Fabrication of OSA Starch/Chitosan Polysaccharide-Based High Internal Phase Emulsion via Altering Interfacial Behaviors

This paper attempted to construct a high internal phase emulsion (HIPE) through altering interfacial behaviors using the electrostatic interaction between positive chitosan and negative octenyl succinic anhydride (OSA) starch. The partial polysaccharide complex of OSA starch/chitosan was used to stabilize HIPE, which was able to adsorb at the oil droplet interface and prevent the coalescence of oil droplets. The wettability of OSA starch was enhanced with the addition of positively charged chitosan, leading to the formation of partial complexes. The impact of pH and concentration of chitosan on the droplet size, surface charge, and interface behavior were investigated, and the formation of the polysaccharide complex was further confirmed by atomic force microscopy. The presence of the OSA starch/chitosan complex facilitated the formation of stable HIPE with a gel-like structure and satisfactory centrifugal and oxidative stability. These results are useful to provide information for fabricating polysaccharide-based HIPE delivery systems, which may help expand their application in the food industry.

A molecular logic gate

We propose a scheme for molecule-based information processing by combining well-studied spectroscopic techniques and recent results from chemical dynamics. Specifically it is discussed how optical transitions in single molecules can be used to rapidly perform classical (Boolean) logical operations. In the proposed way, a restricted number of states in a single molecule can act as a logical gate equivalent to at least two switches. It is argued that the four-level scheme can also be used to produce gain, because it allows an inversion, and not only a switching ability. The proposed scheme is quantum mechanical in that it takes advantage of the discrete nature of the energy levels but, we here discuss the temporal evolution, with the use of the populations only. On a longer time range we suggest that the same scheme could be extended to perform quantum logic, and a tentative suggestion, based on an available experiment, is discussed. We believe that the pumping can provide a partial proof of principle, although this and similar experiments were not interpreted thus far in our terms.

Molecular location of a species-specific epitope on the hamster scrapie agent protein

Scrapie is a transmissible neurodegenerative disease of sheep and goats. An abnormal host protein, Sp33-37, is the major protein component of the scrapie agent and the only known disease- or agent-specific macromolecule. Two monoclonal antibodies (MAbs), 4H8 (immunoglobulin G2b [IgG2b]) and 6B11 (IgG1), produced by immunizing mice with the intact hamster 263K scrapie agent protein, Sp33-37Ha, were found to have species specificity similar to that reported previously for MAb 3F4 (IgG2a), which was produced by using PrP-27-30 as the immunogen (R. J. Kascsak, R. Rubenstein, P. A. Merz, M. Tonna-DeMasi, R. Fersko, R. I. Carp, H. M. Wisniewski, and H. Diringer, J. Virol. 61:3688-3693, 1987). These antibodies all bound to Sp33-37 derived from hamster but not from mouse cells. Competitive binding assays demonstrated that all three MAbs bound to the same or overlapping sites on Sp33-37Ha. The molecular location of the epitope for these antibodies was determined to within 10 residues by using an antigen competition enzyme-linked immunosorbent assay in which synthetic peptides spanning Sp33-37Ha residues 79 to 93 or 84 to 93 specifically inhibited binding of these antibodies to plates coated with purified Sp33-37Ha. A synthetic peptide with the mouse-specific sequence (83 to 92) that differed from the hamster sequence by substitution at two positions (MetHa-87----LeuMo-86 and MetHa-90----ValMo-89) did not inhibit antibody binding to Sp33-37Ha. MAb 3F4 binding to hamster Sp33-37 was eliminated by chemical modification of Sp33-37Ha with diethylpyrocarbonate or succinic anhydride and by cleavage with CNBr or trypsin. The effect of diethylpyrocarbonate on MAb 3F4 binding was not reversed by hydroxylamine treatment. MAb 3F4 binding was not affected by prolonged exposure of Sp33-37Ha to 70% formic acid or by boiling in sodium dodecyl sulfate. We conclude that the epitope for these MAbs is a linear determinant that includes Met-87, Lys-88, and Met-90 and that Met-90 is probably the major species-specific determinant.

