Thermogravimetric study of starch derivatives with amine/ammonium ion-exchanging groups in oxidative environment

The amine/ammonium materials were prepared by cross-linking of starch (S) with epichlorohydrin (E→SE) in the presence of ammonia (A→SEA) or choline (C→SEC–HO⁻) or with 1,3-bis-(3-chloro-2-hydroxypropyl)imidazolium hydrogensulphate (BCHIHS→SHI–HO⁻) and transfered into the acid/salt forms with HCl (SEA–HCl, SEC–Cl⁻, or SHI–Cl⁻), H₂SO₄ (SEA–H₂SO₄, SEC–HSO₄⁻, or SHI–HSO₄⁻), and H₃PO₄ (SEA–H₃PO₄, SEC–H₂PO₄⁻, or SHI–H₂PO₄⁻) and analyzed with thermogravimetry (TG) under dynamic and isothermal conditions in nitrogen or oxygen environment. According to the values of thermooxidation maxima (TM) calculated from the maximal difference of measured residues on the dynamic TG curves run in nitrogen and oxygen environments the order of decreasing thermooxidation resistance is: S>SEA–H₃PO₄>SHI–H₂PO₄⁻>SHI–HSO₄⁻>SEA–H₂SO₄>SEC–HSO₄⁻>SEC–HO⁻>SEA–HCl>HCl–Cl⁻> SEC–Cl⁻>SHI–HO⁻>SEA>SEC–H₂PO₄⁻>SE. The first-order rate constants calculated by the linear regression method (regression coefficient R>0.95) represented the initial rate constants for residue formation (k_r's) and gasification (k_g's). All the derivatives had greater values of rate constants than S and the k_g's were about 1000 times greater than k_r's. The values obtained in nitrogen were smaller than those calculated from runs in oxygen environment with the exception of S. Most of the salt forms had greater values of k_g's in oxygen environment. The activation energies (E's) were usually greater in nitrogen than in oxygen as well as for residue formation than for gasification. The SHI–HO⁻ sample had high k_g's and low E_g's in oxygen environment while for SHI–H₂SO₄⁻ the opposite was true. This we consider as two extremes for labile and resistant samples for gasification.     

Determination of the DS and substituent distribution of cationic alkyl polyglycosides and cationic starch ethers by GLC after dealkylation with morpholine

The total DS and substituent distribution of starch and alkyl polyglycosides functionalised as O-(2-hydroxy-3-trimethylammonium)propyl ethers were determined by GLC. To achieve volatile analytes, the samples were submitted to methanolysis, N-demethylation and O-trimethylsilylation. Alternatively hydrolysis, reduction with NaBH(4) and subsequent O-acetylation were performed, but suffered from intramolecular acetal formation of 2-O-substituted residues, preventing reduction. Morpholine as nucleophile was superior to thiophenolate with regard to quantitative dealkylation and side product formation. The ratio of un-, mono-, di-, tri-, and tetrasubstituted compounds was determined. The total DS values calculated from these mole fractions were in good agreement with those obtained from elemental analysis or NMR from standards. Regioselectivity of the cationisation reaction was determined after methanolysis, permethylation and Hofmann elimination by GLC.     

Synthesis and characterization of a novel potato starch derivative with cationic acetylcholine groups

A novel substance, cationic acetylcholine potato starch (CAPS), was developed for the first time. The synthesis process had three steps: first, carboxymethyl potato starch (CMPS) was synthesized under sodium hydroxide alkaline condition and in isopropyl alcohol organic media; second, bromocholine chloride (BCC) was synthesized with sulphuric acid as a catalytic agent; finally, CAPS was synthesized by the reaction of CMPS with BCC in N,N'-dimethylformamide (DMF). The degree of substitution (DS) of CAPS was determined by ammonia gas-sensing electrode and elemental analysis. CAPS was characterized by Fourier transformed infrared (FTIR) and near infrared (FTNIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC).     

Recent applications of starch derivatives in nanodrug delivery

Starch has found use in industries as diverse as food, textiles, cosmetics, plastics, adhesives, paper, and pharmaceuticals. From a pharmaceutical standpoint, starch finds its value in solid-oral dosage forms, where it has been used as a binder, diluent, and disintegrant. However, only recently has the use of starch in nanotechnology started to make significant advances in biomedical applications, including newer drug delivery techniques. There has been a considerable effort to develop biodegradable nanoparticles as effective drug delivery systems. Being cheap, non-toxic, renewable, biodegradable and compatible with many other materials for industrial applications, starch is attracting the interest of drug delivery scientists. We have put together in a short and concise format, recent applications of starch derivatives in the emerging field of nanodrug delivery with the conclusion that a lot still needs to be done.     

