Gelatine/silicate interactions: from nanoparticles to composite gels

Robocasting and Laser Micromachining of Sol-Gel Derived 3D Silica/Gelatin/β-TCP Scaffolds for Bone Tissue Regeneration

The design and synthesis of sol-gel silica-based hybrid materials and composites offer significant benefits to obtain innovative biomaterials with controlled porosity at the nanostructure level for applications in bone tissue engineering. In this work, the combination of robocasting with sol-gel ink of suitable viscosity prepared by mixing tetraethoxysilane (TEOS), gelatin and β-tricalcium phosphate (β-TCP) allowed for the manufacture of 3D scaffolds consisting of a 3D square mesh of interpenetrating rods, with macropore size of 354.0 ± 17.0 μm, without the use of chemical additives at room temperature. The silica/gelatin/β-TCP system underwent irreversible gelation, and the resulting gels were also used to fabricate different 3D structures by means of an alternative scaffolding method, involving high-resolution laser micromachining by laser ablation. By this way, 3D scaffolds made of 2 mm thick rectangular prisms presenting a parallel macropore system drilled through the whole thickness and consisting of laser micromachined holes of 350.8 ± 16.6-micrometer diameter, whose centers were spaced 1312.0 ± 23.0 μm, were created. Both sol-gel based 3D scaffold configurations combined compressive strength in the range of 2–3 MPa and the biocompatibility of the hybrid material. In addition, the observed Si, Ca and P biodegradation provided a suitable microenvironment with significant focal adhesion development, maturation and also enhanced in vitro cell growth. In conclusion, this work successfully confirmed the feasibility of both strategies for the fabrication of new sol-gel-based hybrid scaffolds with osteoconductive properties.

The effect of gelatin as pore expander in green synthesis mesoporous silica for methylene blue adsorption

Mesoporous silica NSG had been synthesized while employing gelatin as a natural template to successfully increase the particle size and expand the pore diameter of NSG. All silica samples exhibited a similar XRD pattern with a broad peak centred at 2θ = 22.9°, as the characteristic of amorphous silica. FTIR results showed that the reduction of Si–O–Si symmetric stretching vibrations at 1075 cm−1 was due to the use of a high percentage of gelatin. Moreover, TEM analysis displayed the mesoporous channels in the form of a honeycomb structure with a diameter of ± 6 nm. Gelatin enhanced the surface area of silica from 467 to 510 m2/g, the pore volume from 0.64 to 0.72 cc/g and expanded the pore diameter from 3.5 nm to 6.0 nm. The expansion of the ordered mesopores with the increase of P123: gelatin ratios was elucidated by the pore size distribution. The adsorption capacity of methylene blue (MB) was improved on mesoporous silica with an expanded pore dimension to give 168 mg/g adsorption capacity within 70 min.

The Effect of Zinc Oxide Supported on Gelatin Mesoporous Silica (GSBA-15) on Structural Character and Their Methylene Blue Photodegradation Performance

Gelatin mesoporous silica SBA-15 (GSBA-15) with rod-like morphology has been successfully synthesized by hydrothermal method using P-123:gelatin, then aged at 90 °C for 24 h and calcined at 550 °C for 5 h. GSBA-15 was impregnated with ZnO amounts of 1; 5; and 10 wt% to obtain Zn/GSBA-15. Samples were characterized by X-ray Diffraction (XRD), Fourier Transform Infra Red (FTIR), Scanning Electron Microscopy (SEM), and Brunauer-Emmett-Teller (BET). The efficiency of methylene blue photodegradation was determined by a UV-Vis spectrophotometer. The FTIR result is functional groups of ZnO/GSBA-15, those were Si−O−Si, −OH, Zn−OH, and Zn−O. The morphology of ZnO/GSBA-15 was rod-like, and it consisted of silica, oxygen, and Zn. The surface area and pore volume of GSBA-15 declined (surface area from 520.8 to 351.9 m2/g and pore volume from 0.707 to 0.564 cm3/g) after ZnO impregnation due to pore blocking. At the same time, increasing pore diameter (from 2.82 nm to 3.19 nm) and crystallite size (from 5.1 nm to 12.6 nm) were observed due to the overlapping of ZnO-Silica particles. The increasing incorporation of ZnO on the silica GSBA-15 framework increases the photodegradation performance from 88.76% to 94.90% due to the high surface area, functional group rich, and dispersion of ZnO active sites. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Silica Hydrogels as Entrapment Material for Microalgae

