Enzymatic Surface Erosion of High Tensile Strength Polycarbonates Based on Natural Phenols

Surface erosion has been recognized as a valuable design tool for resorbable biomaterials within the context of drug delivery devices, surface coatings, and when precise control of strength retention is critical. Here we report on high tensile strength, aromatic−aliphatic polycarbonates based on natural phenols, tyrosol (Ty) and homovanillyl alcohol (Hva), that exhibit enzymatic surface erosion by lipase. The Young’s moduli of the polymers for dry and fully hydrated samples are 1.0 to 1.2 GPa and 0.8 to 1.2 GPa, respectively. Typical characteristics of enzymatic surface erosion were confirmed for poly(tyrosol carbonate) films with concomitant mass-loss and thickness-loss at linear rates of 0.14 ± 0.01 mg cm−2 d−1 and 3.0 ± 0.8 μm d−1, respectively. The molecular weight and the mechanical properties of the residual films remained constant. Changing the ratio of Ty and Hva provided control over the glass transition temperature (Tg) and the enzymatic surface erosion: increasing the Hva content in the polymers resulted in higher Tg and lower enzymatic erosion rate. Polymers with more than 50 mol % Hva were stable at 37 °C in enzyme solution. Analysis on thin films using quartz crystal microbalance with dissipation (QCM-D) demonstrated that the onset temperature of the enzymatic erosion was approximately 20 °C lower than the wet Tg for all tested polymers. This new finding demonstrates that relatively high tensile strength polycarbonates can undergo enzymatic surface erosion. Moreover, it also sheds light on the connection between Tg and enzymatic degradation and explains why few of the high strength polymers follow an enzyme-meditated degradation pathway

Organizational metrics of interchromatin speckle factor domains: integrative classifier for stem cell adhesion & lineage signaling.

Stem cell fates on biomaterials are influenced by the complex confluence of microenvironmental cues emanating from soluble growth factors, cell-to-cell contacts, and biomaterial properties. Cell-microenvironment interactions influence the cell fate by initiating a series of outside-in signaling events that traverse from the focal adhesions to the nucleus via the cytoskeleton and modulate the sub-nuclear protein organization and gene expression. Here, we report a novel imaging-based framework that highlights the spatial organization of sub-nuclear proteins, specifically the splicing factor SC-35 in the nucleoplasm, as an integrative marker to distinguish between minute differences of stem cell lineage pathways in response to stimulatory soluble factors, surface topologies, and microscale topographies. This framework involves the high resolution image acquisition of SC-35 domains and imaging-based feature extraction to obtain quantitative nuclear metrics in tandem with machine learning approaches to generate a predictive cell state classification model. The acquired SC-35 metrics led to \u3e 90% correct classification of emergent human mesenchymal stem cell (hMSC) phenotypes in populations of hMSCs exposed for merely 3 days to basal, adipogenic, or osteogenic soluble cues, as well as varying levels of dexamethasone-induced alkaline phosphatase (ALP) expression. Early osteogenic cellular responses across a series of surface patterns, fibrous scaffolds, and micropillars were also detected and classified using this imaging-based methodology. Complex cell states resulting from inhibition of RhoGTPase, β-catenin, and FAK could be classified with \u3e 90% sensitivity on the basis of differences in the SC-35 organizational metrics. This indicates that SC-35 organization is sensitively impacted by adhesion-related signaling molecules that regulate osteogenic differentiation. Our results show that diverse microenvironment cues affect different attributes of the SC-35 organizational metrics and lead to distinct emergent organizational patterns. Taken together, these studies demonstrate that the early organization of SC-35 domains could serve as a “fingerprint” of the intracellular mechanotransductive signaling that governs growth factor- and topography-responsive stem cell states

Andean Condor (Vultur gryphus) in Ecuador: Geographic Distribution, Population Size and Extinction Risk.

The Andean Condor (Vultur gryphus) in Ecuador is classified as Critically Endangered. Before 2015, standardized and systematic estimates of geographic distribution, population size and structure were not available for this species, hampering the assessment of its current status and hindering the design and implementation of effective conservation actions. In this study, we performed the first quantitative assessment of geographic distribution, population size and population viability of Andean Condor in Ecuador. We used a methodological approach that included an ecological niche model to study geographic distribution, a simultaneous survey of 70 roosting sites to estimate population size and a population viability analysis (PVA) for the next 100 years. Geographic distribution in the form of extent of occurrence was 49 725 km2. During a two-day census, 93 Andean Condors were recorded and a population of 94 to 102 individuals was estimated. In this population, adult-to-immature ratio was 1:0.5. In the modeled PVA scenarios, the probability of extinction, mean time to extinction and minimum population size varied from zero to 100%, 63 years and 193 individuals, respectively. Habitat loss is the greatest threat to the conservation of Andean Condor populations in Ecuador. Population size reduction in scenarios that included habitat loss began within the first 15 years of this threat. Population reinforcement had no effects on the recovery of Andean Condor populations given the current status of the species in Ecuador. The population size estimate presented in this study is the lower than those reported previously in other countries where the species occur. The inferences derived from the population viability analysis have implications for Condor management in Ecuador. This study highlights the need to redirect efforts from captive breeding and population reinforcement to habitat conservation

