Tricomponent composites with cellulose nanocrystals and chitin nanofibers - Exploring potential synergy through component interactions

Bio-based materials are being investigated increasingly as alternatives for synthetic materials in a variety of application areas, including composite materials. Among the options for bio-based materials, cellulose and chitin are abundant and increasingly available in different forms, including nanofibers. Due to their anticipated mechanical properties and anisotropic structure, nanofibers of cellulose and chitin lend themselves naturally for use as reinforcing fillers in polymer matrix composites, and the use of each in composites has been studied. However, composites containing both nanofillers has been explored to a lesser extent, and this composite design may provide benefits beyond those seen when the nanofibers are used separately. Therefore, the objective of this work is to examine how nanoscale forms of cellulose and chitin may be used separately and together in composite constructs. Specifically, we are preparing and characterizing composites composed of cellulose nanocrystals (CNCs) and/or chitin nanofibers (ChNFs) in a poly(vinyl alcohol) (PVA) matrix to understand more fully how component interactions affect the structure-property relationships in these materials and how these interactions may be used to produce synergistic improvements. For the specific CNCs and ChNFs used in this work, the nanofillers have opposite surface charge, with CNCs having a negative surface charge and ChNFs having a positive surface charge. Additionally, the components have an ability to interact through hydrogen bonding. These different types of interactions are anticipated to play a role in the structural development in the composites through the processing steps. To probe the effect of these interactions further, we have studied consolidated films as well as hydrogels. The results of these studies indicate that composites containing certain CNC/ChNF ratios possess better mechanical properties than composites containing only one type of nanofiber. Additionally, composites containing CNC/ChNF ratios where surface charges are more evenly balanced experience increased aggregation, presumably due to charge-driven association between the fillers. Mechanical property trends in consolidated films and hydrogels were qualitatively similar, suggesting a general behavior resulting from the component interactions. References 1. C.W. Irvin, C.C. Satam, J.C. Meredith, and M.L. Shofner, “Mechanical reinforcement and thermal properties of PVA tricomponent nanocomposites with chitin nanofibers and cellulose nanocrystals”, Composites Part A: Applied Science and Manufacturing, 116, 147-157 (2019)

Seeking homeostasis: Temporal trends in respiration, oxidation, and calcium in SOD1 G93A Amyotrophic Lateral Sclerosis mice

Impairments in mitochondria, oxidative regulation, and calcium homeostasis have been well documented in numerous amyotrophic lateral sclerosis (ALS) experimental models, especially in the superoxide dismutase 1 glycine 93 to alanine (SOD1 G93A) transgenic mouse. However, the timing of these deficiencies has been debatable. In a systematic review of 45 articles, we examine experimental measurements of cellular respiration, mitochondrial mechanisms, oxidative markers, and calcium regulation. We evaluate the quantitative magnitude and statistical temporal trend of these aggregated assessments in high transgene copy SOD1 G93A mice compared to wild type mice. Analysis of overall trends reveals cellular respiration, intracellular ATP, and corresponding mitochondrial elements (Cox, cytochrome c, complex I, enzyme activity) are depressed for the entire lifespan of the SOD1 G93A mouse. Oxidant markers (H2O2, 8OH2’dG, MDA) are initially similar to wild type but are double that of wild type by the time of symptom onset despite early post-natal elevation of protective heat shock proteins. All aspects of calcium regulation show early disturbances, although a notable and likely compensatory convergence to near wild type levels appears to occur between 40-80 days (pre-onset), followed by a post-onset elevation in intracellular calcium. The identified temporal trends and compensatory fluctuations provide evidence that the cause of ALS may lay within failed homeostatic regulation, itself, rather than any one particular perturbing event or cellular mechanism. We discuss the vulnerabilities of motoneurons to regulatory instability and possible hypotheses regarding failed regulation and its potential treatment in ALS

State of the field: An informatics-based systematic review of the SOD1-G93A amyotrophic lateral sclerosis transgenic mouse model

<p>Numerous sub-cellular through system-level disturbances have been identified in over 1300 articles examining the superoxide dismutase-1 guanine 93 to alanine (SOD1-G93A) transgenic mouse amyotrophic lateral sclerosis (ALS) pathophysiology. Manual assessment of such a broad literature base is daunting. We performed a comprehensive informatics-based systematic review or ‘field analysis’ to agnostically compute and map the current state of the field. Text mining of recaptured articles was used to quantify published data topic breadth and frequency. We constructed a nine-category pathophysiological function-based ontology to systematically organize and quantify the field's primary data. Results demonstrated that the distribution of primary research belonging to each category is: systemic measures an motor function, 59%; inflammation, 46%; cellular energetics, 37%; proteomics, 31%; neural excitability, 22%; apoptosis, 20%; oxidative stress, 18%; aberrant cellular chemistry, 14%; axonal transport, 10%. We constructed a SOD1-G93A field map that visually illustrates and categorizes the 85% most frequently assessed sub-topics. Finally, we present the literature-cited significance of frequently published terms and uncover thinly investigated areas. In conclusion, most articles individually examine at least two categories, which is indicative of the numerous underlying pathophysiological interrelationships. An essential future path is examination of cross-category pathophysiological interrelationships and their co-correspondence to homeostatic regulation and disease progression.</p

Spray-Coated Multilayer Cellulose NanocrystalChitin Nanofiber Films for Barrier Applications

Chitin is an abundant biopolymer whose natural production is second only to cellulose. Similar to cellulose nanocrystals (CNCs) or nanofibers (CNFs), chitin nanofibers (ChNFs) can be isolated and used as sustainable O₂ barrier materials for food, electronics, and pharmaceutical packaging. These bioavailable nanomaterials are readily dispersed in water enabling spray-coated films to be deposited at high rates onto uneven or delicate surfaces. In the present study, we demonstrate the successful layer-by-layer spray coating of cationic ChNF and anionic CNC suspensions onto poly­(lactic acid) (PLA) films. ChNF/CNC multilayers were found to lead to a reduction in the O₂ permeability of the final composite film by as much as 73% with the largest effects seen in composites with three alternating layers (ChNF-CNC-ChNF). Multilayer ChNF/CNC coatings were found to have lower O₂ permeability and lower haze than those coated with ChNF or CNCs alone (72% and 86% lower haze, respectively), pointing to a synergistic effect. The composites had a water vapor transmission rate similar to the PLA substrate