Chemical cross-linking gelatin with natural phenolic compounds as studied by high-resolution NMR spectroscopy

Vegetable Additives in Food Packaging Polymeric Materials

Plants are the most abundant bioresources, providing valuable materials that can be used as additives in polymeric materials, such as lignocellulosic fibers, nano-cellulose, or lignin, as well as plant extracts containing bioactive phenolic and flavonoid compounds used in the healthcare, pharmaceutical, cosmetic, and nutraceutical industries. The incorporation of additives into polymeric materials improves their properties to make them suitable for multiple applications. Efforts are made to incorporate into the raw polymers various natural biobased and biodegradable additives with a low environmental fingerprint, such as by-products, biomass, plant extracts, etc. In this review we will illustrate in the first part recent examples of lignocellulosic materials, lignin, and nano-cellulose as reinforcements or fillers in various polymer matrices and in the second part various applications of plant extracts as active ingredients in food packaging materials based on polysaccharide matrices (chitosan/starch/alginate).

Adaptation of hard gelatin capsules for oral delivery of aqueous radiopharmaceuticals

PURPOSE

Oral administration of Iodine-131 (I-131) solutions causes high risk of contamination for patients and dispensers. The objective of the study was to adapt hard gelatin capsules (HGCs) for filling with radiopharmaceutical solutions without deformation.

METHODS

Polystyrene (PS) internally lining films with different thicknesses were used to protect HGCs. The insulated HGCs were evaluated for their physicochemical characteristics and rupturing time in different dissolution media. HGCs internally lined with PS were examined for withstand loading with different volumes and radioactivities of I-131 solutions. Radioactivity release was studied in deionized water and acidic media. Quality control of released I-131 was inspected for radiochemical purities.

RESULTS

There was a directly proportion between PS lining thickness and stability of HGCs after filling with 500 μl aqueous methylene blue solution. HGCs internally lined with PS 100 μm thickness withstand deformation for ˃ two months; however showed fast in-vitro rupturing time in different dissolution media. Internally lined HGCs loaded with different volumes and radioactivities of I-131 solutions resisted for one week without radioactive leakage. Yet, revealed complete release of I-131 after 20 min in dissolution media with great radiochemical purity.

CONCLUSION

The study promises safely I-131 aqueous solution delivery via adapted HGCs. Graphical abstract Oral administration of radiopharmaceuticals.

Bioactive glass based scaffolds coated with gelatin for the sustained release of icariin

Gelatin-coated, 3D sponge-like scaffolds based on 45S5 bioactive glass were produced using the foam replication technique. Compressive strength tests of gelatin-coated samples compared to uncoated scaffolds showed significant strengthening and toughening effects of the gelatin coating with compressive strength values in the range of cortical bone. Additionally, the crosslinked gelatin network (using either caffeic acid or N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC)/N-hxdroxysuccinimide (NHS) as crosslinking agent) was shown to be a suitable candidate for the sustained release of the bioactive molecule icariin. Concerning bioactivity of the produced scaffolds, characterization by FTIR and SEM indicated the formation of hydroxyapatite (HA) in all samples after immersion in simulated body fluid (SBF) for 14 days, highlighting the favorable combination of mechanical robustness, bioactivity and drug delivery capability of this new type of scaffolds.

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Foam like bioactive glass scaffolds produced by replication technique.

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Gelatin coatings confer increased compression strength to scaffolds.

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Crosslinked gelatin coating is suitable candidate for the sustained release of icariin.

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Favorable combination of bioactivity, gelatin coating and icariin release demonstrated.

Development of Gallic Acid-Modified Hydrogels Using Interpenetrating Chitosan Network and Evaluation of Their Antioxidant Activity

In this work, antioxidant hydrogels were prepared by the construction of an interpenetrating chitosan network and functionalization with gallic acid. The poly(2-hydroxyethyl methacrylate) p(HEMA)-based hydrogels were first synthesized and subsequently surface-modified with an interpenetrating polymer network (IPN) structure prepared with methacrylamide chitosan via free radical polymerization. The resulting chitosan-IPN hydrogels were surface-functionalized with gallic acid through an amide coupling reaction, which afforded the antioxidant hydrogels. Notably, gallic-acid-modified hydrogels based on a longer chitosan backbone exhibited superior antioxidant activity than their counterpart with a shorter chitosan moiety; this correlated to the amount of gallic acid attached to the chitosan backbone. Moreover, the surface contact angles of the chitosan-modified hydrogels decreased, indicating that surface functionalization of the hydrogels with chitosan-IPN increased the wettability because of the presence of the hydrophilic chitosan network chain. Our study indicates that chitosan-IPN hydrogels may facilitate the development of applications in biomedical devices and ophthalmic materials.

