A Review of Chitosan and Chitosan Nanofiber: Preparation, Characterization, and Its Potential Applications

Chitosan is produced by deacetylating the abundant natural chitin polymer. It has been employed in a variety of applications due to its unique solubility as well as its chemical and biological properties. In addition to being biodegradable and biocompatible, it also possesses a lot of reactive amino side groups that allow for chemical modification and the creation of a wide range of useful derivatives. The physical and chemical characteristics of chitosan, as well as how it is used in the food, environmental, and medical industries, have all been covered in a number of academic publications. Chitosan offers a wide range of possibilities in environmentally friendly textile processes because of its superior absorption and biological characteristics. Chitosan has the ability to give textile fibers and fabrics antibacterial, antiviral, anti-odor, and other biological functions. One of the most well-known and frequently used methods to create nanofibers is electrospinning. This technique is adaptable and effective for creating continuous nanofibers. In the field of biomaterials, new materials include nanofibers made of chitosan. Numerous medications, including antibiotics, chemotherapeutic agents, proteins, and analgesics for inflammatory pain, have been successfully loaded onto electro-spun nanofibers, according to recent investigations. Chitosan nanofibers have several exceptional qualities that make them ideal for use in important pharmaceutical applications, such as tissue engineering, drug delivery systems, wound dressing, and enzyme immobilization. The preparation of chitosan nanofibers, followed by a discussion of the biocompatibility and degradation of chitosan nanofibers, followed by a description of how to load the drug into the nanofibers, are the first issues highlighted by this review of chitosan nanofibers in drug delivery applications. The main uses of chitosan nanofibers in drug delivery systems will be discussed last.

Chitosan-g-polyacrylonitrile ZnO nano-composite, synthesis and characterization as new and good adsorbent for Iron from groundwater

The highly poisonous, non-biodegradable heavy metals present serious concern in wastewater environmental sustainability and human health. Using adsorption is an effective technology for the treatment of this kind of water. Therefore, developing efficient and cost-effective adsorbents considers a significant and an emerging topic in the field the water purification. Chitosan grafted polyacrylonitrile (Cs-g-PAN) was facially fabricated via graft polymerization using ammonium persulfate (APS) as the initiator. The simple ultrasonic technique was used for doping ZnO nanoparticles into the Cs-g-PAN matrix to prepare chitosan-grafted polyacrylonitrile/ZnO (Cs-g-PAN/ZnO). For comparative study, pure ZnO and nanocomposite of PAN doped with ZnO (PAN/ZnO) were also prepared. XRD, FTIR, SEM, TEM, BET, EDS, and TGA measurements were conducted to confirm the morphological and structural properties of the prepared materials. Cs-g-PAN/ZnO possesses a specific surface area of 20.23 m²/g with a pore size of 31.58 nm and pore volume of 0.16 cm³ g^-1. The adsorption behavior toward Fe(II) as a pollutant for groundwater was studied for the synthesized materials. The effect of pH (4-8), contact time (5-60 min), adsorbent dose (0.01-0.3 g), and different temperature degrees (278, 288, 298, 308, and 318 K) on the removal of iron (II) has been conducted. The removal efficiency was achieved 100 % under the optimum condition, at pH = 7, contact time 30 min, adsorbate concentration 0.93 mg/L, and adsorbent dosage 0.05 g/L at room temperature. Langmuir and Freundlich's isothermal and kinetic studies have been analyzed to determine the adsorption mechanism of Fe(II) ions on the synthesized nanomaterials. The adsorption process of Fe(II) over the surface of prepared catalysts proceeded via the Langmuir model and pseudo-second-order reaction kinetics with R² > 0.99. Suggesting the formation of Fe(II) monolayer over the adsorbent surface and the rate-limiting step is probably controlled by chemisorption through sharing the electrons between Fe⁺² and the prepared catalyst.

Dual (pH and thermal) stimuli-responsive Pickering emulsion stabilized by chitosan-carrageenan composite microgels

Formulation of water-in-oil (W/O) Pickering emulsion (PE) for food applications has been largely restricted by the limited choices of food-grade Pickering emulsifiers. In this study, composite microgels made of chitosan and carrageenan were explored as a dual (pH and thermal) stimuli-responsive Pickering emulsifier for the stabilization of W/O PE. The chitosan-carrageenan (CS-CRG) composite microgels not only exhibited pH- and thermo-responsiveness, but also displayed enhanced lipophilicity as compared to the discrete polymers. The stability of the CS-CRG-stabilized W/O PE system (CS-CRG PE) was governed by CS:CRG mass ratio and oil fractions used. The CS-CRG PE remained stable at acidic pH and at temperatures below 40 °C. The instability of CS-CRG composite microgels at alkaline pH and at temperatures above 40 °C rendered the demulsification of CS-CRG PE. This stimuli-responsive W/O PE could unlock new opportunities for the development of stimuli-responsive W/O PE using food-grade materials.

