Gelatin-siloxane Hybrids Research Articles

Gelatin–Siloxane Hybrid Monoliths as Novel Heavy Metal Adsorbents

Novel gelatin-siloxane hybrid monoliths for heavy metal removal were prepared in the chemical reaction of gelatin with organomodified silicone containing epoxy group. Obtained porous hybrid materials were applied for adsorption of Cu(II), Cd(II) and Pb(II) from aqueous solutions. In this paper, the influence of siloxane amount used for the modification of gelatin on adsorbent stability and heavy metal removal was examined. The effect of pH values of the immersion liquid, as well as the contact time, was studied. Morphology, compressive strength and water absorption of hybrid monoliths were investigated. Desorption tests were also performed. The results showed that the higher the amount of the siloxane, the better stability of the hybrid monoliths in aqueous solutions. The highest values of adsorption capacity were observed for Pb(II) ions. The experimental maximum adsorption capacity determined for hybrid monoliths was 3.75 mg/g for Pb(II), 1.76 mg/g for Cu(II) and 1.5 mg/g for Cd(II). The desorption of metal ions for hybrid monoliths stable in aqueous solutions reached 70%.

Comparative analysis and properties evaluation of gelatin microspheres crosslinked with glutaraldehyde and 3-glycidoxypropyltrimethoxysilane as drug delivery systems for the antibiotic vancomycin

In the present comparative study, gelatin microspheres (GMs) were prepared by emulsification-solvent-extraction method using well-known crosslinker: glutaraldehyde (GA) and biocompatible silane-coupling agent: glycidoxypropyltrimethoxysilane (GPTMS). Crosslinking with GA was done by a definite and common procedure, while GPTMS crosslinking potency was investigated after 5, 10, 24, and 48 h synthesis periods and the fabrication method was adjusted in order for preparation of GMs with optimized morphological and compositional characteristics. The prepared GMs were then evaluated and compared as drug delivery systems for the antibiotic vancomycin (Vm). Morphological observations, FTIR, ninhydrin assay, swelling behavior evaluation and Hydrolytic degradation analysis proved successful modification of GMs and revealed that increasing synthesis time from 5 h to 24 h and 48 h, when using GPTMS as crosslinker, led to formation of morphologically-optimized GMs with highest crosslinking degree (∼50%) and the slowest hydrolytic degradation rate. Such GMs also exhibited most sustained release period of Vm. The antibacterial test results against gram-positive bacterium Staphylococcus aureus, were in accordance with the release profiles of Vm, as well. Together, GPTMS-crosslinked GMs with their preferable characteristics and known as biocompatible gelatin-siloxane hybrids, could act as proper drug delivery systems for the sustained release of the antibiotic vancomycin.

Microwave-induced rapid formation of biomimetic hydroxyapatite coating on gelatin-siloxane hybrid microspheres in 10X-SBF solution

AbstractBioactive materials can attract calcium and phosphate ions in simulated body fluid (SBF) solution to mimic the composition of extracellular matrix (ECM). Rapid biodegradation rate of natural polymers in contact with water-based solutions and time-consuming process of mineralization in SBF led to using concentrated simulated media. Herein, gelatin-siloxane microspheres were fabricated via single emulsion method. Then hybrid spheres were immersed in the modified 10X-SBF solution, and microwave energy (600 W) was expanded for the rapid formation of hydroxyapatite (HA) on the spheres. Results indicated homogeneous coating of microspheres and high similarity of synthesized HA to the bone composition. Increasing intensity of HA-related peaks in Fourier transform infrared spectrum, X-ray diffraction and surface roughness after utilizing microwave-assisted method confirmed high efficiency of this technique in biomimetic mineralization of structures. Cell culture studies with human osteosarcoma cell lines (MG-63) demonstrated that mineralized HA in 10X-SBF solution under microwave treatment could be able to mimic bone ECM for tissue regeneration applications in the shortest time and highest similarity to the natural tissue.

