Chitosan Thin Films Research Articles

High-Power Laser Deposition of Chitosan Polymers: Medical and Environmental Applications.

High-power laser irradiation interaction with natural polymers in biocomposites and Laser-Induced Chitin Deacetylation (LICD) was studied in this work, in order to produce thin films consisting of chitosan composite. The new method can lead to a cutting-edge technology, as a response to the concern regarding the accumulation of “natural biological waste” and its use. The process consists of high-power laser irradiation applied on oyster shells as the target and deposition of the ablated material on different substrates. The obtained thin films we analyzed by FTIR, UV-VIS and LIF spectroscopy, as well as SEM-EDS and AFM. All the results indicated that chitin was extracted from the shell composite material and converted to chitosan by deacetylation. It was, thus, evidenced that chemical transformation in the chitin polymer side-chain occurs during laser irradiation of the oyster shell and in the resulted plasma plume of ablation. The numerical simulation in COMSOL performed for this study anticipates and confirms the experimental results of chitin deacetylation, also providing information about the conditions required for the physico-chemical processes involved. The high sorption properties of the thin films obtained by a LICD procedure is evidenced in the study. This quality suggests that they should be used in transdermal patch construction due to the known hemostatic and antibacterial effects of chitosan. The resulting composite materials, consisting of the chitosan thin films deposited on hemp fabric, are also suitable for micro-filters in water decontamination or in other filtering processes.

Surface Properties of Plasma-Activated Chitosan Foils

Thin films of chitosan are often deposited on various surfaces to provide them with antiseptic properties. In the presented research, chitosan foils were obtained using two methods and treated with nitrogen plasma. The obtained materials were characterized by measuring the wettability of the test liquids, and the apparent surface free energy was calculated using the Tadmor equilibrium contact angles. The surface topography was characterized using optical profilometry and SEM. On the other hand, the effect of plasma on surface groups was investigated using the FTIR-ATR technique. Plasma activation of the surface increases the polarity of the surface. This is observed in the changed surface roughness and the share of functional groups on the surface.

Solid Phase Peptide Synthesis on Chitosan Thin Films.

Stable chitosan thin films can be promising substrates for creating nanometric peptide-bound polyglucosamine layers. Those are of scientific interest since they can have certain structural similarities to bacterial peptidoglycans. Such films were deposited by spin coating from chitosan solutions and modified by acetylation and N-protected amino acids. The masses of deposited materials and their stability in aqueous solutions at different pH values and water interaction were determined with a quartz crystal microbalance with dissipation (QCM-D). The evolution of the surface composition was followed by X-ray photoelectron (XPS) and attenuated total reflectance infrared (ATR-IR) spectroscopy. Morphological changes were measured by atomic force microscopy (AFM), while the surface wettability was monitored by by static water contact angle measurements. The combination of the characterization techniques enabled an insight into the surface chemistry for each treatment step and confirmed the acetylation and coupling of N-protected glycine peptides. The developed procedures are seen as first steps toward preparing thin layers of acetylated chitin, potentially imitating the nanometric peptide substituted glycan layers found in bacterial cell walls.

Modulation of Optical Anisotropy in Chitosan Thin Films: Role of Swelling

Modulation of Optical Anisotropy in Chitosan Thin Films: Role of Swelling

Penetrant-Induced Glass-like Transition in Thin Chitosan Films.

We present the water vapor-induced swelling and the emergence of a penetrant-induced glass-like transition in the substrate-supported glassy chitosan thin films. The time evolution of the film thickness under different levels of relative humidity conditions is measured in real-time using a spectroscopic ellipsometer equipped with a humidity cell. In a dry film, the network of chitosan chains is in a glassy state, and upon exposure to water vapor, initially, the film swells by Fickian diffusion of water molecules, which triggers the structural relaxations of the chains. Under higher humidity conditions, a relatively slower evolution of thickness succeeds the initial rapid swelling due to the non-Fickian sorption of water molecules. The swelling characteristics of the polymer films are accounted for by considering the diffusion-relaxation mechanism of chains in the presence of smaller penetrant molecules. The penetrant-induced glass-like transition (Pg), where the polymer film isothermally transits from a glassy to a rubbery state, is determined for pristine and cross-linked chitosan films. Pg is determined from the abrupt change in the rate of swelling observed upon increasing the relative humidity. Chemical crosslinking has an evident influence on the penetrant-induced glass-like transition of the chitosan films. Pg was found to rise sharply for stiffer films with higher cross-linking density.

