Surfaces play a vial role in biology and medicine with most biological reactions occurring at surfaces and interfaces. The foundations, evolution, and impact of biomedical surface science are ...discussed. In the 19th century, the first observations were made that surfaces control biological reactions. The advancements in surface science instrumentation that have occurred in the past quarter of a century have significantly increased our ability to characterize the surface composition and molecular structure of biomaterials. Similar advancements have occurred in material science and molecular biology. The combination of these advances have allowed the development of the biological model for surface science, where the ultimate goal is to gain a detailed understanding of how the surface properties of a material control the biological reactivity of a cell interacting with that surface. Numerous examples show that the surface properties of a material are directly related to in vitro biological performance such as protein adsorption and cell growth. The challenge is to fully develop the biological model for surface science in the highly complex and interactive in vivo biological environment. Examples of state-of-the-art biomedical surface science studies on surface chemical state imaging, molecular recognition surfaces, adsorbed protein films, and hydrated surfaces are presented. Future directions and opportunities for surface scientists working in biomedical research include exploiting biological knowledge, biomimetics, precision immobilization, self-assembly, nanofabrication, smart surfaces, and control of non-specific reactions.
Abstract Since pore size and geometry strongly impact cell behavior and in vivo reaction, the ability to create scaffolds with a wide range of pore geometries that can be tailored to suit a ...particular cell type addresses a key need in tissue engineering. In this contribution, we describe a novel and simple technique to design porous, degradable poly(2-hydroxyethyl methacrylate) hydrogel scaffolds with well-defined architectures using a unique photolithography process and optimized polymer chemistry. A sphere-template was used to produce a highly uniform, monodisperse porous structure. To create a patterned and porous hydrogel scaffold, a photomask and initiating light were employed. Open, vertical channels ranging in size from 360±25 to 730±70 μm were patterned into ∼700 μm thick hydrogels with pore diameters of 62±8 or 147±15 μm. Collagen type I was immobilized onto the scaffolds to facilitate cell adhesion. To assess the potential of these novel scaffolds for tissue engineering, a skeletal myoblast cell line (C2C12) was seeded onto scaffolds with 147 μm pores and 730 μm diameter channels, and analyzed by histology and digital volumetric imaging. Cell elongation, cell spreading and fibrillar formation were observed on these novel scaffolds. In summary, 3D architectures can be patterned into porous hydrogels in one step to create a wide range of tissue engineering scaffolds that may be tailored for specific applications.
In the last twenty years, policy prescriptions for addressing the global crisis in fisheries have centred on strengthening fisheries governance through clarifying exclusive individual or community ...rights of access to fishery resources. With a focus on small‐scale developing‐country fisheries in particular, we argue that basing the case for fishery governance reform on assumed economic incentives for resource stewardship is insufficient when there are other sources of insecurity in people’s lives that are unrelated to the state of fishery resources. We argue that more secure, less vulnerable fishers make more effective and motivated fishery managers in the context of participatory or rights‐based fisheries governance, and we further suggest that insecurity among fishers living in poverty can be most effectively addressed by social and political development that invokes the existing legal framework supporting the Universal Declaration of Human Rights. This perspective goes well beyond the widely advocated notion of ‘rights‐based fishing’ and aligns what fishery sector analysts call the ‘rights‐based approach’ with the same terminology used in the context of international development. Embedding the fisheries governance challenge within a broader perspective of human rights enhances the chances of achieving both human development and resource sustainability outcomes in small‐scale fisheries of developing countries.
The vast development opportunities offered by the world’s coasts and oceans have attracted the attention of governments, private enterprises, philanthropic organizations and international ...conservation organizations. High-profile dialogue and policy decisions on ocean futures are informed largely by economic and ecological research. Key insights from the social sciences raise concerns for food and nutrition security, livelihoods and social justice but these have yet to gain traction with investors and the policy discourse on transforming ocean governance. The largest group of ocean-users – women and men who service, fish and trade from small-scale fisheries – argue they have been marginalized from dialogue between international environmental and economic actors determining strategies for ocean futures. Blue Economy or Blue Growth initiatives see the ocean as the new economic frontier and imply there is alignment with social objectives and small-scale fisheries concerns. Deeper analysis reveals fundamental differences in ideologies, priorities and approaches. We argue that small-scale fisheries are being subtly and overtly squeezed for geographic, political and economic space by larger scale economic and environmental conservation interests, jeopardizing the substantial benefits small-scale fisheries provide through livelihoods of millions of women and men, food for around four billion consumers globally, and in the developing world, a key source of micro-nutrients and protein for over a billion low-income consumers. Here we bring insights from social science and small-scale fisheries to explore how ocean governance might better account for social dimensions of fisheries.
The Linac Coherent Light Source (LCLS) is an X-ray free-electron laser at the SLAC National Accelerator Laboratory, which has been operating since 2009 for a wide range of scientific research. The ...free-electron laser process at LCLS is based on self-amplified spontaneous emission (SASE) where spontaneous emission from the initial electron beam shot noise is amplified by its interaction with the electrons over a long magnetic undulator. Although SASE is very effective, producing tremendously powerful, ultrashort X-ray beams, the start-up from noise leaves poor temporal coherence and a broad, noisy spectrum. We present experimental results of a new method, suggested by colleagues at DESY, allowing self-seeding using X-rays from the first half of the undulator to seed the second half through a diamond-based monochromator, producing near Fourier-transform-limited X-ray pulses with 0.4-0.5 eV bandwidth at 8-9 keV. These results demonstrate self-seeding at ångstrom wavelengths with a relative bandwidth reduction of 40-50 with respect to SASE.
