Multiphasic Coacervates Assembled by Hydrogen Bonding and Hydrophobic Interactions.

Coacervation has emerged as a prevalent mechanism to compartmentalize biomolecules in living cells. Synthetic coacervates help in understanding the assembly process and mimic the functions of biological coacervates as simplified artificial systems. Though the molecular mechanism and mesoscopic properties of coacervates formed from charged coacervates have been well investigated, the details of the assembly and stabilization of nonionic coacervates remain largely unknown. Here, we describe a library of coacervate-forming polyesteramides and show that the water-tertiary amide bridging hydrogen bonds and hydrophobic interactions stabilize these nonionic, single-component coacervates. Analogous to intracellular biological coacervates, these coacervates exhibit "liquid-like" features with low viscosity and low interfacial energy, and form coacervates with as few as five repeating units. By controlling the temperature and engineering the molar ratio between hydrophobic interaction sites and bridging hydrogen bonding sites, we demonstrate the tuneability of the viscosity and interfacial tension of polyesteramide-based coacervates. Taking advantage of the differences in the mesoscopic properties of these nonionic coacervates, we engineered multiphasic coacervates with core-shell architectures similar to those of intracellular biological coacervates, such as nucleoli and stress granule-p-body complexes. The multiphasic structures produced from these synthetic nonionic polyesteramide coacervates may serve as a valuable tool for investigating physicochemical principles deployed by living cells to spatiotemporally control cargo partitioning, biochemical reaction rates, and interorganellar signal transport.

Thread Size and Polymer Composition of 3D Printed and Electrospun Wound Dressings Affect Wound Healing Outcomes in an Excisional Wound Rat Model.

Thread size and polymer composition are critical properties to consider for achieving a positive healing outcome with a wound dressing. Three-dimensional (3D) printed scaffolds and electrospun mats both offer distinct advantages as replaceable wound dressings. This research aims to determine if the thread size and polymer compositions of the scaffolds affect skin wound healing outcomes, an aspect that has not been adequately explored. Using a modular polymer platform, four polyester direct-write 3D printed scaffolds and electrospun mats were fabricated into wound dressings. The dressings were applied to splinted, full thickness skin wounds in an excisional wound rat model and evaluated against control wounds to which no dressing was applied. Wound closure rates and reduction of the wound bed width were not affected by the thread size or polymer composition. However, epidermal thickness was larger in wounds treated with electrospun dressings and was slightly affected by the polymer composition. Two of the four tested polymer compositions lead to delayed reorganization of granulation tissues. Moreover, enhanced angiogenesis was seen in wounds treated with 3D printed dressings compared to those treated with electrospun dressings. The results from this study can be used to inform the choice of dressing architecture and polymer compositions to achieve positive wound healing outcomes.

Light-Activated Adhesion and Debonding of Underwater Pressure-Sensitive Adhesives.

Pressure-sensitive adhesives (PSAs) such as sticky notes and labels are a ubiquitous part of modern society. PSAs with a wide range of peel adhesion strength are designed by tailoring the bulk and surface properties of the adhesive. However, designing an adhesive with strong initial adhesion but showing an on-demand decrease in adhesion has been an enduring challenge in the design of PSAs. To address this challenge, we designed alkoxyphenacyl-based polyurethane (APPU) PSAs that show a photoactivated increase and decrease in peel strength. With increasing time of light exposure, the failure mode of our PSAs shifted from cohesive to adhesive failure, providing residue-free removal with up to 83% decrease in peel strength. The APPU-PSAs also adhere to substrates submerged underwater and show a similar photoinduced decrease in adhesion strength.

[NiIII(OMe)]-mediated reductive activation of CO2 affording a Ni(κ1-OCO) complex.