Feasibility of chitosan thin film and hybrid chitosan/silica thin film for the mitigation of toxic Alexandrium minutum

Harmful Algal Bloom (HAB) has been a growing issue worldwide for the past few decades, posing harm to aquatic ecosystems and drinking water quality. Therefore, this research aims to investigate the feasibility of a chitosan thin film and hybrid chitosan/silica thin film prepared via a one-pot synthesis method to mitigate toxic algae cells, Alexandrium minutum. The film-forming solution was synthesised by stirring chitosan and sodium silicate solutions obtained from rice husk ash (RHA). The films were neutralised with NaOH and distilled water and finally dried at room temperature. The thin films were characterised using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM). The SEM analysis indicates that the new thin film’s surface was smooth compared to the used thin films. The mitigation of A. minutum was carried out for 72 h. The chitosan film achieved 18.1 % removal of A. minutum at 72 h, whereas 23.8% of the algae was removed when the hybrid chitosan/silica thin film was used. Digital microscopic imaging showed that the algae cells were adsorbed on the chitosan film’s surface ruptured, whereas the adsorbed cells on the hybrid films were preserved. The ATR-FTIR analysis of the used film indicates the presence of the algae cells, which changes the functional group of the film. The film can be separated easily from the seawater and exhibit good biodegradable properties as it degrades after being buried in the soil for one month.

Biosynthesis of thin film derived from microbial chitosan for piezoelectric application

The aim of this paper was to synthesize and characterize microbial chitosan thin films for potential piezoelectric application. Microbial chitosan was derived from the Aspergillus oryzae fungus via extraction and deacetylation. Chitosan thin film was characterized for its surface morphology, chemical properties, tensile strength, and surface topography. For the potential application of chitosan as a piezoelectric material, its piezoelectric characteristics were presented in terms of its electromechanical coupling coefficient and piezoelectric coefficient. The fabrication of the chitosan thin films was optimized via the one-factor-at-a-time (OFAT) method, where the parameters were type of acid solvent, acid concentration and mixing time. The chitosan film prepared using formic acid at a concentration of 0.25 M for 3 h of mixing time had the highest tensile strength (129.29 MPa), electromechanical coupling factor (0.0045), and piezoelectric coefficient d31 (10 pC/N). The results obtained, from the optimized fabrication of the chitosan thin film, were validated against fungal chitosan, and it was shown that the properties of the thin film were comparable to those of commercial PVDF thin films. Therefore, the prospect of using microbial chitosan thin film as wearable piezoelectric energy harvester or nano-generator is promising.

Facile fabrication and nanoscale assembly of polydopamine-functionalized, flexible chitosan films

Substrates that are simultaneously thin, strong, optically transparent, and biocompatible have diverse applications in a range of fundamental and applied fields. While nature-derived materials offer advantages of sustainability and inherent biocompatibility compared to synthetic polymers, their brittleness and swelling, as well as surface charge and chemical functionalization non-conducive to cell growth, can hinder widespread application. In this work, we discuss the fabrication and systematic characterization of polydopamine-coated chitosan thin films. Chitosan is a widely used, partially deacetylated form of chitin, derived from crustaceans and arthropods. Polydopamine (PDA) is derived from chemistries mimicking mussel foot adhesive proteins. A facile dip-coating process of thin and flexible, uncrosslinked chitosan films in aqueous dopamine solutions leads to dramatic changes in physical and chemical properties. We show how the PDA forms time-dependent assemblies on the film surfaces, affecting surface roughness, hydrophilicity, and mechanical strength. Coating the surface for even a few seconds provides functional changes to the films. Our results shows that the optimal coating time is on the order of few hours, whereby the films are optically transparent with excellent extensibility and Young’s modulus, while further coating reduces the benefits of this surface coating. These materials are biocompatible, serving as substrates for cell adhesion and growth while maintaining good viability. Overall, these findings give insight to the effects of PDA assembly on surfaces, and illustrate how a simple, quick, and robust bioinspired coating process can prime substrates for biomedical applications such as tissue engineering, biosensing, and wound healing.

