Periodate oxidation of nanofibrillated cellulose films for active packaging applications

An alternative packaging material based on cellulose that possesses excellent barrier properties and is potentially useful for active packaging has been developed. Cellulose nanofibril was efficiently and selectively oxidized with sodium periodate generating reactive aldehyde groups. These groups formed hemiacetal and hemialdal bonds during film formation and, consequently, highly transparent, elastic and strong films were created even under moisture saturation conditions. The periodate oxidation treatment additionally decreased the polarity of the films and considerably enhanced their water barrier properties. Thus, the water contact angle of films treated for 3 and 6 h was 97° and 102°, their water drop test value was higher than in untreated film (viz., 138 and 141 min with 3 and 6 h of treatment) and their water vapour transmission rate was substantially better (3.31 and 0.78 g m-2 day-1 with 3 and 6 h, respectively). The presence of aldehyde groups facilitated immobilization of the enzyme laccase, which efficiently captures oxygen and prevents food decay as a result. Laccase-containing films oxidized 80 % of Methylene Blue colorant and retained their enzymatic activity after storage for 1 month and 12 reuse cycles, opening the door to the possible creation of a reusable packaging to replace the single-use packaging.

Direct ink writing of multifunctional nanocellulose and allyl-modified gelatin biomaterial inks for the fabrication of mechanically and functionally graded constructs

Recreating the intricate mechanical and functional gradients found in natural tissues through additive manufacturing poses significant challenges, including the need for precise control over time and space and the availability of versatile biomaterial inks. In this proof-of-concept study, we developed a new biomaterial ink for direct ink writing, allowing the creation of 3D structures with tailorable functional and mechanical gradients. Our ink formulation combined multifunctional cellulose nanofibrils (CNFs), allyl-functionalized gelatin (0.8-2.0 wt%), and polyethylene glycol dithiol (3.0-7.5 wt%). The CNF served as a rheology modifier, whereas a concentration of 1.8 w/v % in the inks was chosen for optimal printability and shape fidelity. In addition, CNFs were functionalized with azido groups, enabling the spatial distribution of functional moieties within a 3D structure. These functional groups were further modified using a spontaneous click chemistry reaction. Through additive manufacturing and a readily available static mixer, we successfully demonstrated the fabrication of mechanical gradients - ranging from 3 to 6 kPa in indentation strength - and functional gradients. Additionally, we introduced dual gradients by combining gradient printing with an anisotropic photocrosslinking step. The developed biomaterial ink opens up possibilities for printing intricate multigradient structures, resembling the complex hierarchical organization seen in living tissues.

Debugging periodate oxidation of cellulose: Why following the common protocol of quenching excess periodate with glycol is a bad idea

Periodate oxidation of cellulose to produce "dialdehyde cellulose" (DAC) has lately received increasing attention in sustainable materials development. Despite the longstanding research interest and numerous reported studies, there is still an enormous variation in the proposed preparation and work-up protocols. This apparently reduces comparability and causes reproducibility problems in DAC research. Two simple but prevalent work-up protocols, namely glycol quenching and filtration/washing, were critically examined and compared, resulting in this cautionary note. Various analytical techniques were applied to quantify residual iodine species and organic contaminations from quenching side reactions. The commonly practiced glycol addition cannot remove all oxidising iodine compounds. Both glycol and the formed formaldehyde are incorporated into DAC's polymeric structure. Quenching of excess periodate with glycol can thus clearly be discouraged. Instead, simple washing protocols are recommended which do not bear the risk of side reactions with organic contaminants. While simple washing was sufficient for mildly oxidised celluloses, higher oxidised samples were more likely to trap residual (per)iodate, as determined by thiosulfate titration. For work-up, simple washing with water is proposed while determining potential iodine contaminations after washing with a simple colorimetric test and, if needed, removal of residual periodate by washing with an aqueous sodium thiosulfate solution.

