Preparation and Heavy Metal Ions Chelating Properties of Multifunctional Polymer-Grafted Silica Hybrid Materials

In this research work, novel hybrid materials based on multifunctional polymers and silica were developed and investigated in view of possible employment as sorbents for removal of heavy metal ions from water in presence of various ions. Organic-inorganic hybrid materials were prepared by covalent bonding of vinyl-terminated polyamidoamine (PAA) onto aminated silica particles. Two series of polyamidoamine-grafted silica, differing in the PAA chemical structure, were synthesized, and their heavy metal ions chelating properties were investigated. Column adsorption procedure for Cu, Zn, and Ni in aqueous solution was successfully established. Moreover, the adsorption behaviour of the materials was evaluated in different ionic strength solutions as well as in distilled and natural water. Organic-inorganic hybrid materials exhibited excellent chelating properties and selectivity for different metal ions. The hybrid columns showed exceptional eluting and regenerating property using diluted hydrochloric acid solution as eluent. In particular, the hybrid materials containing more carboxy groups possessed superior adsorption ability, reusability, and stability. The consecutive adsorption-desorption experiments exhibited that this material could be reused more than 20 cycles without almost any loss of adsorption capability. These new organic-inorganic sorbents appear very promising as an effective solid-phase extraction material for the selective preconcentration or removing of heavy metal ions from the environment

Designing Viscoelastic Gelatin-PEG Macroporous Hybrid Hydrogel with Anisotropic Morphology and Mechanical Properties for Tissue Engineering Application

The mechanical properties of scaffolds play a vital role in regulating key cellular processes in tissue development and regeneration in the field of tissue engineering. Recently, scaffolding material design strategies leverage viscoelasticity to guide stem cells toward specific tissue regeneration. Herein, we designed and developed a viscoelastic Gel-PEG hybrid hydrogel with anisotropic morphology and mechanical properties using a gelatin and functionalized PEG (as a crosslinker) under a benign condition for tissue engineering application. The chemical crosslinking/grafting reaction was mainly involved between epoxide groups of PEG and available functional groups of gelatin. FTIR spectra revealed the hybrid nature of Gel-PEG hydrogel. The hybrid hydrogel showed good swelling behavior (water content > 600%), high porosity and pore interconnectivity suitable for tissue engineering application. Simple unidirectional freezing followed by a freeze-drying technique allowed the creation of structurally stable 3D anisotropic macroporous architecture that showed tissue-like elasticity and was capable of withstanding high deformation (50% strain) without being damaged. The tensile and compressive modulus of Gel-PEG hybrid hydrogel were found to be 0.863 MPa and 0.330 MPa, respectively, which are within the range of normal human articular cartilage. In-depth mechanical characterizations showed that the Gel-PEG hybrid hydrogel possessed natural-tissue-like mechanics such as non-linear and J-shaped stress-strain curves, stress softening effect, high fatigue resistance and stress relaxation response. A month-long hydrolytic degradation test revealed that the hydrogel gradually degraded in a homogeneous manner over time but maintained its structural stability and anisotropic mechanics. Overall, all these interesting features provide a potential opportunity for Gel-PEG hybrid hydrogel as a scaffold in a wide range of tissue engineering applications

Dynamic Freedom: Substrate Stress Relaxation Stimulates Cell Responses

An elastic substrate stores cell-induced forces, while a viscoelastic substrate dissipates these forces through matrix reorganization and facilitates cell proliferation and differentiation

Comparative studies of mechanical and interfacial properties between jute and bamboo fiber-reinforced polypropylene-based composites

Jute and bamboo fiber-reinforced polypropylene (PP) based composites (50wt% fiber) were fabricated by compression molding. Tensile strength (TS), bending strength (BS), tensile modulus (TM), and bending modulus (BM) of the jutereinforced PP composite were found to be 48, 56, 900, and 1500 MPa, respectively. Then, bamboo fiber-reinforced PP-based composites (50 wt% fiber) were fabricated and the mechanical properties evaluated. The TS, BS, TM, and BM of bambooreinforced PP composites were found to be 60, 76, 4210, and 6210 MPa, respectively. It was revealed that bamboo fiber-based composites had higher TS, BS, TM, and BM compared to jute-based composites. Degradation tests of the composites (jute fiber/PP and bamboo fiber/PP) were performed in soil at ambient conditions for up to 24 weeks. It was revealed that bamboo fiber/PP composite retained its original mechanical properties higher than that of jute fiber/PP composite. The interfacial shear strength of the jute and bamboo fiber-based composites was investigated using the single-fiber fragmentation test and it was found to be 2.14 and 4.91 MPa, respectively. Fracture sides of the composites were studied by scanning electron microscope, and the results revealed poor fiber matrix adhesion for jute fiber-based composites compared to that of the bamboo fiber-based composites

