Aqueous Gelatin Solution Research Articles

Monitoring gelation using magnetic nanoparticles

The temperature dependent response of magnetic nanoparticles in oscillating magnetic fields was used to monitor gelation of the surrounding fluid at the size scale of the nanoparticles. The dynamic susceptibility of PEG-coated cobalt ferrite nanoparticles suspended in an aqueous gelatin solution had sharp transitions which correlated with gelation and melting observed using macroscale rheological measurements. The reported method requires small sample volumes and provides information on network formation at the scale of the probe nanoparticles.

Segmental bone regeneration using an rhBMP-2-loaded gelatin/nanohydroxyapatite/fibrin scaffold in a rabbit model

We aimed to develop a hybrid scaffold with a porous structure and similar composition as natural bone for the controlled release of bone morphogenetic protein-2 (BMP-2) to enhance bone regeneration. We fabricated a gelatin/nanohydroxypatite (nHAP) scaffold by glutaraldehyde chemical cross-linking a gelatin aqueous solution with nHAP granules at a 5:1 ratio (v/w). Then, fibrin glue (FG) mixed with recombinant human BMP-2 (rhBMP-2) was infused into the gelatin/nHAP scaffold and lyophilized to develop an rhBMP-2-loaded gelatin/nHAP/FG scaffold. On scanning electron microscopy, the composite had a 3-D porous structure. The rhBMP-2 release kinetics from the hybrid scaffold was sustained and slow, and release of rhBMP-2 was complete at 40 days. Immunohistochemistry, azo-coupling and alizarin S-red staining were used to study in vitro differentiation of human bone-marrow mesenchymal cells (hBMSCs). Strong positive staining results confirmed that rhBMP-2 released from the scaffold could improve osteocalcin (OCN) and alkaline phosphatase (ALP) expression and calcium deposition formation. RT-PCR results showed significantly high mRNA expression of ALP and OCN in hBM-MSCs cultured on the gelatin/nHAP/FG scaffold with rhBMP-2. DNA assay demonstrated that the scaffold was noncytotoxic and could promote hBMSC proliferation from the components of the hybrid scaffold, not released rhBMP-2. The hybrid scaffolds were then used to repair critical-size segmental bone defects of rabbit radius. Gross specimen, X-ray, bone histomorphology and bone mineral density assay demonstrated that the rhBMP-2-loaded gelatin/nHAP/FG scaffold had good osteogenic capability and could repair the segmental bone defect completely in 12 weeks.

Fabrication of nanofiber reinforced protein structures for tissue engineering

Extracellular matrices and degradable nanofibers are two very promising materials in the field of tissue engineering; however both of these structures face limitations as tissue engineering scaffolds. Extracellular matrices, such as collagen, gelatin, and laminin, have excellent biocompatibility and allow cell in growth and survival, but structural weakness makes them difficult to handle and greatly limits their uses. Degradable nanofibers support cell attachment and can provide structural support and directional guidance, but individual degradable nanofibers are fragile and have a tendency to form dense fiber bundles which limit cell penetration into the spaces between the nanofibers, especially in the case of aligned nanofibers. To overcome these difficulties, degradable loose nanofibers were embedded in protein matrix in an attempt to fabricate a hybrid scaffold with improved properties, such as improved strength, guidance, spacing among nanofibers, etc. Polycaprolactone (PCL) was used as a model material for degradable nanofibers. Gelatin was employed as a model protein for matrix structure formation. Thin hybrid films (average thickness = 2.78 um) were fabricated by wetting the loose aligned undirectional nanofiber arrays or loose aligned bi-directional nanofiber grids with a gelatin aqueous solution, which also allows for live cell loading into the nanofiber-protein composite if cell are premixed with protein solution or on the surface of the films. Gelatin film alone without nanofiber reinforcement is difficult to handle due to the weakness of the thin membrane. Gelatin films with a fiber density as low as 3% v/v were structurally robust enough for handling, and manipulation into complex shapes. Mechanical testing confirmed that the addition of nanofibers enhanced the strength of gelatin films, in both dry and hydrated state. In vitro testing confirmed that nanofiber reinforced films were biocompatible and provided cells with directional guidance. Results demonstrate the promise of gelatin/PCL nanofiber composites as a tissue scaffolding material.