The effect of periodate oxidation of basil seed gum and its addition on protein binding

This study attempted to determine the best point of basil seed oxidation by applying response surface methodology (RSM) with 3 factors of temperature (35-45 °C), pH (3-7) as well as time (3-7 h), at 3 levels. The produced dialdehyde basil seed gum (DBSG) was collected and its physicochemical properties were determined. Fitting of quadratic, linear polynomial equations was subsequently done by considering the insignificant lack of fit, as well as highly considerable R², in order to probe the probable relationship existing between these considered variables as well as the obtained responses. So the considered optimal related test conditions, which included pH = 3, T = 45 °C as well as Time = 3 h, were specified to produce the highest percentage of aldehyde (DBSG32), optimal (DBSG34) and the (DBSG74) samples with the highest viscosity. The results obtained by FTIR and aldehyde content determination provided the indication that dialdehyde groups were formed in a way that was in equilibrium with the considered the hemiacetal form which was dominant. Furthermore, AFM investigation related to the considered DBSG34 sample displayed over-oxidation as well as depolymerization; this might be due to the enhanced hydrophobic qualities, as well as the decreased viscosity. While the DBSG34 sample had the most dialdehyde factor group with a particular tendency for the combination having the proteins' amino group, DBSG32 and DBSG74 samples could be desirable for industrial uses owing to no overoxidation.

Dicarboxylated hyaluronate: Synthesis of a new, highly functionalized and biocompatible derivative

Sequential periodate-chlorite oxidation of sodium hyaluronate to 2,3-dicarboxylated hyaluronate (DCH), a novel biocompatible and highly functionalized derivative bearing additional pair of COOH groups at C2 and C3 carbons of oxidized ᴅ-glucuronic acid units, is investigated. The impact of various reaction parameters (time, oxidizer concentration, and molar amount) on DCH's composition, molecular weight, degree of oxidation, and cytotoxicity are investigated to guide the synthesis of DCH derivatives of desired properties. Subsequently, fully (99%) and partially (70%) oxidized DCH derivatives were compared to untreated sodium hyaluronate in terms of anticancer drug cisplatin loading efficacy, carrier capacity, drug release rates, and cytotoxicity towards healthy and cancerous cell lines. DCH derivatives were found to be superior in every aspect, having nearly twice the carrier capacity, significantly slower release rates, and higher efficacy. DCH is thus a highly interesting hyaluronate derivative with an adjustable degree of oxidation, molecular weight, and great potential for further modifications.

A comprehensive investigation on modified cellulose nanocrystals and their films properties

In this work, we aimed to tune cellulose nanocrystals (CNCs) properties by introducing different functional groups (aldehyde, carboxyl, silane, and ammonium groups) on the surface through different chemical modifications. These functional groups were obtained by combining: the periodate oxidation with TEMPO-oxidation, aminosylation or cationization. CNCs produced and their films were characterized to elucidate their performances. The results showed that the properties of obtained CNCs varied depending on the grafted functionalities on the surface. The results reveal that after each modification a colloidal stability is preserved. Interestingly, Periodate oxidation of cellulose nanocrystals results in film components that interact through intra- and intermolecular hemiacetals and lead to films with a tensile strength of 116 MPa compared to the pristine CNCs, in contrast the subsequent modifications led to lower tensile strength. Of note, remarkable thermal stability has been achieved after modifications reaching a maximum of 280 °C. The oxygen barrier properties of the films after modifications varied between 0.48 and 0.54 cm³μm/(m²d*kPa) at 50 % RH.

Facile route to tri-carboxyl chitin nanocrystals from di-aldehyde chitin modified by selective periodate oxidation

Chitin, a kind of polysaccharide mainly obtained from food waste, has emerged as an important biodegradable biopolymer in composite materials. The difficulty of aldehyde modification, which greatly limited the application of chitin nanocrystals, was addressed by applying a facile route of partial deacetylation followed by periodate oxidation in this study. Deacetylation occurred on the surface of both crystalline and amorphous regions, which were significantly degraded in the following periodate oxidation due to the inevitable cleavage of chitin chains, leading to an increase in the crystallinity index of obtained di-aldehyde chitin. The degree of deacetylation and periodate addition had limited improvement in the aldehyde content of di-aldehyde chitin with a maximum value of around 0.42 mmol/g. With further 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidation, the carboxyl content of tri-carboxyl chitin was improved to 1.58 mmol/g, which played a critical role in the dispersion efficiency and morphology of chitin nanocrystals. The obtained rod-like chitin nanocrystals with a ζ-potential value of -42 mV and an average size of 97 nm have potential application in dye-adsorption and emulsion stabilizers.

