Properties Of Chitosan-based Films Research Articles

Poly(limonene): A novel renewable oligomeric antioxidant and UV-light blocking additive for chitosan-based films

Limonene is a well-known bioactive additive for biopolymer-based films. However, its high volatility considerably limits such applications. Herein, we propose the use of a low molecular weight poly(limonene) (PLM) as an alternative high-performance additive for chitosan-based (CH) films. Effects of different concentrations (0.15–0.45 % w/w) of PLM on the properties of CH films were systematically evaluated. Overall, films with impressive antioxidant activity and UV light barrier were easily obtained, even at reduced PLM loads. Among the concentrations explored, there was a reduction in the film’s tensile strength from 23.73 to 12.08 MPa, when the maximum concentration of PLM (0.45 %) was used. However, the elongation at break did not change significantly for any sample. Additionally, the water vapor transmission rate decreased from approximately 547 to 412 g m−2 day−1. Therefore, PLM demonstrates the potential to appear as a novel high-stability additive for active bio-based film development serving food packaging.

Effect of Mixed Oxide-Based TiO2 on the Physicochemical Properties of Chitosan Films

The physicochemical, mechanical, and structural properties of chitosan-based films (CS) alone or CS-films with mixed oxide nanoparticles (TiO2-ZnO-MgO, TZM; CSTZM) at different concentrations (125, 250, and 500 μg mL−1) were investigated. The addition of nano-TZM promoted a color change (from colorless to white) in the film-forming solution, which increased its turbidity and it decreased viscosity. CSTZM were semitransparent (transmittance, T% decreased up to 49%) compared to CS-based films (T% = 95.5). CSTZM (particularly at a concentration of 500 μg mL−1) exhibited an improvement in the moisture content (decreased from 12.6 to 9.67%), water solubility (decreased from 14.94 to 10.22%), degree of swelling (increased from 19.79 to 36.28%), water vapor barrier (decreased from 6.62 x 10−16 to 4.33 x 10−16 g m−1 h−1 Pa−1), thermal stability (the endotherm peak increased from 99.5 to 157.7 °C), and mechanical properties (tensile strength and elongation at break increased from 4.15 to 4.98 kPa and 6.96 to 56.18%, respectively, while the modulus of elasticity decreased from 144 kPa to 4.11 kPa), without toxicity effects on Artemia salina (93.33% survival). X-ray diffraction and Fourier transform infrared studies demonstrated an interaction between CS-based films and nano-TZM. Overall, this film exhibited great potential for diverse industrial applications.

Examining the Impact of Squaric Acid as a Crosslinking Agent on the Properties of Chitosan-Based Films.

Hydrogels based on chitosan are very versatile materials which can be used for tissue engineering as well as in controlled drug delivery systems. One of the methods for obtaining a chitosan-based hydrogel is crosslinking by applying different components. The objective of the present study was to obtain a series of new crosslinked chitosan-based films by means of solvent casting method. Squaric acid—3,4-dihydroxy-3-cyclobutene-1,2-dione—was used as a safe crosslinking agent. The effect of the squaric acid on the structural, mechanical, thermal, and swelling properties of the formed films was determined. It was established that the addition of the squaric acid significantly improved Young’s modulus, tensile strength, and thermal stability of the obtained materials. Moreover, it should be stressed that the samples consisting of chitosan and squaric acid were characterized by a higher swelling than pure chitosan. The detailed characterization proved that squaric acid could be used as a new effective crosslinking agent.

Influence of Genipin Crosslinking on the Properties of Chitosan-Based Films.

Chitosan is a promising environment friendly active polymer packaging material due to its biodegradability, exceptional film forming capacity, great mechanical strength, appropriate barrier property along with intrinsic antioxidant and antimicrobial features. Bifunctional reagent was used for producing water insoluble chitosan films. Biopolymeric films crosslinked by Genipin (Gp), which is a reagent of natural origin, should have high potential in food packaging. The influence of the ratio of functional groups in the chitosan-Gp system on film absorption in the visible and ultraviolet regions of the spectrum, sorption, physical, and mechanical properties of the films has been studied. The degree of chitosan crosslinking in the films obtained from solutions containing Gp was estimated using the experimental data on film swelling and water vapor sorption isotherms. It is demonstrated that crosslinking with genipin improves swelling, water resistance, and mechanical properties of the films.