Acoustic and viscosity studies of sodium dodecyl sulfate in aqueous solutions of gelatin

Ultrasonic velocities and densities of anionic surfactant, sodium dodecyl sulfate (SDS), in aqueous solutions of gelatin (0.25, 0.50, 1.00%w/v) have been measured over a wide temperature range (20–40 °C) at an interval of 2 °C by using DSA-5000. The data was used to calculate partial molar volume (Ф v ), adiabatic compressibility (β) and apparent molar compressibility (Ф k ) in order to explain protein–surfactant interactions. Viscosity measurements (viscous relaxation time and activation energy parameter) of SDS in aqueous solutions of gelatin were also carried out to support the explanation. A minimum observed in case of activation parameter in the concentration region 6–8 mmol kg − 1 of SDS supported the results obtained by other parameters indicating micellar solubilisation of the SDS in this region. The behaviour of both Ф k and Ф v data indicates that SDS binding to gelatin is non-cooperative at low surfactant concentration but becomes cooperative at higher concentration.

Shock Hugoniot and equations of states of water, castor oil, and aqueous solutions of sodium chloride, sucrose and gelatin

This paper reports a result of experiments for the determination of reliable shock Hugoniot curves of liquids, in particular, at relatively low pressure region, which are needed to perform precise numerical simulations of shock wave/tissue interaction prior to the development of shock wave related therapeutic devices. Underwater shock waves were generated by explosions of laser ignited 10 mg silver azide pellets, which were temporally and spatially well controlled. Measuring temporal variation of shock velocities and over-pressures in caster oil, aqueous solutions of sodium chloride, sucrose and gelatin with various concentrations, we succeeded to determine shock Hugoniot curves of these liquids and hence parameters describing Tait type equations of state.

Temperature Dependence of Sol‐Gel Conversion Kinetics in Gelatin‐Water System

The conversion kinetics of an aqueous gelatin solution to gel was studied by temperature modulated and regular DSC under isothermal and continuous cooling conditions. Isothermal runs revealed a decrease in the quasi-static heat capacity primarily associated with syneresis (phase separation) of the gel. Above 19 degrees C the isothermal process demonstrated negative effective activation energy that turned positive below 14 degrees C. Continuous cooling runs detected a reversing heat flow apparently related to the continuing formation and melting of new gel structures. Isoconversional kinetic analysis of continuous cooling measurements yielded negative activation energy for the whole range of conversions and temperatures suggesting that nucleation remained a rate controlling step throughout the whole gelation process.

Oxidation and magnetic properties of lead nanoparticles in different matrices

Magnetization vs field at different temperatures for Pb nanoparticles. A systematic study was conducted for in situ synthesis of fine Pb nanoparticles in aqueous gelatin solution and in pre-organized gel of polyacrylamide. The Pb nanoparticles stabilized by gelatin or trapped in polyacrylamide matrix transfer electron to O 2 and methyl viologen (paraquat; 1,1′-dimethyl-4,4′-dipyridinium dichloride; MV 2+ (Cl − ) 2 ). Lead nanoparticles were probed for their magnetic characteristics by superconducting quantum interference device (SQUID) magnetometer and display superconductivity with a critical temperature T c of about 7.1 K. The magnetization measurements reveal the superconducting behaviour of Pb nanoparticles prepared in aqueous gelatin stabilized sol and corroborates the results obtained from electron transfer reactions.