Antibacterial dialdehyde sodium alginate/ε-polylysine microspheres for fruit preservation

Food security is an important global public health issue, which will not only endanger consumers' life and health, but also cause serious food waste. Herein, antibacterial dialdehyde sodium alginate/ε-polylysine microspheres (DSA-PL MPs) were developed to effectively prolong the shelf life of fruit. DSA was prepared by periodate oxidation of sodium alginate. Then the PL was conjugated onto DSA backbone via the Schiff's base reaction to synthesize DSA-PL conjugates, followed by the emulsification and Ca²⁺ ions crosslinking to obtain DSA-PL MPs. The results indicate that DSA-PL MPs show smooth spherical particle, relatively narrow size distribution and good dispersity. In vitro degradation rate of DSA-PL MPs is higher in acetate buffer (pH = 5.0) than that in PBS buffer (pH = 7.4), showing acid-sensitive degradation property. Significantly, DSA-PL MPs possess strong broad-spectrum antibacterial activity, which can effectively extend the shelf life of fruit. Overall, DSA-PL MPs possess promising application as antibacterial agents for fruit preservation.

Gold nanoparticles spontaneously grown on cellulose nanofibrils as a reusable nanozyme for colorimetric detection of cholesterol in human serum

Recently, gold nanoparticles (AuNPs) are extensively used as peroxidase mimics. However, low catalytic activity, high synthesis cost, substrate-induced aggregation in reaction medium and difficulty in recovery and reuse still remain as major challenges. Here, a novel, simple, spontaneous, and reagent-less in-situ method for the production of AuNPs using dialdehyde cellulose nanofibrils (DACNF) is proposed. AuNPs synthesis time and size were greatly influenced by aldehyde content and the optimal aldehyde content for ultra-small AuNPs (≈10 nm) was 2.1 mM/g. AuNPs@DACNFs exhibited broad-spectrum peroxidase activity and steady-state kinetics revealed their better kinetic parameters (low K_m and high V_max) over horseradish peroxidase (HRP). AuNPs@DACNFs was further converted into paper strip, which served as a biosensor for H₂O₂ and cholesterol detection. The proposed method exhibited wide linear response in the range of 10-90 μM and 0.05-0.45 mM, and detection limit of 0.39 μM and 1.9 μM for H₂O₂ and cholesterol, respectively. Great shelf life and reusability were evident by FE-SEM and ICP-OES analysis. The smartphone application "Color Grab" was used to enable the portable onsite detection. The results of cholesterol detection in human serum samples were in agreement with clinically observed values, suggesting the great potential of the probe in disease diagnosis.

A fast method to measure the degree of oxidation of dialdehyde celluloses using multivariate calibration and infrared spectroscopy

The properties of dialdehyde celluloses, which are usually generated by periodate oxidation, are highly dependent on the aldehyde content, i.e. the degree of oxidation (DO). Thus far, the established methods for determining the DO in dialdehyde celluloses lack simplicity or sufficient speed. More than 60 dialdehyde cellulose samples with varying aldehyde content were analysed by near-infrared and Fourier-transform infrared spectroscopy. This was found to be a reliable method for quickly predicting the DO if combined with partial least squares regression (PLSR). The proposed PLSR models can predict the DO with a high determination coefficient (R²) of 99% when applied to a single pulp type and 94% when applied to multiple types. This new approach quickly and reliably determines the DO of dialdehyde celluloses. It can be easily implemented in everyday research to save money, time and resources, especially because the raw datasets and measured DO values are provided.

Surface-mediated periodate activation by nano zero-valent iron for the enhanced abatement of organic contaminants

Periodate (PI)-based advanced oxidation processes have recently received increasing attentions. Herein, PI was readily activated by nano zero-valent iron (nZVI) and subsequently led to the enhanced oxidation of organic contaminants, with the removal performance of sulfadiazine (SDZ) in the nZVI/PI process even higher than that in the nZVI/peroxydisulfate process under identical conditions. Kinetic experiments indicated that the decay of SDZ was susceptible to the dosage of nZVI and PI, but was barely affected by pH values (4.0-7.0) under buffered conditions, suggesting the promising performance of the nZVI/PI process in a relatively wide pH range. Selective degradation of contaminants and ¹⁸O-isotope labeling assays collectively demonstrated that iodate radical (^•IO₃), high-valent iron-oxo species (Fe(IV)) and hydroxyl radical (^•OH) were responsible for the abatement of organic contaminants. More importantly, due to the relatively weak steric hindrance effect of PI, PI easily adsorbed on the surface of nZVI and no iron leaching was detected throughout the reaction, implying that PI activation induced by nZVI was a surface-mediated process. Besides, PI was not transformed into harmful reactive iodine species. This study proposed an environmental-friendly approach for PI activation and shed new lights on the PI-based processes.

