Water-soluble Chitosan Derivative Research Articles

Physical, antibacterial, blood coagulation, and healing promotion evaluations of chitosan derivative-based composite films

Chitosan is a potentially suitable material for wound dressing, but is undesirably water-insoluble. Although chitosan can be modified to produce water-soluble derivatives, the best chitosan derivative for wound dressings remains unclear. The present study introduced three water-soluble chitosan derivatives, namely, carboxymethyl chitosan, quaternized chitosan (QCS), and carboxymethyl quaternized chitosan, and explored the physical properties, biochemical properties, and wound care effectiveness of films of these derivatives. The QCS-based film exhibited higher absorption ability, mechanical properties, water-vapor permeability, electroconductivity, and antioxidant capacity than the other films. Most importantly, the cationic quaternary ammonium groups facilitated the antibacterial activity (>95 %) and blood coagulant capacity of the QCS-based film. As this film also promoted wound healing, it presented as an ideal candidate for wound dressings.

Optimization of Interfacial Properties Improved the Stability and Activity of the Catalase Enzyme Immobilized on Plastic Nanobeads.

The immobilization of catalase (CAT), a crucial oxidoreductase enzyme involved in quenching reactive oxygen species, on colloids and nanoparticles presents a promising strategy to improve dispersion and storage stability while maintaining its activity. Here, the immobilization of CAT onto polymeric nanoparticles (positively (AL) or negatively (SL) charged) was implemented directly (AL) or via surface functionalization (SL) with water-soluble chitosan derivatives (glycol chitosan (GC) and methyl glycol chitosan (MGC)). The interfacial properties were optimized to obtain highly stable AL-CAT, SL-GC-CAT, and SL-MGC-CAT dispersions, and confocal microscopy confirmed the presence of CAT in the composites. Assessment of hydrogen peroxide decomposition ability revealed that applying chitosan derivatives in the immobilization process not only enhanced colloidal stability but also augmented the activity and reusability of CAT. In particular, the use of MGC has led to significant advances, indicating its potential for industrial and biomedical applications. Overall, the findings highlight the advantages of using chitosan derivatives in CAT immobilization processes to maintain the stability and activity of the enzyme as well as provide important data for the development of processable enzyme-based nanoparticle systems to combat reactive oxygen species.

Design of a delivery vehicle chitosan-based self-assembling: controlled release, high hydrophobicity, and safe treatment of plant fungal diseases

BackgroundTraditional pesticides are poorly water-soluble and suffer from low bioavailability. N-succinyl chitosan (NSCS) is a water-soluble chitosan derivative, has been recently used to encapsulate hydrophobic drugs to improve their bioavailability. However, it remains challenging to synthesize pesticides of a wide variety of water-soluble drugs and to scale up the production in a continuous manner.ResultsA synthetic method for preparing water-soluble nanopesticides with a polymer carrier was applied. The bioactive molecule BTL-11 was loaded into hollow NSCS to promote drug delivery, improve solubility and anti-fungal activity. The synthesized nanopesticides had well controlled sizes of 606 nm and the encapsulation rate was 80%. The release kinetics, drug toxicity and drug activity were further evaluated. The inhibitory activity of nanopesticides against Rhizoctonia solani (R. solani) was tested in vivo and in vitro. In vivo against R. solani trials revealed that BTL-11 has excellent control efficiency for cultivated rice leaf and sheath was 79.6 and 76.5%, respectively. By contrast, for BTL-11@NSCS NPs, the anti-fungal ability was strongly released and afforded significant control efficiencies of 85.9 and 81.1%. Those effects were significantly better than that of the agricultural fungicide azoxystrobin (51.5 and 66.5%). The proposed mechanism was validated by successfully predicting the synthesis outcomes.ConclusionsThis study demonstrates that NSCS is a promising biocompatible carrier, which can enhance the efficacy of pesticides, synergistically improve plant disease resistance, protect crop growth, and can be used for the delivery of more insoluble pesticides.Graphical

Exclusion liquid chromatography of carboxymethylchitin and carboxymethylchitosan from crustacean <i>Artemia Parthenogenetica</i> of the Aral Sea

The article deals with the synthesis of water-soluble derivatives of chitin and chitosan from cysts of crustaceans of the genus Artemia Parthenogenetica of the Aral Sea by carboxymethylation of OH and NH2 groups of their chains. The elution, viscosity and polyelectrolyte properties in size exclusion liquid chromatography of carboxymethylchitin and carboxymethylchitosan were studied. The suppression of electrostatic effects and the implementation of the exclusion mechanism for the separation of these polysaccharides were achieved by using an aqueous solution of sodium nitrate with a concentration of 0.1 mol/l as an eluent, which was recommended for determining molecular weight characteristics.

