Periodate oxidation of polysaccharides for modification of chemical and physical properties

Swelling Behavior, Interaction, and Electrostatic Properties of Chitosan/Alginate Dialdehyde Multilayer Films with Different Outermost Layer

In this study, self-cross-linked chitosan/alginate dialdehyde multilayer films, capped with either alginate dialdehyde (6 layers) or chitosan (7 layers), were fabricated using the layer-by-layer method. The disruption of the electrostatic equilibrium when exposing the fabricated layers to acidic and alkaline conditions causes swelling within the film and independently in the outermost layer, showing dependence on the ionic strength. Spectroscopic ellipsometry and quartz crystal microbalance with dissipation monitoring were employed to examine the swelling behavior. Atomic force microscopy colloidal probe measurements were conducted to assess the surface forces between the multilayer films at different pH and ionic strengths. Finally, the electrostatic properties of the multilayer films were examined at different pH and ionic strengths using zeta potential measurements. The results suggest that stimuli-responsiveness and overall swelling behavior of the polysaccharide multilayer films significantly depend on the outermost layer, an effect that should expectedly become more pronounced the thinner the film becomes.

Self-Fibrillating Cellulose Fibers: Rapid In Situ Nanofibrillation to Prepare Strong, Transparent, and Gas Barrier Nanopapers

Cellulose nanofibrils (CNFs) prepared from wood biomass are promising candidates to replace oil-based materials in, for example, packaging applications. However, CNFs’ affinity for water combined with their small size leads to very slow and energy-demanding processes for handling and removal of water. To a large extent, this is the major roadblock that prevents a feasible production of dry CNF-based materials on an industrial scale. In this work, self-fibrillating fibers (SFFs) from wood, where the fibrils can be liberated by external stimuli, were prepared via sequential TEMPO and periodate oxidation reactions. Papers made from these modified fibers using conventional laboratory papermaking methods were then in situ nanofibrillated via a modest pH increase. With a dewatering time of less than 10 s for a 3 g/L dispersion, SFFs represent a major improvement over conventional CNF nanopapers that take approximately 6 h to dewater. Moreover, 100 g/m² nanopapers obtained through in situ fibrillation exhibited comparable, if not superior, properties to those reported for conventionally made CNF films. A tensile strength of 184 MPa, a Young’s modulus of 5.2 GPa, a strain at break of 4.6%, 90% optical transmittance, and an oxygen permeability of 0.7 cm³ μm m^–2 d^–1 kPa^–1 at 50% RH were measured for SFF nanopapers. Furthermore, in situ nanofibrillation of the SFFs can also be achieved from already dried papers, facilitating numerous possibilities in terms of logistics and handling for an industrial scale-up and transportation of nanomaterials. Overall, stimuli-induced SFFs indeed enable a rapid production of strong, transparent, gas barrier nanopapers, which likely can be industrially scaled up and eventually compete with the oil-based plastics in the market for packaging materials.

Bile acid-retention by native and modified oat and barley β-glucan

Foods rich in cereal β-glucan are efficient dietary tools to help reduce serum cholesterol levels and hence the risk of cardiovascular diseases. However, β-glucan undergoes various reactions during food processing, which alter its viscous properties and interactions with components of the gastrointestinal tract. It has been proposed in the literature that oxidation and partial hydrolysis increase β-glucan's bile acid-binding activity, and therefore its effectiveness in lowering cholesterol. Here, the passage kinetics of a bile salt mix across a dialysis membrane was studied with or without oat and barley β-glucan extracts, native or modified (partial hydrolysis and oxidations by sodium periodate or TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)). Bile acid-retention turned out to be purely a function of viscosity, with the most viscous native extracts exhibiting the strongest retardation of bile acid permeation. Opposite of what was suggested in the literature, oxidation and molecular weight reduction do not seem to increase the bile acid-binding capability of β-glucan.

