Long-alkane-chain modified N-phthaloyl chitosan membranes with controlled permeability

Chitosan nanocoatings N-acylated with decanoic anhydride: Hydrophobic, hygroscopic and structural properties

Thin (ca. 340 nm) chitosan coatings were deposited onto glass substrates via dip-coating, then modified with the methanol solution of decanoic anhydride (0.17-56 mM). NMR, FTIR and XPS measurements confirmed that the acylation degree increased from 18 % to 45 %, and at the highest degree, the whole layer was acylated homogeneously by the reagent molecules. The coating thickness increased (up to 60 %), and the refractive index decreased (from 1.541 to 1.532) due to the acylation, that was determined by UV-visible spectroscopy. The AFM did not reveal morphological changes, but wetting tests showed that the acylation rendered the coating hydrophobic (water contact angle increased from ca. 75° to 100°). The contact angle, however, decreased to 85° due to the development of a second molecular layer of the decanoic acid by-product at the highest (over 25 mM) reagent concentrations. XRD studies showed a self-assembling structuring of the alkyl-chains in the bulk phase, which occurred in the case of the highest degree of acylation. This also manifested itself in a significant decrease of the layer hygroscopicity: the swelling degree decreased from 40 % to 8 % in a saturated water atmosphere monitored by spectroscopic ellipsometry.

Study of the antibacterial and cytotoxic activity of chitosan and its derivatives chemically modified with phthalic anhydride and ethylenediamine

The insertion of hydrophobic and hydrophilic chains in the chitosan molecule can improve its antibacterial activity, expanding its range of application in several areas of medical-pharmaceutical sciences. Thus, this work aimed to increase the antibacterial activity of chitosan through the modification reaction with phthalic anhydride (QF) and subsequent reaction with ethylenediamine (QFE). The chitosan and derivatives obtained were characterized by elemental analysis, 13C Nuclear Magnetic Resonance (13C NMR), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TG), where it was possible to prove the chemical modification. Both materials showed a greater antibacterial inhibitory effect against Gram-positive bacteria, Staphylococcus aureus, emphasizing antibacterial activity against Gram-negative bacteria, Escherichia coli, with values above 70 % of the inhibitory effect, which is a promising result. Assays with human fibroblast cells by the [3-(4,5-dimethylthiazolyl)-2,5-diphenyl tetrazolium (MTT)] bromide reduction test did not indicate toxicity in the materials. Thus, the derived materials showed promise for biomedical applications since they combined excellent antibacterial activity against gram-positive and gram-negative strains and did not show cytotoxicity.

Study the anticancer efficacy of doxorubicin-loaded redox-responsive chitosan-derived nanoparticles in the MDA-MB-231 cell line

This study focuses on the design and evaluation of redox-responsive nanoparticles (NPs) by synthesizing disulfide-containing N-phthaloyl chitosan-SS-methoxy poly(ethylene glycol) (NPC-SS-mPEG) and incorporating the anti-cancer drug doxorubicin into the NPs. The structural features of NPC-SS-mPEG were investigated using FTIR, NMR, XRD, and TGA/DTA analysis. DLS and TEM analysis confirmed the particle size and morphology of the NPs. The stability of the NPs was measured with the presence and absence of glutathione (GSH) in buffers pH 5 and 7.4. Furthermore, the release of DOX from the NPs was studied in GSH (10 mM) containing/absent medium at pH 5 and pH 7.4 which mimics the intracellular environment with redox potential. The results indicated a significantly increased release of DOX in the GSH containing medium pH 5 (82.9 ± 2.1 %) and pH 7.4 (67.37 ± 0.88 %) compared to the GSH free pH 7.4 (29.99 ± 1.01 %) and pH 5 medium (56.56 ± 1.7 %) at 60 h. The cytotoxicity study in the MDA-MB-231 breast cancer cell line by MTT assay indicated higher toxicity of redox-responsive NPs to cancer cells than free DOX. In concurrence with the cytotoxicity assay, in-vitro fluorescence staining assays (AO/EB, Hoechst, ROS generation) also confirmed that NPs loaded with DOX induce higher toxicity to cancer cells than free DOX. Taken together, the overall results confirmed the superiority of the redox response-mediated release of DOX in effectively controlling cancer progression.

