Linear Viscoelasticity and Time—Alcohol Superposition of Chitosan/Hyaluronic Acid Complex Coacervates

Complex coacervation is an associative liquid−liquid phase separation phenomenon resulting from the complexation of oppositely charged macroions. While it is well-known that the phase behavior and rheological character of the resulting coacervates can vary as a function of the identity of the various species present (i.e., macroions, salt, and solution conditions), the effect of solvent quality has been rarely studied. Here, the effect of adding small amounts of either methanol or ethanol to complex coacervates of the natural polymers chitosan and hyaluronic acid is described. The effect of cosolvent addition on the phase behavior and linear viscoelasticity of the resulting coacervates is characterized. Lastly, we explore the potential for using not only time−salt superposition but also time−alcohol and time−salt−alcohol superposition to provide insight into coacervate rheology

Understanding The Electrospinability Of Complex Coacervates

Complex coacervation is an associative, liquid-liquid phase separation that is driven by the electrostatic and entropic interactions between oppositely-charged polymers in water. For many coacervating systems it is possible to transition from the liquid coacervate state to a solid material by removing salt. This ‘saloplasticity’ allows for the processing of materials via methods such as spin coating, extrusion, etc. using the coacervate phase as a liquid precursor. In particular, we have developed an approach that uses complex coacervation as an environmentally friendly method for fabricating ultra-stable electrospun fibers directly from aqueous solutions. We have used this method to electrospin complexes of various synthetic polymers as well as natural biopolymers. These efforts have required the simultaneous exploration of the phase behavior of coacervate formation, as well as the rheology of the liquid coacervates

Electrospinning complex coacervates

As polymer-based materials become ever more integrated into our daily lives, there is an increasing need to develop both materials that are safe for the consumer, and manufacturing strategies that have a minimal impact on the environment. However, the vast majority of polymers require either organic solvents for dissolution, or the use of potentially cytotoxic cross-linking agents to prevent material dissolution. Additionally, many of the chemistries and solution conditions necessary for processing can damage cargo molecules and create biocompatibility issues for subsequent use. Complex coacervation is an associative, liquid-liquid phase separation that has the potential to circumvent many of the challenges associated with processing traditional polymers and encapsulating actives. Complex coacervation is driven by the electrostatic and entropic interactions between oppositely-charged polymers in water. For many coacervating systems, the solid or liquid nature of the complex can be tuned via the concentration of salt present. Additionally, the strength of the electrostatic interactions within the complex are such that in the absence of salt, solid complexes are highly resistant to thermal melting and/or solvent dissolution. Furthermore, complex coacervation has a strong history of use for the encapsulation of a range of cargo. We have taken advantage of this salt-driven plasticity to enable fabrication of ultra-stable electrospun fibers directly from aqueous solutions. These efforts have required the simultaneous characterization of coacervation, as well as the effect of cargo molecules on the phase behavior and rheology of the resulting coacervates/precursor solutions. Furthermore, these materials show tremendous promise for the use of electrospun coacervate-based nanofiber meshes across a range of applications

Bacteria-Resistant, Transparent, Free-standing Films Prepared from Complex Coacervates

We report the fabrication, properties, and bacteria-resistance of polyelectrolyte complex (PEC) coatings and free-standing films. Poly(4-styrenesulfonic acid), poly(diallyldimethylammonium chloride), and salt were spin-coated into PEC films. After thermal annealing in a humid environment, highly transparent, mechanically strong, and chemically robust films were formed. Notably, we demonstrate that PEC coatings significantly reduce the attachment of Escherichia coli K12 without killing the microorganisms. We suggest that forming bacteria-resistant surface coatings from commercially available polymers holds the potential for use across a wide range of applications, including high-touch surfaces in medical settings

Extra-articular arthroscopic release of lateral epicondylitis: a prospective study

Background: Operative management of lateral epicondylitis can be managed with percutaneous, arthroscopic, or open surgical release. Extraarticular arthroscopic release is a new technique, and no study has compared its outcomes and risk profile. Methods: A 26-patient cohort was reviewed before and after extraarticular arthroscopic release, which was performed by the senior author. The Mayo Elbow Performance Scores were used as a functional outcome score and obtained via a phone interview. Results were analyzed using a paired t-test with a statistical significance set at P \u3c .05. Results: Of the 26 patients, 10 were being treated under workers compensation. Preoperative Mayo Elbow Performance Score was 47.5, and the postoperative score was 90.2 with a significant difference of 42.7 (P value 1⁄4 .05). The workers compensation group scored 13.3 points lower postoperatively than the remainder of patients, which was shown to also be significant with a P value of .002. Discussion and Conclusion: The advantage of extraarticular arthroscopic release was better visualiza- tion of affected structures, which improved accuracy of debridement, and a small capsulotomy, which decreased the risk of a transient radial nerve palsy. Overall, extraarticular arthroscopic results were found to be good and comparable to the results of other operative techniques with the added advantage of a lower risk profile

Longitudinal associations between specific types of emotional reactivity and psychological, physical health, and school adjustment

