Cardiovascular devices such as vascular grafts, stents, and heart valves have been widely used to treat cardiovascular diseases. The failure of these devices is usually initiated by the formation of ...thrombus and neointima on the device surfaces. Antithrombogenic surface modifications have been employed to improve the performance of these devices. In addition to biochemical modifications, tissue engineering approaches hold the promise to fabricate nonthrombogenic biological substitutes for cardiovascular tissues and devices. Endothelial cells (ECs) and stem cells have been used to cover blood-contacting surfaces. Furthermore, for tissue-engineered vascularized tissues and organs, a nonthrombogenic vascular network is essential for mass transfer and the integration of functional tissues and organs into the host upon transplantation. This review discusses the advances in antithrombogenic approaches for surface modifications and cardiovascular tissue engineering.
Synthetic small diameter vascular grafts have a high failure rate, and endothelialization is critical for preventing thrombosis and graft occlusion. A promising approach is in situ tissue ...engineering, whereby an acellular scaffold is implanted and provides stimulatory cues to guide the in situ remodeling into a functional blood vessel. An ideal scaffold should have sufficient binding sites for biomolecule immobilization and a mechanical property similar to native tissue. Here we developed a novel method to blend low molecular weight (LMW) elastic polymer during electrospinning process to increase conjugation sites and to improve the mechanical property of vascular grafts. LMW elastic polymer improved the elasticity of the scaffolds, and significantly increased the amount of heparin conjugated to the micro/nanofibrous scaffolds, which in turn increased the loading capacity of vascular endothelial growth factor (VEGF) and prolonged the release of VEGF. Vascular grafts were implanted into the carotid artery of rats to evaluate the in vivo performance. VEGF treatment significantly enhanced endothelium formation and the overall patency of vascular grafts. Heparin coating also increased cell infiltration into the electrospun grafts, thus increasing the production of collagen and elastin within the graft wall. This work demonstrates that LMW elastic polymer blending is an approach to engineer the mechanical and biological property of micro/nanofibrous vascular grafts for in situ vascular tissue engineering.
There is a need for increased renewable energy to meet net-zero targets and decarbonise the economy. Harnessing the predictable power of the tides with tidal stream turbines can contribute to this. ...Tidal energy is a nascent technology with higher costs at present. However, cost reductions have been observed with an increased deployment in other renewable energy technologies that have received financial support, and it is postulated that similar will happen with tidal energy. The first tidal stream projects have been awarded market support in the UK through the Contracts for Difference (CfD) scheme, with almost 100 MW expected to be commissioned by 2028. This work uses learning rates to investigate how much investment in ongoing market support might be needed to achieve cost reductions through subsidised deployment alongside research and innovation. Using a range of informed ‘what if?’ scenarios, it shows sensitivity to key inputs. The results show that the support needed is most sensitive to the learning rate, reducing it from 15% to 12.5% or 10% doubles or more than quadruples the investment required, respectively. The support is also highly dependent on the starting cost from which learning occurs, taken as the CfD Strike Price in 2025. Varying this between 156 and 220 GBP/MWh results in total investment of GBP 6.7 and 22.3 bn, respectively. Most importantly, a balance is needed between subsidising deployment to drive down costs through learning and funding innovation to maintain a high learning rate.
Ischemic heart disease represents the leading cause of death worldwide. Heart failure following myocardial infarction (MI) is associated with severe fibrosis formation and cardiac remodeling. ...Recently, injectable hydrogels have emerged as a promising approach to repair the infarcted heart and improve heart function through minimally invasive administration. Here, a novel injectable human amniotic membrane (hAM) matrix is developed to enhance cardiac regeneration following MI. Human amniotic membrane is isolated from human placenta and engineered to be a thermoresponsive, injectable gel around body temperature. Ultrasound-guided injection of hAM matrix into rat MI hearts significantly improves cardiac contractility, as measured by ejection fraction (EF), and decrease fibrosis. The results of this study demonstrate the feasibility of engineering as an injectable hAM matrix and its efficacy in attenuating degenerative changes in cardiac function following MI, which may have broad applications in tissue regeneration.
Exercise induces beneficial responses in the brain, which is accompanied by an increase in BDNF, a trophic factor associated with cognitive improvement and the alleviation of depression and anxiety. ...However, the exact mechanisms whereby physical exercise produces an induction in brain Bdnf gene expression are not well understood. While pharmacological doses of HDAC inhibitors exert positive effects on Bdnf gene transcription, the inhibitors represent small molecules that do not occur in vivo. Here, we report that an endogenous molecule released after exercise is capable of inducing key promoters of the Mus musculus Bdnf gene. The metabolite β-hydroxybutyrate, which increases after prolonged exercise, induces the activities of Bdnf promoters, particularly promoter I, which is activity-dependent. We have discovered that the action of β-hydroxybutyrate is specifically upon HDAC2 and HDAC3, which act upon selective Bdnf promoters. Moreover, the effects upon hippocampal Bdnf expression were observed after direct ventricular application of β-hydroxybutyrate. Electrophysiological measurements indicate that β-hydroxybutyrate causes an increase in neurotransmitter release, which is dependent upon the TrkB receptor. These results reveal an endogenous mechanism to explain how physical exercise leads to the induction of BDNF.
