Biomimetic Choline-Like Graphene Oxide Composites for Neurite Sprouting and Outgrowth

Neurodegenerative diseases or acute injuries of the nervous system always lead to neuron loss and neurite damage. Thus, the development of effective methods to repair these damaged neurons is necessary. The construction of biomimetic materials with specific physicochemical properties is a promising solution to induce neurite sprouting and guide the regenerating nerve. Herein, we present a simple method for constructing biomimetic graphene oxide (GO) composites by covalently bonding an acetylcholine-like unit (dimethylaminoethyl methacrylate, DMAEMA) or phosphorylcholine-like unit (2-methacryloyloxyethyl phosphorylcholine, MPC) onto GO surfaces to enhance neurite sprouting and outgrowth. The resulting GO composites were characterized by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, UV–vis spectrometry, scanning electron microscopy, and contact angle analyses. Primary rat hippocampal neurons were used to investigate nerve cell adhesion, spreading, and proliferation on these biomimetic GO composites. GO–DMAEMA and GO–MPC composites provide the desired biomimetic properties for superior biocompatibility without affecting cell viability. At 2 to 7 days after cell seeding was performed, the number of neurites and average neurite length on GO–DMAEMA and GO–MPC composites were significantly enhanced compared with the control GO. In addition, analysis of growth-associate protein-43 (GAP-43) by Western blot showed that GAP-43 expression was greatly improved in biomimetic GO composite groups compared to GO groups, which might promote neurite sprouting and outgrowth. All the results demonstrate the potential of DMAEMA- and MPC-modified GO composites as biomimetic materials for neural interfacing and provide basic information for future biomedical applications of graphene oxide

Metal Oxyhydroxide Catalysts Promoted CO₂ Absorption and Desorption in Amine-Based Carbon Capture: A Feasibility Study

The huge energy penalty of CO2 desorption is the greatest challenge impeding the commercial application of amine-based CO2 capture. To deal with this problem, a series of metal oxide and oxyhydroxide catalysts were synthesized in this study to kinetically facilitate the CO2 desorption from 5.0 M monoethanolamine (MEA). The effects of selected catalysts on CO2 absorption kinetics, CO2 absorption capacity, CO2 reaction enthalpy, and desorption duty reduction of 2.0 M MEA were investigated by a true heat flow reaction calorimeter to access the practical feasibility of the catalytic CO2 desorption. The kinetic study of catalytic CO2 desorption was also carried out. CO2 desorption chemistry, catalyst characterization, and structure–function relationships were investigated to reveal the underlying mechanisms. Results show that addition of the catalyst had slight effects on the CO2 absorption kinetics and CO2 reaction enthalpy of MEA. In contrast, the CO2 desorption efficiency greatly increased from 28% in reference MEA to 52% in ZrO(OH)2-aided MEA. Compared to the benchmark catalyst HZSM-5, ZrO(OH)2 exhibited a 13% improvement in CO2 desorption efficiency. More importantly, compared to the reference MEA, the CO2 desorption duties of ZrO(OH)2 and FeOOH-aided MEA significantly reduced by 45 and 47% respectively, which are better than those of most other reported catalysts. The large surface area, pore volume, pore diameter, and amount of surface hydroxyl groups of ZrO(OH)2 and FeOOH afforded the catalytic performance by promoting the adsorption of alkaline speciation (e.g., MEA and HCO3–) onto the particle surface

Metal Oxyhydroxide Catalysts Promoted CO₂ Absorption and Desorption in Amine-Based Carbon Capture: A Feasibility Study