The synergy between natural polyphenol-inspired catechol moieties and plant protein-derived bio-adhesive enhances the wet bonding strength

Novel soybean meal-based biomimetic (STP) adhesives were fabricated via soybean meal (SM) and enhanced by tannic acid (TA) and polyetheylenimine (PEI) (TAPI) co-crosslinking network based on natural polyphenol-inspired chemistry. The multiple physico-chemical interactions (including intermolecular H-bonding and covalent bonding) between the TAPI co-crosslinking system and SM matrices were examined by the Fourier transform infrared spectroscopy, solid-state 13C nuclear magnetic resonance, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The results showed that a dense, robust, and water-resistant adhesive layer was constructed between network-bound catechol moieties in the TAPI and SM system, endowing the STP adhesive with high wet bonding strength for plywood. As expected, TAPI-modified SM adhesives showed a 156.1% increase in wet bonding strength compared to the control SM adhesive. The adhesion meets standard requirements for interior-use plywood. Both the solid content and residual mass analysis also confirmed that the enhancement in the STP adhesive was attributable to the network crosslinking density and stiffness after integrating the TAPI system. Moreover, the thermal stability of the resultant STP adhesive exhibited a significant improvement. The proposed STP adhesive may be a promising cost-effective and wet-resistant bio-adhesive for the application in the wood composites industry.

Molecular interactions in gelatin/chitosan composite films

Gelatin and chitosan were mixed at different mass ratios in solution forms, and the rheological properties of these film-forming solutions, upon cooling, were studied. The results indicate that the significant interactions between gelatin and chitosan promote the formation of multiple complexes, reflected by an increase in the storage modulus of gelatin solution. Furthermore, these molecular interactions hinder the formation of gelatin networks, consequently decreasing the storage modulus of polymer gels. Both hydrogen bonds and electrostatic interactions are formed between gelatin and chitosan, as evidenced by the shift of the amide-II bands of polymers. X-ray patterns of composite films indicate that the contents of triple helices decrease with increasing chitosan content. Only one glass transition temperature (T_g) was observed in composite films with different composition ratios, and it decreases gradually with an increase in chitosan proportion, indicating that gelatin and chitosan have good miscibility and form a wide range of blends.

Preparation and antibacterial properties of gelatin grafted with an epoxy silicone quaternary ammonium salt

Gelatin (GE) was modified with epoxy silicone quaternary ammonium salt (EPSiQA) under alkaline conditions (pH 10-11). Silyl and quaternary ammonium groups were linked to gelatin skeleton simultaneously. It was illustrated by XRD and DSC that the short-range order of GE is destroyed and the glass transition temperature (Tg) of GE drops 10 °C after modification. The measured contact angles and surface free energy calculated by Owens-Wendt equation showed that the surface energy of modified gelatin EPSiQA-GE is mainly contributed by the dispersive component of non-polarity silicone groups, the hydrophobility of EPSiQA-GE increases with the increase of grafted silicone units in gelatin. The results of minimum inhibitory concentration indicated that EPSiQA-GE has bactericidal property against Gram-positive bacteria, Gram-negative bacteria and has no antibacterial effect on mold.

Cutaneous biocompatible rutin-loaded gelatin-based nanoparticles increase the SPF of the association of UVA and UVB filters

