Bioinspired Processing: Complex Coacervates as Versatile Inks for 3D Bioprinting

3D bioprinting is a powerful fabrication technique in biomedical engineering, which is currently limited by the number of available materials that meet all physicochemical and cytocompatibility requirements for biomaterial inks. Inspired by the key role of coacervation in the extrusion and spinning of many natural materials, hyaluronic acid-chitosan complex coacervates are proposed here as tunable biomaterial inks. Complex coacervates are obtained through an associative liquid-liquid phase separation driven by electrostatic attraction between oppositely charged macromolecules. They offer bioactive properties and facile modulation of their mechanical properties through mild physicochemical changes in the environment, making them attractive for 3D bioprinting. Fine-tuning the salt concentration, pH, and molecular weight of the constituent polymers results in biomaterial inks that are printable in air and water. The biomaterial ink, initially a viscoelastic fluid, transitions into a viscoelastic solid upon printing due to dehydration (for printing in air) or due to a change in pH and ionic composition (for printing in solution). Consequently, scaffolds printed using the complex coacervate inks are stable without the need for post-printing processing. Fabricated cell culture scaffolds are cytocompatible and show long-term topological stability. These results pave the way to a new class of easy-to-handle tunable biomaterials for biofabrication.

Stress responses across the scales of life: Towards a universal theory of biological stress

Although biological systems are more complex and can actively respond to their environment, an effective entry point to the development of a universal theory of biological stress are the physical concepts of stress and strain. If you apply stress to the end of a beam of steel, strain will accumulate within that steel beam. If the stress is weak, that strain will disappear when the force is removed and the beam will return to its original state of form and functionality. If the stress is more severe, the strain becomes permanent and the beam will be deformed, potentially losing some degree of functionality. In extremely stressful situations, the beam will break and lose most or all of its original functional capabilities. Although this stress-strain theory applies to the abiotic, stress and strain are also rules of life and directly relate to the form and function of living organisms. The main difference is that life can react and adjust to stress and strain to maintain homeostasis within a range of limits. Here, we summarize the rules of stress and strain in living systems ranging from microbes to multicellular organisms to ecosystems with the goal of identifying common features that may underlie a universal biological theory of stress. We then propose to establish a range of experimental, observational, and analytical approaches to study stress across scales, including synthetic microbial communities that mimic many of the essential characteristics of living systems, thereby enabling a universal theory of biological stress to be experimentally validated without the constraints of timescales, ethics, or cost found when studying other species or scales of life. Although the range of terminology, theory, and methodology used to study stress and strain across the scales of life presents a formidable challenge to creating a universal theory of biological stress, working towards such a theory that informs our understanding of the simultaneous and interconnected unicellular, multicellular, organismal, and ecosystem stress responses is critical as it will improve our ability to predict how living systems respond to change, thus informing solutions to current and future environmental and human health challenges.

Biobased Acrylate Photocurable Resin Formulation for Stereolithography 3D Printing

To facilitate the ongoing transition toward a circular economy, the availability of renewable materials for additive manufacturing becomes increasingly important. Here, we report the successful fabrication of complex shaped prototypes from biobased acrylate photopolymer resins, employing a commercial stereolithography apparatus (SLA) 3D printer. Four distinct resins with a biobased content ranging from 34 to 67% have been developed. All formulations demonstrated adequate viscosity and were readily polymerizable by the UV-laser-based SLA process. Increasing the double-bond concentration within the resin results in stiff and thermally resilient 3D printed products. High-viscosity resins lead to high-resolution prototypes with a complex microarchitecture and excellent surface finishing, comparable to commercial nonrenewable resins. These advances can facilitate the wide application of biobased resins for construction of new sustainable products via stereolithographic 3D printing methods.