Polysaccharides on gelatin-based hydrogels differently affect chondrogenic differentiation of human mesenchymal stromal cells

Selection of feasible hybrid-hydrogels for best chondrogenic differentiation of human mesenchymal stromal cells (hMSCs) represents an important challenge in cartilage regeneration. In this study, three-dimensional hybrid hydrogels obtained by chemical crosslinking of poly (ethylene glycol) diglycidyl ether (PEGDGE), gelatin (G) without or with chitosan (Ch) or dextran (Dx) polysaccharides were developed. The hydrogels, namely G-PEG, G-PEG-Ch and G-PEG-Dx, were prepared with an innovative, versatile and cell-friendly technique that involves two preparation steps specifically chosen to increase the degree of crosslinking and the physical-mechanical stability of the product: a first homogeneous phase reaction followed by directional freezing, freeze-drying and post-curing. Chondrogenic differentiation of human bone marrow mesenchymal stromal cells (hBM-MSC) was tested on these hydrogels to ascertain whether the presence of different polysaccharides could favor the formation of the native cartilage structure. We demonstrated that the hydrogels exhibited an open pore porous morphology with high interconnectivity and the incorporation of Ch and Dx into the G-PEG common backbone determined a slightly reduced stiffness compared to that of G-PEG hydrogels. We demonstrated that G-PEG-Dx showed a significant increase of its anisotropic characteristic and G-PEG-Ch exhibited higher and faster stress relaxation behavior than the other hydrogels. These characteristics were associated to absence of chondrogenic differentiation on G-PEG-Dx scaffold and good chondrogenic differentiation on G-PEG and G-PEG-Ch. Furthermore, G-PEG-Ch induced the minor collagen proteins and the formation of collagen fibrils with a diameter like native cartilage. This study demonstrated that both anisotropic and stress relaxation characteristics of the hybrid hydrogels were important features directly influencing the chondrogenic differentiation potentiality of hBM-MSC

3D gelatin-chitosan hybrid hydrogels combined with human platelet lysate highly support human mesenchymal stem cell proliferation and osteogenic differentiation

Bone marrow and adipose tissue human mesenchymal stem cells were seeded in highly performing 3D gelatin–chitosan hybrid hydrogels of varying chitosan content in the presence of human platelet lysate and evaluated for their proliferation and osteogenic differentiation. Both bone marrow and adipose tissue human mesenchymal stem cells in gelatin–chitosan hybrid hydrogel 1 (chitosan content 8.1%) or gelatin–chitosan hybrid hydrogel 2 (chitosan 14.9%) showed high levels of viability (80%–90%), and their proliferation and osteogenic differentiation was significantly higher with human platelet lysate compared to fetal bovine serum, particularly in gelatin–chitosan hybrid hydrogel 1. Mineralization was detected early, after 21 days of culture, when human platelet lysate was used in the presence of osteogenic stimuli. Proteomic characterization of human platelet lysate highlighted 59 proteins mainly involved in functions related to cell adhesion, cellular repairing mechanisms, and regulation of cell differentiation. In conclusion, the combination of our gelatin–chitosan hybrid hydrogels with hPL represents a promising strategy for bone regenerative medicine using human mesenchymal stem cells

Effects of gamma sterilization on the physicomechanical and thermal properties of gelatin‐based novel hydrogels

