From 3D Hierarchical Scaffolds for Tissue Engineering to Advanced Hydrogel-Based and Complex Devices for in situ Cell or Drug Release

In Vitro Study of Composite Cements on Mesenchymal Stem Cells of Palatal Origin

Uniform filler distribution in composites is an important requirement. Therefore, BaO glass, nano hydroxyapatite and quartz filler distribution was realized through PCL microcapsules which progressively release filler during matrix polymerization. Two composites were realized based on a complex matrix containing BisGMA, UDMA, HEMA and PEG400 mixed with a previously described mineral filler: 33% for C1 and 31% for C2. The spreading efficiency was observed via SEM, revealing a complete disintegration of the microcapsules during C1 polymerization, while C2 preserved some microcapsule parts that were well embedded into the matrix beside BaO filler particles; this was confirmed by means of the EDS spectra. Mesenchymal stem cells of palatal origin were cultured on the composites for 1, 3, 5 and 7 days. The alkaline phosphatase (ALP) level was measured at each time interval and the cytotoxicity was tested after 3, 5 and 7 days of co-culture on the composite samples. The SEM investigation showed that both composites allowed for robust proliferation of the cells. The MSC cell pluripotency stage was observed from 1 to 3 days with an average level of ALP of 209.2 u/L for C1 and 193.0 u/L for C2 as well as a spindle cell morphology. Cell differentiation occurred after 5 and 7 days of culture, implied by morphological changes such as flattened, star and rounded shapes, observed via SEM, which were correlated with an increased ALP level (279.4 u/L for C1 and 284.3 u/L for C2). The EDX spectra after 7 days of co-culture revealed increasing amounts of P and Ca close to the hydroxyapatite stoichiometry, indicating the stimulation of the osteoinductive behavior of MSCs by C1 and C2. The MTT assay test showed a cell viability of 98.08% for C1 and 97.33% for C2 after 3 days, proving the increased biocompatibility of the composite samples. The cell viability slightly decreased at 5 and 7 days but the results were still excellent: 89.5% for C1 and 87.3% for C2. Thus, both C1 and C2 are suitable for further in vivo testing.

Enhancement of Fracture Toughness in carbonate doped Hydroxyapatite based nanocomposites: Rietveld analysis and Mechanical behaviour

Highly nanocrystalline carbonated hydroxyapatite (CHAp) is synthesized by hydrothermal technique with four different stoichiometric compositions for microstructural and mechanical analysis. HAp is one of the most biocompatible material and addition of carbonate ions lead to increase in fracture toughness highly required in biomedical applications. The structural properties and its purity as single phase is confirmed by X-ray diffraction. Lattice imperfections and structural defects is investigated using XRD pattern model simulation, i.e. Rietveld's analysis. The substitution of CO₃^2- in HAp structure leads to a decrease in crystallinity which ultimately lessens crystallite size of sample as verified by XRD analysis. FE-SEM micrographs confirms the formation of nanorods with cuboidal morphology and porous structure of HAp and CHAp samples. The particle size distribution histogram validates the constant decrease in size due to carbonate addition. The mechanical testing of prepared samples revealed the increase in mechanical strength from 6.12 MPa to 11.52 MPa due to the addition of carbonate content, which leads to a rise in fracture toughness, a significant property of an implant material from 2.93 kN to 4.22 kN. The cumulative effect of CO₃^2- substitution on HAp structure and mechanical properties has been generalized for the application as biomedical implant material or biomedical smart materials.