Starch Modification by Organic Acids and Their Derivatives: A Review

Starch has been an inexhaustible subject of research for many decades. It is an inexpensive, readily-available material with extensive application in the food and processing industry. Researchers are continually trying to improve its properties by different modification procedures and expand its application. What is mostly applied in this view are their chemical modifications, among which organic acids have recently drawn the greatest attention, particularly with respect to the application of starch in the food industry. Namely, organic acids naturally occur in many edible plants and many of them are generally recognized as safe (GRAS), which make them ideal modification agents for starch intended for the food industry. The aim of this review is to give a short literature overview of the progress made in the research of starch esterification, etherification, cross-linking, and dual modification with organic acids and their derivatives.

Quenching and Blinking of Fluorescence of a Single Dye Molecule Bound to Gold Nanoparticles

A fluorescein derivative (SAMSA) bound to gold nanoparticles of different diameters is investigated by time-resolved fluorescence at the single molecule level in a wide dynamic range, from nanosecond to second time scale. The significant decrease of both SAMSA excited state lifetime and fluorescence quantum yield observed upon binding to gold nanoparticles can be essentially traced back to an increase of the nonradiative deactivation rate, probably due to energy transfer, that depends on the nanoparticle size. A slow single molecule fluorescence blinking, in the ms time scale, has a marked dependence on the excitation intensity both under single and under two photon excitation. The blinking dynamics is limited by a low probability nonlinear excitation to a high energy state from which a transition to a dark state occurs. The results point out a strong coupling between the vibro-electronic configuration of the dye and the plasmonic features of the metal nanoparticles that provide dye radiationless deactivation channels on a wide dynamic range.

Homogeneous modification of sugarcane bagasse cellulose with succinic anhydride using a ionic liquid as reaction medium

The homogeneous chemical modification of sugarcane bagasse cellulose with succinic anhydride using 1-allyl-3-methylimidazolium chloride (AmimCl) ionic liquid as a reaction medium was studied. Parameters investigated included the molar ratio of succinic anhydride/anhydroglucose units in cellulose in a range from 2:1 to 14:1, reaction time (from 30 to 160min), and reaction temperature (between 60 and 110 degrees C). The succinylated cellulosic derivatives were prepared with a low degree of substitution (DS) ranging from 0.071 to 0.22. The results showed that the increase of reaction temperature, molar ratio of SA/AGU in cellulose, and reaction time led to an increase in DS of cellulose samples. The products were characterized by FT-IR and solid-state CP/MAS (13)C NMR spectroscopy, and thermal analysis. It was found that the crystallinity of the cellulose was completely disrupted in the ionic liquid system under the conditions given. The data also demonstrated that homogeneous modification of cellulose with succinic anhydride in AmimCl resulted in the production of cellulosic monoester. The thermal stability of the succinylated cellulose decreased upon chemical modification.

Zwitterionic chitosan derivatives for pH-sensitive stealth coating

Zwitterionic chitosan, a chitosan derivative with a unique pH-dependent charge profile, was employed to create a stealth coating on the cationic surface of drug carriers. Zwitterionic chitosans were synthesized by amidation of chitosan with succinic anhydride. The succinic anhydride-conjugated chitosan had an isoelectric point, which could be easily tuned from pH 4.9 to 7.1 and showed opposite charges below and above the isoelectric point. The succinic anhydride-conjugated chitosan was able to inhibit the protein adsorption to the cationic surface at physiological pH, compatible with blood components and well tolerated upon intraperitoneal injection. The succinic anhydride-conjugated chitosan has the potential to serve as a coating material to prevent protein adsorption to cationic surfaces, which can be removed in a pH-responsive manner.