Chitosan-Based Biomaterials: Insights into Chemistry, Properties, Devices, and Their Biomedical Applications

Chitosan is a marine-origin polysaccharide obtained from the deacetylation of chitin, the main component of crustaceans’ exoskeleton, and the second most abundant in nature. Although this biopolymer has received limited attention for several decades right after its discovery, since the new millennium chitosan has emerged owing to its physicochemical, structural and biological properties, multifunctionalities and applications in several sectors. This review aims at providing an overview of chitosan properties, chemical functionalization, and the innovative biomaterials obtained thereof. Firstly, the chemical functionalization of chitosan backbone in the amino and hydroxyl groups will be addressed. Then, the review will focus on the bottom-up strategies to process a wide array of chitosan-based biomaterials. In particular, the preparation of chitosan-based hydrogels, organic–inorganic hybrids, layer-by-layer assemblies, (bio)inks and their use in the biomedical field will be covered aiming to elucidate and inspire the community to keep on exploring the unique features and properties imparted by chitosan to develop advanced biomedical devices. Given the wide body of literature that has appeared in past years, this review is far from being exhaustive. Selected works in the last 10 years will be considered.

A Novel Hydrophilic, Antibacterial Chitosan-Based Coating Prepared by Ultrasonic Atomization Assisted LbL Assembly Technique

To explore the potential applicability of chitosan (CTS), we prepared aldehyde chitosan (CTS-CHO) with chitosan and sodium periodate via oxidation reaction and then a chitosan-based hydrophilic and antibacterial coating on the surface of poly (lactic acid) (PLA) film was developed and characterized. The oxidation degree was determined by Elemental analyser to be 12.53%, and a Fourier transform infrared spectroscopy was used to characterize the structure of CTS-CHO. It was evident that CTS-CHO is a biocompatible coating biomaterial with more than 80% cell viability obtained through the Live/Dead staining assay and the alamarBlue assay. The hydrophilic and antibacterial CTS-CHO coating on the PLA surface was prepared by ultrasonic atomization assisted LbL assembly technique due to Schiff's base reaction within and between layers. The CTS-CHO coating had better hydrophilicity and transparency, a more definite industrialization potential, and higher antibacterial activity at experimental concentrations than the CTS coating. All of the results demonstrated that the ultrasonic atomization-assisted LbL assembly CTS-CHO coating is a promising alternative for improving hydrophilicity and antibacterial activity on the PLA surface. The functional groups of CTS-CHO could react with active components with amino groups via dynamic Schiff's base reaction and provide the opportunity to create a drug releasing surface for biomedical applications.

The Synergistic Effect of Biochar and Poly(2-ethyl-2-oxazoline)/poly(2- hydroxyethylmethacarylate)/Chitosan) Hydrogels on Saline Soil Properties and Carrot Productivity.. [DOI: 10.21203/rs.3.rs-2409982/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Background Soil Salinity is one of the most important factors limiting crop production. Moreover, with the increasing population and saline soil worldwide there is no choice but to use saline soil to increase the agricultural area. Therefore, to increase carrot productivity under saline conditions, it's necessary to provide good management such as applying hydrogels and biochar for improving soil properties. Methodology Hydrogels (PEtOx-HEMA-CS) were prepared from poly (2-ethyl-2-oxazoline), chitosan (CS), and 2-hydroxyethyl methacrylate (HEMA as crosslinker), by exposure those to gamma irradiation at range from 0–50 kGy with 0.9 kGy/h, and obtained three types of hydrogels according to concentration of chitosan. The PEtOx-HEMA-CS hydrogels were prepared for enhanced water holding capacity for agriculture purposes. The chemical structures of those were investigated by FTIR, XRD and SEM. Biochar (BC) as an active substance was physically mixed with those hydrogels at different ratios (0/100, 0.5/99.5, 1/99 and 100/0 (g/g) biochar/hydrogels). BC, PEtOx-HEMA-CS and the mixture of PEtOx-HEMA-CS-BC were mixed with saline soil at ratio 0.05 and 0.1% w/w of prepared materials/soil. Pot agriculture carrot experiments were conducted to mitigate the salinity hazards by using biochar with and without hydrogels. Findings The obtained data referred that there is a significant decrease in soil salinity and exchangeable sodium percentage and increase in organic matter, cation exchange capacity, field capacity, permanent wilting point and available water especially at (PEtOx-HEMA-CS5)0.1-BC1. The highest increment percentage of NP and K were 36.36, 70 and 72%, respectively. Also, the relative increase of carrot productivity was 49.63% at the highest rates of biochar and hydrogels. However, the highest value of water use efficiency was observed at the mixture of biochar and hydrogels at (PEtOx-HEMA-CS5)0.1-BC1. Conclusion Finally, applying biochar combined with (PEtOx-HEMA-CS5) could be recommended as a good approach to enhance carrot productivity and water use efficiency under saline soil conditions.

