Condensed state structure and biocompatibility of the konjac glucomannan/chitosan blend films

Specialised blend films have been prepared by blending 1% w/v konjac glucomannan aqueous with 1% w/v chitosan solution in acetate solution and drying at room temperature for 24 h. The condensed state structure and miscibility of the blend films were studied by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, and wide-angle X-ray diffraction. The results indicated that the blend film obtained from an 80/20 mixing ratio of konjac glucomannan and chitosan derivate showed the highest miscibility and blend homogeneity, and that strong intermolecular hydrogen bonds took place between the amino groups of chitosan and the hydroxyl groups of konjac glucomannan; thus the tensile strength also achieved its maximum in this ratio. The cell morphologies on the pure and blend films were examined by light microscopy and cell viability was studied by using MTT assay. The results showed that the particular blend film was more suitable for the cell culture than the pure konjac glucomannan film, and that the cells cultured on this blend film had greater spreading coefficients than that of the pure konjac glucomannan film. As a result of the good mechanical properties, miscibility and biocompatibility, the blend film is a promising biomaterial matrix.     

Physicochemical and bioactivity of cross-linked chitosan–PVA film for food packaging applications

This work aimed to develop a novel antimicrobial coating based on chitosan and PVA to evaluate its effect on minimally processed tomato by means of microbiological analyses. In this report an antimicrobial film was prepared by blending chitosan (CS) and poly(vinyl alcohol) (PVA) with glutaraldehyde as the cross-linker. The miscibility and morphology of the film were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal property of the chitosan–PVA film was examined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The microbiological screening has demonstrated the antimicrobial activity of the film against food pathogenic bacteria viz. Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. The obtained results indicate the film may be a promising material for food packaging applications.     

Entrapment of 5‐aminolevulinic acid under edible composite film of konjac glucomannan and chitosan

5‐Aminolevulinic acid (5‐ALA) is a known plant regulator and growth promoter. It is a very sensitive and highly unstable compound that is easy to deteriorate. Here we propose a novel approach to stabilize 5‐ALA into a film. Films from konjac glucomannan (KGM), KGM treated with alkali solution (KGOH), chitosan (CHI) as well as blends between KGOH and CHI were fabricated for 5‐ALA entrapment. It was found that the efficiency of KGM film, KGOH film and CHI film for 5‐ALA entrapment was 55.7 ± 0.73%, 58.3 ± 0.36% and 60.3 ± 0.18 %, respectively. A 25:75 (%w/w) blended film (KGOH/CHI) showed the highest entrapment efficiency of 5‐ALA (65.9 ± 0.37%) versus other films. The possible mechanism for entrapment of 5‐ALA in blended film was postulated under two mechanisms. A secondary amide that leads to the interaction between the amino group of CHI and carboxyl group of 5‐ALA is proposed as the first mechanism. The fact that the 5‐ALA molecule was entrapped within the complexity of KGOH structure is proposed as the second mechanism. Therefore, stabilizing 5‐ALA in a film may be an alternative way to use and preserve 5‐ALA for further applications.     

Structural characterization and properties of starch/konjac glucomannan blend films

In this work, a series of glycerol-plasticized pea starch/konjac glucomannan (ST/KGM) blend films was prepared by a casting and solvent evaporation method. The structure, thermal behavior, and mechanical properties of the films were investigated by means of Fourier Transform Infrared Spectroscopy, wide-angle X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, and tensile testing. The results indicated that strong hydrogen bonding formed between macromolecules of starch (ST) and konjac glucomannan (KGM), resulting in a good miscibility between ST and KGM in the blends. Compared with the neat ST, the tensile strength of the blend films were enhanced significantly from 7.4 to 68.1 MPa with an increase of KGM content from 0 to 70 wt%. The value of elongation at break of the blend films was higher than that of ST and reached a maximum value of 59.0% when the KGM content was 70 wt% and 20% of glycerol as plasticizer. The incorporation of KGM into the ST matrix also led to an increase of moisture uptake for the ST-based materials. The structure and properties of pea starch-based films were modified and improved by blending with KGM.     