Succinoglycan dialdehyde-reinforced gelatin hydrogels with toughness and thermal stability

Pure gelatin hydrogel (PG) has limited practical applications due to their thermal instability and unfavorable mechanical properties. To overcome these limitations, dually crosslinked hydrogels were developed by imparting chemical crosslinking to existing physically crosslinked gelatin hydrogel networks using succinoglycan dialdehyde (SGDA) as a macromolecular crosslinker. SGDA-reinforced gelatin hydrogels (SGDA/Gels) displayed an 11 times higher compressive stress under identical deformation strain and a 1040% improvement in storage modulus (G') than PG. In addition, chemical crosslinking induced by SGDA increased the thermal stability of SGDA/Gels, such that they did not decompose at 60 °C, as confirmed by oscillatory temperature ramp experiments. The newly synthesized SGDA/Gels with reinforced networks and thermal stability exhibit potential for long-term use as controlled drug delivery carriers and 3D cell culture scaffolds for tissue engineering.

In situ forming hydrogel of natural polysaccharides through Schiff base reaction for soft tissue adhesive and hemostasis

In this study, a novel injectable hydrogel with biocompatibility and biodegradability through Schiff base reaction was prepared for soft tissue adhesive and hemostasis. Aldehyde hydroxyethyl starch (AHES) was prepared by oxidizing hydroxyethyl starch to get aldehyde groups. Amino carboxymethyl chitosan (ACC) was prepared by grafting ethylenediamine onto carboxymethyl chitosan to get more amino groups. Two-component AHES/ACC hydrogel was formed through Schiff base reaction between aldehyde and amino groups. By changing the reaction conditions various contents of aldehyde and amino group were achieved. The properties of AHES/ACC hydrogel were tunable including gelation time, swelling ratio, degradation and mechanical tensile by varying the content of aldehyde and amino groups. Then biocompatibility measurements showed that AHES/ACC hydrogels supported cell viability and proliferation in vitro and exhibited good biodegradability and biocompatibility in vivo. AHES/ACC hydrogel also had effective hemostatic ability. Thus, this study provides a strategy for the design and fabrication of fast in situ forming hydrogels. Through Schiff base reaction in situ forming hydrogel derived from natural polysaccharides can be modulated and prepared for soft tissue adhesive, hemostasis or other biomedical applications in future.

Chemical Modification of Alginate for Controlled Oral Drug Delivery

Here, we report two methods that chemically modify alginate to achieve neutral-basic pH sensitivity of the resultant hydrogel. The first method involves direct amide bond formation between alginate and 4-(2-aminoethyl)benzoic acid. The second method that arose out of the desire to achieve better control of the degradation rate of the alginate hydrogel involves reductive amination of oxidized alginate. The products of both methods result in a hydrogel vehicle for targeted delivery of encapsulated payload under physiological conditions in the gastrointestinal tract. Two-dimensional diffusion-ordered spectroscopy and internal and coaxial external nuclear magnetic resonance standards were used to establish chemical bonding and percent incorporation of the modifying groups into the alginate polymer. The hydrogel made with alginate modified by each method was found to be completely stable under acidic pH conditions while disintegrating within minutes to hours in neutral-basic pH conditions. We found that, while alginate oxidation did not affect the β-d-mannuronate/α-l-guluronate ratio of alginate, the rate of disintegration of the hydrogel made with oxidized alginate was dependent upon the degree of oxidation.

Preparation and Characterization of Oxidized Inulin Hydrogel for Controlled Drug Delivery

Inulin-based hydrogels are useful carriers for the delivery of drugs in the colon-targeted system and in other biomedical applications. In this project, inulin hydrogels were fabricated by crosslinking oxidized inulin with adipic acid dihydrazide (AAD) without the use of a catalyst or initiator. The physicochemical properties of the obtained hydrogels were further characterized using different techniques, such as swelling experiments, in vitro drug release, degradation, and biocompatibility tests. The crosslinking was confirmed with Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). In vitro releases of 5-fluorouracil (5FU) from the various inulin hydrogels was enhanced in acidic conditions (pH 5) compared with physiological pH (pH 7.4). In addition, blank gels did not show any appreciable cytotoxicity, whereas 5FU-loaded hydrogels demonstrated efficacy against HCT116 colon cancer cells, which further confirms the potential use of these delivery platforms for direct targeting of 5-FU to the colon.