Viscoelastic and Properties of Amphiphilic Chitin in Plasticised Polylactic Acid/Starch Biocomposite

The enhancement of the PLA thermomechanical properties is significant due to its suitability as a replacement for primary synthetic polymer use in diverse industrial production. The amphiphilic chitin was used as a compatibilizer in PLA/starch biocomposite. The properties of plasticised polylactic acid blended with starch, and amphiphilic chitin was studied for enhanced thermomechanical and viscoelastic properties. Chitin was modified using acetylated substitution reaction and blended with plasticised PLA/starch biocomposite. The biocomposite was prepared with combined compression and melt extrusion techniques. The biocomposite’s thermomechanical, thermal, mechanical, and morphological properties were studied using dynamic mechanical analysis, TGA-DSC, tensile test, and scanning electron microscopy. The storage and loss modulus were significantly enhanced with increased amphiphilic chitin content. Similarly, the single peak of tan delta showed good miscibility of the polymeric blend. Additionally, the modulus increases with frequency change from 1 Hz to 10 Hz. The thermal stability of the biocomposite was observed to be lower than the neat PLA. The tensile properties of the biocomposite increased significantly more than the neat PLA, with P4S4C having the highest tensile strength and modulus of 87 MPa and 7600 MPa. The SEM images show good miscibility with no significant void in the fractured surface. The viscoelastic properties of PLA were enhanced considerably with plasticizer and amphiphilic chitin with improved biodegradability. The properties of the biocomposite can be adapted for various industrial applications.

Synthesis and properties of tetrazole-containing polyelectrolytes based on chitosan, starch, and arabinogalactan

The synthesis of tetrazole-containing derivatives of chitosan, starch, and arabinogalactan was carried out by a sequence of reactions including cyanoethylation of polysaccharides and subsequent azidation of cyanoethyl derivatives. The reaction of cyanoethylation of polysaccharides with acrylonitrile proceeds in the temperature range 40–60°C in the presence of NaOH. The transformation of nitrile groups into tetrazole rings (azidation) of cyanoethylated polysaccharide derivatives was carried out with a mixture of sodium azide with ammonium chloride in DMF at 105°C. The reaction with the participation of derivatives of starch and arabinogalactan is characterized by the degree of conversion of nitrile groups into tetrazole rings, which is close to the maximum. The introduction of unsubstituted tetrazole rings into the structure of polysaccharides of acidic N–H substantially changes some of their properties. Like other carbo- and hetero-chain polymers containing N–H unsubstituted tetrazole rings in the structure, tetrazolated polysaccharides exhibit the properties of acidic polyelectrolytes. Tetrazole-containing derivatives of chitosan exhibit the properties of polyampholytes. The presence of tetrazole rings in the structure of modified polysaccharides allows the reaction with epoxy compounds to yield network polymers capable of limited swelling in aqueous media with the formation of polyelectrolyte hydrogels.

Hydrophobic Chitosan Nanoparticles Loaded with Carvacrol against Pseudomonas aeruginosa Biofilms

Pseudomonas aeruginosa infections have become more challenging to treat and eradicate due to their ability to form biofilms. This study aimed to produce hydrophobic nanoparticles by grafting 11-carbon and three-carbon alkyl chains to a chitosan polymer as a platform to carry and deliver carvacrol for improving its antibacterial and antibiofilm properties. Carvacrol–chitosan nanoparticles showed ζ potential values of 10.5–14.4 mV, a size of 140.3–166.6 nm, and an encapsulation efficiency of 25.1–68.8%. Hydrophobic nanoparticles reduced 46–53% of the biomass and viable cells (7–25%) within P. aeruginosa biofilms. Diffusion of nanoparticles through the bacterial biofilm showed a higher penetration of nanoparticles created with 11-carbon chain chitosan than those formulated with unmodified chitosan. The interaction of nanoparticles with a 50:50 w/w phospholipid mixture at the air–water interface was studied, and values suggested that viscoelasticity and fluidity properties were modified. The modified nanoparticles significantly reduced viable P. aeruginosa in biofilms (0.078–2.0 log CFU·cm⁻²) and swarming motility (40–60%). Furthermore, the formulated nanoparticles reduced the quorum sensing in Chromobacterium violaceum. This study revealed that modifying the chitosan polarity to synthesize more hydrophobic nanoparticles could be an effective treatment against P. aeruginosa biofilms to decrease its virulence and pathogenicity, mainly by increasing their ability to interact with the membrane phospholipids and penetrate preformed biofilms.

