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Chemical and radiation modification of gelatin
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A prosthetic vascular graft that induces perigraft tissue incorporation may effectively prevent serious sequelae such as seroma formation and infection. Radiation-crosslinked gelatin hydrogel (RXgel) mimics the chemical and physical properties of the in vivo extracellular matrix and may facilitate wound healing by promoting tissue organization. Fibroblasts cultured on RXgel actively migrated into the gel for up to 7 days. RXgels of three different degrees of hardness (Rx[10], soft; Rx[15], middle; Rx[20], hard) were prepared, and small disc-like samples of RXgels were implanted into rats. In vitro and in vivo results indicated that Rx[10] was too soft to coat vascular grafts. Thus, expanded polytetrafluoroethylene (ePTFE) vascular grafts coated with RXgel were developed using Rx[15] and Rx[20] gels, and ring-shaped slices of the graft were implanted into rats. Alpha-smooth muscle actin (αSMA) and type III collagen (Col-III) levels were detected by immunohistochemistry. Immunohistochemical staining for αSMA and Col-III demonstrated that RXgel-coated vascular grafts induced more granulation tissue than non-coated grafts on days 14 and 28 after implantation. RXgel-coated ePTFE vascular grafts may provide a solution for patients by reducing poor perigraft tissue incorporation.
Magnetic Resonance Imaging (MRI) contrast agents with rapid renal excretion that do not penetrate the blood brain barrier (BBB) and blood cerebrospinal fluid barrier (BCFB) are preferred for safer and low-risk diagnosis. Gadolinium (Gd)-conjugated nanoparticles have been proposed for use as contrast agents; however, the particle size must range between 1 to 7 nm to ensure rapid renal excretion. In this study, three types of gelatin, dissolved in water at varying concentrations of 0.1–2 wt.%, were irradiated with 5 kGy γ-rays at 25°C under aerated conditions to produce ultra-small gelatin nanogels having an average particle size ranging between 6 ± 2 to 21 ± 4 nm. Ultra-small Gd-coordinated gelatin nanogels (GdGN) suitable for use as MRI contrast agents were produced using 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid mono-N-hydroxysuccinimide ester (DOTA-NHS) and DOTA-butylamine as Gd ligand derivatives. Non-cytotoxicity and effective relaxivity of GdGN as a positive MRI contrast agent were verified using in vivo experiments. Rapid renal excretion of GdGN was observed in mice within 1 h with no accumulation in the liver. GdGN did not migrate across the BCFB in normal mice, thus emphasizing its safety as an MRI contrast agent.
This review begins with a discussion of the general properties of gelatin and its sources, particularly in the food and health industries, and then briefly address the status quo of gelatin in today's market. Apart from the basic chemical compounds and gelatin types, this paper also discussed the commercialisation of gelatin. This study also highlights the production of conventional gelatin and its current method of processing, i.e. enzymatic hydrolysis. In addition, the variety of raw materials of collagen is outlined and briefly broached the plant hydrocolloids which have been labeled as 'veggie-gelatin'. With regard to the potential and market stability of gelatin, its recent studies are summarised in this paper. Accordingly, this paper focuses on assessing the general utilities of the various sources of collagen as gelatin derivatives. At that basis, the aim of this review is to provide an insight into gelatin in current applications , market value and progress in gelatin extraction.
Background
Studies indicate a 30% increase in demand for all types of food and non-food grade gelatins in the world. The largest volume of gelatin production comes from mammal sources (cows and pigs). Nowadays, health, cultural, and religious concerns have arisen due to consumption of mammalian gelatin. This has prompted scientists to look for non-mammal sources that closely resembles the desirable physicochemical, functional, and sensory characteristics of mammalian gelatins. Non-mammalian gelatin from poultry and fish by-products are also gaining importance in food industry. Over the past decade, poultry production has increased by about 37.34%. Poultry by-products have good potential for replacing mammalian sources for gelatin extraction.
Scope and approach
This paper reviews in detail the fundamental properties of poultry gelatins (PG), including rheological, functional and physicochemical properties. This study provides a perspective on their potential food, pharmaceutical, medical and industrial applications.
Key findings and conclusions
The highest quality PG was extracted through acid treatments. PG extracted in this way exhibited favorable rheological, fat replacement, film formation, foaming, emulsifying and sensory properties, and nutritional quality. PG films showed better barrier properties than mammal-origin gelatin, making them ideal for food and medical applications. The amino acids composition of PG, especially the imino acid and hydrophobic amino acids, which determine the physicochemical and functional properties of gelatin, are higher than gelatin obtained from mammals and fish that classifies them in the upper Bloom category.
Pathogenic bacterial infection, especially in the wound, may threaten human health. Developing new antibacterial materials for wound healing is still urgent. Metal nanoclusters have been explored as a novel antibacterial agent. Herein, biomolecule gelatin was chosen as a substrate and functionalized with gold/silver clusters for bacterial killing. Through a simple amidation reaction, gold/silver clusters were successfully conjugated in gelatin substrate to obtain Au/Ag@gelatin sponge. The presence of gold/silver clusters modified the porous structure of gelatin, and thus the water absorption and water retention of Au/Ag@gelatin sponge were enhanced. More importantly, the gold/silver clusters show aggregation-enhanced emission and strong reactive oxygen generation, that endow Au/Ag@gelatin sponge good antibacterial property. The good physical performance and favorable bactericidal activity of Au/Ag@gelatin sponge suggest their potential for applying as a wound dressing.