Influence of Glutaraldehyde Crosslinking and Alkaline Post-treatment on the Properties of Chitosan-Based Films

Depending on the modifications proposed, chitosan films present different characteristics, for instance correlated to hydrophilicity, chemical and mechanical properties. The aim of this study was to evaluate the influence of glutaraldehyde crosslinking and an alkaline post-treatment with NaOH on the characteristics of chitosan based films. Films were obtained by casting and characterized by thickness, swelling degree, mechanical and thermal properties and chemical structure. The water vapor permeability (WVP) was also evaluated for food packaging application. It was observed that crosslinking and NaOH post-treatment have great influence on the chitosan films characteristics. Crosslinking reduced the swelling degree of films and increased its fragility, whereas NaOH treatment also reduces the swelling degree and changes mechanical properties, acting in the same way as a crosslinker. The WVP analyses showed that the basic treatment could substitute the glutaraldehyde crosslinking for film water stability, without greatly compromising the barrier properties of chitosan based films.

Chitosan films incorporated with nettle (Urtica dioica L.) extract-loaded nanoliposomes: I. Physicochemical characterisation and antimicrobial properties

The objective of this study was to characterise and compare physical, mechanical and antimicrobial properties of chitosan-based films, containing free or nanoencapsulated nettle (Urtica dioica L.) extract (NE) at concentrations of 0, 0.5, 1 and 1.5% w/w. Nanoliposomes were prepared using soy-lecithin by thin-film hydration and sonication method to generate an average size of 107–136 nm with 70% encapsulation efficiency. The information on FT-IR reflected that some new interaction have occurred between chitosan and nanoliposomes. Despite the increasing yellowness and decreasing whiteness indexes, the nanoliposomes incorporation improved the thermal properties and mechanical stiffness and caused to decrease water vapour permeability (WVP), moisture uptake and water solubility. The possible antimicrobial activity of the films containing NE-loaded nanoliposomes against Staphylococcus aureus was decreased in comparison to free NE-incorporated films, which could be due to the inhibition effect of the encapsulation that prevents the release of NE from the matrix.

Development of Greener Multi-Responsive Chitosan Biomaterials Doped with Biocompatible Ammonium Ionic Liquids

There is a current interest in the development of new stimuli-responsive materials using biodegradable and biocompatible molecules, mainly if biomedical applications are envisaged. In this work, chitosan (a cationic polyelectrolyte obtained from renewable resources) and two ammonium-based ionic liquids (ILs), namely, choline chloride ([Ch][Cl]) and choline dihydrogen phosphate ([Ch][DHP]), were used to develop biocompatible and biodegradable materials that can be used as improved electrical and pH-sensitive drug delivery systems. The influence of each IL and of residual acetic acid on the properties of chitosan-based films was evaluated. Results showed that the employed ILs can affect the water vapor sorption capacities, water vapor transmission rates, elastic moduli, and impedances/conductivities of chitosan films. Acidic pH conditions significantly enhanced the conductivity and the actuation capacity of the films, and this effect was more pronounced for films loaded with [Ch][DHP]. The potential use of these films as tunable and stimuli-responsive drug delivery systems was also studied for chitosan films loaded with [Ch][DHP] and sodium phosphate dexamethasone (DXA). The amount of DXA released from films doped with [Ch][DHP] was always lower than for films without IL, independent of the pH of the release medium. Therefore, choline-based ILs can be used as additives to tune drug release profiles of ionic drugs from chitosan-based materials. Furthermore, the simultaneous effect of ILs on the conductivities/impedances of films will allow the development of biocompatible and biodegradable drug delivery responsive systems for several biomedical/pharmaceutical applications such as iontophoretic devices.

Effect of essential oils and homogenization conditions on properties of chitosan-based films

The influence of essential oil type (basil and thyme), its content and the homogenization treatment on the physical properties of chitosan-based film-forming dispersions and edible films was studied. Two homogenization treatments were applied, without (H1) and with (H2) microfluidization (MF) at 165 MPa. H2 emulsions showed the smallest particle size with the highest ζ-potential and the lowest viscosity. Composite films with essential oils were softer, less rigid and more stretchable than pure CH films. MF intensified these changes. H2 films showed micro-cracks due to the weakening of the polymer chain interaction forces when oils are present, which affected their mechanical behaviour. MF increased WVP of pure CH films while oil incorporation was only effective to reduce WVP when they were incorporated at the lowest ratio and when high pressure was used in the homogenization of the film-forming dispersion. Gloss was reduced by the essential oil addition, whereas MF tended to yield glossier films.