A simple and convenient method to synthesize N-[(2-hydroxyl)-propyl-3-trimethylammonium] chitosan chloride in an ionic liquid

Carboxymethyl cellulose-chitosan edible films for food packaging: A review of recent advances

Polysaccharide-based edible films have been widely developed as food packaging materials in response to the rising environmental concerns caused by the extensive use of plastic packaging. In recent years, the integration of carboxymethyl cellulose (CMC) and chitosan (CS) for a binary edible film has received considerable interest because this binary edible film can retain the advantages of both constituents (e.g., the great oxygen barrier ability of CMC and moderate antimicrobial activity of CS) while mitigating their respective disadvantages (e.g., the low water resistance of CMC and poor mechanical strength of CS). This review aims to present the latest advancements in CMC-CS edible films. The preparation methods and properties of CMC-CS edible films are comprehensively introduced. Potential additives and technologies utilized to enhance the properties are discussed. The applications of CMC-CS edible films on food products are summarized. Literature shows that the current preparation methods for CMC-CS edible film are solvent-casting (main) and thermo-mechanical methods. The CMC-CS binary films have superior properties compared to films made from a single constituent. Moreover, some properties, such as physical strength, antibacterial ability, and antioxidant activity, can be greatly enhanced via the incorporation of some bioactive substances (e.g. essential oils and nanomaterials). To date, several applications of CMC-CS edible films in vegetables, fruits, dry foods, dairy products, and meats have been studied. Overall, CMC-CS edible films are highly promising as food packaging materials.

Preparation of N-(2-hydroxypropyltrimonium chloride)-O-dodecylylpyridine chitosan quaternary ammonium salt and its antibacterial activities

Chitosan derivatives, including O-carboxymethyl chitosan (CMC), N-(2-hydroxypropyltrimonium chloride)-O-carboxymethyl chitosan (QCMC), and N-(2-hydroxypropyltrimonium chloride)-O-dodecylylpyridine chitosan quaternary ammonium salt (DQCMC), were synthesized and characterized using Fourier transform infrared (FTIR) spectroscopy, 1H nuclear magnetic resonance (1H NMR) spectroscopy, Ultraviolet-visible (UV-vis) spectroscopy, and element analysis (EA). The antibacterial activities of chitosan and chitosan derivatives against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were evaluated through the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and antibacterial rate assays. Results demonstrated that DQCMC exhibited significantly higher antibacterial efficacy compared to chitosan, CMC, and QCMC. The MIC of DQCMC against E. coli and S. aureus were 31 μg/mL and 7 μg/mL, respectively, with a 100 % antibacterial rate at a concentration of 0.5 mg/mL. Furthermore, assessment of mouse fibroblast (L929) cell viability using cell counting kit-8 (CCK-8) methods revealed no toxicity associated with the material.

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.

Synthesis, Optimization and Molecular Self-Assembly Behavior of Alginate-g-Oleylamine Derivatives Based on Ugi Reaction for Hydrophobic Drug Delivery

To achieve the optimal alginate-based oral formulation for delivery of hydrophobic drugs, on the basis of previous research, we further optimized the synthesis process parameters of alginate-g-oleylamine derivatives (Ugi-FOlT) and explored the effects of different degrees of substitution (DSs) on the molecular self-assembly properties of Ugi-FOlT, as well as the in vitro cytotoxicity and drug release behavior of Ugi-FOlT. The resultant Ugi-FOlT exhibited good amphiphilic properties with the critical micelle concentration (CMC) ranging from 0.043 mg/mL to 0.091 mg/mL, which decreased with the increase in the DS of Ugi-FOlT. Furthermore, Ugi-FOlT was able to self-assemble into spherical micellar aggregates in aqueous solution, whose sizes and zeta potentials with various DSs measured by dynamic light scattering (DLS) were in the range of 653 ± 25~710 ± 40 nm and -58.2 ± 1.92~-48.9 ± 2.86 mV, respectively. In addition, RAW 264.7 macrophages were used for MTT assay to evaluate the in vitro cytotoxicity of Ugi-FOlT in the range of 100~500 μg/mL, and the results indicated good cytocompatibility for Ugi-FOlT. Ugi-FOlT micellar aggregates with favorable stability also showed a certain sustained and pH-responsive release behavior for the hydrophobic drug ibuprofen (IBU). Meanwhile, it is feasible to control the drug release rate by regulating the DS of Ugi-FOlT. The influence of different DSs on the properties of Ugi-FOlT is helpful to fully understand the relationship between the micromolecular structure of Ugi-FOlT and its macroscopic properties.