Preparation and chromatographic performance of a multifunctional immobilized chiral stationary phase based on dialdehyde microcrystalline cellulose derivatives

A novel high-performance liquid chromatography (HPLC) multifunctional immobilized chiral stationary phase was prepared by bonding dialdehyde microcrystalline cellulose to aminosilica via Schiff base reaction and then derivatized with 3,5-dimethylphenyl isocyanate. The HPLC multifunctional immobilized chiral stationary phase could not only achieve chiral separation but also achieve achiral separation. Chiral separation evaluation showed that 1-(1-naphthyl)ethanol and mandelonitrile got separation in normal phase (NP) mode. Ranolazine, benzoin ethyl ether, metalaxyl, and diclofop were successfully separated in reversed phase (RP) mode. Aromatic compounds such as polycyclic aromatic hydrocarbons (PAHs), anilines, and aromatic acids were selected as analytes to investigate the achiral separation performance of the multifunctional immobilized chiral stationary phase in NP and RP modes. The achiral separation evaluation showed that six PAHs could get good separation within 10 minutes in NP mode. Four aromatic acids were well separated in RP mode. The retention mechanism of aromatic compounds on the stationary phase was discussed, founding that π-π interaction, π-π electron-donor-acceptor (EDA) interaction, and hydrogen bonding interaction played important roles during the achiral separation process. This multifunctional immobilized chiral stationary phase had the advantages of simple bonding steps, short reaction time, and no need for space arm.

Molecular Assemblies of Biomimetic Microcapsules

Layer-by-layer (LbL) assembly is a most commonly used method to prepare various microcapsules based on the electrostatic interactions, hydrogen bonding, covalent bonding, and so on. Among these interactions, Schiff base bond formed in covalent assembly not only has an advantage in stability, but also enables the assembled microcapsules with autofluorescence and pH sensitivity. In this Article, we will mainly describe the construction of biomimetic microcapsules through Schiff base mediated LbL assembly. The structures and properties of the assembled microcapsules are introduced and their applications as drug carriers are highlighted.

Efficient Grafting of Cyclodextrin to Alginate and Performance of the Hydrogel for Release of Model Drug

Controlling the rate of release of molecules from a hydrogel is of high interest for various drug delivery systems and medical devices. A strategy to alter the release profiles of soluble and poorly soluble active ingredients from hydrogels can be to combine the hydrogel forming ability of alginate with the inclusion forming ability of cyclodextrins (CyD). Here, β-CyD was grafted to alginate in a three-step synthesis using periodate oxidation, reductive amination and copper(I)-catalyzed azide-alkyne cycloaddition. A grafting degree of 4.7% mol β-CyD/mol sugar residues was obtained. The grafting degree was controlled by varying the reaction parameters where the amount of linker used in reductive amination was especially influential. Ca-alginate gel beads grafted with β-CyD showed increased uptake of the model molecule methyl orange. Release experiments showed that the grafted material had a prolonged release of methyl orange and an increased total amount of released methyl orange. These results show that the β-CyD grafted alginate is still able to form a hydrogel while the grafted cyclodextrins retain their ability to form inclusion complex with methyl orange. Further testing should be done with this system to investigate capability for drug delivery applications.

Nanoplatform Constructed from a β-Glucan and Polydeoxyadenylic Acid for Cancer Chemotherapy and Imaging

A nanoplatform carrying doxorubicin (Dox) for cancer therapy and a dye for imaging was developed based on a natural triple helix β-glucan (t-LNT) and polydeoxyadenylic acid (poly(dA)). The t-LNT-Dox conjugates were prepared through Schiff-base reaction between the aldehyde group in the oxidized t-LNT and the amino group of Dox, the single chains (s-LNT-Dox) of which interacted with the poly(dA)-dye to form a composite s-LNT-Dox/poly(dA)-dye through hydrogen bonding between s-LNT and poly(dA). t-LNT-Dox was confirmed to acid-responsively release Dox in vitro, showing enhanced cytotoxicity against HeLa cancer cells with time. It was confirmed that Dox and the dye could be simultaneously delivered into HeLa cells or the tumors with a prolonged duration time. Furthermore, LNT-Dox conjugates effectively inhibited tumor growth and decreased adverse effects of the free Dox in vivo. Hence, this work develops a new strategy to fabricate the nanoplatform for therapy and imaging using a natural polysaccharide.