Corrosion inhibition of mild steel in 1 M HCl using water soluble chitosan derivative of vanillin

The water-soluble chitosan derivative (WSCD) was made by mixing chitosan with sodium hydroxide, treating the mixture with chloroacetic acid, and then forming a Schiff base with vanillin in an acidic medium. In this study, we examined the corrosion-inhibiting ability of a WSCD on mild steel surfaces in acidic environments. Weight loss, EIS, PDP, LPS, and OCP measurements were used to study the corrosion resistance on mild steel surfaces in 1 M HCl solutions with known concentrations of WSCD. The results show that WSCD functions effectively as a mixed-type anodic and cathodic inhibitor, providing 87 % corrosion inhibition efficiency at 75 ppm. Using SEM to investigate the morphology of corroded mild steel with and without varying amounts of WSCD, impedance measurements show the development of a thin film of inhibitor on the metal surface, the extent of which increases as the inhibitor concentration rises. The WSCD molecule first adsorbs on mild steel and follows Langmuir adsorption isotherm. It is found that the (∆Gads0)adsorption's free energy is −17.473 kJ/mol. The contact angle measurements confirm that the hydrophobicity of the metal surface has increased as a result of the inhibitor's thin film development.

A Water-Soluble Chitosan Derivative for the Release of Bioactive Deferoxamine.

Deferoxamine (DFO) is a water-soluble iron chelator used pharmacologically for the management of patients with transfusional iron overload. However, DFO is not cell-permeable and has a short plasma half-life, which necessitates lengthy parenteral administration with an infusion pump. We previously reported the synthesis of chitosan (CS) nanoparticles for sustained slow release of DFO. In the present study, we developed solid dispersions and nanoparticles of a carboxymethyl water-soluble chitosan derivative (CMCS) for improved DFO encapsulation and release. CS dispersions and nanoparticles with DFO have been prepared by ironical gelation using sodium triphosphate (TPP) and were examined for comparison purposes. The successful presence of DFO in CMCS polymeric dispersions and nanoparticles was confirmed through FTIR measurements. Furthermore, the formation of CMCS nanoparticles led to inclusion of DFO in an amorphous state, while dispersion of DFO in the polymeric matrix led to a decrease in its crystallinity according to X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results. An in vitro release assay indicated sustained release of DFO from CS and CMCS nanoparticles over 48 h and 24 h, respectively. Application of CMCS-DFO dispersions to murine RAW 264.7 macrophages or human HeLa cervical carcinoma cells triggered cellular responses to iron deficiency. These were exemplified in the induction of the mRNA encoding transferrin receptor 1, the major iron uptake protein, and the suppression of ferritin, the iron storage protein. Our data indicate that CMCS-DFO nanoparticles release bioactive DFO that causes effective iron chelation in cultured cells.

6-deoxy-6-amino chitosan: a preventative treatment in the tomato/Botrytis cinerea pathosystem.