Polyelectrolyte complex formation of alginate and chito oligosaccharide is influenced by their proportion and alginate molecular weight

Sodium alginate (SA) and chito oligosaccharide (COS) are widely used food additives in the food industry, and exploring their interaction to form polyelectrolyte complexes (PECs) may provide insights into food development. In the present study, the effects of viscosity-average molecular weight (Mv) and relative amounts of SA on the formation of sodium alginate/chito oligosaccharide polyelectrolyte (SCP) complexes were investigated. The results showed that the electrostatic interaction between -COOH and -NH2 and the hydrogen bonding between OH, were attributed to the formation of the SCP complexes. Then the formation and properties of SCP complexes were greatly dependent on the Mv and the relative amount of SA. SA with Mv of ≥2.16 × 106 Da could form spherical SCP complexes, while the SA/COS ratio (w/w) ≥ 0.8 was not conducive to the formation of SCP complexes. Moreover, the SCP complexes were more stable in the gastric environment than in the intestinal condition. In addition, 1.73 × 107 Da was the optimal Mv of SA for SCP complexes formation. This study contributed to a comprehensive understanding of the interaction between SA and COS, and shed light on the potential application of SA and COS formulation to develop new food products.

Investigation of Filtration and Shale Inhibition Characteristics of Chitosan-N-(2-hydroxyl)-propyl trimethylammonium Chloride as Drilling Fluid Additives

Hydrated shale formations often lead to severe drilling problems and may lead to wellbore instability. These instabilities can result in issues such as bit balling, borehole collapse, formation damage, stuck pipe, and low drilling rates. Keeping these fundamental issues with drilling in shale formation in mind, this study is aimed at designing a water-based drilling fluid system for effective shale inhibition, ensuring enhanced wellbore stability and drilling efficiency. The designed mud system comprises a typical base fluid along with newly synthesized chitosan derivative chitosan-N-(2-hydroxyl)-propyl trimethylammonium chloride (HACC) as an additive. This additive was found to be soluble in water and conducive for shale inhibition. The derived product was characterized by field emission scanning electron microscopy, thermogravimetric analysis, and Fourier-transform infrared spectroscopy (FTIR). Various drilling fluid tests, including filtration and rheological experiments, were conducted to evaluate its proficiency as a drilling mud additive. The results showed improvement in rheological and filtration properties after hot rolling at 100 °C in comparison to a conventional shale inhibitor, polyethylenimine. As we increase the concentration of synthesized chitosan derivative from 0.3 to 1.5 w/v%, the filtration loss is reduced from 40% to 65% as compared to the base fluids. Shale recovery tests were also conducted using shale samples from an Indian field to assess its viability for field application. The addition of 0.3 to 1.5 w/v% chitosan derivative resulted in high shale recovery above 88% to 96% at 100 °C compared to polyethylenimine, which showed a change in recovery from 62% to 73%. HACC intercalates into clay platelets, reducing the interlayer spacing between particles and preventing clay from hydrating and swelling. This mechanism of inhibition is evaluated by X-ray diffraction, FTIR, and zeta potential analysis. This bolsters the hypothesis of using the synthesized chitosan derivative as a shale inhibitor.

Reactive oxygen species-responsive hydrophobic crosslinked chitosan films based on triple-function crosslinkers

Chitosan is widely used in reactive oxygen species (ROS)-responsive films but remains great challenges owing to its weak mechanical strength and strong hydrophilicity. Herein, we synthesized novel hydrophobic crosslinked CS films with ROS-responsive properties and excellent physicochemical properties. A novel crosslinker, 2-((10-carboxydecyl)thio)succinic acid, with long-chain alkanes, three carboxyl groups, and sulfhydryl groups was synthesized and then used to produce thioether-containing crosslinked CS membranes. The results suggested that crosslinking could significantly increase the tensile strength of the film from 15.67 MPa to 24.32 MPa. The compact structure of crosslinked chitosan film improved the hydrophobicity and degradability, reduced the thermal stability and swelling rates, exhibited excellent non- cytotoxicity. The in vitro release studies revealed that crosslinked chitosan films could displayed the highest flux about 1.40 mg/ (cm2 h) and significant NR fluorescence change over 80 %. Collectively, our results demonstrate the applicability of these films as ROS-responsive drug delivery systems.

Marine-origin polysaccharides-based free-standing multilayered membranes as sustainable nanoreservoirs for controlled drug delivery