Preparation and Characterization of PVDF/g-C3N4/Chitosan Polymeric Membrane for the Removal of Direct Blue 14 Dye

Polyvinylidene fluoride (PVDF)/g-C3N4/Chitosan thin film membranes were prepared by immersing of PVDF/g-C3N4 membrane in solution containing various concentrations of chitosan for removal of Direct Blue 14 dye (an anionic dye) from aqueous solutions. The resulting membranes were characterized by XRD, FESEM, TEM and AFM. Also, pure water flux, salt rejection, water content and antifouling properties of prepared membranes were investigated. The resulting demonstrate that pure water flux was decreased (from 70.98 to 14.7%) by increasing of chitosan concentration (2–4%), while water content (42.5–94.78%), salt rejection (from 62.66 to 88.98%) and antifouling properties were increased. It is found that chitosan has major impact on the membrane structural properties due to transform of the PVDF membrane into hydrophilic ones. It is reported that maximum 93% rejection of Direct Blue 14 was obtained by PCC3 (PVDF/g-C3N4-chitosan 4% w/v) membrane. Compared to the PVDF/g-C3N4 membrane, the experimental results showed that PVDF/g-C3N4/Chitosan membranes demonstrated high potential mainly due to greater hydrophilicity and further minimizing membrane fouling.

Essential oils-loaded electrospun chitosan-poly(vinyl alcohol) nonwovens laminated on chitosan film as bilayer bioactive edible films

Direct application of active and volatile compounds of essential oils (EOs) is ineffective in food and uncontrolled release of these compounds may be undesirable from sensory and antimicrobial efficacy standpoints. The present study aimed to develop and characterize the physical and antimicrobial properties of casting composite chitosan (CS) thin films laminated with electrospun nonwovens loaded with Zataria multiflora (ZEO) and cinnamon (CEO) targeting for active food packaging purposes. The composite structures were incorporated with various amounts of ZEO and CEO blend to enhance their antimicrobial and physical properties. There was no significant difference between antibacterial activity of the films containing EOs in both Gram-positive and Gram-negative bacteria (P˂0.05). All the films had antifungal activity against A.flavus. The highest antioxidant activity was found in the composite CS film (97.20%) in comparison to other films (P˂0.05). Morphological analysis of bilayer films revealed homogeneous bead-free electrospun nanofibers with diameters of less than 200 nm. The addition of 0.5 %v/v CEO significantly enhanced the elongation in comparison to CS film (P˂0.05). Our results demonstrated that the properties of bilayer films were influenced by the contents of EOs and these findings may pave a way for introducing new category of active packaging staffs.

Effect of chitosan dissolved in different acetic acid concentration towards VOC sensing performance of quartz crystal microbalance overlay with chitosan

Improvement in sensing layer properties of quartz crystal microbalance (QCM) sensors are crucial in developing gas sensors with high sensitivity and selectivity. In this work, we study the use of chitosan thin film as the sensing layer on a QCM sensor to identify the presence of volatile organic compounds specifically isopropyl alcohol (IPA). The effect of chitosan dissolved in different acetic acid concentrations towards QCM overlay with chitosan sensing performance were studied. Characterization work on chitosan thin film at different acetic acid concentrations (1.0, 1.5, 2.0, 2.5% (v/v)) were performed by using FTIR and FESEM. Higher acid concentration led to a higher degree of protonation which results in a more progressive solubilization of chitosan and promotes smoother film. For chitosan layer dissolved in 2% acetic acid, the highest resonance frequency shift (99.3 Hz) was observed during the adsorption of the analyte gas molecules on QCM sensors. This can be explained by the increase in chitosan solubility and protonation. This indicates that difference acid concentration in chitosan dissolution affects the sensing performance during the presence of the analyte gas.

