Acid Films Research Articles

Zinc Oxide–Incorporated Chitosan–Poly(methacrylic Acid) Polyelectrolyte Complex as a Wound Healing Material

A novel type of porous films based on the ZnO-incorporated chitosan-poly(methacrylic acid) polyelectrolyte complex was developed as a wound healing material. The structure of porous films was established by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) analysis. Scanning electron microscope (SEM) and porosity studies revealed that the pore size and porosity of the developed films increased with the increase in zinc oxide (ZnO) concentration. The porous films with maximum ZnO content exhibited improved water swelling degree (1400%), controlled biodegradation (12%) for 28 days, a porosity of 64%, and a tensile strength of 0.47 MPa. Moreover, these films presented antibacterial activity toward Staphylococcus aureus and Micrococcus sp. due to the existence of ZnO particles. Cytotoxicity studies demonstrated that the developed films had no cytotoxicity against the mouse mesenchymal stem (C3H10T1/2) cell line. These results reveal that ZnO-incorporated chitosan-poly(methacrylic acid) films could be used as an ideal material for wound healing application.

Comparative analysis on poly lactic acid and chitin fortified poly lactic acid films

Comparative analysis on poly lactic acid and chitin fortified poly lactic acid films

Elucidating Trivalent Ion Adsorption at Floating Carboxylic Acid Monolayers: Charge Reversal or Water Reorganization?

We study the adsorption of trivalent neodymium on floating arachidic acid films at the air-water interface by two complementary surface specific probes, sum frequency generation spectroscopy and X-ray fluorescence near total reflection. In the absence of background ions, neodymium ions compensate for the surface charge of the arachidic acid film at a bulk concentration of 50 μM without any charge reversal. Increasing the bulk concentration to 1 mM does not change the neodymium surface coverage but affects the interfacial water structure significantly. In the presence of a high concentration of NaCl, there is overcharging at 1 mM Nd3+, i.e., 30% more Nd3+ than needed to compensate for the surface charge. These results show that the total coverage of neodymium ions is not enough to describe the complete picture at the interface, and interfacial water and ion coverage needs to be considered together to understand more complex ion adsorption and transport processes.

Incorporation of Ag NPs/palygorskite into chitosan/glycyrrhizic acid films as a potential antibacterial wound dressing

Chitosan/glycyrrhizic acid (CG) film has poor mechanical properties and antibacterial activity, which limits its practical application in wound dressing. In this study, Ag nanoparticles/palygorskite (Ag NPs/Pal) nanocomposites with different mass ratios were prepared by the metal salt pyrolysis and incorporated to synergistically improve the mechanical and antibacterial properties of CG films. The structural characteristics of CS/GA/Ag/Pal (CGAP) namocomposite films were characterized by SEM, ATR−FTIR and XRD. The effects of Ag NPs/Pal nanocomposites with different mass ratios on the physicochemical properties of the CGAP films were evaluated by systematic experiments. The CGAP nanocomposite films prepared by introducing Ag NPs/Pal nanocomposite with the mass ratio of AgNO3 to Pal of 0.5 had a uniform distribution of inorganic filler, good mechanical properties (tensile strength was 25.65 MPa and elongation at break was 63.71%) and excellent antibacterial activity (antibacterial effectiveness up to 100%), and preserved favorable swelling behavior (144.70%), acceptable light transmittance (T800 was 62.95%) and outstanding biocompatibility (hemolysis percentage was 1.69%). Overall, the above results demonstrate that the CGAP composite films are suitable for wound dressings in biomedical applications.

Nonmigrating Active Antibacterial Packaging: Antimicrobial Mechanism against Staphylococcus Aureus and Its Application in Large Yellow Croaker

In this study, chitosan (CS) was grafted onto the surface of polylactic acid (PLA) film by covalent immobilization to prepare four kinds of CS-grafted PLA (CS-g-PLA) films with different molecular weights. The properties of the films were characterized, and their antibacterial effect and mechanism of action against Staphylococcus aureus (S. aureus) were explored. After being treated with CS-g-PLA films, the cell morphology was destroyed, the permeability of the cell membrane changed, and malate dehydrogenase (MDH) activity decreased. Furthermore, the large yellow croaker fillets were packaged by the films mentioned above and stored at 4 °C, the physicochemical changes and microbial counts were measured. The results showed that the CS-g-PLA films could effectively delay the decay of fish fillets for 1–4 days. Overall, this study demonstrated that grafted films showed great application potential in aquatic product packaging and preservation.