The encapsulation of natural ingredients, such as rutin, can offer improvements in sun protection effectiveness. This strategy can provide enhanced flavonoid content and produces an improved bioactive compound with new physical and functional characteristics. As an alternative to common synthetic-based sunscreens, rutin-entrapped gelatin nanoparticles (GNPs) were designed and associated with ethylhexyl dimethyl PABA (EHDP), ethylhexyl methoxycinnamate (EHMC) and methoxydibenzoylmethane (BMDBM) in sunscreen formulations. The purpose of this study was to develop rutin-loaded gelatin nanoparticles and characterize their physicochemical, thermal, functional and safety properties. Rutin-loaded gelatin nanoparticles increased antioxidant activity by 74% relative to free-rutin (FR) solution. Also, this new ingredient upgraded the Sun Protection Factor (SPF) by 48%, indicating its potential as a raw material for bioactive sunscreens. The safety profile indicated that GNPs and glutaraldehyde (GTA) decreased HaCaT cell viability in a concentration/time-dependent manner. However, both blank nanoparticles (B-NC) and rutin-loaded nanoparticles (R-NC) had good performance on skin compatibility tests. These results functionally characterized rutin-loaded nanoparticles as a safe SPF enhancer in sunscreens, especially in association with UV filters.

Cold water fish gelatin modification by a natural phenolic cross-linker (ferulic acid and caffeic acid)

Nowadays use of edible films and coatings is increasing due to their biodegradability and environment friendly properties. Fish gelatin obtained from fish skin wastage can be used as an appropriate protein compound for replacing pork gelatin to produce edible film. In this study films were prepared by combination of fish gelatin and different concentration (0%, 1%, 3%, and 5%) of two phenolic compounds (caffeic acid and ferulic acid). The film was prepared at pH > 10 and temperature of 60˚c under continuous injection of O₂ and addition of the plasticizer sorbitol/glycerol. Results showed that solubility, oxygen permeability, and water vapor permeability were decreased for caffeic acid and the highest effect was observed at concentration of 5%. Solubility had a linear relationship with concentration of phenolic compound in film containing ferulic acid, however, no significant change was observed in vapor and O₂ permeability. A comparison between two phenolic compounds showed that caffeic acid had the highest effect in decreasing solubility, water vapor permeability, and oxygen permeability. Caffeic acid is more effective phenolic compound compared with Ferulic acid that can increase safety of biodegradable packaging by improving their barrier and physicochemical properties.

Investigating linear and nonlinear viscoelastic behaviour and microstructures of gelatin-multiwalled carbon nanotube composites

The linear and nonlinear rheology of physically-crosslinked-gelatin gel-multiwalled carbon nanotube (MWNT), chemically-crosslinked-gelatin gel-MWNT, and chemically–physically-crosslinked-gelatin gel-MWNT composites, are investigated.

Mechanical characterization of electrospun gelatin scaffolds cross-linked by glucose

Nanofibrous gelatin scaffolds were prepared by electrospinning from aqueous acetic acid and cross-linked thermally by glucose. The effect of the amount of glucose used as cross-linking agent on the mechanical properties of gelatin fibres was studied in this paper. The elastic modulus of gelatin fibres cross-linked by glucose was determined by modelling the behaviour of the meshes during tensile test. The model draws connections between the elastic moduli of a fibrous mesh and the fibre material and allows evaluation of elastic modulus of the fibre material. It was found that cross-linking by glucose increases the elastic modulus of gelatin fibres from 0.3 GPa at 0 % glucose content to 1.1 GPa at 15 % glucose content. This makes fibrous gelatin scaffolds cross-linked by glucose a promising material for biomedical applications.

Grafting of gallic acid onto chitosan enhances antioxidant activities and alters rheological properties of the copolymer

A new, simple, and effective method to graft gallic acid (GA) onto chitosan (CS) in aqueous solution in the presence of carbodiimide and hydroxybenzotriazole was developed. The grafting amount of GA reached as much as 209.9 mg/g of copolymer, which appears as the highest one among the reported literature, and the grafting degree of GA to CS was adjustable with modulation of the mass ratio of GA to CS. The covalent insertion of GA onto the polymeric backbones was confirmed by UV-vis and (1)H NMR analyses. Grafting endowed the resulting copolymer GA-grafted-CS (GA-g-CS) with both the advantages of CS and GA. The antioxidant capacity of GA-g-CS was much higher than that of the plain CS examined by assays of DPPH, superoxide, and ABTS radicals scavenging activities, reducing power, chelating power, inhibition of lipid peroxidation, ferric reducing antioxidant potential, and β-carotene-linoleic acid assays. Particularly, GA-g-CS showed significantly higher antioxidant activity than GA in β-carotene-linoleic acid assay. Furthermore, the viscosity of GA-g-CS was significantly higher than that of CS. The present study developed a novel approach to synthesize GA-g-CS that could be a potential biomaterial in food industries.