6-deoxy-6-amino chitosan (aminochitosan) is a water-soluble chitosan derivative with an additional amine group at the C-6 position. This modification has improved aqueous solubility, in vitro antifungal activity and is hypothesized to have enhanced in vivo antifungal activity compared to native chitosan. Gray mold disease in tomatoes is caused by the fungus, Botrytis cinerea, and poses a severe threat both pre- and post-harvest. To investigate the optimal concentration of aminochitosan and its lower molecular weight fractions for antifungal and priming properties in the tomato/B. cinerea pathosystem, different concentrations of aminochitosan were tested in vitro on B. cinerea growth and sporulation and in vivo as a foliar pre-treatment in tomato leaves. The leaves were monitored for photosynthetic changes using multispectral imaging and hydrogen peroxide accumulation using DAB. Despite batch-to-batch variations in aminochitosan, it displayed significantly greater inhibition of B. cinerea in vitro than native chitosan at a minimum concentration of 1 mg/mL. A concentration-dependent increase in the in vitro antifungal activities was observed for radial growth, sporulation, and germination with maximum in vitro inhibition for all the biopolymer batches and lower MW fractions at 2.5 and 5 mg/mL, respectively. However, the inhibition threshold for aminochitosan was identified as 1 mg/mL for spores germinating in vivo, compared to the 2.5 mg/mL threshold in vitro. The pre-treatment of leaves displayed efficacy in priming direct and systemic resistance to B. cinerea infection at 4, 6 and 30 days post-inoculation by maintaining elevated Fv/Fm activity and chlorophyll content due to a stronger and more rapid elicitation of the defense systems at earlier time points. Moreover, these defense systems appear to be ROS-independent at higher concentrations (1 and 2.5 mg/mL). In addition, aminochitosan accumulates in the cell membrane and therefore acts to increase the membrane permeability of cells after foliar spray. These observations corroborate the notion that aminochitosan biopolymers can exert their effects through both direct mechanisms of action and indirect immunostimulatory mechanisms. The contrast between in vitro and in vivo efficacy highlights the bimodal mechanisms of action of aminochitosan and the advantageous role of primed plant defense systems.

Development and Bioactivity of Zinc Sulfate Cross-Linked Polysaccharide Delivery System of Dexamethasone Phosphate.

Improving the biopharmaceutical properties of glucocorticoids (increasing local bioavailability and reducing systemic toxicity) is an important challenge. The aim of this study was to develop a dexamethasone phosphate (DexP) delivery system based on hyaluronic acid (HA) and a water-soluble cationic chitosan derivative, diethylaminoethyl chitosan (DEAECS). The DexP delivery system was a polyelectrolyte complex (PEC) resulting from interpolymer interactions between the HA polyanion and the DEAECS polycation with simultaneous incorporation of zinc ions as a cross-linking agent into the complex. The developed PECs had a hydrodynamic diameter of 244 nm and a ζ-potential of +24.4 mV; the encapsulation efficiency and DexP content were 75.6% and 45.4 μg/mg, respectively. The designed DexP delivery systems were characterized by both excellent mucoadhesion and prolonged drug release (approximately 70% of DexP was released within 10 h). In vitro experiments showed that encapsulation of DexP in polysaccharide nanocarriers did not reduce its anti-inflammatory activity compared to free DexP.

Effects of oxidation degree on the physicochemical properties of xanthan gum hydrogels containing N,O-carboxymethyl chitosan

ABSTRACT Most xanthan gum-based hydrogels are crosslinked by physical methods, but they typically have inadequate mechanical strength and low thermal, pH, and salt stability. To improve the physicochemical properties of XG-based hydrogels, this study applied periodate oxidation of XG to produce ring-opened products with dialdehyde groups for forming chemically crosslinked hydrogels. The research investigated the effects of oxidized xanthan gum (OXG) at different degrees on the properties of its hydrogels with N,O-carboxymethyl chitosan (NOCC), a water-soluble chitosan derivative. Results show that the rigidity and brittleness of NOCC/OXG hydrogels were enhanced with the increased oxidation of XG. Additionally, the swelling ratio of NOCC/OXG hydrogels was increased by 3.5 times and the degradation rate was reduced by 1.5 times. These hydrogels are promising biomaterials for drug delivery, cell therapy, or tissue regeneration applications.

Effect of deacetylation of chitosan on physicochemical properties, antioxidant and antibacterial activities of chitosan-mannose derivatives.