Molecular interaction mechanisms of glycol chitosan self-healing hydrogel as a drug delivery system for gemcitabine and doxorubicin

Glycol chitosan is a derivative of chitosan that has attracted attention in recent years due to its biocompatibility and biodegradability. Due to its unique biological characteristics, it has been widely used in hydrogels and biomaterials. In this study, we explored the loading efficiency of a self-healing hydrogel (GC-DP) comprising glycol chitosan (GC) and telechelic difunctional poly(ethylene glycol) (DF-PEG) for delivering the anticancer drugs gemcitabine and doxorubicin through full atomistic simulations. We also constructed full atomistic models of the two drug delivery systems at three drug concentrations of 10%, 40%, and 80% to understand how the drug concentration affects the loading efficiency and molecular structure of the GC-DP hydrogels. Through the analysis of the results, we show that the GC-DP hydrogel exhibits excellent loading efficiency for both gemcitabine and doxorubicin at all drug concentrations (10%, 40% and 80%). Our results reveal that the main mechanism of interaction between the GC-DP hydrogels and gemcitabine is van der Waals adsorption and that the dominant interactions between the GC-DP hydrogel and doxorubicin are hydrogen bonds for the D10 model and van der Waals adsorption for the D40 and D80 models. Our results provide molecular insights into how drug molecules are carried by hydrogel materials and indicate that the GC-DP hydrogel is a promising candidate for carrying both gemcitabine and doxorubicin, and thus serving as a novel drug carrier for cancer treatment.

High antibacterial performance of hydrophobic chitosan-based nanoparticles loaded with Carvacrol

Bacterial infections have become one of the top ten public health concerns worldwide. These problems are aggravated with the emergence of multi-drug resistant bacterial strains. Thus, it is necessary to adopt novel technological strategies, such as development of bionanomaterials to prevent the infection, and treat this kind of bacteria. At this regard, the chemical modification of chitosan (Cs), by the covalent attachment of a hydrocarbon chain (octanoic acid), was developed to obtain hydrophobic chitosan (HCs). Then, HCs was used to synthetize nanoparticles using the well-known ionotropic gelation approach, optimizing the parameters, such as the TPP/HCs ratio and pH solution to get stable nanoparticles. Then, carvacrol (CAR) was loaded into NPs (HCs-CAR NPs) using different concentrations of 25%, 50% and 75% (%w/w CAR/HCs). The physicochemical properties for HCs-CAR NPs prepared at 50% of CAR stood out from the rest, showing a spherical morphology, with a size of 200 nm, Z potential of 10.4 mV and encapsulation efficiency of 56.28%. These formulations were chosen to evaluate the antibacterial activity, using Gram-negative (Escherichia coli) and Gram-positive bacterial model (Staphylococcus aureus). The HCs-CAR NPs showed great activity against both bacterial models, being more effective against Gram (+) strain (S. aureus), suggesting the potential application of these NPs as novel biomaterial to treat bacterial infection.

Supercritical Carbon Dioxide Isolation of Cellulose Nanofibre and Enhancement Properties in Biopolymer Composites

The physical properties, such as the fibre dimension and crystallinity, of cellulose nanofibre (CNF) are significant to its functional reinforcement ability in composites. This study used supercritical carbon dioxide as a fibre bundle defibrillation pretreatment for the isolation of CNF from bamboo, in order to enhance its physical properties. The isolated CNF was characterised through zeta potential, TEM, XRD, and FT-IR analysis. Commercial CNF was used as a reference to evaluate the effectiveness of the method. The physical, mechanical, thermal, and wettability properties of the bamboo and commercial CNF-reinforced PLA/chitin were also analysed. The TEM and FT-IR results showed the successful isolation of CNF from bamboo using this method, with good colloidal stability shown by the zeta potential results. The properties of the isolated bamboo CNF were similar to the commercial type. However, the fibre diameter distribution and the crystallinity index significantly differed between the bamboo and the commercial CNF. The bamboo CNF had a smaller fibre size and a higher crystallinity index than the commercial CNF. The results from the CNF-reinforced biocomposite showed that the physical, mechanical, thermal, and wettability properties were significantly different due to the variations in their fibre sizes and crystallinity indices. The properties of bamboo CNF biocomposites were significantly better than those of commercial CNF biocomposites. This indicates that the physical properties (fibre size and crystallinity) of an isolated CNF significantly affect its reinforcement ability in biocomposites. The physical properties of isolated CNFs are partly dependent on their source and production method, among other factors. These composites can be used for various industrial applications, including packaging.

