Extraction of high-quality grade cellulose and cellulose nanocrystals from different lignocellulosic agri-food wastes

Introduction

Prompted by the increasing need for an intensified valorization of agri-food waste, in this work a three-step chemical procedure was used to extract high-purity cellulose from garlic stalk, corncob, and giant cane cut-up by a sequential removal of hemicellulose, lignin, ash, and organic compounds. Cellulose nanocrystals of potential interest for nanocomposite applications were then obtained through acid hydrolysis.

Methods

The purity of the cellulose was determined employing Nuclear Magnetic Resonance and infrared spectroscopy, whereas dynamic light scattering, optical, atomic force microscopy, and transmission electron microscopy were used for morphological characterization. The high purity and crystallinity of cellulose was confirmed by comparison with the ultra-pure bacterial cellulose originating from K. sucrofermentans, irrespective of the waste used.

Results and discussion

At the end of the extraction procedure, cellulose yields of 35.73, 37.15, and 39.10%, for garlic stalk, corncob, and giant cane cut-up, respectively, were achieved. Dynamic light scattering and atomic force microscopy analyses showed that the length of the whisker-like nanocrystals depended on the raw material (from ~100 nm up to > 2μm), while the final yield was ~40–50% for all three wastes. The versatility and effectiveness of the method here proposed can be profitably used for a wide range of agro-waste feedstocks.

Multivalent γ-PGA-Exendin-4 conjugates to target pancreatic β-cells

Targeting of glucagon‐like peptide 1 receptor (GLP‐1R), expressed on the surface of pancreatic β‐cells, is of great interest for the development of advanced therapies for diabetes and diagnostics for insulinoma. We report the conjugation of exendin‐4 (Ex‐4), an approved drug to treat type 2 diabetes, to poly‐γ‐glutamic acid (γ‐PGA) to obtain more stable and effective GLP‐1R ligands. Exendin‐4 modified at Lysine‐27 with PEG4‐maleimide was conjugated to γ‐PGA functionalized with furan, in different molar ratios, exploiting a chemoselective Diels‐Alder cycloaddition. The γ‐PGA presenting the highest number of conjugated Ex‐4 molecules (average 120 per polymeric chain) showed a double affinity towards GLP‐1R with respect to exendin per se, paving the way to improved therapeutic and diagnostic applications.

Antioxidant Properties of Agri-food Byproducts |and Specific Boosting Effects of Hydrolytic Treatments

Largely produced agri-food byproducts represent a sustainable and easily available source of phenolic compounds, such as lignins and tannins, endowed with potent antioxidant properties. We report herein the characterization of the antioxidant properties of nine plant-derived byproducts. 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing/antioxidant power (FRAP) assays indicated the superior activity of pomegranate peels and seeds, grape pomace and pecan nut shell. An increase in the antioxidant potency was observed for most of the waste materials following a hydrolytic treatment, with the exception of the condensed tannin-rich pecan nut shell and grape pomace. UV-Vis and HPLC investigation of the soluble fractions coupled with the results from IR analysis and chemical degradation approaches on the whole materials allowed to conclude that the improvement of the antioxidant properties was due not only to removal of non-active components (mainly carbohydrates), but also to structural modifications of the phenolic compounds. Parallel experiments run on natural and bioinspired model phenolic polymers suggested that these structural modifications positively impacted on the antioxidant properties of lignins and hydrolyzable tannins, whereas significant degradation of condensed tannin moieties occurred, likely responsible for the lowering of the reducing power observed for grape pomace and pecan nut shell. These results open new perspectives toward the exploitation and manipulation of agri-food byproducts for application as antioxidant additives in functional materials.