Modeling the release of an antimicrobial agent from multilayer film containing coaxial electrospun polylactic acid nanofibers

The research of active biodegradable multilayer materials are of current interest for developing functional and sustainable packages able to guarantee the microbiological safety of food. In this work, an active biodegradable trilayer packaging system composed of (1) an external layer of extruded polylactic acid (PLA) film, (2) an intermediate layer of electrospun PLA loaded with ethyl lauroyl arginate (LAE) and cellulose nanocrystals (CNC), and (3) an inner layer of chitosan processed by coating, was developed. Optical, structural, and thermal properties were evaluated. Furthermore, a mathematical mass transfer model focused on the fibers structure was developed to study the LAE release to aqueous and fatty food simulants. Compared to extruded PLA, the trilayer material was white and opaque with a ΔE = 2.6. Furthermore, the processing of material produced a scarce interaction between their components and its crystallinity was increased by 85%. K coefficients were lower than 100 evidencing the high affinity of LAE for both simulants, while D coefficients ≈0.5x10−17m2s−1 demonstrated the slow diffusion of LAE through the material.

Development and Characterization of Salicylic Acid Film Forming Gel for the Treatment of Hyperkeratotic and Scaling Disorders

Development and Characterization of Salicylic Acid Film Forming Gel for the Treatment of Hyperkeratotic and Scaling Disorders

Antibacterial Properties of Three-Dimensional Flower Cluster ZIF-L Modified by N-Doped Carbon Dots

To overcome the problems of excessive ion release of inorganic antimicrobial agents and the biological toxicity of organic antimicrobial agents, metal organic framework (MOF) materials are attracting attention in the antimicrobial field due to their tunable structural properties and multifunctional applications. Most current studies are limited to zeolitic imidazolate framework-8 (ZIF-8), which has low antimicrobial efficiency by component release. Two-dimensional (2D) zeolitic imidazolate framework nanoleaf (ZIF-L) possesses better antimicrobial effect than ZIF-8 because of the physical destructionto bacteria by its blade tip. However, the in-situ synthesis method of two-dimensional ZIF-L, and the problem of leaf accumulation, limit the wider application of ZIF-L. In this paper, three-dimensional(3D) flower cluster-like ZIF-L (2–3 μm, +31.23 mv), with better antibacterial effects and a wider application range, was prepared by stirring without adding other reagents. To further improve the antibacterial performance of ZIF-L, nitrogen-doped carbon dots (NCDs) were electrostatically absorbed by ZIF-L to obtain NCDs@ZIF-L composites. The NCDs@ZIF-L composites showed over 95% and 85% antibacterial efficiency against E. coli and S. aureus, respectively, at a concentration of 0.25 mg/mL. In addition, polylactic acid (PLA) films mixed with ZIF-L and NCDs@ZIF-L composites with PLA showed good antimicrobial properties, indicating the applicability of ZIF-L and NCDs@ZIF-L composites for antibacterial materials. With a unique three-dimensional crystal shape and positive surface charge, ZIF-L and NCDs@ZIF-L composites exhibited excellent antibacterial properties, which provided a new perspective for the study of antimicrobial materials.

New Self-Healing Metallosupramolecular Copolymers with a Complex of Cobalt Acrylate and 4′-Phenyl-2,2′:6′,2″-terpyridine

Currently, the chemistry of self-healing polymers is aimed not only at obtaining materials with high self-healing efficiency, but also at improving their mechanical performance. This paper reports on a successful attempt to obtain self-healing copolymers films of acrylic acid, acrylamide and a new metal-containing complex of cobalt acrylate with a 4'-phenyl-2,2':6',2″-terpyridine ligand. Samples of the formed copolymer films were characterized by ATR/FT-IR and UV-vis spectroscopy, elemental analysis, DSC and TGA, SAXS, WAXS and XRD studies. The incorporation of the metal-containing complex directly into the polymer chain results in an excellent tensile strength (122 MPa) and modulus of elasticity (4.3 GPa) of the obtained films. The resulting copolymers demonstrated self-healing properties both at acidic pH (assisted by HCl healing) with effective preservation of mechanical properties, and autonomously in a humid atmosphere at room temperature without the use of initiators. At the same time, with a decrease in the content of acrylamide, a decrease in the reducing properties was observed, possibly due to an insufficient amount of amide groups to form hydrogen bonds through the interface with terminal carboxyl groups, as well as a decrease in the stability of complexes in samples with a high content of acrylic acid.