Despite being a promising feedstock for food, feed, chemicals, and biofuels, microalgal production processes are still uneconomical due to slow growth rates, costly media, problematic downstreaming processes, and rather low cell densities. Immobilization via entrapment constitutes a promising tool to overcome these drawbacks of microalgal production and enables continuous processes with protection against shear forces and contaminations. In contrast to biopolymer gels, inorganic silica hydrogels are highly transparent and chemically, mechanically, thermally, and biologically stable. Since the first report on entrapment of living cells in silica hydrogels in 1989, efforts were made to increase the biocompatibility by omitting organic solvents during hydrolysis, removing toxic by-products, and replacing detrimental mineral acids or bases for pH adjustment. Furthermore, methods were developed to decrease the stiffness in order to enable proliferation of entrapped cells. This review aims to provide an overview of studied entrapment methods in silica hydrogels, specifically for rather sensitive microalgae.

pH-Responsive doxorubicin delivery using shear-thinning biomaterials for localized melanoma treatment

Injectable shear-thinning biomaterials (STBs) have attracted significant attention because of their efficient and localized delivery of cells as well as various molecules ranging from growth factors to drugs. Recently, electrostatic interaction-based STBs, including gelatin/LAPONITE® nanocomposites, have been developed through a simple assembly process and show outstanding shear-thinning properties and injectability. However, the ability of different compositions of gelatin and LAPONITE® to modulate doxorubicin (DOX) delivery at different pH values to enhance the effectiveness of topical skin cancer treatment is still unclear. Here, we fabricated injectable STBs using gelatin and LAPONITE® to investigate the influence of LAPONITE®/gelatin ratio on mechanical characteristics, capacity for DOX release in response to different pH values, and cytotoxicity toward malignant melanoma. The release profile analysis of various compositions of DOX-loaded STBs under different pH conditions revealed that lower amounts of LAPONITE® (6NC25) led to higher pH-responsiveness capable of achieving a localized, controlled, and sustained release of DOX in an acidic tumor microenvironment. Moreover, we showed that 6NC25 had a lower storage modulus and required lower injection forces compared to those with higher LAPONITE® ratios. Furthermore, DOX delivery analysis in vitro and in vivo demonstrated that DOX-loaded 6NC25 could efficiently target subcutaneous malignant tumors via DOX-induced cell death and growth restriction.

Green Synthesis of Hexagonal Hematite (α-Fe2O3) Flakes Using Pluronic F127-Gelatin Template for Adsorption and Photodegradation of Ibuprofen

Hematite (α-Fe2O3) with uniform hexagonal flake morphology has been successfully synthesized using a combination of gelatin as natural template with F127 via hydrothermal method. The resulting hematite was investigated as adsorbent and photocatalyst for removal of ibuprofen as pharmaceutical waste. Hexagonal flake-like hematite was obtained following calcination at 500 °C with the average size was measured at 1-3 µm. Increasing the calcination temperature to 700 °C transformed the uniform hexagonal structure into cubic shape morphology. Hematite also showed high thermal stability with increasing the calcination temperatures; however, the surface area was reduced from 47 m2/g to 9 m2/g. FTIR analysis further confirmed the formation Fe-O-Fe bonds, and the main constituent elements of Fe and O were observed in EDX analysis for all samples. α-Fe2O3 samples have an average adsorption capacity of 55-25.5 mg/g at 12-22% of removal efficiency when used as adsorbent for ibuprofen. The adsorption capacity was reduced as the calcination temperatures increased due to the reduction of available surface area of the hexagonal flakes after transforming into cubes. Photocatalytic degradation of ibuprofen using hematite flakes achieved 50% removal efficiency; meanwhile, combination of adsorption and photocatalytic degradation further removed 80% of ibuprofen in water/hexane mixtures.