This paper investigates the physical, chemical, and antibacterial properties of water-soluble chitosan derivatives. Preparation of the water-soluble chitosan derivatives was done by the Maillard reaction (MR) between chitosan (the degree of deacetylation (DD) being 50%, 70%, and 90%) and mannose. No organic reagent was used in the process. Systematic evaluations of the effects of chitosan DD on the reaction extent, the structure, the composition, as well as the physicochemical properties, antioxidant properties, and bacterial inhibitory properties of the finished chitosan-mannose Maillard reaction products (Mc-mrps) were carried out. Based on the experimental data obtained from the Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Pyrolysis-gas chromatography-mass analysis (PY-GC-MS), and 1H-NMR, the Mc-mrps formed from chitosan with different DDs had different structures and components. An increase in the DD of chitosan led to a significant increase in the degree of reaction, color difference (△E), and solubility (p<0.05). The zeta potential and particle size of the Mc-mrps were also influenced by the DD of chitosan. Additionally, the antimicrobial action against Gram-positive (S.aureus and Bacillus subtilis) and Gram-negative bacteria (E.coli and Salmonella typhimurium) as well as antioxidant activity were enhanced by the incorporation of mannose. This was also achieved by the increase of the DD of chitosan. The results of the study suggest that chitosan was derived with mannose to yield a novel, water-soluble polysaccharide with better antioxidant and antimicrobial activities. The DD of chitosan had a significant effect on the properties of the Mc-mrp, which can serve as a reference point for the subsequent preparation and application of such derivatives. This article is protected by copyright. All rights reserved.

Coordinated encapsulation by β-cyclodextrin and chitosan derivatives improves the stability of anthocyanins

To improve the stability of anthocyanins (ACNs), ACNs were loaded into dual-encapsulated nanocomposite particles by self-assembly using β-cyclodextrin (β-CD) and two different water-soluble chitosan derivatives, namely, chitosan hydrochloride (CHC) and carboxymethyl chitosan (CMC). The ACN-loaded β-CD-CHC/CMC nanocomplexes with small diameters (333.86 nm) and had a desirable zeta potential (+45.97 mV). Transmission electron microscopy (TEM) showed that the ACN-loaded β-CD-CHC/CMC nanocomplexes had a spherical structure. Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H NMR) and X-ray diffraction (XRD) confirmed that the ACNs in the dual nanocomplexes were encapsulated in the cavity of the β-CD and that the CHC/CMC covered the outer layer of β-CD through noncovalent hydrogen bonding. The ACNs from the dual-encapsulated nanocomplexes improved stability of ACNs under adverse environmental conditions or in a simulated gastrointestinal environment. Further, the nanocomplexes exhibited good storage stability and thermal stability over a wide pH range when added into simulated electrolyte drinks (pH = 3.5) and milk tea (pH = 6.8). This study provides a new option for the preparation of stable ACNs nanocomplexes and expands the applications for ACNs in functional foods.

DEAE/Catechol-Chitosan Conjugates as Bioactive Polymers: Synthesis, Characterization, and Potential Applications.

This work provides the first description of the synthesis and characterization of water-soluble chitosan (Cs) derivatives based on the conjugation of both diethylaminoethyl (DEAE) and catechol groups onto the Cs backbone (Cs-DC) in order to obtain a Cs derivative with antioxidant and antimicrobial properties. The degree of substitution [DS (%)] was 35.46% for DEAE and 2.53% for catechol, determined by spectroscopy. Changes in the molecular packing due to the incorporation of both pendant groups were described by X-ray diffraction and thermogravimetric analysis. For Cs, the crystallinity index was 59.46% and the maximum decomposition rate appeared at 309.3 °C, while for Cs-DC, the values corresponded to 16.98% and 236.4 °C, respectively. The incorporation of DEAE and catechol groups also increases the solubility of the polymer at pH > 7 without harming the antimicrobial activity displayed by the unmodified polymer. The catecholic derivatives increase the radical scavenging activity in terms of the half-maximum effective concentration (EC50). An EC50 of 1.20 μg/mL was found for neat hydrocaffeic acid (HCA) solution, while for chitosan-catechol (Cs-Ca) and Cs-DC solutions, concentrations equivalent to free HCA of 0.33 and 0.41 μg/mL were required, respectively. Cell culture results show that all Cs derivatives have low cytotoxicity, and Cs-DC showed the ability to reduce the activity of reactive oxygen species by 40% at concentrations as low as 4 μg/mL. Polymeric nanoparticles of Cs derivatives with a hydrodynamic diameter (Dh) of around 200 nm, unimodal size distributions, and a negative ζ-potential were obtained by ionotropic gelation and coated with hyaluronic acid in aqueous suspension, providing the multifunctional nanoparticles with higher stability and a narrower size distribution.

