Modified Gelatin Films Research Articles

Gelatin-Immobilized Cu(II) Metal Complex: Synthesis and Applications

Gelatin, resulting from collagen, a naturally occurring protein found in ligaments and tissues, is formed through the boiling of connective tissues, bones and animal skins, commonly sourced from cows. Its exceptional properties, including the ability to form strong, transparent gels and flexible films, easy digestibility, solubility in hot water and positive binding action, make gelatin a highly valuable resource in various industries such as food processing, pharmaceuticals, photography and paper production. It is regarded as non-toxic, biocompatible, biodegradable and generally safe for use. Gelatin serves as a key ingredient in the manufacturing of a wide range of products, with a notable example being hard gelatin capsules, which come in varying levels of solubility in water. In this study, a Schiff base was synthesized by modifying gelatin with salicylaldehyde in ethanol at room temperature, a mixture of gelatin-Schiff base added to appropriate copper chloride sonicated in ethanol, the mixture was poured onto glass plates and allowed to dry. Modified gelatin film was produced and characterized using FTIR spectroscopy, while its surface properties were examined through Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Furthermore, the modified gelatin film’s potential biological activity was assessed against bacterial strains. The antibacterial screening tests revealed that the modified gelatin exhibited promising antibacterial activity against microorganisms, indicating an improvement in its antibacterial efficacy. These findings highlight the enhanced antibacterial potential of the modified gelatin film, further contributing to its versatility and potential applications in various fields. Different molecular weight distributions within the gelatin can lead to variations in film formation and subsequent surface features. Additionally, the composition of the gelatin film, including the presence of any crosslinking agents or modified functional groups, can further influence the resulting surface morphology. This study focuses on the preparation of modified gelatin films using suitable aldehyde compounds and explores their potential for pharmaceutical applications. Various techniques assessment of biological activity will be employed to investigate the properties and performance of the modified gelatin films. HIGHLIGHTS A Schiff base was synthesized by modifying gelatin with salicylaldehyde, a mixture of gelatin-Schiff base added to appropriate copper chloride to produce gelatin-Schiff base-Cu(II) complex Modified gelatin characterized using FTIR spectroscopy, while its surface properties were examined through SEM and AFM The modified gelatin film’s potential biological activity was assessed against bacterial strains GRAPHICAL ABSTRACT

Native and Modified Gelatin Films Produced by Casting, Extrusion, and Blowing Extrusion Processes

Samples of native gelatin and gelatin modified by acylation and esterification were processed by casting and thermoplastic extrusion to produce laminated and tubular films. Extruded films containing sorbitol showed homogeneity and flexibility. Thinner films were obtained with the addition of sorbitol to the formulation. Tubular films prepared from gelatin modified with stearic acid were easily processed, had reduced friction, and were able to withstand bubble formation without fracturing after preparation. Films prepared by casting or thermoplastic techniques showed a decrease in tensile strength with the addition of plasticizer, and this also resulted in a substantial increase in their elongation ratio. The stearic acid modified gelatin-based films processed by blown extrusion showed higher tensile strength. Films fabricated by casting were, in general, less soluble than those prepared by extrusion except the films modified with stearic acid with or without the addition of plasticizer.

Tailoring physical properties of transglutaminase-modified gelatin films by varying drying temperature

Transglutaminase (TGase)-modified gelatin films containing different levels of physical and chemical networks were prepared by drying films above or below gelation temperature of gelatin. Differences in protein network structure were observed by optical microscopy analysis in freeze-dried film-forming solutions. The relative amount of triple helices decreased when drying temperature increased as observed by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The addition of TGase slightly inhibited triple helix formation. TGase-modified films exhibited stronger mechanical properties than blank films, and the highest tensile strength was observed in films dried close to the gelation temperature (25 °C) and the highest elongation at break above it (35 °C). TGase modification enhanced the water resistance and thermal stability of gelatin films by decreasing the water solubility, increasing the glass transition temperature and degradation temperature, respectively, which was further enhanced with increasing drying temperature. The cross-section (SEM) and surface (AFM) microstructure of gelatin films with TGase both appeared more compact and smooth, and improved when temperature increased. The results obtained show that drying temperature may be used to tailor the physical properties of TGase-modified gelatin films for specific applications.