Fourier transform and near infrared dataset of dialdehyde celluloses used to determine the degree of oxidation with chemometric analysis

This dataset is related to the research article entitled ``A fast method to measure the degree of oxidation of dialdehyde celluloses using multivariate calibration and infrared spectroscopy''. In this article, 74 dialdehyde cellulose samples with different degrees of oxidation were prepared by periodate oxidation and analysed by Fourier-transform infrared (FTIR) and near-infrared spectroscopy (NIR). The corresponding degrees of oxidation were determined indirectly by periodate consumption using UV spectroscopy at 222 nm and by the quantitative reaction with hydroxylamine hydrochloride followed by potentiometric titration. Partial least squares regression (PLSR) was used to correlate the infrared data with the corresponding degree of oxidation (DO). The developed NIR/PLSR and FTIR/PLSR models can easily be implemented in other laboratories to quickly and reliably predict the degree of oxidation of dialdehyde celluloses.

The combined effect of thermal-acid hydrolysis, periodate oxidation, and iodine species removal on the properties of native tapioca (Manihot esculenta Crantz) starch

Through a four-step top-down approach, native tapioca starch (NTS) was thermally acid-hydrolyzed, periodate-oxidized with subsequent removal of iodine species (i.e., IO₄(-), IO₃(-), I(-), and I₂), and dialdehyde tapioca starch (DTS) alcohol-precipitation. The percent yield was ∼91%. Analyses confirmed the presence of aldehydic functionalities (∼71%), effectual iodine species removal (∼98%), and enhanced water-solubility (∼96.57%). Besides, the combined treatment significantly reduced the M_w (∼57.81 kDa) and ameliorated homogeneity as well as thermal stability (T_max ∼ 667.15 °C). Structural-spectral characterization also confirmed the presence of aldehydic functionality, polymorphic transition (C- to A-type), and a higher degree of crystallinity (∼91.77%), the latter further corroborated by thermal analysis. The morphological study revealed that the combined treatment reduced size (∼393.55-nm-diameter and ∼5.22-μm-length) and changed shape into rod-like crystals. DTS showed considerably and significantly low cytotoxicity to HaCaT cells in vitro at the concentrations assayed over the test period (24 h). DTS's conformation was most stable at -289 kcal/mol and -151.7 au heat formation and minimum potential energies, respectively. Overall, these results demonstrated that the combined treatment had no deleterious effects on NTS's properties, thus yielded DTS with ideal properties for multifarious uses.

Enhancing cisplatin anticancer effectivity and migrastatic potential by modulation of molecular weight of oxidized dextran carrier

The molecular weight (M_w) of dextran derivatives, such as regioselectively oxidized dicarboxydextran (DXA), is greatly influencing their faith in an organism, which could be possibly used to improve anticancer drug delivery. Here we present a modified method of sulfonation-induced chain scission allowing direct and accurate control over the M_w of DXA without increasing its polydispersity. Prepared DXA derivatives (M_w = 10-185 kDa) have been conjugated to cisplatin and the M_w of the carrier found to have a significant impact on cisplatin release rates, in vitro cytotoxicity, and migrastatic potential. Conjugates with the high-M_w DXA showed particularly increased anticancer efficacy. The best conjugate was four times more effective against malignant prostatic cell lines than free cisplatin and significantly inhibited the ovarian cancer cell migration. This was traced to the characteristics of spontaneously formed cisplatin-crosslinked DXA nanogels influenced by M_w of DXA and amount of loaded cisplatin.