Preparation and characterization of polyaniline/chitosan blend film

Films consisting of a blend of a chitosan hydrogel and a conductive polymer, polyaniline (PANI), were prepared and characterized for their electrical and mechanical properties. Polyaniline in emeraldine base (EB) form was dispersed in chitosan solution and blend films were obtained by solution casting. The PANI particles in the blend films were then doped with HCl where we observed reductions in the film tensile strength and Young's modulus by about 30%, but the films electrical conductivity increased by 6 orders of magnitude. The highest electrical conductivity of the blend films was of the order 10⁻⁴ S/cm. The electrical and mechanical properties of the films varied with polyaniline content, acid dopant type, acid dopant concentration, and doping time.     

Synthesis of chitosan–polycaprolactone blend for control delivery of ofloxacin drug

In the present research work chitosan has been blended with different amounts of polycaprolactone (PCL) (80:20, 75:25, 60:40 and 50:50) for using them for control delivery of ofloxacin. The blends were characterized by Fourier transmission infra red spectroscopy (FTIR), UV–visible spectroscopy (UV), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis. From the FTIR spectra the various groups present in chitosan and PCL blend were monitored. The homogeneity, morphology and crystallinity of the blends were ascertained from SEM and XRD data, respectively. The swelling studies have been measured at different drug loading. The kinetics of the drug delivery system has been systematically studied. Drug release kinetics was analyzed by plotting the cumulative release data vs. time by fitting to an exponential equation which indicated the non-Fickian type of kinetics. The drug release was investigated at different pH medium and it was found that the drug release depends upon the pH medium as well as the nature of matrix.     

Synergistic effects of nisin and thymol on antimicrobial activities in Listeria monocytogenes and Bacillus subtilis

Nisin Z and thymol were tested, alone and in combination, for antibacterial activity against Listeria monocytogenes ATCC 7644 and Bacillus subtilis ATCC 33712. The antibacterial effect of nisin Z, produced by Lactococcus lactis KE3 isolated from the traditional Moroccan fermented milk, was greatly potentiated by sub-inhibitory concentrations of thymol in both bacterial strains. Our data showed that the concentration of nisin required for effective control of food-borne pathogenic bacteria could be considerably lowered by the use of thymol in combination. The use of low concentrations of nisin could lead to a less favourable condition for the occurrence of nisin-resistant bacterial sub-populations.     

Preparation of konjac glucomannan-based pulsatile capsule for colonic drug delivery system and its evaluation in vitro and in vivo

The current study aims to develop and evaluate a colon-specific, pulsatile drug delivery system based on an impermeable capsule. A pulsatile capsule was prepared by sealing a 5-aminosalicylic acid rapid-disintegrating tablet inside an impermeable capsule body with a konjac glucomannan (KGM)-hydroxypropyl methylcellulose (HPMC)-lactose plug. The drug delivery system showed a typical pulsatile release profile with a lag time followed by a rapid release phase. The lag time was determined by the KGM/HPMC/lactose ratio, the type of HPMC, and the plug weight. The addition of β-glucanase and rat cecal contents into the release medium shortened the lag time significantly, which predicted the probable enzyme sensitivity of the KGM plug. The in vivo studies show that the plasma drug concentration can only be detected 5 h after oral administration of the capsule, which indirectly proves the colon-specific characteristics. These results indicate that the pulsatile capsule may have therapeutic potential for colon-specific drug delivery.     

Preparation and physicochemical properties of a novel hydroxyapatite/chitosan–silk fibroin composite

A novel hydroxyapatite/chitosan–silk fibroin (HA/CTS–SF) composite was prepared for bone repair and replacement by a coprecipitation method. It was revealed that the inorganic phase in the composite was carbonate-substituted HA with low crystallinity. The HA crystallites were found to be needle-like in shape with a typical size of 20–50 nm in length and around 10 nm in width. The composite exhibited a higher compressive strength than the precipitated HA without any organic source involved, which was closely related to the perfect incorporation of chitosan and SF macromolecules into the composite. The chemical interactions occurring between the mineral phase and the organic matrix were thought to improve the interfacial bonding and thus resulted in the enhanced mechanical property of the composite.     