An electrospun polylactic acid film containing silver nanoparticles and encapsulated Thymus daenensis essential oil: release behavior, physico-mechanical and antibacterial studies

An electrospun polylactic acid film containing silver nanoparticles and encapsulated Thymus daenensis essential oil: release behavior, physico-mechanical and antibacterial studies

Development and Evaluation of Fast Dissolving Oral Films of Mefenamic Acid for the Management of Fever

Abstract: The marketed formulations of Mefenamic Acid (MA) used for the treatment of fever in the paediatric population are reported to have several drawbacks. This study aimed to develop and evaluate the mefenamic acid–loaded oral dispersible films which may be a better alternative than the existing formulations. The solubility of mefenamic acid was enhanced by forming inclusion complexes with β cyclodextrin. The best ratio for the mefenamic acid-β cyclodextrin inclusion complex, 1:0.5 was selected based on the drug content and in vitro drug release. Fourier transform Infrared spectroscopy and scanning electron microscopy analysis was performed on the complex. The oral dispersible films were developed by solvent casting method and evaluated for parameters such as average weight, thickness, pH, folding endurance, percentage moisture uptake and loss, drug content, in vitro disintegration time and drug release. The statistical analysis of the data suggested that oral dispersible films with 4% w/v of crospovidone (coded P3) as the best. Drug content (95.46±0.93%), disintegration time (28.6±2.0 s), cumulative percentage drug release (97.41±0.68% in 180 s), and all other investigated parameters of P3 were well within the acceptable limit. The in vitro dissolution profile of P3 showed no significant difference from the marketed mefenamic acid suspension and has a good stability profile at in-house testing conditions. The data obtained from this investigation revealed that mefenamic acid oral dispersible films could act as an excellent alternative to existing marketed paediatric formulations. Keywords: Oral dispersible films, Mefenamic acid, β Cyclodextrin, Paediatric, Kneading method, Solvent casting.

Construction of fully biodegradable poly(L-lactic acid)/poly(D-lactic acid)-poly(lactide-co-caprolactone) block polymer films: Viscoelasticity, processability and flexibility

Development of biodegradable polymer films is essential for sustainable energy conservation and ecological protection. In this work, to improve the processability and toughness of poly(lactic acid) (PLA) films, poly(lactide-co-caprolactone) (PLCL) segments were introduced into poly(L-lactic acid) (PLLA)/poly(D-lactic acid) (PDLA) chains via chain branching reactions during reactive processing, and fully biodegradable/flexible PLLA/D-PLCL block polymer with long-chain branches and stereocomplex (SC) crystalline structure was prepared. Compared with neat PLLA, PLLA/D-PLCL exhibited much higher complex viscosity/storage modulus, lower tanδ values in terminal region and obvious strain-hardening behavior. Through biaxial drawing, PLLA/D-PLCL films were prepared, which showed improved uniformity and non-preferred orientation. With increasing draw ratio, the total crystallinity (Xc) and Xc for SC crystal both increased. By introduction of PDLA, the two phases of PLLA and PLCL penetrated and entangled with each other, and the phase structure transformed from “sea-island” structure to “co-continuous network” structure, which was beneficial for exerting the toughening effect of flexible PLCL molecules on PLA matrix. The tensile strength and elongation at break of PLLA/D-PLCL films increased from 51.87 MPa and 28.22 % of neat PLLA film to 70.82 MPa and 148.28 %. This work provided a new strategy for developing fully biodegradable polymer films with high performance.

