Polymer Polyethylenimine Research Articles

Lead-Free Perovskite Thin Films for Gas Sensing through Surface Acoustic Wave Device Detection.

Thin film technology shows great promise in fabricating electronic devices such as gas sensors. Here, we report the fabrication of surface acoustic wave (SAW) sensors based on thin films of (1 - x) Ba(Ti0.8Zr0.2)O3-x(Ba0.7Ca0.3)TiO3 (BCTZ50, x = 50) and Polyethylenimine (PEI). The layers were deposited by two laser-based techniques, namely pulsed laser deposition (PLD) for the lead-free material and matrix assisted pulsed laser evaporation (MAPLE) for the sensitive polymer. In order to assay the impact of the thickness, the number of laser pulses was varied, leading to thicknesses between 50 and 350 nm. The influence of BCTZ film's crystallographic features on the characteristics and performance of the SAW device was studied by employing substrates with different crystal structures, more precisely cubic Strontium Titanate (SrTiO3) and orthorhombic Gadolinium Scandium Oxide (GdScO3). The SAW sensors were further integrated into a testing system to evaluate the response of the BCTZ thin films with PEI, and then subjected to tests for N2, CO2 and O2 gases. The influence of the MAPLE's deposited PEI layer on the overall performance was demonstrated. For the SAW sensors based on BCTZ/GdScO3 thin films with a PEI polymer, a maximum frequency shift of 39.5 kHz has been obtained for CO2; eight times higher compared to the sensor without the polymeric layer.

Designing Nanomedicines for Breast Cancer Therapy.

In 2020, breast cancer became the most diagnosed cancer worldwide. Conventional chemotherapies have major side effects due to their non-specific activities. Alternatively, short interfering RNA(siRNA)-carrying nanoparticles (NPs) have a high potential to overcome this non-specificity. Lipid-substituted polyethyleneimine (PEI) polymers (lipopolymers) have been reported as efficient non-viral carriers of siRNA. This study aims to engineer novel siRNA/lipopolymer nanocomplexes by incorporating anionic additives to obtain gene silencing through siRNA activity with minimal nonspecific toxicity. We first optimized our polyplexes in GFP+ MDA-MB-231 cells to effectively silence the GFP gene. Inclusion of phosphate buffer with pH 8.0 as complex preparation media and N-Lauroylsarcosine Sodium Salt as additive, achieved ~80% silencing with the least amount of undesired cytotoxicity, which was persistent for at least 6 days. The survivin gene was then selected as a target in MDA-MB-231 cells since there is no strong drug (i.e., small organic molecule) for inhibition of its oncogenic activity. The qRT-PCR, flow cytometry analysis and MTT assay revealed >80% silencing, ~95% cell uptake and >70% cell killing by the same formulation. We conclude that our lipopolymer can be further investigated as a lead non-viral carrier for breast cancer gene therapy.

Facile preparation of PEGylated polyethylenimine polymers as vaccine carriers with reduced cytotoxicity and enhanced Interleukin-2 (IL-2) production.

Developing low-cost, easy-to-prepare, biocompatible and highly efficient vaccine carriers is a promising approach to realize practical cancer immunotherapy. In this study, through facile modification of mPEG5k-4-toluenesulfonate (mPEG5k-OTs) on PEI25k under mild conditions, a series of "stealth" mPEG5k-PEI25k polymers (PP1, PP2 and PP3) were prepared, their structures and physicochemical properties were characterized and theoretically analyzed. The polymers could bind/load ovalbumin (OVA) to form mPEG5k-PEI25k/OVA complexes as negatively charged nanoparticles with small hydrodynamic particle size (80-210nm) and narrow size distribution. Compared to PEI25k/OVA, lower cytotoxicity could be achieved on mPEG5k-PEI25k/OVA complexes in dendritic cells (DCs). In DCs-RF 33.70T-cells co-culture system, the mPEG5k-PEI25k/OVA complexes could bring about higher IL-2 production /secretion than that of PEI25k/OVA, notably, the optimum IL-2 secretion could reach 9.3-folds of the PEI25k/OVA under serum condition (10% FBS). Moreover, the cell biological features could be optimized by selecting suitable mPEG5k-grafting ratios and/or mPEG5k-PEI25k/OVA weight ratios. Intracellular imaging results showed that the mPEG5k-PEI25k(PP3)/Rhodamine-OVA complexes mainly localized inside lysosomes. Taken together, this work provided a facile method to prepare "stealth" PEGylated-PEI25k polymers with reduced cytotoxicity, promoted OVA cross-presentation efficiency and improved serum compatibility towards cancer immunotherapy.