Functional properties and in vitro antioxidant and antibacterial effectiveness of pigskin gelatin films incorporated with hydrolysable chestnut tannin

The impact of the incorporation of 10% w/w of hydrolyzable chestnut tannin into pigskin gelatin (G) films plasticized with glycerol (Gly) on the physicochemical properties as well as the in vitro antioxidant and antibacterial effectiveness against food-borne pathogens such as Escherichia coli and Streptococcus aureus was investigated. A higher tendency to both redness (a*) and yellowness (b*) coloration characterized gelatin films incorporated with chestnut tannin. The reduced lightness (L) and transparency of gelatin–chestnut tannin films plasticized with 30% w/w Gly might be associated with certain degree of phase separation which provoked the migration of the plasticizer to the film surface. The incorporation of chestnut tannin and glycerol affected the chemical structure of the resultant films due to the establishment of hydrogen interactions between components as revealed by Fourier transform infrared spectroscopy. These interactions reduced gelatin crystallinity and seemed to be involved in the substantial decrease of the water uptake of films with tannin, irrespective of the glycerol level. Such interactions had minor effect on tensile properties being similar to those of the control films (without chestnut tannin) at the same glycerol level. Films modified with 10% w/w chestnut tannin showed significant (P < 0.05) 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity, ca. from 0 ± 0.033 to 87.1 ± 0.002% for chestnut tannin-free and chestnut tannin-containing gelatin films. The limited inhibitory activity of films incorporated with 10% w/w chestnut tannin against the selected bacteria evidenced by disk diffusion method probably resulted from the interactions within the film restricting the diffusion of the active agent into the agar medium. The more modest protective effect observed against a Gram-positive bacterium ( S. aureus) was also discussed.

Physico-chemical characteristics of gamma-irradiated gelatin

This article reports the effects of gamma irradiation (dose ranges 0.1–10 kGy from ⁶⁰Co source) on the characteristics of solid gelatin and the physico-mechanical, microstructural and bioactive properties of the scaffold prepared from irradiated gelatin solution. FTIR, intrinsic viscosity, bloom strength, thermal properties, SEM, tensile properties, water uptake ability and antimicrobial activities of non-irradiated and irradiated solid gelatin and its scaffolds were investigated. The detailed experimental results for the solid gelatin demonstrated that 1 kGy γ-irradiated samples showed higher intrinsic viscosity, enhanced thermal stability and bloom strength than other irradiated samples. Furthermore, the scaffold thus prepared from irradiated and non-irradiated gelatin also revealed that 1 kGy samples showed the highest tensile strength and modulus with good water resistivity than other irradiated and non-irradiated samples. In addition to the physico-mechanical properties, 1 kGy scaffolds have also exhibited the highest resistivity towards microbial growth that can have potentiality as scaffold in biomedical sector. The enhanced functional and bioactive properties at low irradiation doses (1 kGy) may occurred due to an initial breaking of hydrogen bonds of polypeptide chains in gelatin molecules that indicated by the shift of amide A, I and II peaks to higher wave numbers in FTIR. This enhancement resulted probably due to the domination of crosslinking over degradation at 1 kGy. It was also observed that 1 kGy γ-radiation-induced crosslinking has lowered the hydrophilicity by decreasing water uptake and mean pore diameter of the interconnected porous structures of gelatin.

Chemical Approaches in Processing Wheat Gluten-Based Polymer Materials

Processing wheat gluten-based renewable and biodegradable polymer materials through chemical modifications has been demonstrated as an effective way to improve the mechanical strength and modulus, material flexibility, barrier properties, and thermal processability, and to introduce new functionalities. Challenges still remain in further enhancing material properties, balancing hydrophilicity/hydrophobicity and biodegradability in the material, achieving a designed performance, and maintaining the material sustainability. A good understanding of protein structures, reactivity, and functionalities of wheat gluten is fundamental for such research and development, and a close collaboration between bio-chemists, polymer chemists, and material scientists is necessary for the approach.

Effects of oxygen and antioxidants on the lipid oxidation and yellow discolouration of film from red tilapia mince

BACKGROUND

Generally, biodegradable films from fish muscle protein become yellow after preparation. This discolouration is more likely associated with lipid oxidation and can be prevented by minimising the oxidation in the films. Thus, the effects of oxygen and antioxidants on lipid oxidation and yellow discolouration of film from red tilapia mince during storage were investigated.