The layer-by-layer (LbL) assembly technology has been widely used to functionalise surfaces and precisely engineer robust multilayered bioarchitectures with tunable structures, compositions, properties, and functions at the nanoscale by resorting to a myriad of building blocks exhibiting complementary interactions. Among them, marine-origin polysaccharides are a sustainable renewable resource for the fabrication of nanostructured biomaterials for biomedical applications owing to their wide bioavailability, biocompatibility, biodegradability, non-cytotoxicity, and non-immunogenic properties. Chitosan (CHT) and alginate (ALG) have been widely employed as LbL ingredients to shape a wide repertoire of size- and shape-tunable electrostatic-driven multilayered assemblies by exploring their opposite charge nature. However, the insolubility of CHT in physiological conditions intrinsically limits the range of bioapplications of the as-developed CHT-based LbL structures. Herein, we report the preparation of free-standing (FS) multilayered membranes made of water-soluble quaternised CHT and ALG biopolymers for controlled release of model drug molecules. The influence of the film structure in the drug release rate is studied by assembling two distinct set-ups of FS membranes, having the model hydrophilic drug fluorescein isothiocyanate-labelled bovine serum albumin (FITC-BSA) either as an intrinsic building block or added as an outer layer after the LbL assembly process. Both FS membranes are characterised for their thickness, morphology, in vitro cytocompatibility, and release profile, with those having FITC-BSA as an intrinsic LbL ingredient denoting a more sustained release rate. This work opens up new avenues for the design and development of a wide array of CHT-based devices for biomedical applications, overcoming the limitations associated with the insolubility of native CHT under physiological conditions.

Modification of glass-ionomer cement properties by quaternized chitosan-coated nanoparticles

Glass ionomers (GICs), because of their qualities, are in a good position to be modified to resist masticatory stresses as permanent posterior restoration and prevent recurrent caries. The purpose of the present study was to evaluate the effect of adding quaternized chitosan-coated mesoporous silica nanoparticles (HTCC@MSNs) to conventional GIC on its mechanical properties, antimicrobial activity and fluoride release and the effect of 1- and 3-month water aging on the studied properties. HTCC@MSNs was synthesized, added to commercially available conventional GIC at 1%, 3%, and 5% by weight forming three experimental groups and compared with plain GIC as a control group. Flexural strength, modulus, Vickers microhardness and wear volumes were evaluated. Antibacterial activity was tested against Streptococcus mutans and fluoride release in de-ionized water was measured. All properties were evaluated before and after one- and three-month aging (n = 10 specimens per test/per time). Two-way ANOVA was used for statistical analysis. Characterization confirmed successful preparation of HTCC@MSNs. The flexural strength, modulus, hardness and wear resistance of the GICs improved significantly by adding 1-3% HTCC@MSNs, while 5% HTCC@MSNs group showed no significant difference compared to control group. Bacterial inhibition zones and fluoride release increased proportionally to the amount of filler added. Mechanical properties were improved by artificial aging. Fluoride release values, and bacterial inhibition zones decreased with aging for all groups. HTCC@MSNs as a filler with the optimized proportion provides strengthening and antibacterial effect. In addition, aging is an important factor to be considered in evaluating experimental fillers.

Development of Quaternized Chitosan Integrated with Nanofibrous Polyacrylonitrile Mat as an Anion-Exchange Membrane

A two-phase anion-exchange membrane was prepared from quaternized chitosan (QCS) integrated with an electrospun polyacrylonitrile (PAN) scaffold by spin coating. To synthesize QCS, glycidyltrimethylammonium chloride in various amounts was introduced into the structure of CS. The characterization of the cast cross-linked QCS (CQCS) membranes by impedance spectroscopy revealed the ionic conductivity (IC) in the range of 2.8 × 10^-4 to 8.2 × 10^-4 S cm^-1 and the degree of quaternization (DQ) of 26.4-51.0%, where the CQCS film with the DQ of 51.0% showed excellent performance. When CQCS was reinforced with a PAN fiber mat, the newly developed composite membrane demonstrated the highest IC of 34 × 10^-4 S cm^-1 at 80 °C, low swelling, and an almost eightfold increase in tensile strength at a fully hydrated state compared to pristine materials. Moreover, the CQCS/PAN membrane was chemically stable and revealed increasing hydroxide transport during 1 month immersion in alkaline media.

Studies on Intermolecular Interaction of N-Glycidyltrimethyl Ammonium Chloride Modified Chitosan/N,N-Dimethyl-N-dodecyl-N-(2,3-epoxy propyl) Ammonium Chloride and Curcumin Delivery

Chitosan has potential applications in many fields, due to its biocompatibility, biodegradability and reproducibility. However, the insolubility in water restricts its wide application. In order to expand the application of chitosan in the delivery of oil-soluble drugs and improve the efficacy of oil-soluble drugs, N-Glycidyltrimethyl ammonium chloride-modified chitosan (GTA-m-CS) and N,N-Dimethyl-N-dodecyl-N-(1,2-epoxy propyl) ammonium chloride (DDEAC), a kind of reactive surfactant, were synthesized and characterized by FTIR, NMR and XRD methods. The interactions between GTA-m-CS and DDEAC was studied by surface tension, viscosity, conductivity and fluorescence methods. The parameters, including equilibrium surface tension, critical micelle concentrations of DDEAC with different GTA-m-CS concentration, critical aggregation concentration of DDEAC, the amount of DDEAC adsorbed on GTA-m-CS, pc₂₀ and π_cmc were obtained from the surface tension curves. The influence of temperature on the above parameters were evaluated. The degree of counterion binding to micelle and the thermodynamic parameters of the system were calculated from the conductivity curves. According to the change of conductivity with temperature, the thermodynamic parameters of micellar formation were calculated. The aggregation number of DDEAC molecules in GTA-m-CS/DDEAC aggregates were calculated from steady-state fluorescence data. Based on the experimental results, the interaction models between GTA-m-CS and DDEAC were proposed. The GTA-m-CS/DDEAC aggregates could be used as curcumin carries, and achieved sustained release.