Synthesis of cationic cardiolipin analogues

An approach was developed to synthesize a new class of cationic cardiolipin analogues containing two quaternary ammonium groups with tetra alkyl groups retaining "glycerol" moiety, the central core of the molecule. Cationic cardiolipin analogues were modified via introduction of either two or four oxyethylene groups to enhance the solubility in polar solvents. These newly synthesized cationic cardiolipin analogues can be applied to a broad range of drug delivery systems such as transfection reagents.     

Structure and characterization of amphoteric semi-IPN hydrogel based on cationic starch

A series of semi-interpenetrating polymer network (semi-IPN) materials were prepared by blending polymerization of acrylic acid (AA) in cationic starch (CS) and poly(methacryloyloxyethyl trimethylammonium chloride) (PDMC) solution. The crosslinker concentration, the feed ratio of the CS-g-AA to PDMC was discussed in term of the swelling capacity, and hydrogel properties were evaluated by network parameters M_c, morphological and compressive load tests. The semi-IPN hydrogels were also characterized by FT-IR spectroscopy to confirm the interactions between CS-g-AA and PDMC. Electron microscopy involved to staining of the anionic phases using CsF showed a transition from two-phase to compatible structure with the increasing content of PDMC, and further confirmed that the semi-IPN structure in hydrogels along with DSC. The resultant semi-IPN hydrogels were found to possess appreciable compatibility, good swellability and mechanical strength.     

Preparation and characterization of cationic corn starch with a high degree of substitution in dioxane-THF-water media

Cationic corn starch derivatives with a high degree of substitution are prepared in alkaline solution or in mixed media of organic solvent and water with different levels of the cationic reagent, 2,3-epoxypropyltrimethylammonium chloride. The starch cationization yield is investigated, and the results indicate that the degree of substitution (DS) of the samples depends on the reaction conditions and reaction media. The maximum DS values are up to 1.37 in 1,4-dioxane alkaline-aqueous solution. Meanwhile, the structures of the cationic starch derivatives are characterized by elemental analyses, FTIR spectroscopy, X-ray diffraction, and ¹³C NMR spectroscopy, as well as by SEM techniques.     

Strength-enhancing effect of cationic starch on mixed recycled and virgin pulps

The present work focuses on the effect of cationic starch (Cat St) on the properties of handsheets made from recycled old corrugated container (OCC) and virgin neutral sulfite semi-chemical (NSSC) pulp. This study also evaluates the usage of OCC fibers as a supplement raw material for papermaking. The handsheet samples contained a series of mixtures of OCC and virgin NSSC pulp (0:100, 20:80, 30:70 and 40:60 by weight) and Cat St (0, 0.5, 1.2, 2 and 3 wt.%). The results showed that addition of Cat St could enhance all the strength properties of handsheets remarkably. At certain Cat St dosage, with increasing OCC fibers, the strength properties were improved significantly, which could be related to the Cat St adsorption efficiency. OCC fibers have more specific surface area than NSSC fibers; therefore, they could adsorb much more amounts of Cat St.     

Photoinactivation of Escherichia coli using porphyrin derivatives with different number of cationic charges

The photodynamic effect of meso-substituted cationic porphyrins, 5-[4-(trimethylammonium)phenyl]-10,15,20-tris(2,4,6-trimethoxyphenyl)porphyrin iodide 1, 5,10-di(4-methylphenyl)-15,20-di(4-trimethylammoniumphenyl)porphyrin iodide 2 and 5-(4-trifluorophenyl)-10,15,20-tris(4-trimethylammoniumphenyl)porphyrin iodide 3, have been investigated in both homogeneous medium bearing photooxidizable substrates and in vitro on a typical gram-negative bacterium Escherichia coli. Absorption and fluorescence spectroscopic studies were compared in N,N-dimethylformamide. Fluorescence quantum yields (varphiF) of 0.10, 0.06 and 0.08 were calculated for porphyrins 1, 2 and 3, respectively. The singlet molecular oxygen, O2(1Deltag), production was evaluated using 9,10-dimethylanthracene yielding values of 0.66, 0.36 and 0.42 for porphyrins 1, 2 and 3, respectively. Guanosine 5'-monophosphate was used as biological substrate model. Similar decomposition of guanosine 5'-monophosphate was obtained using these cationic porphyrins as sensitizer. In biological medium, photosensitized inactivation of E. coli was analyzed using cells without and with one washing step. E. coli cultures were treated with sensitizer at 37 degrees C for 30 min in dark. In both procedures, a higher photoinactivation of cells (>99.999%) was found for cells treated with 10 microM of tricationic porphyrin 3 and irradiated for 5 min with visible light. Porphyrins 1 and 2 only show an important photodamage when the cells are irradiated without washing step. These results indicated that the tetracationic porphyrin 3 could be a promising sensitizer with potential applications in the photoinactivation of bacterial cells by photodynamic therapy.     