Design of biostable scaffold based on collagen crosslinked by dialdehyde chitosan with presence of gallic acid

In this study, we have prepared the biostable collagen scaffold which is crosslinked by dialdehyde chitosan (DAC) with presence of Gallic acid (GA) and characterized its physico-chemical, biostable and biocompatible properties. The digital photographic and scanning electron microscopic (SEM) images of the prepared collagen scaffold is exposed well with properly oriented interconnected porous natured structure. The appearance of diffraction peaks showed slightly crystalline characteristic when compared to others. The differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA) measurements indicates well significantly increased denaturation temperature (T_D) and decreased decomposition rate. FT-IR result suggests the structural integrity of collagen which favours the molecular stability. The dialdehyde groups from DAC crosslinked with collagen functional groups that increase the molecular crosslinking owing to the large number of amino groups in its molecular chain. This scaffold exhibited 87% resistance against collagenolytic degradation by collagenase. The results showed that the improved biostability which prevents the free access of the collagenase to binds with the collagen triple helical chains. This scaffold confirm high biocompatibilities; enhanced cell proliferation and adhesions properties. This results gains new insight into the collagen scaffold to improves the biostability. This could be suitable method to preparation of collagenous biomaterials for tissue engineering applications.

Biocatalytic Production of Amino Carbohydrates through Oxidoreductase and Transaminase Cascades

Plant-derived carbohydrates are an abundant renewable resource. Transformation of carbohydrates into new products, including amine-functionalized building blocks for biomaterials applications, can lower reliance on fossil resources. Herein, biocatalytic production routes to amino carbohydrates, including oligosaccharides, are demonstrated. In each case, two-step biocatalysis was performed to functionalize d-galactose-containing carbohydrates by employing the galactose oxidase from Fusarium graminearum or a pyranose dehydrogenase from Agaricus bisporus followed by the ω-transaminase from Chromobacterium violaceum (Cvi-ω-TA). Formation of 6-amino-6-deoxy-d-galactose, 2-amino-2-deoxy-d-galactose, and 2-amino-2-deoxy-6-aldo-d-galactose was confirmed by mass spectrometry. The activity of Cvi-ω-TA was highest towards 6-aldo-d-galactose, for which the highest yield of 6-amino-6-deoxy-d-galactose (67 %) was achieved in reactions permitting simultaneous oxidation of d-galactose and transamination of the resulting 6-aldo-d-galactose.

Structural Investigation of a Self-Cross-Linked Chitosan/Alginate Dialdehyde Multilayered Film with in Situ QCM-D and Spectroscopic Ellipsometry

A chitosan/alginate dialdehyde multilayered film was fabricated using the layer-by-layer assembly method. Besides electrostatic interaction that promotes alternate adsorption of the oppositely charged polyelectrolytes, the Schiff base reaction between the amine groups on chitosan and the aldehyde groups on alginate dialdehyde provides a covalently cross-linked film, which after reduction by sodium cyanoborohydride is stable under both acidic and alkaline conditions. Moreover, the cross-linked film is responsive to changes in pH and addition of multivalent salts. The structural properties of the multilayered film such as thickness, refractive index, and water content were examined using simultaneous quartz crystal microbalance with dissipation monitoring and spectroscopic ellipsometry.

