Development of a Pneumatic-Driven Fiber-Shaped Robot Scaffold for Use as a Complex 3D Dynamic Culture System.

Cells can sense and respond to different kinds of continuous mechanical strain in the human body. Mechanical stimulation needs to be included within the in vitro culture system to better mimic the existing complexity of in vivo biological systems. Existing commercial dynamic culture systems are generally two-dimensional (2D) which fail to mimic the three-dimensional (3D) native microenvironment. In this study, a pneumatically driven fiber robot has been developed as a platform for 3D dynamic cell culture. The fiber robot can generate tunable contractions upon stimulation. The surface of the fiber robot is formed by a braiding structure, which provides promising surface contact and adequate space for cell culture. An in-house dynamic stimulation using the fiber robot was set up to maintain NIH3T3 cells in a controlled environment. The biocompatibility of the developed dynamic culture systems was analyzed using LIVE/DEAD™ and alamarBlue™ assays. The results showed that the dynamic culture system was able to support cell proliferation with minimal cytotoxicity similar to static cultures. However, we observed a decrease in cell viability in the case of a high strain rate in dynamic cultures. Differences in cell arrangement and proliferation were observed between braided sleeves made of different materials (nylon and ultra-high molecular weight polyethylene). In summary, a simple and cost-effective 3D dynamic culture system has been proposed, which can be easily implemented to study complex biological phenomena in vitro.

Carbonic Anhydrase Enhanced UV-Crosslinked PEG-DA/PEO Extruded Hydrogel Flexible Filaments and Durable Grids for CO2 Capture.

In this study, poly (ethylene glycol) diacrylate/poly (ethylene oxide) (PEG-DA/PEO) interpenetrating polymer network hydrogels (IPNH) were extruded into 1D filaments and 2D grids. The suitability of this system for enzyme immobilization and CO2 capture application was validated. IPNH chemical composition was verified spectroscopically using FTIR. The extruded filament had an average tensile strength of 6.5 MPa and elongation at break of 80%. IPNH filament can be twisted and bent and therefore is suitable for further processing using conventional textile fabrication methods. Initial activity recovery of the entrapped carbonic anhydrase (CA) calculated from esterase activity, showed a decrease with an increase in enzyme dose, while activity retention of high enzyme dose samples was over 87% after 150 days of repeated washing and testing. IPNH 2D grids that were assembled into spiral roll structured packings exhibited increased CO2 capture efficiency with increasing enzyme dose. Long-term CO2 capture performance of the CA immobilized IPNH structured packing was tested in a continuous solvent recirculation experiment for 1032 h, where 52% of the initial CO2 capture performance and 34% of the enzyme contribution were retained. These results demonstrate the feasibility of using rapid UV-crosslinking to form enzyme-immobilized hydrogels by a geometrically-controllable extrusion process that uses analogous linear polymers for both viscosity enhancement and chain entanglement purposes, and achieves high activity retention and performance stability of the immobilized CA. Potential uses for this system extend to 3D printing inks and enzyme immobilization matrices for such diverse applications as biocatalytic reactors and biosensor fabrication.

Relationship between heat loss indexes and physiological indicators of turnout-related heat strain in mild and hot environments.

A validated physiological manikin method was used to qualify environmentally dependent correlations between firefighter turnout total heat loss (THL) and intrinsic evaporative resistance (Ref) heat strain indexes and core temperature rise in stressful work conducted in mild (25 °C, 65% relative humidity [RH]) and hot (35 °C, 40% RH; 40 °C, 28% RH) conditions. Five turnout suit constructions representing a wide range of breathability were selected. The observed correlations between measured material heat loss and core temperature showed that the THL heat strain index accurately forecast thermal burden in mild environments (<25 °C); while the Ref index provided accurate prediction in hot environments (>35 °C). They showed that the THL index did not predict heat strain in hot work environments. The findings of this study support incorporating both the Ref and THL heat strain indexes as dual metrics for characterizing the heat strain performance of turnout clothing fabrics.

Advances in 3D Gel Printing for Enzyme Immobilization.