Chitosan-Based Biomaterial Scaffolds for the Repair of Infected Bone Defects

The treatment of infected bone defects includes infection control and repair of the bone defect. The development of biomaterials with anti-infection and osteogenic ability provides a promising strategy for the repair of infected bone defects. Owing to its antibacterial properties, chitosan (an emerging natural polymer) has been widely studied in bone tissue engineering. Moreover, it has been shown that chitosan promotes the adhesion and proliferation of osteoblast-related cells, and can serve as an ideal carrier for bone-promoting substances. In this review, the specific molecular mechanisms underlying the antibacterial effects of chitosan and its ability to promote bone repair are discussed. Furthermore, the properties of several kinds of functionalized chitosan are analyzed and compared with those of pure chitosan. The latest research on the combination of chitosan with different types of functionalized materials and biomolecules for the treatment of infected bone defects is also summarized. Finally, the current shortcomings of chitosan-based biomaterials for the treatment of infected bone defects and future research directions are discussed. This review provides a theoretical basis and advanced design strategies for the use of chitosan-based biomaterials in the treatment of infected bone defects.

Synthesis of Chitosan Derivatives and Their Inhibition Effects on Methane Hydrates

In recent years, the study of natural polymer products such as methane hydrate inhibitors has attracted more and more attention in the scientific research field. In order to achieve environmentally friendly and economical methane hydrate inhibitors with high activity, four chitosan derivatives were successfully synthesized and their methane hydrate inhibition effects were compared with chitosan (CS) and carboxymethyl chitosan (CMCS). Under the conditions of 6 MPa, 1 °C and 400 rpm, the induction time of methane hydrate was prolonged by 7.3 times with the addition of 0.1 wt% CS. It was found that chitosan with high hydrophobicity could effectively prevent methane gas from entering the water solution and reduce the driving force of methane hydrates, resulting in the extension of hydrate induction time. The hydrate inhibition effect of CMCS could be improved by the introduction of hydroxypropyl-3-trimethylamine and N-2-hydroxypropyl-3-isooctyl ether groups based on the enhancement of the molecular hydrophobicity. At the same time, the introduction of the trimethyl quaternary ammonium group increased the ion content in the aqueous solution, which further inhibited the nucleation and growth of methane hydrates. This work is supposed to serve as an inspiration for the further research and development of green kinetic hydrate inhibitors with high-efficiency.

N-(2-hydroxyl)-propyl-3-trimethylammonium chitosan chloride/carboxymethyl cellulose films filled with in-situ crystallized calcium carbonate

The research and development of substitutes for petroleum-based plastics has become a hot topic. The N-(2-hydroxyl)-propyl-3-trimethylammonium chitosan chloride (HTCC, 10 wt%)/sodium carboxymethyl cellulose (CMC) films have showed enhanced mechanical properties, which also provide a potential substitute to petroleum-based plastics. In this paper, calcium carbonate was crystallized (cry-CaCO3) in HTCC/CMC film-forming solutions, and the effects of the cry-CaCO3 particles on HTCC/CMC film properties including microstructures, mechanical properties, thermal stability, whiteness, and wettability were characterized. An HTCC/CMC film with commercially available CaCO3 (com-CaCO3) was used as a control. The results showed that the cry-CaCO3 promoted the homogeneous distribution of the HTCC/CMC matrix and significantly improved mechanical properties, but showed little effect on the thermal stability, whiteness and wettability of the films. To reveal the affecting mechanism of cry-CaCO3 on HTCC/CMC film properties, the cry-CaCO3 particles were isolated from film-forming solutions and characterized by scanning electron microscope (SEM), powder X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetric analysis (TGA) methods. The results showed that the HTCC/CMC matrix modulated spherical CaCO3 particles, and the macromolecules were encapsulated in cry-CaCO3 particles, decreasing their adhesion to the HTCC/CMC matrix while increasing their distribution in the HTCC/CMC matrix. The strong electrostatic, hydrogen bonding and flexible interaction between CMC and cry-CaCO3 particles played a key role in improving the mechanical properties of HTCC/CMC films.