The huge energy penalty of CO2 desorption is the greatest challenge impeding the commercial application of amine-based CO2 capture. To deal with this problem, a series of metal oxide and oxyhydroxide catalysts were synthesized in this study to kinetically facilitate the CO2 desorption from 5.0 M monoethanolamine (MEA). The effects of selected catalysts on CO2 absorption kinetics, CO2 absorption capacity, CO2 reaction enthalpy, and desorption duty reduction of 2.0 M MEA were investigated by a true heat flow reaction calorimeter to access the practical feasibility of the catalytic CO2 desorption. The kinetic study of catalytic CO2 desorption was also carried out. CO2 desorption chemistry, catalyst characterization, and structure–function relationships were investigated to reveal the underlying mechanisms. Results show that addition of the catalyst had slight effects on the CO2 absorption kinetics and CO2 reaction enthalpy of MEA. In contrast, the CO2 desorption efficiency greatly increased from 28% in reference MEA to 52% in ZrO(OH)2-aided MEA. Compared to the benchmark catalyst HZSM-5, ZrO(OH)2 exhibited a 13% improvement in CO2 desorption efficiency. More importantly, compared to the reference MEA, the CO2 desorption duties of ZrO(OH)2 and FeOOH-aided MEA significantly reduced by 45 and 47% respectively, which are better than those of most other reported catalysts. The large surface area, pore volume, pore diameter, and amount of surface hydroxyl groups of ZrO(OH)2 and FeOOH afforded the catalytic performance by promoting the adsorption of alkaline speciation (e.g., MEA and HCO3–) onto the particle surface

On-Chip Construction of Liver Lobule-like Microtissue and Its Application for Adverse Drug Reaction Assay

Engineering the liver <i>in vitro</i> is promising to provide functional replacement for patients with liver failure, or tissue models for drug metabolism and toxicity analysis. In this study, we describe a microfluidics-based biomimetic approach for the fabrication of an <i>in vitro</i> 3D liver lobule-like microtissue composed of a radially patterned hepatic cord-like network and an intrinsic hepatic sinusoid-like network. The hepatic enzyme assay showed that the 3D biomimetic microtissue maintained high basal CYP-1A1/2 and UGT activities, responded dynamically to enzyme induction/inhibition, and preserved great hepatic capacity of drug metabolism. Using the established biomimetic microtissue, the potential adverse drug reactions that induced liver injury were successfully analyzed via drug–drug interactions of clinical pharmaceuticals. The results showed that predosed pharmaceuticals which agitated CYP-1A1/2 and/or UGT activities would alter the toxic effect of the subsequently administrated drug. All the results validated the utility of the established biomimetic microtissue in toxicological studies <i>in vitro</i>. Also, we anticipate the microfluidics-based bioengineering strategy would benefit liver tissue engineering and liver physiology/pathophysiology studies, as well as <i>in vitro</i> assessment of drug-induced hepatotoxicity

Fabrication of Polydiacetylene Liposome Chemosensor with Enhanced Fluorescent Self-Amplification and Its Application for Selective Detection of Cationic Surfactants

Polydiacetylene (PDA) materials have been adopted as one of the powerful conjugated polymers for sensing applications due to their unique optical properties. In this paper, we present a new PDA liposome-based sensor system with enhanced fluorescent self-amplification by tuning a fluorophore fluorescence emission. In this system, a 1,8-naphthalimide derivative employed as a highly fluorescent fluorophore was incorporated into a PDA supermolecule. During the formation of blue PDA liposomes, the fluorescence emission of the fluorophore can be directly quenched, while thermal-induced phase transition of PDA liposomes from blue to red can readily restore this fluorescence emission. These phenomena could be ascribed to the tunable Förster energy transfer between the excited fluorophore and PDA conjugated framework. To demonstrate the sensing performance of this newly prepared PDA liposome-based sensor, the sensor with fluorescent self-amplification was successfully applied for the detection of cationic surfactants (CS). The results show that the PDA liposomes displayed a distinct color change and fluorescence restoration in the presence of cationic surfactant species, and allowed detection of cationic surfactants with high sensitivity and selectivity. The limit of detection for target CS, such as cetyltrimethylammonium bromide (CTAB), can reach as low as 184 nM. Compared to the traditional methods based on colorimetric PDA liposomes, this newly fabricated PDA sensor system was superior for sensitivity. Thus, our findings offer an avenue for the design and development of new types of PDA sensors with enhanced sensitivity