Antimicrobial activity of organic–inorganic hybrid films based on gelatin and organomodified silicones

AbstractGelatin–siloxane hybrid films containing antimicrobial agents were prepared in the two‐step procedure. First, gelatin was chemically modified with organomodified silicones containing epoxy (S1) and both epoxy and fluoroalkyl groups (S2). Next, antimicrobial agents such as lysozyme, EDTA, and nisin, in various concentrations, were introduced into obtained hybrid solution, prior to solvent casting of the films. Antimicrobial activity of prepared samples, as well as neat gelatin and gelatin–siloxane hybrid as a reference, was investigated using a modified agar diffusion method against several bacterial strains (Aeromonas hydrophila, Bacillus subtilis, Escherichia coli) and opportunistic fungus (yeast species Candida albicans). Prepared gelatin–siloxane films were characterized using FT‐IR, thermal and SEM analysis. Mechanical properties and swelling behavior of the samples were also investigated. The influence of type and amount of organosilicon compound used for modification of gelatin, as well as type and concentration of applied active agent on antimicrobial activity, was determined. We observed higher antimicrobial activity for all synthesized gelatin–siloxane hybrids than for unmodified gelatin with lysozyme, nisin, and EDTA prepared as comparison. Moreover, samples obtained with siloxane containing fluoroalkyl groups (S2) showed higher resistance to microbial agents than hybrids with S1 siloxane. Hybrid films showed also better water stability than neat biopolymer.

Synthesis, Characterization, and Thermal Properties of Organic–Inorganic Hybrids Based on Gelatin and Organomodified Silicones

ABSTRACTThe synthesis of organic–inorganic hybrids is an interesting approach as it offers the possibility of combining the advantages of organic polymer (elasticity, formability) and inorganic material (hardness, strength, high chemical resistance, and thermal stability). Gelatin–siloxane hybrid materials were prepared in the reaction of gelatin and organomodified silicones containing epoxy‐ and both epoxy‐ as well as fluoroalkyl groups. The hybrids obtained were characterized using Fourier transform infrared spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, and scanning electron microscopic analysis. Thermal properties of the samples were evaluated by means of thermogravimetric analysis and differential scanning calorimetric measurements, showing the influence of type and amount of organosilicon compound on thermal properties of the hybrid materials. The samples obtained with siloxane containing fluoroalkyl groups as well as with mixed siloxanes revealed higher thermal stability than unmodified gelatin. Glass transition temperatures of the hybrids occurred at lower values than for gelatin, exhibiting the plasticizing effect of the applied siloxanes. Enthalpy values of the hybrids decreased, indicating the changes in the helical structure of gelatin caused by the introduction of siloxane.

Facile and green fabrication of biomimetic gelatin–siloxane hybrid hydrogel with highly elastic properties for biomedical applications

Non-covalent hydrogel attracted a great deal of interest in drugs delivery and tissue regeneration areas because of its excellent characters such as mild preparation conditions and easily controlled structure and properties. Herein, we conducted a study on fabricating a biomimetic gelatin–siloxane (GT–S) hybrid hydrogel with tunable composition and properties by a facile and green method. The hybrid hydrogel was formed in biocompatible phosphate buffer solution (PBS) by a simple physical cross-linking mechanism. Hydrogels’ composition, chemical structure, mechanical properties, biodegradation and cellular biocompatibility were investigated in various conditions. The results showed that siloxane contents and curing temperatures had important effects on hybrid hydrogel structure and properties. GT–S hydrogel with optimized siloxane content and curing temperature exhibited high compressive elasticity (3.6 MPa at 86% strain, 85 wt% water) and excellent controlled biodegradation behavior with PBS and enzyme. Furthermore, GT–S hydrogel was shown to support marrow stem cell attachment and proliferation. This study conclusively demonstrates that our hybrid hydrogel has special properties including high elasticity and controlled biodegradation in various conditions. Therefore, it may act as a promising candidate in special biomedical applications such as implants for drugs delivery and scaffolds for tissue regeneration.

Porous gelatin–siloxane hybrid scaffolds with biomimetic structure and properties for bone tissue regeneration

We produced highly porous gelatin-siloxane (GLA-S) hybrid scaffolds with biomimetic anisotropic porous structure, physiochemical properties, mechanical behaviors and biological functions by treating gelatin-siloxane hybrid gels in an ammonium hydroxide solution. The siloxane used as an inorganic phase could effectively crosslink the gelatin polymer, which allowed for the unidirectional enlargement of ammonia vacuoles during ammonium hydroxide treatment. This created aligned pores in an axial direction when the siloxane contents (10 and 20 wt %) were high. In addition, the gelatin polymer could be uniformly hybridized with the siloxane phase at the molecular level, while intense interaction between these two phases could be achieved. This resulted in a significant increase in mechanical properties. The GLA-S hybrid scaffold with a siloxane content of 10 wt % showed reasonably high compressive yield strength of 4.2 ± 0.1 MPa and compressive modulus of 84 ± 5 MPa at a porosity of 86 vol %, which would be comparable to those of natural cancellous bone. In addition, the GLA-S hybrid scaffold had good biocompatibility assessed by in vitro cell tests using pre-osteoblast MC3T3-E1 cells.