One-Pot Synthesis of Amphiphilic Biopolymers from Oxidized Alginate and Self-Assembly as a Carrier for Sustained Release of Hydrophobic Drugs

In this paper, we developed an organic solvent-free, eco-friendly, simple and efficient one-pot approach for the preparation of amphiphilic conjugates (Ugi-OSAOcT) by grafting octylamine (OCA) to oxidized sodium alginate (OSA). The optimum reaction parameters that were obtained based on the degree of substitution (DS) of Ugi-OSAOcT were a reaction time of 12 h, a reaction temperature of 25 °C and a molar ratio of 1:2.4:3:3.3 (OSA:OCA:HAc:TOSMIC), respectively. The chemical structure and composition were characterized by Fourier transform infrared spectroscopy (FTIR), ¹H nuclear magnetic resonance (¹H NMR), X-ray diffraction (XRD), thermogravimetry analyser (TGA), gel permeation chromatography (GPC) and elemental analysis (EA). It was found that the Ugi-OSAOcT conjugates with a CMC value in the range of 0.30–0.085 mg/mL could self-assemble into stable and spherical micelles with a particle size of 135.7 ± 2.4–196.5 ± 3.8 nm and negative surface potentials of −32.8 ± 0.4–−38.2 ± 0.8 mV. Furthermore, ibuprofen (IBU), which served as a model poorly water-soluble drug, was successfully incorporated into the Ugi-OSAOcT micelles by dialysis method. The drug loading capacity (%DL) and encapsulation efficiency (%EE) of the IBU-loaded Ugi-OSAOcT micelles (IBU/Ugi-OSAOcT = 3:10) reached as much as 10.9 ± 0.4–14.6 ± 0.3% and 40.8 ± 1.6–57.2 ± 1.3%, respectively. The in vitro release study demonstrated that the IBU-loaded micelles had a sustained and pH-responsive drug release behavior. In addition, the DS of the hydrophobic segment on an OSA backbone was demonstrated to have an important effect on IBU loading and drug release behavior. Finally, the in vitro cytotoxicity assay demonstrated that the Ugi-OSAOcT conjugates exhibited no significant cytotoxicity against RAW 264.7 cells up to 1000 µg/mL. Therefore, the amphiphilic Ugi-OSAOcT conjugates synthesized by the green method exhibited great potential to load hydrophobic drugs, acting as a promising nanocarrier capable of responding to pH for sustained release of hydrophobic drugs.

Hydroxypropyltrimethyl ammonium chloride chitosan-based hydrogel as the split H5N1 mucosal adjuvant: Structure-activity relationship

In this study, 2-hydroxypropyltrimethyl ammonium chloride chitosan (HTCC)-based hydrogel was devised as a mucosal adjuvant for H5N1 vaccine. Aimed to investigate the structure activity relationship between HTCC hydrogel and immune response, we prepared a series of HTCC hydrogel with defined quaternization degrees (DQs, 0%, 21%, 41%, 60%, 80%). Results suggested that with DQ increasing, the positive charge and gelation time of HTCC hydrogel increased but the viscosity decreased. We applied in vivo imaging system and found that the moderate DQ 41% prolonged antigen residence time in nasal cavity, resulting in the most potent systemic responses (IgG, IgG1, IgG2a, HI). While, the lowest DQ 0% produced the best mucosal IgA antibody responses, most likely due to the closer contact with mucosa. Furthermore, the influence of animal gender was also discussed. These data add to the growing understanding of the relationship between physicochemical features of chitosan-based hydrogel and how they influence the immune responses.

An Overview of Current Knowledge on the Properties, Synthesis and Applications of Quaternary Chitosan Derivatives

Chitosan, a chitin-derivative polysaccharide, known for its non-toxicity, biocompatibility and biodegradability, presents limited applications due to its low solubility in neutral or basic pH medium. Quaternization stands out as an alternative to modify this natural polymer, aiming to improve its solubility over a wide pH range and, consequently, expand its range of applications. Quaternization occurs by introducing a quaternary ammonium moiety onto or outside the chitosan backbone, via chemical reactions with primary amino and hydroxyl groups, under vast experimental conditions. The oldest and most common forms of quaternized chitosan involve N,N,N-trimethyl chitosan (TMC) and N-[(2-hydroxy-3-trimethyl ammonium) propyl] chitosan (HTCC) and, more recently, quaternized chitosan by insertion of pyridinium or phosphonium salts. By modifying chitosan through the insertion of a quaternary moiety, permanent cationic charges on the polysaccharide backbone are achieved and properties such as water solubility, antimicrobial activity, mucoadhesiveness and permeability are significantly improved, enabling the application mainly in the biomedical and pharmaceutical areas. In this review, the main quaternized chitosan compounds are addressed in terms of their structure, properties, synthesis routes and applications. In addition, other less explored compounds are also presented, involving the main findings and future prospects regarding the field of quaternized chitosans.