Bovine serum albumin/chitosan-nanoparticle bio-complex; spectroscopic study and in vivo toxicological - Hypersensitivity evaluation

This study, investigates the interaction of bovine serum albumin (BSA) with synthesized chitosan nanoparticles (CSNPs) using steady-state fluorescence and UV-vis absorbance spectroscopy as well as picosecond time-resolved fluorescence technique. The fluorescence quenching mechanism of BSA by CSNPs indicates the presence of both static and dynamic mechanism. The loading efficiency of BSA-CSNPs exhibited a decrease by about 6% in neutral pH under physiological temperature. Transmission electron microcopy (TEM) images revealed the Synthesized CSNPs were irregular in shape with size of ~42 nm. The safety and biocompatibility of BSA-CSNPs inside the body was investigated after intraperitoneal (IP) injection of male mice for nine days, analysis of in vivo results, revealed no toxicity with a hypocholesterolemic effect and a predicted mild activation of WBCs due to CSNPs adjuvant and immunogenic peptides in BSA. Accordingly, no signs of hypersensitivity were observed due to the administration of such formulations. The results can be used for a better understanding the interaction of CSNPs within biological protein environment.

Antibacterial Activity of N,O-Acylated Chitosan Derivative

The antibacterial activity of N,O-acylated chitosan derivative with linoleic acid (CH_LA) was tested by disc and well diffusion, agar impregnation and microdilution methods against Staphylococcus aureus, Escherichia coli and Helicobacter pylori strains. Hydrophobically modified chitosan (HMC) was expected to exhibit enhanced antibacterial activity and specific mucin interactions. Although diffusion tests have not indicated the antibacterial potential of chitosan (CH) or CH_LA, the results of the microdilution method demonstrated that tested polymers significantly reduced the amount of living bacteria cells in different concentrations depending on the microorganism. Additionally, CH_LA was characterized by enhanced antibacterial activity compared to CH, which may suggest a different mechanism of interaction with S. aureus and H. pylori. Furthermore, the UV-VIS analysis revealed that the amphiphilic character of derivative led to strong CH_LA–mucin interactions. The study proved the high potential of CH_LA in antibacterial applications, especially for the gastrointestinal tract.

Self-Assembled Amphiphilic Starch Based Drug Delivery Platform: Synthesis, Preparation, and Interactions with Biological Barriers

Core-shell structured nanoparticles (NPs) render the simultaneous coloading capacity of both hydrophobic and hydrophilic drugs and may eventually enhance therapeutic efficacy. In this study, we employed a facile squalenoylation technology to synthesize a new amphiphilic starch derivative from partially oxidized starch, which self-assembled into core-shell starch NPs (StNPs) only at a squalenyl degree of substitution (DoS) of ∼1%. The StNPs characteristics could be tuned as the functions of the polymer molecular weight, DoS, and NPs concentration. The biopharmaceutical features of the StNPs, including colloidal stability, carrier properties, and biocompatibility, were carefully investigated. The interaction study between StNPs and mucin glycoproteins, the main organic component of mucus, revealed a moderate mucin interacting profile. Furthermore, the StNPs also showed good penetration through Pseudomonas aeruginosa biofilms. These results nominate StNPs as a versatile drug delivery platform with potential applications for mucosal drug delivery and the treatment of persistent infections.

A multiscale coarse-grained model to predict the molecular architecture and drug transport properties of modified chitosan hydrogels

Hydrogels constructed with functionalized polysaccharides are of interest in a multitude of applications, chiefly the design of therapeutic and regenerative formulations. Tailoring the chemical modification of polysaccharide-based hydrogels to achieve specific drug release properties involves the optimization of many tunable parameters, including (i) the type, degree (χ), and pattern of the functional groups, (ii) the water-polymer ratio, and (iii) the drug payload. To guide the design of modified polysaccharide hydrogels for drug release, we have developed a computational toolbox that predicts the structure and physicochemical properties of acylated chitosan chains, and their impact on the transport of drug molecules. Herein, we present a multiscale coarse-grained model to investigate the structure of networks of chitosan chains modified with acetyl, butanoyl, or heptanoyl moieties, as well as the diffusion of drugs doxorubicin (Dox) and gemcitabine (Gem) through the resulting networks. The model predicts the formation of different network structures, in particular the hydrophobically-driven transition from a uniform to a cluster/channel morphology and the formation of fibers of chitin chains. The model also describes the impact of structural and physicochemical properties on drug transport, which was confirmed experimentally by measuring Dox and Gem diffusion through an ensemble of modified chitosan hydrogels.