RESULTS

Both films prepared at pH 3 and 11, and kept under atmosphere containing 100% N(2) had the lowest TBARS value with the concomitant lowest b* and ΔE* values during storage (P < 0.05), when compared with other films kept in air and a 100% O(2) atmosphere. Films prepared at pH 3 and incorporated with antioxidants (Trolox and catechin) at all levels (100, 200 and 400 mg L(-1) film-forming solution) had the lowest TBARS value, b* and ΔE* values during storage, indicating the retardation of lipid oxidation and yellow discolouration in films. Nevertheless, films prepared at pH 11 had no difference in TBARS values, in comparison with control film, regardless of antioxidant incorporation. Coincidentally, increases in b* and ΔE* values were observed in those films.

CONCLUSIONS

Lipid oxidation was the main factor inducing yellow discolouration of film exposed to oxygen and the incorporation of antioxidants in film prepared at acidic pH was able to prevent yellow discolouration of resulting film.

Cell adhesion and proliferation enhancement by gelatin nanofiber scaffolds

Gelatin nanofibers (GNs) prepared by electrospinning were cross-linked with glutaraldehyde vapor to improve their water-resistant ability. After cross-linking treatment, the form of the fibers expressed no substantial change, but the average diameter of the fibers increased with increasing cross-linking time. The swelling induced by the moisture during the cross-linking process was moderated when the cross-linking time reached 45 min. The contact angle measurements confirmed that the electrospun gelatin fibers were more hydrophilic than the gelatin film (GF). Increasing the cross-linking time did not alter the hydrophilic properties of the gelatin fibers. The cell compatibility was evaluated based on 3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay, scanning electron microscope and confocal microscope observations, and Western blot analysis by culturing MG-63 cells on the GFs and GNs. The nanofibrous structure fabricated by an electrospinning technique was found to enhance cell adhesion and proliferation. This process is a cost-effective simulation of GN structures’ promising applications on scaffold preparation for tissue engineering.

A review on composite liposomal technologies for specialized drug delivery

The combination of liposomes with polymeric scaffolds could revolutionize the current state of drug delivery technology. Although liposomes have been extensively studied as a promising drug delivery model for bioactive compounds, there still remain major drawbacks for widespread pharmaceutical application. Two approaches for overcoming the factors related to the suboptimal efficacy of liposomes in drug delivery have been suggested. The first entails modifying the liposome surface with functional moieties, while the second involves integration of pre-encapsulated drug-loaded liposomes within depot polymeric scaffolds. This attempts to provide ingenious solutions to the limitations of conventional liposomes such as short plasma half-lives, toxicity, stability, and poor control of drug release over prolonged periods. This review delineates the key advances in composite technologies that merge the concepts of depot polymeric scaffolds with liposome technology to overcome the limitations of conventional liposomes for pharmaceutical applications.

Mechanical properties of the beetle elytron, a biological composite material

We determined the relationship between composition and mechanical properties of elytra (modified forewings that are composed primarily of highly sclerotized dorsal and less sclerotized ventral cuticles) from the beetles Tribolium castaneum (red flour beetle) and Tenebrio molitor (yellow mealworm). Elytra of both species have similar mechanical properties at comparable stages of maturation (tanning). Shortly after adult eclosion, the elytron of Tenebrio is ductile and soft with a Young's modulus (E) of 44 ± 8 MPa, but it becomes brittle and stiff with an E of 2400 ± 1100 MPa when fully tanned. With increasing tanning, dynamic elastic moduli (E') increase nearly 20-fold, whereas the frequency dependence of E' diminishes. These results support the hypothesis that cuticle tanning involves cross-linking of components, while drying to minimize plasticization has a lesser impact on cuticular stiffening and frequency dependence. Suppression of the tanning enzymes laccase-2 (TcLac2) or aspartate 1-decarboxylase (TcADC) in Tribolium altered mechanical characteristics consistent with hypotheses that (1) ADC suppression favors formation of melanic pigment with a decrease in protein cross-linking and (2) Lac2 suppression reduces both cuticular pigmentation and protein cross-linking.