Production of octenyl succinic anhydride-modified waxy corn starch and its characterization

The objective of this work is to investigate the effects of reaction conditions on the synthesis of octenyl succinic anhydride (OSA)-modified starch from waxy corn starch and to study the characteristics of the OSA-modified starch as well as its applications. A mathematical model was developed to investigate the influences of various processing condition factors on the production of the OSA-modified waxy corn starch production and predict the optimum reaction conditions. The maximal degree of substitution (DS) of OSA-modified waxy corn starch (0.0204) was predicted to occur when the starch concentration was 31.2%, the pH was 8.6, the reaction temperature was 33.6 degrees C, and the reaction time was 18.7 h. Repeated reactions for producing OSA-modified waxy corn starch were carried out in a 5 m(3) reactor under the optimized conditions for verification of the model. The characteristics of modified waxy corn starch including infrared spectrum, scanning electron microscopy, and pasting property were tested and emulsification capacity of the OSA-modified starch were evaluated as well.

Improved collagen bilayer dressing for the controlled release of drugs

A novel bilayer dressing has been developed from bovine succinylated collagen. The dressing contains an antibiotic, Ciprofloxacin, for both immediate and time-regulated release for controlling the infection, as the infected open wounds need special care. The dressing consists of a sponge and a film, both prepared from succinylated bovine collagen. The sponge has a smooth surface on one side; its rough surface on the other side forms the bilayer system with the film. Both sponge and film act as an anionic reservoir to hold the cationic Ciprofloxacin. The drug, after dispersing in poly (N-vinyl-2-pyrrolidione) (PVP) solution is allowed to spread in the bilayer system by diffusion. The drug stays in the bilayer system because of ionic binding, but starts releasing when comes in contact with the wound. Release of the drug is immediate, but it is regulated by ionic binding between the drug and succinylated collagen. The wound exudates, and there is a polarity-controlled release of the drug from the bilayer system. The PVP and bilayer system permits only time-regulated release, and the system lasts up to 5 days with therapeutically sufficient drug availability.

Exploration of the Stabilization Mechanism and Curcumin Bioaccessibility of Emulsions Stabilized by Whey Protein Hydrolysates after Succinylation and Glycation in Different Orders

The combined effects of succinic anhydride (SA) succinylation and linear dextrin (LD) glycation on whey protein hydrolysates (WPH) and their stabilized emulsions were evaluated. Degree of succinylation (DS), degree of glycation (DG), and degree of browning of samples suggested that a competitive displacement of reactive groups existed when WPH reacted with SA and LD in different orders. Attenuated total reflection Fourier transform infrared (ATR-FTIR) and far-UV circular dichroism (CD) indicated that the order of modification methods had a significant effect on secondary structures of WPH. Succinylation combined with glycation effectively reduced the surface hydrophobicity and increased the molecular flexibility of WPH. Meanwhile, the total free -SH content decreased, and the exposed free -SH content increased. Results of storage stability and gastrointestinal fate of the curcumin-loaded emulsion revealed that the modified WPH with higher DS was more effective for improving the curcumin bioaccessibility, while that with higher DG was more effective for enhancing the stability of the emulsion.

Controlled synthesis of camptothecin-polylactide conjugates and nanoconjugates

We report here a unique method of formulating camptothecin-polylactide (CPT-PLA) conjugate nanoparticles, termed nanoconjugates (NCs), through CPT/(BDI)ZnN(TMS)(2) [(BDI) = 2-((2,6-diisopropylphenyl)amido)-4-((2,6-bisalkyl)-imino)-2-pentene] mediated polymerization of lactide (LA) followed by nanoprecipitation. When CPT was used as the initiator to polymerize LA in the presence of (BDI)ZnN(TMS)(2), the polymerization was completed within hours with nearly 100% CPT loading efficiency and 100% LA conversion. CPT loading as high as 19.5% can be achieved for the CPT-polylactide (CPT-PLA) conjugate prepared at a LA/CPT ratio of 10. The steric bulk of the chelating ligands and the type of metals used had a dramatic effect on the initiation of the LA polymerization and the tendency of the ring-opening of the CPT lactone. The CPT/(BDI)ZnN(TMS)(2)-mediated LA polymerization yielded CPT-PLA conjugates with well-controlled molecular weights and narrow molecular weight distributions (1.02-1.18). The nanoprecipitation of CPT-PLA led to the formation of NCs around 100 nm in size with narrow particle size distributions. Sustained release of CPT from CPT-PLA NCs was achieved without burst release. CPT-PLA NCs were toxic to PC-3 cells with tunable IC(50) possible by adjusting the drug loading of the CPT-PLA NCs.