Electrospinning of gelatin and gelatin/poly( l-lactide) blend and its characteristics for wound dressing

Gelatin nanofibres were electrospun from its aqueous acetic acid solution. Electrospinning parameters, such as concentration of aqueous acetic acid and gelatin solutions, electric field and spinning distance, were examined to investigate the electrospinnability of gelatin solutions and the morphology of gelatin nanofibrous mats. Nanofibrous mats from poly( l-lactide) (PLLA) and gelatin/PLLA solutions were obtained. The electrospun mats showed controlled evaporative water loss, promoted fluid drainage ability, and excellent biocompatibility, and therefore have a potential application as wound dressing.

Electrowetting of Complex Fluids: Perspectives for Rheometry on Chip

We explore the possibilities of electrowetting (EW) as a tool to assess the elastic properties of aqueous jellifying materials present in the form of a small droplet on a hydrophobic substrate. We monitored the EW response of aqueous solutions of gelatin (2-10 wt %) in ambient oil for various temperatures (8-40 degrees C) below and above the gel point. Whereas the drops remained approximately spherical cap-shaped under all conditions, the voltage-induced reduction of the contact angle became progressively less pronounced upon entering the gel state at lower temperatures. We modeled the decrease in contact angle by minimizing the total energy of the drops consisting of interfacial energies, electrostatic energy, and the elastic energy due to the deformation of the drop, which was taken into account in a modified Hertz model. This allowed fitting the data and extracting the elastic modulus G, which were found to agree well with macroscopic storage moduli G' obtained with oscillatory shear rheometry. These results show that EW can be used as a tool for characterizing soft materials with the elastic moduli ranging (at least) from 10 to 1000 Pa. Our observations also create interesting perspectives for performing in situ rheological measurement inside microfluidic chips.

Phase Diagram of Gelatin Plasticized by Water and Glycerol

AbstractSummary: Gelatin is widely used in capsules manufacturing. Most of the capsules in pharmaceutical applications are hard capsules made out of concentrated solutions of gelatin, where water has been progressively removed during the drying process. More recently soft capsules found an increasing interest in pharmaceutical and cosmetic applications where they are filled and sealed with a liquid substance. In order to keep the shells of capsules flexible after drying at room temperature, plasticizer is added to the gelatin aqueous solutions. We present in this paper a systematic investigation of gelatin films, equilibrated under a range of relative humidity (RH). The films contain glycerol as plasticizer P or only water and gelatin, (G). In order to analyze the role of the plasticizer, we fixed various P/G ratios and measured the water retention versus RH. Films were characterized by DSC (Mettler Toledo DSC823). Glass transition temperature Tg, melting temperature Tm and enthalpy associated with helix‐coil transition were determined. The role of water and glycerol was examined in relation with the large variations of these transition temperatures with film composition. Non equilibrium effects are also discussed, in particular concerning the glass transition temperature, the relaxation effects and the water repartition between amorphous coils and helical structure. In conclusion, we propose a unique phase diagram of the gelatin films with any proportion of water and glycerol.

Plasma sprayed hydroxyapatite coatings from nanostructured granules

The present study utilized nanostructured hydroxyapatite (HA) granules for plasma-sprayed coating on a titanium alloy (Ti–6Al–4V). The initial nanostructured HA powder was synthesized in aqueous solutions of gelatin. The effect of gelatin solutions of variable concentration on the particles size was investigated. The nanostructured HA particles were formed into the porous granules using a liquid immiscibility effect. Consolidation of these powders at various temperatures was carried out. The phase composition, structure, residual stresses and adhesive bond strengths of the obtained coatings from the developed feedstock were investigated by X-ray diffraction, scanning electron microscopy and mechanical tests. X-ray diffraction showed that all the HA coating is a fully crystalline phase without any decomposition. The coatings exhibited a unique phase construction and a fairly low tensile residual stress. The adhesive bond strength of a HA coating was achieved up to 37 ± 2.2 MPa. Tensile failure analysis has suggested that the failure took place at the coating/substrate interface. It is expected that the developed coatings will have much longer service life as compared to the existing ones.

