Cytotoxicity evaluation of gelatin sponges prepared with different cross-linking agents

Gelatin is a natural polymer used in pharmaceutical and medical applications, especially in the production of biocompatible and biodegradable wound dressings and drug delivery systems. Gelatin granules hydrate, swell and solubilize in water, and rapidly degrade in vivo. The durability of these materials could, however, be prolonged by cross-linking by aldehydes, carbodiimides, and aldose sugars, but the biocompatibility of collagenous biomaterials is profoundly influenced by the nature and extent of cross-linking. In this study, gelatin sponges were prepared by using various cross-linkers such as glutaraldehyde (GA), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDAC), and D-fructose. The effects of the type and the amount of cross-linker on thermal and mechanical properties, stability, and cytotoxicity were investigated. The mechanical analysis data showed that an increase in the amount of GA in the sponge structures caused a slight increase in the modulus of elasticity but had almost no effect on the tensile strength. Increase in the EDAC concentration produced a maximum in the modulus of elasticity and tensile strength values. The stability of the sponges and the time required for complete degradation in aqueous media increased in parallel with the cross-linker content. In vitro studies carried out with fibroblast cells demonstrated a higher cell viability for the samples cross-linked with low concentrations of GA than for those cross-linked with EDAC.     

Studies on immobilization of urease in gelatin by cross-linking.

Urease enzyme was immobilized in photographic gelatin by chemical cross-linking using formaldehyde, glutaraldehyde and chromium (III) acetate. The effects of enzyme and cross-linker concentrations, temperature, incubation time and pH on urea hydrolysis were investigated. Effect of reuse on the activity of immobilized enzyme was also studied. Glutaraldehyde (0.004 M) was the most suitable cross-linker; relative activities within 2.5 months after 24 reuses were stable (about 78%).     

Uses of thermoresponsive and RGD/insulin-modified poly(vinyl ether)-based hydrogels in cell cultures

Thermoresponsive hydrogels were synthesized by radiation copolymerization of ethylene glycol vinyl ether (1) and butyl vinyl ether (2) in the presence of cross-linking agent diethylene glycol divinyl ether. The comonomer ratio (monomer 1/monomer 2) and the cross-linker concentration were kept constant at 60:40 (mole percentage in the monomeric mixture) and 4% (mole basis), respectively. The hydrogels showed a volume-phase transition in the temperature range 10-25 degrees C and their swelling behaviour was reversible. The gels were modified by a cell adhesion factor, the RGD sequence of fibronectin, and a cell growth factor, insulin. However, they lost their thermoresponsive character after modification. The use of the gels in cell culture was investigated without using a proteolytic enzyme or serum. Cell culture studies realized by human skin fibroblasts (HS An1) showed that the cells can attach and proliferate on the surface of a thermoresponsive polymer. 80% of the cultured cells were readily detached from the polymer surface by lowering the incubation temperature from 37 degrees C to 10 degrees C for 30 min. In the studies carried out with RGD or insulin-modified hydrogels in serum-free cultures, higher values of cell proliferation (9 x 10(5) cells/ml) were obtained on the insulin-modified hydrogels, whereas higher values of cell attachment were obtained on the RGD-immobilized surfaces.     

Cytotoxicity evaluation of gelatin sponges prepared with different cross-linking agents

Gelatin is a natural polymer used in pharmaceutical and medical applications, especially in the production of biocompatible and biodegradable wound dressings and drug delivery systems. Gelatin granules hydrate, swell and solubilize in water, and rapidly degrade in vivo. The durability of these materials could, however, be prolonged by cross-linking by aldehydes, carbodiimides, and aldose sugars, but the biocompatibility of collagenous biomaterials is profoundly influenced by the nature and extent of cross-linking. In this study, gelatin sponges were prepared by using various cross-linkers such as glutaraldehyde (GA), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDAC), and D-fructose. The effects of the type and the amount of cross-linker on thermal and mechanical properties, stability, and cytotoxicity were investigated. The mechanical analysis data showed that an increase in the amount of GA in the sponge structures caused a slight increase in the modulus of elasticity but had almost no effect on the tensile strength. Increase in the EDAC concentration produced a maximum in the modulus of elasticity and tensile strength values. The stability of the sponges and the time required for complete degradation in aqueous media increased in parallel with the cross-linker content. In vitro studies carried out with fibroblast cells demonstrated a higher cell viability for the samples cross-linked with low concentrations of GA than for those cross-linked with EDAC.     