Flexible Fabrication and Hybridization of Bioactive Hydrogels with Robust Osteogenic Potency.

Osteogenic scaffolds reproducing the natural bone composition, structures, and properties have represented the possible frontier of artificially orthopedic implants with the great potential to revolutionize surgical strategies against the bone-related diseases. However, it is difficult to achieve an all-in-one formula with the simultaneous requirement of favorable biocompatibility, flexible adhesion, high mechanical strength, and osteogenic effects. Here in this work, an osteogenic hydrogel scaffold fabricated by inorganic-in-organic integration between amine-modified bioactive glass (ABG) nanoparticles and poly(ethylene glycol) succinimidyl glutarate-polyethyleneimine (TSG-PEI) network was introduced as an all-in-one tool to flexibly adhere onto the defective tissue and subsequently accelerate the bone formation. Since the N-hydroxysuccinimide (NHS)-ester of tetra-PEG-SG polymer could quickly react with the NH2-abundant polyethyleneimine (PEI) polymer and ABG moieties, the TSG-PEI@ABG hydrogel was rapidly formed with tailorable structures and properties. Relying on the dense integration between the TSG-PEI network and ABG moieties on a nano-scale level, this hydrogel expressed powerful adhesion to tissue as well as durable stability for the engineered scaffolds. Therefore, its self-endowed biocompatibility, high adhesive strength, compressive modulus, and osteogenic potency enabled the prominent capacities on modulation of bone marrow mesenchymal stem cell (BMSCs) proliferation and differentiation, which may propose a potential strategy on the simultaneous scaffold fixation and bone regeneration promotion for the tissue engineering fields.

Electrospun polyethylenimine (PEI)-derived nitrogen enriched carbon nanofiber for supercapacitors with artificial neural network modeling

This paper presents the utilization of polyethylenimine (PEI) polymer to obtain freestanding, binder-free, and nitrogen- enriched carbon nanofibers (NCNFs) by electrospinning which is an easy and fast method. The PEI polymer played a significant role as a poring agent for the adjustment of surface area and as the heteroatom doping to increase conductivity. NCNFs-10 electrode exhibited a specific capacitance of 200 F/g at 1 A/g with a good retention of 84.25 % at 10 A/g in three electrode system. The assembled supercapacitor had a specific energy of 5.57 Wh/kg at 125 W/kg with a good cycling performance of 80.5 % after 10,000 cycles. Furthermore, an artificial neural network (ANN) method was utilized to understand the relationship between the CNF's structure and supercapacitor performance by modeling the specific capacitance. The input factors were specific surface area (SBET), nitrogen doping (N% at), graphitization degree (ID/IG), internal resistance (Rs), pore size (Vpor), micropore volume (Vmic), the average diameter (Dave), and mesopore volume (Vmeso). Results showed that the first three remarkable variables are SBET, N (%at), and ID/IG.