Electrospun nano-fiber mats containing cationic cellulose derivatives and poly (vinyl alcohol) with antibacterial activity

Nano-fibrous mats have been successfully prepared by electrospinning of the blend solutions of cationic cellulose derivatives (PQ-4) and polyvinyl alcohol (PVA). Effects of the blending ratio and applied voltage on the morphology and diameter of the electrospun nano-fibers were investigated. The average diameter of the PQ-4/PVA blend fibers was in the range of 150–250 nm. The electrospinning process became instable and the fiber diameter distribution broadened with increasing PQ-4 content and applied voltage. The antibacterial activity of electrospun PQ-4/PVA blend mats against Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus indicated potential for biomedical use.     

Synthesis and delivery activity of new cationic cholesteryl glucosides

Cholesterol amphiphiles containing positively charged groups (pyridinium, N-methylimidazolium, N-methylmorpholinium, and N-methylpiperidinium) linked via β-glucosyl spacer were prepared by alkylation of the corresponding bases with 6-О-mesyl-β-d-cholesteryl glucopyranoside. IC₅₀ values were in the range 20-35 μM for the series of compounds and liposomal formulations with DOPE (1:1) were significantly less toxic. The liposomal formulations provided the accumulation of FITC-labeled oligonucleotide in cells, and the efficiency of this process was comparable to that of Lipofectamine® 2000. Cationic liposomes were able to deliver siRNA into the cells, and the liposomal formulation 7d/DOPE provided the most pronounced down-regulation of EGFP expression both in the presence and in the absence of serum (up to 30%).     

Preparation and adsorption behavior for brilliant blue X-BR of the cost-effective cationic starch intercalated clay composite matrix

In order to increase the adsorption capacity of cationic starch and avoid the loss of cationic groups, novel and cost-effective cationic starch (CS) intercalated clay composite matrix was prepared by controlling the weight ratio of clay and CS. Intercalated microstructure of the composite matrix was characterized by FTIR and XRD, respectively. Reactive dye (brilliant blue X-BR) was used to study adsorption behaviors of the matrix under various parameters such as weight ratio of clay to CS, initial dye concentration, contact time and temperature. Adsorption equilibrium, thermodynamics and kinetics models were further investigated. The results showed that the adsorption capacity increased greatly with increasing the weight ratio of clay to CS from 0.1 to 0.2, and then decreased when the weight ratio up to 0.3. The adsorption isotherm fitted well with the Langmuir isotherm model with a maximum adsorption capacity of 122.0 mg/g. Kinetic study showed that the pseudo-second-order model provided a better correlation of experimental data. Furthermore, the thermodynamic parameters were also calculated.     

Hydrophilic monolayer formation of adsorbed cationic starch and cationic hydroxyethyl cellulose derivatives on polyester surfaces

Cationic starch, cationic cellulose derivatives, and hydrophobically modified cationic cellulose were physically adsorbed from aqueous solution onto oppositely charged hydrophobic polyester (poly(ethylene terephthalate)) fabric and nonwoven, and this resulted in hydrophilic surface properties. Surface coverage of the polysaccharides occurred primarily by strong electrostatic interactions, and the surface characteristics were evaluated by measuring the time required for a water droplet to be absorbed into the polyester material as well as by electron spectroscopy for chemical analysis (ESCA). From a comparison of the adsorption characteristics we assess the polysaccharide-dependent and substrate-dependent adsorption behavior and discuss the similarities and differences in the hydrophilic properties and wettability observed. In particular, the temperature of the cationic polysaccharide solutions in which the substrate was immersed, the configuration of the polymer in solution, and the presence of hydrophobic substituents on the cationic moiety have a considerable effect on the polysaccharide affinity and its adsorption on the surface, irrespective of the substrate type (fabric or nonwoven). We also evaluate the relative contribution of the polyelectrolyte molecular weight, concentration in solution, and degree of charge density along the polymer chain which determine the range of interactions and alter surface hydroplilicity dependent on the type of substrate.     