Functionalisation of the non-reducing end of chitin by selective periodate oxidation: A new approach to form complex block polysaccharides and water-soluble chitin-based block polymers

Most polysaccharides used in polysaccharide-based block copolymers are attached to the second block through the reducing end, due to the few and highly polysaccharide specific non-reducing end (NRE) functionalisation methods available. Chitin oligomers, prepared by nitrous acid degradation of chitosan (A_nM) can, however, be selectively oxidised by periodate since they only possess a single vicinal diol in the NRE residue. Here, we show that both aldehydes formed after oxidation are highly reactive towards bifunctional oxyamines and hydrazide linkers. Sub-stochiometric amounts of linkers resulted in conjugation of A_nM oligomers through both chain termini to yield a discrete distribution of 'polymerised' oligomers. Such chitin-based block polymers were, in contrast to chitins of the same chain lengths, water-soluble. Oxidised A_nM oligomers, functionalised at both termini can also enable the preparation of more complex block polysaccharides such as ABA- or ABC-type.

Optimizing the properties of Zodo gum and examining its potential for amino acid binding by periodate oxidation

In this study, the Zodo gum exudated by Amygdalus scoparia spach underwent the periodate oxidation process for chemical modification and the formation of dialdehyde groups. Modification of the Zodo gum properties was done using the periodate oxidation method, response surface methodology (RSM) and central composite design (CCD), with 4 factors of sodium periodate volume (6.4-19.2 mL), temperature (35-55 °C), pH (3-5) and time (2-4 h). Dialdehyde Zodo gum (DZG) was produced by controlling test variables and measuring some responses including dialdehyde content and efficacy, in addition to evaluating the rheological parameters. Quadratic, linear polynomial equations were then fitted with the insignificant Lack of fit and high R² to address the relationship between the mentioned variables and responses. Optimal test conditions, including pH = 3.9, T = 43 °C and Time = 3.5 h, were also determined for the production of DZG₁₀, DZG₂₀ and DZG₃₀ samples. The results of ¹H-¹³C NMR, FTIR and determination of the aldehyde content indicated the formation of dialdehyde groups in equilibrium with the dominant hemiacetal form. The AFM study of the DZG₃₀ sample also showed over-oxidation and depolymerization, which could be associated with increased hydrophobic properties and the reduced viscosity. Although the DZG₃₀ sample had the highest amount of the dialdehyde factor group with the tendency to combine with the amino group of proteins, DZG₁₀ and DZG₂₀ samples could be recommended for industrial applications due to the nonoccurrence of overoxidation.

Promising alternative gum: Extraction, characterization, and oxidation of the galactomannan of Cassia fistula

Galactomannan extracted from Cassia fistula seed endosperm present little data related to the its structural characterization. This study reports the chemical characterization of the galactomannan from Cassia fistula (CF) and their oxidized derivatives. The extracted CF presented a yield of 26.5% (w/w) and the intrinsic viscosity [η] was 9.73 dL/g. 1D and 2D nuclear magnetic resonance spectroscopy (NMR) confirmed that the polysaccharide has a backbone of 4-linked β-D-mannose units, and contains galactose units as pending groups. These galactose units are linked to the central core through a (1→6) linkage and the galactomannan presented Man/Gal ratio of 3.1/1. The galactomannan from Cassia fistula presents low cytotoxicity in Vero cells with a CC₅₀ > 1000 μg/ml. The properties of CF resemble other commercially important galactomannans such as Locust bean gum. Three oxidized derivatives of CF were produced by periodate oxidation, which were carefully characterized by different structural techniques. It was observed that as the degree of oxidation increased, there was an increase in the Man/Gal ratio and a reduction in molar mass and viscosity. The polialdehyde produced may be explored as a versality material to react with amine group of the protein and amined polysaccharide to produce biomaterials.

Review: Periodate oxidation of wood polysaccharides-Modulation of hierarchies

Periodate oxidation of polysaccharides has transitioned from structural analysis into a modification method for engineered materials. This review summarizes the research on this topic. Fibers, fibrils, crystals, and molecules originating from forests that have been subjected to periodate oxidation can be crosslinked with other entities via the generated aldehyde functionality, that can also be oxidized or reduced to carboxyl or alcohol functionality or used as a starting point for further modification. Periodate-oxidized materials can be subjected to thermal transitions that differ from the native cellulose. Oxidation of polysaccharides originating from forests often features oxidation of structures rather than liberated molecules. This leads to changes in macro, micro, and supramolecular assemblies and consequently to alterations in physical properties. This review focuses on these aspects of the modulation of structural hierarchies due to periodate oxidation.

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.