Self‐supporting flexible poly(1‐naphaneneboronic acid) film as green light‐emitting material

AbstractThe flexible conducting polymer films (FCPs) with fused ring structure is of great significance in the field of flexible electronics, yet their preparation is challenging. The mechanical properties can be improved by introducing boric acid groups to FCPs. Herein, free‐standing poly (1‐naphaneneboronic acid) (PNBA) film with a conductivity of 3 × 10−4 S cm−1 is readily prepared by electrochemical polymerization of 1‐naphaneneboronic acid. The PNBA film exhibits good redox activity and electrochemical stability. Fourier transform infrared spectrum proves that polymerization site of the as‐prepared PNBA occurs at C5 and C8 positions. The UV–Vis spectrum proves that the optical band gap of PNBA is 2.76 eV. In addition, thermal analysis reveals that the polymer displays excellent thermal stability. Fluorescence spectroscopy results show that PNBA film is a good green light‐emitting material. These characteristics indicate that free‐standing flexible PNBA film has potential applications in flexible electronic semiconductors, fluorescent materials and electrochemical sensors.

Inner Zn layer and outer glutamic acid film as efficient dual-protective interface of Al anode in Al-air fuel cell

Inner Zn layer and outer glutamic acid film as efficient dual-protective interface of Al anode in Al-air fuel cell

A polymer-based artificial microenvironment for enhancing cell adhesion

An efficient platform capable of cell adhesion needs to be developed to understand cell activities such as cell differentiation, diffusion, and migration. The basic sequence of cell adhesion involves cells communicating with their environment by generating mechanical and chemical signals. Thin polymeric films with micro- or nano-patterns are widely used to support cell growth with conformal contact at the biointerface. However, stable and biocompatible films with high reproducibility on a flexible substrate remain a challenge. As described here, we developed micro-pattern poly(tetrafluoroethyleneco-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acid) (Nafion) films fabricated by a molding process. We present the fabrication and characterization of flexible, micro-patterned Nafion films and the evaluation of cell adhesion and alignment on these films. We found that cell adhesion and migration/direction could be modulated by controlling the surface architecture. This approach offers a new platform that constitutes a promising tool for use in flexible cell-based platforms and devices to observe cell-cell and cell-surface interactions.

Evolution of the free volume during water desorption in thermoplastic starch/citric acid films: In situ positron annihilation studies

The effect of citric acid (CA) concentration and water content on the free hole volume of thermoplastic cassava starch films (TPS) was studied. To this aim, continuous in situ positron annihilation lifetime spectroscopy measurements were performed at fixed moisture content and during water desorption. The results show that the increase in CA concentration leads to wider free hole volume distributions with lower mean values. During water desorption, the mean values and width of such distributions systematically decrease with the exposure time, and the evolution of the hole volumes was well-described using the Kohlrausch-Williams-Watts function. The water vapour permeability was significantly higher in films incorporating 5 % (w/w) of CA, in line with the more open network of this material that was revealed in the hole volumes distribution. The Young's modulus of all the developed films increased significantly after partial water desorption, which was attributed to the plasticizer loss reflected in a decrease in the mean hole volume value (between 4 % and 13 %). This work evidences that the control and report of the relative humidity are essential when testing TPS-based films, as their nanostructures are strongly dependent on external conditions.

Antioxidant and Antimicrobial Effect of Biodegradable Films Containing Pitaya (Stenocereus thurberi) Extracts during the Refrigerated Storage of Fish.

This study focused on the quality loss inhibition of fish muscle during refrigerated storage. Two parallel experiments were carried out that were focused on the employment of pitaya (Stenocereus thurberi) extracts in biodegradable packing films. On the one hand, a pitaya-gelatin film was employed for hake (Merluccius merluccius) muscle storage. On the other hand, a pitaya-polylactic acid (PLA) film was used for Atlantic mackerel (Scomber scombrus) muscle storage. In both experiments, fish-packing systems were stored at 4 °C for 8 days. Quality loss was determined by lipid damage and microbial activity development. The presence of the pitaya extract led to an inhibitory effect (p < 0.05) on peroxide, fluorescent compound, and free fatty acid (FFA) values in the gelatin-hake system and to a lower (p < 0.05) formation of thiobarbituric acid reactive substances, fluorescent compounds, and FFAs in the PLA-mackerel system. Additionally, the inclusion of pitaya extracts in the packing films slowed down (p < 0.05) the growth of aerobes, anaerobes, psychrotrophs, and proteolytic bacteria in the case of the pitaya-gelatin films and of aerobes, anaerobes, and proteolytic bacteria in the case of pitaya-PLA films. The current preservative effects are explained on the basis of the preservative compound presence (betalains and phenolic compounds) in the pitaya extracts.

