Learning from Classic: DNA-Based Conditional Equilibrium Constant To Regulate Affinity "On-the-Fly" for Bioassays.

Artificial programming of affinity is beneficial to optimize responsiveness in biomolecules for various applications. In one classical theory, one comprehensive parameter, conditional equilibrium constant (K'EDTA), can accurately and quantitatively define the affinity of ethylene diamine tetraacetic acid (EDTA) for metal ions. Learning from the classic, we have proposed a novel DNA-based conditional equilibrium constant (K'DNA) to regulate DNA probes' affinity and response "on-the-fly", long after the probe design and synthesis. Artificial regulation of affinity over several magnitudes has been simply realized via short oligonucleotides with different lengths, concentrations, and combinations. The thermodynamic response can be quantitatively simulated by one DNA-based conditional equilibrium constant (K'DNA), acting as an analogue to the classical EDTA system. The proof of concept of affinity programming also allows improved discrimination of single-nucleotide variants as well as assaying ribonuclease and doxycycline in a homogeneous solution. Therefore, the theory of DNA-based conditional equilibrium constant (K'DNA) will enable to engineer versatile DNA switches with programmable affinity in assays and bionanotechnology.

Photocatalytic Aptamer Chemiluminescent System for a Homogeneous, Reliable, Label-Free, Generic Assay of Small Molecules.

Chemiluminescence is a powerful analytical technique with many advantages, while aptamers are well-known as good molecular recognition units. However, many aptamer-based chemiluminescence assays employed interface sensing, which often needed several immobilization, separation, and washing steps. To minimize the risks of contamination and false-positive, we for the first time proposed a photocatalytic aptamer chemiluminescent system for a homogeneous, label-free, generic assay of small molecules. After binding to a DNA aptamer, thioflavin T has a unique photocatalytic oxidase activity to activate the system's luminol chemiluminescence. Then, the specific binding between the aptamer and target molecules will compete with the above process. Therefore, we can realize the efficient assay of different analytes including estradiol and adenosine. Such a homogeneous chemiluminescent system allowed a direct assay of small molecules with limits of detection in a nM level. Several control tests were carried out to avoid possible false-positive results, which were originated from the interactions between analytes and sensing interfaces previously. This homogeneous chemiluminescent system provides a useful strategy to reliably assay various analytes in the pharmacy or biology field.

Dynamics of polylactic acid under ultrafine nanoconfinement: The collective interface effect and the spatial gradient.

Polymers under nanoconfinement can exhibit large alterations in dynamics from their bulk values due to an interface effect. However, understanding the interface effect remains a challenge, especially in the ultrafine nanoconfinement region. In this work, we prepare new geometries with ultrafine nanoconfinement ∼10nm through controlled distributions of the crystalline phases and the amorphous phases of a model semi-crystalline polymer, i.e., the polylactic acid. The broadband dielectric spectroscopy measurements show that ultrafine nanoconfinement leads to a large elevation in the glass transition temperature and a strong increment in the polymer fragility index. Moreover, new relaxation time profile analyses demonstrate a spatial gradient that can be well described by either a single-exponential decay or a double-exponential decay functional form near the middle of the film with a collective interface effect. However, the dynamics at the 1-2 nm vicinity of the interface exhibit a power-law decay that is different from the single-exponential decay or double-exponential decay functional forms as predicted by theories. Thus, these results call for further investigations of the interface effect on polymer dynamics, especially for interfaces with perturbed chain packing.

Simulation-Guided Rational Design of DNA Probe for Accurate Discrimination of Single-Nucleotide Variants Based on "Hill-Type" Cooperativity.