Baicalin functionalized PEI-heparin carbon dots as cancer theranostic agent

The worldwide prevalence of cancer and its significantly rising risks with age have garnered the attention of nanotechnology for prompt detection and effective therapy with minimal or no adverse effects. In the current study, heparin (HP) polymer derived heteroatom (N, S-) co-doped CDs were synthesized using hydrothermal synthesis method to efficiently deliver natural anticancer compound baicalin (BA). Heparin carbon dots (HCDs) were passivated with polyethylenimine (PEI) to improve its fluorescence quantum yield. The surface passivation of CDs by polycationic PEI polymer not only facilitated loading of BA, but also played a crucial role in the pH-responsive drug delivery. The sustained release of BA (up to 80 %) in mildly acidic pH (5.5 and 6.5) conditions endorsed its drug delivery potential for cancer-specific microenvironments. BA-loaded PHCDs exhibited enhanced anticancer activity as compared to BA/PHCDs indicating the effectiveness of the nanoformulation, Furthermore, the flow cytometry analysis confirmed that BA-PHCDs treated cells were arrested in the G2/M phase of cell cycle and had a higher potential for apoptosis. Bioimaging study demonstrated the excellent cell penetration efficiency of PHCDs with complete cytoplasmic localization. All this evidence comprehensively demonstrates the potency of BA-loaded PHCDs as a nanotheranostic agent for cancer.

Implication of the Autophagy-Related Protein Beclin1 in the Regulation of EcoHIV Replication and Inflammatory Responses.

The protein Beclin1 (BECN1, a mammalian homologue of ATG6 in yeast) plays an important role in the initiation and the normal process of autophagy in cells. Moreover, we and others have shown that Beclin1 plays an important role in viral replication and the innate immune signaling pathways. We previously used the cationic polymer polyethyleneimine (PEI) conjugated to mannose (Man) as a non-viral tool for the delivery of a small interfering (si) Beclin1-PEI-Man nanoplex, which specifically targets mannose receptor-expressing glia (microglia and astrocytes) in the brain when administered intranasally to conventional mice. To expand our previous reports, first we used C57BL/6J mice infected with EcoHIV and exposed them to combined antiretroviral therapy (cART). We show that EcoHIV enters the mouse brain, while intranasal delivery of the nanocomplex significantly reduces the secretion of HIV-induced inflammatory molecules and downregulates the expression of the transcription factor nuclear factor (NF)-kB. Since a spectrum of neurocognitive and motor problems can develop in people living with HIV (PLWH) despite suppressive antiretroviral therapy, we subsequently measured the role of Beclin1 in locomotor activities using EcoHIV-infected BECN1 knockout mice exposed to cART. Viral replication and cytokine secretion were reduced in the postmortem brains recovered from EcoHIV-infected Becn1+/- mice when compared to EcoHIV-infected Becn1+/+ mice, although the impairment in locomotor activities based on muscle strength were comparable. This further highlights the importance of Beclin1 in the regulation of HIV replication and in viral-induced cytokine secretion but not in HIV-induced locomotor impairments. Moreover, the cause of HIV-induced locomotor impairments remains speculative, as we show that this may not be entirely due to viral load and/or HIV-induced inflammatory cytokines.

Pyrolysis acetylation: A novel on-line Py-GC-MS derivatisation for the characterisation of nitrogen-containing polymers

Several on-line chemical reactions have been combined with Py-GC-MS to improve the chromatographic behaviour of polar pyrolysis products. Derivatisations, principally methylation and silylation, have been widely employed to the analysis of oxygenated pyrolysis products, while the conversion of nitrogen-containing compounds resulted more challenging. The present study shows that amines can be efficiently converted into the corresponding N-substituted amides (acetamides) by conducting pyrolysis in the presence of acetic anhydride (PyAc). PyAc was assessed on three common N-containing polymer families, polyethylenimine (PEI, linear and branched), polyurethane (PUR, based on the methylenediphenyl diisocianate monomer) and nylons (polyamide PA6 and PA66). Upon PyAc, PEI produced a series of N-methyl, ethyl, ethenyl acetamides indicative of the formation of several alkylated monoamines that were more difficult to detect in the free form by conventional Py-GC-MS. Acetyl derivatives of linear acyclic polyamines and piperazines were also identified confirming previous investigations. In the case of PUR, the acetylated 4,4′-diaminodiphenylmethane was generated along with the diisocyanate monomer. PyAc of PA66 produced the acetyl derivative of 1,6-hexyldiamine, while the caprolactam of PA6 was only partially acetylated. The effectiveness of acetylation was confirmed by PyAc of calibration standards for microplastic analysis. Besides the acetylated amines distinctive of PUR and PA66, the acetylated forms of 1,4-butandiol from PUR and bisphenol A from polycarbonate were detected. The results showed the potential of extension of PyAc to other polymer families and highlighted some weaknesses to be solved.