Carbon dioxide is expected to be employed as an inexpensive and potential feedstock of C1 sources for the mass production of valuable chemicals and fuel. Versatile chemical transformations of CO2, i.e. insertion of CO2 producing bicarbonate/acetate/formate, cleavage of CO2 yielding µ-CO/µ-oxo transition-metal complexes, and electrocatalytic reduction of CO2 affording CO/HCOOH/CH3OH/CH4/C2H4/oxalate were well documented. Herein, we report a novel pathway for the reductive activation of CO2 by the [NiIII(OMe)(P(C6H3-3-SiMe3-2-S)3)]- complex, yielding the [NiIII(κ1-OCO˙-)(P(C6H3-3-SiMe3-2-S)3)]- complex. The formation of this unusual NiIII(κ1-OCO˙-) complex was characterized by single-crystal X-ray diffraction, EPR, IR, SQUID, Ni/S K-edge X-ray absorption spectroscopy, and Ni valence-to-core X-ray emission spectroscopy. The inertness of the analogous complexes [NiIII(SPh)], [NiII(CO)], and [NiII(N2H4)] toward CO2, in contrast, demonstrates that the ionic [NiIII(OMe)] core attracts the binding of weak σ-donor CO2 and triggers the subsequent reduction of CO2 by the nucleophilic [OMe]- in the immediate vicinity. This metal-ligand cooperative activation of CO2 may open a novel pathway promoting the subsequent incorporation of CO2 in the buildup of functionalized products.

Association of umbilical cord plasma acid-labile subunit of the insulin-like growth factor ternary complex with anthropometry in term newborns.

BACKGROUND: Birth size can affect neonatal morbidity and mortality. The insulin-like growth factor (IGF) system is the most important endocrine factor influencing fetal growth. In the circulation, IGFs (mostly IGF-I) are bound to IGF-binding protein 3 (IGFBP-3) and an acid-labile subunit (ALS) to form a ternary complex. The ALS protects IGFs from decay and facilitates their endocrine activity. However, the function of ALS in fetal growth has not yet been fully determined. METHODS: Venous umbilical plasma samples were obtained from 98 term neonates and analyzed using enzyme-linked immunosorbent assays. The ALS, IGF-I, and IGFBP-3 umbilical cord plasma levels were analyzed for their association with anthropometric measurements of the neonates. RESULTS: The ALS, IGF-I, and IGFBP-3 cord plasma levels were positively correlated with birth weight (r = 0.42, p < 0.001; r = 0.43, p < 0.001; and r = 0.27, p < 0.01, respectively) and placental weight (r = 0.37, p < 0.001; r = 0.31, p < 0.01; and r = 0.30, p < 0.01, respectively). In addition, the ALS cord plasma levels were also positively correlated with head circumference (r = 0.29, p < 0.01). Multiple linear regression analyses showed that both ALS and IGF-I cord plasma levels were independent predictive variables for birth weight (p < 0.01 and p < 0.005, respectively). The ALS cord plasma levels were the only independent predictive variables, however, for head circumference and placental weight (p < 0.01 and p < 0.05, respectively). CONCLUSION: The ALS umbilical cord plasma levels are one important factor, in addition to IGF-I, in the IGF system for predicting birth anthropometry, at least for near-term gestation. Our results suggest that the influence of ALS on the IGF system may develop prior to birth and affect fetal growth.

Associations among perinatal factors and age of achievement of full oral feeding in very preterm infants.

BACKGROUND: Progress to full oral feeding from a tube or parenteral feeding is a complex process for very preterm infants born before 32 weeks of gestation. The influence of infant characteristics and medical complications on feeding progression has not been studied thoroughly. The aim of this study was to constitute a regression model to estimate the postmenstrual age (PMA) of full oral feeding and the length of transition time from the initiation to completion of oral feeding. METHODS: A chart review was conducted on very preterm infants born between 2005 and 2010 in one medical center in Taiwan. All enrolled infants were able to take all nutrition by mouth before discharge. RESULTS: A total of 117 infants fulfilling the criteria were included. The mean PMAs for the initiation and completion of oral feeding were 33.9 ± 1.7 and 35.1 ± 2.0 weeks, respectively. Infants required 7.5 ± 6.6 days from initiation to full oral feeding. The results of a stepwise regression revealed that the reciprocal of birth weight (beta coefficient = 3.81, p < 0.001), moderate-severe bronchopulmonary dysplasia (beta coefficient = 1.21, p < 0.001), necrotizing enterocolitis (beta coefficient = 0.84, p < 0.005), and patent ductus arteriosus (beta coefficient = 0.69, p < 0.01) were predictors for the PMA of full oral feeding. The regression model incorporating those factors explained 62.5% of the variation in the feeding outcome (p < 0.001). Gender, multiple gestations, mild bronchopulmonary dysplasia, intraventricular hemorrhage, and sepsis had no effect on the feeding outcome. None of the explored factors were significantly correlated with transition time. CONCLUSION: A regression model incorporating significant predictors to estimate the PMA of full oral feeding in very preterm infants was suggested. It could enhance communication between health professionals and parents about the feeding progress of infants born very prematurely.