Incorporating enzymes with three-dimensional (3D) printing is an exciting new field of convergence research that holds infinite potential for creating highly customizable components with diverse and efficient biocatalytic properties. Enzymes, nature's nanoscale protein-based catalysts, perform crucial functions in biological systems and play increasingly important roles in modern chemical processing methods, cascade reactions, and sensor technologies. Immobilizing enzymes on solid carriers facilitates their recovery and reuse, improves stability and longevity, broadens applicability, and reduces overall processing and chemical conversion costs. Three-dimensional printing offers extraordinary flexibility for creating high-resolution complex structures that enable completely new reactor designs with versatile sub-micron functional features in macroscale objects. Immobilizing enzymes on or in 3D printed structures makes it possible to precisely control their spatial location for the optimal catalytic reaction. Combining the rapid advances in these two technologies is leading to completely new levels of control and precision in fabricating immobilized enzyme catalysts. The goal of this review is to promote further research by providing a critical discussion of 3D printed enzyme immobilization methods encompassing both post-printing immobilization and immobilization by physical entrapment during 3D printing. Especially, 3D printed gel matrix techniques offer mild single-step entrapment mechanisms that produce ideal environments for enzymes with high retention of catalytic function and unparalleled fabrication control. Examples from the literature, comparisons of the benefits and challenges of different combinations of the two technologies, novel approaches employed to enhance printed hydrogel physical properties, and an outlook on future directions are included to provide inspiration and insights for pursuing work in this promising field.

Identifying factors that contribute to structural firefighter heat strain in North America.

This article describes results from a survey of firefighters designed to identify conditions that contribute to heat strain in structural firefighting. Based on responses from about 3000 firefighters across the USA and Canada, the article provides invaluable information about how firefighters associate environmental conditions, work tasks and other factors with heat strain. One-half of firefighters surveyed have experienced heat stress during their service. They can wear fully deployed turnout gear for 2 h or more at the fire scene, reinforcing the importance of turnout suit breathability as a factor in heat strain. Survey results are useful in weighing the comparative value of total heat loss (THL) and evaporative heat resistance (Ref) for predicting turnout-related heat strain. Survey findings support the inclusion of a performance criterion in the National Fire Protection Association 1971 standard for firefighter personal protective equipment based on limiting Ref of turnout materials along with current THL requirement.

The Heterogeneous Effects of Different Environmental Policy Instruments on Green Technology Innovation.

Environmental regulation is an important driving force of green technology innovation. In this paper, environmental policy instruments are classified into three categories: command-control, market-incentive and social-will. Based on the panel data of 30 provinces in China from 2010 to 2017, a fixed effect model and a panel threshold regression model are used to test the heterogeneous effects of different types of environmental policy instruments on the green technology innovation in China. The results show that: (1) Overall, China's environmental policy instruments do not provide sufficient impetus for green technology innovation; (2) The impact of command-control environmental policy instruments on green technology innovation has a single threshold effect. When its intensity exceeds a certain threshold, green technology innovation is improved. The impact of market-incentive environmental policy instruments on the green technology innovation shows a double threshold effect, that is to say, only when its intensity maintained within a reasonable interval, can green technology innovation be promoted by it; (3) There is significant spatial difference in the impact of different types of environmental policy instruments on green technology innovation. In order to induce green technology innovation, it is necessary to formulate a combined and differentiated environmental policy system, while rationally adjusting the strength of different types of environmental policy instruments.

Nanoscale considerations responsible for diverse macroscopic phase behavior in monosubstituted isobutyl-POSS/poly(ethylene oxide) blends.

Nanocomposites prepared by incorporating functionalized polyhedral oligomeric silsesquioxane (POSS) into polymer matrices afford a wide range of versatile hybrid materials for use in technologies ranging from cosmetics and pharmaceuticals to sensors and batteries. Here, we investigate the phase behavior of nanocomposites composed of poly(ethylene oxide) (PEO) and monosubstituted isobutyl POSS (iPOSS) modified with different functional moieties. Microscopic analyses of blends containing these iPOSS variants reveal the existence of different macroscopic morphologies and surface topologies. In the presence of octa-iPOSS, a POSS-rich surface cell motif reminiscent of breath patterns develops, whereas addition of allyl-iPOSS promotes the formation of surface plates. While aminopropyl-iPOSS forms dispersed aggregates, maleamic acid-iPOSS disperses in PEO with little effect on PEO crystal morphology. We perform rotational isomeric state Monte Carlo simulations to discern the effect of monosubstitution on the interaction energy between iPOSS and PEO, and establish the molecular-level origin for these observed differences in phase behavior.