Regioselective modification at the 2,3- and 6-positions of chitosan with phenylcarbamates for chromatographic enantioseparation

Chitosan derivatives with two different phenylcarbamate pendants at the 6-position and 2,3-positions of the glucosamine unit were synthesized by triphenylmethyl as a protective group. The regioselective chitosan derivatives were prepared corresponding to coated-type chiral packed materials (CPMs), which were evaluated with thirteen chiral compounds by high-performance liquid chromatography (HPLC). The regioselective chitosan derivatives (4aⅠ/4aⅡ, 4bⅠ/4bⅡ) bearing electron-withdrawing 3,5‑chloro or 4‑chloro at the 6-position can recognize 7 or 8 of the 13 enantiomers and achieve baseline separation for enantiomers 5 and 7. They exhibited better chiral recognition abilities than the other derivatives with different substituents at the 6-position and the same 3,5-dimethylphenyl substituent at the 2,3-postion. In comparison to Chit-1 featuring a 3,5-dimethylphenyl substituent at the 2,3- and 6-positions, it was observed that the combination of both an electron-withdrawing and an electron-donating substituent of the regioselective chitosan derivatives (4aⅠ/4aⅡ, 4bⅠ/4bⅡ) showed better or similar enantioseparation abilities for racemic Compounds 7 and 6, respectively. The molecular weight-performance relationship of the regioselective chitosan derivatives was investigated in detail. It was found that with increasing molecular weight, the derivatives 4aⅡ and 4bⅡ all possessed greater enantioseparation power for 4 enantiomers, such as enantiomers 4, 7, 11, and 15, than the corresponding derivatives with low molecular weights. The molecular docking simulation results showed that excellent enantioseparation power significantly depended on the combination and interaction of multiple factors, such as steric hindrance, and polarity of the substituents on the CPMs and enantiomers.

Asymmetric fabrication and in vivo evaluation of the wound healing potency of electrospun biomimetic nanofibrous scaffolds based on collagen crosslinked modified-chitosan and graphene oxide quantum dot nanocomposites

Asymmetric scaffolds were developed through electrospinning by utilizing biocompatible materials for effective wound healing applications. First of all, the chitosan surface was modified with decanoyl chloride and crosslinked with collagen to synthesize collagen crosslinked modified-chitosan (CG-cross-CS-g-Dc). Then, the asymmetric scaffolds were fabricated through electrospinning, where the top layer was a monoaxial nanofiber of the PCL/graphene oxide quantum dot (GOQD) nanocomposite and the bottom layer was a coaxial nanofiber having PCL in the core and the CG-cross-CS-g-Dc/GOQD nanocomposite in the shell layer. The formation of monoaxial (∼130 ± 50 nm) and coaxial (∼320 ± 40 nm) nanofibers was confirmed by transmission electron microscopy (TEM). The presence of GOQDs contributed to antioxidant and antimicrobial efficacy. These scaffolds showed substantial antibacterial activity against the common wound pathogens Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The scaffolds exhibited excellent cytocompatibility (MTT assay) and anti-inflammatory behaviour as analysed via the cytokine assay and biochemical analysis. The in vivo wound healing potential of the nanofibrous scaffolds was assessed with full-thickness excisional wounds in a rat model. The scaffolds accelerated the re-epithelialization as well as the collagen deposition, thereby facilitating the wound healing process in a very short span of time (10 days). Both in vitro and in vivo analyses thus provide a compelling argument for the use of these scaffolds as therapeutic biomaterials and their suitability for application in rapid wound regeneration and repair.

Quaternized carbon dots with enhanced antimicrobial ability towards Gram-negative bacteria for the treatment of acute peritonitis caused by E. coli

Infections caused by Gram-negative bacteria still pose a clinical challenge. Although nanomaterials have been developed for antibacterial treatments, a systematic evaluation of the mechanisms and intervention models of antibacterial materials toward Gram-negative bacteria is still lacking. Herein, antibacterial quaternized carbon dots (QCDs) were synthesized via a one-step melting method using anhydrous citric acid and diallyl dimethyl ammonium chloride (DDA). The QCDs exhibited effective broad-spectrum antibacterial activity and enhanced inhibitory ability towards Gram-negative bacteria. The antibacterial mechanism of the QCDs with respect to Gram-negative bacteria was investigated through the characterization of bacterial morphology changes, the absorption modes of the QCDs on bacteria, and the potential generation of reactive oxygen species by the QCDs. The QCDs showed low toxicity in different cells, and did not cause hemolysis. The QCDs were administered via intraperitoneal injection to treat acute peritonitis in mice infected with E. coli. Routine blood examination, magnetic resonance imaging, and pathological analysis were undertaken and it was found that, similar to the positive control group treated with gentamicin sulfate, the QCDs exhibited a therapeutic effect that eliminated infection and inflammation. This study explores a controllable synthetic strategy for the synthesis of active carbon dots with antibacterial activity, a material that is a promising candidate for new treatments of Gram-negative bacterial infections.