Uses of thermoresponsive and RGD/insulin-modified poly(vinyl ether)-based hydrogels in cell cultures

Thermoresponsive hydrogels were synthesized by radiation copolymerization of ethylene glycol vinyl ether (1) and butyl vinyl ether (2) in the presence of cross-linking agent diethylene glycol divinyl ether. The comonomer ratio (monomer 1/monomer 2) and the cross-linker concentration were kept constant at 60 :40 (mole percentage in the monomeric mixture) and 4% (mole basis), respectively. The hydrogels showed a volume-phase transition in the temperature range 10-25 ° C and their swelling behaviour was reversible. The gels were modified by a cell adhesion factor, the RGD sequence of fibronectin, and a cell growth factor, insulin. However, they lost their thermoresponsive character after modification. The use of the gels in cell culture was investigated without using a proteolytic enzyme or serum. Cell culture studies realized by human skin fibroblasts (HS An1) showed that the cells can attach and proliferate on the surface of a thermoresponsive polymer. 80% of the cultured cells were readily detached from the polymer surface by lowering the incubation temperature from 37 ° C to 10 ° C for 30 min. In the studies carried out with RGD or insulin-modified hydrogels in serum-free cultures, higher values of cell proliferation (9 × 10⁵ cells/ml) were obtained on the insulin-modified hydrogels, whereas higher values of cell attachment were obtained on the RGD-immobilized surfaces.     

Characterization of the T cell antigen receptor--p60fyn protein tyrosine kinase association by chemical cross-linking.

Engagement of the TCR by specific antigen results in activation of a tyrosine kinase pathway. A candidate for the kinase responsible for the rapid tyrosine phosphorylation detected with T cell activation is p60fyn, a member of the src kinase family. In an earlier study [Samelson et al. (1990) Proc. Natl Acad. Sci. USA 87:4358] this enzyme was co-immunoprecipitated with the TCR from T cells solubilized in digitonin. In that study a sensitive in vitro kinase assay was used to detect the associated p60fyn. It was subsequently found that the reproducibility of the interaction depended on lot-to-lot variations in digitonin. To eliminate the possibility that the association of antigen receptor and kinase is an artifact of solubilization with ill-defined digitonin preparations, a cross-linking protocol was developed to stabilize the interaction between the TCR and p60fyn. T cells were permeabilized with tetanolysin and proteins were cross-linked with the water soluble chemical cross-linker, 3,3' dithiobis(sulfosuccinimidylpropionate). These experiments allowed the confirmation of the interaction between the TCR, p60fyn, and several additional proteins. The cross-linking studies also enabled the mapping of the interaction of p60fyn and associated proteins to the TCR zeta-chain. This technique should have a general use in stabilizing interactions between other receptors and molecules required for intracellular signaling.     

Cross-linking and characterisation of gelatin matrices for biomedical applications

Cross-linking of gelatin A and B with N,N-(3-dimethylaminopropyl)-N'-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) was optimised by varying the NHS/EDC molar ratio at constant EDC concentration. Native and cross-linked gelatin gels were characterised using the degree of swelling, the number of free amine groups, the phase transition temperature, and titration of the carboxylic acid residues. The cross-linking reaction was most efficient at a NHS to EDC molar ratio of 0.2. At higher NHS/EDC molar ratios, the reaction of EDC with NHS becomes more pronounced, thereby reducing the effective amount of EDC for cross-linking. Swelling measurements of cross-linked gelatin gels gave deviating results when no NHS was used, which was explained by heterogeneous localisation of cross-links in the gelatin gel. The incorporation of undesired compounds into the gelatin gels during the cross-linking reaction was not observed. At optimal NHS to EDC molar ratio, gelatin A and B were cross-linked using increasing EDC/COOHgelatin molar ratios. A range of samples varying from very low cross-link density to very high cross-link density (at high EDC/COOHgelatin) was obtained. Stability of the gels is enhanced with increasing cross-link density, but a minimal cross-link density is required to obtain gelatin gels which are stable at 40 degrees C.     