Coupling quaternary ammonium surfactants to the surface of liposomes improves both antibacterial efficacy and host cell biocompatibility

By functionalizing the surface of PEG-liposomes with linkers bearing quaternary ammonium compounds (QACs), we generated novel bacteria disruptors with anti-adhesive properties and reduced cytotoxicity compared to free QACs. Furthermore, QAC-functionalized liposomes are a promising platform for future drug encapsulation. The QAC (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide (MTAB) was attached to maleimide-functionalized liposomes (DSPE-PEG) via thiol linker. The MTAB-functionalized liposomes were physicochemically characterized and their biological activity, in terms of anti-adherence activity and biofilm prevention in Escherichia coli were assessed. The results showed that MTAB-functionalized liposomes inhibit bacterial adherence and biofilm formation while reducing MTAB toxicity.

Green-Emitting Powders of Zero-Dimensional Cs4PbBr6: Delineating the Intricacies of the Synthesis and the Origin of Photoluminescence

A detailed investigation into the synthesis of green-emitting powders of Cs₄PbBr₆ and CsPbBr₃ materials by antisolvent precipitation from CsBr-PbBr₂ precursor solutions in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is reported. Various solvated lead bromide and polybromide species (PbBr₂, [PbBr₃]^-, [PbBr₄]^2-, and possibly [PbBr₅]^3-or [PbBr₆]^4-) are detected in the precursor solutions by optical absorbance and emission spectroscopies. The solvodynamic size of the species in solution is strongly solvent-dependent: ~1 nm species were detected in DMSO, while significantly larger species were observed in DMF by dynamic light scattering. The solvodynamic size of the lead bromide species plays a critical role in determining the Cs-Pb-Br composition of the precipitated powders: smaller species favor the precipitation of Cs₄PbBr₆, while larger species template the formation of CsPbBr₃ under identical experimental conditions. The powders have been characterized by ¹³³Cs and ²⁰⁷Pb solid-state nuclear magnetic resonance, and ¹³³Cs sensitivity toward the different Cs environments within Cs₄PbBr₆ is demonstrated. Finally, the possible origins of green emission in Cs₄PbBr₆ samples are discussed. It is proposed that a two-dimensional Cs₂PbBr₄ inclusion may be responsible for green emission at ~520 nm in addition to the widely acknowledged CsPbBr₃ impurity, although we found no conclusive experimental evidence supporting such claims.

Mechanical and Drug Release Properties of Sponges from Cross-linked Cellulose Nanofibers

All-organic porous sponges were obtained throughout the direct and solvent-free (oven 105 °C, time>6 h) crosslinking of TEMPO-oxidized cellulose nanofibers (TOCNF) with 25 kDa branched polyethyleneimine (bPEI) in the presence of different amounts of citric acid (CA) as co-crosslinker. The chemical and mechanical stability of these materials was provided by the formation of amide bonds between the carboxylic moieties of TOCNF and CA with the primary amines of bPEI. The mechanical properties were investigated under static and dynamic loads with both dry and wet samples. The materials had the interesting capability to recover their shape with reduced losses in mechanical resistance, while their Young's modulus progressively increased with the content of CA. In work toward developing possible applications of bPEI-TOCNF sponges in drug delivery, amoxicillin (AM) and ibuprofen (IB) were considered as model drugs. All materials showed very good performance in adsorbing both AM and IB (ca. 200 mg g^-1 ) from methanol solution. In particular, an increased adsorption of IB was observed in parallel to the increase of citrate moieties in the samples. Moreover, samples crosslinked in presence of CA showed slower kinetic release in aqueous environments than materials obtained without CA.

Powering tyrosol antioxidant capacity and osteogenic activity by biocatalytic polymerization

Oxidative polymerization of tyrosol afforded a mixture of oligomers (OligoTyr) which proved to be more active than tyrosol as antioxidant and as stimulator of alkaline phosphatase (ALP) activity when loaded into polylactic acid (PLA) scaffolds.

Magnetic iron oxide nanoparticle functionalization: isocyanate moiety as a suitable monodentate anchoring group

A new strategy for anchoring organic molecules onto superparamagnetic iron oxide nanoparticles (SPIONs) using isocyanate containing linkers has been realized. This functional group easily and efficiently reacts with the hydroxyl residues of the nanoparticle surface, leading to the formation of a stable carbamate bond, as confirmed by means of spectroscopic and analytical data.