In order to investigate the effect of glutaraldehyde (GTA) on the structure, mechanical properties and thermal stability of gelatin films, gelatin films modified by GTA at various pH (4.5, 6.5, and 11), were prepared. According to FTIR analysis, the reaction mechanism between GTA and gelatin was different at various pH. With the addition of GTA, the intermolecular forces (hydrogen bonds and ionic bonds) and triple helix structure of gelatin film were significantly disrupted. At pH 4.5, gelatin films modified by GTA showed the highest mechanical properties and thermal stability among all films, which tensile strength and residues in TGA up to 16.13 MPa and 15.05%, respectively. Therefore, an optimum pH was around 4.5 in gelatin films cross‐linked by GTA. The reaction mechanism between glutaraldehyde (GTA) and gelatin was adjusted by pH. pH affected mechanical properties, thermal stability, and triple helix content of the gelatin films with GTA. An optimum pH was around 4.5 in gelatin films cross‐linked by GTA to improve the physical properties of gelatin films.
Electrospinning is an exceptional technology to fabricate sub-micrometric fiber scaffolds for regenerative medicine applications and to mimic the morphology and the chemistry of the natural extracellular matrix (ECM). Although most synthetic and natural polymers can be electrospun, gelatin frequently represents a material of choice due to the presence of cell-interactive motifs, its wide availability, low cost, easy processability, and biodegradability. However, cross-linking is required to stabilize the structure of the electrospun matrices and avoid gelatin dissolution at body temperature. Different physical and chemical cross-linking protocols have been described to improve electrospun gelatin stability and to preserve the morphological fibrous arrangement of the electrospun gelatin scaffolds. Here, we review the main current strategies. For each method, the cross-linking mechanism and its efficiency, the influence of electrospinning parameters, and the resulting fiber morphology are considered. The main drawbacks as well as the open challenges are also discussed.
A novel approach is developed for preparing a highly porous super absorbent hydrogel (SAH). Synthetic and natural hydrogel based acrylamide (Am) and gelatin (G) were polymerized and crosslinked by gamma radiation. Three hydrogels compositions have been prepared in weight ratio 1:2, 1.5:1.5 and 2:1 (wt:wt) for 30% PAAM/G and exposed to gamma radiation at dose of 30 kGy. The effect of chemical modifications on increasing the swelling power of polyacrylamide gelatin (PAAM/G) has been evaluated. The alkaline hydrolysis of PAAM/G hydrogel with concentrated NaOH converts amid groups CONH2 to carboxylic groups COONa. The modified hydrogels will take the codes PAAM-COOH/G, PAAM-COONa/G and PAAM-COOK/G that dramatically increased the degree of swelling from 220 to 720 (g/g). Furthermore, studies on the slow release ability of three kinds of fertilizer (K, P and urea) loaded on modified PAAM-COOH/G and evaluated the ability of SAH hydrogels to absorb and then gradually release water and fertilizer. A mathematical model for fertilizer release from PAAM-COOK/G was applied to calculate the diffusion coefficient D. The main aim of this article is performed the effect of soil amendment with PAAM-COOK/G on eliminating water stress was tested for bean plant (Vicia faba) irrigation cycles in drought-prone environments. The growth of bean plant was monitored by measuring the highest and size of leaves and bean seed. The effect of water stress was monitored also, by measuring the intensity of chlorophyll for both SAH and control soil. The results indicated that the chemical modification of (PAAM/G) into (PAAM-COOK/G) could greatly improve water absorbency. The experimental data indicated that the SAH has a positive effect to use as fertilizers carrier and soil conditioner. © 2018 Springer Science+Business Media, LLC, part of Springer Nature
Background
Crosslinked gelatin nanofibers are one of the widely used scaffolds for soft tissue engineering. However, modifying the biodegradation rate of chemically crosslinked gelatin is necessary to facilitate cell migration and tissue regeneration. Here, we investigated the optimal electron beam (e-beam) irradiation doses with biodegradation behavior on changes in the molecular weight, morphology, pore structure, and cell proliferation profiles of electrospun nanofibrous gelatin sheets.
Methods
The molecular weights of uncrosslinked gelatin nanofibers were measured using gel permeation chromatography. The morphology and pore structure of the gelatin scaffolds were analyzed by scanning electron microscopy and a porosimeter. Biodegradation tests were performed in phosphate-buffered saline solutions for 4 weeks. Cell proliferation and tissue regeneration profiles were examined in fibroblasts using WST-1 assays and hematoxylin and eosin staining.
Results
Crosslinked gelatin nanofiber sheets exposed to e-beam irradiation over 300 kGy showed approximately 50% weight loss in 2 weeks. Gelatin scaffolds exposed to e-beam irradiation at 100–200 kGy showed significantly increased cell proliferation after 7 days of incubation.
Conclusions
These findings suggested that the biodegradation and cell proliferation rates of gelatin nanofiber scaffolds could be optimized by varying e-beam irradiation doses for soft tissue engineering.