Covalent and ionic co-cross-linking--an original way to prepare chitosan-gelatin hydrogels for biomedical applications

The first goal of this work was to develop a method for obtaining interpenetrating gelatin (G)-chitosan (CS) networks prepared by double cross-linking (covalent followed by ionic) that exhibit hydrogel character. The second goal was to modulate their properties as a function of the preparation parameters by using neural network models. This study was therefore carried out by experiment and simulation. The covalent cross-linking resulted from the reaction between the carbonyl groups of glutaraldehyde with amino groups belonging to both polymers; the ionic cross-linking is based on the interaction between tripolyphosphate anions and protonated amine groups (ammonium ions) of the polymers. The total cross-linking density (indirectly assessed by estimating the water swelling capacity) and the ability to include hydrosoluble bioactive principles are influenced by the following process parameters: the CS/G ratio, the amount of ionic cross-linker, and the ionic cross-linking time. The prepared hydrogels were characterized with respect to their structural, morphological, and some physical properties. The hydrogels ability to load high amounts of water-soluble drugs indicates their potential use as carriers for biologically active principles in the human body. A neural network methodology was applied to model the swelling degree and caffeine loading/release capacity depending on reaction conditions; in addition, applying this method, the optimal preparation conditions have been determined, targeting pre-established values for swelling degree or maximum caffeine value. The accuracy of the results obtained through this technique proves that the neural networks are suitable tools for modeling cross-linking processes taking place complex nonlinear polymers.     

Bruton's tyrosine kinase is required for signaling the CD79b-mediated pro-B to pre-B cell transition

Formation of the pre-BCR complex is a critical check point during B cell development and induces the transition of pro-B to pre-B cells. CD79b (Igbeta) is a signaling component in the pre-BCR complex, since differentiation to the pre-B phenotype is induced by cross-linking the CD79b expressed on developmentally arrested pro-B cells from recombination-activating gene (RAG)-2-deficient mice. Bruton's tyrosine kinase (BTK) plays important roles in B cell development. However, its molecular mechanisms in early B cell development are not fully understood. To examine whether BTK functions in CD79b-mediated signaling for the pro-B/pre-B transition, we utilized RAG2/BTK double-knockout (DKO) mice. Pro-B cells from RAG2/BTK-DKO mice did not differentiate into pre-B cells following CD79b cross-linking, although tyrosine phosphorylation of cellular proteins including Erk1/2 and phospholipase C-gamma2 was induced in the same manner as RAG2-KO mice. BTK is phosphorylated after cross-linking of CD79b on RAG2-deficient pro-B cells. These findings suggest that BTK-dependent pathways downstream of CD79b are critical for the pro-B/pre-B transition and BTK-independent signaling pathways are also activated via the pre-BCR complex.     

Controlling Thermo-Reversibility of Gelatin Gels through a Peroxidase-Catalyzed Reaction under Mild Conditions for Mammalian Cells

A variety of cross-linking methods is used for obtaining gelatin gels having a tolerance to thermo-reversible gel–sol transition at physiological temperature. In this paper, we investigated the applicability of horseradish peroxidase-catalyzed cross-linking of tyrosine residues originally contained in native gelatin molecules for preparing such gelatin gels. The gelatin gels obtained through exposure to the enzymatic reaction showed a higher resistance to thermo-reversibility at 37°C than gels obtained through a thermally-induced gelation alone. In addition, the resistance property to thermo-reversible gel–sol transition was tunable by controlling enzymatic reaction conditions: higher peroxidase concentration and thermally-induced pre-gelation accomplished by cooling the gelatin solution prior to the enzymatic reaction produced gels with higher resistance to thermo-reversibility. Fibroblast cells enclosed in the gelatin gels obtained through the enzymatic reaction with thermally-induced pre-gelation showed 93% viability. These results demonstrate the feasibility of peroxidase-catalyzed reaction for obtaining gelatin gels having a tolerance to thermo-reversible gel-to-sol transition at physiological temperature toward applications in biomedical and biopharmaceutical fields.     