Complex Formation of Silica Nanoparticles with Collagen: Effects of the Conformation of Collagen

Negatively charged Ludox silica nanoparticles (SiNPs) form a complex with atelocollagen (AC) in acidic buffers (pH = 4 or 3). AC is a low-immunogenic derivative of collagen obtained by the removal of N- and C-terminal telopeptide components. Mixed solutions of negatively charged SiNPs and AC were turbid, while positively charged SiNPs (Ludox CL) did not form a complex with AC in pH 4 buffer, indicating that electrostatic attraction is the dominant force to form the complex. Small-angle X-ray scattering (SAXS) and circular dichroism (CD) measurements were made for AC and Ludox LS (or CL) solutions in acetate buffer (pH 4.0) and citrate buffer (pH 3.0). The CD data showed that the stability of the triple helical structure of AC in the buffers is not affected by the complexation. The resulting complex consisting of triple helical AC and SiNPs did not influence the SAXS profile except for the lowest q region investigated. On the contrary, different scattering profiles were observed for the single chain AC and SiNP mixture indicating densely packed SiNPs in the complex. This scattering behavior was fairly explained in terms of the sticky hard sphere model (SHSM). This AC conformation-dependent complexation may be because of the hydrogen bonding interaction between the single chain AC and SiNPs. The temperature-induced change of the complex formation can be applied for thermoresponsive hybrid materials.

Stabilization of Collagen Fibrils by Gelatin Addition: A Study of Collagen/Gelatin Dense Phases

Collagen and its denatured form, gelatin, are biopolymers of fundamental interest in numerous fields ranging from living tissues to biomaterials, food, and cosmetics. This study aims at characterizing mixtures of those biopolymers at high concentrations (up to 100 mg·mL^-1) at which collagen has mesogenic properties. We use a structural approach combining polarization-resolved multiphoton microscopy, polarized light microscopy, magnetic resonance imaging, and transmission electron microscopy to analyze gelatin and collagen/gelatin dense phases in their sol and gel states from the macroscopic to the microscopic scale. We first report the formation of a lyotropic crystal phase of gelatin A and show that gelatin must structure itself in particles to become mesogenic. We demonstrate that mixtures of collagen and gelatin phase segregate, preserving the setting of the pure collagen mesophase at a gelatin ratio of up to 20% and generating a biphasic fractal sample at all tested ratios. Moreover, differential scanning calorimetric analysis shows that each protein separates into two populations. Both populations of gelatins are stabilized by the presence of collagen, whereas only one population of collagen molecules is stabilized by the presence of gelatin, most probably those at the interface of the fibrillated microdomains and of the gelatin phase. Although further studies are needed to fully understand the involved mechanism, these new data should have a direct impact on the bioengineering of those two biopolymers.

Design and Cellular Fate of Bioinspired Au-Ag Nanoshells@Hybrid Silica Nanoparticles

Silica-coated gold-silver alloy nanoshells were obtained via a bioinspired approach using gelatin and poly-l-lysine (PLL) as biotemplates for the interfacial condensation of sodium silicate solutions. X-ray photoelectron spectroscopy was used as an efficient tool for the in-depth and complete characterization of the chemical features of nanoparticles during the whole synthetic process. Cytotoxicity assays using HaCaT cells evidenced the detrimental effect of the gelatin nanocoating and significant induction of late apoptosis after silicification. In contrast, PLL-modified nanoparticles had less biological impact that was further improved by the silica layer, and uptake rates of up to 50% of those of the initial particles could be achieved. These results are discussed considering the effect of nanosurface confinement of the biopolymers on their chemical and biological reactivity.

Improved properties of composite collagen hydrogels: protected oligourethanes and silica particles as modulators

This paper reports the structure–property relationship of novel biomedical hydrogels derived from collagen, water-soluble oligourethanes, and silica.

Self-Assembly in Biosilicification and Biotemplated Silica Materials

During evolution, living organisms have learned to design biomolecules exhibiting self-assembly properties to build-up materials with complex organizations. This is particularly evidenced by the delicate siliceous structures of diatoms and sponges. These structures have been considered as inspiration sources for the preparation of nanoscale and nanostructured silica-based materials templated by the self-assembled natural or biomimetic molecules. These templates range from short peptides to large viruses, leading to biohybrid objects with a wide variety of dimensions, shapes and organization. A more recent strategy based on the integration of biological self-assembly as the driving force of silica nanoparticles organization offers new perspectives to elaborate highly-tunable, biofunctional nanocomposites.