Development and Characterization of CO2-Responsive Intelligent Polymer Sealant.

In this study, we present an innovative intelligent polymer sealant designed to mitigate CO2 leakage during underground geological storage (CCUS). This sealant is formulated by cross-linking CO2-responsive polymers, specifically acrylamide (AM) and N-[3-(dimethylamino) propyl] methacrylamide (DMAPMA), with polyethylenimine (PEI) serving as the cross-linking agent. The polymer sealant's characteristics were systematically investigated, varying the CO2-responsive polymer content (1.5 wt %) and PEI content (0.1-0.6 wt %). A comprehensive analysis encompassing the rheological properties, thermal behavior, conductivity, and microstructures was conducted. Experimental results indicate that the polymer sealant exhibits excellent injectability, rapid response kinetics, thermal stability, and robust mechanical strength. Upon encountering CO2, the polymer system undergoes a transition from sol to gel state, forming a surface-smooth, uniformly porous three-dimensional (3D) network skeleton structure. Remarkably, the gel's modulus remains relatively unaffected by the shear frequency. Core fluid displacement experiments demonstrated a substantial sealing efficiency of 73.6% for CO2 and an impressive subsequent injection water sealing rate of 96.2%, underscoring its superior sealing and migration performance. In conclusion, the proposed CO2-responsive gel sealant exhibits an exceptional potential for successful utilization in CCUS operations. This advancement introduces a novel avenue to enhance the effectiveness of CO2-responsive gel sealants, thereby contributing to the advancement of CO2 leakage mitigation strategies in geological storage scenarios.

A surfactant modified solid amine adsorbent to enhance CO2 adsorption performance

Solid-amine adsorbents are promising CO2 post-combustion adsorption materials to mitigate global warming. As one of the most important evaluation criteria, the CO2 adsorption capacity of the adsorbent was determined by both kinetic and thermodynamic factors, while high temperature is good for mass transfer and low temperature is advantageous for equilibrium to move towards adsorption. In this study, surfactants were added into polyethylenimine (PEI) cryogel to enhance mass transfer and reduce the adsorption temperature, thereby promoting its adsorption capacity. With the addition of polyethylene glycol (PEG200), the CO2 adsorption capacity reached a maximum value of 6.48 mmol/g at 65 °C, and the amine efficiency reached a maximum value of 0.52 mol C/mol N at 45 °C. Further characterization revealed that the addition of PEG not only enhanced the mass transfer, but also changed the chemisorption mechanisms, which were very similar to the effects of water. Besides, PEG would form hydrogen bonds with the PEI polymer network and showed stable regeneration capacity, thereby exhibiting a greater application potential.

Overcoming the blood-brain barrier? - prediction of blood-brain permeability of hydrophobically modified polyethylenimine polyplexes for siRNA delivery into the brain with in vitro and in vivo models

The blood-brain barrier (BBB) is a highly selective biological barrier that represents a major bottleneck in the treatment of all types of central nervous system (CNS) disorders. Small interfering RNA (siRNA) offers in principle a promising therapeutic approach, e.g., for brain tumors, by downregulating brain tumor-related genes and inhibiting tumor growth via RNA interference. In an effort to develop efficient siRNA nanocarriers for crossing the BBB, we utilized polyethyleneimine (PEI) polymers hydrophobically modified with either stearic-acid (SA) or dodecylacrylamide (DAA) subunits and evaluated their suitability for delivering siRNA across the BBB in in vitro and in vivo BBB models depending on their structure. Physicochemical characteristics of siRNA-polymer complexes (polyplexes (PXs)), e.g., particle size and surface charge, were measured by dynamic light scattering and laser Doppler anemometry, whereas siRNA condensation ability of polymers and polyplex stability was evaluated by spectrophotometric methods. The composition of the biomolecule corona that absorbs on polyplexes upon encountering physiological fluids was investigated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and by a liquid chromatography-tandem mass spectrometry (LC-MS-MS) method. Cellular internalization abilities of PXs into brain endothelial cells (hCMEC/D3) was confirmed, and a BBB permeation assay using a human induced pluripotent stem cell (hiPSC)–derived BBB model revealed similar abilities to cross the BBB for all formulations under physiological conditions. However, biodistribution studies of radiolabeled PXs in mice were inconsistent with in vitro results as the detected amount of radiolabeled siRNA in the brain delivered with PEI PXs was higher compared to PEI-SA PXs. Taken together, PEI PXs were shown to be a suitable nanocarrier to deliver small amounts of siRNA across the BBB into the brain but more sophisticated human BBB models that better represent physiological conditions and biodistribution are required to provide highly predictive in vitro data for human CNS drug development in the future.

