The effects of varying poly(ethylene glycol) hydrogel crosslinking density and the crosslinking mechanism on protein accumulation in three-dimensional hydrogels

a b s t r a c t Matrix stiffness has been shown to play an important role in modulating various cell fate processes such as differentiation and cell cycle. Given that the stiffness can be easily tuned by varying the crosslinking density, poly(ethylene glycol) (PEG) hydrogels have been widely used as an artificial cell niche. However, little is known about how changes in the hydrogel crosslinking density may affect the accumulation of exogenous growth factors within 3-D hydrogel scaffolds formed by different crosslinking mechanisms. To address such shortcomings, we measured protein diffusivity and accumulation within PEG hydrogels with varying PEG molecular weight, concentration and crosslinking mechanism. We found that protein accumulation increased substantially above a critical mesh size, which was distinct from the protein diffusivity trend, highlighting the importance of using protein accumulation as a parameter to better predict the cell fates in addition to protein diffusivity, a parameter commonly reported by researchers studying protein diffusion in hydrogels. Furthermore, we found that chain-growth-polymerized gels allowed more protein accumulation than step-growth-polymerized gels, which may be the result of network heterogeneity. The strategy used here can help quantify the effects of varying the hydrogel crosslinking density and crosslinking mechanism on protein diffusion in different types of hydrogel. Such tools could be broadly useful for interpreting cellular responses in hydrogels of varying stiffness for various tissue engineering applications

Long-Term Controlled Protein Release from Poly(Ethylene Glycol) Hydrogels by Modulating Mesh Size and Degradation

Poly(ethylene glycol) (PEG)-based hydrogels are popular biomaterials for protein delivery to guide desirable cellular fates and tissue repair. However, long-term protein release from PEGbased hydrogels remains challenging. Here, we report a PEG-based hydrogel platform for long term protein release, which allows efficient loading of proteins via physical entrapment. Tuning hydrogel degradation led to increase in hydrogel mesh size and gradual release of protein over 60 days of with retained bioactivity. Importantly, this platform does not require the chemical modification of loaded proteins, and may serve as a versatile tool for longterm delivery of a wide range of proteins for drugdelivery and tissue-engineering applications

Recurrence of ameloblastoma involving iliac bone graft after 16 years

SummaryThe condition with recurrence of ameloblastoma in autogenous iliac bone grafts is very rare. This report presents such a case from a 55-year-old female

An animal model of SARS produced by infection of Macaca mulatta with SARS coronavirus.

A new SARS animal model was established by inoculating SARS coronavirus (SARS-CoV) into rhesus macaques (Macaca mulatta) through the nasal cavity. Pathological pulmonary changes were successively detected on days 5-60 after virus inoculation. All eight animals showed a transient fever 2-3 days after inoculation. Immunological, molecular biological, and pathological studies support the establishment of this SARS animal model. Firstly, SARS-CoV-specific IgGs were detected in the sera of macaques from 11 to 60 days after inoculation. Secondly, SARS-CoV RNA could be detected in pharyngeal swab samples using nested RT-PCR in all infected animals from 5 days after virus inoculation. Finally, histopathological changes of interstitial pneumonia were found in the lungs during the 60 days after viral inoculation: these changes were less marked at later time points, indicating that an active healing process together with resolution of an acute inflammatory response was taking place in these animals. This animal model should provide insight into the mechanisms of SARS-CoV-related pulmonary disease and greatly facilitate the development of vaccines and therapeutics against SARS

Numerical and Experimental Investigations of the Effect of Melt Delivery Nozzle Design on the Open- to Closed-Wake Transition in Closed-Coupled Gas Atomization

The single-phase gas-flow behavior of a closed-coupled gas atomization was investigated with four different melt nozzle tip designs with two types of gas die. Particular attention was paid to the open- to closed-wake transition. Experimental Schlieren imaging and numerical modeling techniques were employed, with good agreement between the two being found in relation to the wake closure pressure. It was found that the melt nozzle tip design had a significant impact on the WCP, as did the type of die used, with a convergent–divergent gas die giving significantly high WCPs