Preparation, characterization and antimicrobial activity of 6-amino-6-deoxychitosan

6-Amino-6-deoxychitosans with molecular weights from 0.23 × 10⁴ to 1.41 × 10⁴ and degree of substitution from 0.85 to 0.96 were prepared via N-phthaloylation, tosylation, azidation, hydrazinolysis and reduction of azide groups. Their structures were characterized by FT-IR, ¹H NMR, ¹³C NMR, gel permeation chromatography (GPC) and elemental analysis. The antimicrobial activities of 6-amino-6-deoxychitosans against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Aspergillus niger were investigated. The results showed that 6-amino-6-deoxychitosans had a wide spectrum of effective antimicrobial activities. Compared with chitosan, 6-amino-6-deoxychitosans had much better antimicrobial activities. Their minimum inhibitory concentrations (MICs) were between 0.025% and 0.1% (w/v) in acetic/sodium acetate solution with different pH from 5.4 to 7.5. 6-Amino-6-deoxychitosans could also inhibit growth of bacteria tested in distilled water under pH 6.6-8.45. The antimicrobial mechanism was complex and the positive charge on the amino groups was not the sole factor resulting in the antimicrobial activities.     

Structure–antimicrobial activity of some natural isocoumarins and their analogues

Three naturally occurring isocoumarins (paepalantine, paepalantine 9-O-beta-D-glucopyranoside and paepalantine 9-O-beta-D-allopyranosyl(1 --> 6) glucopyranoside) and two semi-synthetic analogues, 9,10-acylated compound and 9-OH-10-methylated compound, structurally similar to paepalantine, were evaluated for antimicrobial activity using a spectrophotometric microdilution technique. The paepalantine was active against S. aureus, S. epidermidis, and E. faecalis while the other four compounds proved ineffective against all microorganisms tested at concentrations of 500 microg/ml. Variations in phenolic substitution at OH-9 and/or OH-10 in the paepalantine molecule resulted in compounds without antimicrobial activity. A combination of structural features, two phenolic groups as cathecolic system, forms an oxygenated system arrangement that may reflect the potentially antimicrobial properties of paepalantine.     

Dyeing and antimicrobial characteristics of chitosan treated wool fabrics with henna dye

Chitosan, a naturally available biopolymer which is now increasingly being used as a functional finish on textile substrates to impart antimicrobial characteristics and increase dye uptake of fabrics was applied on wool fabrics. Henna a natural dye with proven bactericidal properties was applied on wool fabrics along with chitosan to impart antimicrobial characteristics. The effect of chitosan application on the dyeing properties of wool fabrics was studied by measuring the K/S values of the treated substrates at various concentrations of chitosan and the dye. The antimicrobial properties of chitosan and natural dyes both when applied independently and collectively on fabrics were assessed. The results proved that the chitosan treated wool fabrics showed increase dye uptake of fabrics. The treated fabrics were found to be antimicrobial and the chitosan treatment enhances the antimicrobial characteristics of the dyes. Fastness properties of the applied finish to washing, rubbing and perspiration have also been discussed.     

Immobilization of Candida cylindracea lipase on poly lactic acid,polyvinyl alcohol and chitosan based ternary blend film: Characterization,activity, stability and its application for N-acylation reactions