Properties of gelatin films cross–linked by N-hydroxysuccinimide–activated furandicarboxylic acid (NHS-FDCA)

N-hydroxysuccinimide-activated furandicarboxylic acid (NHS-FDCA), a novel cross-linker, was synthesized to modify gelatin films. The properties of cross-linked gelatin solution was also explored, which showed residual-free amino and viscosity reached best level when mol(NHS-FDCA)/mol(–NH2) ≥1.5. A more homogeneous film was observed by SEM and DSC results exhibited higher decomposition temperature (Td) compared with original films. The degradation test verified better compatibility of modified gelatin films. Finally, the optimization experiment was carried out via free-NH2 and viscosity test.

Modified Gelatin Films from Croaker Skins: Effects of pH, and Addition of Glycerol and Chitosan

AbstractThis work evaluated the effects of pH (3, 4 and 5) and addition of glycerol (10, 20 and 30%, w/w) in films of gelatin extracted from croaker skins, and afterward modified by chitosan. The gelatin films were produced by casting technique. The chitosan additions (10, 20 and 30% w/w) in relation to the gelatin films were analyzed. Films were characterized as tensile strength (TS), elongation, water vapor permeability (WVP) and optical properties (color, color variation and opacity). Gelatins were characterized for gel strength (221 g) and viscosity (3.7 cP), and chitosan was obtained from shells of shrimp and characterized (150 kDa and deacetylation degree of 85%). The gelatin film with 10% (w/w) glycerol and pH 4 showed the best TS value and suitable WVP value. The amount of chitosan of 10% (w/w) added to the gelatin film on the best conditions produced the modified films with the best properties of TS and WVP.Practical ApplicationsSeveral types of biopolymeric films have been developed, combining proteins and polysaccharides, and among these, gelatin and chitosan take on homogeneous form because of miscibility between the two biopolymers. Improvements in the connection crossed in gelatin mixture with chitosan are attributed to the formation of polielectrolic compounds, among the groups of amino of the chitosan and of the groups of lateral chains charged negatively of the gelatin through electrostatic interaction. The study of the mechanical properties of the biodegradable films is a subject of great importance, because of its influence on the acting of the product and the consumer's acceptance. In this context, the intensification need is observed in the studies about the gelatin extraction starting from fish skins and its application in the production of pure and modified films with chitosan and plasticizer.

Bonding behavior of hydrophobically modified gelatin films on the intestinal surface

The bonding behavior was determined for hydrophobically modified alkaline-treated gelatin on wet porcine intestinal surfaces. The modified gelatin films were obtained by reacting the amino groups of alkaline-treated gelatin with fatty acid chlorides of different alkyl chain lengths, namely, hexanoyl (Hx: C6) chloride, decanoyl (Dec: C10) chloride, and stearoyl (Ste: C18) chloride. Three kinds of the films were prepared, 32HxAlGltn, 24DecAlGltn, and 26SteAlGltn that had substitution ratios of hydrophobic groups to the amino groups of 32HxAlGltn, 24DecAlGltn, and 26SteAlGltn of 32%, 24%, and 26%, respectively. The 32HxAlGltn film had the strongest bonding to porcine intestinal surfaces. A thick 32HxAlGltn film remained on the intestinal surface even after the bonded film was scraped off for the measurement of bonding strength. In addition, the burst strength increased with an increase in the substitution ratio of the Hx group. Thus, the HxAlGltn film with the higher Hx modification ratio has a potential as a sealant material to prevent agglutination of intestinal surfaces.

Enhanced Bonding Strength of Hydrophobically Modified Gelatin Films on Wet Blood Vessels

The bonding behavior between hydrophobically modified alkaline-treated gelatin (hm-AlGltn) films and porcine blood vessels was evaluated under wet conditions. Hexanoyl (Hx: C6), decanoyl (Dec: C10), and stearyl (Ste: C18) chlorides were introduced into the amino groups of AlGltn to obtain HxAlGltn, DecAlGltn, and SteAlGltn, respectively, with various modification percentages. The hm-AlGltn was fabricated into films and thermally crosslinked to obtain water-insoluble films (t-hm-AlGltn). The 42% modified t-HxAlGltn (t-42HxAlGltn) possessed higher wettability than the 38% modified t-DecAlGltn (t-38DecAlGltn) and the 44% modified t-SteAlGltn (t-44SteAlGltn) films, and the t-42HxAlGltn film showed a high bonding strength with the blood vessel compared with all the hm-AlGltn films. Histological observations indicated that t-42HxAlGltn and t-38DecAlGltn remained on the blood vessel even after the bonding strength measurements. From cell culture experiments, the t-42HxAlGltn films showed significant cell adhesion compared to other films. These findings indicate that the Hx group easily interpenetrated the surface of blood vessels and effectively enhanced the bonding strength between the films and the tissue.

