Fabrication and characterization of chitosan/gelatin porous scaffolds with predefined internal microstructures

The fabrication process for a novel three-dimensional (3D) chitosan/gelatin scaffold with predefined multilevel internal architectures and highly porous structures is presented combining solid freeform fabrication (SFF), microreplication and lyophilization techniques. The computer model of the scaffold is designed with biological data such as branching angle in liver vascular cast incorporated. Stereolithography (SL), known as a SFF technique, is utilized to build the resin mould, based on which poly-dimethylsilicone (PDMS) mould is produced by microreplication. The chitosan/gelatin hybrid solution is then cast onto the PDMS mould for pre-freeze and the monolayer porous structures with organized internal morphology are produced upon lyophilization. The 3D scaffold can be constructed via stacking these monolayer structures. The properties of porous structure, such as porosity, pore size and micromorphology as well as wall thickness, were investigated. Scanning electron microscopy (SEM) demonstrated that the scaffold possesses multilevel organized internal morphologies including vascular systems (portal vein, artery and hepatic vein) and parenchymal component (hepatocyte chamber). These organized structures enable orderly arrangement of hepatocyte and hepatic nonparenchymal cells and co-culture in the same 3D scaffold to guide liver regeneration in a controlled manner. Cell culture experiment in vitro showed that hepatocytes perform better in the well-defined chitosan/gelatin scaffold than in porous scaffold. This approach makes it flexible to investigate the relationship between internal scaffold microstructure and hepatocyte behavior in vitro. It also provides a new way to fabricate complex 3D scaffold using various natural biomaterials for vital organ engineering.     

Novel pH,ion sensitive polyampholyte gels based on carboxymethyl chitosan and gelatin

Natural pH and ion sensitive polyampholyte gels were successfully prepared by blending carboxymethyl chitosan (CM‐chitosan) and gelatin using glutaraldehyde as crosslinking agent. Their swelling behaviour under the influence of pH and ionic strength of the solution has been studied, and molecular interaction and, morphology of the gels were investigated by infrared spectroscopy and scanning electron microscopy. At the isoelectric point (IEP) the blend gels shrunk most, and when pH deviated from the IEP they behaved as polycations or polyanions. A decrease in swelling degree (D_s) with rising NaCl concentration up to 0.15 M was observed for all gels, while addition of Ca²⁺ made them shrink due to formation of Ca²⁺ crosslinked bridges. The blended gels showed increasing sensitivity to pH and ionic strength as the weight fraction of CM‐chitosan increased. Two essential components seem to regulate the swelling behaviour of blended gel: the first is related to osmotic pressure difference caused by the redistribution of mobile ions; the second is related to the possible formation of interactions corresponding to hydrogen bonding and hydrophobic interactions. © 2003 Society of Chemical Industry     

Preparation of gelatin fiber by gel spinning and its mechanical properties

A gel‐spinning process was used in an attempt to prepare a gelatin fiber with a high level of drawability. A gel fiber prepared by extrusion of 15 wt % gelatin in dimethyl sulfoxide into methanol at ?20°C was drawn to sixteen times the original length. After extraction of the dispersion medium, the mechanical strength of the fiber increased markedly with the draw ratio, and the fiber exhibited a tensile strength of 146 MPa and a Young's modulus of 2.3 GPa when drawn to the maximum. A gelatin fiber with greater mechanical strength was obtained when ethylene glycol was used as the spinning solvent. The X‐ray diffraction profile indicated the formation of triple‐helical structures and their lateral association, which is responsible for the mechanical strength of the fiber. Heat‐treatment improved the water‐resistance of the prepared fiber. γ‐Irradiation and treatment with glutaraldehyde improved the mechanical strength of the fiber. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phase separation in poly(vinyl alcohol)/gelatin blend systems