Monitoring Tumor Response to Anticancer Drugs Using Stable Three-Dimensional Culture in a Recyclable Microfluidic Platform

The development and application of miniaturized platforms with the capability for microscale and dynamic control of biomimetic and high-throughput three-dimensional (3D) culture plays a crucial role in biological research. In this study, pneumatic microstructure-based microfluidics was used to systematically demonstrate 3D tumor culture under various culture conditions. We also demonstrated the reusability of the fabrication-optimized pneumatic device for high-throughput cell manipulation and 3D tumor culture. This microfluidic system provides remarkably long-term (over 1 month) and cyclic stability. Furthermore, temporal and high-throughput monitoring of tumor response to evaluate the therapeutic efficacy of different chemotherapies, was achieved based on the robust culture. This advancement in microfluidics has potential applications in the fields of tissue engineering, tumor biology, and clinical medicine; it also provides new insight into the construction of high-performance and recyclable microplatforms for cancer research

Electrochemically Reduced Carboxyl Graphene Modified Electrode for Simultaneous Determination of Guanine and Adenine

<div><p>An electrochemically reduced carboxyl graphene modified glassy carbon electrode (ERCGr/GCE) was prepared from a carboxyl graphene modified glassy carbon electrode (CGr/GCE) and employed for the simultaneous determination of guanine and adenine. The ERCGr/GCE showed an enhanced voltammetric response toward the oxidation of guanine and adenine compared with the CGr/GCE because the conductivity and electrochemical active surface area increased during the reduction process. The voltammetric peak current was linearly dependent on guanine and adenine concentration over the ranges of 0.5–10 and 2.5–50 µmol L⁻¹, respectively. The detection limits were 0.15 µmol L⁻¹ for guanine and 0.10 µmol L⁻¹ for adenine in 50 µmol L⁻¹ phosphate buffer at pH 6.86. Determination of guanine and adenine in thermally denatured herring sperm DNA showed that the ratio of guanine/adenine was 0.758 demonstrating practical application of the ERCGr/GCE.</p></div

Investigation of Hypoxia-Induced Myocardial Injury Dynamics in a Tissue Interface Mimicking Microfluidic Device

Myocardial infarction is a major cause of morbidity and mortality worldwide. However, the methodological development of a spatiotemporally controllable investigation of the damage events in myocardial infarction remains challengeable. In the present study, we describe a micropillar array-aided tissue interface mimicking microfluidic device for the dynamic study of hypoxia-induced myocardial injury in a microenvironment-controllable manner. The mass distribution in the device was visually characterized, calculated, and systematically evaluated using the micropillar-assisted biomimetic interface, physiologically relevant flows, and multitype transportation. The fluidic microenvironment in the specifically functional chamber for cell positioning and analysis was successfully constructed with high fluidic relevance to the myocardial tissue. We also performed a microenvironment-controlled microfluidic cultivation of myocardial cells with high viability and regular structure integration. Using the well-established culture device with a tissue-mimicking microenvironment, a further on-chip investigation of hypoxia-induced myocardial injury was carried out and the varying apoptotic responses of myocardial cells were temporally monitored and measured. The results show that the hypoxia directionally resulted in observable cell shrinkage, disintegration of the cytoskeleton, loss of mitochondrial membrane potential, and obvious activation of caspase-3, which indicates its significant apoptosis effect on myocardial cells. We believe this microfluidic device can be suitable for temporal investigations of cell activities and responses in myocardial infarction. It is also potentially valuable to the microcontrol development of tissue-simulated studies of multiple clinical organ/tissue disease dynamics

Small Molecule-Initiated Light-Activated Semiconducting Polymer Dots: An Integrated Nanoplatform for Targeted Photodynamic Therapy and Imaging of Cancer Cells