Regeneration behavior of chitosan from ionic liquid using water and alcohols as anti-solvents

While ionic liquids (ILs) have been considered as effective and "green" solvents for biopolymer processing, regeneration of IL-dissolved biopolymers could largely impact biopolymer structure and properties. This study indicates that the reconstitution of chitosan structure during regeneration from 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) depends on anti-solvent (water, methanol or ethanol) largely. Irrespective of anti-solvent, the chitosan chemical structure was not varied by dissolution or regeneration. With water, the regenerated chitosan had the highest crystallinity index of 54.18%, followed by those with methanol (35.07%) and ethanol (25.65%). Water as an anti-solvent could promote chitosan chain rearrangement, leading to the formation of an ordered aggregated structure and crystallites. Density functional theory (DFT) simulation indicates that the number of hydrogen bonds formed between anti-solvents and [Emim][OAc] was in the order of water > methanol > ethanol. With water used for regeneration, the aggregation and rearrangement of chitosan chains occurred more easily.

Quaternary Ammonium Chitosans: The Importance of the Positive Fixed Charge of the Drug Delivery Systems

As a natural polysaccharide, chitosan has good biocompatibility, biodegradability and biosecurity. The hydroxyl and amino groups present in its structure make it an extremely versatile and chemically modifiable material. In recent years, various synthetic strategies have been used to modify chitosan, mainly to solve the problem of its insolubility in neutral physiological fluids. Thus, derivatives with negative or positive fixed charge were synthesized and used to prepare innovative drug delivery systems. Positively charged conjugates showed improved properties compared to unmodified chitosan. In this review the main quaternary ammonium derivatives of chitosan will be considered, their preparation and their applications will be described to evaluate the impact of the positive fixed charge on the improvement of the properties of the drug delivery systems based on these polymers. Furthermore, the performances of the proposed systems resulting from in vitro and ex vivo experiments will be taken into consideration, with particular attention to cytotoxicity of systems, and their ability to promote drug absorption.

Marine-Derived Polymers in Ionic Liquids: Architectures Development and Biomedical Applications

Marine resources have considerable potential to develop high-value materials for applications in different fields, namely pharmaceutical, environmental, and biomedical. Despite that, the lack of solubility of marine-derived polymers in water and common organic solvents could restrict their applications. In the last years, ionic liquids (ILs) have emerged as platforms able to overcome those drawbacks, opening many routes to enlarge the use of marine-derived polymers as biomaterials, among other applications. From this perspective, ILs can be used as an efficient extraction media for polysaccharides from marine microalgae and wastes (e.g., crab shells, squid, and skeletons) or as solvents to process them in different shapes, such as films, hydrogels, nano/microparticles, and scaffolds. The resulting architectures can be applied in wound repair, bone regeneration, or gene and drug delivery systems. This review is focused on the recent research on the applications of ILs as processing platforms of biomaterials derived from marine polymers.

Water-soluble N-2-Hydroxypropyl trimethyl ammonium chloride chitosan enhanced the immunogenicity of inactivated porcine parvovirus vaccine vaccination on sows against porcine parvovirus infection

Porcine parvovirus (PPV) is one of the most common and important virus causes of infectious infertility in swine throughout the world. Inactivated PPV vaccine is broadly used, however, there is no appropriate immunomodulatory adjuvant for enhancing present vaccines and developing new ones. Therefore, in this study, the water-soluble N-2-Hydroxypropyl trimethyl ammonium chloride chitosan (N-2-HACC) was synthesized, the adjuvant potential of chitosan derivative was evaluated in inactivated PPV vaccine. Twenty adult healthy sows were assigned to four groups and vaccinated with synthesized PPV/N-2-HACC, commercial inactivated vaccine, N-2-HACC adjuvant and PBS. After insemination, all sows were challenged with the homologous PPV-H strain. In vivo immunization showed that sows immunized with the PPV/N-2-HACC induced more long-lasting HI antibodies and strong immune responses. Importantly, immunization of PPV/N-2-HACC significantly protected sows from homologous PPV-H strain infection. However, immunization of PPV/N-2-HACC didn't change the level of IL-2, IL-4 and IFN-γ and the production of CD4+, CD8 + T lymphocyte. The results indicated that PPV/N-2-HACC protect PPV infection mainly through enhancing the humoral immunity rather than cellular immunity. In addition, the mummified fetuses were observed from the control groups, but neither of the two vaccine groups. In conclusion, these results suggest that N-2-HACC can be exploited as an effective adjuvant for vaccine development, and the PPV/N-2-HACC are potent immunization candidates against PPV infection.