Design of Magnetic Gelatine/Silica Nanocomposites by Nanoemulsification: Encapsulation versus in Situ Growth of Iron Oxide Colloids

The design of magnetic nanoparticles by incorporation of iron oxide colloids within gelatine/silica hybrid nanoparticles has been performed for the first time through a nanoemulsion route using the encapsulation of pre-formed magnetite nanocrystals and the in situ precipitation of ferrous/ferric ions. The first method leads to bi-continuous hybrid nanocomposites containing a limited amount of well-dispersed magnetite colloids. In contrast, the second approach allows the formation of gelatine-silica core-shell nanostructures incorporating larger amounts of agglomerated iron oxide colloids. Both magnetic nanocomposites exhibit similar superparamagnetic behaviors. Whereas nanocomposites obtained via an in situ approach show a strong tendency to aggregate in solution, the encapsulation route allows further surface modification of the magnetic nanocomposites, leading to quaternary gold/iron oxide/silica/gelatine nanoparticles. Hence, such a first-time rational combination of nano-emulsion, nanocrystallization and sol-gel chemistry allows the elaboration of multi-component functional nanomaterials. This constitutes a step forward in the design of more complex bio-nanoplatforms.

Incorporation of mesoporous silica particles in gelatine gels: effect of particle type and surface modification on physical properties

The aim of this work was to investigate the impact of mesoporous silica particles (MSPs) on the physicochemical properties of filled protein gels. We have studied the effect of the addition of different mesoporous silica particles, either bare or functionalized with amines or carboxylates, on the physical properties of gelatine gels (5% w/v). Textural properties of the filled gels were investigated by uniaxial compression, while optical properties were investigated by turbidity. The MSPs were characterized with the objective of correlating particle features with their impact on the corresponding filled-gel properties. The addition of MSPs (both with and without functionalization) increased the stiffness of the gelatine gels. Furthermore, functionalized MSPs showed a remarkable increase in the strength of the gels and a slight reduction in the brittleness of the gels, in contrast with nonfunctionalized MSPs which showed no effect on these two properties. The turbidity of the gels was also affected by the addition of all tested MSPs, showing that the particles that formed smaller aggregates resulted in a higher contribution to turbidity. MSPs are promising candidates for the development of functional food containing smart delivery systems, also being able to modulate the functionality of protein gels.

Carboxymethyl cellulose-gelatin-silica nanohybrid: an efficient carrier matrix for alpha amylase

Carboxymethyl cellulose (CMC)-gelatin (G) dual templated polymerization of tetramethoxysilane (TMOS) furnished an efficient hybrid carrier support for alpha amylase. The material has been characterized using FTIR, XRD SEM, TGA and BET studies. The amylase was immobilized at the presynthesized hybrid support by adsorption and the immobilized enzyme was used to optimize the conditions for soluble starch hydrolysis. The immobilization did not change the optimum working pH (pH 5) and temperature (40°C) of the enzymatic reaction. The kinetic parameters of the immobilized (Km=9.970mgmL(-1); Vmax=66.23mgmL(-1)min(-1)) and free amylase (KM=4.0509mgmL(-1), Vmax=4.2909mgmL(-1)min(-1)) indicated that the immobilization has enhanced the catalytic function of diastase alpha amylase. The immobilized enzyme showed higher shelf life as compared to the free enzyme in solution and it could be reused for seven consecutive cycles where 85% of the initial activity was exhibited even in the last cycle. The present material is as efficient as our previously reported material CMC-AgNps-Si.

Design of gold nanoshells via a gelatin-mediated self-assembly of gold nanoparticles on silica cores

Gold nanoshells have been designed for the first time through gold nanoparticles self-assembly on silica/gelatin cores.