Tumor microenvironment-labile polymer-doxorubicin conjugate thermogel combined with docetaxel for in situ synergistic chemotherapy of hepatoma

Topical chemotherapy with complementary drugs is one of the most promising strategies to achieve an effective antitumor activity. Herein, a synergistic strategy for hepatoma therapy by the combination of tumor microenvironment-sensitive polymer-doxorubicin (DOX) conjugate thermogel, containing a DNA intercalator DOX, and docetaxel (DTX), a microtubule-interfering agent, was proposed. First, cis-aconitic anhydride-functionalized DOX (CAD) and succinic anhydride-modified DOX (SAD) were conjugated onto the terminal hydroxyl groups of poly(lactide-co-glycolide)-block-poly(ethylene glycol)-block-poly(lactide-co-glycolide) (PLGA-PEG-PLGA), yielding the acid-sensitive CAD-PLGA-PEG-PLGA-CAD and the insensitive SAD-PLGA-PEG-PLGA-SAD conjugates, respectively. The prodrug aqueous solution exhibited a thermoreversible sol-gel transition between room and physiological temperature. Meantime, appropriate mechanical property, biodegradability, as well as a sustained release profile were revealed in such prodrug thermogels. More importantly, the addition of DTX to the DOX-conjugated thermogels (i.e., Gel-CAD and Gel-SAD) was verified with enhanced curative effect against tumor, where the antitumor efficacy of Gel-CAD+DTX was obviously higher than the other groups. A reliable security in vivo was also showed in the Gel-CAD+DTX group. Taken together, such combination of tumor microenvironment-labile prodrug thermogel and a complementary drug exhibited fascinating prospect for local synergistic antineoplastic therapy.

STATEMENT OF SIGNIFICANCE

Multidrug chemotherapy with synergistic effect has been proposed recently for hepatoma treatment in the clinic. However, the quick release, fast elimination, and unselectivity of multidrugs in vivo always limit their further application. To solve this problem, a synergistic combination of tumor microenvironment-sensitive polymeric doxorubicin (DOX) prodrug thermogel for DNA intercalation and a microtubule-interfering agent docetaxel (DTX) is developed in the present study for the local chemotherapy of hepatoma. Interestingly, a pH-triggered sustained release behavior, an enhanced antitumor efficacy, and a favorable security in vivo are observed in the combined dual-drug delivery platform. Therefore, effectively combining tumor microenvironment-labile polymeric prodrug thermogel with a complementary drug provides an advanced system and a promising prospect for local synergistic hepatoma chemotherapy.

Adsorption studies of methylene blue and gentian violet on sugarcane bagasse modified with EDTA dianhydride (EDTAD) in aqueous solutions: kinetic and equilibrium aspects

In this study the adsorption of cationic dyes by modified sugarcane bagasse with EDTA dianhydride (EB) was examined using methylene blue (MB) and gentian violet (GV) as model compounds in aqueous single solutions. The synthesized adsorbent (EB) was characterized by FTIR, elemental analysis, and BET. The capacity of EB to adsorb dyes was evaluated at different contact times, pH values, and initial dye concentrations. According to the obtained results, the adsorption processes could be described by a pseudo-second-order kinetic model. The adsorption isotherms were well fitted by the Langmuir model. Maximum adsorption capacities for MB and GV on EB were found to be 202.43 and 327.83 mg/g, respectively. The free energy change during adsorption of MB and GV was found to be -22.50 and -24.21 kJ/mol, respectively, suggesting that chemisorption is the main mechanism controlling the adsorption process.

