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

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

Optimization of a high internal phase emulsion-based resin for use in commercial vat photopolymerization additive manufacturing

High internal phase emulsions (HIPEs) are potential stereolithography-based resins for producing innovative lightweight porous materials; however, the use of these resins has only been shown in bespoke stereolithography setups. These studies indicated that HIPEs tend to scatter the light during structuring through stereolithography, and can produce poorly defined and low-resolution structures, but the inclusion of light absorbers can drastically increase the printing resolution. In this study, we focused on the inclusion of biocompatible light absorbers within the resin and the compatibility of those resins with a commercial vat photopolymerization additive manufacturing (or stereolithography) setup. A surfactant (hypermer)-stabilized water-in-oil emulsion based on 2-ethylhexyl-acrylate and isobornyl-acrylate was used. For the light absorbers, both hydrophobic (beta-carotene) and hydrophilic (tartrazine) molecules were used, which dissolve in the organic phase and aqueous phase, respectively. It was found that using a combination of both beta-carotene and tartrazine provided the best stereolithography-based 3D printing resolution. In addition, the emulsion was stable for the duration of the printing process and showed a porous polyHIPE structure with open surface porosity. The formulation of these HIPE-based resins permits them to be used in a wide range of applications since complex structures could be fabricated from HIPEs

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

Effect of solvent type on porous structure of emulsion templated poly(glycerol sebacate)-methacrylate

Polymerised emulsion templating is a common method for the fabrication of biomaterials with interconnected porous structures. Here, we present the fabrication of poly(glycerol sebacate)-methacrylate (PGSM) porous structures via emulsion templating. The mixing speed and photoinitiator concentration for emulsions were optimised (350 rpm, 16 wt%, respectively). The resulting emulsion separation before/after mixing and pore morphology of PGSM emulsions was then assessed by altering the emulsion formulation using four different types of diluting solvent (chloroform, dichloromethane, dichloroethane, toluene) for the first time. By altering the type and volume of solvents, the overall pore morphology of polymerised emulsions was tuned

Demonstrating the Potential of Using Bio-Based Sustainable Polyester Blends for Bone Tissue Engineering Applications

YesHealthcare applications are known to have a considerable environmental impact and the use of bio-based polymers has emerged as a powerful approach to reduce the carbon footprint in the sector. This research aims to explore the suitability of using a new sustainable polyester blend (Floreon™) as a scaffold directed to aid in musculoskeletal applications. Musculoskeletal problems arise from a wide range of diseases and injuries related to bones and joints. Specifically, bone injuries may result from trauma, cancer, or long-term infections and they are currently considered a major global problem in both developed and developing countries. In this work we have manufactured a series of 3D-printed constructs from a novel biopolymer blend using fused deposition modelling (FDM), and we have modified these materials using a bioceramic (wollastonite, 15% w/w). We have evaluated their performance in vitro using human dermal fibroblasts and rat mesenchymal stromal cells. The new sustainable blend is biocompatible, showing no differences in cell metabolic activity when compared to PLA controls for periods 1-18 days. FloreonTM blend has proven to be a promising material to be used in bone tissue regeneration as it shows an impact strength in the same range of that shown by native bone (just under 10 kJ/m2) and supports an improvement in osteogenic activity when modified with wollastonite.We would like to acknowledge the Medical Research Council in the UK (MRC) for funding this research throughout a MRC Proximity to Discovery award (P2D) with grant number MC_PC_16084. We would also like to acknowledge CONACYT for funding DH RamosRodriguez’s work

Tissue Engineering at the Blood-Contacting Surface: A Review of Challenges and Strategies in Vascular Graft Development.

Tissue engineered vascular grafts (TEVGs) are beginning to achieve clinical success and hold promise as a source of grafting material when donor grafts are unsuitable or unavailable. Significant technological advances have generated small-diameter TEVGs that are mechanically stable and promote functional remodeling by regenerating host cells. However, developing a biocompatible blood-contacting surface remains a major challenge. The TEVG luminal surface must avoid negative inflammatory responses and thrombogenesis immediately upon implantation and promote endothelialization. The surface has therefore become a primary focus for research and development efforts. The current state of TEVGs is herein reviewed with an emphasis on the blood-contacting surface. General vascular physiology and developmental challenges and strategies are briefly described, followed by an overview of the materials currently employed in TEVGs. The use of biodegradable materials and stem cells requires careful control of graft composition, degradation behavior, and cell recruitment ability to ensure that a physiologically relevant vessel structure is ultimately achieved. The establishment of a stable monolayer of endothelial cells and the quiescence of smooth muscle cells are critical to the maintenance of patency. Several strategies to modify blood-contacting surfaces to resist thrombosis and control cellular recruitment are reviewed, including coatings of biomimetic peptides and heparin