Physical properties of fish gelatin-based bio-nanocomposite films incorporated with ZnO nanorods

Well-dispersed fish gelatin-based nanocomposites were prepared by adding ZnO nanorods (NRs) as fillers to aqueous gelatin. The effects of ZnO NR fillers on the mechanical, optical, and electrical properties of fish gelatin bio-nanocomposite films were investigated. Results showed an increase in Young's modulus and tensile strength of 42% and 25% for nanocomposites incorporated with 5% ZnO NRs, respectively, compared with unfilled gelatin-based films. UV transmission decreased to zero with the addition of a small amount of ZnO NRs in the biopolymer matrix. X-ray diffraction showed an increase in the intensity of the crystal facets of (10ī1) and (0002) with the addition of ZnO NRs in the biocomposite matrix. The surface topography of the fish gelatin films indicated an increase in surface roughness with increasing ZnO NR concentrations. The conductivity of the films also significantly increased with the addition of ZnO NRs. These results indicated that bio-nanocomposites based on ZnO NRs had great potentials for applications in packaging technology, food preservation, and UV-shielding systems.

Bionanocomposites: Green sustainable materials for the near future

Bionanocomposites are a novel class of nanosized materials. They contain the constituent of biological origin and particles with at least one dimension in the range of 1–100 nm. There are similarities with nanocomposites but also fundamental differences in the methods of preparation, properties, functionalities, biodegradability, biocompatibility, and applications. The article includes two parts. Bionanocomposite definition and classification along with nanoparticles, biomaterials, and methods of their preparation are initially reviewed. Then, novel approaches developed by our team are presented. The first approach concerns the preparation of bionanocomposites from chitosan and nanoparticles. It is based on the regulated charging of polysaccharide by the gradual shift of solution pH. When charges appear, the biomacromolecules come into the electrostatic interactions with negatively charged nanoparticles that cause the jellification of solutions. It is also applied to form films. They have a nacre-like structure from stacked planar nanoparticles separated by aligned biomacromolecules. The second approach deals with the biomimicking mineralization of biopolymers by using a novel silica precursor. Its advantage over the current sol-gel processing is in the compatibility and regulation of processes and structure of generated silica. Another example of the mineralization is presented by titania. Syntheses are performed in anhydrous ethylene glycol. Processes and structure of bionanocomposites are regulated by water that is added in an amount to only hydrate functional groups in the carbohydrate macromolecule.

Direct scaffolding of biomimetic hydroxyapatite-gelatin nanocomposites using aminosilane cross-linker for bone regeneration

Hydroxyapatite-gelatin modified siloxane (GEMOSIL) nanocomposite was developed by coating, kneading and hardening processes to provide formable scaffolding for alloplastic graft applications. The present study aims to characterize scaffolding formability and mechanical properties of GEMOSIL, and to test the in vitro and in vivo biocompatibility of GEMOSIL. Buffer Solution initiated formable paste followed by the sol-gel reaction led to a final hardened composite. Results showed the adequate coating of aminosilane, 11-19 wt%, affected the cohesiveness of the powders and the final compressive strength (69 MPa) of the composite. TGA and TEM results showed the effective aminosilane coating that preserves hydroxyapatite-gelatin nanocrystals from damage. Both GEMOSIL with and without titania increased the mineralization of preosteoblasts in vitro. Only did titania additives revealed good in vivo bone formation in rat calvarium defects. The scaffolding formability, due to cohesive bonding among GEMOSIL particles, could be further refined to fulfill the complicated scaffold processes.

Investigation of polyurea-crosslinked silica aerogels as a neuronal scaffold: a pilot study

BACKGROUND

Polymer crosslinked aerogels are an attractive class of materials for future implant applications particularly as a biomaterial for the support of nerve growth. The low density and nano-porous structure of this material combined with large surface area, high mechanical strength, and tunable surface properties, make aerogels materials with a high potential in aiding repair of injuries of the peripheral nervous system. however, the interaction of neurons with aerogels remains to be investigated.

METHODOLOGY

In this work the attachment and growth of neurons on clear polyurea crosslinked silica aerogels (PCSA) coated with: poly-L-lysine, basement membrane extract (BME), and laminin1 was investigated by means of optical and scanning electron microscopy. After comparing the attachment and growth capability of neurons on these different coatings, laminin1 and BME were chosen for nerve cell attachment and growth on PCSA surfaces. The behavior of neurons on treated petri dish surfaces was used as the control and behavior of neurons on treated PCSA discs was compared against it.