Role of Thermo-responsiveness and Poly(ethylene glycol) Diacrylate Cross-link Density on Protein Release from Poly(N-isopropylacrylamide) Hydrogels

Thermo-responsive hydrogels have shown promise as injectable materials for local drug delivery. However, the phase-induced changes in polymer properties of N-isopropylacrylamide (NIPAAm) can pose additional challenges for achieving controlled protein release. In this work, thermo-responsive hydrogels derived from NIPAAm and cross-linked with poly(ethylene glycol) diacrylate (PEG-DA) were synthesized via free radical polymerization. The volume phase transition temperature (VPTT) of the hydrogels ranged from 32.9°C to 35.9°C. Below the VPTT, swelling ratios of the hydrogels decreased with cross-linker concentration, and showed a sharp drop (at least 4-fold) upon phase change. Protein encapsulation efficiency was high (84–90%) and decreased with cross-linker concentration. Release of bovine serum albumin, a model protein, at body temperature was significantly higher than at room temperature (67% at 37°C compared to 44% at 23°C after 48 h). The release kinetics of proteins from the hydrogels were initially expected to be a function of cross-link density. However, at the hydrogel compositions explored in this work, protein release did not change significantly with cross-linker mol fraction. The thermo-responsive hydrogels offer a promising platform for the localized delivery of proteins.     

Poly(vinyl alcohol)-heparin hydrogels as sensor catheter membranes

Poly(vinyl alcohol)-heparin hydrogels with varying water content were synthesized for use as sensor catheter membranes. Films were cast from aqueous mixtures of poly(vinyl alcohol) (PVA), a photosensitive cross-linker p-diazonium diphenyl amine polymer (PA), glutaraldehyde (GA) and heparin. After drying, the films were cross-linked by successive UV irradiation and heat treatment. To get an indication about the cross-linking density of the networks, the water content of the hydrogels was measured after equilibration in water. Hydrogels from PVA, PA, GA and heparin, with a water content of 35-95%, could be obtained if the components were dissolved in saline instead of water. The release of heparin from PVA-heparin or PVA-PA-heparin hydrogels was studied using different receiving phases. The cumulative amount of released heparin appeared to be dependent on the initial water content of the hydrogels and the composition of the receiving phase. For the PVA-PA-heparin hydrogels as well as the PVA-heparin hydrogels the cumulative amount of released heparin in water was about six times higher than in a Tris buffer. Using Tris buffer as receiving phase PVA-PA-heparin hydrogels with water contents of 53, 61 or 71% released heparin for at least 3 wk. The cumulative amount of released heparin increased with initial water content of these hydrogels. Recalcification times (RCT) of plasma exposed to PVA-PA-heparin hydrogels (water content 53%), which released heparin at a low rate (2 micrograms/cm2 per day), were markedly prolonged compared with the RCT values for PVA-PA hydrogels without heparin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cross-linking and characterisation of gelatin matrices for biomedical applications

Cross-linking of gelatin A and B with N,N-(3-dimethylaminopropyl)-N′-ethyl-carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) was optimised by varying the NHS/ EDC molar ratio at constant EDC concentration. Native and cross-linked gelatin gels were characterised using the degree of swelling, the number of free amine groups, the phase transition temperature, and titration of the carboxylic acid residues. The cross-linking reaction was most efficient at a NHS to EDC molar ratio of 0.2. At higher NHS/EDC molar ratios, the reaction of EDC with NHS becomes more pronounced, thereby reducing the effective amount of EDC for cross-linking. Swelling measurements of cross-linked gelatin gels gave deviating results when no NHS was used, which was explained by heterogeneous localisation of cross-links in the gelatin gel. The incorporation of undesired compounds into the gelatin gels during the cross-linking reaction was not observed. At optimal NHS to EDC molar ratio, gelatin A and B were cross-linked using increasing EDC/COOH_gelatin molar ratios. A range of samples varying from very low cross-link density to very high cross-link density (at high EDC/COOH_gelatin) was obtained. Stability of the gels is enhanced with increasing cross-link density, but a minimal cross-link density is required to obtain gelatin gels which are stable at 40°C.     