The mechanical, thermal, swelling, and release properties of chitosan-gelatin (CG) films have been investigated in order to verify the influence of UV and gamma radiation on the stability of the films. Thin films of chitosan and gelatin (1 : 3, w/w) that were radiated with 100 krad of gamma dose showed the best performance and the TS values reached 25, 45, and 49 MPa, respectively, for chitosan, gelatin, and blend. The corresponding highest TS values were 23, 42, and 45 MPa, respectively, for 10 passes of UV radiation. The effect of radiation over gelatin, chitosan, and CG blend caused modification in the arrangement of molecules in the crystal lattice that is significant by XRD analysis. Surfaces of the films were also investigated by scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) studies further revealed structural changes of the films. These changes were attributed to understanding the behavior of the irradiated chitosan, gelatin, and CG blend on application of thermal energy using DSC and TGA studies, water uptake of the films in aqueous medium, and soil degradation properties to observe the best possibility for its application.
Background:
Hydrogels can serve as three-dimensional (3D) scaffolds for cell culture and be readily injected into the body. Recent advances in the image technology for 3D scaffolds like hydrogels have attracted considerable attention to overcome the drawbacks of ordinary imaging technologies such as optical and fluorescence microscopy. Multiphoton microscopy (MPM) is an effective method based on the excitation of two-photons. In the present study, C2C12 myoblasts differentiated in 3D gelatin hydroxyphenylpropionic acid (GHPA) hydrogels were imaged by using a custom-built multiphoton excitation fluorescence microscopy to compare the difference in the imaging capacity between conventional microscopy and MPM.
Results:
The physicochemical properties of GHPA hydrogels were characterized by using scanning electron microscopy and Fourier-transform infrared spectroscopy. In addition, the cell viability and proliferation of C2C12 myoblasts cultured in the GHPA hydrogels were analyzed by using Live/Dead Cell and CCK-8 assays, respectively. It was found that C2C12 cells were well grown and normally proliferated in the hydrogels. Furthermore, the hydrogels were shown to be suitable to facilitate the myogenic differentiation of C2C12 cells incubated in differentiation media, which had been corroborated by MPM. It was very hard to get clear images from a fluorescence microscope.
Conclusions:
Our findings suggest that the gelatin-based hydrogels can be beneficially utilized as 3D scaffolds for skeletal muscle engineering and that MPM can be effectively applied to imaging technology for tissue regeneration.
Graft copolymerization of acrylamide (AM) and methyl acrylacyl oxyethyl trimethyl ammonium chloride (DMC) onto gelatin under microwave radiation was studied. The resultant ternary graft copolymer was used as wood pulp dry-strengthening agent. The application results showed that the optimum synthesis conditions was that microwave radiation power was 500W, microwave radiation time was 120S, the concentration of CAN(initiator) was 3mmol/L, m(CS): m(AM): m(DMC) =1:6:2. The breaking length and broken index of hand sheet made of wood pulp was respectively increased by 24.5% and 22.3% when the dosage of the graft copolymer was 0.8% of dry fiber weight.
A series of poly (vinyl) alcohol/gelatin copolymer (PVA/Gel) with different entrapped carotene (Carot) concentration into the films has been devised. The films were irradiated with γ-rays at dose levels of 10, 50, 100, 150 and 250 kGy. The crystalline and chemical structures of the samples have been studied using XRD and FTIR techniques. The direct current electrical conductivity (σDC) has been determined from the proposed sampling before and after gamma exposure. It is clearly demonstrated that the electrical conductivity of PVA/Gel/Carot films was increased from two to three orders of magnitude due to carotene doping, and decreased one order of magnitude due to gamma radiation. The obtained results can be attributed to the existence of the conjugated double bonds in the aliphatic side chain of the carotene molecule. Thus, this work suggests the possibility of the use of the gamma irradiated PVA/Gel/Carot films in different electronic applications.
Gelatin-PVA blend films of different compositions (0%, 5%, 10%, 15% of PVA) were prepared by casting. The tensile strength (TS) and elongation at break (Eb) of the films were studied. The TS and Eb of pure gelatin films were found to be 32 MPa and 3.3% respectively. The films were irradiated under different gamma radiation dose (50 Krad, 100 Krad, 150 Krad, 250 Krad, 500 Krad). 5% PVA containing gelatin films irradiated under 100 Krad gamma radiation showed highest TS of 42 MPa and highest Eb of 4.2%. Thermal property of the films was studied by Thermomechanical analysis (TMA) and Thermogravimetric Analysis (TGA). The grafting of PVA onto gelatin is studied by IR. In order to study surface morphology SEM study was undertaken.
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.
Gelatin films were prepared by dissolving gelatin granules in hot distilled water (90°C) followed by casting. Tensile strength (TS), tensile modulus (TM) and elongation at break (Eb %) of the films were found to be 27.0 MPa, 100 MPa and 4%, respectively. Gelatin films were irradiated under Co-60 source at different doses (50-1000 krad) and it was found that TS and TM of the films increased up to 48% and 120%, respectively at 250 krad dose. Urea (1–5 wt%) was added to the gelatin solution and films were prepared by casting, then irradiated and found that TS of the 2% urea containing gelatin film was 44.3 MPa which is about 64% enhancement of TS compared to raw gelatin films at 100 krad. Gelatin-urea films were then soaked in 1–10 wt% of EHA (2-Ethylhexyl acrylate) solutions at varying soaking time and irradiated under gamma radiation up to 500 krad. The highest TS and Eb were found to be 57 MPa and 11%, respectively for the 3% EHA and 3 min soaking time at 100 krad radiation dose.
