Slim en efficiënt zoeken met AGNES. Graven in archeologische onderzoeksrapporten

Digital Archaeolog

Hybrid manufacturing strategies for tissue engineering scaffolds using methacrylate functionalised poly(glycerol sebacate)

Poly(glycerol sebacate) is an attractive biomaterial for tissue engineering due to its biocompatibility, elasticity and rapid degradation rate. However, poly(glycerol sebacate) requires harsh processing conditions, involving high temperatures and vacuum for extended periods, to produce an insoluble polymer matrix. These conditions make generating accurate and intricate geometries from poly(glycerol sebacate), such as those required for tissue engineering scaffolds, difficult. Functionalising poly(glycerol sebacate) with methacrylate groups produces a photocurable polymer, poly(glycerol sebacate)-methacrylate, which can be rapidly crosslinked into an insoluble matrix. Capitalising on these improved processing capabilities, here, we present a variety of approaches for fabricating porous tissue engineering scaffolds from poly(glycerol sebacate)-methacrylate using sucrose porogen leaching combined with other manufacturing methods. Mould-based techniques were used to produce porous disk-shaped and tubular scaffolds. Porogen size was shown to influence scaffold porosity and mechanical performance, and the porous poly(glycerol sebacate)-methacrylate scaffolds supported the proliferation of primary fibroblasts in vitro. Additionally, scaffolds with spatially variable mechanical properties were generated by combining variants of poly(glycerol sebacate)-methacrylate with different stiffness. Finally, subtractive and additive manufacturing methods were developed with the capabilities to generate porous poly(glycerol sebacate)-methacrylate scaffolds from digital designs. These hybrid manufacturing strategies offer the ability to produce accurate macroscale poly(glycerol sebacate)-methacrylate scaffolds with tailored microscale porosity and spatially resolved mechanical properties suitable for a broad range of applications across tissue engineering

Fabrication of biodegradable synthetic vascular networks and their use as a model of angiogenesis

One of the greatest challenges currently faced in tissue engineering is the incorporation of vascular networks within tissue-engineered constructs. The aim of this study was to develop a technique for producing a perfusable, three-dimensional cell friendly model of vascular structures that could be used to study the factors affecting angiogenesis and vascular biology in engineered systems in more detail. Initially, biodegradable synthetic pseudo-vascular networks were produced via the combination of robocasting and electrospinning techniques. The internal surfaces of the vascular channels were then recellularized with human dermal microvascular endothelial cells (HDMECs) with and without the presence of human dermal fibroblasts (HDFs) on the outer surface of the scaffold. After 7 days in culture, channels that had been reseeded with HDMECs alone, demonstrated irregular cell coverage. However when using a co-culture of HDMECs inside and HDFs outside the vascular channels, coverage was found to be continuous throughout the internal channel. Using this cell combination, collagen gels loaded with vascular endothelial growth factor were deposited onto the outer surface of the scaffold and cultured for a further 7 days after which endothelial cell (EC) outgrowth from within the channels into the collagen gel was observed showing the engineered vasculature maintains its capacity for angiogenesis. Furthermore the HDMECs appeared to have formed perfusable tubules within the gel. These results show promising steps towards the development of an in vitro platform upon which to study angiogenesis and vascular biology in a tissue-engineering context

Bioengineering vascular networks to study angiogenesis and vascularisation of physiologically relevant tissue models in vitro

Angiogenesis assays are essential for studying aspects of neovascularisation and angiogenesis and investigating drugs that stimulate or inhibit angiogenesis. To date, there are several in vitro and in vivo angiogenesis assays that are used for studying different aspects of angiogenesis. Although in vivo assays are the most representative of native angiogenesis, they raise ethical questions, require considerable technical skills, and are expensive. In vitro assays are inexpensive and easier to perform, but the majority of them are only two-dimensional cell monolayers which lack the physiological relevance of three-dimensional structures. Thus, it is important to look for alternative platforms to study angiogenesis under more physiologically relevant conditions in vitro. Accordingly, in this study, we developed polymeric vascular networks to be used to study angiogenesis and vascularisation of a 3D human skin model in vitro. Our results showed that this platform allowed the study of more than one aspect of angiogenesis, endothelial migration and tube formation, in vitro when combined with Matrigel®. We successfully reconstructed a human skin model, as a representative of a physiologically relevant and complex structure, and assessed the suitability of the developed in vitro platform for studying endothelialisation of the tissue-engineered skin model