Polyethyleneimine efficiently extracts recombinant cytoplasmatic green fluorescent protein produced in Escherichia coli with high purity.

We used a polycationic polymer polyethyleneimine (PEI) to develop a method to extract recombinant proteins produced in the Escherichia coli (E. coli) cytosol. Compared to high pressure homogenization, commonly used to disrupt E. coli cells, our extraction method leads to higher purity of extracts. Upon addition of PEI to the cells, flocculation occurs and the recombinant protein gradually diffuses out of the PEI/cell network. While several aspects such as the E. coli strain, the cell or PEI concentration as well as the protein titer and the pH of the buffer seem to influence the extraction rate, our results show that the PEI molecule (molecular weight and structure) must be chosen appropriately for protein extraction. The method works well with resuspended cells but can also be applied directly to fermentation broths at higher PEI concentration. This extraction approach allows for effective reduction of DNA, endotoxins, and host cell proteins levels by 2 to 4 orders of magnitude, and drastically facilitate the subsequent downstream processing steps such as centrifugation and filtration.

Fabrication of NiFe2O4@PEI and NiFe2O4@PPy nanospheres for adsorptive and photocatalytic removal of organic dyes

Spinel ferrites (MFe2O4) and their binary composites with polymers are frequently used to remove and degrade organic dyes due to their magnetic, optical, and biocompatible features. In this study, NiFe2O4, as a superparamagnetic core, was coated using the deposition of polyethylenimine (PEI) and in-situ oxidative polymerization of pyrrole (py). Fourier-transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were employed to analyze NiFe2O4, NiFe2O4@PEI, and NiFe2O4@PPy nanospheres. The morphology and chemical composition of nanoparticles were investigated using field emission scanning electron microscopy (FESEM). The formation of core-shell nanostructure was confirmed using transmission electron microscopy (TEM). A vibrating sample magnetometer (VSM) recorded the magnetic behavior of samples before and after coating polymers. NiFe2O4 superparamagnetic core exhibited high saturation magnetization (Ms) (63.6 emu/g) and easy collection by applying an external magnetic field. The maximum magnetic adsorption efficiencies were determined to be 92% and 72% for NiFe2O4@PEI (NiFe2O4/PEI weight ratio of 1:10) and NiFe2O4@PPy (NiFe2O4/PPy weight ratio of 1:50), respectively. Moreover, optical properties and photocatalytic activity were examined using UV-Vis spectroscopy. The band gap energy value was reduced from 2.3 eV for pure NiFe2O4 to 2.0 eV and 1.9 eV for NiFe2O4@PEI and NiFe2O4@PPy nanoparticles, respectively. The photocatalytic decomposition of methyl orange (MO) under visible illumination was improved after coating NiFe2O4 with PEI and PPy polymers. The results denote that NiFe2O4@PEI and NiFe2O4@PPy core-shell nanostructures are effective candidates for the adsorptive and photocatalytic removal of organic dyes from wastewater.

