XPS analysis of genomic DNA adsorbed on PEI-modified surfaces

Preparation of multifunctional PET membrane and its application in high-efficiency filtration and separation in complex environment

Nowadays, effluent treatment is a severe challenge mainly because of its complex composition, which includes oil, heavy metal ions, and dyes. Developing new intelligent membranes is one of the strategies to tackle these significant challenges in wastewater treatment. In this study, we fabricated asymmetric polyethylene glycol terephthalate (PET) membranes by grafting cross-linked poly (itaconic anhydride) (CL-PITA) nanoparticles onto the irradiated face. These nanoparticles were then functionalized with polyethyleneimine (PEI) and protonated with HCl to introduce numerous active electropositive amine groups. The fundamental purpose was to increase surface roughness, introduce numerous hydrophilic groups, and modify it to create a multi-functional PET membrane to separate complex environments. The promising results demonstrated that the protonated PET-g-ITA/DVB(10)-cat membrane exhibited excellent separation efficiencies (SE) for water/light oil, water/heavy oil and oil-in-water (O/W) emulsion. Compared to PET-g-ITA/DVB(0)-cat, it showed superior performance in SE for O/W emulsion and flux decay for water/light oil after 10 cycles. More interestingly, owing to numerous positively charged active amino groups and negativley charged carboxylate groups, the intelligent membrane exhibited a high removal rate of ca. 90 % for anionic dye (congo red) and heavy metals (Cu2+ and Co2+), showing great potential in complex water treatment environments.

Different Strategies for the Microfluidic Purification of Antibiotics from Food: A Comparative Study

The presence of residual antibiotics in food is increasingly emerging as a worrying risk for human health both for the possible direct toxicity and for the development of antibiotic-resistant bacteria. In the context of food safety, new methods based on microfluidics could offer better performance, providing improved rapidity, portability and sustainability, being more cost effective and easy to use. Here, a microfluidic method based on the use of magnetic microbeads specifically functionalized and inserted in polymeric microchambers is proposed. The microbeads are functionalized either with aptamers, antibodies or small functional groups able to interact with specific antibiotics. The setup of these different strategies as well as the performance of the different functionalizations are carefully evaluated and compared. The most promising results are obtained employing the functionalization with aptamers, which are able not only to capture and release almost all tetracycline present in the initial sample but also to deliver an enriched and simplified solution of antibiotic. These solutions of purified antibiotics are particularly suitable for further analyses, for example, with innovative methods, such as label-free detection. On the contrary, the on-chip process based on antibodies could capture only partially the antibiotics, as well as the protocol based on beads functionalized with small groups specific for sulfonamides. Therefore, the on-chip purification with aptamers combined with new portable detection systems opens new possibilities for the development of sensors in the field of food safety.

Super-adsorbent microspheres based on a triallyl isocyanurate-maleic anhydride copolymer for the removal of organic pollutants from water

Owing to the frequent occurrence of diclofenac sodium (DS) in fresh aquatic environments and its potential toxicity towards living organisms, the effective removal of DS has attracted worldwide attention. Herein, a green and efficient strategy to fabricate crosslinked microspheres with interconnected mesoporous structures and abundant adsorption active sites was developed. With this strategy, triallyl isocyanurate (TAIC)-maleic anhydride (MAH) copolymer microspheres (TMs) with a diameter of 1.19-1.35 μm were first prepared by self-stabilized precipitation (2SP) polymerization, and the TMs possess a large amount reactive anhydride groups (62.5-71.8 mol%), a specific surface area of 51.6-182.4 m² g^-1 and a mesoporous structure (average pore size: 3.4-3.8 nm). Then the TMs were further functionalized with polyethylenimine (PEI) to give rise to cationic microspheres (Cat-TMs), which showed excellent adsorption performance to DS with a rapid adsorption rate (reached equilibrium within 30 min), a very high equilibrium adsorption capacity (1421 mg g^-1) and excellent recyclability. The pseudo-second-order model and Langmuir model were a good fit for the adsorption kinetic and isotherm process, respectively. Furthermore, due to the high cation density (4.291 mmol g^-1) and excellent pH buffer capacity of Cat-TMs, the adsorption capacity can be maintained at a high level within the pH range of 6-10. The regenerated Cat-TMs showed only a slight loss (<5%) in the adsorption capacity even after 5 adsorption-desorption cycles. In short, Cat-TMs can be considered as a highly promising adsorbent for the rapid and ultra-efficient removal of anionic organic contaminants and have significant potential to be applied in wastewater treatment.

Rapid and Unamplified Detection of SARS-CoV-2 RNA via CRISPR-Cas13a-Modified Solution-Gated Graphene Transistors

The disease caused by severe acute respiratory syndrome coronavirus, SARS-CoV-2, is termed COVID-19. Even though COVID-19 has been out for more than two years, it is still causing a global pandemic. Due to the limitations of sample collection, transportation, and kit performance, the traditional reverse transcription-quantitative polymerase chain reaction (RT-qPCR) method has a long detection period and high testing costs. An increased risk of infection is inevitable, since many patients may not be diagnosed in time. The CRISPR-Cas13a system can be designed for RNA identification and knockdown, as a promising platform for nucleic acid detection. Here, we designed a solution-gated graphene transistor (SGGT) biosensor based on the CRISPR-Cas13a system. Using the gene-targeting capacity of CRISPR-Cas13a and gate functionalization via multilayer modification, SARS-CoV-2 nucleic acid sequences can be quickly and precisely identified without the need for amplification or fluorescence tagging. The limit of detection (LOD) in both buffer and serum reached the aM level, and the reaction time was about 10 min. The results of the detection of COVID-19 clinical samples from throat swabs agree with RT-PCR. In addition, the interchangeable gates significantly minimize the cost and time of device fabrication. In a nutshell, our biosensor technology is broadly applicable and will be suitable for point-of-care (POC) testing.