Using a multimethod, multiinformant longitudinal design, we examined associations between specific forms of positive and negative emotional reactivity at age 5, children’s effortful control (EC), emotion regulation, and social skills at age 7, and adolescent functioning across psychological, academic, and physical health domains at ages 15/16 (N = 383). We examined how distinct components of childhood emotional reactivity directly and indirectly predict domain-specific forms of adolescent adjustment, thereby identifying developmental pathways between specific types of emotional reactivity and adjustment above and beyond the propensity to express other forms of emotional reactivity. Age 5 high-intensity positivity was associated with lower age 7 EC and more adolescent risk-taking; age 5 low-intensity positivity was associated with better age 7 EC and adolescent cardiovascular health, providing evidence for the heterogeneity of positive emotional reactivity. Indirect effects indicated that children’s age 7 social skills partially explain several associations between age 5 fear and anger reactivity and adolescent adjustment. Moreover, age 5 anger reactivity, low-, and high-intensity positivity were associated with adolescent adjustment via age 7 EC. The findings from this interdisciplinary, long-term longitudinal study have significant implications for prevention and intervention work aiming to understand the role of emotional reactivity in the etiology of adjustment and psychopathology

Graphene-Based Microfluidics for Serial Crystallography

Microfluidic strategies to enable the growth and subsequent serial crystallographic analysis of micro-crystals have the potential to facilitate both structural characterization and dynamic structural studies of protein targets that have been resistant to single-crystal strategies. However, adapting microfluidic crystallization platforms for micro-crystallography requires a dramatic decrease in the overall device thickness. We report a robust strategy for the straightforward incorporation of single-layer graphene into ultra-thin microfluidic devices. This architecture allows for a total material thickness of only ∼1 μm, facilitating on-chip X-ray diffraction analysis while creating a sample environment that is stable against significant water loss over several weeks. We demonstrate excellent signal-to-noise in our X-ray diffraction measurements using a 1.5 μs polychromatic X-ray exposure, and validate our approach via on-chip structure determination using hen egg white lysozyme (HEWL) as a model system. Although this work is focused on the use of graphene for protein crystallography, we anticipate that this technology should find utility in a wide range of both X-ray and other lab on a chip applications

Childhood self-regulation as a mechanism through which early overcontrolling parenting is associated with adjustment in preadolescence

We examined longitudinal associations across an 8-year time span between overcontrolling parenting during toddlerhood, self-regulation during early childhood, and social, emotional, and academic adjustment in preadolescence (N = 422). Overcontrolling parenting, emotion regulation (ER), and inhibitory control (IC) were observed in the laboratory; preadolescent adjustment was teacher-reported and child self-reported. Results from path analysis indicated that overcontrolling parenting at age 2 was associated negatively with ER and IC at age 5, which, in turn, were associated with more child-reported emotional and school problems, fewer teacher-reported social skills, and less teacher-reported academic productivity at age 10. These effects held even when controlling for prior levels of adjustment at age 5, suggesting that ER and IC in early childhood may be associated with increases and decreases in social, emotional, and academic functioning from childhood to preadolescence. Finally, indirect effects from overcontrolling parenting at age 2 to preadolescent outcomes at age 10 were significant, both through IC and ER at age 5. These results support the notion that parenting during toddlerhood is associated with child adjustment into adolescence through its relation with early developing self-regulatory skills

Three red suns in the sky: A transiting, terrestrial planet in a triple M-dwarf system at 6.9 pc

We present the discovery from Transiting Exoplanet Survey Satellite (TESS) data of LTT 1445Ab. At a distance of 6.9 pc, it is the second nearest transiting exoplanet system found to date, and the closest one known for which the primary is an M dwarf. The host stellar system consists of three mid-to-late M dwarfs in a hierarchical configuration, which are blended in one TESS pixel. We use MEarth data and results from the Science Processing Operations Center data validation report to determine that the planet transits the primary star in the system. The planet has a radius of ${1.38}_{-0.12}^{+0.13}$ ${R}_{\oplus }$, an orbital period of ${5.35882}_{-0.00031}^{+0.00030}$ days, and an equilibrium temperature of ${433}_{-27}^{+28}$ K. With radial velocities from the High Accuracy Radial Velocity Planet Searcher, we place a 3σ upper mass limit of 8.4 ${M}_{\oplus }$ on the planet. LTT 1445Ab provides one of the best opportunities to date for the spectroscopic study of the atmosphere of a terrestrial world. We also present a detailed characterization of the host stellar system. We use high-resolution spectroscopy and imaging to rule out the presence of any other close stellar or brown dwarf companions. Nineteen years of photometric monitoring of A and BC indicate a moderate amount of variability, in agreement with that observed in the TESS light-curve data. We derive a preliminary astrometric orbit for the BC pair that reveals an edge-on and eccentric configuration. The presence of a transiting planet in this system hints that the entire system may be co-planar, implying that the system may have formed from the early fragmentation of an individual protostellar core.Accepted manuscrip