Acknowledging Andean Condor predation on livestock, a first step in addressing the human-condor conflict: A commentary to Estrada Pacheco et al. 2020

In this comment, we emphasize the need to acknowledge that Andean Condors occasionally depart from their scavenging habits to injure or kill young livestock as an important first step to accepting the existence of a human-condor conflict. Estrada Pacheco et al. (2020) briefly admit a localized “strong conflict with the condor” due to perceived predation of cattle, however, throughout the bulk of the article, they treat the condor as a nonconflictive species accidentally killed in conflicts involving carnivorous predators. To stop Andean Condor mass poisonings in Argentina, the authors recommended two measures: (1) instating a National Law of Traceability and prescription of pesticides, and (2) engaging all stakeholders to resolve the human-carnivore (i.e., wild mammals) conflict. However, we are deeply concerned that denial of the underlying cause of the specific humancondor conflict leads to criminalizing illegal persecution and to ignoring calls for interdisciplinary research and management to tackle the conflict at its roots.Fil: Zuluaga Castañeda, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina. The Peregrine Fund; Estados UnidosFil: Salom, Amira. The Peregrine Fund; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Vargas, Félix Hernán. The Peregrine Fund; Estados UnidosFil: Coulson, Jeniffer O.. University of Tulane; Estados UnidosFil: Kohn, Sebastián. Fundación Cóndor Andino; EcuadorFil: Grande, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina. Universidad Nacional de La Pampa; Argentin

Geographic distribution of Andean Condor (<i>Vultur gryphus</i>) in Ecuador.

<p>Blue dots are roosting sites surveyed during September 29–30, 2015. Red polygons represent the National System of Protected Areas. Green areas represent extent of occurrence (left) and area of occupancy (right).</p

Andean Condor (<i>Vultur gryphus</i>) in Ecuador: Geographic Distribution, Population Size and Extinction Risk

<div><p>The Andean Condor (<i>Vultur gryphus</i>) in Ecuador is classified as Critically Endangered. Before 2015, standardized and systematic estimates of geographic distribution, population size and structure were not available for this species, hampering the assessment of its current status and hindering the design and implementation of effective conservation actions. In this study, we performed the first quantitative assessment of geographic distribution, population size and population viability of Andean Condor in Ecuador. We used a methodological approach that included an ecological niche model to study geographic distribution, a simultaneous survey of 70 roosting sites to estimate population size and a population viability analysis (PVA) for the next 100 years. Geographic distribution in the form of extent of occurrence was 49 725 km². During a two-day census, 93 Andean Condors were recorded and a population of 94 to 102 individuals was estimated. In this population, adult-to-immature ratio was 1:0.5. In the modeled PVA scenarios, the probability of extinction, mean time to extinction and minimum population size varied from zero to 100%, 63 years and 193 individuals, respectively. Habitat loss is the greatest threat to the conservation of Andean Condor populations in Ecuador. Population size reduction in scenarios that included habitat loss began within the first 15 years of this threat. Population reinforcement had no effects on the recovery of Andean Condor populations given the current status of the species in Ecuador. The population size estimate presented in this study is the lower than those reported previously in other countries where the species occur. The inferences derived from the population viability analysis have implications for Condor management in Ecuador. This study highlights the need to redirect efforts from captive breeding and population reinforcement to habitat conservation.</p></div

Environmental predictors used to model geographic distribution of Andean Condor (<i>Vultur gryphus</i>) in Ecuador.

<p>Environmental predictors used to model geographic distribution of Andean Condor (<i>Vultur gryphus</i>) in Ecuador.</p

Comparison of population size trends of Andean Condor (<i>Vultur gryphus</i>) in Ecuador among scenarios with different threats and management conditions.

<p>Trends modeled in VORTEX V10. Population size in vertical axis. Years in horizontal axis.</p

Demographic parameters used in the population viability analysis of Andean Condor (<i>Vultur gryphus</i>) in Ecuador.

<p>Demographic parameters used in the population viability analysis of Andean Condor (<i>Vultur gryphus</i>) in Ecuador.</p