O-Carboxymethyl chitosan-based pH-responsive amphiphilic chitosan derivatives: Characterization, aggregation behavior, and application

Chitosan has attracted much attention in drug delivery, however, carboxymethyl chitosan (CMC)-based self-aggregated nanocarriers are seldom reported. In this paper, two kinds of CMC-based pH-responsive amphiphilic chitosan derivatives, N-2-hydroxylpropyl-3-butyl ether-O-carboxymethyl chitosan (HBCC) and N-2-hydroxylpropyl-3-(2-ethylhexyl glycidyl ether)-O-carboxymethyl chitosan (H2ECC), have been synthesized by the homogeneous reaction. The molecular structures were characterized by FTIR, ¹H NMR and ¹³C NMR. The optimum reaction condition was obtained based on the data of ¹H NMR spectrum: reaction time of 4 h, reaction temperature of 80 °C and n_epoxyn_-NH2 of 3/1, respectively. The XRD patterns showed the crystallinity of HBCC and H2ECC decreased due to the introduction of hydrophobic segments. The thermostability of HBCC and H2ECC was improved for the formation of heat-resistant stereo-complexed structures. The intermolecular hydrophobic interaction hindered the intermolecular mobility by increasing glass transition temperature of ca. 10 °C. Both HBCC and H2ECC have very low critical aggregation concentrations (HBCC: 0.66-1.56 g/L, H2ECC: 0.57-1.07 g/L) and moderate aggregate particle size, which is advantageous for utilization as a drug carrier. The curcumin loaded HBCC and H2ECC aggregates showed nontoxicity, meanwhile, HBCC and H2ECC showed good antibacterial activity against Staphylococcus aureus and Escherichia coli. As a result of these two favorable properties, HBCC and H2ECC could be used as curcumin nanocarriers as well as antibacterial agents.

Trimethyl Chitosan/Siloxane-Hybrid Coated Fe3O4 Nanoparticles for the Uptake of Sulfamethoxazole from Water

The presence of several organic contaminants in the environment and aquatic compartments has been a matter of great concern in the recent years. To tackle this problem, new sustainable and cost-effective technologies are needed. Herein we describe magnetic biosorbents prepared from trimethyl chitosan (TMC), which is a quaternary chitosan scarcely studied for environmental applications. Core@shell particles comprising a core of magnetite (Fe3O4) coated with TMC/siloxane hybrid shells (Fe3O4@SiO2/SiTMC) were successfully prepared using a simple one-step coating procedure. Adsorption tests were conducted to investigate the potential of the coated particles for the magnetically assisted removal of the antibiotic sulfamethoxazole (SMX) from aqueous solutions. It was found that TMC-based particles provide higher SMX adsorption capacity than the counterparts prepared using pristine chitosan. Therefore, the type of chemical modification introduced in the chitosan type precursors used in the surface coatings has a dominant effect on the sorption efficiency of the respective final magnetic nanosorbents.

Uniform Core-Shell Nanoparticles with Thiolated Hyaluronic Acid Coating to Enhance Oral Delivery of Insulin

Oral delivery of protein drugs is an attractive route of administration due to its convenience for repeated dosing and good patient compliance. However, currently oral protein therapeutics show very low bioavailability mainly due to the existence of hostile gastrointestinal (GI) environments, including mucus layers and intestinal epithelial barriers. Herein, using insulin as a model protein therapeutic, the core-shell nanoparticles with thiolated hyaluronic acid (HA-SH) coating (NP_HA-SH ) are produced utilizing a two-step flash nanocomplexation process to enhance oral delivery efficiency of insulin. A positively charged nanoparticle core is first generated by electrostatic complexation between insulin and N-(2-hydroxypropyl)-3-trimethyl ammonium chloride modified chitosan (HTCC), followed by surface coating with HA-SH. The optimized NP_HA-SH shows an average size of 100 nm with high encapsulation efficiency (91.1%) and loading capacity (38%). In vitro and ex vivo results confirm that NP_HA-SH shows high mucus-penetration ability, improved intestinal retention and transepithelial transport property due to its thiolated surface and the ability of HA-SH coating to dissociate from the nanoparticle surface when across the mucosal layer. Oral administration of NP_HA-SH to Type 1 diabetic rats yields high efficacy and an average relative bioavailability of 11.3%. These results demonstrate that the HA-SH coated core-shell nanoparticles are a promising oral delivery vehicle for protein therapeutics.

Chitosan Derivatives: Introducing New Functionalities with a Controlled Molecular Architecture for Innovative Materials

The functionalization of polymeric substances is of great interest for the development of innovative materials for advanced applications. For many decades, the functionalization of chitosan has been a convenient way to improve its properties with the aim of preparing new materials with specialized characteristics. In the present review, we summarize the latest methods for the modification and derivatization of chitin and chitosan under experimental conditions, which allow a control over the macromolecular architecture. This is because an understanding of the interdependence between chemical structure and properties is an important condition for proposing innovative materials. New advances in methods and strategies of functionalization such as the click chemistry approach, grafting onto copolymerization, coupling with cyclodextrins, and reactions in ionic liquids are discussed.