Intermolecular interactions of chitosan: Degree of acetylation and molecular weight

The degree of acetylation (DA), which determines as the molar proportion of N-acetyl-D-glucosamine units on chitosan, characterizes the physical, chemical, and biological properties of chitosan. Thus, DA can be a critical factor in the utilization of chitosan. Nevertheless, quantitative studies on the molecular interactions of chitosan as a function of DA are lacking. Here, we directly measured the molecular interaction (adhesion and cohesion) of molecularly thin chitosan films, dependent on the molecular weight and DA, using a surface forces apparatus. Using low molecular weight (LMW, ∼5 kDa) and high molecular weight (HMW, ∼135 kDa) chitosan, we obtained several DA ranges through a reacetylation method. The interactions of LMW chitosan were greatly influenced by the intrinsic charge of the chitosan units, whereas for HMW chitosan, chain flexibility was found to be the major factor affecting molecular interaction Taken together, our comprehensive data provides a holistic understanding of the interaction mechanism of chitosan.

On thermal and optical sensor applications of chitosan molecule in the Co/Chitosan/p-Si hybrid heterojunction design

Co/Chitosan/p-Si/Al and Co/p-Si devices were made and barrier height and ideality factor values of both devices were determined at room temperature (dark conditions). After the chitosan interlayer was found to improve the device, the thermal and photosensivity properties of the Co/Chitosan/p-Si/Al device were investigated in detail. The current–voltage measurements of Co/Chitosan/p-Si/Al heterojunction were performed in temperature range of 100–460 K and illumination intensity range of 100–400 mW/cm2. It was seen that the device parameters such as barrier height, ideality factor, series resistance and interface states density were strongly dependent on temperature. Furthermore, the capacitance–voltage (C–V) characteristics of the device were investigated at various frequencies at room temperature. The responsivity (R), detectivity (D*) and rectification ratio (RR) values of the Co/Chitosan/p-Si/Al heterojunction were found to be as a function of illumination intensity. The experimental results show that the fabricated device with chitosan thin film interlayer can be used in various optoelectronic applications, especially applications in low temperature switching devices, energy generation, photodiode and photodetector.

Effect of TiO2 nanoparticles on the structural configurations and thermal, mechanical, and optical properties of chitosan/TiO2 nanoparticle composites

The solution casting method was used to prepare nanocomposite films of chitosan/TiO2 nanoparticles (NPs) because of their applications in various fields. The effects of TiO2NP concentration on the structural, morphological, thermal, mechanical, and optical properties of such films were studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, and thermal analysis (thermogravimetric analysis [TGA] and differential scanning calorimetry [DSC]). The XRD patterns reveal miscibility between the amorphous components of chitosan and TiO2NPs. The HRTEM and FESEM images illustrate the distribution and dispersion of TiO2NPs on the film surface. Data from FTIR spectroscopy, DSC, and TGA and the mechanical properties indicate the dependence of chitosan properties on the presence of TiO2NPs and the existence of interactions between chitosan and TiO2NPs. The reflectance and transmittance values obtained were used to calculate the CIE tristimulus values, color parameters, refractive index, absorption coefficient, dielectric spectra, optical conductivity, volume energy loss function (VELF), and surface energy loss function (SELF). The dependence of the absorption coefficient on the photon energy demonstrated that the optical transfer is permissible and direct. The variations of the dielectric spectra and optical conductivity indicate different interactions between photons and electrons in the films produced and relate to the electronic structure. The values of the VELF were found to be greater than those of the SELF, which confirms that the energy loss occurred mostly within the material. Films were also examined for water vapor transmission (WVT) and water vapor permeability (WVP), and the results showed that incorporation of TiO2NPs onto chitosan caused a decrease of WVT and WVP. In addition, the antimicrobial activity of the nanocomposite films against Gram-positive and Gram-negative bacteria was studied, and good antimicrobial activity was found, indicating their ability to inhibit bacterial proliferation at the culture site. The developed chitosan thin films supporting an optimized amount of TiO2NPs could be used to treat various diseases.