Water-soluble amino functionalized chitosan: Preparation, characterization, antioxidant and antibacterial activities

Amino functionalized chitosan has attracted much attention because of the fascinated bioactivities. In our study, a novel water-soluble amino functionalized chitosan bearing free amino group at C-2 and quaternary ammonium moiety contained free amino group at C-6 (5c) was prepared by a four-step method. The structural characterization was identified by FTIR and ¹H NMR spectroscopy. The water-solubility and antioxidant activities against hydroxyl, DPPH radicals and reducing power were estimated. The results displayed that amino functionalized chitosan 5c exhibited improved water-solubility and antioxidant ability, especially its DPPH scavenging rate reached about 90 % at the minimum test concentration of 0.10 mg/mL. Besides, antibacterial tests showed that amino functional chitosan 5c had best antibacterial activities, which indicated that amino group made main contribution to the enhanced bioactivities. In short, the novel chitosan 5c possessed enhanced water-solubility and excellent antioxidant and antibacterial activities, which could provide novel strategy for the development of antioxidant and antibacterial agents in biomedicine and food fields.

Chitosan: Sources, Processing and Modification Techniques

Chitosan, a copolymer of glucosamine and N-acetyl glucosamine, is derived from chitin. Chitin is found in cell walls of crustaceans, fungi, insects and in some algae, microorganisms, and some invertebrate animals. Chitosan is emerging as a very important raw material for the synthesis of a wide range of products used for food, medical, pharmaceutical, health care, agriculture, industry, and environmental pollution protection. This review, in line with the focus of this special issue, provides the reader with (1) an overview on different sources of chitin, (2) advances in techniques used to extract chitin and converting it into chitosan, (3) the importance of the inherent characteristics of the chitosan from different sources that makes them suitable for specific applications and, finally, (4) briefly summarizes ways of tailoring chitosan for specific applications. The review also presents the influence of the degree of acetylation (DA) and degree of deacetylation (DDA), molecular weight (M_w) on the physicochemical and biological properties of chitosan, acid-base behavior, biodegradability, solubility, reactivity, among many other properties that determine processability and suitability for specific applications. This is intended to help guide researchers select the right chitosan raw material for their specific applications.

Novel Chitosan Derivatives and Their Multifaceted Biological Applications

Chitosan is a rather attractive material, especially because of its bio-origins as well as generation from exoskeletal waste. As the mantle has been effectively transferred from chitin to chitosan, so has it been extrapolated to in-house synthesized novel chitosan derivatives. This review comprehensively lists the available novel chitosan derivatives (ChDs) and summarizes their biological applications. The fact that chitosan derivatives do comprise multifaceted biological applications is attested by the voluminous reports on their varied contributions. However, this review points out to the fact that there has been selective focus on bio functions such as antifungal, antioxidant, antibacterial, whereas other biomedical applications and antiviral applications remain relatively less explored. With their current functionality record, there is definitely no doubt that the plethora of synthesized ChDs will have a profound impact on the unexplored biological aspects. This review points out this lacuna as room for future exploration.

Chitosan Natural Polymer Material for Improving Antibacterial Properties of Textiles

In recent years, the textile industry has been seeking to develop innovative products. It is a good choice to organically combine materials with superior functional characteristics and commercial textiles to form products with excellent performance. In particular, textiles made of biological functional materials are often beneficial to human health, which is an interesting research direction. As a biopolymer material, chitosan has the advantages of strong availability, low cost, excellent safety, outstanding performance, etc., particularly the antibacterial property, and has broad application prospects in the textile field. This review provides an overview of the latest literature and summarizes recent innovations and state-of-the-art technologies that can add value to textiles. To this end, preparation of chitosan fiber, synthesis of chitosan nanofiber, antibacterial activity of chitosan fiber, antibacterial activity of chitosan nanofiber, etc., will be discussed. Furthermore, the challenges and prospects of chitosan-based materials used in textiles are evaluated. Importantly, this review can not only help researchers understand the development status of antibacterial textiles, but also help researchers discover and solve problems in this field through comparative reading.