Characterization, Antimicrobial Properties and Coatings Application of Gellan Gum Oxidized with Hydrogen Peroxide

The effect of hydrogen peroxide (H₂O₂) oxidation on the physicochemical, gelation and antimicrobial properties of gellan gum was studied. The oxidized gellan gum (OGG) was characterized by measuring the carboxyl/carbonyl group contents, Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. The H₂O₂ oxidation resulted in a large increase in the carboxyl groups in gellan gum. The OGG lost gelation ability by oxidation even in the presence of metal ions. The antimicrobial activities of the OGG against Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli), and fungal (Aspergillus niger) were tested. The OGG could inhibit the growth of both bacteria and fungal, and the activity was improved with an increase in the oxidation level. Finally, the application of the OGG as an active coatings material to extend the storage of apples was tested.

Quantitative glycomics using liquid phase separations coupled to mass spectrometry

Post-translational modification of proteins by the attachment of glycans is governed by a variety of highly specific enzymes and is associated with fundamental impacts on the parent protein's physical, chemical and biological properties. The inherent connection between cellular physiology and specific glycosylation patterns has been shown to offer potential for diagnostic and prognostic monitoring of altered glycosylation in the disease state. Conversely, glycoprotein based biopharmaceuticals have emerged as dominant therapeutic strategies in the treatment of intricate diseases. Glycosylation present on these biopharmaceuticals represents a major critical quality attribute with impacts on both pharmacokinetics and pharmacodynamics. The structural variety of glycans, based upon their non-template driven assembly, poses a significant analytical challenge for both qualitative and quantitative analysis. Labile monosaccharide constituents, isomeric species and often low sample availability from biological sources necessitates meticulous sample handling, ultra-high-resolution analytical separation and sensitive detection techniques, respectively. In this article a critical review of analytical quantitation approaches using liquid phase separations coupled to mass spectrometry for released glycans of biopharmaceutical and biomedical significance is presented. Considerations associated with sample derivatisation strategies, ionisation, relative quantitation through isotopic as well as isobaric labelling, metabolic/enzymatic incorporation and targeted analysis are all thoroughly discussed.

Efficient, Self-Terminating Isolation of Cellulose Nanocrystals through Periodate Oxidation in Pickering Emulsions

Many efforts have been made to isolate native nanocrystals from raw materials in the last two decades, such as cellulose nanocrystals (CNCs), but existing methods still suffer from low yields, complicated synthesis processes, and nonuniform sizes of obtained CNCs. This study concerns a facile, self-terminating, and efficient method for the formation of uniform CNCs in high yields during the periodate oxidation process within Pickering emulsions. A biphasic system containing hexane with dissolved hexylamine and an aqueous solution of sodium periodate (NaIO₄ ) was used as the reaction medium. Regulated by hexylamine, owing to its limited solubility in water, the pH value of the aqueous phase was enhanced to around 9.8, leading to the precipitation of sodium orthoperiodate (Na₂ H₃ IO₆ ) nanoplates and thus the formation of the initial Pickering emulsions. During the gradual formation of cellulose nanofibers and then CNCs, CNCs were attracted to stabilize the interface of the Pickering emulsions, which prevented further decomposition of CNCs by the oxidizing agent in aqueous suspensions. Thus, this isolation strategy secured the efficient separation of CNCs based on their own particular amphiphilic properties and achieved a high yield of up to 56 wt %.

Evaluation of Hydrogels Based on Oxidized Hyaluronic Acid for Bioprinting

In this study, we evaluate hydrogels based on oxidized hyaluronic acid, cross-linked with adipic acid dihydrazide, for their suitability as bioinks for 3D bioprinting. Aldehyde containing hyaluronic acid (AHA) is synthesized and cross-linked via Schiff Base chemistry with bifunctional adipic acid dihydrazide (ADH) to form a mechanically stable hydrogel with good printability. Mechanical and rheological properties of the printed and casted hydrogels are tunable depending on the concentrations of AHA and ADH cross-linkers.