An efficient silica scale inhibiting strategy for geothermal systems: Combination of cationic and anionic polymers

AbstractCationic silica scale inhibitors are widely used, but are prone to precipitation and exhibit poor performance in geothermal systems. In this study, the cationic polymer polyethyleneimine ethoxylate (PEIE) was first found to have high silica scale inhibition efficiency. Three anionic polymers were added separately to PEIE solutions to alleviate the precipitation and scaling. The inhibition effect of PEIE alone and PEIE with anionic polymers were measured at 40°C without salt and 136.7°C with salt. Molecular dynamics simulation was used to investigate the inhibition mechanism. The results showed that PEIE exhibited good inhibition efficiency of 62% at 40°C without salt and 48% at 136.7°C with salt, while the addition of the anionic polymer acrylic acid‐2‐acrylamide‐2‐methylpropanesulfonic acid (AA/AMPS) to PEIE further improved to 71% and 62%. Compared with commercial inhibitors, the PEIE + AA/AMPS enhanced at least 15% scale inhibition efficiency. This is because the addition of AA/AMPS: (1) enhances the attraction of PEIE to silicic acid and inhibits the silicic acid condensation process; (2) chelates metal ions that promote condensation; and (3) enhances dispersion ability, stabilizing the colloid formed by PEIE and silicic acid. This study provides a promising new inhibitor and efficient strategy for inhibiting silica scale in geothermal systems.

Elimination of Interface Energy Barriers Using Dendrimer Polyelectrolytes with Fractal Geometry.

In this work we study conjugated polyelectrolyte (CPE) films based on polyamidoamine (PAMAM) dendrimers of generations G1 and G3. These fractal macromolecules are compared to branched polyethylenimine (b-PEI) polymer using methanol as the solvent. All of these materials present a high density of amino groups, which protonated by methoxide counter-anions create strong dipolar interfaces. The vacuum level shift associated to these films on n-type silicon was 0.93 eV for b-PEI, 0.72 eV for PAMAM G1 and 1.07 eV for PAMAM G3. These surface potentials were enough to overcome Fermi level pinning, which is a typical limitation of aluminium contacts on n-type silicon. A specific contact resistance as low as 20 mΩ·cm2 was achieved with PAMAM G3, in agreement with the higher surface potential of this material. Good electron transport properties were also obtained for the other materials. Proof-of-concept silicon solar cells combining vanadium oxide as a hole-selective contact with these new electron transport layers have been fabricated and compared. The solar cell with PAMAM G3 surpassed 15% conversion efficiency with an overall increase of all the photovoltaic parameters. The performance of these devices correlates with compositional and nanostructural studies of the different CPE films. Particularly, a figure-of-merit (Vσ) for CPE films that considers the number of protonated amino groups per macromolecule has been introduced. The fractal geometry of dendrimers leads to a geometric increase in the number of amino groups per generation. Thus, investigation of dendrimer macromolecules seems a very good strategy to design CPE films with enhanced charge-carrier selectivity.

Polyethyleneimine (PEI) and Chitosan (CS) grafted with L-cysteine were used as effective materials for Hg(II) adsorption

Naturally derived polymer materials have attracted extensive attention due to their abundant and environmentally friendly characteristics, and have been modified by more and more scholars to meet specific properties. As a global pollutant that seriously affects human health and ecosystems, Hg(II) is posing a great threat to human and environmental safety. Therefore, it is of great practical significance and commercial value to develop cheap, easily available and excellent Hg(II) adsorbent materials. In this paper, two kinds of effective porous materials for Hg(II) adsorption were successfully prepared by using the water-soluble polymer polyethyleneimine(PEI) and chitosan(CS) as raw materials and modified with L-cysteine(L-Cys), which is simple in structure and environmentally friendly. The maximum Hg(II) adsorption capacities of PEI-Cys and CS-Cys were 231.2 mg/g and 407.4 mg/g. This work provides a new and reliable idea for the practical application of Hg(II) pollution removal.