Blends of a commercial poly(vinyl alcohol) (a-PVA) derived from vinyl acetate and gelatin obtained from collagen were prepared by mixing aqueous solutions of both samples under various conditions. For the blend hydrogels, the depression of melting temperatures was observed at high PVA content. Similarly to the a-PVA/silk fibroin (SF) system, when the degrees of polymerization of PVA increased, the microphase separation region in a phase diagram of the blend films increased for the a-PVA/gelatin system. In the IR spectra of the blend films, no absorption bands corresponding to a conformational change of gelatin appeared. Comparison of the mechanical properties of the a-PVA/gelatin and a-PVA/SF systems, showed the interaction between PVA and gelatin molecules to be smaller than that between PVA and SF molecules. © 1999 Society of Chemical Industry     

Phase behavior of gelatin in the presence of pectin in water-acid medium

Summary Phase separation of alkaline gelatin in water-acid solutions in the presence of low etherified pectin (ED 38%) were investigated. The effects of the pectin weight fraction in pectin/gelatin mixture (q_o) as well as two conditions of complex formation, namely, mixing of the binary biopolymer-solvent systems at pH 3.5 (‘mixing conditions’), or preparation of the ternary gelatin-pectin-water systems at pH 7.5 and their subsequent acidification up to pH 3.5 (‘titration conditions’), on phase equilibrium and macrostructure of the concentrated complex phase were established using phase analysis, and optical microscopy. At q_o<0.5 the aggregative phase separation was observed in both conditions of complex formation leading to the almost complete concentration of both biopolymers in the bottom phase at q_o=0.3 (‘mixing conditions’) and at q_o=0.5 (‘titration conditions’). At q_o>0.5 unusual three phase separation took place in the ‘mixing conditions’, leading to formation of supernatant (phase 1), complex coacervate (phase 2) and concentrated pectin solution (phase 3). Possible mechanism of such phenomenon was discussed in term of segregative and aggregative phase separations.     

Characteristics and gel properties of gelatin from goat skin as affected by spray drying

Gelatin powder from goat skin prepared by spray drying at various inlet temperatures (160–200°C) was characterized. Predominant particle sizes were in the range of 4.65–5.14?µm. Gelatin powder was mostly concave in shape with varying sizes, depending on inlet temperatures used. All gelatin powders were creamy whitish. Powder generally became more yellowish as the inlet temperature of spray drying increased (p?p?p?p?>?0.05). Goat skin gelatin spray dried with inlet temperatures of 160 or 180°C had higher gel strength than commercial bovine gelatin (p?相似文献   

Properties of polyelectrolyte complex films of chitosan and gelatin

A series of chitosan–gelatin complexes was prepared by varying the ratio of constituents. Differential scanning calorimetry was used to determine the amount of the different states of water. The interaction between chitosan and gelatin was checked by IR and X-ray analysis and was related to mechanical strength. The results indicate that the water take-up of a chitosan–gelatin complex is depressed by strong interactions within networks. Chitosan can improve the tensile strength of complex films, and even with high water content these can keep appropriate tensile strength and higher elongation. © 1999 Society of Chemical Industry     

Preparation and characterization of gelatin gel with a gradient structure

Gelatin gel with a gradient structure was produced by a vapour crosslinking procedure. The crosslinking degree at various depths (distance from plate surface) and its gradient are dependent on the crosslinking time and vapour temperature. The experimental data indicate that the gelatin gel with a gradient structure does not follow a second‐order swelling kinetics. The dissolution rate can also be regulated by crosslinking time and vapour temperature. © 2000 Society of Chemical Industry     

Fabrication of gelatin/chitosan nanofibrous scaffold: process optimization and empirical modeling