The ecofriendly ternary blend polymer film was prepared from the chitosan (CH), polylactic acid (PLA) and polyvinyl alcohol (PVA). Immobilization of Candida cylindracea lipase (CCL) was carried out on ternary blend polymer via entrapment methodology. The ternary blend polymer and immobilized biocatalyst were characterized by using N₂ adsorption–desorption isotherm, SEM, FTIR, DSC, and (%) water content analysis through Karl Fischer technique. Biocatalyst was then subjected for the determination of practical immobilization yield, protein loading and specific activity. Immobilized biocatalyst was further applied for the determination of biocatalytic activity for N-acylation reactions. Various reaction parameters were studied such as effect of immobilization support (ratio of PLA:PVA:CH), molar ratio (dibutylamine:vinyl acetate), solvent, biocatalyst loading, time, temperature, and orbital speed rotation. The developed protocol was then applied for the N-acylation reactions to synthesize several industrially important acetamides with excellent yields. Interestingly, immobilized lipase showed fivefold higher catalytic activity and better thermal stability than the crude extract lipase CCL. Furthermore various kinetic and thermodynamic parameters were studied and the biocatalyst was efficiently recycled for four successive reuses. It is noteworthy to mention that immobilized biocatalyst was stable for period of 300 days.     

Synthesis,antimicrobial evaluation and molecular modeling of 5-hydroxyisoquinolinium salt series; the effect of the hydroxyl moiety

In the present paper, we describe the synthesis of a new group of 5-hydroxyisoquinolinium salts with different lengths of alkyl side-chain (C₁₀–C₁₈), and their chromatographic analysis and biological assay for in vitro activity against bacterial and fungal strains. We compare the lipophilicity and efficacy of hydroxylated isoquinolinium salts with the previously published (non-hydroxylated) isoquinolinium salts from the point of view of antibacterial and antifungal versatility and cytotoxic safety. Compound 11 (C₁₈) had to be excluded from the testing due to its low solubility. Compounds 9 and 10 (C₁₄, C₁₆) showed only moderate efficacy against G+ bacteria, notably with excellent potency against Staphyloccocus aureus, but no effect against G− bacteria. In contrast, non-hydroxylated isoquinolinium salts showed excellent antimicrobial efficacy within the whole series, particularly 14 (C₁₄) against G+ strains and 15 (C₁₆) against fungi. The electronic properties and desolvation energies of 5-hydroxyisoquinolinium and isoquinolinium salts were studied by quantum-chemistry calculations employing B3LYP/6-311++G(d,p) method and an implicit water-solvent simulation model (SCRF). Despite the positive mesomeric effect of the hydroxyl moiety reducing the electron density of the quaternary nitrogen, it is probably the higher lipophilicity and lower desolvation energy of isoquinolinium salts, which is responsible for enhanced antimicrobial versatility and efficacy.     

Preparation of N-vanillyl chitosan and 4-hydroxybenzyl chitosan and their physico-mechanical, optical, barrier, and antimicrobial properties

Chitosan derivatives such as N-vanillyl chitosan and 4-hydroxybenzyl chitosan were prepared by reacting chitosan with 4-hydroxy-3-methoxybenzaldehyde (vanillin) and 4-hydroxybenzaldehyde. Amino groups on chitosan reacts with these aldehydes to form a Schiff base intermediate, which is later on converted into N-alkyl chitosans by reduction with sodium cyanoborohydride. The chemical reaction was monitored by ¹H NMR spectroscopy and the absence of aldehydic proton at 9.83 ppm in NMR spectra was observed for both the modified chitosan derivatives confirming the reaction. Modified chitosan films were later prepared by solution casting method and their physico-mechanical, barrier, optical and thermal properties were studied. The results clearly indicated significant change in tensile strength, water vapour transmission rate, and haze properties of modified chitosans. Modified chitosan films were also studied for their antimicrobial activity against Aspergillus flavus. The results showed a marked reduction of aflatoxins produced by the fungus in the presence of the N-vanillyl chitosan and 4-hydroxybenzyl chitosan film discs to 98.9% and non-detectable levels, respectively.     