Human MIEF1 recruits Drp1 to mitochondrial outer membranes and promotes mitochondrial fusion rather than fission

Mitochondrial morphology depends on the balance between fission and fusion events. This study identifies a receptor for the fission factor Drp1 within the mitochondrial outer membrane, which inhibits Drp1-mediated fission and activates fusion

Atmospheric pollution and human health in a Chinese megacity (APHH-Beijing) programme. Final report

In 2016, over 150 UK and Chinese scientists joined forces to understand the causes and impacts - emission sources, atmospheric processes and health effects - of air pollution in Beijing, with the ultimate aim of informing air pollution solutions and thus improving public health. The Atmospheric Pollution and Human Health in a Chinese Megacity (APHH-Beijing) research programme succeeded in delivering its objectives and significant additional science, through a large-scale, coordinated multidisciplinary collaboration. In this report are highlighted some of the research outcomes that have potential implications for policymaking

Service Quality in Cloud Gaming: Instrument Development and Validation

AbstractPurpose - The global market for cloud gaming is growing rapidly. How gamers evaluate the service quality of this emerging form of cloud service has become a critical issue for both researchers and practitioners. Building on the literature on service quality and software as a service, this study develops and validates a gamer-centric measurement instrument for cloud gaming service quality.Design/methodology/approach - A three-step measurement instrument development process, including item generation, scale development, and instrument testing, was adopted to conceptualize and operationalize cloud gaming service quality.Findings - Cloud gaming service quality consists of two second-order constructs of support service quality and technical service quality with seven first-order dimensions, namely rapport, responsiveness, reliability, compatibility, ubiquity, smoothness, and comprehensiveness. The instrument exhibits desirable psychometric properties.Practical implications - Practitioners can use this new measurement instrument to evaluate gamers’ perceptions toward their service and to identify areas for improvement. Originality/value - This study contributes to the service quality literature by utilizing qualitative and quantitative approaches to develop and validate a new measurement instrument of service quality in the context of cloud gaming and by identifying new dimensions (compatibility, ubiquity, smoothness, and comprehensiveness) specific to it

Hydrogels with Dual Gradients of Mechanical and Biochemical Cues for Deciphering Cell-Niche Interactions

Cell niche is a multifactorial environment containing complex interactions between biochemical and physical cues. Although extensive studies have examined the effects of biochemical or physical cues alone on cell fate, how biochemical and mechanical signals interact to influence cell fates remains largely unknown. To address this challenge, here we report a polyethylene glycol-based gradient hydrogel platform as biomimetic cell niche containing independently tunable matrix stiffness and biochemical ligand density. The versatility of this platform is demonstrated by fabricating and characterizing single gradient or orthogonally aligned dual gradient hydrogels. These gradients result in differential elongation and spreading of human fibroblasts. Both hydrogel stiffness and biochemical ligand density are independently tunable by sequential photopolymerization. By controlling light exposure, a broad range of hydrogel stiffness and different types/doses of biochemical ligands can be incorporated. Such tunability facilitates customization of this platform for investigating complex cell-niche interactions associated with various cell types, such as stem cells and cancer cells. The outcomes of such studies may help identify optimal niche cues to promote desiralbe stem fates and tissue regeneration or inhibit diseases progression

Adaptation of migratory Tibetan antelope to infrastructure development

The Tibetan antelope (Pantholops hodgsonii) is a migratory ungulate species that inhabits the Qinghai–Tibet Plateau. In recent years, the population of Tibetan antelope has steadily increased owing to rigorous protection measures to safeguard the species from commercial poaching. Currently, infrastructure development, competition with domestic livestock, and predation are the principal factors threatening the survival of Tibetan antelope. Our study found that migratory Tibetan antelope can adapt to the development of infrastructure over time, decreasing the potential negative impacts of such developments. We, therefore, urge infrastructure development companies to incorporate wildlife corridors that enable free movement of wildlife populations, particularly for migratory species