Coir/glass hybrid fiber reinforced thermoset polymer composite laminates with room-temperature self-healing and shape memory functions

Natural fibers have a lot of potentials as renewable reinforcements for polymers. However, their lower load-carrying capacity compared with synthetic fibers made it a challenge to use them as polymer reinforcements. When a laminated composite beam is bent, the normal stress is the highest on the top and bottom layers and zero in the midplane due to the (non)linear distribution of normal strain. Even though the shear stress is the highest in the midplane, most polymers can tolerate the high shear stress. Therefore, hybrid composite laminates with strong synthetic glass fibers stacked over the core of weak natural coir fiber reinforcement have been designed. Even using a significant portion of coir fibers in the composites, the samples with hybrid fiber reinforcement showed almost similar mechanical properties compared with the samples with glass fiber reinforcement alone. Delamination and matrix crack induced by low velocity impact inside the composite panels were repeatedly healed at room temperature due to the self-healing capability of the diglycidyl 1,2-cyclohexanedicarboxylate (DCN) and polyethylenimine (PEI) polymer matrix. The healing efficiency was up to 99% for the first healing cycle and 72% for the fourth healing cycle. The composites also had good shape memory properties, with a shape fixity ratio up to 51% and a shape recovery ratio up to 93%, which were well maintained even after the several damage/healing cycles of the composites. This study opens new opportunities for applications of natural fibers in multifunctional load-bearing composites.

Surface modification strategy of boronic acids on glass substrates and its application for detecting glycated hemoglobin by liquid crystal-based sensors

Surface modification is a fundamental technique in the development of chemical sensors and biosensors. In this work, we established a strategy to incorporate boronic acids into the structure of polyethylenimine (PEI) through a multi-component reaction under microwave conditions. The presence of boronic acids on PEI was identified by NMR and IR spectroscopy. This borylated PEI polymer was coated on the glass substrate and its binding activity was tested by using 5-(diethylamino)-2-((methylimino)methyl)phenol (DAHMI) as a fluorescence tag. Moreover, the boronic acid-modified surface was applied to construct a liquid crystal (LC)-based sensor system for detecting glycated hemoglobin (HbA1C). The specific binding of HbA1C to boronic acid on glass surface lead to the reorientation of LCs, such that a dark-to-bright optical transition was observed under polarized light. Based on this mechanism, the limit of detection of the LC-based sensor for HbA1C was 100 μg/mL with good specificity. Our results demonstrated the applicability of the surface modification strategy of boronic acids on glass substrates for developing chemical sensors and biosensors.

Chemical doping of unsubstituted perylene diimide to create radical anions with enhanced stability and tunable photothermal conversion efficiency.

N-doping of perylene diimides (PDIs) to create stable radical anions is significant for harvesting photothermal energy due to their intensive absorption in the near-infrared (NIR) region and non-fluorescence. In this work, a facile and straightforward method has been developed to control the doping of perylene diimide to create radical anions using organic polymer polyethyleneimine (PEI) as a dopant. It was demonstrated that PEI is an effective polymer-reducing agent for the n-doping of PDI toward the controllable generation of radical anions. In addition to the doping process, PEI could suppress the self-assembly aggregation and improve the stability of PDI radical anions. Tunable NIR photothermal conversion efficiency (maximum 47.9%) was also obtained from the radical-anion-rich PDI-PEI composites. This research provides a new strategy to tune the doping level of unsubstituted semiconductor molecules for varying yields of radical anions, suppressing aggregation, improving stability, and obtaining the highest radical anion-based performance.

Carbon nanotubes – PEI – Formate dehydrogenase nano-biointerface for the specific bioelectrochemical reduction of CO2 to formate

Reduction of extensive CO2 emissions is one of the key challenges that our society must overcome in order to minimize the effects of global warming and climate change. In this respect, electrochemical reduction of CO2 via redox enzymes is believed to be a promising route to minimize global CO2 concentrations, as they specifically catalyze the selective CO2 reduction in a reversible way at low potentials and mild conditions. In this work, we describe the effective anchoring of the enzyme Desulfovibrio vulgaris Hildenborough FdhAB formate dehydrogenase using electrostatic interactions favoring oriented immobilization, to the surface of MWCNTs-modified low density graphite electrodes with subsequent protection of the enzyme with polyethyleneimine (PEI) polymer. The synergistic effect of MWCNTs and PEI has been studied. High catalytic current densities, up to −230 μA cm−2, as well as a high operational stability of 11 h of continuous long-term measurements, were achieved.