Glyoxal modification of gelatin leads to change in properties of solutions and resulting films

The influence of different pretreated film forming solutions (FFSs) on the physical, chemical and barrier properties of gelatin films was studied. Hydrolyzation with hydrochloric acid and acetylation with acetic acid anhydride at different pHs were performed. Subsequently, gelatin was crosslinked with glyoxal to result in biopolymer films with properties predetermined by the rheological behavior of the respective FFS. Gel time, storage modulus and tan δ of FFSs were obtained from small-strain oscillatory measurements and were correlated with swelling and solubility of the resulting films as well as with chemical analysis of lysine and arginine and the respective amino acid modifications Ne-carboxymethyllysine (CML), glyoxal derived lysine dimer (GOLD) and 5-(2-imino-5-oxo-1-imidazolidinyl)norvaline (imidazolinone). In general, chemical modification reduced the storage modulus whether it was hydrolyzation, acetylation or modification with glyoxal. Treatment by hydrolyzation or acetylation led to differences in gel time and in the ratio between viscous and elastic portion of the different hydrogels, also affecting the relationship between monovalent amino acid modification and bivalent crosslinking after glyoxal addition. Thus, the structural character of FFS hydrogels and of the protein network of films both determined the physical and barrier properties of chemically modified gelatin films.

Photocuring of Gelatin Films with TMPTMA: Effect on Aging Properties

Gelatin films were prepared from granular gelatin by casting. Gelatin films were modified by photocuring with a trifunftional monomer Trimethylolpropane trimethacrylate (TMPTMA). Optimum condition for photocuring were established. Water aging of untreated and modified gelatin films was studied. Thermal aging of untreated and TMPTMA treated films were determined at different temperatures (50°C, 70°C and 100°C) for 60 min. pH aging of gelatin films were investigated in different pH solutions (3.2, 4.1, 4.8, 6.9, 9.2, 12.2) for 1min. Water aging, thermal aging and pH aging showed that the TMPTMA grafted gelatin films experienced less deterioration of mechanical properties than pure gelatin films.

Properties of chemically modified gelatin films

Edible and/or biodegradable films usually have limited water vapor barriers, making it difficult to use them. Thus, the objective of this work was to evaluate the effect of a chemical reticulation treatment with formaldehyde and glyoxal on the mechanical properties, water vapor permeability, solubility and color parameters of gelatin-based films. Formaldehyde and glyoxal were added to the filmogenic solution in concentrations ranging from 3.8 to 8.8 mmoles/100 mL of filmogenic solution and 6.3 to 26.3 mmoles/100 mL of filmogenic solution, respectively. The treatments caused a reduction in permeability to water vapor and in solubility. Only the treatment with formaldehyde caused a significant increase in rupture tension for concentrations above 6.3 mmoles/100 mL of filmogenic solution. Scanning electron microscopy indicated a loss of matrix orientation due to the chemical reticulation treatment.

Preparation and properties of biodegradable stearic acid-modified gelatin films

Gelatin was modified by various amounts of stearic acid using different reaction times in aqueous media at 60 °C and pH of 5.5. By casting the modified gelatin solutions, slightly yellow films were formed. It was found that all modified gelatin films had longer drying time, lower tensile strength, lower % moisture absorption, and better biodegradability than unmodified ones. Their oil resistance was comparable. It was also found that the amount of stearic acid and the reaction time significantly affected these properties. As the amount of stearic acid increased, the films exhibited longer drying time, lower tensile strength and lower moisture absorption. With increasing the reaction time, the films exhibited shorter drying time, higher tensile strength and lower moisture absorption. The results suggest that the film prepared from 15% stearic acid-modified gelatin using the reaction time of 8 h had highest potential for applications in environmental friendly packaging.