CONCLUSIONS/SIGNIFICANCE

This study demonstrates that: 1) untreated PCSA surfaces do not support attachment and growth of nerve cells, 2) a thin application of laminin1 layer onto the PCSA discs adhered well to the PCSA surface while also supporting growth and differentiation of neurons as evidenced by the number of processes extended and b3-tubulin expression, 3) three dimensional porous structure of PCSA remains intact after fixing protocols necessary for preservation of biological samples and 4) laminin1 coating proved to be the most effective method for attaching neurons to the desired regions on PCSA discs. This work provides the basis for potential use of PCSA as a biomaterial scaffold for neural regeneration.

Silica hybrid biomaterials containing gelatin synthesized by sol-gel method

This work reports the sol-gel synthesis of silica hybrids. We determined the effect of the type and quantity of silica precursors and organic compounds on the resulting structure, surface area, nanostructure design and size, and potential applications. The structure of the synthesized hybrids was analyzed using FT-IR, XRD, BET-Analysis, SEM, and AFM. We demonstrate the immovilization of whole living thermophilic bacterial cells with cyanocompound degradation activity in the synthesized silica hybrid biomaterials by entrapment, chemical binding, and adsorption.

Enzyme stabilization by glass-derived silicates in glass-exposed aqueous solutions

OBJECTIVES

To analyze the solutes leaching from glass containers into aqueous solutions, and to show that these solutes have enzyme activity stabilizing effects in very dilute solutions.

METHODS

Enzyme assays with acetylcholine esterase were used to analyze serially succussed and diluted (SSD) solutions prepared in glass and plastic containers. Aqueous SSD preparations starting with various solutes, or water alone, were prepared under several conditions, and tested for their solute content and their ability to affect enzyme stability in dilute solution.

RESULTS

We confirm that water acts to dissolve constituents from glass vials, and show that the solutes derived from the glass have effects on enzymes in the resultant solutions. Enzyme assays demonstrated that enzyme stability in purified and deionized water was enhanced in SSD solutions that were prepared in glass containers, but not those prepared in plastic. The increased enzyme stability could be mimicked in a dose-dependent manner by the addition of silicates to the purified, deionized water that enzymes were dissolved in. Elemental analyses of SSD water preparations made in glass vials showed that boron, silicon, and sodium were present at micromolar concentrations.

CONCLUSIONS

These results show that silicates and other solutes are present at micromolar levels in all glass-exposed solutions, whether pharmaceutical or homeopathic in nature. Even though silicates are known to have biological activity at higher concentrations, the silicate concentrations we measured in homeopathic preparations were too low to account for any purported in vivo efficacy, but could potentially influence in vitro biological assays reporting homeopathic effects.

Preparation, characterization and in vitro biological study of biomimetic three-dimensional gelatin-montmorillonite/cellulose scaffold for tissue engineering

This work focused on studying the effect of blending gelatin (Gel) with Cellulose (Cel), in the presence of montmorillonite (MMT), on the swelling behavior, in vitro degradation and surface morphology. Additionally, the effect of the prepared biocomposites on the characteristics of the human osteosarcoma cells (Saos-2), including proliferation, scaffold/cells interactions, apoptosis and their potential of the cells to induce osteogenesis and differentiation was evaluated. The crosslinked biocomposites with glutaraldehyde (GA) or N,N-methylene-bisacrylamide (MBA) was prepared via an intercalation process and freeze-drying technique. Properties including SEM morphology, X-ray diffraction characterization and in vitro biodegradation were investigated. The successful generation of 3-D biomimetic porous scaffolds incorporating Saos-2 cells indicated their potential for de novo bone formation that exploits cell-matrix interactions. In vitro studies revealed that the scaffolds containing 12 and 6% MMT crosslinked by 5 and 0.5% GA seem to be the two most efficient and effective biodegradable scaffolds, which promoted Saos-2 cells proliferation, migration, expansion, adhesion, penetration, spreading, and differentiation, respectively. MMT improved cytocompatibility between the osteoblasts and the biocomposite. In vitro analysis indicated good biocompatibility of the scaffold and presents the scaffold as a new potential candidate as suitable biohybrid material for tissue engineering.