Gelatin films were prepared from gelatin granules in aqueous medium by casting. Tensile strength, tensile modulus, elongation at break and the glass point of the gelatin films were found to be 27 MPa, 100 MPa, 4% and 51.7°C, respectively. After irradiated with gamma radiation tensile properties were increased due to denser network structure. Gelatin films were soaked in five different formulations containing 2-hydroxyethyl methacrylate (HEMA) (10–50%, by wt), methanol and photoinitiator and then irradiated under gamma radiation. Again, a series of gelatin solutions was prepared by blending varying percentages (10–50% by wt) of HEMA and then films were prepared and irradiated under gamma radiation. It was found that tensile and thermal properties of gelatin films improved significantly.
In this study, the gelatin crosslinked by Transglutaminase (TG) was applied to stabilize food-grade high internal phase emulsions (HIPEs) by a facile one-step method. The influence of TG crosslinking time on the molecular weight distribution of gelatin and the microstructure, thermal stability and rheological properties of the HIPEs were investigated. The results showed that TG crosslinking effectively promoted the production of high weight molecular. The obtained HIPEs exhibited a uniform droplet diameter and a good storage stability. An excellent thermal stability was achieved among the HIPEs stabilized by TG-crosslinked gelatin. After heating at 90 °C and 121 °C for 20 min, there was little change in microstructure and viscosity when the crosslinking time reached 4 h, implying that it could be stored at room temperature through high temperature sterilization. In the rheological analysis, the HIPEs showed a higher viscosity and lower frequency dependence with the extension of the crosslinking time, suggesting its potential application in three dimensional (3D) printing. The subsequent 3D printing experiments also confirmed that the HIPEs had a good printing performance, and some 3D printing models with different colors could be successfully obtained. This study provides a facile industrialized method for gelatin-based HIPEs with high thermal stability, and supplies theoretical guidance for its practical application.
The potential of a radiation crosslinking technique for developing gelatin scaffolds for tissue engineering was evaluated by comparing it with a chemical crosslinking method. Radiation-crosslinked gelatin exhibited higher visible light transmittance as compared to chemically crosslinked gelatin. The radiation crosslinking efficiency of the gelatin was estimated to be 91%; it was affected by hydroxyl (OH) radicals formed by γ-radiolysis of the aqueous gelatin solution under nitrous oxide or nitrogen-saturated conditions. The proportions of phenylalanine, tyrosine, and histidine in the gelatin decreased significantly with increasing absorbed dose. At the same time, the amounts of 12 other amino acids remained almost unchanged after γ-ray irradiation, and these amino acids did not participate in the crosslinking reactions. The contents of tyrosine, phenylalanine, and histidine in gelatin were the most important factors for radiation crosslinking. Cell adhesion of the radiation-crosslinked gelatin would be maintained before and after γ-ray irradiation because there was no decrease in the proportion of the cell adhesion active sequence (arginine-glycine-aspartic acid, RGD motif). The yield for dityrosine formation was estimated to be 0.030 mol l⁻¹ Gy⁻¹, and this is considered to be the point at which crosslinking occurred in the radiation-crosslinked gelatin. As the crosslinked gelatin and degradation products have no absorption bands in the visible region, the radiation crosslinking technique, unlike chemically crosslinking techniques, can modify the gelatin while maintaining high transparency.
Gelatin is used in a broad range of tissue engineering applications because of its bioactivity, mild processing conditions, and ease of modification, which have increased interest in its use as a growth factor delivery vehicle. Traditional methods to control growth factor sequestration and delivery have relied on controlling hydrogel mesh size via chemical crosslinking with corollary changes to the physical properties of the hydrogel. To decouple growth factor release from scaffold properties, affinity sequestration modalities have been developed to preserve the bioactivity of the growth factor through interactions with the modified gelatin. This review provides a summary of these mechanisms, highlights current gelatin growth factor delivery systems, and addresses the future perspective of gelatin matrices for growth factor delivery in tissue engineering.
We report a water-soluble and non-toxic method to incorporate additional extracellular matrix proteins into gelatin hydrogels, while obviating the use of chemical crosslinkers such as glutaraldehyde. Gelatin hydrogels were fabricated using a range of gelatin concentrations (4%-10%) that corresponded to elastic moduli of approximately 1 kPa-25 kPa, respectively; a substrate stiffness relevant for multiple cell types. Microbial transglutaminase was then used to enzymatically crosslink a layer of laminin on top of gelatin hydrogels, resulting in 2-component gelatin-laminin hydrogels. Human induced pluripotent stem cell derived-neurospheres readily adhered and rapidly extended axons on GEL-LN hydrogels. Axons displayed a more mature morphology and superior electrophysiological properties on GEL-LN hydrogels compared to controls. Schwann cells on GEL-LN hydrogels adhered and proliferated normally, displayed a healthy morphology, and maintained expression of Schwann cell specific markers. Lastly, skeletal muscle cells on GEL-LN hydrogels achieved long-term culture for up to 28 days without delamination, while expressing higher levels of terminal genes including myosin heavy chain, MyoD, MuSK, and M-Cadherin suggesting enhanced maturation potential and myotube formation compared to controls. Future studies will employ the superior culture outcomes of this hybrid substrate for engineering functional neuromuscular junctions and related organ on a chip applications.