Peroxide-periodate co-modification of carboxymethylcellulose to prepare polysaccharide-based tanning agent with high solid content

Dialdehyde carboxymethylcellulose (DCMC) solution generally has quite low solid content, which inevitably limits its industrial application. In this work, carboxymethylcellulose sodium (Na-CMC) was pre-degraded using H₂O₂ followed by periodate oxidation for preparing DCMC with high solid content as practical tanning agent. Pre-degradation conditions optimization showed that H₂O₂ dosage most impacted the tanning effect of DCMC, and the M_w and viscosity of Na-CMC underwent remarkable reduction. FT-IR and ¹H NMR illustrated that aldehyde group was successfully introduced into DCMC after periodate oxidation. Under the optimized conditions, the solid content of DCMC could be improved to around 30%. This DCMC could endow tanned leather with high shrinkage temperature and satisfactory fiber dispersion. Besides, DCMC tanned leather had comparable physical and organoleptic properties to those of leathers tanned by chrome tanning agent and commercial polyaldehyde tanning agent TWT. This suggests the prospect of DCMC with high solid content as useful tanning agent.

Synthesis of compounds having antimicrobial activity from alginate

Compounds having antimicrobial activity were synthesized from sodium alginate, the main constituent of brown algae. Sodium alginate was oxidized with sodium periodate to get alginate dialdehyde (ADA). FTIR spectrum of the ADA gave very small peak characteristic for aldehyde groups at 1720 cm^-1, indicating that the aldehyde group is masked somehow. It may be hydrated, involving at hemiacetal formation or hemialdol, similar to cellulose dialdehyde. Two methods were used for the condensation of ADA with o-phenylenediamine analogs to obtain the final products. The first method was stirring at room temperature and the second method was heating in microwave. The microwave method gave higher yield and shorter reaction time than the other method. The condensation reaction is considered as a shiff-base formation and the proposed mechanism was suggested. The condensation products were characterized by FTIR and UV spectra. The antimicrobial potency for five of these products in addition to the used alginate and to the precursor amines was evaluated against four pathogenic fungi and six pathogenic bacteria species.

Preparation and characterization of dialdehyde β-cyclodextrin with broad-spectrum antibacterial activity

Consumers demand more alternatives of riskless antibacterial agents to prevent microbial contamination in food industry. Oxidized carbohydrate may be a potential option as new antibacterial agent. However, the relatively weak antibacterial property of oxidized carbohydrate is not satisfactory. In this paper, dialdehyde β-cyclodextrins with different oxidation degree were prepared by periodate oxidation and their antibacterial properties were systematically studied. The results showed that multi-aldehyde groups were successfully introduced into β-cyclodextrin molecules by periodate oxidation. The aqueous solubility and stability of dialdehyde β-cyclodextrins were improved as expected. It is interesting that dialdehyde β-cyclodextrins possessed outstanding antibacterial activity against both Gram-positive and Gram-negative bacteria. The minimal inhibitory concentrations against E. coli, S. aureus and B. subtilis reached 0.63, 1.25 and 0.63 mg/mL, respectively. Moreover, dialdehyde β-cyclodextrins effectively inhibited bacterial growth on the surface of apples. The results demonstrated that oxidized oligosaccharide with multi-aldehyde groups and good dispersibility in aqueous solution possessed satisfactory antibacterial activity, which can be used as new antibacterial agent in food industry.

Characterization of therapeutic protein AvidinOX by an integrated analytical approach

AvidinOX, the oxidized derivative of Avidin, is a chemically modified glycoprotein, being currently under clinical investigation for targeted delivery of radioactive biotin to inoperable tumors. AvidinOX is produced by 4-hydroxyazobenzene-2-carboxylic acid (HABA)-assisted sodium periodate oxidation of Avidin. The peculiar property of the periodate-generated glycol-split carbohydrate moieties to form Schiff's bases with amino groups of the tissue proteins allows to achieve a tissue half-life of 2 weeks compared to 2 h of native Avidin. Carbohydrate oxidation, along with possible minor amino acid modifications, introduces additional microheterogeneity in the glycoprotein structure, making its characterization even more demanding than for native glycoproteins. Aiming at the elucidation of the effects of oxidation conditions on the AvidinOX protein backbone and sugars, this microheterogeneous glycoprotein derivative was characterized for the first time using a combination of different analytical methods, including colorimetric methods, mass spectrometry, hollow-fiber flow field-flow fractionation with UV and multi-angle laser scattering detection (HF5-UV-MALS), and NMR. The proposed integrated approach reveals structural features of AvidinOX relevant for its biological activity, e.g., oxidized sites within both carbohydrate moieties and protein backbone and conformational stability, and will be considered as an analytical tool for AvidinOX industrial preparations. It is worth noting that this study enriches also the structural data of native Avidin published up-to-date (e.g., glycan structure and distribution, peptide fingerprint, etc.). Graphical abstract Scheme of phenylacetic hydrazide/MALDI-TOF approach for quantification of aldehydes in AvidinOX based on the determination of the number of hydrazone adducts between hydrazide reagent and aldehyde groups of protein.