Green route to modification of wood waste, cellulose and hemicellulose using reactive extrusion

A large volume of wood waste is produced in timber processing industry which traditionally used in low value applications. Here, value addition to the wood waste (Sander dust) and cellulose, hemicellulose isolated thereof by functionalisation using cyclic anhydrides in a solvent-free and green reactive extrusion process is reported. The effect of extrusion temperature, catalyst and different weight ratios of Sander dust (SD):succinic anhydride (SA) on the esterification reaction is evaluated. The esterified products were characterised by the acid value, degree of substitution (DS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), solid state (13)C NMR and thermo-gravimetric analysis (TGA). Under optimum extrusion conditions, mixed esters are formed, with highest acid value obtained for succinylation of cellulose (0.122 g/g at DS of 0.350) which is two times higher compared to succinylated SD (0.059 g/g at a weight gain of 0.452) and hemicellulose (0.043 g/g at DS of 0.290). The reactivity trend for individual anhydride was: (1) SA-Cellulose>SD>hemicellulose; (2) maleic anhydride (MA)-SD>hemicellulose>cellulose and (3) dodecenyl succinic anhydride (DDSA)-SD ≈ cellulose ≫ hemicellulose. The pendant free carboxyl groups generated through functionalisation of wood waste, cellulose and hemicellulose without the presence of polymeric carriers will allow more tailored or targeted modification of wood-plastic composites.

Enhanced film-forming properties for ethyl cellulose and starch acetate using n-alkenyl succinic anhydrides as novel plasticizers

PURPOSE

The aim of this study was to investigate the ability of n-alkenyl succinic anhydrides (n-ASAs) to improve the film-forming characteristics of a novel coating polymer, potato starch acetate degree of substitution 2.8 (SA). n-ASAs were also applied to improve the otherwise brittle properties of ethyl cellulose (EC) aqueous dispersion (Aquacoat) and EC solvent-based films.

METHODS

The effectiveness of two n-ASAs, 2-octenyl succinic anhydride (OSA) and 2-dodecen-1-ylsuccinic anhydride were evaluated as plasticizers. Mechanical properties, both water vapor and drug permeabilities, and glass transition temperatures of the cast free films were measured. Triethyl citrate and dibutyl sebacate were used as reference plasticizers.

RESULTS

The long hydrocarbon chain of n-ASA, with its accessible carbonyl groups, enabled a strong plasticization effect on the tested polymers. Due to the excellent mechanical properties (i.e., a tough film structure with considerable flexibility) and low permeability of the plasticized films, n-ASAs, and especially OSA proved to be an ideal plasticizer particularly for EC based coatings. Also, the EC aqueous dispersion plasticized with n-ASAs resulted in a markedly enhanced coalescence of the colloidal polymer particles, even at low drying temperatures.

CONCLUSIONS

In applications where a coating with high flexibility is required, n-ASAs can be used as plasticizers at moderately high concentrations (up to 60-70%, w/w) without losing the high tensile strength, excellent toughness and low permeability of EC and SA films.

An ESR assay for alpha-amylase activity toward succinylated starch, amylose and amylopectin

The esterification of the three polysaccharides, starch, amylose and amylopectin was carried out in pyridine-DMSO by succinic anhydride. The carboxylic groups in the succinylated polysaccharides were measured by FT-IR spectroscopy. The succinic derivatives were tested as alpha-amylase (1,4-alpha-D-glucan glucano hydrolase, E.C. 3.2.1.1) substrates. A colorimetric assay of the alpha-amylase activity indicated that this enzyme is active on succinic esters of starch and amylose and that the activity shows a linear decrease with the number of succinic units introduced into the polysaccharide. Since the colorimetric test was not suitable for the detection of the alpha-amylase activity when succinylated amylopectin was the substrate, we set-up an assay based on the labeling by a paramagnetic probe of the free carboxylic groups of succinylated polysaccharides. The kinetics of the alpha-amylase reaction were monitored by ESR spectroscopy through the increase of the mobility of the paramagnetic probe. The spin label used was the commercially available 4-amino-tempo. By this method we demonstrated that alpha-amylase is active on succinylated amylopectin. The utility of the assay for monitoring alpha-amylase activity when other methods (i.e. colorimetric tests) fail, is discussed.