Nitric oxide releasing nanofibrous Fmoc-dipeptide hydrogels for amelioration of renal ischemia/reperfusion injury

Renal ischemia/reperfusion (I/R) injury is responsible for significant mortality and morbidity during renal procedures. Nitric oxide (NO) deficiency is known to play a crucial role in renal I/R injury; however, low stability and severe toxicity of high concentrations of NO have limited its applications. Herein, we developed an in-situ forming Fmoc-dipheylalanine hydrogel releasing s-nitroso-n-acetylpenicillamine (FmocFF-SNAP) for renal I/R injury. Fmoc-FF hydrogel comprising of β-sheet nanofibers was prepared through the pH-titration method. It was then characterized by electron microscopy, pyrene assay, and circular dichroism techniques. Mechanical properties of Fmoc-FF hydrogel (thixotropy and syringeability) were investigated by oscillatory rheology and texture analysis. To assess the therapeutic efficiency in the renal I/R injury model, expression of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) was measured in various samples (different concentrations of free SNAP and FmocFF-SNAP, unloaded Fmoc-FF, and sham control) by real-time RT-PCR, ROS production, serum biomarkers, and histopathological evaluations. According to the results, Fmoc-FF self-assembly in physiologic conditions led to the formation of an entangled nanofibrous and shear-thinning hydrogel. FmocFF-SNAP exhibited a sustained NO release over 7 days in a concentration-dependent manner. Importantly, intralesional injection of FmocFF-SNAP caused superior recovery of renal I/R injury when compared to free SNAP in terms of histopathological scores and renal function indices (e.g. serum creatinine, and blood urea nitrogen). Compared to the I/R control group, biomarkers of oxidative stress and iNOS expression were significantly reduced possibly due to the sustained release of NO. Interestingly, the eNOS expression showed a significant enhancement reflecting the regeneration of the injured endothelial tissue. Thus, the novel FmocFF-SNAP can be recommended for the alleviation of renal I/R injury.

Collagen-Alginate Composite Hydrogel: Application in Tissue Engineering and Biomedical Sciences

Alginate (ALG), a polysaccharide derived from brown seaweed, has been extensively investigated as a biomaterial not only in tissue engineering but also for numerous biomedical sciences owing to its wide availability, good compatibility, weak cytotoxicity, low cost, and ease of gelation. Nevertheless, alginate lacks cell-binding sites, limiting long-term cell survival and viability in 3D culture. Collagen (Col), a major component protein found in the extracellular matrix (ECM), exhibits excellent biocompatibility and weak immunogenicity. Furthermore, collagen contains cell-binding motifs, which facilitate cell attachment, interaction, and spreading, consequently maintaining cell viability and promoting cell proliferation. Recently, there has been a growing body of investigations into collagen-based hydrogel trying to overcome the poor mechanical properties of collagen. In particular, collagen-alginate composite (CAC) hydrogel has attracted much attention due to its excellent biocompatibility, gelling under mild conditions, low cytotoxicity, controllable mechanic properties, wider availability as well as ease of incorporation of other biomaterials and bioactive agents. This review aims to provide an overview of the properties of alginate and collagen. Moreover, the application of CAC hydrogel in tissue engineering and biomedical sciences is also discussed.

Three dimensional printed bioglass/gelatin/alginate composite scaffolds with promoted mechanical strength, biomineralization, cell responses and osteogenesis

In this study, porous bioglass/gelatin/alginate bone tissue engineering scaffolds were fabricated by three-dimensional printing. The compressive strength and in vitro biomineralization properties of the bioglass-gelatin-alginate scaffolds (BG/Gel/SA scaffolds) were significantly improved with the increase of bioglass content until 30% weight percentage followed by a rapid decline in strength. In addition, the cells attach and spread on the BG/Gel/SA scaffolds surfaces represents good adhesion and biocompatibility. Furthermore, the cells (rat bone marrow mesenchymal stem cells, mBMSCs) proliferation and osteogenic differentiation on the BG/Gel/SA scaffolds were also promoted with the increase of bioglass content. Overall, the adding of bioglass in Gel/SA scaffolds promotes mechanical strength and in vitro osteogenic properties and the 30 BG scaffold (30%wt BG) has potential applications in bone tissue engineering and bone regenerative repair because of good compressive strength, biocompatibility, and in vitro osteogenesis.