Cationic chitosan derivatives as potential antifungals: A review of structural optimization and applications

The increasing resistance of pathogen fungi poses a global public concern. There are several limitations in current antifungals, including few available fungicides, severe toxicity of some fungicides, and drug resistance. Therefore, there is an urgent need to develop new antifungals with novel targets. Chitosan has been recognized as a potential antifungal substance due to its good biocompatibility, biodegradability, non-toxicity, and availability in abundance, but its applications are hampered by the low charge density results in low solubility at physiological pH. It is believed that enhancing the positive charge density of chitosan may be the most effective approach to improve both its solubility and antifungal activity. Hence, this review mainly focuses on the structural optimization strategy of cationic chitosan and the potential antifungal applications. This review also assesses and comments on the challenges, shortcomings, and prospect of cationic chitosan derivatives as antifungal therapy.

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.

Permeability of P and K-nutrient through polystyrene membrane from aqueous solutions of urea + KH2PO4

With the polymer-coated fertilizer as background, the permeability of P- and K-nutrient through a representative polymer membrane-polystyrene membrane were investigated by measuring their permeability in the solutions of KH2PO4-water and urea-KH2PO4-water at nominal temperature of 298 K using the Ussing chamber method. To analyze and interpret the variation of permeability with solute concentration, the solubility of permeate in polymer membrane were determined experimentally and the permeate diffusion coefficient were assessed by the measurements of density and apparent molar volume of the aqueous fertilizer solutions. An interesting “increase-decrease” trend for the permeability of both phosphorous (P)-nutrient, and potassium (K)-nutrient fertilizer with permeate concentration was observed, in which the increases in permeability at low concentrations of permeate could be attributed to the increase in solubility of KH2PO4 in polymer while the decreases in permeability at high concentrations was due to the decrease in diffusion coefficient of permeate in polymer membrane. Finally, the release kinetics of these nutrients from a PS-coated urea-KH2PO4 compound fertilizer granule was predicted using the Shaviv’s model along with the permeability data of P- and K-nutrient generated.

Reducing nitrogen losses through ammonia volatilization and surface runoff to improve apparent nitrogen recovery of double cropping of late rice using controlled release urea

Controlled release fertilizer can reduce nitrogen losses to the environment while increasing grain yield and improving apparent nitrogen recovery (ANR) of rice. However, few studies have evaluated the comparative efficacy of different polymer-coated urea products on nitrogen (N) losses, ANR, and N uptake of rice. A 2-year field experiment was conducted to compare the effects of three different types of polymer-coated urea fertilizer on nitrogen losses through NH₃ volatilization and surface runoff to the environment, ANR, grain yield, and N uptake as compared to conventional urea of rice. Six treatments including (1) control with 0 kg N ha^-1 (CK), (2) basal application of urea (U_b), (3) split application (U_s) of urea (50% at transplanting, 25% at tillering, and 25% at panicle stages), (4) CRU-1 (polyurethane-coated urea), (5) CRU-2 (degradable polymer-coated urea), and (6) CRU-3 (water-based polymer-coated urea) all applied at 165 kg N ha^-1. It was found that CRU-2 resulted in the highest grain yield and panicle numbers among the N fertilization treatments in 2013 and 2014. Applying CRU could help increase N uptake in rice, reduce N losses through NH₃ volatilization and surface runoff, and hence improve ANR. Its single dose can meet the nutrient demand of the rice plant. Controlled release urea could be adopted as an effective mitigation alternative to retard N losses through NH₃ volatilization and surface runoff while improving ANR of double cropping of late rice.