Development of a photocurable gelatin-based gelation material for application to periodontal regeneration

Novel photocurable materials, comprised mixed aqueous solutions of photoreactive gelatin – gelatin partially derivatized with eosin – and polyamine, which is a polymer of N, N-dimethylaminopropylacrylamide, were designed. The materials had appropriate viscosity for shape formation at 37 °C. When photoirradiated with a clinically used visible light source, the materials were almost completely converted to hydrogels to fix their shape in the desired form within several tenths of a second. Cells that were seeded on the eosin–gelatin-coated surface showed good proliferation. Negligible cytotoxicity of eosin–gelatin was confirmed when culturing was performed in the presence of a large amount of eosin–gelatin. The developed photocurable materials could be converted to a hydrogel with desired physical property change by using a convenient curing procedure of photoirradiation at any desired time and in any shape with minimal cytotoxicity, which was appropriate for the application in periodontal tissue regeneration.

Gelatin nanofibrous membrane fabricated by electrospinning of aqueous gelatin solution for guided tissue regeneration

The electrospinning of gelatin aqueous solution was successfully carried out by elevating the spinning temperature. The effects of spinning temperature and solution concentration were investigated on the morphology of gelatin nanofibers in the current study. To improve the stability and mechanical properties in moist state, the gelatin nanofibrous membrane was chemically crosslinked by 1-ethyl-3-dimethyl-aminopropyl carbodiimide hydrochloride and N-hydroxyl succinimide. The concentration of crosslinker was optimized by measuring the swelling degree and weight loss. Nanofibrous structure of the membrane was retained after lyophilization, although the fibers were curled and conglutinated. Tensile test revealed that the hydrated membrane becomes pliable and provides predetermined mechanical properties. Periodontal ligament cells cultured on the membrane in vitro exhibited good cell attachment, growth, and proliferation. Gelatin nanofibrous membrane can be one of promising biomaterials for the regeneration of damaged periodontal tissues.

Immobilization of Ionic Liquid [BMIM][PF6] by Spraying Suspension Dispersion Method

A novel method of immobilizing ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6] by spraying suspension dispersion was proposed. The oil phase, composed of [BMIM][PF6], polysulfone, and dichloromethane, was sprayed into the 0.2 wt % gelatin aqueous solution using nitrogen gas pressure to form droplets. As dichloromethane evaporated completely, polysulfone microcapsules, containing the [BMIM][PF6], were obtained. In order to select a suitable shell material and dispersant, several parallel experiments were also carried out, which proved that that polysulfone and gelatin are suitable shell material and dispersant, respectively. The polysulfone microcapsules enclosing ionic liquid were examined using a scanning electron microscope and thermogravimetric analyzer. The results showed that the microcapsules have an average diameter of 70 mu m with narrow size distribution and smooth surface, and the encapsulation capacity of microcapsules is 29%.

Evolution of ultrasound transmission during the sol‐gel transition

The velocity of the ultrasound wave has been detected during the gelation process of the aqueous gelatin solution. We observe monotonic decrease of the ultrasound transmission in train of the gel network formation. In order to find the dependance of the ultrasound velocity on the number of the intermolecular bonds, responsible for gel formation, we have performed the simultaneous measurements of the optical activity evolution. The experiments have been performed in the gelatin gel and in the silica gel. We have described the process in terms of the percolation theory by power law, according to Landau theory of the second order phase transitions, and by fitting the theoretical results to the experimental curves we have found the appropriate critical exponents. We have also shown how the ultrasound velocity depends on the concentration of the gelling substance and on the temperature, in which the process of the sol‐gel transition has been performed.

Circular dichroism and viscosity studies of gelatin with anionic surfactant, SDBS

The interaction of SDBS in aqueous gelatin solutions is studied above the gelation temperature by viscosity and circular dichroism (CD) measurements. The steep rise in the relative viscosity of the system could be due the structural transitions leading to micellar growth of higher orders, which is supported by CD measurements. The circular dichroism spectra indicated that gelatin helped in inducing the sphere → rod transition, without suffering any conformational changes within it. The large changes in viscosity over the concentration range studied points to the strong molecular interactions in gelatin–SDBS system and its dependence on [SDBS]. CD spectra showed an increase in ellipticity, suggesting that the micelle can either bind intra molecularly, i.e. within a gelatin molecule, or it can bind cooperatively with two or more molecules to form a large complex. The findings are particularly significant in terms of the head group contribution, hydrophobic interaction and formation of formulated complexes.