An antioxidant bioinspired phenolic polymer for efficient stabilization of polyethylene

The synthesis, structural characterization and properties of a new bioinspired phenolic polymer (polyCAME) produced by oxidative polymerization of caffeic acid methyl ester (CAME) with horseradish peroxidase (HRP)-H2O2 is reported as a new sustainable stabilizer toward polyethylene (PE) thermal and photo-oxidative degradation. PolyCAME exhibits high stability toward decarboxylation and oxidative degradation during the thermal processes associated with PE film preparation. Characterization of PE films by thermal methods, photo-oxidative treatments combined with chemiluminescence, and FTIR spectroscopy and mechanical tests indicate a significant effect of polyCAME on PE durability. Data from antioxidant capacity tests suggest that the protective effects of polyCAME are due to the potent scavenging activity on aggressive OH radicals, the efficient H-atom donor properties inducing free radical quenching, and the ferric ion reducing ability. PolyCAME is thus proposed as a novel easily accessible, eco-friendly, and biocompatible biomaterial for a sustainable approach to the stabilization of PE films in packaging and other applications.

Conformation of the tridimensional structure of 1,2,3,4,6-pentagalloyl-β-D-glucopyranose (PGG) by (1)H NMR, NOESY and theoretical study and membrane interaction in a simulated phospholipid bilayer: a first insight

1,2,3,4,6-Penta-O-galloyl-β-D-glucopyranose (PGG) is a polyphenolic compound found in substantial amounts in a number of medicinal herbs. We report (i) its conformational analysis by solution NMR and molecular dynamics calculation and (ii) theoretical study of its interaction with a model membrane bilayer. The galloyl groups B and E appear to play important roles in the interaction with the phospholipid bilayer.

Phagocytosis of biocompatible gold nanoparticles

We report the evidence for the cellular uptake of gold nanoparticles via the phagocytosis mechanism in murine macrophage cells strongly supported by TEM and optical microscopy. Nanoparticles were prepared using several biocompatible molecules of choice (5-aminovaleric acid, l-DOPA, melatonin, and serotonin hydrochloride) as stabilizers for gold colloids. Their surface chemistry was fully characterized by UV-vis, ATR-FTIR, (1)H NMR, and HR-MAS (1)H NMR spectroscopies, and size distribution was determined by CPS disc centrifuge and TEM. Differences in coatings were evaluated against cellular uptake, and a preferential movement of macrophages toward 5-aminovaleric acid-modified gold nanoparticles was shown, leading to the fast accumulation of nanoparticles in the cytosol.

Magnetic peptide nucleic acids for DNA targeting

A versatile synthetic platform for the efficient immobilization of PNAs on magnetic iron oxides, providing magnetic nanosensors for selective DNA recognition, is presented.

Gold nanoparticles prepared using cape aloe active components

A novel use of two components of Cape aloe, aloin A and aloesin, acting as stabilizers in the preparation of gold and silver nanoparticles, is reported. Stable water-soluble particles of different size and shape are prepared by varying the reaction conditions, temperature, reaction time, and reducing agents. Characterization of the obtained particles is performed using UV-visible, attenuated total reflection Fourier transform infrared (ATR-FTIR), and 1H NMR spectroscopies and transmission electron microscopy (TEM). The efficient cellular uptake of 50 nm sized aloin A and aloesin stabilized gold particles into macrophages and HeLa cells was investigated, proposing these particles as nanovehicles.

Structure elucidation and NMR assignments of two new pyrrolidinyl quinoline alkaloids from chestnut honey

The complete (1)H, (13)C and (15)N NMR spectral assignments of two new alkaloids isolated from chestnut honey and structurally related to kynurenic acid have been made using 1-D and 2-D NMR techniques, including COSY, HMQC and HMBC experiments. The new compounds have been identified as 3-(2'-pyrrolidinyl)-kynurenic acid and its gamma-lactam derivative.