Enhanced collagen production from human dermal fibroblasts on poly(glycerol sebacate)-methacrylate scaffolds

Poly(glycerol sebacate)-methacrylate (PGS-M) is a photocurable form of polyglycerol sebacate (PGS) that has recently been shown to be suitable for use as a scaffold for tissue engineering. It has the benefits of PGS, including biocompatibility and biodegradability, while also being much simpler to process into a variety of 3D structures. Cell compatibility has already been demonstrated on the 30% methacrylated PGS-M scaffolds. However no studies have yet assessed the collagen produced by cells growing on the PGS-M scaffold. Here we demonstrate that 50% methacrylated PGS-M 3D scaffolds are able to support the culture of human dermal fibroblasts for 1 week. We also show that collagen production is enhanced compared with the same cells growing on tissue culture plastic, with the cells producing approximately 50% more total collagen after 1 week in culture. These results go further to demonstrate the suitability of the PGS-M scaffolds for generating ECM based constructs for soft tissue engineering

Characterizing cross‐linking within polymeric biomaterials in the SEM by secondary electron hyperspectral imaging

A novel capability built upon secondary electron (SE) spectroscopy provides an enhanced cross‐linking characterization toolset for polymeric biomaterials, with cross‐linking density and variation captured at a multiscale level. The potential of SE spectroscopy for material characterization has been investigated since 1947. The absence of suitable instrumentation and signal processing proved insurmountable barriers to applying SE spectroscopy to biomaterials, and consequently, capturing SE spectra containing cross‐linking information is a new concept. To date, cross‐linking extent is inferred from analytical techniques such as nuclear magnetic resonance (NMR), differential scanning calorimetry, and Raman spectroscopy (RS). NMR provides extremely localized information on the atomic scale and molecular scale, while RS information volume is on the microscale. Other methods for the indirect study of cross‐linking are bulk mechanical averaging methods, such as tensile and compression modulus testing. However, these established averaging methods for the estimation of polymer cross‐linking density are incomplete because they fail to provide information of spatial distributions within the biomaterial morphology across all relevant length scales. The efficacy of the SE spectroscopy capability is demonstrated in this paper by the analysis of poly(glycerol sebacate)‐methacrylate (PGS‐M) at different degrees of methacrylation delivering new insights into PGS‐M morphology

Osteosarcoma growth on trabecular bone mimicking structures manufactured via laser direct write

This paper describes the direct laser write of a photocurable acrylate-based PolyHIPE (High Internal Phase Emulsion) to produce scaffolds with both macro- and microporosity, and the use of these scaffolds in osteosarco-ma-based 3D cell culture. The macroporosity was introduced via the application of stereolithography to produce a clas-sical woodpile structure with struts having an approximate diameter of 200 ?m and pores were typically around 500 ?m in diameter. The PolyHIPE retained its microporosity after stereolithographic manufacture, with a range of pore sizes typically between 10 and 60 ?m (with most pores between 20 and 30 ?m). The resulting scaffolds were suitable substrates for further modification using acrylic acid plasma polymerisation. This scaffold was used as a structural mimic of the trabecular bone and in vitro determination of biocompatibility using cultured bone cells (MG63) demon-strated that cells were able to colonise all materials tested, with evidence that acrylic acid plasma polymerisation im-proved biocompatibility in the long term. The osteosarcoma cell culture on the 3D printed scaffold exhibits different growth behaviour than observed on tissue culture plastic or a flat disk of the porous material; tumour spheroids are ob-served on parts of the scaffolds. The growth of these spheroids indicates that the osteosarcoma behave more akin to in vivo in this 3D mimic of trabecular bone. It was concluded that PolyHIPEs represent versatile biomaterial systems with considerable potential for the manufacture of complex devices or scaffolds for regenerative medicine. In particular, the possibility to readily mimic the hierarchical structure of native tissue enables opportunities to build in vitro models closely resembling tumour tissue

Osteosarcoma growth on trabecular bone mimicking structures manufactured via laser direct write