Abstract Extracellular matrix (ECM) scaffolds prepared from different tissue sources or using different methods have been demonstrated to have distinctive effects upon cell adhesion patterns and the ...ability to support and maintain differentiated phenotypes. It is unknown whether the molecular composition or the ultrastructure of the ECM plays a greater role in determining the phenotype of the cells with which it comes into contact. However, when implanted, the topology and ligand landscape of the material will determine the host molecules that bind and the type and behavior of cells that mediate the host response. Therefore, a comprehensive understanding of surface characteristics is essential in the design of scaffolds for specific clinical applications. The surface characteristics of ECM scaffolds derived from porcine urinary bladder, small intestine, and liver as well as the effects of two commonly used methods of chemical cross-linking upon UBM were investigated. Electron microscopy and time of flight secondary ion mass spectroscopy were used to examine the surface characteristics of the scaffolds. The results show that ECM scaffolds have unique morphologic and structural properties which are dependant on the organ or tissue from which the scaffold is harvested. Furthermore, the results show that the surface characteristics of an ECM scaffold are changed through chemical cross-linking.
A study of protein resistance of oligo(ethylene glycol) (OEG), HS(CH2)11(OCH2CH2) n OH (n = 2, 4, and 6), self-assembled monolayers (SAMs) on Au(111) surfaces is presented here. Hydroxyl-terminated ...OEG-SAMs are chosen to avoid the hydrophobic effect observed with methyl-terminated OEG-SAMs, particularly at high packing densities. The structure of the OEG-SAM surfaces is controlled by adjusting the assembly solvent. These SAMs were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Protein adsorption on these surfaces was investigated by surface plasmon resonance (SPR). OEG-SAMs assembled from mixed ethanol and water solutions show higher packing density on gold than those from pure ethanol solution. For EG2OH- and EG4OH-SAMs, proteins (i.e., fibrinogen and lysozyme) adsorb more on the densely packed SAMs prepared from mixed ethanol and water solutions, while EG6OH-SAMs generally resist protein adsorption regardless of the assembly solvent used.
In this paper, we propose a new approach to measuring ultrafast dynamics with free-electron lasers (FELs). Ultrafast experiments are among the most promising avenues of research at x-ray FELs, with ...the potential to reveal the chemical dynamics of charge separation, conical intersection crossing, and biologically mediated reactions. Pump-probe scanning is the standard approach to measure dynamics at x-ray FELs, but at the shortest timescales, and particularly for x-ray pump, x-ray probe experiments, the scans require challenging beam setups and can introduce systematic errors. Here, we propose an alternative approach using the randomness of the self-amplified spontaneous emission (SASE) process to drive many simultaneous pump-probe experiments on each shot. Measuring the fluctuations in the incident beam’s time profile on a shot-to-shot basis enables the reconstruction of ultrafast dynamics down to the coherence length of the FEL without the need for pump-probe scans. Because of similarity to ghost imaging, in which spatial properties are reconstructed by measuring the incident probe’s transverse properties, we call this “pump-probe ghost imaging.” In this paper, we describe the method and simulate an example experiment. We also describe an alternative implementation that uses only spectral measurements, avoiding the need for direct time-domain diagnostics and extending the method to the attosecond regime.
Abstract Fibrin has been long used as an effective scaffolding material to grow a variety of cells and tissue constructs. It has been utilized mainly as a hydrogel in varying concentrations to ...provide an environment in which suspended cells work to rearrange the fibers and lay down their own extracellular matrix. For these fibrin hydrogels to be useful in many tissue-engineering applications, the gels must be cultured for long periods of time in order to increase their mechanical strength to the levels of native tissues. High concentrations of fibrinogen increase the mechanical strength of fibrin hydrogels, but at the same time reduce the ability of cells within the scaffold to spread and survive. We present a method to create a microporous, nanofibriliar fibrin scaffold that has controllable pore size, porosity, and microstructure for applications in tissue engineering. Fibrin has numerous advantages as a scaffolding material as it is normally used by the body as temporary scaffolding for tissue regeneration and healing, and can be autologously sourced. We present here a scaffolding process which enhances the mechanical properties of the fibrin hydrogel by forming it surrounding poly(methyl-methacrylate) beads, then removing the beads with acetone to form an interconnected microporous network. The acetone serves the dual purpose of precipitating and fixing the fibrinogen-based scaffolds as well as adding strength to the network during polymer bead removal. Effects of fibrinogen concentration and time in acetone were examined as well as polymerization with thrombin. A natural crosslinker, genipin, was also used to add strength to the scaffolds, producing a Young's modulus of up to 184±5 kPa after 36 h of reaction. Using these methods we were able to produce microporous fibrin scaffolds that support cell growth and have mechanical properties similar to many native tissues.
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