Extraction of microbial chitosan for piezoelectric application

Chitosan is a natural polysaccharide derived from chitin which is found in the fungus cell walls and crustacean shells. Chitosan has generated a great interest in piezoelectric application because of its interesting properties such as biodegradability, biocompatibility, and low toxicity. The purpose of this study is to focus on the cultivation, fabrication and characterization of chitosan thin film from fungal strain, Aspergillus oryzae cell walls. The fungi was cultivated in bioreactor. Fabrication of chitosan thin film via solvent casting method was optimized via one-factor-at-a-time (OFAT) with 2 parameters (drop-casting volume of solution and drying temperature). Pure chitosan dissolved in formic acid at 0.25 M concentration, dried at 60°C with 35 mL of solution volume gave the highest mechanical quality factor (3.22) and the lowest dissipation factor (0.327) for thin film fabrication. The optimized fabricate thin film was validated using fungal chitosan and shows the results of mechanical quality factor (3.68) and dissipation factor (0.248) which is comparable to conventional piezopolymer thin film. Therefore, fungal chitosan thin film obtained in this study has the potential to be used in piezoelectric application.

Ultra-short laser pulse modification of chitosan/silver nanoparticles (AgNPs) thin films for potential antimicrobial applications

The last several years witnessed increasingly rapid advances in applying biopolymers in tissue engineering for the purposes of regenerative medicine. The growing demand for preparing materials with desired physical, biological and mechanical properties requires active investigations in the field of tissue engineering. Among the wide variety of biopolymers, chitosan proved to be an outstanding material due to its properties, such as biocompatibility, biodegradability and a wide range of available fabrication technologies. The present work is a case study of an extensive research on the functionalization of thin biopolymer films via laser patterning. The aim of the current study is to investigate the optical properties of biopolymer films on the example of chitosan and chitosan with silver nanoparticles additives. As laser sources are used a nano- and a femto-second laser system emitting the wavelengths of 355 nm and 800 nm, respectively. The compositions produced are investigated by spectral analyses using spectrometers and an optical microscope. Furthermore, the morphology of the samples is monitored by SEM analyses. The results obtained demonstrate the potential of the method employed for obtaining diverse porous modifications depending on the laser parameters. Adding silver nanoparticles will drastically increase the thin chitosan films’ antimicrobial properties, thus enhancing the biocompatibility properties of the 2D matrices created.

Enhancement of the dynamic mechanical properties of chitosan thin films by crosslinking with greenly synthesized silver nanoparticles

Over the last decade, chitosan films have promising applications due to their biocompatible, biodegradable, non-toxic, and mucoadhesive nature; haemostatic effects; as well as antimicrobial and biological activities. The conjugation of chitosan with green synthesized silver nanoparticles (SNPs) to form a nanocomposite film will greatly affect the structural properties of chitosan film. This study aimed to evaluate the physical properties of chitosan films doped with different concentrations of SNPs (100–400 μg). X-ray diffraction (XRD) and dynamic mechanical analysis (DMA) were measured for pure chitosan and chitosan films doped with SNPs (100–400 μg). XRD pattern for chitosan film doped with the highest concentration of SNPs (400 μg) showed a decrease in the crystallinity of the chitosan matrix compared with the other doped films. Also, DMA results showed that the storage modulus of the nanocomposite films is dependent on the concentration of SNPs. Accordingly, chitosan film doped with high concentration of SNPs (400 μg) affected the structure and viscoelastic behaviour of chitosan. Thus, the integration of green synthesized silver nanoparticles using aloe vera extract with chitosan films identifies promising candidate in biomedical applications.