Cytocompatible cross-linking of electrospun zein fibers for the development of water-stable tissue engineering scaffolds

This paper reports a new method of cross-linking electrospun zein fibers using citric acid as a non-toxic cross-linker to enhance the water stability and cytocompatibility of zein fibers for tissue engineering and other medical applications. The electrospun structure has many advantages over other types of structures and protein-based biomaterials possess unique properties preferred for tissue engineering and other medical applications. However, ultrafine fiber matrices developed from proteins have poor mechanical properties and morphological stability in the aqueous environments required for medical applications. Efforts have been made to improve the water stability of electrospun protein scaffolds using cross-linking and other approaches, but the current methods have major limitations, such as cytotoxicity and low efficiency. In this research electrospun zein fibers were cross-linked with citric acid without using any toxic catalysts. The stability of the cross-linked fibers in phosphate-buffered saline and their ability to support the attachment, spreading and proliferation of mouse fibroblast cells were studied. The cross-linked electrospun fibers retained their ultrafine fibrous structure even after immersion in PBS at 37 °C for up to 15 days. Citric acid cross-linked electrospun zein scaffolds showed better attachment, spreading and proliferation of fibroblast cells than uncross-linked electrospun zein fibers, cross-linked zein films and electrospun polylactide fibers.     

Construction of caged polyplexes with a reversible intracellular unpacking property to improve stability and transfection

Cross-linking of protein macromonomers accompanies the assembly of viral particles, which provides the virus with high stability in the host. Following inspiration, caged polyplexes were fabricated via a biomimetic cross-linker. Thiolated polyethylenimine was synthesized and showed sufficient DNA condensation ability. Spherical particles with a diameter of about 150nm were formed at an N/P ratio of 10. Shell-cross-linked polyplexes were then constructed by the oxidation of thiol groups in air. All the results indicate that the cross-linking shell via disulfide bonds could improve the stability of polyplexes in the physiological condition and showed a reversible unpacking property at the intracellular GSH concentration. By selecting the proper preparation conditions, polyplexes caged via a biomimetic cross-linker could efficiently release DNA for transfection.     

Influence of Cross-Linker Concentration on the Functionality of Carbodiimide Cross-Linked Gelatin Membranes for Retinal Sheet Carriers

Carbodiimide cross-linking can easily regulate the functionality of gelatin carriers used for retinal sheet delivery. This paper investigates the effect of cross-linker concentrations (0–0.4 mmol EDC/mg gelatin membrane (GM)) on the properties of the chemically-modified GMs. ATR–FT-IR and ninhydrin analyses results consistently indicated that the EDC cross-linking reaction approaches saturation at concentrations around 0.02 mmol EDC/mg GM. The thermal stability and resistance to water dissolution and collagenase digestion were significantly enhanced with increasing cross-linker concentration from 0.001 to 0.02 mmol EDC/mg GM. In addition, the chemical cross-linking did not affect the ability to form a tissue-encapsulating structure at 37°C. Irrespective of their cross-linking degree, the GMs had an appropriate degradation rate sufficient to allow tissue integration. It was noted that, although high cross-linker concentrations can be used to improve the delivery efficiency of gelatin samples, the treatment with 0.1–0.4 mmol EDC/mg GM may lead to poor biocompatibility. Results of Live/Dead and pro-inflammatory cytokine expression analyses showed that the exposure of ARPE-19 cultures to the test materials cross-linked with a concentration ≥0.1 mmol EDC/mg GM induces significant cytotoxicity and high levels of interleukin-1β and interleukin-6. However, the presence of EDC cross-linked gelatin membranes in the culture medium had no effect on the glutamate uptake capacity. It is concluded that among the cross-linked gelatin samples studied, 0.02 mmol EDC/mg GM is the best cross-linker concentration for preparation of retinal sheet delivery carriers.     

Water-soluble polymers with low critical solution temperature (LCST) as carriers for protein drug delivery

The copolymers of N,N-diethylacrylamide and ovomucoid from duck egg white (an inhibitor of proteolytic enzymes) with low critical solution temperature (LCST) have been synthesized. The behaviour of these copolymers at the point of phase transition was investigated. It was shown that the relation between LCST and physiological activity for these copolymers is a function of their composition. The increase of ovomucoid content leads to the increase of LCST. When the content of ovomucoid rises above 0.2 mol%, LCST disappears. At the same time the physiological activity of obtained copolymers decrease with increasing of N,N-diethylacrylamide content.     