Hydrogels are attracting ample attention for tissue engineering application thanks to their water-loving attribute and closely mimicry to the natural extracellular matrix. However, effectively and efficiently sterilization of hydrogels without compromising their end-use beneficial attributes is a major challenge. The aim of this work is to study the resistance to gamma sterilization of newly developed gelatin-based hybrid hydrogels for tissue engineering. This study reported the investigation of 25 kGy gamma sterilization, a typical sterilization procedure for healthcare products, on the physico-mechanical and thermal properties of a three set of gelatin-based novel hydrogels, namely, gelatin-polyethylene glycol (G/PEG), gelatin-polyethylene glycol-hydroxyethyl cellulose (G/PEG/HEC) and gelatin-polyethylene glycol-chitosan (G/PEG/CH). FTIR and TGA were done to evaluate the chemical change and variation of thermal behavior, respectively, imposed by the gamma exposure, and the results showed that gamma sterilization did not modify the chemical composition and thermal degradation behavior of the hydrogels. The water uptake, mechanical properties (both in tension and compression) and stress relaxation experiments revealed that parent G/PEG and interpenetrating polymer network (IPN) G/PEG/CH were nearly negligibly sensitive to the gamma sterilization. However, semi-interpenetrating polymer network (semi-IPN) G/PEG/HEC appeared to be slightly vulnerable to the gamma exposure: a decrease in modulus and strength but simultaneous increase in water uptake, percentage dissipation energy and stress relaxation responses were observed

Effects of Gamma Sterilization on the Physico-Mechanical and Thermal Properties of Gelatin-Based Novel Hydrogels

Hydrogels are attracting ample attention for tissue engineering application thanks to their water-loving attribute and closely mimicry to the natural extracellular matrix. However, effectively and efficiently sterilization of hydrogels without compromising their end-use beneficial attributes is a major challenge. The aim of this work is to study the resistance to gamma sterilization of newly developed gelatin-based hybrid hydrogels for tissue engineering. This study reported the investigation of 25 kGy gamma sterilization, a typical sterilization procedure for healthcare products, on the physico-mechanical and thermal properties of a three set of gelatin-based novel hydrogels, namely, gelatin-polyethylene glycol (G/PEG), gelatin-polyethylene glycol-hydroxyethyl cellulose (G/PEG/HEC) and gelatin-polyethylene glycol-chitosan (G/PEG/CH). FTIR and TGA were done to evaluate the chemical change and variation of thermal behavior, respectively, imposed by the gamma exposure, and the results showed that gamma sterilization did not modify the chemical composition and thermal degradation behavior of the hydrogels. The water uptake, mechanical properties (both in tension and compression) and stress relaxation experiments revealed that parent G/PEG and interpenetrating polymer network (IPN) G/PEG/CH were nearly negligibly sensitive to the gamma sterilization. However, semi-interpenetrating polymer network (semi-IPN) G/PEG/HEC appeared to be slightly vulnerable to the gamma exposure: a decrease in modulus and strength but simultaneous increase in water uptake, percentage dissipation energy and stress relaxation responses were observed

Degradation-Dependent Stress Relaxing Semi-Interpenetrating Networks of Hydroxyethyl Cellulose in Gelatin-PEG Hydrogel with Good Mechanical Stability and Reversibility

The mechanical milieu of the extracellular matrix (ECM) plays a key role in modulating the cellular responses. The native ECM exhibits viscoelasticity with stress relaxation behavior. Here, we reported the preparation of degradation-mediated stress relaxing semi-interpenetrating (semi-IPN) polymeric networks of hydroxyethyl cellulose in the crosslinked gelatin-polyethylene glycol (PEG) architecture, leveraging a newly developed synthesis protocol which successively includes one-pot gelation under physiological conditions, freeze-drying and a post-curing process. Fourier transform infrared (FTIR) confirmed the formation of the semi-IPN blend mixture. A surface morphology analysis revealed an open pore porous structure with a compact skin on the surface. The hydrogel showed a high water-absorption ability (720.00 ± 32.0%) indicating the ability of retaining a hydrophilic nature even after covalent crosslinking with functionalized PEG. Detailed mechanical properties such as tensile, compressive, cyclic compression and stress relaxation tests were conducted at different intervals over 28 days of hydrolytic degradation. Overall, the collective mechanical properties of the hydrogel resembled the mechanics of cartilage tissue. The rate of stress relaxation gradually increased with an increasing swelling ratio. Hydrolytic degradation led to a marked increase in the percentage dissipation energy and stress relaxation response, indicating the degradation-dependent viscoelasticity of the hydrogel. Strikingly, the hydrogel maintained the structural stability even after degrading two-thirds of its initial mass after a month-long hydrolytic degradation. This study demonstrates that this semi-IPN G-PEG-HEC hydrogel possesses bright prospects as a potential scaffolding material in tissue engineering