Phosphorylated chitosan accelerates dermal wound healing in diabetic wistar rats

Phosphorylated chitosan (PC), a water-soluble derivative of chitosan possesses several biological and chemical properties suitable for diabetic wound healing. In the present study, we report the synthesis and diabetic wound healing capabilities of PC. Elemental analysis, FT-IR, 13C-NMR and 31P-NMR techniques were employed for the chemical characterization of PC. In vitro, antioxidant properties of PC were determined in terms of Fe3+ reducing, metal chelating, lipid peroxidation and superoxide scavenging ability. The wound healing potential of PC was assessed in diabetic excisional wound rat model. PC exhibited good water solubility, and in vitro antioxidant capacity. Wound contraction was higher in PC-treated wounds (91.11%) as compared to untreated wounds (67.26%) on 14th-day post wound creation. Histopathology of PC-treated wounds revealed improved tissue morphology with higher number of fibroblasts, a thicker epithelial layer, enhanced collagen deposits and angiogenesis as compared to untreated wounds. An overall increase of 57% and 25% in hydroxylamine and hexosamine content respectively were noted as compared to untreated wounds. A significant (P ≤ 0.05) increase in SOD activity and a significant (P ≤ 0.05) decrease in lipid peroxides were recorded in PC-treated wounds as compared to untreated wounds. These observations demonstrated that PC can be used as an effective agent in diabetic wound healing.Graphical Illustration of phosphorylated chitosan (PC) synthesis and its wound healing potential: Chitosan was phosphorylated to impart diabetic wound healing properties. Chemical characterizations such as elemental analysis, FT-IR and NMR confirmed successful phosphorylation of chitosan. PC exhibited good in vitro antioxidant properties. To assess the diabetic wound healing potential, an excisional wound model was developed in diabetic rats. PC treatment demonstrated accelerated wound healing.

Smart pH responsive system based on hybrid mesoporous silica nanoparticles for delivery of fungicide to control Fusarium crown and root rot in tomato

Mesoporous silica nanoparticles (MSNs) can promote the solubility and absorption of pesticides by plants and are widely used as a delivery system to improve the efficacy of pesticide applications. In this study, MSNs with 20 nm particle size were produced. Additionally, a water-soluble chitosan (CS) derivative, here called N-(2-Hydroxyl) propyl-3- tri-methyl-ammonium CS chloride (HTCC) was produced and used to cap the outer surface of the MSNs preloaded with the pesticide fludioxonil (Flu). The HTCC coating layers resulted in a pesticide loading efficiency of 84% on the MSNs in comparison to a loading efficiency of 20% of uncoated particles. A comparative in vitro analysis indicated that Flu@MSNs20nm-HTCC loaded with a 0.05 mg/L dose of fungicide had significant higher fungicidal activity than the same fungicide at 1 mg/L dose against F. oxysporum f. sp. radicis-lycopersici (FORL). Moreover, after an initial burst, MSNs20nm-HTCC kept releasing Flu for 21 d, compared to an activity of 7 d associated with the direct release of Flu. Greenhouse data showed that 0.1 mg/L Flu applied through MSNs20nm-HTCC is sufficient to reduce Fusarium crown and root rot disease severity to a value of less than 6% in tomato plants, without any noticeable phytotoxicity after 70 d. In comparison, 1.56 mL/L of the fungicide are required to reach a 27% disease severity level. Thus, we suggest that HTCC-decorated MSNs20nm has a great potential as a nanodelivery systems for agrochemical applications. We also suggest that this work contributes to the notion that agro-nanotechnology is a powerful, environmentally-safe and cost-effective approach for a sustainable and long term protection of plants from disease.

