR sample preparation, the measurement of MSD by HR-MAS NMR spectroscopy and the final data processing to achieve the time dependence of MSD are here reported and discussed. The presented experiments represent a paradigmatic case and the data are discussed in terms of innovative approach to the characterization of the transport properties of an encapsulated guest within a polymeric host of potential application for drug delivery.