The accurate discrimination of single-nucleotide variants is of great interest for disease diagnosis and clinical treatments. In this work, a unique DNA probe with "Hill-type" cooperativity was first developed based on toehold-mediated strand displacement processes. Under simulation, this probe owns great thermodynamics advantage for specificity due to two mismatch bubbles formed in the presence of single-nucleotide variants. Besides, the strategies of ΔG' = 0 and more competitive strands are also beneficial to discriminate single-nucleotide variants. The feasibility of this probe was successfully demonstrated in consistent with simulation results. Due to "Hill-type" cooperativity, the probe allows a steeper dynamic range compared with previous probes. With simulation-guided rational design, the resulting probe can accurately discriminate single-nucleotide variants including nucleotide insertions, mutation, and deletions, which are arbitrarily distributed in target sequence. Two specificity parameters were calculated to quantitatively evaluate its good discrimination ability. Hence, "Hill-type" cooperativity can serve as a novel strategy in DNA probe's design for accurate discrimination of single-nucleotide variants.

Versatile DNA Balances via Adjacent Base Stacking for Homogeneous Assay of Energy Parameters, Small Molecules, And Ribonuclease.

Homogeneous assays often obviate any separation and washing steps, thus minimizing the risks of contamination and false positive. DNA toehold exchange is a homogeneous, reversible process whose thermodynamic properties can be finely tuned for various assay applications. However, the developed probes often rely on direct interactions of analytes with DNA strands involved in toehold exchange, limiting the versatility of probe design. Here, the coaxial adjacent stacking between one auxiliary strand and another invading strand offers a favorable ΔG to shift one DNA balance, while the auxiliary strand is independent of the DNA balance itself. Therefore, such a DNA balance allowed fine tuning of the equilibrium via adjustment of the auxiliary strand alone. The energy contribution of base stacking can be quantified in a homogeneous solution based on the difference in the equilibrium constant. Besides, the proof of concept for DNA balance allows effective assay of a small molecule or ribonuclease in a homogeneous solution. This novel DNA balance via adjacent base stacking provides an interesting alternative to homogeneously assay various analytes.

Spontaneous outflow efficiency of confined liquid in hydrophobic nanopores.

The suspension of nanoporous particles in a nonwetting liquid provides a unique solution to the crux of superfluid, sensing, and energy conversion, yet is challenged by the incomplete outflow of intruded liquid out of nanopores for the system reusability. We report that a continuous and spontaneous liquid outflow from hydrophobic nanopores with high and stable efficiency can be achieved by regulating the confinement of solid-liquid interactions with functionalized nanopores or/and liquids. Full-scale molecular-dynamics simulations reveal that the grafted silyl chains on nanopore wall surfaces will promote the hydrophobic confinement of liquid molecules and facilitate the molecular outflow; by contrast, the introduction of ions in the liquid weakens the hydrophobic confinement and congests the molecular outflow. Both one-step and multistep well-designed quasistatic compression experiments on a series of nanopores/nonwetting liquid material systems have been performed, and the results confirm the outflow mechanism in remarkable agreement with simulations. This study offers a fundamental understanding of the outflow of confined liquid from hydrophobic nanopores, potentially useful for devising emerging nanoporous-liquid functional systems with reliable and robust reusability.

Electronic health literacy and health-related outcomes among older adults: A systematic review.

This review aims to identify, appraise, and synthesize research evidence of the association between electronic health (eHealth) literacy and health outcomes in older adults. English-written articles that presented the relationships between eHealth literacy and health-related outcomes in older adults were identified by searching five scientific databases (Web of Science, PubMed, Cochrane Library, APA PsycInfo, and EMBASE) hand-searching reference lists. Searches yielded 2993 studies after duplicates were removed, of which 24 publications were included in the final review. eHealth literacy was relatively low in older adults, and the eHealth Literacy Scale, developed by Norman and Skinner in 2006, was the most frequently used instrument in the included studies (21/24, 87.5%). The health-related outcomes associated with eHealth literacy were grouped into four categories: physical, behavioral, psychosocial, and cognitive. For behavioral (e.g., health-promoting behaviors, self-care, and medication adherence) and cognitive (e.g., health knowledge and health decision making) outcomes, the evidence was mostly consistent that eHealth literacy was positively associated with better outcomes. For physical (e.g., health-related quality of life) and psychosocial outcomes (e.g., anxiety and self-efficacy), the associations were less consistent, with some studies showing significant associations while others showed no associations. Most included studies were assessed as moderate quality. Overall, higher eHealth literacy is associated with more positive health behaviors and better health knowledge and attitude in older adults, however, the associations with some physical and psychosocial outcomes are less consistent. Clarifying the pathways of the relationships between eHealth literacy and some health-related outcomes is needed for further exploring their underlying mechanisms.