The Recent Developments in Biobased Polymers toward General and Engineering Applications: Polymers that are Upgraded from Biodegradable Polymers, Analogous to Petroleum-Derived Polymers, and Newly Developed

The main motivation for development of biobased polymers was their biodegradability, which is becoming important due to strong public concern about waste. Reflecting recent changes in the polymer industry, the sustainability of biobased polymers allows them to be used for general and engineering applications. This expansion is driven by the remarkable progress in the processes for refining biomass feedstocks to produce biobased building blocks that allow biobased polymers to have more versatile and adaptable polymer chemical structures and to achieve target properties and functionalities. In this review, biobased polymers are categorized as those that are: (1) upgrades from biodegradable polylactides (PLA), polyhydroxyalkanoates (PHAs), and others; (2) analogous to petroleum-derived polymers such as bio-poly(ethylene terephthalate) (bio-PET); and (3) new biobased polymers such as poly(ethylene 2,5-furandicarboxylate) (PEF). The recent developments and progresses concerning biobased polymers are described, and important technical aspects of those polymers are introduced. Additionally, the recent scientific achievements regarding high-spec engineering-grade biobased polymers are presented.

Pyridyl-1,2,4-triazole diphenyl boron complexes as efficient tuneable blue emitters

The detection of nuclear radiation necessitates the availability of new generations of tunable blue emitting fluorophores with high emission quantum yields. Here we show that pyridyl-1,2,4-triazole based diphenyl boron complexes can provide highly tuneable emission through facile modification of the C5 position of the 1,2,4-triazolato ring. The series of complexes prepared show a wide range of emission from near-UV to green, enabling fine control over the spectral overlap with detectors used in scintillator technology.

Nitrogen stable isotope composition of leaves and roots of plants growing in a forest and a meadow

In controlled N-nutrition experiments, differences in delta15N composition of leaves and roots are regularly found. In this paper we report results from a survey of nitrogen stable isotope signatures of leaves and roots of 16 plant species growing under natural conditions in a meadow and a forest understorey, which differed in nitrate and ammonium availability. Significant differences between leaf and root were observed. The range of delta15N [leaf-root] values was -0.97 to +0.86 per thousand, small compared to published values from controlled N-nutrition experiment, but almost as large as the range of leaf delta15N values (-1.04 to +1.08 per thousand). Forbs showed the largest differences between leaves and roots and showed a significant difference with respect to habitat. Grasses and legumes did not show significant differences in delta15N [leaf-root] between the two habitats. Care must be taken when using leaf delta15N values as representative for whole-plant 15N composition in these two habitats.

Rationalizations and defensive attributions for high-risk sex among heterosexuals

A group of 39 respondents high at risk for HIV and a group of 39 respondents low at risk for HIV were selected from a larger sample to examine their rationalizations and attributions for having unprotected sex. Respondents high at risk for HIV used more often rationalizations and attributions to justify and excuse their risky behavior. At the same time, respondents high at risk were somewhat more fearful of contracting Acquired Immune Deficiency Syndrome (AIDS), and did not deny the riskiness of their behaviors compared with low-risk respondents. It is suggested that interventions should not focus on enhancing risk perceptions, but rather on challenging rationalizations and attributions that foster risky sexual behavior.

Effects of elevated carbon dioxide on soils in a Florida scrub oak ecosystem

The results of a 3-yr study on the effects of elevated CO2 on soil N and P, soil pCO2, and calculated CO2 efflux in a fire-regenerated Florida scrub oak ecosystem are summarized. We hypothesized that elevated CO2 would cause (i) increases in soil pCO2 and soil respiration and (ii) reduced levels of soil-available N and P. The effects of elevated CO2 on soil N availability differed according to the method used. Results of resin lysimeter collections and anion exchange membrane tests in the field showed reduced NO3- in soils in Years 1 and 3. On the other hand, re-analysis of homogenized, buried soil bags after 1 yr suggested a relative increase in N availability (lower C to N ratio) under elevated CO2. In the case of P, the buried bags and membranes suggested a negative effect of CO2 on P during the first year; this faded over time, however, as P availability declined overall, probably in response to P uptake. Elevated CO2 had no effect on soil pCO2 or calculated soil respiration at any time, further suggesting that plant rather than microbial uptake was the primary factor responsible for the observed changes in N and P availability with elevated CO2.