Cost reductions in nascent forms of Renewable Energy Technology (RET) are essential for them to contribute to the energy mix. Policy intervention can facilitate this cost reduction; however, this may ...require a significant investment from the public sector. These cost reductions fall into two broad categories: (1) incremental cost reductions through continual improvements to existing technologies, and (2) radical innovation where technologies that significantly differ from the incumbents are developed. This study presents a modelling methodology to integrate radical innovation in RET experience curve and learning investment analysis, using wave energy as an example nascent RET. This aims to quantify the potential effects of radical innovation on the learning investment, allowing the value of successful innovation to be better analysed. The study highlights the value offered by radical innovations in long-term deployment scenarios for wave energy. This suggests that high-risk R&D efforts in nascent RET sectors, even with low success rates, could still present significant expected value in offsetting future revenue support.
Developing new wave energy technologies is risky, costly and time-consuming. The large diversity of concepts, components and evaluation criteria creates a vast design space of potentially feasible ...solutions. This paper aims to introduce a novel methodology for the holistic assessment of wave energy capabilities in various market applications based on sound Systems Engineering methods. The methodology provides a consistent hierarchy of performance metrics relevant to the given system of reference, design activity and development stage under consideration as a means to scrutinise wave energy requirements. Full traceability of system requirements and performance metrics is then facilitated by multi-criteria decision tools and aggregation logic, respectively. The qualitative assessment in the case studies has resulted in very different rankings of System Drivers and Stakeholders for the two market applications considered. However, the Stakeholder Requirements and Functional Requirements present a small variation in the weights for the two application markets which results in a quantitative assessment with very similar Global Merit. Finally, the performance benchmark using the Commercial Attractiveness and Technical Achievability concepts enables a more objective comparison in the utility-scale and remote generation markets and a way to concentrate innovation efforts before proceeding to the next development stage.
Using learning curves as an analytical tool for technology forecasting involves making assumptions over a range of key uncertainties, often implicitly. In this paper, we present an explicit treatment ...of the key uncertainties involved in learning rates' analyses of marine energy innovation (wave and tidal stream) — technology fields attracting considerable interest, but whose commercial prospects depends on substantial learning and cost reduction. Taking a simple single factor learning rate model, we describe a range of plausible learning investments required so that marine energy technologies become cost-competitive with their ‘benchmark’ technology: offshore wind. Our analysis highlights the sensitivity of marine energy to three key parameters: the capital cost of first devices, the level of deployment before sustained cost reduction emerges, and the average rate of cost reduction with deployment (learning rate). Figures often quoted within the marine energy sector for the parameters of starting cost, learning rate, and capacity at which sustained cost reduction occurs (metrics conventionally used for learning rate analysis) can be seen to represent very attractive scenarios. The intention of this paper is to display that even small changes to input assumptions can have a dramatic effect on the overall investment required for a sector to reach parity with benchmark technologies. In the short term, reaching cost competitiveness with offshore wind is a necessity if marine energy is to reach commercialisation. Additionally, an assessment of the plausible total investment (and inherent uncertainties) in a global wave and tidal deployment scenario will be presented. The paper also considers the implications of these uncertainties for marine energy innovation management. While the benchmark against offshore wind will generally be used as a performance indicator, in order to achieve similar and sustained cost reductions to other, more mature, renewable energy technologies (and thus achieve a competitive price for marine technologies, securing their place within the energy mix), the marine energy sector needs a targeted innovation focus to fulfil the desired objectives, and a development pathway very different to offshore wind must be used.
•Small variations in inputs can have a significant impact on the plausible learning investment.•Cost and performance uncertainties have the potential to ‘make or break’ the marine renewable energy industry.•Marine renewable industry requires an innovation strategy different to offshore wind.•Innovation is fundamental to achieving and maintaining high learning rates.
This work investigates potential cost reduction trajectories of three emerging offshore renewable energy technologies (floating offshore wind, tidal stream, and wave) with respect to meeting ...ambitious cost targets set out in the Strategic Energy Technology Implementation Plans (SET-Plans) for Offshore Wind and Ocean Energy. A methodology is presented which calculates target costs for current early-stage devices, starting from the 2030 SET-Plan levelised cost targets. Component-based experience curves have been applied as part of the methodology, characterised through the comparative maturity level of each technology-specific cost centre. The resultant early-stage target costs are then compared with actual costs for current devices to highlight where further cost reduction is still required. It has been found that innovation and development requirements to reach these targets vary greatly between different technologies, based on their current level of technological maturity. Future funding calls and programmes should be designed with these variables in mind to support innovative developments in offshore renewables. The method presented in this paper has been applied to publicly available cost data for emerging renewable technologies and is fully adaptable to calculate the innovation requirements for specific early-stage renewable energy devices.
Energy system scenarios and modelling exercises may under-represent the learning potential of emerging technologies such as marine energy. The research described here was devised to represent this ...potential, and thereby explore the possible role of marine energy in future energy systems. The paper describes a scenario for the accelerated development of marine energy technology, and the incorporation of this scenario into wider scenarios of UK energy system decarbonisation from now to 2050. The scenarios suggest that the accelerated development of marine energy could contribute significantly to the decarbonisation of energy supply in the UK, especially over the medium to long term. However, this is predicated on sustained innovation, learning and cost reduction over time. Encouragingly, a number of recently established policy support programmes are now beginning to stimulate the development of marine energy in Scotland, the UK and beyond. As the paper discusses, building on these initiatives, and ‘realising’ the accelerated development of marine energy, present a number of challenges, and will increasingly require international efforts. However, the potential rewards are very substantial.
► Accelerated development of marine energy impacts UK energy system decarbonisation. ► Realising the accelerated marine energy scenario will require sustained support. ► Innovation support for marine energy has changed over time due to policy learning. ► Marine acceleration requires a co-evolution of development and deployment.
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