Electrospinning is a very useful technique for producing polymeric nanofibers by applying electrostatic forces. This study reports on the modeling and optimization of the electrospinning process of gelatin/chitosan, using response surface methodology. The individual and the interaction effects of the gelatin/chitosan blend ratio (50/50, 60/40 and 70/30), applied voltage (20, 25 and 30 kV) and feeding rate (0.2, 0.4 and 0.6 mL h^?1) on the mean fiber diameter and standard deviation of the fiber diameter were investigated on optimization section, using scanning electron microscopy. To fabricate the nanofibrous gelatin/chitosan blend, trifluoroacetic acid/dichloromethane was selected as the solvent system. The model obtained for the mean fiber diameter has a quadratic relationship with applied voltage and feeding rate. The interaction between applied voltage and flow rate were found significant but the interactions of blend ratio and flow rate and also blend ratio and applied voltage were negligible. A quadratic relationship was obtained for applied voltage and flow rate with standard deviation of the fiber diameter and there was no interaction between the parameters in the model. The optimum condition for electrospinning of gelatin/chitosan was also introduced using the model obtained in this study. Scanning electron micrographs of human dermal fibroblast cells on the nanofibrous structures show good attachment and proliferation on the fabricated scaffold surface. Electrospun gelatin/chitosan nanofibrous mats have great potential for use as a scaffold for skin tissue engineering. © 2014 Society of Chemical Industry     

Thermal and NMR investigation of the change in the states of water caused by volume phase transition of gelatin gel

The occurrence of volume phase transition (VPT) of a polymer gel is often accompanied by the loss of water. In view of the fact that few studies have been made on the change in different states of water during VPT, in this paper, DSC and NMR are used to check the variation in states of water during VPT of glutaraldehyde crosslinked gelatin gel caused by the variation in composition of water–acetone mixture. The results indicate that the volume of gel collapses at 50 % acetone concentration. The contents of free, intermediate and bound water absorbed by gelatin gel decrease with an increase in the amount of acetone. At 50 % and 60 % acetone content, free water disappears; because acetone accounts for 70 % and 85 %, there remains only bound water. Near VPT the relative content of bound water to total water increases sharply. The spin–lattice relaxation times (T₁) determined by NMR show that the T₁ values of intermediate and bound water, respectively, decrease by approximately four and ten times compared with that of free water. Before VPT, most of the water is freezable and highly mobile. After VPT, bound water gradually plays a dominant role in the mobility of water in the gel. The findings are helpful in understanding the dehydration process of protein induced by poor solvent. © 2000 Society of Chemical Industry     

Use of chitosan derivatives as solid phase extractors for metal ions

This paper shows a comparative study between the two radiation grafted chitosan derivatives viz. cross-linked chitosan (CRC) and cross-linked chitosan after hydrolysis (CRCH). These chitosan derivatives were used as solid phase extractors for several radionuclides. The uptake of ¹³⁷Cs, ^85,89Sr, ¹⁵²Eu, ²⁴¹Am, ²³⁴Th and ²³³U by CRCH and CRC was studied using batch and column methods. The K_d, exchange capacity, breakthrough capacity for different metal ions with the functionalized polymers were determined. The uptake followed the following trend: UO₂²⁺>Th⁴⁺>Cs⁺>Eu³⁺>Am³⁺>Sr²⁺ for both sorbents. It was seen that CRCH has a greater uptake of metal ions compated to CRC but CRC was more selective of the two.     

Weighted‐average isostrain and isostress model to describe the kinetic evolution of the mechanical properties of a composite gel: Application to the system gelatin:Maltodextrin

Application of a weighted‐average model (WAM) to the kinetic evolution of the elasticity during 16 h was successfully performed for a composite gel in which a maltodextrin phase is dispersed within a continuous gelatin phase. The results obtained using the model for different starting compositions along an initial higher‐temperature binodal are in good agreement with the phase diagram measured at high temperature and help to confirm the position of the binodal. A novel application of confocal Raman microscopy was used to measure the local concentration of the included phase of the composite gel and confirms the results given by the WAM. This model allows calculation of tie lines appropriate to the gel state and could be used for other biopolymer blends if the assumption is made that the gelation process involves a complete phase separation of both polymers before any gelation occurs. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1465–1477, 2000     