Interactions of Sodium Dodecyl Benzene Sulfonate and Sodium Dodecyl Sulfate with Gelatin: A Comparison

AbstractThe interaction of SDS/SDBS in aqueous gelatin solutions is studied above the gelation temperature by viscosity and circular dichroism (CD) measurements. The steep rise observed in the relative viscosity can be due the structural transitions leading to micellar growth of higher order. Circular dichroism spectra indicated that gelatin helped in inducing the sphere→rod transition, without suffering any conformational changes within it. The findings are particularly significant in terms of the head group contribution, hydrophobic interaction and the formation of formulated complexes.

Gelatin Hydrogel Electrolytes and Their Application to Electrochemical Supercapacitors

Gelatin hydrogel electrolytes (GHEs) with varying concentrations have been prepared by cross-linking an aqueous solution of gelatin with aqueous glutaraldehyde and characterized by scanning electron microscopy, differential scanning calorimetry, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic chronopotentiometry. Glass transition temperatures for GHEs range between 339.6 and depending on the dopant concentration. Ionic conductivity behavior of GHEs was studied with varying concentrations of gelatin, glutaraldehyde, and , and found to vary between and . GHEs have a potential window of about . Undoped and -doped GHEs follow Arrhenius equations with activation energy values of 1.94 and , respectively. Electrochemical supercapacitors (ESs) employing these GHEs in conjunction with Black Pearl Carbon electrodes are assembled and studied. Optimal values for capacitance, phase angle, and relaxation time constant of , , and are obtained for -doped GHE, respectively. ES with pristine GHE exhibits a cycle life of vs for the ES with -doped GHE.

Temporal evolution of self-organization of gelatin molecules and clusters on quartz surface

Aqueous gelatin solutions when spread on hydrophilic substrates form self-organized structures where the gelatin molecules and clusters are arranged as self-similar objects giving a mass fractal dimension df=1.67 and 1.72 for solutions made with KCl and NaCl salts as estimated from atomic force microscopic studies. The dehydration driven self-organization of particles changed the df values to 1.78 and 1.81, respectively, after 24 h. This further changed to 1.83 and 1.85 after a time lapse of 10 days. The dynamics of formation of these structures are modeled through spin-exchange kinetics in the nonequilibrium steady state regime in order to understand their complex behavior. Kawasaki spin exchange dynamics has been applied to a diffusion limited aggregation type fractal object, and the growth of the domains was observed by minimizing the free energy. The fractal dimension of such a system changed from 1.70 to 1.82 which inferred the loss of fractal behavior and the generation of a more compact object. The experimentally observed temporal evolution of these complex structures could be adequately described through the results obtained from the computer simulation data.

Experimental Determination of Shock Hugoniot for Water, Castor Oil, and Aqueous Solutions of Sodium Chloride, Sucrose and Gelatin

Shock waves are indispensable tools for medical applications, and hence their interactions with human tissue become one of the most important basic research topics. In this paper, the determination of shock Hugoniot curves for liquids that can model human tissue, namely water, castor oil, and aqueous solutions of sodium chloride, sucrose and gelatin, at 10 and 20 weight percent are presented. Underwater shock waves were generated by ignition of 10 mg silver azide pellets and time variations of over-pressures were measured and simultaneously the shock speed was measured by the time of flight technique. Then shock Hugoniot curves were obtained, by assuming the Tait type equation of state, to relate the estimated density and measured pressure values. Results show in the cases of aqueous solutions that increasing amount of additives into water causes only a very minute decrease in the compressibility of the solution. This difference was more pronounced in the case of sodium chloride, less for gelatin, and almost none for sucrose aqueous solution.