Adsorption of chromium (VI) ion from aqueous solution by succinylated mercerized cellulose functionalized with quaternary ammonium groups

Succinylated mercerized cellulose (cell 1) was used to synthesize an anion exchange resin. Cell 1, containing carboxylic acid groups was reacted with triethylenetetramine to introduce amine functionality to this material to obtain cell 2. Cell 2 was reacted with methyl-iodide to quaternize the amine groups from this material to obtain cell 3. Cells 2 and 3 were characterized by mass percent gain, degree of amination and quaternization, FTIR and CHN. Cells 2 and 3 showed degrees of amination and quaternization of 2.8 and 0.9 mmol/g and nitrogen content of 6.07% and 2.13%, respectively. Cell 3 was used for Cr (VI) adsorption studies. Adsorption equilibrium time and optimum pH for Cr (VI) adsorption were found to be 300 min and 3.1, respectively. The Langmuir isotherm was used to model adsorption equilibrium data. The adsorption capacity of cell 3 was found to be 0.829 mmol/g. Kinetic studies showed that the rate of adsorption of Cr (VI) on cell 3 obeyed a pseudo-second-order kinetic model.

Synthesis and characterization of novel antimicrobial emulsifiers from epsilon-polylysine

epsilon-Polylysine (EPL) has been used in the food industry as an antimicrobial additive and also a dietary agent. To generate amphiphilic molecules from EPL, hydrophobically modified epsilon-polylysine graft copolymers, which were denoted as OSA-g-EPLs, were synthesized by reacting EPL with octenyl succinic anhydride (OSA). The success of synthesis was confirmed by (1)H NMR and FT-IR spectroscopy. It was found that OSA-g-EPLs had glass transition temperatures lower than EPL. Furthermore, they were able to form polymer micelles in water and to lower the surface tension of water, confirming their amphiphilic properties. The antimicrobial activities of OSA-g-EPLs were also examined, and the minimum inhibitory concentrations of OSA-g-EPLs against Escherichia coli O157:H7 remained the same as that of EPL. Therefore, OSA-g-EPLs have the potential of becoming bifunctional molecules, which can be used either as surfactants or emulsifiers in the encapsulation of nutraceuticals or drugs or as antimicrobial agents.

Study of succinylated food proteins by Raman spectroscopy

Three food protein products, soy protein isolates, spray-dried egg white, and whey protein isolates, were chemically modified to varying levels with succinic anhydride, and the extent of modification of these proteins were determined by standard wet chemistry methods. Raman spectra (500-2000 cm(-1)) of the modified proteins were obtained. New C=O stretching vibrations were observed at 1420 and 1737 cm(-1) and were attributed to the carboxylate (COO-) and ester carbonyl (RCOO-) groups, respectively, which were appended to the proteins during succinylation. Two series of calibration curves were obtained by plotting the intensity ratio of the 1420 and 1737 cm(-1) to 1003 cm(-1) phenylalanine stretching band (used as an internal standard) against the extent of substituted epsilon-amino (and alpha-amino) groups and aliphatic hydroxyl groups, respectively. Linear fits were obtained with correlation coefficient r > 0.988. The Raman spectral data were also analyzed to study the effect of succinylation on the conformation of the three proteins. Some conformational changes were observed, including a transition from ordered to disordered structures, an exposure of tryptophan residues from a buried, hydrophobic microenvironment, and probably conformational shift of cystine residues.

Effect of the degree of substitution of octenyl succinic anhydride-banana starch on emulsion stability

Banana starch was esterified with octenylsuccinic anhydride (OSA) at different degree substitution (DS) and used to stabilize emulsions. Morphology, emulsion stability, emulsification index, rheological properties and particle size distribution of the emulsions were tested. Emulsions dyed with Solvent Red 26 showed affinity for the oil phase. Backscattering light showed three regions in the emulsion where the emulsified region was present. Starch concentration had higher effect in the emulsification index (EI) than the DS used in the study because similar values were found with OSA-banana and native starches. However, OSA-banana presented greater stability of the emulsified region. Rheological tests in emulsions with OSA-banana showed G'>G" values and low dependence of G' with the frequency, indicating a dominant elastic response to shear. When emulsions were prepared under high-pressure conditions, the emulsions with OSA-banana starch with different DS showed a bimodal distribution of particle size. The emulsion with OSA-banana starch and the low DS showed similar mean droplet diameter than its native counterpart. In contrast, the highest DS led to the highest mean droplet diameter. It is concluded that OSA-banana starch with DS can be used to stabilize specific emulsion types.