Synthesis and characterization of biodegradable TPP/genipin co-crosslinked chitosan gel beads

Novel chitosan gel beads were synthesized by a coupled ionic and chemical co-crosslinking mechanism. Tripolyphosphate (TPP) and a naturally occurring crosslinking reagent, genipin, which has been used in herbal medicine, were employed, respectively, as an ionic and a chemical crosslinkers to prepare the chitosan-based networks of gel beads. The competitive crosslinking of chitosan with ionic crosslinker (TPP) and chemical crosslinker (genipin) was characterized by FTIR, UV and EDAX spectroscopy (X-ray energy dispersion) spectroscopy. The variation of characteristic peak of genipin observed from UV spectroscopy and the characteristic peak of tripolyphosphate in crosslinked chitosan-based networks observed from FTIR spectroscopy suggests that the co-crosslinking mechanism is dependent on the pH of TPP/genipin co-crosslinker. The energy profiles of carbon and phosphorus estimated from confirms that chemical crosslinking dominates the co-crosslinking reaction at higher pH condition (pH 7.0 and 9.0) and ionic crosslinking dominates the co-crosslinking reaction at lower pH condition (pH 1.0, 3.0 and 5.0). The pH-dependent ionic/chemical co-crosslinking mechanism shows an obvious effect on the swelling property and enzymatic degradation behavior of prepared chitosan networks. These results reveal that the ionic/chemical co-crosslinked chitosan networks may be suitable for biomedical applications.     

Rheological properties of phase transitions in polydisperse and monodisperse colloidal rod systems

Rheological modifiers are added to formulations to tune rheology, enable function and drive phase changes requiring an understanding of material structure and properties. We characterize two colloidal rod systems during phase transitions using multiple particle tracking microrheology, which measures the Brownian motion of probes embedded in a sample. These systems include a colloid (monodisperse polyamide or polydisperse hydrogenated castor oil), surfactant (linear alkylbenzene sulfonate [LAS]), and nonabsorbing polymer (polyethylene oxide [PEO]) which drives gelation by depletion interactions. Phase transitions are characterized at all concentrations using time-cure superposition. We determine that rheological evolution depends on LAS:colloid. The critical PEO concentration required to form a gel, c_c/c*, is independent of LAS:colloid, critical relaxation exponent, n, is dependent on LAS:colloid, and both are independent of colloid polydispersity. n indicates the material structure at the phase transition. At LAS:colloid > 16, the scaffold is a tightly associated network and at LAS:colloid = 16 a loosely associated network.     

Effect of hydrotalcite on the swelling and mechanical behaviors for the hybrid nanocomposite hydrogels based on gelatin and hydrotalcite

A series of hybrid nanocomposite hydrogels, based on gelatin and intercalated hydrotalcite (IHT), crosslinked with glutaraldehyde, was prepared in this study. The microstructures of the IHT and sample gels were identified by X‐ray diffraction (XRD). Swelling behaviors and physical properties of these hybrid gels were investigated. XRD results indicated that exfoliation of IHT was achieved in the hybrid nanocomposite gels. The results indicated that adding a small amount of IHT could effectively decrease the swelling ratio of the hybrid gels, but adding excess IHT could increase the swelling ratio of the nanocomposite hybrid gels. The crosslinking densities (ρ_x) of the present gels varied with IHT content and swelling ratio of the gels. The drug release behaviors of these gels were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 500–507, 2006     

In situ atomic force microscopy measurement of the dynamic variation in the elastic modulus of swollen chitosan/gelatin hybrid polymer network gels in media of different pH

The surface morphology and elastic modulus of chitosan/gelatin hybrid polymer network (CS/GLN HPN) gels was investigated by in situ atomic force microscopy (AFM). The surface domains of hydrogel varied from irregular clumps to sponge-like patterns with increasing swelling time. The vertical height and width of the surface domains observed in alkali medium are smaller than in acidic medium. The indentation of the gels caused by the AFM tip increased with time and the elastic modulus of the gels estimated by the Hertz model decreased sharply compared with that of xerogel. In alkali medium, due to the reassociation of hydrogen bondings between networks, the elastic modulus increased slightly. © 1999 Society of Chemical Industry     