Smallest detectable difference of maximal mouth opening in patients with painfully restricted temporomandibular joint function

Changes in maximal mouth opening reflect the impact of temporomandibular disorders and the effect of a therapeutic intervention. No information about the amount of change in maximal mouth opening with regard to reasoned decision-making is available. The smallest detectable difference, as a measure of reliability assessment, provides this information and is expressed in the unit of the measurement instrument. Twenty-five consecutive patients (5 males, 20 females) with a painfully restricted temporomandibular joint participated in this study. Measurements of maximal mouth opening were performed by two well-trained observers on two separate measurement days, one week apart. The maximal mouth opening measurements were repeated three times. Inter-observer, intra-observer, and test-retest reliability varied between 0.90 and 0.96. Inconsistency in measurement results analyzed in terms of absolute error variance, i.e. the measurement facets plus all the interactions, represented 11% of total variance. The smallest detectable difference of maximal mouth opening varied from 9 to 6 mm. For being successful in painfully restricted temporomandibular joint patients, statistically as well as clinically, the clinician has to measure at least 9 mm of improvement in maximal mouth opening. To reduce the smallest detectable difference from 9 to 6 mm, repeated measurement is necessary.

Photosynthetic acclimation to elevated atmospheric CO(2) concentration in the Florida scrub-oak species Quercus geminata and Quercus myrtifolia growing in their native environment

Long-term effects of elevated CO(2) concentration (ambient plus 350 &mgr;mol mol(-1)) on leaf photosynthetic acclimation of two species of a scrub-oak community, Quercus myrtifolia Willd. and Quercus geminata Small, were studied. Plants of both species were grown in open-top chambers in their natural habitat at Kennedy Space Center, Florida, USA. Compared to ambient CO(2), elevated CO(2) stimulated photosynthetic rates by 73 and 51% for Q. geminata and Q. myrtifolia, respectively. Maximum rate of carboxylation (V(cmax)) was significantly reduced by elevated CO(2) in Q. myrtifolia (28%) but not in Q. geminata. Maximum rate of potential electron transport (J(max)) was not significantly reduced by elevated CO(2) in either species. In response to elevated CO(2), specific leaf area decreased in Q. myrtifolia (22%), but not in Q. geminata. Elevated CO(2) caused a significant accumulation of sugars (54%) and starch (264%) in Q. myrtifolia leaves, but not in Q. geminata leaves. Total Rubisco activity in Q. myrtifolia leaves was reduced 40% by elevated CO(2), whereas no significant reduction occurred in Q. geminata leaves. Although both species share a common habitat, they exhibited marked differences in photosynthetic acclimation to elevated CO(2) concentration.

Decreased leaf-miner abundance in elevated CO2: reduced leaf quality and increased parasitoid attack

Most studies on the effects of elevated CO2 have focused on the effects on plant growth and ecosystem processes. Fewer studies have examined the effects of elevated CO2 on herbivory, and of these, most have examined feeding rates in laboratory conditions. Our study takes advantage of an open-top CO2 fertilization study in a Florida scrub-oak community to examine the effects of elevated CO2 on herbivore densities, herbivore feeding rates, and levels of attack of herbivores by natural enemies. Higher atmospheric CO2 concentration reduced plant foliar nitrogen concentrations, decreased abundance of leaf-mining insect herbivores, increased per capita leaf consumption by leafminers, and increased leafminer mortality. As suggested by other authors, reduced foliar quality contributed to the increase in herbivore mortality, but only partly. The major factor increasing mortality was higher attack rate by parasitoids. Thus increasing CO2 concentrations may reduce the survivorship of insect herbivores directly, by reducing plant quality, but also indirectly, by changing herbivore feeding and eliciting greater top-down pressure from natural enemies.