Thiol-disulfide redox equilibria of glutathione metaboloma compounds investigated by tandem mass spectrometry

The thiol group of cysteine plays a pivotal role in structural and functional biology. We use mass spectrometry to study glutathione-related homo- and heterodimeric disulfides, aiming at understanding the factors affecting the redox potentials of different disulfide/thiol pairs. Several electrospray ionization (ESI)-protonated disulfides of cysteamine, cysteine, penicillamine, N-acetylcysteine, N-acetylpenicillamine, gammaGluCySH, HSCyGly, and glutathione were analyzed on a triple quadrupole instrument to measure their energy-resolved tandem mass spectra. Fission of the disulfide bond yields RSH*H(+) and RS(+) ions. The logarithm of the intensity ratio of the RS(+)/RSH*H(+) fragments in homodimeric disulfides is proportional to the normal reduction potential of their RSSR/RSH pairs determined by nuclear magnetic resonance (NMR) in solution, the more reducing ones yielding the higher ratios. Also in some R(1)S-SR(2) disulfides, the ratio of the intensities of the RSH + H(+) and RS(+) ions of each participating thiol shows a linear relationship with the Nernst equation potential difference of the corresponding redox pairs. This behavior allows us to measure the redox potentials of some disulfide/thiol pairs by using different thiol-reducing probes of known oxidoreductive potential as reference. To assist understanding of the fission mechanism of the disulfide bond, the fragments tentatively identified as 'sulfenium' were themselves fragmented; accurate mass measurement of the resulting second-generation fragments demonstrated a loss of thioformaldehyde, thus supporting the assigned structure of this elusive intermediate of the oxidative stress pathway. Understanding this fragmentation process allows us to employ this technique with larger molecules to measure by mass spectrometry the micro-redox properties of different disulfide bonds in peptides with catalytic and signaling biological activity.

Kynurenic acid in honey from arboreal plants: MS and NMR evidence

KYNA, a Trp metabolite, shows neuroprotective activity against excitotoxic amino acids by antagonizing the NMDA receptor (glycine, glutamate). Here we report the identification of KYNA by a combination of ESI-MS/MS and 1D- and 2D-NMR analyses in honey varieties of arboreal origin. KYNA are absent in single-flower honeys from herbal flowers. These different distribution patterns might possibly involve an indirect plant defence mechanism against fungal pathogens and herbivorous parasites, ever-present on wild trees. The presence of KYNA in honey may explain its pain-relieving effects reported in the literature. The substance, acting in concert with honey flavonoids (COX-2 inhibitors), by antagonizing the NMDA receptor may contribute to the antinociceptive effect of honey. Moreover, kynureninates, owing to their antimicrobial properties, can favour the successful outcome of wounds and burns.

NMR evidence for the participation of triflated ionic liquids in glycosylation reaction mechanisms

A systematic low-temperature NMR study of a glycosylation reaction was performed in the presence of different ionic liquids and acidic catalysts. The influence of the triflate anion derived from [emim][OTf] on the stereochemistry of the glycosylation products was evaluated.

Glycosylation with Trichloroacetimidates in Ionic Liquids: Influence of the Reaction Medium on the Stereochemical Outcome

[reactions: see text] The glycosylation with trichloroacetimidates derived from different glycopyranoses bearing a nonparticipating group at C-2 was explored in different ionic liquids as solvents. The stereoselectivity of the reaction was significantly affected by the reaction media and by the anomeric configuration of the donor.

Synthesis and characterization of a penicillin-poly(L-lysine) which recognizes human IgE anti-penicillin antibodies

Conjugates of poly(L-lysine) containing a penicillin or a penicilloyl residue were prepared and characterized by 1H NMR and by size-exclusion HPLC. These conjugates and conjugates with human serum albumin were used in radioallergosorbent tests (RAST) for the determination of allergy toward penicillins.