Cu(II) and As(V) Adsorption Kinetic Characteristic of the Multifunctional Amino Groups in Chitosan

Amino groups in the chitosan polymer play as a functional group for the removal of cations and anions depending on the degree of protonation, which is determined by the solution pH. A hydrogel beadlike porous adsorbent was used to investigate the functions and adsorption mechanism of the amino groups by removal of Cu(II) as a cation and As(V) as an anion for a single and mixed solution. The uptakes of Cu(II) and As(V) were 5.2 and 5.6 μmol/g for the single solution and 5.9 and 3.6 μmol/g for the mixed solution, respectively. The increased total capacity in the presence of both the cation and anion indicated that the amino group (NH2 or NH3+) species was directly associated for adsorption. The application of a pseudo second-order (PSO) kinetic model was more suitable and resulted in an accurate correlation coefficient (R2) compared with the pseudo first-order (PFO) kinetic model for all experimental conditions. Due to poor linearization of the PFO reaction model, we attempted to divide it into two sections to improve the accuracy. Regardless of the model equation, the order of the rate constant was in the order of As(V)-single > Cu(II)-single > As(V)-mixed > Cu(II)-mixed. Also, the corresponding single solution and As(V) showed a higher adsorption rate. According to intraparticle and film diffusion applications displaying two linear lines and none passing through zero, the rate controlling step in the chitosan hydrogel bead was determined by both intraparticle and film diffusion.

Review on Polysaccharides Used in Coatings for Food Packaging Papers

Paper and board show many advantages as packaging materials, but the current technologies employed to obtain adequate barrier properties for food packaging use synthetic polymers coating and lamination with plastic or aluminium foils—treatments which have a negative impact on packaging sustainability, poor recyclability and lack of biodegradability. Recently, biopolymers have attracted increased attention as paper coatings, which can provide new combinations in composite formulas to meet the requirements of food packaging. The number of studies on biopolymers for developing barrier properties of packaging materials is increasing, but only a few of them are addressed to food packaging paper. Polysaccharides are viewed as the main candidates to substitute oil-based polymers in food paper coating, due to their film forming ability, good affinity for paper substrate, appropriate barrier to gases and aroma, and positive effect on mechanical strength. Additionally, these biopolymers are biodegradable, non-toxic and act as a matrix for incorporation additives with specific functionalities for coated paper (i.e., active-antimicrobial properties). This paper presents an overview on the availability and application of polysaccharides from vegetal and marine biomass in coatings for foods packaging paper. The extraction methods, chemical modification and combination routes of these biopolymers in coatings for paper packaging are discussed.

Diminishing Cohesion of Chitosan Films in Acidic Solution by Multivalent Metal Cations

Chitosan is a natural polymer with good biocompatibility, biodegradability, and bioactivity that has great potential for biomedical and industrial applications. Like other natural sugar-based polymers, chitosan molecules own versatile adhesion abilities to bind with various surfaces, owing to multiple functional moieties contained in the chain. To develop the promising biomaterials based on the chitosan chemistry, it is fundamentally important to figure out its adhesion mechanism under a certain condition, which leaves us numbers of open questions. In this work, we characterized the chitosan films adsorbed on a mica substrate in acidic solution and investigated the effects of multivalent salts on the cohesive behaviors of the films by means of the surface forces apparatus. The results showed that the cohesion capacities of chitosan films were reduced to around 30% of their original states after the addition of 10^-7 M LaCl₃ into 150 mM acetic acid, which could be partially recovered by holding the films at the contact position for a longer time. Surprisingly, the cohesion loss in the films exhibited the dependence on the properties of the metal cations including valance and concentration. The topography of the chitosan-coated surface also showed obvious aggregation in the presence of submicromolar of the salts. Here, we attributed these phenomena regarding cohesion loss to the mechanisms involved in the absorption of metal cations by the chitosan chains, which not only consumed the binding sites but also induced conformation change in the polymer network. Our findings may offer a suggestion for the production of chitosan-based materials to notice the potential impacts of ultralow concentrated salts that are usually neglected even under acidic conditions.

Tailoring the Chemical Modification of Chitosan Hydrogels to Fine-Tune the Release of a Synergistic Combination of Chemotherapeutics