The effect of content and thickness of chitosan thin films on resistive switching characteristics

Introduction: Nowadays, a resistive switching memory using biological, transparent, and environmentally friendly materials is appreciated as the tendency of science and technology, especially in the field of electronic devices. Chitosan (CS), having dominant characteristics such as non-toxic, biocompatible and large capacity, plays as a switching medium in resistive random access memory devices (RRAM).
 Methods: In our study, CS film was fabricated onto a commercial substrate (FTO) using a simple spin coating method, and the top electrode (Ag) was deposited by a direct-current sputtering technique.
 Results: The Ag/CS/FTO devices shown the bipolar switching behavior when applying sequence voltage from -1.5 to 2V with the set process in the negative bias and the reset process in the positive bias. The content (0.2, 0.5, and 0.8 wt%) and thickness (100, 300, 500 nm) of chitosan film significantly affect the resistive switching performance. The devices with 0.5 wt%/v concentration and 300 nm-thickness of CS have shown better efficiency than the others with endurance over 100 sweeping cycles and ON/OFF ratio at ca. 2x10 times.
 Conclusions: It is found that the chitosan material has a large potential candidate for applications in optoelectronic devices.

Preparation and Thermal Analysis of Flame-retardant Chitosan Thin Films on Ammonium Polyphosphate Treated Reconstituted Tobacco Sheet

Background: Burning temperature is one of the most important factors affecting the chemical structure of the smoke and the addition of reconstituted tobacco sheet to cut tobacco has been widely used by the tobacco industry to reduce the cost of cigarettes and the health risks of smoking. Methods: A flame retardant film, made from chitosan and ammonium polyphosphate, has been coated on the surface of the reconstituted tobacco sheet substrate by Layer-by-Layer and spray coating techniques. The thermal degradation properties and flame retardancy of these reconstituted tobacco sheets were analyzed by TG-FTIR and micro-scale combustion calorimetry. Results: It was found that the reconstituted tobacco sheet with the ratio of chitosan (5%) and ammonium polyphosphate (3%) film coating showed significant reductions in the peak heat release rate (50.7%), total heat release (35.8%) and the highest temperature in the temperature distribution diagram (77°C). The main gases released during the pyrolysis of these reconstituted tobacco sheet samples were H2O, CO2, CO, NH3, carbonyl compounds and the presence of film coating changed the formation of evolved volatile products and formed less gaseous products except NH3 during the thermal decomposition process. Conclusion: The coating film can greatly enhance the char forming ability and reduce the flammability of reconstituted tobacco sheet, and therefore, reduce the health risks of smoking with the addition of these reconstituted tobacco sheets.

Evaluation of the mechanical, physical and antimicrobial properties of chitosan thin films doped with greenly synthesized silver nanoparticles

Chitosan is a natural polysaccharide with unique physical, chemical and biological properties that potentiates its use in many biomedical applications. In this study, chitosan thin film was doped with different concentrations of green synthesized silver nanoparticles (AgNPs) (100−400 μg) to improve its mechanical and antimicrobial activity. Transmission electron microscopy (TEM), UV–vis absorption spectroscopy and dynamic light scattering (DLS) were used to characterize the silver nanoparticles. The silver-doped chitosan films were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) in addition to assessment of their mechanical and antimicrobial properties. The characterization results revealed the successful formation of spherical silver nanoparticles with a size distribution of 100 nm ± 40 nm. The mechanical properties of chitosan film doped with silver nanoparticles (300, 400 μg) showed superior mechanical properties over pure chitosan film. Compared with pure chitosan film, silver nanoparticles doped chitosan films showed significant antibacterial activity against Staphylococcus aureus. Chitosan film doped with 300 μg AgNPs showed significant antifungal activity against Candida albicans compared with pure chitosan. Accordingly, doping of chitosan film with silver nanoparticles greatly improves its mechanical properties and antimicrobial activity.