Effect of Extra Gas Amount on Liquid Outflow from Hydrophobic Nanochannels: Enhanced Liquid-Gas Interaction and Bubble Nucleation.

Understanding liquid motion in nanoenvironment is of fundamental importance in nanofluidics-based systems. While the liquid outflow from hydrophobic nanochannels can significantly affect system performance, its underlying mechanism remains unclear so far. Here, we present an experimental study of the gas-phase effect on liquid outflow behavior from hydrophobic nanochannels in a liquid nanofoam (LN) system. Four LN samples, consisting of same liquid-solid composition but different amounts of the gas phase, are characterized by cyclic quasi-static compression tests. A remarkable difference in the LN system reusability has been observed, indicating that the liquid outflow behavior is highly sensitive to the amount of the gas phase. As the gas amount increases, the degree of liquid outflow from hydrophobic nanochannels is considerably promoted. This promotive effect is because of the suppression of gas outflow and acceleration of bubble nucleation in the nanochannels. These fundamental findings open a new perspective on liquid outflow behavior and can facilitate the design of reusable nanofluidics-based energy absorbers.

Effect of Electrolytes on Gas Oversolubility and Liquid Outflow from Hydrophobic Nanochannels.

We have experimentally studied the effect of electrolytes on gas oversolubility and liquid outflow from hydrophobic nanochannels. By immersing nanoporous material with the same porous structure and surface properties into four different aqueous electrolyte solutions with the same surface tension, the excessive solid-liquid interfacial tension of the resulted liquid nanofoam (LN) systems has been set as a constant. Upon unloading, partial liquid outflow has been observed and quantified. As the four LN systems show different degrees of recoverability, it suggests that the degree of liquid outflow is highly sensitive to the ion species. In addition, different from bulk phase scenario, the anions have a more profound effect than cations on gas oversolubility. Lower bulk gas solubility and larger gas oversolubility factor lead to higher degree of liquid outflow and recoverability of the LN systems. This fundamental understanding on the mechanism of liquid outflow enables the development of nanofluidics-based system into reusable energy absorbers.

Enhanced Catalytic Activity of Aluminum Complexes for the Ring-Opening Polymerization of ε-Caprolactone.

A series of dinuclear aluminum (Al2Pyr2) complexes bridged by two pyrazole ligands were synthesized, and their catalytic activity toward ring-opening polymerization of ε-caprolactone (CL) was investigated. Different types of the Al-N-N-Al-N-N skeletal ring were found among these Al2Pyr2 complexes. The butterfly form, LThio2Al2Me4, exerted the highest catalytic activity for CL polymerization. κ2-CL coordination with both Al centers within the butterfly form LThio2Al2Me4 facilitates the initiation process. Generally speaking, the Al2Pyr2 complexes exhibited substantially higher catalytic activity for CL polymerization than literature examples such as ß-diketiminate- or traiaza-bearing aluminum complexes. In fact, the Al2Pyr2 complexes can even carry out CL polymerization at room temperature.

Adaptive liquid flow behavior in 3D nanopores.

Liquid flow speed in 2D nanochannel models has previously been characterized, whereas liquid flow behavior in 3D nanostructured materials remains unknown. To fill this gap, we have developed a novel liquid nanofoam (LN) system composed of nanoporous silica gel particles and a non-wettable liquid phase. We demonstrated that the dynamic behavior of the LN sample was strain rate insensitive by impacting it with a drop weight at various incident speeds. Using this experimental setup, we measured the effective liquid flow speed in 3D nanopores and showed that it was 5 orders of magnitude higher than that of quasi-static loading. Importantly, the liquid infiltration speed as well as the energy absorption efficiency of the LN was found to be adaptive to the incident speed and energy level. This provides a mechanistic explanation for the high energy absorption efficiency of LNs at high blast impact levels and strain rates, and demonstrates the importance of experimentally investigating the liquid flow behavior in 3D instead of the traditional 2D nanopores.