Combination chemotherapy with a defined ratio and sequence of drug release is a clinically established and effective route to treat advanced solid tumors. In this context, a growing body of literature demonstrates the potential of hydrogels constructed with chemically modified polysaccharides as depots for controlled release of chemotherapeutics. Identifying the appropriate modification in terms of physicochemical properties of the functional group and its degree of substitution (χ) to achieve the desired release profile for multiple drugs is, however, a complex multivariate problem. To address this issue, we have developed a computational toolbox that models the migration of a drug pair through a hydrated network of polysaccharide chains modified with hydrophobic moieties. In this study, we chose doxorubicin (DOX) and Gemcitabine (GEM) as model drugs, as their synergistic effect against breast cancer has been thoroughly investigated, and chitosan as the model polymer. Our model describes how the modification of chitosan chains with acetyl, butanoyl, and heptanoyl moieties at different values χ governs both the structure of the hydrogel network and drug migration through it. Our experimental data confirm the in silico predictions for both single- and dual-drug release and, most notably, the counterintuitive inversion of release vs χ that occurs when switching from a single- to a dual-drug system. Consensus between predicted and experimental data indicates that acetyl modifications (χ = 32-42%) and butanoyl modifications (χ = 19-24%) provide synergistic GEM/DOX release molar ratios (i.e., 5-10). Collectively, these results demonstrate the potential of this model in guiding the design of chemotherapeutic hydrogels to combat cancer.

A functionalized nano-structured cellulosic sorbent aerogel for oil spill cleanup: Synthesis and characterization

A new synthesis strategy was adopted to convert cellulose to a biodegradable sorbent with properties of very high oil absorption and retention capacities, excellent oil-water selectivity, good mechanical strength and recycling ability. The sorbent in form of a hydrophobic/oleophilic nano-structured aerogel was prepared through functionalizing cotton cellulose with low surface energy moieties followed by dissolving and chemically cross-linking the product in an organic medium (DMSO), and freeze-drying. High absorption capacities of 40.7, 57.1, and 47.3 g/g were achieved for three different light crude oils at 25 °C which is comparable with most synthetic oil sorbents. Washburn's model was utilized to describe the wicking dynamics and fluid flow through the pores and to evaluate the effects of all important factors on the sorption process. Via comparing the experimental data with the predictions made by the model, it was revealed that unlike other cellulose-based oil sorbents reported in the literature, the swelling of fibrous network in the synthesized aerogel plays an important role in the absorption process besides the capillary pressure, resulting in a very good oil retention capacity and at the same time lowering the absorption rate, especially for viscose organic liquids.

Optimization of Photosensitized Tryptophan Oxidation in the Presence of Dimegin-Polyvinylpyrrolidone-Chitosan Systems

By the example of a model process of tryptophan photooxidation in the aqueous medium in the presence of a three-component photosensitizing complex (porphyrin photosensitizer-polyvinylpyrrolidone- chitosan, PPS-PVP-CT) in the temperature range of 20-40 °С, we have demonstrated a possibility of modification of such a process by selecting different molar ratios of the components in the reaction mixture. The actual objective of this selection is the formation of a certain PPS-PVP-CT composition in which PVP macromolecules would coordinate with PPS molecules and at the same time practically block the complex binding of PPS molecules with chitosan macromolecules. Such blocking allows utilization of the bactericidal properties of chitosan to a greater extent, since chitosan is known to depress the PPS photosensitizing activity in PPS-PVP-CT complexes when using those in photodynamic therapy (PDT). The optimal composition of photosensitizing complexes appears to be dependent on the temperature at which the PDT sessions are performed. We have analyzed the correlations of the effective rate constants of tryptophan photooxidation with the photophysical characteristics of the formed complexes.

Water-Based Suspensions of Iron Oxide Nanoparticles with Electrostatic or Steric Stabilization by Chitosan: Fabrication, Characterization and Biocompatibility

Present day biomedical applications, including magnetic biosensing, demand better understanding of the interactions between living systems and magnetic nanoparticles (MNPs). In this work spherical MNPs of maghemite were obtained by a highly productive laser target evaporation technique. XRD analysis confirmed the inverse spinel structure of the MNPs (space group Fd-3m). The ensemble obeyed a lognormal size distribution with the median value 26.8 nm and dispersion 0.362. Stabilized water-based suspensions were fabricated using electrostatic or steric stabilization by the natural polymer chitosan. The encapsulation of the MNPs by chitosan makes them resistant to the unfavorable factors for colloidal stability typically present in physiological conditions such as pH and high ionic force. Controlled amounts of suspensions were used for in vitro experiments with human blood mononuclear leukocytes (HBMLs) in order to study their morphofunctional response. For sake of comparison the results obtained in the present study were analyzed together with our previous results of the study of similar suspensions with human mesenchymal stem cells. Suspensions with and without chitosan enhanced the secretion of cytokines by a 24-h culture of HBMLs compared to a control without MNPs. At a dose of 2.3, the MTD of chitosan promotes the stimulating effect of MNPs on cells. In the dose range of MNPs 10-1000 MTD, chitosan "inhibits" cellular secretory activity compared to MNPs without chitosan. Both suspensions did not caused cell death by necrosis, hence, the secretion of cytokines is due to the enhancement of the functional activity of HBMLs. Increased accumulation of MNP with chitosan in the cell fraction at 100 MTD for 24 h exposure, may be due to fixation of chitosan on the outer membrane of HBMLs. The discussed results can be used for an addressed design of cell delivery/removal incorporating multiple activities because of cell capability to avoid phagocytosis by immune cells. They are also promising for the field of biosensor development for the detection of magnetic labels.