Achieving Controlled Biomolecule-Biomaterial Conjugation

The conjugation of biomolecules can impart materials with the bioactivity necessary to modulate specific cell behaviors. While the biological roles of particular polypeptide, oligonucleotide, and glycan structures have been extensively reviewed, along with the influence of attachment on material structure and function, the key role played by the conjugation strategy in determining activity is often overlooked. In this review, we focus on the chemistry of biomolecule conjugation and provide a comprehensive overview of the key strategies for achieving controlled biomaterial functionalization. No universal method exists to provide optimal attachment, and here we will discuss both the relative advantages and disadvantages of each technique. In doing so, we highlight the importance of carefully considering the impact and suitability of a particular technique during biomaterial design.

SEC Separation of Polysaccharides Using Macroporous Spherical Silica Gel as a Stationary Phase

Abstract

Meso- and macroporous spherical silica gels of pore sizes in the range of 60–1000 Å and 40–75 µm particle size were investigated as a stationary phase for the separation and purification of polysaccharides and poly(ethylene glycols) (PEGs) of various MWs using an aqueous mobile phase. Sephadex and Bio-Gel were used for comparison as the most common stationary phases for similar purposes. The separation of dextrans of a mean MW = 31 kDa from small molecules (NaCl) was possible with SiO₂ with a pore size of 60–300 Å, but the observed efficiencies of a column of the same size were lower comparing with Sephadex or Bio-Gel. In the case of oxidized alginic acid only SiO₂ of the 60 Å pore size was suitable, while Sephadex, Bio-Gel and other investigated silicas were not efficient. Sephadex and 300–1000 Å SiO₂ offered the possibility of dividing dextrans with MW within the range of 1 MDa–10 kDa into fractions of various MWs, while Bio-Gel and 60 Å SiO₂ were not suitable. The investigated silica gels strongly adsorbed PEGs of MW 2–20 kDa. The amount adsorbed decreased with the increase of pore size and they were not useful as a stationary phase for this class of polymers. An advantage of SiO₂ of the investigated particle size was a very low back pressure comparing with Sephadex. A considerably lower price of silica offers time- and cost-efficient separation of polysaccharides.

Graphical Abstract

Transparent, Flexible, and Strong 2,3-Dialdehyde Cellulose Films with High Oxygen Barrier Properties

2,3-Dialdehyde cellulose (DAC) of a high degree of oxidation (92% relative to AGU units) prepared by oxidation of microcrystalline cellulose with sodium periodate (48 °C, 19 h) is soluble in hot water. Solution casting, slow air drying, hot pressing, and reinforcement by cellulose nanocrystals afforded films (∼100 μm thickness) that feature intriguing properties: they have very smooth surfaces (SEM), are highly flexible, and have good light transmittance for both the visible and near-infrared range (89–91%), high tensile strength (81–122 MPa), and modulus of elasticity (3.4–4.0 GPa) depending on hydration state and respective water content. The extraordinarily low oxygen permeation of <0.005 cm³ μm m^–2 day^–1 kPa^–1 (50% RH) and <0.03 cm³ μm m^–2 day^–1 kPa^–1 (80% RH) can be regarded as a particularly interesting feature of DAC films. The unusually high initial contact angle of about 67° revealed a rather low hydrophilicity compared to other oxidatively modified or unmodified cellulosic materials which is most likely the result of inter- and intramolecular hemiacetal and hemialdal formation during drying and pressing.

New perspectives of starch: Synthesis and in vitro assessment of novel thiolated mucoadhesive derivatives

AIM

The purpose of this study was to develop a novel thiolated starch polymer with improved mucoadhesive properties by conjugation of cysteamine to starch as a natural polymer of restricted mucoadhesive properties.

METHODS

Aldehyde substructures were integrated into starch via oxidative cleavage of vicinal diols by increasing amounts of sodium periodate followed by covalent attachment of cysteamine to oxidized starch via reductive amination. Thiol groups were quantified via Ellman's reaction and their impact on mucoadhesion was analyzed by rheological investigations, the rotating cylinder method and tensile studies on porcine mucosa.