Comparative Emulsifying Properties of Octenyl Succinic Anhydride (OSA)-Modified Starch: Granular Form vs Dissolved State

The emulsifying ability of OSA-modified and native starch in the granular form, in the dissolved state and a combination of both was compared. This study aims to understand mixed systems of particles and dissolved starch with respect to what species dominates at droplet interfaces and how stability is affected by addition of one of the species to already formed emulsions. It was possible to create emulsions with OSA-modified starch isolated from Quinoa as sole emulsifier. Similar droplet sizes were obtained with emulsions prepared at 7% (w/w) oil content using OSA-modified starch in the granular form or molecularly dissolved but large differences were observed regarding stability. Pickering emulsions kept their droplet size constant after one month while emulsions formulated with OSA-modified starch dissolved exhibited coalescence. All emulsions stabilized combining OSA-modified starch in granular form and in solution showed larger mean droplet sizes with no significant differences with respect to the order of addition. These emulsions were unstable due to coalescence regarding presence of free oil. Similar results were obtained when emulsions were prepared by combining OSA-modified granules with native starch in solution. The degree of surface coverage of starch granules was much lower in presence of starch in solution which indicates that OSA-starch is more surface active in the dissolved state than in granular form, although it led to unstable systems compared to starch granule stabilized Pickering emulsions, which demonstrated to be extremely stable.

Stereocontrol in asymmetric γ-lactam syntheses from imines and cyanosuccinic anhydrides

Computations (SCS-MP2//B3LYP) reveal that the asymmetric synthesis of highly substituted γ-lactams with three stereogenic centers, including one quaternary center, proceeds through a Mannich reaction between the enol form of the anhydride and the E-imine, followed by a transannular acylation. This new mechanistic picture accounts for both the observed reactivity and stereoselectivity. CH-O and hydrogen bonding interactions in the Mannich step and torsional steering effects in the acylation step are responsible for stereocontrol. It is demonstrated that this new mechanistic picture applies to the related reactions of homophthalic anhydrides with imines and presents new vistas for the design of a new reaction to access complex molecular architectures.

Anionically Stabilized Cellulose Nanofibrils through Succinylation Pretreatment in Urea-Lithium Chloride Deep Eutectic Solvent

Deep eutectic solvents (DESs) are green chemicals that have the potential to replace traditional solvents in chemical reactions. In this study, urea-LiCl DES was used successfully as a reaction medium in the anionic functionalization of wood cellulose with succinic anhydride. The effects of reaction temperature and time on the carboxyl content and yield were evaluated. The analyses of the degree of polymerization and crystallinity revealed that the DES was a nondegrading and nondissolving reaction medium. Three samples with the highest carboxyl contents were further nanofibrillated with a microfluidizer to diameters of 2-7 nm, as observed by atomic force microscopy. Samples treated at 70-80 °C for 2 h gave the best outcome and resulted in highly viscose and transparent gels. The sample treated at 90 °C contained larger nanoparticles and larger aggregates owing to the occurrence of possible side reactions but resulted in better thermal stability.

Dodecenylsuccinic anhydride derivatives of gum karaya (Sterculia urens): preparation, characterization, and their antibacterial properties

Esterifications of the tree-based gum, gum karaya (GK), using dodecenylsuccinic anhydride (DDSA) were carried out in aqueous solutions. GK was deacetylated using alkali treatment to obtain deacetylated gum karaya (DGK). The DGK and its DDSA derivative were characterized using gel permeation chromatography/multiangle laser light scattering (GPC/MALLS), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), proton nuclear magnetic resonance spectroscopy ((1)H NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) analysis, and rheological studies. The degree of substitution was found to be 10.25% for DGK using (1)H NMR spectroscopy. The critical aggregation concentration of DDSA-DGK was determined using dye solubilization and surface tension methods. The antibacterial activity of the DDSA-DGK derivative was then investigated against Gram-negative Escherichia coli and Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. The DDSA-DGK derivative has the potential for use as a stabilizing agent in food and nonfood applications. It can also be developed as an antibacterial agent.