Synthesis of Hydroxypropyltrimethyl Ammonium Chitosan Derivatives Bearing Thioctate and the Potential for Antioxidant Application

Hydroxypropyltrimethyl ammonium chloride chitosan (HACC) is one of the most important water-soluble chitosan derivatives; its derivatives have gained growing attention due to their potential biomedical applications. Here, hydroxypropyltrimethyl ammonium chitosan derivatives bearing thioctate (HACTs), with different degrees of substitution of thioctate, were prepared using HACC and α-lipoic acid as the reaction precursors, using an ion exchange method. The structural characteristics of the synthesized derivatives were confirmed by FTIR, 1H NMR, and 13C NMR spectroscopy. In addition, their antioxidant behaviors were also investigated in vitro by the assays of reducing power, and scavenging activities against hydroxyl radicals and DPPH radicals. The antioxidant assay indicated that HACTs displayed strong antioxidant activity compared with HACC, especially in terms of reducing power. Besides, the antioxidant activities of the prepared products were further enhanced with the increase in the test concentration and the degrees of substitution of thioctate. At the maximum test concentration of 1.60 mg/mL, the absorbance value at 700 nm of HACTs, under the test conditions, was 4.346 ± 0.296, while the absorbance value of HACC was 0.041 ± 0.007. The aforementioned results support the use of HACTs as antioxidant biomaterials in food and the biomedical field.

Acyl-Modified Water-Soluble Chitosan Derivatives as Carriers for Adsorption Immobilization of Papain

Acyl-Modified Water-Soluble Chitosan Derivatives as Carriers for Adsorption Immobilization of Papain

The Water-Soluble Chitosan Derivative, N-Methylene Phosphonic Chitosan, Is an Effective Fungicide against the Phytopathogen Fusarium eumartii.

Chitosan has been considered an environmental-friendly polymer. However, its use in agriculture has not been extended yet due to its relatively low solubility in water. N-Methylene phosphonic chitosan (NMPC) is a water-soluble derivative prepared by adding a phosphonic group to chitosan. This study demonstrates that NMPC has a fungicidal effect on the phytopathogenic fungus Fusarium solani f. sp. eumartii (F. eumartii) judged by the inhibition of F. eumartti mycelial growth and spore germination. NMPC affected fungal membrane permeability, reactive oxygen species production, and cell death. Also, this chitosan-derivative exerted antifungal effects against two other phytopathogens, Botrytis cinerea, and Phytophthora infestans. NMPC did not affect tomato cell viability at the same doses applied to these phytopathogens to exert fungicide action. In addition to water solubility, the selective biological cytotoxicity of NMPC adds value in its application as an antimicrobial agent in agriculture.

Water-soluble chitosan-based indicator label membrane and its response behavior to carbon dioxide

In this work, two kinds of water-soluble chitosan derivatives (succinylated chitosan and hydroxypropyl chitosan) were used as substrates to prepare indicator label for detecting CO 2 concentration. The mixed-dyes of bromocresol blue and methyl red indicators were investigated and the results of SEM test revealed that the mixed indicator could be uniformly dispersed in the transparent membranes. The color differences of the indicator label under different environmental conditions (humidity and temperature) were highly correlated with the CO 2 concentration. The values of label membranes' color difference ( δ E ) showed a good linear relationship with the CO 2 content. Subsequently, these label membranes were successfully applied to reveal the evolution of the CO 2 content in fruit packaging to indicate the freshness of fruit. Therefore, these chitosan derivative-based indicator label membranes assume a promising application prospect in the future. • Chitosan derivative-based indicator label for detecting CO 2 concentration was fabricated. • The color difference ( δ E ) of label showed a good linear relationship with the CO 2 content. • The response to CO 2 level can be achieved under different conditions of humidity and temperature. • The freshness of fruits and vegetables can be revealed by the color change of this indicator label.

Exploring phosphonium and ammonium chitosan polymers and their PEGylated analogs for high performance gene delivery