RESULTS

The total amount of immobilized thiol groups revealed a correlation between degree of oxidation and thiolation. Modified starch demonstrated an up to 1.66-fold increase in water uptake in comparison to native starch. Modification of starch resulted in greatly improved cohesive properties and improvement in mucoadhesion. Rheological investigations revealed a 2- to 4-fold rise in viscosity of mucus. Tensile studies revealed a linear correlation between degree of oxidation/thiolation and enhancement of maximum detachment force and total work adhesion.

CONCLUSION

In terms of these results, thiolated starch is a new, promising, polymer in the field of mucoadhesive drug delivery systems.

Activation of Periodate by Freezing for the Degradation of Aqueous Organic Pollutants

A new strategy (i.e., freezing) for the activation of IO₄^- for the degradation of aqueous organic pollutants was developed and investigated. Although the degradation of furfuryl alcohol (FFA) by IO₄^- was negligible in water at 25 °C, it proceeded rapidly during freezing at -20 °C. The rapid degradation of FFA during freezing should be ascribed to the freeze concentration effect that provides a favorable site (i.e., liquid brine) for the proton-coupled degradation process by concentrating IO₄^-, FFA, and protons. The maximum absorption wavelength of cresol red (CR) was changed from 434 nm (monoprotonated CR) to 518 nm (diprotonated CR) after freezing, which confirms that the pH of the aqueous IO₄^- solution decreases by freezing. The degradation experiments with varying experimental parameters demonstrate that the degradation rate increases with increasing IO₄^- concentration and decreasing pH and freezing temperature. The application of the IO₄^-/freezing system is not restricted to FFA. The degradation of four other organic pollutants (i.e., tryptophan, phenol, 4-chlorophenol, and bisphenol A) by IO₄^-, which was negligible in water, proceeded during freezing. In addition, freezing significantly enhanced the IO₄^--mediated degradation of cimetidine. The outdoor experiments performed on a cold winter night show that the IO₄^-/freezing system for water treatment can be operated without external electrical energy.

Biodegradable Nanoparticles Enhanced Adhesiveness of Mussel-Like Hydrogels at Tissue Interface

Popular bioadhesives, such as fibrin, cyanoacrylate, and albumin-glutaraldehyde based materials, have been applied for clinical applications in wound healing, drug delivery, and bone and soft tissue engineering; however, their performances are limited by weak adhesion strength and rapid degradation. In this study a mussel-inspired, nanocomposite-based, biodegradable tissue adhesive is developed by blending poly(lactic-co-glycolic acid) (PLGA) or N-hydroxysuccinimide modified PLGA nanoparticles (PLGA-NHS) with mussel-inspired alginate-dopamine polymer (Alg-Dopa). Adhesive strength measurement of the nanocomposites on porcine skin-muscle constructs reveals that the incorporation of nanoparticles in Alg-Dopa significantly enhances the tissue adhesive strength compared to the mussel-inspired adhesive alone. The nanocomposite formed by PLGA-NHS nanoparticles shows higher lap shear strength of 33 ± 3 kPa, compared to that of Alg-Dopa hydrogel alone (14 ± 2 kPa). In addition, these nanocomposites are degradable and cytocompatible in vitro, and elicit in vivo minimal inflammatory responses in a rat model, suggesting clinical potential of these nanocomposites as bioadhesives.

New molecular targets for functionalized nanosized drug delivery systems in personalized therapy for hepatocellular carcinoma