A Review of Injectable Polymeric Hydrogel Systems for Application in Bone Tissue Engineering

Biodegradable, stimuli-responsive polymers are essential platforms in the field of drug delivery and injectable biomaterials for application of bone tissue engineering. Various thermo-responsive hydrogels display water-based homogenous properties to encapsulate, manipulate and transfer its contents to the surrounding tissue, in the least invasive manner. The success of bioengineered injectable tissue modified delivery systems depends significantly on their chemical, physical and biological properties. Irrespective of shape and defect geometry, injectable therapy has an unparalleled advantage in which intricate therapy sites can be effortlessly targeted with minimally invasive procedures. Using material testing, it was found that properties of stimuli-responsive hydrogel systems enhance cellular responses and cell distribution at any site prior to the transitional phase leading to gelation. The substantially hydrated nature allows significant simulation of the extracellular matrix (ECM), due to its similar structural properties. Significant current research strategies have been identified and reported to date by various institutions, with particular attention to thermo-responsive hydrogel delivery systems, and their pertinent focus for bone tissue engineering. Research on future perspective studies which have been proposed for evaluation, have also been reported in this review, directing considerable attention to the modification of delivering natural and synthetic polymers, to improve their biocompatibility and mechanical properties.

Quaternized Chitosan-Capped Mesoporous Silica Nanoparticles as Nanocarriers for Controlled Pesticide Release

Nanotechnology-based pesticide formulations would ensure effective utilization of agricultural inputs. In the present work, mesoporous silica nanoparticles (MSNs) with particle diameters of ~110 nm and pore sizes of ~3.7 nm were synthesized via a liquid crystal templating mechanism. A water-soluble chitosan (CS) derivative (N-(2-hydroxyl)propyl-3-trimethyl ammonium CS chloride, HTCC) was successfully capped on the surface of pyraclostrobin-loaded MSNs. The physicochemical and structural analyses showed that the electrostatic interactions and hydrogen bonding were the major forces responsible for the formation of HTCC-capped MSNs. HTCC coating greatly improved the loading efficiency (LC) (to 40.3%) compared to using bare MSNs as a single encapsulant (26.7%). The microstructure of the nanoparticles was revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The pyraclostrobin-loaded nanoparticles showed an initial burst and subsequent sustained release behavior. HTCC-capped MSNs released faster than bare MSNs in the initial stage. Pyraclostrobin-loaded HTCC-capped MSNs with half doses of pyraclostrobin technical demonstrated almost the same fungicidal activity against Phomopsis asparagi (Sacc.), which obviously reduced the applied pesticide and enhanced the utilization efficiency. Therefore, HTCC-decorated MSNs demonstrated great potential as nanocarriers in agrochemical applications.

Quaternized Chitosan-Capped Mesoporous Silica Nanoparticles as Nanocarriers for Controlled Pesticide Release

Nanotechnology-based pesticide formulations would ensure effective utilization of agricultural inputs. In the present work, mesoporous silica nanoparticles (MSNs) with particle diameters of ~110 nm and pore sizes of ~3.7 nm were synthesized via a liquid crystal templating mechanism. A water-soluble chitosan (CS) derivative (N-(2-hydroxyl)propyl-3-trimethyl ammonium CS chloride, HTCC) was successfully capped on the surface of pyraclostrobin-loaded MSNs. The physicochemical and structural analyses showed that the electrostatic interactions and hydrogen bonding were the major forces responsible for the formation of HTCC-capped MSNs. HTCC coating greatly improved the loading efficiency (LC) (to 40.3%) compared to using bare MSNs as a single encapsulant (26.7%). The microstructure of the nanoparticles was revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The pyraclostrobin-loaded nanoparticles showed an initial burst and subsequent sustained release behavior. HTCC-capped MSNs released faster than bare MSNs in the initial stage. Pyraclostrobin-loaded HTCC-capped MSNs with half doses of pyraclostrobin technical demonstrated almost the same fungicidal activity against Phomopsis asparagi (Sacc.), which obviously reduced the applied pesticide and enhanced the utilization efficiency. Therefore, HTCC-decorated MSNs demonstrated great potential as nanocarriers in agrochemical applications.

Positively Charged Nanostructured Lipid Carriers and Their Effect on the Dissolution of Poorly Soluble Drugs

The objective of this study is to develop suitable formulations to improve the dissolution rate of poorly water soluble drugs. We selected lipid-based formulation as a drug carrier and modified the surface using positively charged chitosan derivative (HTCC) to increase its water solubility and bioavailability. Chitosan and HTCC-coated lipid particles had higher zeta-potential values than uncoated one over the whole pH ranges and improved encapsulation efficiency. In vitro drug release showed that all NLC formulations showed higher in vitro release efficiency than drug particle at pH 7.4. Furthermore, NLC formulation prepared with chitosan or HTCC represented good sustained release property. The results indicate that chitosan and HTCC can be excellent formulating excipients of lipid-based delivery carrier for improving poorly water soluble drug delivery.