• New chitosan derivatives containing triethylammonium chloride or triethylphosphonium chloride and their PEGylated analogs have been synthesized and characterized. • The derivatives efficiently bind pDNA at low weight ratio of derivative:pDNA of 2.8:1. • Apoptosis measurements by flow cytometry indicated that the derivatives containing triethylammonium chloride or triethylphosphonium chloride and PEG induce no perceptible and mild apoptosis with their concentration at 100 µg/mL. • The present study provides evidence that these PEGylated derivatives are safe and effective vectors for efficient nucleic acid delivery. Among cationic polymers, chitosan (CS) is a promising non-viral vector due to its biocompatibility, biodegradability and safety profile. However, its application for gene delivery is hindered by its poor solubility at physiological pH. In this study, novel water-soluble chitosan derivatives containing triethylphosphonium chloride ((N-(1-carboxybutyl-4-triethylphosphonium chloride) chitosan = TEPB-CS)) or triethylammonium chloride ((N-(1-carboxybutyl-4-triethylammonium chloride) chitosan = TEAB-CS)) with 4-carbon spacers separating the cationic units from the chitosan backbone were synthesized by carbodiimide mediated coupling reactions. Two different degrees of substitution of quaternary phosphonium (43% and 21%) and ammonium (40.6% and 26%) were synthesized. The polymers with higher degrees of substitutions displayed higher solubility in aqueous media and were further grafted with mPEG (TEAB-CS-g-mPEG and TEPB-CS-g-mPEG) and used for DNA complexation, cytotoxicity, apoptosis, and gene transfection studies. Chemical characterization of the above polymers was performed by FTIR, 1 H NMR, and 31 P NMR, and the degree of substitution of the grafted phosphonium and ammonium and mPEG was calculated by 1 H NMR. The polymers efficiently bound pDNA at weight ratio of polymer:pDNA of 2.8:1. From dynamic light scattering experiments, the mean diameters of the calf thymus DNA complexes with the polymers, in water and phosphate buffer (pH 7.4), were in the range of 140 – 330 nm. Zeta potential of these complexes in water became positive as the weight ratios of the polymers/DNA exceeded 2:1. Most of these polymers mildly affect the viability of HeLa cells with a final concentration of 10 µg/mL or higher. Cell viability was only modestly compromised in the presence of 100 µg/mL of TEPB-CS-g-mPEG, and this derivative was also found to display the highest transfection efficiencies among all four polymers. Apoptosis measurements by flow cytometry indicated that both TEAB-CS-g-mPEG and TEPB-CS-g-mPEG induce no perceptible and mild apoptosis with their concentration at 100 µg/mL, respectively. Together, the present study provides evidence that these PEGylated TEPB-CS and TEAB-CS are safe and effective vectors for efficient nucleic acid delivery.

Quaternary Trimethyl Chitosan Chloride Capped Bismuth Nanoparticles with Positive Surface Charges: Catalytic and Antibacterial Activities

Quaternary trimethyl chitosan-stabilized bismuth nanoparticles (QTMC-BiNPs) with positive surface charges were uniquely synthesized and fully characterized. In the synthesis, Quaternary Trimethyl Chitosan (QTMC), a water-soluble derivative of chitosan (CTS) was prepared using two-step reductive methylation. The new biopolymeric functionalized ligand was further used as capping agent for the synthesis of QTMC-BiNPs which was applied as antibacterial and catalytic agents. The reaction was carried out at room temperature without the use of energy consuming or high-cost instruments. The QTMC and nanocomposites were characterized by proton nuclear magnetic resonance (1H NMR), attenuated total reflection Fourier-transform infrared, UV–visible, X-ray diffraction, X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopic techniques. The topology and morphology of the composites were examined with scanning electron microscopy and high-resolution transmission electron microscopy. Thermogravimetric and differential thermal gravimetric analysis were also conducted. The degree of quaternization and degree of dimethylation values of 63.33 and 11.75%, respectively obtained for QTMC confirmed that the main product is a quaternary derivative. The average particle size of QTMC-BiNPs was evaluated to be between 30 and 45 nm. The QTMC-BiNPs revealed clear and uniform lattice fringes with an estimated interplanar d-spacing of 0.32 nm confirming the formation of highly crystalline nanocomposites. A further insight into the antibacterial activities of this nanomaterial were carefully examined on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) using resazurin based microdilution method for Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC). The obtained results revealed that both bacteria pathogens were effectively inhibited/killed by the QTMC-BiNPs at very low concentrations. The MIC of 15.63 and 125 µg/mL were recorded against E. coli and S. aureus, respectively while the MBC of 31.25 and 500.00 µg/mL were estimated against E. coli and S. aureus, respectively. An extensive evaluation of the catalytic capability of the nanocomposites towards the reduction of 4-nitrophenol to 4-aminophenol was also carried out with highly promising result.