Microsphere-integrated gelatin-siloxane hybrid scaffolds for bone tissue engineering: in vitro bioactivity & antibacterial activity

Microsphere integrated gelatin-siloxane hybrid scaffolds were successfully synthesized by using a combined sol-gel processing, post-gelation soaking and freeze-drying process. A bone-like apatite layer was able to form in the Ca2+-containing porous hybrids upon soaking in a simulated body fluid (SBF) up to 1 day. The rate of gentamicin sulfate (GS) release from the GS-loaded gelatin-siloxane hybrid microsphere became constant after a 4 h burst. The antibacterial activity was assessed by the agar diffusion test (ADT) and the bactericidal effect test. It is evident that the as-synthesized porous scaffolds have excellent bioactivity and antibacterial activity, and may be favorable in bone tissue engineering.

Gelatin-Siloxane Hybrid Scaffolds with Vascular Endothelial Growth Factor Induces Brain Tissue Regeneration

In the brain after infarction or trauma, the tissue becomes pannecrotic and forms a cavity. In such situation, a scaffold is necessary to produce new tissue. In this study, we implanted a new porous gelatin-siloxane hybrid derived from gelatin and 3-(glycidoxypropyl) trimethoxysilane (gelatin-GPTMS) scaffolds into a brain defect, and investigated whether it makes a new brain tissue. In addition, vascular endothelial growth factor (VEGF) was added on gelatin-GPTMS scaffolds and its effect on tissue regeneration was examined. At 30 days after the implantation, the marginal territory of the scaffolds became occupied by newly formed tissue. Immunohistochemical analysis revealed that the new tissue was constituted by endothelial, astroglial and microglial cells, some of which were labeled for bromodeoxyuridine (BrdU). Addition of VEGF promoted numbers of these cells. Thus, combination of gelatin-GPTMS scaffolds and VEGF is preferable for brain regeneration.

Bioactive microspheres produced from gelatin–siloxane hybrids for bone regeneration

In this study, we produced a novel microsphere with a hybridized composition of gelatin and siloxane which is bioactive and degradable for the applications in bone regeneration fields. A solution of gelatin organic and siloxane inorganic containing calcium chloride was formulated into microspheres in an oil bath mediated by a surfactant. Following the processes of hydration, gelation and solidification, well-shaped spherical particles were produced with sizes of a few to hundreds of micrometers (68 microm on average). The obtained microspheres were highly stable in an aqueous solution due to the in situ cross-linking of the siloxane with gelatin chains, which eliminated the additional cross-linking step generally used in pure gelatin. The hybridized microspheres exhibited rapid induction of apatite-like crystals on their surface with incubation in a simulated body fluid, suggesting an excellent bone bioactivity in vitro. It is considered that the newly developed organic-inorganic microspheres may be useful for the regeneration of skeletal defects.

Bioactive Gelatin-Siloxane Hybrids as Tissue Engineering Scaffold

Ca2+-containing porous gelatin-siloxane hybrids were prepared using sol-gel process, post-gelation soaking, and freeze-drying. The porosity and pore size of the hybrids could be well controlled by the freezing temperature and the pH value of the soaking solution. The pore characteristics were related to the structure change during the soaking treatment. A bone-like apatite layer was able to form in the Ca2+-containing porous gelatin-siloxane hybrids upon soaking in a stimulated body fluid. The porous gelatin-siloxane hybrids could release gentamicin sulfate which is an antibiotic drug in bone chemotherapy. Thus, those hybrid materials are proposed to find application as novel bioactive and biodegradable scaffolds in bone tissue engineering.

Implantation of a New Porous Gelatin–Siloxane Hybrid into a Brain Lesion as a Potential Scaffold for Tissue Regeneration

For brain tissue regeneration, any scaffold for migrated or transplanted stem cells with supportive angiogenesis is important once necrotic brain tissue has formed a cavity after injury such as cerebral ischemia. In this study, a new porous gelatin-siloxane hybrid derived from the integration of gelatin and 3-(glycidoxypropyl) trimethoxysilane was implanted as a three-dimensional scaffold into a defect of the cerebral cortex. The porous hybrid implanted into the lesion remained at the same site for 60 days, kept integrity of the brain shape, and attached well to the surrounding brain tissues. Marginal cavities of the scaffolds were occupied by newly formed tissue in the brain, where newly produced vascular endothelial, astroglial, and microglial cells were found with bromodeoxyuridine double positivity, and the numbers of those cells were dose-dependently increased with the addition of basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF). Extension of dendrites was also found from the surrounding cerebral cortex to the newly formed tissue, especially with the addition of bFGF and EGF. The present study showed that a new porous gelatin-siloxane hybrid had biocompatibility after implantation into a lesion of the central nervous system, and thus provided a potential scaffold for cell migration, angiogenesis and dendrite elongation with dose-dependent effects of additive bFGF and EGF.