Synthesis of Sodium Complexes Supported with NNO-Tridentate Schiff Base Ligands and Their Applications in the Ring-Opening Polymerization of L-Lactide.

A series of sodium complexes bearing NNO-tridentate Schiff base ligands with an N-pendant arm were synthesized and used as catalysts for the ring-opening polymerization of L-lactide (L-LA). Electronic effects of ancillary ligands coordinated by sodium complexes substantially influence the catalysis, and ligands with electron-donating groups increase the catalytic activity of the sodium complexes for catalyzing L-LA polymerization. In particular, a sodium complex bearing a 4-methoxy group has the highest activity with conversion up to 95% within 30 s at 0 °C and a low polydispersity index of 1.13, whereas the 4-bromo group showed the poorest performance with regard to the catalytic rate of L-LA polymerization in the presence of benzyl alcohol (BnOH). (1)H NMR pulsed-gradient spin-echo diffusion experiments and single-crystal X-ray analyses showed that sodium complexes [L(H)Na(THF)]2 and [L(4-Cl)Na(THF)]2 were dinuclear species in both solution and the solid state. The kinetic results indicated a first-order dependence on each of [[L(4-Cl)Na]2], [l-LA], and [BnOH].

Improvement in Titanium Complexes Bearing Schiff Base Ligands in the Ring-Opening Polymerization of L-Lactide: A Dinuclear System with Hydrazine-Bridging Schiff Base Ligands.

A series of titanium (Ti) complexes bearing hydrazine-bridging Schiff base ligands were synthesized and investigated as catalysts for the ring-opening polymerization (ROP) of L-lactide (LA). Complexes with electron withdrawing or steric bulky groups reduced the catalytic activity. In addition, the steric bulky substituent on the imine groups reduced the space around the Ti atom and then reduced LA coordination with Ti atom, thereby reducing catalytic activity. All the dinuclear Ti complexes exhibited higher catalytic activity (approximately 10-60-fold) than mononuclear L(Cl-H)-TiOPr2 did. The strategy of bridging dinuclear Ti complexes with isopropoxide groups in the ROP of LA was successful, and adjusting the crowded heptacoordinated transition state by the bridging isopropoxide groups may be the key to our successful strategy.

The impact mitigation of a heterojunction nanotube-water system: behavior and mechanism.

A novel nanofluidic impact protection system is introduced in this paper, consisting of hydrophobic heterojunction carbon nanotubes (HCNTs) and water molecules. When the capillary resistance of the nanopores is overcome, water molecules can infiltrate into nanopores such as to convert external impact energy into excessive surface energy. A model of a single HCNT with water molecules in a reservoir is established and validated. The effects of several dominant parameters (e.g., nanopore size, impact velocity) are evaluated, and the potential mechanism is illustrated. The effect of the carbon nanotube structure on the nanofluidic behavior of the HCNT-water system is investigated. Results reveal that the segment of carbon nanotubes close to the water reservoir determines the energy absorption efficiency of the system.

Comparative Study of Aluminum Complexes Bearing N,O- and N,S-Schiff Base in Ring-Opening Polymerization of ε-Caprolactone and L-Lactide.

A series of Al complexes bearing Schiff base and thio-Schiff base ligands were synthesized, and their application for the ring-opening polymerization of ε-caprolactone (CL) and l-lactide (LA) was studied. It was found that steric effects of the ligands caused higher polymerization rate and most importantly the Al complexes with N,S-Schiff base showed significantly higher polymerization rate than Al complexes with N,O-Schiff base (5-12-fold for CL polymerization and 2-7-fold for LA polymerization). The reaction mechanism of CL polymerization was investigated by density functional theory (DFT). The calculations predicted a lower activation energy for a process involved with an Al complex bearing an N,S-Schiff base ligand (17.6 kcal/mol) than for that of an Al complex bearing an N,O-Schiff base ligand (19.0 kcal/mol), and this magnitude of activation energy reduction is comparable to the magnitude of rate enhancement observed in the experiment. The reduction of activation energy was attributed to the catalyst-substrate destabilization effect. Using a sulfur-containing ligand to decrease the activation energy in the ring-opening polymerization process may be a new strategy to design a new Al complex with high catalytic activity.