Herein the construction of a strong gelatin hydrogel is presented by using pullulan dialdehyde (PDA) as a macromolecular crosslinker. The resultant PDA crosslinked gelatin hydrogels (G-PDA) exhibit extremely high mechanical strength, manifested in the achieved optimal compressive stress of 5.80 MPa at 80% strain, which is up to 152 times higher than pure gelatin hydrogel. The G-PDA were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The extent of crosslinking was determined by ninhydrin assay. The results suggested that the synergistic effect of dual-crosslinking, which is composed of short- and long-range covalent crosslinking and thermoreversible physical crosslinking, may played a key role in enhancing the load-bearing capacity of ensuing hydrogels. The swelling and enzymatic degradation of G-PDA are gradually limited with increasing PDA concentration. The result from MTT assay demonstrated that G-PDA is non-cytotoxic against MC3T3 cells, regardless of the concentrations of PDA.
Crosslinking a gelatin layer with formaldehyde gives a decrease in swelling and solubility as function of the reaction time and the pH value. The molecular weight distribution of the crosslinked gelatin is determined by gelchromatography, the average molecular weight by sedimentation in the ultracentrifuge and the helical content by means of circular dichroism. In the reaction process, the average molecular weight Mw as well as the amount of gelatin molecules with M ≤ 10.106 increase, while the material of M ≈ 105 decreases. The formation of helix is hindered by crosslinking with formaldehyde. The cross-linking in solution is intercatenar as well as intracatenar.
Résumé
La réticulation d´une couche de gélatine par addition de formaldehyde réduit son gonflement et sa solubilité, l´éffet dependant simultanément de la durée de la réaction et du pH.
Les courbes de distribution de gélatines réticulées sont determinées par chromatographie sur gel, des masses molécularies Mw par ultra oontrifugation et les taux d´helicité par dichroisme circulaire.
A la réticulation de la gélatine les masses moleculaires moyennes s´agrandissent, la hauteure du maximum de la courbe de distribution diminue et il se forme des molécules ayant une masse moléculaire M supérieure ou égale à 10.106.
La formation hélice est empêchée par la réticulation de la gélatine avec formaldehyde. Il a été trouvé d’apres la relation viscosité- masse moléculaire que le tannage en solution forme aussi bien des ponts intra qu´interchaînes.
Zusammenfassung
Die Vernetzung einer Gelatineschicht mit Formaldehyd führt zur Verminderung von Quellfaktor und Löslichkeit in Abhängogkeit von Reaktionszeit und pH-Wert.
Die relative Molekulargewichtsverteilung der vernetzten Gelatine wird mit Hilfe der Gelchromatographie, das mittlere Molekulargewicht ou durch Sedimentation in der Ultrazentrifuge und der Helixanteil aus Messungen des Circulardichroismus ermittelt.
Bei der Vernetzungsreaktion steigt sowohl das mittlere Molekulargewicht Mw, als auch der Anteil an Gelatinemolekülen mit Molekulargewichten M ≥ 10.106 än, während der Anteil an Molekülen mit einem Molekulargewicht von MTI0 abnimmt.
Die Helixbildung wird infolge der Vernetzung mit Formaldehyd behindert. Aus Viskositäts- und Molekulargewichtsmessungen folgt, is die Vernetzung in Lösung sowohl intra- als auch intercatenar erfolgt.
Riassunto
I legami incrociati cui la formaldeide da luogo in strati di gelatina, portano ad una diminuzione del rigonfiamento e della olubilitá, entrambe in funzione del tempo di reazione e del valore di pH.
La determinazione della distribuzione dei pesi molecolari in soluzioni di gelatina con numero parziale di crosslinking con formaldeide Co determinato per mezzo della gelcromatografia, il peso molecolare medio viene determinato mediante ultracentrifugazione, mentre il contenuto di struttura elicoidale mediante misure di dicróimo circolure.
Durante la reazione della gelatina con la formaldeide aumenta il peso molecolare medio Mw, cosí pure la percentuale delle molecule i. un peso molecolare di M ≥ 10.106, mentre la percentuale delle molecole con un peso molecolare di cir≈cas 105 dimuisce. La formazione a Struttura elicoidale viene disturbata dai legami incrociati cui la formaldeide da luogo. In solutione sono i legami incrociati sia intracatenar ooi come intercatenar.
The cross-linking reaction was followed by measuring the horizontal and vertical swelling (water absorption) of the layers. It was found that the cross-linking of the gelatin with hardener could be adequately described as a pseudofirst-order reaction:
EH, Q = a + b*e-kt
where EH - horizontal swelling Q - vertical swelling a - swelling after full hardening b - variable component of the swelling k - rate constant t - time
Various influences on the size of the rate con- slant are described: gelatin concentration concentration of anionic wetting agents molecular weight distribution of the gelatin surface temperature of the film point of time addition of the hardener type of hardener
The gelatin films were coated on production coalers with reproducible parameters of chilling and drying.
The low molecular weight component of gelatin has been investigated by determination of the molecular weight distribution of the sol fraction from hardened gelatin films. The hardeners used were formaldehyde and mucochloric acid. Different hardening conditions and gelatin types were studied. It was observed that a couple of weeks were needed to reach a stable level of hardening. Acid- processed gelatins exhibited higher reactivity than lime-processed gelatins. The results indicate that the method seems to be effective as an evaluation of gelatin hardening.
Earlier kinetic studies of the crosslinking of gelatin by formaldehyde and glyoxal gave consistent relationships for the concentration dependence of the reactants. These however required the postulation of more complex chemistry than had been envisaged. Studies of tilt1 stoichiometry of these and a range of other hardening agents, showed a wide range of molecular efficiencies that did not correlate with the rates of reaction.