A highly sensitive fluorescent nanoprobe for the amplified detection of formaldehyde

Non-conjugated polymer nanoparticles (PNPs) have been widely reported for analytical applications; however, the development of an effective fluorescence signal-amplification scheme based on PNPs remains challenging. In this study, polyethyleneimine-based polymer nanoparticles (PEI-PNPs) were synthesized for interrogating the fluorescence signal-amplification analytical application of the PNPs. The PEI-PNPs with an aggregated PEI polymer structure were able to confine a large density of sub-fluorophores on an individual nanoparticle, enabling the realization of a signal-amplification effect. Herein, formaldehyde (FA) was utilized for enhancing the fluorescence intensity of the PEI-PNPs as a model to confirm our proof-of-concept strategy. Our results showed that a more than 9-fold signaling-enhancing ability for the sensing of FA was observed using the PEI-PNPs prepared with a higher PEI concentration. The possible mechanism for the FA amplified sensing was studied. In particular, the FA-recognition units were sub-fluorophores of PEI-PNPs, which were simultaneously formed with the preparation of the PEI-PNPs avoiding the leakage effect of dyes. We believe that the water-soluble and biocompatible PEI-PNPs are promising candidates for the detection of endogenous FA in living systems.

Laser-Assisted Direct Grafting of Poly(ethyleneimine) on Poly(methyl methacrylate)

Demand for direct chemical modification of functional material on a surface is increasing in various fields. A new approach for a functionalized surface is investigated by applying a conventional laser in order to generate chemical activation by photothermal energy. Poly(ethyleneimine) (PEI), with a high density of amino groups, is chemically grafted on poly(methyl methacrylate) (PMMA) by irradiation of a CO₂ laser (10.6 μm). Laser parameters such as power, scan rate, and focal length are observed to play an important role in order to introduce effective photothermal energy for the chemical reaction between PEI and PMMA. By optimization of laser parameters, the amide compound is produced as a result of the reaction of amine from PEI and the ester of PMMA successfully. The PMMA surface modified with PEI is analyzed by XPS and TOF-SIMS to identify the functional groups. Furthermore, the surface is characterized in terms of wettability, adhesion force, and surface charge for various applications. Finally, reaction with dye and metal on the amine-terminated PMMA shows promising results in supplying a selective and reliable functional substrate.

A stable and easily regenerable solid amine adsorbent derived from a polyethylenimine-impregnated dialdehyde-cellulose/graphene-oxide composite

A DAC-GO composite adsorbent with high CO2 adsorption capacity and low regeneration energy consumption was prepared through oxidation-gelation and crosslinking-amination.

Increase in Interfacial Adhesion and Electrochemical Charge Storage Capacity of Polypyrrole on Au Electrodes Using Polyethyleneimine

High-performance devices based on conducting polymers (CPs) require the fabrication of a thick CP-coated electrode with high stability. Herein, we propose a method for enhancing the interfacial adhesion strength between a gold electrode and an electropolymerized polypyrrole (pPy) layer by introducing a polyethyleneimine (PEI) layer. Although this insulating layer hinders the initial growth of the pPy layer on the Au surface, it improves the adhesion by up to 250%. Therefore, a thick layer of pPy can be fabricated without delamination during drying. X-ray photoelectron spectroscopy shows that the PEI layer interacts with the Au surface via polar/ionic groups and van der Waals interactions. Scanning electron microscopy reveals that the cohesion of the pPy layer is stronger than the interfacial adhesion between the PEI layer and the pPy layer. Importantly, the electroactivities of pPy and its dopant are unaffected by the PEI layer, and the electrochemical storage capacity of the pPy layers on the PEI-coated Au electrodes increases with thickness, reaching ~530 mC/cm². Negative potential sweep is detrimental to pPy layer adhesion: pPy layers on a bare Au electrode peel off instantly as the potential is swept from 0.2 to −0.7 V, and most of the charge stored in the layer becomes inaccessible. In contrast, pPy layers deposited on PEI coated Au electrode are mechanically stable and majority of the charge can be accessed, demonstrating that this method is also effective for enhancing electrochemical stability. Our simple approach can find utility in various applications involving CP-coated electrodes, where thickness-dependent performance must be improved without loss of stability.

Prussian blue nanocubes with an open framework structure coated with polyoxometalates as a highly sensitive platform for ascorbic acid detection in drinks/human urine

A novel PB NC@POM platform was constructed and demonstrated high electrochemical response to ascorbic acid due to the excellent synergistic effect.

Self-assembly of zinc hydroxystannate on amorphous hydrous TiO2 solid sphere for enhancing fire safety of epoxy resin

Zinc hydroxystannate (ZHS) was fabricated on the surface of amorphous hydrous TiO₂ solid spheres (AHTSS) via a layer-by-layer method for improving the fire safety of epoxy resin. AHTSS@PEI@ZHS was prepared by self-assembly of AHTSS, PEI and ZHS. The well-organized fabrication process was proved by TEM, XPS, XRD and SEM tests. TG results illustrated that the incorporation of AHTSS@PEI@ZHS show a higher residue compared with the addition of AHTSS or ZHS alone. In addition, AHTSS@PEI@ZHS filled EP composites exhibits improved flame retardancy and smoke suppression properties evaluated by cone calorimeter test. TG-IR results also indicated that the catalytic labyrinth structure of AHTSS@PEI@ZHS can effectively decrease the permeation of volatile organic compounds, thereby improving the fire safety of EP resin.