Preparation of Chitosan/Poly‐γ‐Glutamic Acid Polyelectrolyte Multilayers on Biomedical Metals for Local Antibiotic Delivery

Polyelectrolyte multilayer assembly is one of the most widely applied biomaterial coatings for applications from surface modification, drug delivery, tissue engineering to biomimetic extracellular environment. In this research, we propose a simple layer-wise spin coating technique to prepare chitosan/poly-γ-glutamic acid (C/PGA) polyelectrolyte multilayers (PEMs) on two different biomedical metals, 316L stainless steel (316LSS) and titanium alloy (Ti6Al4V). The multilayer coating was fabricated using oppositely charged chitosan and poly--glutamic acid to deposit a total of 10, 20, or 30 multilayered films. Afterward, tetracycline was loaded by soaking the coated metals for 12 hours. The microstructure, mechanical properties, biocompatibility and drug release rate were investigated by scanning electron microscopy, contact angle measurement, MG63 cell viability and inhibition of Escherichia coli (E. coli) growth. Lastly, MG63 cell attachment was detected by fluorescence microscopy after staining with Hoechst 33258. This coating technique can prepare a layer of 2.2–6.9 m C/PGA PEMs favoring cell attachment and growth. Moreover, tetracycline was released from C/PGA PEMs and inhibited the growth of E. coli. The results suggest that C/PGA PEMs provide a useful platform for modulating the micro-environment for better cell adhesion and antibiotic delivery, which hold great potential for surface modification and drug loading for biomimetic materials.

Gladius and its derivatives as potential biosorbents for marine diesel oil

The demand for low cost and effective materials to remove contaminants such as residues of oil spills has encouraged studies on new biosorbents produced from wastes. Considering the overgeneration of fishing residues and the necessity to provide an alternative purpose for such materials, this study aimed to evaluate squid gladius and its derivatives (β-chitin and chitosan) as sorbents to remove marine diesel oil (MDO) from fresh and artificial seawater. It was also executed an attempted to improve their performances through a high-intensity ultrasound treatment (UT-gladius and UT-β-chitin). All sorbents removed MDO at both salinities. Contact surface area, salinity, and water retention seemed to play a key role in the outcomes. UT-β-chitin's performance was significantly superior to β-chitin's and chitosan's in MDO removal at salinity 0, as well as at salinity 30, where gladius and UT-gladius also excelled. Ultrasound treatment improved the oil removal performance of UT-β-chitin by increasing its contact surface area. This is the first report on the efficiency of gladius and UT-β-chitin for such purpose, and brought up huge possibilities and new questions that can lead to the achievement of biosorbents of great efficiency.

Nano-Encapsulation of Bilirubin in Pluronic F127-Chitosan Improves Uptake in β Cells and Increases Islet Viability and Function after Hypoxic Stress

Pancreatic islet transplantation is the only curative, noninvasive treatment for type 1 diabetes mellitus; however, high rates of cell death in the immediate postimplantation period have limited the success of this procedure. Bilirubin, an endogenous antioxidant, can improve the survival of murine pancreatic allografts during hypoxic stress but has poor solubility in aqueous solutions. We hypothesized that nano-encapsulation of bilirubin in pluronic 127-chitosan nanoparticle bilirubin (nBR) would improve uptake by murine pancreatic islet cells and improve their viability following hypoxic stress. Nano-bilirubin was synthesized, and drug release characteristics were studied in vitro. Cellular uptake of nBR was compared to free bilirubin (fBR) in an insulinoma cell line (INS-R3) model using confocal-like structured illumination microscopy. Next, C57BL/6 mouse islets were treated with concentrations of 0 to 20 μM of nBR, fBR, or empty nanoparticle (eNP), prior to incubation under standard or hypoxic conditions. Islet viability and function were compared between treatment groups. Release of bilirubin was greatest from nBR suspended in protein-rich solution. Increased, selective uptake of nBR by INS-R3 cells was demonstrated. Cell death after hypoxic stress was significantly decreased in murine islets treated with 5 μM nBR (18.5% ± 14.1) compared to untreated islets (33.5% ± 17.5%; P = 0.019), with reduction in central necrosis. Treatment group had a significant effect on glucose stimulation index [SI], ( P = 0.0137) and islets treated with 5 μM nBR had the highest SI overall. Delivery of bilirubin using pluronic F127-chitosan NP improves uptake by murine islets compared to fBR and offers dose-dependent protective effects following hypoxic stress.