In vitro evaluation of osteoblast response to sol-gel derived gelatin-siloxane hybrids

Cytotoxicity and cytocompatibility of porous gelatin-siloxane hybrids were evaluated due to osteoblastic cell (MC3T3-E1) proliferation, ALP activity, or their responses to the hybrids and their extracts. The hybrids were found intoxic, and appropriate incorporation of calcium ions stimulated proliferation and differentiation in vitro. Cells were seeded into the porous hybrids and the cell morphology was studied. The hybrids involving calcium ions favored osteoblast growth and differentiation.

Novel approach to fabricate porous gelatin–siloxane hybrids for bone tissue engineering

Porous and bioactive gelatin–siloxane hybrids were successfully synthesized by using a combined sol–gel processing, post-gelation soaking, and freeze-drying process to provide a novel kind of materials in the developments and optimization of bone tissue engineering. The pore sizes of the hybrids can be well controlled by varying the freezing temperature. The scaffolds were soaked in a simulated body fluid (SBF) up to 14 days to evaluate the in vitro bioactivity. The Ca 2+-containing scaffolds showed in vitro bioactivity as they biomimetically deposited apatite, but the Ca 2+-free scaffolds failed. Cytotoxicity and cytocompatibility of those scaffolds and their extracts were monitored by the MC3T3-E1 cell responses, including the cell proliferation and the alkaline phosphatase activity. It was demonstrated that appropriate incorporation of Ca 2+ ions stimulated osteoblast proliferation and differentiation in vitro.

Sol–gel preparation and in vitro deposition of apatite on porous gelatin–siloxane hybrids

Ca(II) containing porous hybrids of gelatin and 3-(glycidoxypropyl)trimethoxysilane (GPSM) were prepared using a sol–gel process, post-gelation soaking, and freeze-drying. The porosity and pore size of the hybrids could be well controlled by the freezing temperature and the pH value of the soaking solution. The pore characteristics were related to the structure change during the soaking treatment. A second soaking of the porous hybrids introduced a binary-pore distribution. The rate of biodegradation in a trishydroxymethylaminomethane (Tris) buffer solution decreased with an increased GPSM content. A bone-like apatite layer was able to form in the Ca(II) containing porous gelatin–siloxane hybrids upon soaking in a stimulated body fluid (Kokubo recipe). These hybrid materials are proposed to find application as novel bioactive and biodegradable scaffolds in bone tissue engineering.

Incorporation of Ca2+ Ions in Gelatin-Siloxane Hybrids Through a Sol-Gel Process.

Several gelatin-siloxane hybrids incorporating Ca2+ ions were synthesized through a sol-gel process starting with gelatin, 3-(glycidoxypropyl) trimethoxysilane (GPSM), and Ca(NO3)2. Amino acid analysis, 29Si NMR spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and dynamic mechanical thermal analysis were used to assess the hybrid structure. It has been indicated that the grafting degree of epoxy groups of GPSM to gelatin and the extent of polymerization of methoxysilane end groups of GPSM strongly depended on the fraction of GPSM (fG) in the hybrids, but not on incorporation of Ca2+ ions. Hence, the hybrids with the same fG value, independent of incorporation of Ca2+ ions, had a similar cross-link density. However, the glass transition temperature (Tg) and storage modulus (E′) around Tg decreased with incorporation of Ca2+ ions. Through the deconvolution of amide I bands of FT-IR spectra, flexibility may be interpreted by that the percentage of gelatin having a random structure increased with incorporation of Ca2+ ions. The Ca2+-containing hybrids can spontaneously deposit apatite when they were soaked in a simulated body fluid of the Kokubo recipe, showing their bioactivity.

Synthesis and characterization of gelatin-siloxane hybrids derived through sol-gel procedure

A new type of inorganic-organic hybrid materials incorporating gelatin and 3-(glycidoxypropyl) trimethoxysilane (GPSM) was prepared through sol-gel processing. A solid-state 29Si NMR analysis indicated that all the methoxy silane groups of GPSM were polymerized to yield —Si—O—Si— bridging bonds. An amino acid analysis confirmed grafting reactions of GPSM against gelatin chains. The increasing GPSM/gelatin ratio stimulated gel formation, phase separation, and the density of GPSM-crosslinking of the gelatin chains as well as it changed the micro- and macro- structures and the viscoelastic properties of the final products.