Kinetic studies have now been extended to higher dialdehydes (Succinaldehyde, glutaraldehyde, 3- methylglutaraldehyde) and other crosslinking agents (2, 3-dihydroxy-l, 4-dioxane, 1, 3-bis- (vinylsulplumylmethyl) ether). The results again show consistent patterns of behaviour dependent on relatively complex chemistry. Some explanations for the mechanisms involved are advanced together with separate supporting chemical evidence.
It has long been recognized that the solubility and coagulation characteristics of chemically modified gelatins can be exploited by emulsion manufacturers for the purpose of washing and concentrating silver halide emulsions. In order to study these characteristics, it has generally been necessary to precipitate silver halide grains in the presence of the chemically modified gelatin to provide a substrate for the coagulation. A more convenient test system has been developed that uses a readily available material (barium sulphate) to mimic silver halide grains and provide a reproducible substrate for coagulation. This test system has been used to study various aspects of the coagulation process and their relationship to properties of phthalic anhydride (PA) modified gelatins. The coagulation properties (or solubilities) of PA gelatins were found to be a non-linear function of the degree of modification. Molecular weight distribution was found to be a secondary factor in solubility.
Gelatin is an insoluble protein obtained by hydrolysis of collagen, a basic structure of animal bodies including the skin, tendons, bones, and connective tissues. There are few types of gelatin sources such as mammalian (pig and cow), marine including fish (warm- and cold-water) and squid, poultry (chicken, birds, and ducks), and insect sources. The properties and functionality of gelatin depend on the type of collagen, sources, ages of animal, processes, etc., due to the different contents of amino acids and molecular weight distribution. This significant hydrocolloid has wide applications in cosmetic, pharmaceutical, photography, and food industries.
Chitosan (CS)/Gelatin (Gel)/Polyvinyl alcohol (PVA) hydrogels were prepared by the gamma irradiation method for usage in wound dressing applications. Chitosan and gelatin solution was mixed with poly(vinyl alcohol) (PVA) solution at different weight ratios of CS/Gel of 1:3, 1:2, 1:1, 2:1and 3:1. The hydrogels irradiated at 40 kGy. The structure of the hydrogels was characterized by using FT-IR and SEM. The CS/Gel/PVA hydrogels were characterized for physical properties and blood clotting activity. The tensile strength of CS/Gel/PVA hydrogel enhanced than on the basis of the Gel/PVA hydrogel. The highest tensile strength reached the 2.2 Mpa. All hydrogels have shown a good coagulation effect. It takes only 5 minutes for the BCI index to reached 0.032 only 5 minutes when the weight ratio of CS/Gel was 1:1. It means that the hemostatic effect of hydrogels were optimal. And the hydrogrls also showed good pH-sensitivity, swelling ability and water evaporation rate. Therefore, this hydrogel showed a promising potential to be applied as wound dressing.
Research over the past decade on the cell-biomaterial interface has shifted to the third dimension. Besides mimicking the native extracellular environment by 3D cell culture, hydrogels offer the possibility to generate well-defined 3D biofabricated tissue analogs. In this context, gelatin-methacryloyl (gelMA) hydrogels have recently gained increased attention. This interest is sparked by the combination of the inherent bioactivity of gelatin and the physicochemical tailorability of photo-crosslinkable hydrogels. GelMA is a versatile matrix that can be used to engineer tissue analogs ranging from vasculature to cartilage and bone. Convergence of biological and biofabrication approaches is necessary to progress from merely proving cell functionality or construct shape fidelity towards regenerating tissues. GelMA has a critical pioneering role in this process and could be used to accelerate the development of clinically relevant applications.
In this research, we synthesized a novel graft copolymer of gelatin-based via radical polymerization mixtures Acrylic acid (AcA) and Acrylamide (AAm) onto gelatin backbones. The polymerization reaction was carried out in an aqueous medium and in the presence of ammonium persulfate (APS) as an initiator. Evidence of grafting was obtained by comparing FTIR and TGA analysis of CMC and the graft copolymer as well as solubility characteristics of the products. The effect of grafting variables, i.e. concentration of AAm, AcA, APS and Gelatin, and temperature was systematically optimized to achieve a highest percent grafting possible. The overall activation energy for the grafting was also estimated to be 23.30kJ/mole.
Functionalization of microcrystalline cellulose (MCC) with EDTA dianhydride (EDTAD) was first achieved using an esterification reaction. N-Hydroxysuccinimide-activated MCC-EDTAD ester (MEN), a novel macromolecule crosslinker based on MCC, was synthesized for the modification of gelatin films. The reaction between gelatin and MEN was verified by the residual free amino test, FTIR and XRD spectra. The introduction of MEN into gelatin decreased the film degradation ratio and increased its thermal stability, flexibility, hydrophobicity, light barrier performance and water uptake ability. Additionally, SEM images proved the successful surface grafting reaction and degradation phenomenon. This unique gelatin film material with advanced properties broke the limitation of the blending method for modification of gelatin with macromolecules and broadened its application as a novel sustained-release material. This journal is
This research was to study the effects of gelatin content variation and gamma radiation after the 2-ethylhexyl acrylate (EHA) pre-treatment on the foundamental properties of gelatin film laminated polycaprolactone (PCL) biocomposites. PCL/gelatin film (PCL/GF) composites were fabricated by compression molding and their properties were studied by physico-mechanical, thermomechanical, thermal and degradation properties. The results from mechanical properties such as tensile modulus and impact strength of the composites increased with increasing of gelatin content up to 10 wt% and then decreased while the tensile strength and elongation at break decreased. EHA monomer (2–8 wt%) was added to the gelatin solution and films were prepared by casting and found to increase the mechanical properties of the PCL/EHA blended gelatin film (PCL/EGF) composites. Treatment of the gelatin film with gamma radiation after the EHA pre-treatment showed the best mechanical properties of the resulting composites. Dynamic mechanical thermal analysis results showed that the storage modulus of the PCL/EGF and PCL/EHA blended gelatin film with gamma radiation (PCL/GEGF) composites was increased significantly. The degradation properties in water and soil were determined for the non-irradiated and irradiated composites. It was observed that the non-irradiated composite degrades more than that of the irradiated composites.