Covalent Immobilization of Enzymes on Eupergit® Supports: Effect of the Immobilization Protocol

A selection of best combination of adequate immobilization support and efficient immobilization method is still a key requirement for successful application of immobilized enzymes on an industrial level. Eupergit^® supports exhibit good mechanical and chemical properties and allow establishment of satisfactory hydrodynamic regime in enzyme reactors. This is advantageous for their wide application in enzyme immobilization after finding the most favorable immobilization method. Methods for enzyme immobilization that have been previously reported as efficient considering the obtained activity of immobilized enzyme are presented: direct binding to polymers via their epoxy groups, binding to polymers via a spacer made from ethylene diamine/glutaraldehyde, and coupling the periodate-oxidized sugar moieties of the enzymes to the polymer beads. The modification of the conventionally immobilized enzyme with ethylenediamine via the carbodiimide route seems to be a powerful tool to improve its stability and catalytic activity.

Peculiar behavior of starch 2,3-dialdehyde towards sulfanilamide and sulfathiazole

In this study, starch (1) was oxidized to starch-2,3-dialdehyde (DAS; 2) using potassium periodate. In addition, two novel Schiff's bases (5 &6) were synthesized via a condensation reaction between DAS (2) and sulfa drugs (sulfanilamide; 3 & sulfathiazole; 4). The synthesized Schiff's bases (5 &6) were characterized by FT-IR spectroscopy, X-ray diffraction and DSC analysis. DAS can easily be oxidized owing to its high aldehyde content (91.0%). However, it has low reactivity towards sulfanilamide (3) and sulfathiazole (4). According to the diffraction functional theory, this peculiar behavior is caused by the absence of V-shape in α-glucan linkage in DAS molecules, making the carbonyl group least electropositive. This reduces the nucleophilic attacks of the amino group in sulfa drugs towards the carbonyl group in DAS.

Efficient functionalization of alginate biomaterials

Peptide coupled alginates obtained by chemical functionalization of alginates are commonly used as scaffold materials for cells in regenerative medicine and tissue engineering. We here present an alternative to the commonly used carbodiimide chemistry, using partial periodate oxidation followed by reductive amination. High and precise degrees of substitution were obtained with high reproducibility, and without formation of by-products. A protocol was established using l-Tyrosine methyl ester as a model compound and the non-toxic pic-BH3 as the reducing agent. DOSY was used to indirectly verify covalent binding and the structure of the product was further elucidated using NMR spectroscopy. The coupling efficiency was to some extent dependent on alginate composition, being most efficient on mannuronan. Three different bioactive peptide sequences (GRGDYP, GRGDSP and KHIFSDDSSE) were coupled to 8% periodate oxidized alginate resulting in degrees of substitution between 3.9 and 6.9%. Cell adhesion studies of mouse myoblasts (C2C12) and human dental stem cells (RP89) to gels containing various amounts of GRGDSP coupled alginate demonstrated the bioactivity of the material where RP89 cells needed higher peptide concentrations to adhere.

Conformation of carboxylated schizophyllan in aqueous solution

Carboxylated schizophyllan (sclerox) samples of different degrees of oxidation were molecularly characterized by size exclusion chromatography equipped with a multi-angle light scattering detector (SEC-MALS) in 0.10 M aqueous NaCl solution. The molar mass distribution obtained by SEC-MALS shows that sclerox of low degree of oxidation is dissolved mainly as the trimer, whereas the trimer and single chain coexist in solution of sclerox of high degree of oxidation. The trimer of sclerox is much more flexible than the fully ordered triple helix of the parent schizophyllan and easily dissociates into single chains upon heating.