Preparation and application of solvent‐modulated self‐doped N–S multicolour fluorescence carbon quantum dots

In this paper, two types of carbon quantum dot (CQDs) were prepared using biocompatible l ‐methionine as the carbon source and urea as the nitrogen source and a one‐step hydrothermal treatment. By changing the reaction solvents (deionized (DI) water and dimethylformamide (DMF)), the maximum emission of the resulting CQDs shifted from blue to red light. Specifically, the emission wavelength of the CQDs moved from 433 nm to 625 nm following embedding of a new functional group (–CONH–) on the surface of the CQDs. Photoluminescence quantum yields of the CQDs with blue and red emission reached 64% and 61%, respectively. The R‐CQDs were used to detect metal ions and a linear relationship was demonstrated between ln(F/F₀) and Fe³⁺ concentration in the range 0–0.5 mmol/L with a detection limit of 0.067 μM. Therefore these R‐CQDs have great potential as fluorescent probes for Fe³⁺ detection. We expect that the excellent water‐soluble, biocompatible and optical properties of the CQDs developed in this work mean that they will be widely used to detect biological cells.     

Comparative BAC‐based physical mapping of Oryza sativa ssp. indica var. 93–11 and evaluation of the two rice reference sequence assemblies

Reference sequences are sequences that are used for public consultation, and therefore must be of high quality. Using the whole‐genome shotgun/next‐generation sequencing approach, many genome sequences of complex higher plants have been generated in recent years, and are generally considered reference sequences. However, none of these sequences has been experimentally evaluated at the whole‐genome sequence assembly level. Rice has a relatively simple plant genome, and the genome sequences for its two sub‐species obtained using different sequencing approaches were published approximately 10 years ago. This provides a unique system for a case study to evaluate the qualities and utilities of published plant genome sequences. We constructed a robust BAC physical map embedding a large number of BAC end sequences forrice variety 93–11. Through BAC end sequence alignments and tri‐assembly comparisons of the 93–11 physical map and the two reference sequences, we found that the Nipponbare reference sequence generated using the clone‐by‐clone approach has a high quality but still contains small artifact inversions and missing sequences. In contrast, the 93–11 reference sequence generated using the whole‐genome shotgun approach contains many large and varied assembly errors, such as inversions, duplications and translocations, as well as missing sequences. The 93–11 physical map provides an invaluable resource for evaluation and improvements toward completion of both Nipponbare and 93–11 reference sequences.     

A simple and rapid method for evaluation of Mark–Houwink–Sakurada constants of linear random coil polysaccharides using molecular weight and intrinsic viscosity determined by high performance size exclusion chromatography: application to guar galactomannan

A rapid method for establishing the constants in the Mark–Houwink–Sakurada equation, relating intrinsic viscosity and molecular weight (MW), of guar galactomannan is described. Following partial acid hydrolysis, the galactomannan was analyzed using high performance size exclusion chromatography employing viscosimetry and right angle light scattering detectors. In this way, a large number of samples of polysaccharides with a wide range of MW distributions were prepared, without need for isolation, and intrinsic viscosity and MW rapidly determined. The a and K values found for guar galactomannan were 0.72 and 5.13×10⁻⁴ ([η] in dl/g) respectively, in good agreement with previously published values.     

Encapsulation of an Agrobacterium radiobacter extract containing d-hydantoinase and d-carbamoylase activities into alginate–chitosan polyelectrolyte complexes: Preparation of the biocatalyst

Alginate–chitosan polyelectrolyte complexes (PECs) have been used for the first time as a suitable matrix for coimmobilisation of enzymes to reproduce a multistep enzymatic route for production of d-amino acids. Encapsulation of a crude cell extract from Agrobacterium radiobacter containing d-hydantoinase and d-carbamoylase activities into the PECs with negligible leakage from the formed capsules was accomplished. All results in this study indicate that the preparation of the biocatalyst (preparation method and chitosan characteristics) play a key role in the biocatalyst's properties. The most suitable biocatalysts were prepared using a chitosan with a medium molecular weight (600 kDa) and a degree of deacetylation of 0.9. For all of the preparation conditions under study, an encapsulation yield of around 60% was achieved and the enzymatic activity yields ranged from 30 to 80% for d-hydantoinase activity and from 40 to 128% for d-carbamoylase activity relative to the activities of the soluble extract. All of the biocatalysts were able to hydrolyze l,d-hydroxyphenylhydantoin into p-hydroxyphenylglycine with yields ranging from 30 to 80%.