MTGase反胶束纯化及其催化合成壳聚糖胶原改性物的展望

综述了微生物转谷氨酰胺酶（MTGase）的性质、用途及反胶束萃取纯化效果,展望了用MTGase催化合成等日化用新功能性原料的可行性及其前景。     

Complexation of poly(vinylpyrrolidone) and gelatin with some transition metal chlorides in aqueous solution

Complexation of poly(vinylpyrrolidone) and gelatin with certain metal chlorides (HgCl₂, CdCl₂, CoCl₂, and ZnCl₂) have been investigated by viscosimetric and spectrophotometric techniques in aqueous solutions. While the change in intrinsic viscosity, [η], of poly(vinylpyrrolidone) has shown a discontinuity with a concentration of metal chlorides, gelatin showed a steady decrease with increasing metal chloride concentration. The decreasing order of effectiveness of cations in complex formation is Hg²⁺ > Cd²⁺ > Co²⁺ > Zn²⁺ for poly(vinylpyrrolidone) and Zn²⁺ > Co²⁺ > Cd²⁺ > Hg²⁺ for gelatin solutions. It has been suggested that the poly(vinylpyrrolidone)/metal cation interaction is a charge-controlled reaction, and gelatin/metal cation is a covalent coordination in character. A similar metal cation effect has been observed for poly(vinylpyrrolidone) by UV-VIS spectrophotometry. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 891–895, 1998     

Preparation and characterization of a novel thermosensitive hydrogel based on chitosan and gelatin blends

In this study, a novel injectable in situ gelling thermosensitive hydrogel system based on chitosan and gelatin blends was designed and investigated. The addition of gelatin provides the correct buffering and other physicochemical conditions including control of hydrophobic interactions and hydrogen bonding, which are necessary to retain chitosan in solution at neutral pH near 4°C and furthermore to allow gel formation upon heating to body temperature. The chitosan/gelatin hydrogels were studied by FTIR, swelling, and rheological analysis. The rheological analysis evidenced the endothermic gelation of chitosan/gelatin solutions, which indicated their gelation temperatures and reflected the effect of gelatin concentration on the thermosensitive properties of gels. The morphology of this system was examined with laser scanning confocal microscopy and scanning electron microscopy. The images indicated that the gels were quite heterogeneous and porous. The investigation of these gels as vehicles for delivering bovine serum albumin as a model drug of protein showed that the system could sustain the release of the protein drug. These results show that chitosan/gelatin solutions can form gels rapidly at body temperature and have promising perspective for their use in local and sustained delivery of protein drug. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of the addition of ultrasound‐pulsed gelatin to chitosan on physicochemical and antioxidant properties of casting films

This study investigated the performance of chitosan based films with added, high‐intensity ultrasound‐pulsed, gelatins (42, 52, 71 and 84 W cm^?2). The mechanical, structural, chemical and antioxidant properties were investigated, to evaluate the potential of ultrasound as a technique to improve film properties. The tensile strength and elastic modulus of films containing ultrasound‐pulsed gelatins showed a significant increase, while the elongation parameter showed a significant decrease. Micrographs showed that all films presented agglomerations. The infrared spectra of the films displayed characteristic shifts in the chitosan and gelatin spectra, which may be the result of hydrogen bridge interactions and electrostatic interactions between the two polymers. The antioxidant capacity was analyzed through the ferric reducing antioxidant power (FRAP) assay and the 2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulfonic acid) (ABTS) assay of films and showed that gelatins treated with higher acoustic intensity had improved antioxidant capacity. High‐intensity ultrasound‐treated gelatin enhanced the strength, elasticity and antioxidant properties of the chitosan based films. © 2020 Society of Chemical Industry