Photodynamic therapy (PDT) is a noninvasive and light-activated method for cancer treatment. Two of the vital parameters that govern the efficiency of PDT are the light irradiation to the photosensitizer and visual detection of the selective accumulation of the photosensitizer in malignant cells. Herein, we prepared an integrated nanoplatform for targeted PDT and imaging of cancer cells using folic acid and horseradish peroxidase (HRP)-bifunctionalized semiconducting polymer dots (FH-Pdots). In the FH-Pdots, meta-tetra­(hydroxyphenyl)-chlorin (m-THPC) was used as photosensitizer to produce cytotoxic reactive oxygen species (ROS); fluorescent semiconducting polymer poly­[2-methoxy-5-((2-ethylhexyl)­oxy)-<i>p</i>-phenylenevinylene] was used as light antenna and hydrophobic matrix for incorporating m-THPC, and amphiphilic Janus dendrimer was used as a surface functionalization agent to conjugate HRP and aminated folic acid onto the surface of FH-Pdots. Results indicated that the doped m-THPC can be simultaneously excited by the on-site luminol–H₂O₂–HRP chemiluminescence system through two paths. One is directly through chemiluminescence resonance energy transfer (CRET), and the other is through CRET and subsequent fluorescence resonance energy transfer. In vitro PDT and specificity studies of FH-Pdots using a standard transcriptional and translational assay against MCF-7 breast cancer cells, C6 glioma cells, and NIH 3T3 fibroblast cells demonstrated that cell viability decreased with increasing concentration of FH-Pdots. At the same concentration of FH-Pdots, the decrease in cell viability was positively relevant with increasing folate receptor expression. Results from in vitro fluorescence imaging exhibited that more FH-Pdots were internalized by cancerous MCF-7 and C6 cells than by noncancerous NIH 3T3 cells. All the results demonstrate that the designed semiconducting FH-Pdots can be used as an integrated nanoplatform for targeted PDT and on-site imaging of cancer cells

Fluorenone Organic Crystals: Two-Color Luminescence Switching and Reversible Phase Transformations between π–π Stacking-Directed Packing and Hydrogen Bond-Directed Packing

Organic solid-state luminescence switching (SLS) materials with the ability to reversibly switch the luminescence by altering the mode of molecular packing without changing the chemical structures of their component molecules have attracted considerable interest in recent years. In this work, we design and synthesize a new class of 2,7-diphenylfluorenone derivatives (compounds <b>1</b>–<b>6</b>) that exhibit prominent aggregation-induced emission (AIE) properties with high solid-state fluorescence quantum yields (29–65%). Among them, 2,7-bis­(4-methoxyphenyl)-9<i>H</i>-fluoren-9-one (<b>2</b>) and 2,7-bis­(4-ethylphenyl)-9<i>H</i>-fluoren-9-one (<b>6</b>) display reversible stimuli-responsive solid-state luminescence switching. Compound <b>2</b> transforms between red and yellow crystals (the emission wavelength switches between 601 and 551 nm) under the stimuli of temperature, pressure, or solvent vapor. Similarly, compound <b>6</b> exhibits SLS behavior, with luminescence switching between orange (571 nm) and yellow (557 nm). Eight X-ray single-crystal structures, characterization of the photophysical properties, powder X-ray diffraction, and differential scanning calorimetry provide insight into the structure–property relationships of the solid-state fluorescence behavior. The results indicate that the variable solid-state luminescence of the fluorenone derivatives is attributed to the formation of different excimers in different solid phases. Additionally, the stimuli-responsive reversible phase transformations of compounds <b>2</b> and <b>6</b> involve a structural transition between π–π stacking-directed packing and hydrogen bond-directed packing. The results also demonstrate the feasibility of our design strategy for new solid-state luminescence switching materials: introduction of both π–π stacking and hydrogen bonding into an AIE structure to obtain a metastable solid/crystalline state luminescence system