This paper describes the direct laser write of a photocurable acrylate-based PolyHIPE (High Internal Phase Emulsion) to produce scaffolds with both macro- and microporosity, and the use of these scaffolds in osteosarco-ma-based 3D cell culture. The macroporosity was introduced via the application of stereolithography to produce a clas-sical woodpile structure with struts having an approximate diameter of 200 ?m and pores were typically around 500 ?m in diameter. The PolyHIPE retained its microporosity after stereolithographic manufacture, with a range of pore sizes typically between 10 and 60 ?m (with most pores between 20 and 30 ?m). The resulting scaffolds were suitable substrates for further modification using acrylic acid plasma polymerisation. This scaffold was used as a structural mimic of the trabecular bone and in vitro determination of biocompatibility using cultured bone cells (MG63) demon-strated that cells were able to colonise all materials tested, with evidence that acrylic acid plasma polymerisation im-proved biocompatibility in the long term. The osteosarcoma cell culture on the 3D printed scaffold exhibits different growth behaviour than observed on tissue culture plastic or a flat disk of the porous material; tumour spheroids are ob-served on parts of the scaffolds. The growth of these spheroids indicates that the osteosarcoma behave more akin to in vivo in this 3D mimic of trabecular bone. It was concluded that PolyHIPEs represent versatile biomaterial systems with considerable potential for the manufacture of complex devices or scaffolds for regenerative medicine. In particular, the possibility to readily mimic the hierarchical structure of native tissue enables opportunities to build in vitro models closely resembling tumour tissue

Synergistic effect of type and concentration of surfactant and diluting solvent on the morphology of emulsion templated matrices developed as tissue engineering scaffolds

Emulsion templating is an advantageous route for the fabrication of tissue engineering scaffolds. Emulsions are mostly stabilised using surfactants, and the performances of the surfactants depend on various parameters such as emulsification temperature and the presence of the electrolytes. In this study, we suggest that diluting solvent type also has a dramatic impact on the efficiency of the surfactant and morphology of the polymerised emulsions. For this, morphologies of polycaprolactone methacrylate-based polymerised emulsions, which are designed for tissue engineering applications and in vitro biocompatibilities, were shown by our group, prepared using four different surfactants, and three different solvents were investigated. Results showed that the diluting solvent used in the emulsion composition has a strong impact on the performance of the surfactant and consequently on the morphology of polymerised emulsions. Increasing surfactant concentration and diluting solvent volume have an opposite impact on the characteristics of emulsions. Scaffolds with average pore sizes changing from 10 to 78 μm could be fabricated. Establishing these relations enables us to have control over the overall morphology of polymerised emulsions and precisely engineer them for specific tissue engineering applications by tuning solvent and surfactant type and concentration

Porous microspheres support mesenchymal progenitor cell ingrowth and stimulate angiogenesis

Porous microspheres have the potential for use as injectable bone fillers to obviate the need for open surgery. Successful bone fillers must be able to support vascularisation since tissue engineering scaffolds often cease functioning soon after implantation due to a failure to vascularise rapidly. Here, we test the angiogenic potential of a tissue engineered bone filler based on a photocurable acrylate-based high internal phase emulsion (HIPE). Highly porous microspheres were fabricated via two processes, which were compared. One was taken forward and investigated for its ability to support human mesenchymal progenitor cells and angiogenesis in a chorioallantoic membrane (CAM) assay. Porous microspheres with either a narrow or broad size distribution were prepared via a T-junction microfluidic device or by a controlled stirred-tank reactor of the HIPE water in oil in water (w/o/w), respectively. Culture of human embryonic stem cell-derived mesenchymal progenitor (hES-MP) cells showed proliferation over 11 days and formation of cell-microsphere aggregates. In-vitro, hES-MP cells were found to migrate into microspheres through their surface pores over time. The presence of osteoblasts, differentiated from the hES-MP cells, was evidenced through the presence of collagen and calcium after 30 days. Microspheres pre-cultured with cells were implanted into CAM for 7 days and compared with control microspheres without pre-cultured cells. The hES-MP seeded microspheres supported greater angiogenesis, as measured by the number of blood vessels and bifurcations, while the empty scaffolds attracted host chick cell ingrowth. This investigation shows that controlled fabrication of porous microspheres has the potential to create an angiogenic, bone filling material for use as a cell delivery vehicle