Biodegradation of Chemically Modified Gelatin Films in a Simulated Natural Environment

ABSTRACTModified (crosslinked) gelatin films were prepared using various crosslinking agents: formaldehyde, butadiene diepoxide and hexamethylene diisocyanate. They were evaluated for their biodegradability by exposing them to sewage, which was inoculated with periphyton taken from the bottom and walls of municipal sewage systems. Biodegradability was assessed by weight loss of the films and by means of total dehydrogenase activity of the biomass, taken from the surface of the films. Biodegradation was apparent both in uncrosslinked gelatin and in the crosslinked samples. The gelatin crosslinked with hexamethylene diisocyanate degraded fastest (complete degradation in 5 days), followed by uncrosslinked gelatin and gelatin crosslinked with butadiene diepoxide (complete degradation in 10 days). The most stable was the formaldehyde crosslinked gelatin—complete degradation only in 20 days. The dehydrogenase activity increased rapidly up to the 7th day, and then dropped. It paralleled the biodegradation of gelatin and could be used as a measure of biodegradability of crosslinked gelatin, and probably other biodegradable polymers. The periphyton on the surfaces of the films was found to be molds, actinomyces, yeast and bacteria. Various kinds of algae were observed as well, specifically flint algae, brown algae, blue-green algae, and filamentous green algae.

Biodegradation of chemically modified gelatin films in soil

Gelatin films that had been chemically modified (crosslinked with formaldehyde, glyoxal, glutaraldehyde, hexamethylene diisocyanate, butadiene diepoxide, or diepoxyoctane) were tested for their biodegradability by soil burial testing in a laboratory environment under temperature and humidity control. The relationship between weight loss and time of biodegradation showed a linear behavior for all the samples, but the rate of biodegradation showed a dependence on the type of crosslinking agent. The most stable films were those crosslinked with aldehydes, and these biodegraded by the 10th day. The samples crosslinked with hexamethylene diisocyanate and diepoxides completely biodegraded by the fourth and sixth days, respectively. It was shown that the rate of biodegradation depended on the density of crosslinking, which was calculated by a modified Flory–Rehner equation. The biodegraded samples showed considerable changes in the fingerprint region of FTIR spectra, and, thus, these spectra could be used for evaluation of the soil burial biodegradation of chemically modified gelatin samples. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1341–1347, 2000

Biodegradation of chemically modified gelatin films in lake and river waters

Gelatin was chemically modified by crosslinking samples with one of a number of bifunctional reagents as was done earlier in a processing technique used to improve mechanical properties through chain orientation. The effects of this crosslinking on the biodegradability of the resulting films were evaluated in the laboratory by exposing them to lake and river waters for 10 days with or without inoculation with periphyton organisms. Biodegradabilities were assessed by weight losses of the films and by measurements of dehydrogenase activity of biomasses taken from their surfaces. The extent of biodegradation depended on the type of crosslinking agent and the presence or absence of the periphyton. The gelatin films crosslinked with formaldehyde, glyoxal, or glutaraldehyde were the slowest to biodegrade; complete degradation required 8-10 days. In contrast, the most biodegradable was the gelatin crosslinked with hexamethylene diisocyanate, which required only 3-4 days. The uncrosslinked gelatin and the gelatin crosslinked with butadiene diepoxide and diepoxyoctane were intermediate, degrading in 5-7 days. The dehydrogenase activity paralleled the weight losses but rapidly decreased when the amount of gelatin remaining was small.

Biodegradation of chemically modified gelatin films in soil

Gelatin films that had been chemically modified (crosslinked with formaldehyde, glyoxal, glutaraldehyde, hexamethylene diisocyanate, butadiene diepoxide, or diepoxyoctane) were tested for their biodegradability by soil burial testing in a laboratory environment under temperature and humidity control. The relationship between weight loss and time of biodegradation showed a linear behavior for all the samples, but the rate of biodegradation showed a dependence on the type of crosslinking agent. The most stable films were those crosslinked with aldehydes, and these biodegraded by the 10th day. The samples crosslinked with hexamethylene diisocyanate and diepoxides completely biodegraded by the fourth and sixth days, respectively. It was shown that the rate of biodegradation depended on the density of crosslinking, which was calculated by a modified Flory–Rehner equation. The biodegraded samples showed considerable changes in the fingerprint region of FTIR spectra, and, thus, these spectra could be used for evaluation of the soil burial biodegradation of chemically modified gelatin samples. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1341–1347, 2000