GMA grafted sago starch as a reactive component in ultra violet radiation curable coatings

Glycidyl methacrylate (GMA) was successfully grafted onto sago starch using ceric ammonium nitrate as initiator in aqueous medium. The percentage of grafting increased with increasing concentration of GMA monomer in the range studied. A core-shell configuration had been suggested to account for the hydrophobic behavior of the starch-g-GMA. Fourier transform infrared spectral analysis provided evidence of the grafting of GMA onto the starch. The acrylic double bond participated in the grafting onto the polysaccharide backbone with the glycidyl groups remaining unaffected.

The graft copolymer of starch and glycidyl methacrylate (starch-g-GMA) was incorporated into UV curable formulations using a cationic photoinitiator. In general, the addition of starch-g-GMA increased the flexibility of the cured film. The increasing of starch-g-GMA concentration in the coatings formulation increased the hardness of cured films. Gel content of the cured epoxy resin remained unimpaired by the addition of starch-g-GMA. Increasing the photoinitiator concentration in the coating formulations increased the hardness and as expected decreased the flexibility of the cured film. The gel content increased with increasing photoinitiator concentration. Further experiments are in progress to study the biodegradability of coatings.     

Synthesis of amphiphilic amylose and starch derivatives

For non-food uses starch generally is modified in order to obtain products with properties suitable for various applications. In the present work, starch and amylose were hydrophobically modified through reactions with long-chain -alkyl epoxides (C₆ and C₁₂) in DMSO solution, in the presence of NaH as a catalyst. The molar substitution (MS) was calculated from NMR spectra. Derivatives with high as well as low MS values were obtained. In order to reach MS values above 1.5, the reaction had to be run for 150–300 h. Viscosity and GPC measurements indicated that the polysaccharides were degraded in DMSO under the influence of methyl sulfinyl anion, which presumably is the active catalyst.

The derivatives were also characterized by FTIR. The ratio between the peak areas for OH stretching and alkyl stretching vibrations, respectively, in the FTIR spectra, was found to be proportional to MS values determined from NMR spectra.

The solubility of the hydrophobically modified polysaccharide in various solvents was tested. Samples having C₁₂-alkyl side chains and MS>1 were soluble in toluene. The C₆ derivatives were water soluble up to a MS value of 0.3.     

Novel imidazole-functionalized cyclen cationic lipids: Synthesis and application as non-viral gene vectors

A series of novel 1,4,7,10-tetraazacyclododecanes (cyclen)-based cationic lipids bearing histidine imidazole group 10a–10e were synthesized. These amphiphilic molecules have different hydrophobic tails (long chain, cholesterol or α-tocopherol) and various type of linking groups (ether, carbamate or ester). These molecules were used as non-viral gene delivery vectors, and their structure–activity relationships were investigated. As expected, the imidazole group could largely improve the buffering capabilities comparing to cyclen. The liposomes formed from 10 and dioleoylphosphatidyl ethanolamine (DOPE) could bind and condense plasmid DNA into nanoparticles with proper size and zeta-potentials. Comparing with Lipofectamine 2000, the formed lipoplexes gave lower transfected cells proportion, but higher fluorescence intensity, indicating their good intracellular delivering ability. Furthermore, results indicate that transfection efficiency of the cationic lipids is influenced by not only the hydrophobic tails but also the linking group. The cyclen-based cationic lipid with α-tocopherol hydrophobic tail and an ester linkage could give the highest transfection efficiency in the presence of serum.     

Biocomposites of thermoplastic starch with surfactant

Thermoplastic starch films were prepared by a casting technique. Microfibrillated fibers from husks of corncobs were added as reinforcing agents and glyceryl monostearate (GMS) as surfactant. The films were characterized using X-ray diffraction studies, thermal and mechanical analysis and water uptake experiments. Differential scanning calorimetry (DSC) and X-ray diffraction showed the formation of amylose–GMS complexes. Compared to films without GMS the films with GMS showed significant reductions in water uptake and an increase in tensile strength. Important differences in the DSC measurements in the 160–200 °C range of films with and without GMS were also exhibited. These effects can be related to the reinforcement of the polymer matrix by the web-like network of the microfibrillated fibers, the formation of amylose–GMS complexes and the interactions of the polar groups of the GMS with the hydroxyl groups of the cellulose. Retrogradation tendencies of the TPS films were also changed by these phenomena.