Amine-terminated dendritic polymers as a multifunctional chelating agent for heavy metal ion removals

Performance and mechanism of amphiphilic polymeric chelator for enhanced removal of high concentrations of Cu(II) from wastewater

An amphiphilic polymeric chelator (APC16-g-SX) grafted with sodium xanthate (SX) groups was successfully prepared for the efficient removal of high concentrations of Cu(II) from wastewater. The ordinary polymeric chelator (PAM-g-SX) based on linear polyacrylamide (PAM) was also prepared for comparative studies. The polymeric chelators were characterized by Fourier transform infrared spectroscopy (FT-IR), solid-state nuclear magnetic resonance (13C-NMR), gel permeation chromatography (GPC), elemental analyzer, and scanning electron microscope (SEM). The chelating performance of these polymeric chelators was investigated, and the mechanism of APC16-g-SX for enhanced removal of Cu(II) from wastewater was proposed based on fluorescence spectroscopy, cryo-scanning electron microscope (Cryo-SEM), energy-dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS) tests. The results show that as the initial Cu(II) concentration in the wastewater increases, APC16-g-SX shows more excellent chelating performance than ordinary PAM-g-SX. For the wastewater with an initial Cu(II) concentration of 200 mg/L, the removal rate of Cu(II) was 99.82% and 89.34% for both 500 mg/L APC16-g-SX and PAM-g-SX, respectively. The pH of the system has a very great influence on the chelating performance of the polymeric chelators, and the increase in pH of the system helps to improve the chelating performance. The results of EDS and XPS tests also show that N, O, and S atoms in APC16-g-SX were involved in the chelation of Cu(II). The mechanism of enhanced removal of Cu(II) by APC16-g-SX can be attributed to the spatial network structure constructed by the self-association of hydrophobic groups that enhances the utilization of chelation sites.

Upconversion luminescence nanosensor for detection of Fe3+ and phosphate ion based on the inner-filter effect

In this work, an upconversion luminescence (UCL) nanosensor for fast detection of ferric ion (Fe3+) and phosphate ion (Pi) is developed based on the inner-filter effect (IFE) between NaYF4:Yb/Er upconversion nanoparticles (UCNPs) and Fe3+-hypocrellin B (HB) complex. Fe3+-HB complex has strong absorption band (450-650 nm), which overlaps with the green emission peak of UCNPs at 545 nm. By adding Fe3+ and Pi, the UCNPs-HB system produces the red-shift change of absorption spectrum, which leads to the "on-off-on" process of IFE. So, with the specific recognition ability of HB for Fe3+ and the competitive complexation of Pi for Fe3+, the proposed nanosensor utilizes the UCL change to achieve the detection of the targets. For the detections of Fe3+, the linear range is 10-600 μM with a limit of detection (LOD) of 2.62 μM, and for Pi, the linear range is 5-100 μM with a LOD of 1.25 μM. The results for selectivity, precision, and recovery test are also satisfactory. Furthermore, the real sample detection shows that the proposed nanaosensor has a great potential in environmental and biological systems. An upconversion luminescence (UCL) nanosensor based on the inner-filter effect (IFE) between upconversion nanoparticles (UCNPs) and Fe3+-hypocrellin B (HB) complex for the detection of Fe3+ and phosphate ion has been proposed, which is promising to be a convenient and sensitive assay for monitoring Fe3+ and phosphate ion in different environments and biological systems.

Functionalized Amphiphilic Block Copolymers and Complex Emulsions for Selective Sensing of Dissolved Metals at Liquid-Liquid Interfaces

Increasing contamination in potable water supplies necessitates the development of sensing methods that provide the speed and selectivity necessary for safety. One promising method relies on recognition and detection at the liquid-liquid interface of dynamic complex emulsions. These all-liquid materials transduce changes in interfacial tensions into optical signals via the coupling of their chemical, physical, and optical properties. Thus, to introduce selectivity, it is necessary to modify the liquid-liquid interface with an interfacially stable and selective recognition unit. To this end, we report the synthesis and characterization of amphiphilic block copolymers modified with metal chelators to selectively measure the concentrations of dissolved metal ions. We find that significant reduction in interfacial tensions arises upon quantitative addition of metal ions with high affinity toward functionalized chelators. Furthermore, measurements from UV-vis spectroscopy reveal that complexation of the block copolymers with metal ions leads to an increase in surface excess and surfactant effectiveness. We also demonstrate selective detection of iron(III) cations (Fe3+) on the μM levels even through interference from other mono-, di-, or trivalent cations in complex matrices of synthetic groundwater. Our results provide a unique platform that couples selective recognition and modulation of interfacial behaviors and demonstrates a step forward in the development of the multiplexed sensing device needed to deconvolute the complicated array of contaminants that comprise real-world environmental samples.