Insoluble lipid film mediates transfer of soluble saccharides from the sea to the atmosphere: the role of hydrogen bonding

Abstract. Saccharides are a large portion of organic matter in sea spray aerosol (SSA). Although they can affect climate-related properties of SSA, the mechanism through which saccharides are transferred from bulk seawater to the ocean surface and ultimately into SSA is still debated. Here, the transfer of small soluble saccharides was validated using a controlled plunging jet sea spray aerosol generator to better understand the wide range of particle properties produced by natural seawater mixed with model organic species, glucose and trehalose. We showed that both soluble saccharides can promote the production of SSA particles, and the presence of trehalose could increase the SSA number concentration by 49.4 %. Conversely, the role of the insoluble fatty acid film on the seawater surface greatly reduced the production of SSA. The resulting inorganic–organic mixed particles identified by the transmission electron microscope (TEM) showed typical core–shell morphology. A Langmuir model was used to parameterize the adsorption and distribution of saccharide into SSA across the bubble surface, while infrared reflection–absorption spectroscopy (IRRAS) combined with Langmuir isotherms was undertaken to examine the effects of aqueous subphase soluble saccharides with various concentrations on the phase behavior, structure, and ordering of insoluble lipid monolayers adsorbed at the air/water interface. We found that the adsorption of glucose and trehalose on the fatty acid monolayer led to the expansion of the mean molecular area. Saccharide–lipid interactions increased with increasing complexity of the saccharide in the order of glucose &lt; trehalose. In a seawater solution, the effects of dissolved saccharides on the ordering and organization of fatty acid chains were muted. The enhancement of the carbonyl band to the low wavenumber region implied that soluble saccharides can form new hydrogen bonds with fatty acid molecules by displacing large amounts of water near the polar headgroups of fatty acids. Our results indicate that the interaction between soluble saccharides and insoluble fatty acid molecules through hydrogen bonds is an important component of the sea–air transfer mechanism of saccharides.

Towards ductile single-step polyelectrolyte complex films by means of plasticization

Polyelectrolyte complexes (PECs) show great promise as functional coatings, including as oxygen barrier coatings for food packaging, but the brittleness of dry PECs limits their application. In this work, the possibility of plasticizing polyethylenimine/poly(4-styrenesulfonic acid) (PEI/PSS) films was investigated. Three different classes of plasticizers were chosen: salt, polyols, and ionic liquids (ILs). They were successfully incorporated in the evaporation-based single-step method. Potassium bromide or sorbitol plasticized films all showed crystallization upon evaporation, while films plasticized by glycerol, polyethylene glycol, and imidazole-based ILs all showed a clear brittle-to-ductile transition in their mechanical properties. The hydrophilicity of polyols and the amphiphilicity of these ILs allowed them to form homogenous casting solutions, but also increased their water sensitivity. The ionic nature of ILs make them more efficient as plasticizers since they can replace part of the PE-PE ionic-crosslinks, resulting in a more flexible network. Overall, this work demonstrates that ductile PEC films can be formed in a single step with controlled mechanical properties through plasticization.

Effect of orodispersible hyaluronic acid film on palatal mucosa wound healing.

The objective of the study was to evaluate the healing effect of hyaluronic acid films on palatal wounds. After making 5-mm diameter palatal wounds, 72 rats were randomly assigned to three groups: control, hyaluronic acid gel, and hyaluronic acid film. The animals were sacrificed at 3, 7, and 21 days after the experiment. Clinical, histological, and RT-PCR analyses were performed. Human ex vivo oral mucosa models were used. Histological analysis and pan-cytokeratin staining were performed at 5 days after wound creation. In rat model, both gels and films showed favorable healing on Days 3 and 7 compared with healing in the control (p < 0.05). Film showed remarkable VEGF and α-SMA expression than did the others (p < 0.05). Immunohistochemical analysis showed that film exhibited significantly lower CD68 and greater α-SMA and vimentin expression levels than those in the others (p < 0.05). In human model, re-epithelialization rate of film group was significantly higher than that of the others. Complete epithelial regeneration was confirmed only in film group using pan-cytokeratin staining. Within the limits of this study, hyaluronic acid film outperformed gels in terms of palatal wound healing in both models.