Gelatin is used in various biological and medical fields, including drug delivery systems and tissue engineering. In the context of these applications, radiation sterilization of gelatin was evaluated in terms of radiation stability. The molecular weight of gelatin powder irradiated by electron beams (EB) was analyzed using gel permeation chromatography (GPC). We found that irradiation decomposed the gelatin and that the weight-averaged molar mass (Mw) decreased by approximately 7–10% with sterilization doses in the range of 5–25 kGy. Also, we found that the hydrolysis rate in body and cell culture environments (37 °C water) was affected by irradiation. Although gelatin powder underwent chain scission when irradiated, crosslinking was predominantly induced when the gelatin was irradiated in water solution. Radiation-crosslinked (RX) gelatin hydrogel was fabricated without using any crosslinkers. In this case, fabrication and radiation sterilization were performed simultaneously. Using gel fraction and GPC analysis of the eluted sol, it was determined that the RX-gelatin hydrogel was stable for 7 days in water at 37 °C. These results provide important data for evaluating the feasibility of biological and medical applications of gelatin and RX-gelatin hydrogel.
Chemical modifications of gelatin from New Zealand hoki (Macruronus novaezelandiae) skins were carried out using three different cross-linking agents, namely, genipin, glutaraldehyde and caffeic acid, at different concentrations. The chemically modified gelatins exhibited better physical properties, such as higher gel strength, melting point, and rheological properties than did the uncross-linked gelatin. Gelatin cross-linked with glutaraldehyde had higher gel strength and melting point (231 g, 21.9 °C) than those cross-linked with caffeic acid (229 g, 21.6 °C) and genipin (211 g, 20.5 °C) at concentrations of 0.133, 0.111, and 0.044 M, respectively. The elastic modulus (G′) and the loss modulus (G″) of chemically cross-linked gelatins were higher than those of the uncross-linked ones. These improved physicochemical properties of gelatin could lead to the development of products in the food industry that meet consumer demands.
Grafting of gelatin with acrylonitrile in zinc chloride medium has been studied using potassium persulfate as the initiator. The rate of grafting, grafting efficiency, and percentage of grafting are calculated. The grafting results are discussed in the light of the rate of grafting. The enhanced activity of the monomer is due to the formation of AN … ZnCl2 complexes.
Gelatin hydrogels with various concentrations were cross-linked by the irradiation with 60Co γ-rays, and we investigated the radiation-induced cross-linking of gelatin hydrogels by estimating the physical properties of irradiated hydro-gels. In case of the 1, 5, and 10% (w/v) gelatin solutions, the specific water content of the irradiated hydrogels, the index showing the extent of cross-linking depended on the absorbed dose, and that of the irradiated gelatin hydrogels with the lower concentration decreased drastically. The breaking strength correlated to the absorbed dose, irrespective of the initial gelatin concentration. More than 8kGy irradiation induced insolubility due to the cross-linking of the gelatin hydrogels. Besides, γ-ray irradiation to gelatin with free amino acids revealed that amino acids, which have side chains of hydrocarbon groups that are more than two carbon atoms, obstructed the cross-linking of gelatin hydrogels. It is thought that the hydrocarbon groups, such as an alkyl or a phenyl group of the side chains, are the cross-linking sites of gelatin hydrogels.
The processes of regeneration of collagen-like structure were studied during gelation of gelatin in irradiated systems (thermically unsoluble and soluble gels) by the methods of measuring the optical rotation changes and of measuring the viscosity (η) and density (ρ{variant}) product value of the system. The kinetics of mutarotation process was considered as a simple transition of coil→helix and the order of this reaction was established to be n=3 both for unirradiated gelatin and for radiation modified systems. A complex process of re-formation of collagen-type structure was considered as a sum of three parallel first order reactions. The constant rates of these reactions κ1, κ2 and κ3 are independent of the degree of radiation crosslinking of gelatin system. From these studies it has been concluded that the irradiated gelatin does not change the kinetics of re-formation of collagen-like structure. The contents of this structure decreases both in gelatin irradiated in solution and in the form of gel.
The denaturation of soluble collagen is shown to consist of two consecutive reactions. The first step is a breakdown of the helical, rodlike structure of the collagen molecule as indicated by the rapid decrease of the angular dependence of light scattering and of optical rotation and viscosity. The second step is a slower dissociation into smaller components which can be followed by the decrease of the molecular weight as measured by light scattering.In the so-called renaturation process of collagen, less than 10% of the denatured collagen forms rodlike native molecules under the conditions studied here. This is indicated by the negligible increase in the angular dependence of light scattering. The peptide chains seem to form aggregates with a low degree of asymmetry but with a structure which is, in certain of its features, very similar to native collagen as indicated by the high optical rotation and the same final melting temperature. The term renaturation in its literal meaning seems misleading.