Synthesis,characterization and controlled drug release from temperature-responsive poly(ether-urethane) particles based on PEG-diisocyanates and aliphatic diols

A series of linear amphiphilic poly(ether-urethane)s with alternative hydrophilic/hydrophobic segments based on PEG-diisocyanates and aliphatic diols is developed. The molecular structures of the copolymers were confirmed with nuclear magnetic resonance, Fourier transform infrared spectra and gel permeation chromatography. Nanoparticles prepared by self-assembly of the resulting copolymers show sharp temperature-responsive phase transition. The phase transition temperature could be easily modulated by the length of hydrophilic or hydrophobic segments of the polymer. The mechanism of the temperature-responsive behaviour is discussed. In the presence of these obtained poly(ether-urethane)s, doxorubicin (DOX) could be dispersed into aqueous solution. The ratio of DOX release from polymeric particles increased sharply above the phase transition temperature, while the release was suppressed below the phase transition temperature. A controlled drug release can be achieved by changing the environmental temperature. The easy-prepared polymeric nanoparticles, with features of biocompatibility, biodegradability and tail-made temperature responsiveness, are a kind of promising carriers for temperature-controllable drug release.     

Poly(hydroxyethyl methacrylate-co-methacrylated-beta-cyclodextrin) hydrogels: synthesis, cytocompatibility, mechanical properties and drug loading/release properties

Copolymerization of hydroxyethyl methacrylate (HEMA) with a methacrylated-derivative of β-cyclodextrin (β-CD) was evaluated as a way to obtain hydrogels with tunable mechanical and drug loading and release properties, particularly for preparing medicated soft contact lenses. A fully methacrylated β-CD monomer was synthesized and added to the HEMA and cross-linker solution at concentrations ranging from 0.042 to 0.333 g ml⁻¹ (i.e. 0.23–1.82 mol.%). Thermal polymerization led to transparent hydrogels with a degree of conversion above 74%, which showed a high cytocompatibility and did not induce macrophage response. The greater the content in methacrylated β-CD was, the higher the glass transition temperature, the lower the degree of swelling and free water proportion, and the greater the storage and loss moduli of the swollen disks. These findings are directly related to the increase in the degree of cross-linking caused by the methacrylated β-CD. Loading studies were carried out with hydrocortisone and acetazolamide, both able to form complexes with CDs in water and in lacrimal fluid. Hydrocortisone loading progressively decreased as the content in methacrylated β-CD rose due to a decrease in the volume of aqueous phase of the hydrogel. Acetazolamide loading showed a maximum for an intermediate content in β-CD (0.125–0.167 g ml⁻¹) owing to a balance between complexation with β-CD and hydrogel mesh size. The hydrogels sustained drug delivery for several days, the acetazolamide release rate being dependent on the β-CD content. An adequate selection of the content in β-CD enables pHEMA-co-β-CD hydrogels suitable for specific biomedical applications to be obtained.     

In Vitro Degradation and Drug-Release Properties of Water-Soluble Chitosan Cross-Linked Oxidized Sodium Alginate Core–Shell Microgels

Abstract

Hydrogels based on sodium alginate (SA) have already been widely used in biomedical applications using Ca²⁺ as a cross-linker; however, these hydrogels tend to disintegrate in electrolyte solutions. To solve this problem, we present a kind of oxidized sodium alginate (OSA) microgel using water-soluble chitosan (WSC) as a cross-linker. This microgel was successfully prepared via an emulsion cross-linking technique at room temperature. The microgel was cross-linked by the formation of both Schiff base bonds and inter-polyelectrolyte complexes, which can efficiently eliminate the disintegration of the microgel in electrolyte solutions. Morphological properties of the resulting microgels were determined by transmission electron microscopy (TEM), hydrodynamic diameters of the microgels were characterized by dynamic light scattering (DLS). The objective of this work was to achieve the colon-specific delivery of an anti-ulcerative colitis drug. 5-Aminosalicylic acid (5-ASA) was chosen as a model drug and the in vitro drug-release profile was established in buffer solutions with 0.1 M HCl/NaCl (pH 1.2) and 0.1 M phosphate-buffered saline (PBS, pH 7.4) at 37°C. The microgel was incubated in 0.1 M PBS (pH 7.4) at 37°C to determine its degradation behavior. Cell cytotoxicity (tested by MTT assay) showed that this microgel had no significant cytotoxicity. These results indicated that this microgel prepared by introducing WSC into OSA may have potential applications in oral controlled drug-delivery systems. Therefore, the OSA/WSC microgel may be a useful carrier for the colon-specific delivery of anti-inflammatory drugs including 5-ASA and the enhanced therapeutic effect of ulcerative colitis.