Physicochemical characterization of novel Schiff bases derived from developed bacterial cellulose 2,3-dialdehyde

The synthesis of two novel Schiff's bases (cellulose-2,3-bis-[(4-methylene-amino)-benzene-sulfonamide] (5) & cellulose-2,3-bis-[(4-methylene-amino)-N-(thiazol-2-yl)-benzenesulfonamide] (6) via condensation reactions of periodate oxidized developed bacterial cellulose ODBC (2) with sulfa drugs [sulfanilamide (3) & sulfathiazole (4)] was reported. The physicochemical characterization of the condensation products was performed using FTIR, (1)H NMR, (13)C NMR spectral analyses, X-ray diffraction and DTA. The ODBC exhibited the highest degree of oxidation based on the aldehyde group number percentage (82.9%), which confirms the highest reactivity of developed bacterial cellulose [DBC (1)]. The X-ray diffractograms indicated an increase in the interplanar distance of the cellulose Schiff base (6) compared to ODBC (2) due to sulfathiazole (4) inclusion between ODBC (2) sheets corresponding to the 1 1 0 plane. In addition, the aldehyde content of Schiff base (6) was (20.8%) much lower than that of Schiff base (5) (41.5%). These results confirmed the high affinity of sulfathiazole (4) to the ODBC (2) chain, and the substantial changes in the original properties of ODBC were due to these chemical modifications rather than the sulfanilamide (3).

Susceptibility of enoxaparin reducing end amino sugars to periodate oxidation

There is a growing interest on glycol-split low-molecular weight heparins (gs-LMWHs), obtained by periodate oxidation of LMWHs, optionally followed by borohydride reduction, as potential anticancer and anti-inflammatory drugs. However, their structural characterization is still a challenging task, mainly because of the high microheterogeneity of the starting material. In addition, susceptibility to oxidation of some end-groups of LMWHs induces additional heterogeneity, making analysis of gs-LMWHs more complex. In our previous study we showed that 1,6-anhydro-d-mannosamine N-sulfate was affected by periodate, while its epimer 1,6-anhydro-d-glucosamine N-sulfate was resistant. In order to understand the apparently anomalous behavior of terminal 1,6-anhydro-d-mannosamine N-sulfate residues, in the present work we have studied by NMR spectroscopy and LC/MS the behavior of the reducing end amino sugar residues of the tetrasaccharides, isolated from the LMWH enoxaparin, in the presence of periodate. Their molecular mechanics conformational characterization has been also performed. We have shown that the C(2)-C(3) bond of the 1,6-anhydro-d-mannosamine residue can be split by periodate despite the N-substitution. Moreover, we have found that both terminal d-mannosamine N-sulfate and d-glucosamine N-sulfate, lacking the 1,6-anhydro-bridge, can be also oxidized by periodate but with a significantly lower rate. The present results suggest that the cis-e-/a-position of OH and NHSO3(-) groups of N-sulfated 1,6-anhydro-d-mannosamine is not the only factor that makes these end residues susceptible to the oxidation. The 1,6-anhydro-bridge that 'blocks' the ring conformation appears another crucial factor for oxidation to occur. Moreover, we have shown that controlling the reaction time could permit to selectively split non-sulfated iduronic acids of enoxaparin chains without oxidizing terminal amino sugar residues, a finding that may be useful to obtain more structurally homogeneous gs-LMHWs.

Porous thin film barrier layers from 2,3-dicarboxylic acid cellulose nanofibrils for membrane structures

To fabricate a strong hydrophilic barrier layer for ultrafiltration (UF) membranes, 2,3-dicarboxylic acid cellulose nanofibrils with high anionic surface charge density (1.2 mekv/g at pH 7) and a width of 22 ± 4 nm were used. A simple vacuum filtration method combined with a solvent exchange procedure resulted in a porous layer with a thickness of ∼ 0.85 μm. The fabricated membranes reached high rejection efficiencies (74-80%) when aqueous dextrans up to 35-45 kDa were filtrated to evaluate the molecular weight cut-offs (MWCO). A linear correlation between the barrier layer thickness and the flux rate was observed in all tested cases. Further optimization of the barrier layer thickness can lead to an even more effective structure.