THE dilute-solution viscosity method, which has been so successfully used for high polymers, has rarely been employed in studies of protein solutions, even where there is reason to expect a markedly anisodimensional molecular shape1. The following results have been obtained on the dilute-solution viscosity of gelatin, as part of a programme of work on the molecular weight and molecular weight distribution. The reduced viscosity (1c·loge(ηr)) of very dilute ash-free2 solutions of gelatin (gelatin concentration 0.20 per cent and less) have been measured as a function of pH (range pH 0.50–12.5) and concentration of added electrolyte (range zero to 1.00 M sodium chloride) at 35.0° C. in standard U-tube visco-meters. The results for an alkali-treated calfskin gelatin of good quality, isoelectric point pH 5.08, are given in the accompanying graph.
We successfully prepared colloidal silver nanoparticles (Ag-NPs) using a nanosecond pulsed Nd:YAG laser, λ = 532 nm, with laser fluence of approximately about 0.6 J/pulse, in an aqueous gelatin solution. The size and optical absorption properties of samples were studied as a function of the laser repetition rates. The results from the UV–vis spectroscopy demonstrated that the mean diameter of Ag-NPs increase with the laser repetition rate increases. The Ag-NPs have mean diameters ranging from approximately 9 nm to 15 nm. Compared with other preparation methods, this work is clean, rapid, and simple to use.Research highlights▶ To date, no approach has been carried out on the preparation of Ag-NPs using gelatin as a stabilizer in the PLA method. ▶ In this paper, we used the PLA method to focus on the preparation of Ag-NPs from silver plating in water using gelatin as a stabilizer. ▶ The effect of the laser-pulsed repetition rate on size of Ag-NPs is studied.
The transformation of rat-tail tendon collagen from the native helical to the random coil form, and the process of reversion of the latter to the former, have been followed viscometrically and polarimetrically in dilute aqueous solutions, both temperature and concentration being varied. The rate of the former process increases ca. 130-fold from 35 to 40°. Final values of the intrinsic viscosity and specific rotation after long periods at temperatures from 35 to 38° show incomplete transformation within this range. The 3° breadth of the transformation equilibrium is attributed to minor variations among the native protofibrillar population. Reversion from coil to helix is first order in the concentration over the range c = 0.066 to 0.41 g./100 ml. The reversion rate displays a large negative temperature coefficient, the half-time increasing ca. 135-fold from 5 to 23°. Inasmuch as the transition temperature Tm for the reverted collagen matches that of the native material and the optical rotation of the former approaches that of the latter, their structures evidently are equivalent. The apparent unimolecularity of the reversion process can be reconciled with the generally accepted three-strand coiled-coil model for the protofibril of the native form by postulating a transitory intermediate consisting of a single chain helix, possibly of the type attributed to synthetic poly-L-proline II, the formation of this intermediate being rate determining. This hypothesis succeeds further in explaining the large negative temperature coefficient of the reversion process. Consideration of the increase in the minimum helix length required for thermodynamic stability at a given degree of supercooling ΔT = Tm -T, where Tm is the equilibrium transformation temperature, leads to an expression of the form Const. exp(- A/kTΔT) for the specific rate where A is a constant. The observed reversion rates are compatible with this relationship.
The effects of a series of salts and acids on the melting points of gelatin gels have been studied. The effects of ions, of the same or opposite charge, are additive. There is a correlation between the binding of ions, as indicated by pH changes, and their effects on the melting point. However, by the use of amino-acetylated gelatin and a guanidino-nitrated, hydroxyl-sulfated gelatin, it is shown that binding of anions at amino, guanidino or hydroxyl groups is not responsible for melting point changes. By the use of carboxyl-esterified gelatin and hydroxyl-acetylated gelatin, it is shown that binding of cations at carboxyl or hydroxyl groups is not the cause of melting point reduction. Iron (III) ion, at low concentration, raises the melting point by inter- or intramolecular cross-linking through the carboxyl groups. In agreement with previous reports polarizable anions are effective melting point reducers with diiodosalicylate being the most potent observed.
The reaction mechanism of chitosan, bovine serum albumin (BSA), and gelatin with genipin (a natural crosslinking reagent) was examined with infrared, ultraviolet–visible, and 13C NMR spectroscopies; protein-transfer reaction mass spectrometry; photon correlation spectroscopy; and dynamic oscillatory rheometry. Two reactions that proceeded at different rates led to the formation of crosslinks between primary amine groups. The fastest reaction to occur was a nucleophilic attack on genipin by a primary amine group that led to the formation of a heterocyclic compound of genipin linked to the glucosamine residue in chitosan and the basic residues in BSA and gelatin. The second, slower, reaction was the nucleophilic substitution of the ester group possessed by genipin to form a secondary amide link with chitosan, BSA, or gelatin. A decreased crosslinking rate in the presence of deuterium oxide rather than water suggested that acid catalysis was necessary for one or both of the reactions to proceed. The behavior of the gel time with polymer concentration was consistent with second-order gelation kinetics resulting from an irreversible crosslinking process, but was complicated by the oxygen radical-induced polymerization of genipin that caused the gels to assume a blue color in the presence of air. The lower elastic modulus attained after a given time during crosslinking of the globular protein BSA as compared to the coiled protein gelatin, despite possessing more crosslinkable basic residues, demonstrated the importance of protein secondary and tertiary structures in determining the availability of sites for crosslinking with genipin in protein systems. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3941–3953, 2003