Relation between relative growth rate, endogenous gibberellins, and the response to applied gibberellic acid for Plantago major

Relationships between relative growth rate (RGR), endogenous gibberellin (GA) concentration and the response to application of gibberellic acid (GA(3) ) were studied for two inbred lines of Plantago major L., which differed in RGR. A4, the fast-growing inbred line, had a higher free GA concentration than the slow-growing W9, as analyzed by enzyme immunoassay. GA(3) application increased total plant weight and RGR(3) particularly for the slow-growing line. Chlorophyll a content and photosynthetic activity per unit leaf area were decreased, while transpiration rate was unaffected by GA(3) application. The increase in RGR by GA(3) application was associated with an increased leaf weight ratio; specific leaf area and percentage of dry matter in the leaves were only temporarily affected. Root respiration rate per unit dry weight was unaffected. The correlation between low RGR, low GA concentration and high responsiveness to applied GA(3) supports the contention that gibberellins are involved in the regulation of RGR. However, the transient influence of GA(3) application on some growth components suggests the involvement of other regulatory factors in addition to GA.

Persistent sternum synchondroses on bone scintigraphy

This report describes the case history of two patients who showed a hyperactive midsternal area on bone scintigraphy due to a persistent sternal synchondrosis. Whereas this anatomical variant is diagnosed infrequently, midsternal hotspots can sometimes be related to arthrotic degeneration of these extra joint spaces. In the differential diagnosis of midsternal hotspots on bone scintigraphy, persistent sternum synchondroses should be considered.

Hypertelorism in neurofibromatosis

In eight out of thirty-four patients with neurofibromatosis hypertelorism was seen. This hypertelorism was diagnosed by measuring the intercanthal distance and calculating the interpupillary distance from it. The high incidence of hypertelorism in our group of patients (24%) makes its direct association with neurofibromatosis feasible. Moreover, hypertelorism was found exclusively in neurofibromatosis patients with brain involvement (8 out 11) and therefore seems to herald a severe expression of Morbus Recklinghausen. The bones of the face and the base of the skull are mesenchymal structures of neural crest origin and skull dysplasias - e.g. hypertelorism - fit well into the neurocristopathy concept of neurofibromatosis. Its ease of clinical recognition and its presence at birth makes the hypertelorism an early diagnostic criterium.

Neurofibromatosis and hypertelorism

Hypertelorism was observed in eight of 34 patients with neurofibromatosis. This diagnosis was made by measuring the intercanthal distance and calculating the interpupillary distance from it. The bones of the base of the skull and of the face are mesenchymal structures of neural crest origin. Skull dysplasias, in which hypertelorism can be included, fit well into the neurocristopathy concept of neurofibromatosis. Hypertelorism seems to herald a severe expression of neurofibromatosis, eg, with brain involvement, and would therefore be an indication for doing a computed tomographic scan. The high prevalence of hypertelorism in our group of patients (24%) makes its direct association with neurofibromatosis highly feasible. Its ease of clinical recognition and its presence at birth would make it a valuable early diagnostic criterion.

Physical impairment, stress, and cardiovascular disorders

Physical impairments bring about social and psychological consequences leading to stress. Here Dutch epidemiological data were used to test whether the physically disabled have an increased risk of CD. Results indicated this was partly so. Possible confounding variables, however, severely limit a firm statement concerning the relationship between disabling impairments and cardiovascular disorders.

[Life styles of myocardial infarct patients and of control groups: various similarities and differences]

In a population sample of 'healthy' males (N = 136; age 39-41) the classifications on the Jenkins Activity Survey (JAS) for assessing the Type A/B coronary-prone behavior pattern, and on the Maastricht Questionnaire (MQ), measuring emotional drain and subsequent depression, were investigated in relation to retrospective reporting of life changes on a newly developed Middle Adulthood Life Changes Questionnaire (MALC). In ANOVA, Type A subjects (N = 70) did report significantly more life changes in their work environment and family situation over the last two years than their Type B counterparts (N = 66). For subjects reporting clearcut manifestations of vital exhaustion and depression (N = 32) the same statistical associations do hold. Also, these latter subjects did evaluate their life changes as significantly 'more distressing' or as 'requiring more adjustment'. A group of male myocardial infarction (MI) patients (N = 35; average age 52) was compared with this control group on the MQ and the MALC. The MI-group showed a significantly lower average MQ-score than the section of the control group with clearcut manifestations of emotional drain and depression. Mean 'adjustment' scores, however, were significantly higher in the MI-group. In the discussion, the requirements for a dynamic life-span developmental model for explaining the assumedly different life-courses of MI-cases and controls are enunciated.