Synthesis and characterization of 3,6-O,O'- dimyristoyl chitosan micelles for oral delivery of paclitaxel

The aim of the present study was to investigate the potential application of 3,6-O,O'- dimyristoyl chitosan DMCh, an amphiphilic derivative of chitosan, for improving the oral bioavailability of paclitaxel (PTX), a water insoluble anticancer drug. The O-acylation of chitosan with myristoyl chloride was carried out by employing high (≈13.3) or low (2.0) molar excess of chitosan to result in samples DMCh07 and DMCh12, respectively. The successful O-acylation of chitosan was confirmed by FTIR and ¹H NMR spectroscopy, the latter allowing also the determination of average degree of substitution (DS). The critical aggregation concentration (CAC) of samples DMCh07 (DS≈6.8%) and DMCh12 (DS≈12.0%) were 8.9×10^-3mg/mL and 13.2×10³mg/mL, respectively. It was observed by TEM that the DMCh micelles showed spherical shape while DLS measurements allowed the determination of their average size (287nm-490nm) and zeta potential (+32mV to +44mV). Such DMCh micelles were able to encapsulate paclitaxel with high drug encapsulation efficiency (EE), as confirmed by HPLC analyses. Studies on the cytotoxicity of DMCh07 micelles toward Caco-2 and HT29-MTX cells showed that, regardless the PTX loaded, DMCh07 micelles slightly decreased cellular viability at low micelles concentration (≤1μg/mL) while at high concentration (>10μg/mL) PTX-loaded DMCh07 micelles were less toxic toward Caco-2 cells when compared to free PTX. The PTX permeation across Caco-2 monoculture and Caco-2/HT29-MTX co-culture model confirmed the potential of DMCh micelles in improving the intestinal absorption of PTX. These results suggest that DMCh micelles may be a promising carrier to encapsulate PTX aiming cancer therapy.

Amphiphilic polysaccharide nanocarriers with antioxidant properties

The development of self-assembled nanocarriers for the encapsulation of hydrophobic antioxidants is of growing interest. Self-assembled amphiphilic chitosan conjugate nanocarriers that stabilize antioxidants were prepared based on the concept that both the nanocarrier and the antioxidant bear similar hydrophobic moieties able to establish hydrophobic interactions. This work describes the preparation and characterization of a system consisting of a palmitoyl chitosan conjugate and retinyl palmitate. Palmitic acid was coupled to chitosan using a carbodiimide-mediated coupling reaction, and two different palmitoyl chitosan conjugates were obtained by varying the coupling system. Palmitoyl chitosan conjugates self-assembled to form nanoparticles in aqueous medium varying in mean average diameter (Dh) between 200 and 437 nm. Retinyl palmitate–loaded nanoparticles were prepared by a solvent displacement method using dialysis, with loading efficiencies of 77.5% and 88.6%, loading contents of 12.6% and 14.6%, and Dh values of approximately 280 nm. The zeta potential (ζ) of all palmitoyl chitosan nanoparticle were above 25 mV, but ζ slightly increased in the retinyl palmitate–loaded nanoparticle. Antioxidant activity of loaded nanoparticles was confirmed using the 1,1-diphenyl-2-picryl-hydrazyl radical scavenging assay. The in vitro cytotoxicity of blank and loaded nanoparticles was determined using fibroblasts of human embryonic skin. All nanoparticles were not cytotoxic when they were tested with methylthiazol tetrazolium and lactate dehydrogenase tests. The obtained results suggest that the system has potential as a nanocarrier for dermal application. Additionally, the approach considered in this article can be expanded to other nanocarrier/antioxidant systems.

Enhancement of the controlled-release properties of chitosan membranes by crosslinking with suberoyl chloride

A novel crosslinking agent, suberoyl chloride, was used to crosslink N-phthaloyl acylated chitosan and improves the properties of chitosan membranes. Membranes with different crosslinking degrees were synthesized. The derivatives were characterized by Fourier transform infrared spectroscopy and ¹³C solid state nuclear magnetic resonance spectroscopy, which indicated that the crosslinking degrees ranged from 0 to 7.4%. The permeabilities of various plant nutrients, including macroelements (N, P, K), microelements (Zn²⁺ and Cu²⁺), and a plant growth regulator (naphthylacetic acid), were varied by moderate changes in crosslinking degree, indicating that the controlled-release properties can be regulated in this way. The film-forming ability of native chitosan was maintained, whilst mechanical properties, hydrophobicity and controlled permeability were improved. These dramatic improvements occurred with a small amount of added suberoyl chloride; excessive crosslinking led to membranes with unwanted poor permeability. Thus, both the mechanical properties and permeability of the crosslinked membrane can be optimized.