Hepatocellular carcinoma, the most frequent solid tumor of the liver, has a very poor prognosis, being the second most common cause of death from cancer worldwide. The incidence and mortality of this liver tumor are increasing in most areas of the world as a consequence of aging and the emerging of new risk factors such as the metabolic syndrome, beside the recognized role of hepatitis B and C viral infections and alcohol abuse. Despite the increasing knowledge on the molecular mechanisms underlying hepatic carcinogenesis, effective therapeutic strategies are still an unmet clinical need. Efforts have been made to develop selective drugs as well as effective targeted drug delivery systems. The development of novel drug carriers for therapeutic molecules can indeed offer a valuable strategy to ameliorate the efficacy of HCC treatment. In this review, we discuss recent drug delivery strategies for HCC treatment based on the exploitation of targeted nanoparticles (NPs). Indeed, a few of these platforms have achieved an advanced stage of preclinical development. Here, we review the most promising drug nanovehicles based on both synthetic and natural polymers, including polysaccharides that have emerged for their biocompatibility and biodegradability. To maximize site-selectivity and therapeutic efficacy, drug delivery systems should be functionalized with ligands which can specifically recognize and bind targets expressed by HCC, namely cell membrane associated antigens, receptors or biotransporters. Cell surface and intracellular molecular targets are exploited either to selectively deliver drug-loaded nanovehicles or to design novel selective therapeutics. In conclusion, the combination of novel and safe drug delivery strategies based on site-specific targeted drug nanovehicles with therapeutic molecular targets may significantly improve the pharmacological efficacy for the treatment of HCC.

Synthesis and Charaterization of Silica-Based Aldehyde Chitosan Hybrid Material for Biodiesel Purification

This study concerns the development and charaterization of Silica-based aldehyde Chitosan hybrid material as an adsorbent for biodiesel purification. This biocomposite was prepared by sol-gel route and oxidation with periodate, and then characterized. FTIR experiments showed that the hybrid formed presents absorption bands similar to those of Chitosan-Silica, with the exception of the vibrations at 1480 cm⁻¹ and 1570 cm⁻¹ attributed to the symmetrical angular deformation in the N-H plane, and possess large N₂ Brunauer–Emmett–Teller (BET) surface areas. Thermogravimetric analysis (TG) and scanning electron microscopy (SEM) was also carried out. Adsorption studies of bioadsorbents involving the analysis of free glycerol, soap, acidity, diglycerides, triglycerides, and fluorescence spectroscopy showed that silica-based aldehyde chitosan has a good affinity for glycerol and a good purification process.

An unexpected reactivity during periodate oxidation of chitosan and the affinity of its 2, 3-di-aldehyde toward sulfa drugs

In an attempt to determine the reactivity during the periodate oxidation of the vicinal amino sugar, chitosan was oxidized by KIO₄ in a neutral medium. The reactivity was unexpectedly found to be low. The formation of di-aldehyde chitosan (DACT) might cause the low reactivity of chitosan oxidation. Therefore, density functional theory (DFT) calculations were carried out, which revealed that the greater stability of the cyclic amino iodate intermediate might retard the ring opening to form DACT. Furthermore, the affinity of the formation of two novel Schiff bases from the interaction of delivered DACT with two sulfa drugs [sulfanilamide and sulfathiazole] was also investigated using aldehyde content estimation. DACT and Schiff's bases were characterized by FT-IR spectroscopy, X-ray diffraction, and DTA analysis. The X-ray diffraction plane (110) of DACT at the high angle side was expanded more by sulfathiazole than sulfanilamide, indicating that sulfathiazole reacted effectively with DACT. The lowest interaction of DACT with sulfa drugs could be ascribed to the lowest aldehyde content and the intramolecular hemiacetal formation that hinders the Schiff's base condensation.

Preparation of oxidized sodium alginate with different molecular weights and its application for crosslinking collagen fiber

A series of periodate oxidized sodium alginate (OSA) were prepared as green polysaccharide-based crosslinkers. The molecular weight of OSA decreased, while their aldehyde group content increased with increasing dosage of sodium periodate. A typical OSA was further fractionated to four fractions by ethanol with a narrower molecular weight distribution. Then the crosslinking performances of OSAs/fractions on collagen fiber (CF) were investigated. DSC and SEM analyses showed that the thermal stability and dispersion degree of crosslinked CF was considerably enhanced with decreasing molecular weight of OSA. The effect of aldehyde group content of OSA on its crosslinking performance was less obvious than that of molecular weight, probably because the aldehyde group content in each OSA sample was higher than the amino group content of CF involved in the crosslinking reaction. In general, molecular weight of OSA plays a decisive role in improving properties of the crosslinked CF.