Light-activated oxidative capacity of isoquinoline alkaloids for universal, homogeneous, reliable, colorimetric assays with DNA aptamers.

Aptamers are good affinity receptors for bio-assays, while colorimetric method is suitable for point-of-care sensing via direct visualization. But previously aptamers often need complex re-engineering for colorimetric measurement at the cost of affinity and performance. Here isoquinoline alkaloids are found to own unique light-activated oxidative capacity, which can be specifically triggered by unmodified aptamers. This feature is universal for two alkaloids to efficiently oxidize four chromogenic substrates with obvious color changes. Based on a dye-displacement process, we have developed a novel light-activated aptamer system for the colorimetric assay of estradiol. It shows a good sensitivity with a detection limit of 326 nM, and this homogeneous assay is reliable to avoid artifacts in previous heterogeneous scheme. Besides, it is proven to be a universal design to assay other two targets. Significantly, they do not employ any aptamers re-engineering but only simply use their parental aptamers. Therefore, this light-activated oxidative capacity of isoquinoline alkaloid can serve as an ideal tool for colorimetric assay of various targets based on aptamer's specific recognition.

Effects of ion concentration on thermally-chargeable double-layer supercapacitors.

The concept of thermally-chargeable supercapacitor was discussed and validated experimentally. As two double-layer supercapacitor-type devices were placed at different temperatures and connected, due to the thermal dependence of surface charge structures, the electrode potentials became different, and thermal energy could be harvested and stored as electric energy. The important effect of ion concentration was investigated. The results were quite different from the prediction of conventional surface theory, which should be attributed to the unique behaviors of the ions confined in the nanoporous electrodes.

A Nanoconfined Water-Ion Coordination Network for Flexible Energy-Dissipation Devices.

Water-ion interaction in a nanoconfined environment that deeply constrains spatial freedoms of local atomistic motion with unconventional coupling mechanisms beyond that in a free, bulk state is essential to spark designs of a broad spectrum of nanofluidic devices with unique properties and functionalities. Here, it is reported that the interaction between ions and water molecules in a hydrophobic nanopore forms a coordination network with an interaction density that is nearly fourfold that of the bulk counterpart. Such strong interaction facilitates the connectivity of the water-ion network and is uncovered by corroborating the formation of ion clusters and the reduction of particle dynamics. A liquid-nanopore energy-dissipation system is designed and demonstrated in both molecular simulations and experiments that the formed coordination network controls the outflow of confined electrolytes along with a pressure reduction, capable of providing flexible protection for personnel and devices and instrumentations against external mechanical impact and attack.

[Advances in organoids of the digestive system].

Organoid is a newly developed cellular there-dimensional culture system in recent years. Organoids have a three-dimensional structure, which is similar to that of the real organs. Together with the characteristics of self-renewal and reproduction of tissue origin, organoids can better simulate the function of real organs. Organoids provide a new platform for the study of organogenesis, regeneration, disease pathogenesis, and drug screening. The digestive system is an essential part of the human body and performs important functions. To date, organoid models of various digestive organs have been successfully established. This review summarizes the latest research progress of organoids of taste buds, esophagi, stomachs, livers and intestines, and prospects future application of organoids.

Tris(1,2-dimeth-oxy-ethane-κO,O')iodidocalcium iodide.

In the title complex, [CaI(C(4)H(10)O(2))(3)]I, the Ca(II) atom is seven-coordinated by six O atoms from three 1,2-dimeth-oxy-ethane (DME) ligands and one iodide anion in a distorted penta-gonal-bipyramidal geometry. The I atom and one of the O atoms from a DME ligand lie in the axial positions while the other O atoms lie in the basal plane. The other iodide anion is outside the complex cation.