Hybrid electrospun scaffolds based on polylactic acid/ PAMAM dendrimer/gemini surfactant for enhancement of synergistic antibacterial ability for biomedical application

Hybrid electrospun scaffolds based on poly (L-lactic acid) (PLLA) / poly (amidoamine) (PAMAM-G2) dendrimer / gemini surfactant were fabricated for the enhancement of synergistic antibacterial activities. The second generation of poly (amidoamine) (PAMAM-G2) and cationic gemini surfactant were utilized to functionalize the optimum electrospun scaffolds. The gelatination process was utilized to improve the wettability of PLLA scaffolds to extend cell attachment and cell proliferation. PLLA nanofibrous scaffolds were characterized by energy dispersion X-ray (EDX), Scanning electron microscopy (SEM) images, mechanical properties, water contact angle, Fourier transform infrared (FTIR) spectroscopy, zeta potential and antibacterial assessment. In vitro cell biocompatibility was evaluated by MTT assay and morphology of PC-12 cells cultured on hybrid nanofibrous scaffolds and gelatinized ones. The results indicated that the optimum scaffolds could successfully modify the characteristics of PLLA scaffolds leading to much more appropriate physical and chemical properties. In addition, gelatinized nanofibrous scaffolds reveal more wettability enhancing cell attachment and proliferation. Furthermore, using poly (amidoamine) (PAMAM-G2) and gemini surfactant reveals synergetic antibacterial activity due to the competition between both cationic groups of PAMAM and gemini surfactant. Finally, improved cell adhesion and cell viability on modified scaffolds were confirmed. These favorable properties give a chance for these scaffolds to be used in a wide variety of biomedical applications.

Effect of Cavity Cleanser With Long-Term Antibacterial and Anti-Proteolytic Activities on Resin-Dentin Bond Stability

Objective

Secondary caries caused by oral microbiome dysbiosis and hybrid layer degradation are two important contributors to the poor resin-dentin bond durability. Cavity cleansers with long-term antimicrobial and anti-proteolytic activities are in demand for eliminating bacteria-induced secondary caries and preventing hybrid layers from degradation. The objectives of the present study were to examine the long-term antimicrobial effect and anti-proteolytic potential of poly(amidoamine) dendrimers with amino terminal groups (PAMAM-NH₂) cavity cleanser.

Methods

Adsorption tests by attenuated total reflectance-infrared (ATR-IR) spectroscopy and confocal laser scanning microscopy (CLSM) were first performed to evaluate whether the PAMAM-NH₂ cavity cleanser had binding capacity to dentin surface to fulfill its relatively long-term antimicrobial and anti-proteolytic effects. For antibacterial testing, Streptococcus mutans, Actinomyces naeslundii, and Enterococcus faecalis were grown on dentin surfaces, prior to the application of cavity cleanser. Colony-forming unit (CFU) counts and live/dead bacterial staining were performed to assess antibacterial effects. Gelatinolytic activity within the hybrid layers was directly detected by in situ zymography. Adhesive permeability of bonded interface and microtensile bond strength were employed to assess whether the PAMAM-NH₂ cavity cleanser adversely affected resin-dentin bonding. Finally, the cytotoxicity of PAMAM-NH₂ was evaluated by the Cell Counting Kit-8 (CCK-8) assay.

Results

Adsorption tests demonstrated that the binding capacity of PAMAM-NH₂ on dentin surface was much stronger than that of 2% chlorhexidine (CHX) because its binding was strong enough to resist phosphate-buffered saline (PBS) washing. Antibacterial testing indicated that PAMAM-NH₂ significantly inhibited bacteria grown on the dentin discs as compared with the control group (p < 0.05), which was comparable with the antibacterial activity of 2% CHX (p > 0.05). Hybrid layers conditioned with PAMAM-NH₂ showed significant decrease in gelatin activity as compared with the control group. Furthermore, PAMAM-NH₂ pretreatment did not adversely affect resin-dentin bonding because it did not decrease adhesive permeability and microtensile strength. CCK-8 assay showed that PAMAM-NH₂ had low cytotoxicity on human dental pulp cells (HDPCs) and L929.

Conclusions

PAMAM-NH₂ cavity cleanser developed in this study could provide simultaneous long-term antimicrobial and anti-proteolytic activities for eliminating secondary caries that result from a dysbiosis in the oral microbiome and for preventing hybrid layers from degradation due to its good binding capacity to dentin collagen matrix, which are crucial for the maintenance of resin-dentin bond durability.

Fabrication and Characterization of Lignin/Dendrimer Electrospun Blended Fiber Mats

Blending lignin as the second most abundant polymer in Nature with nanostructured compounds such as dendritic polymers can not only add value to lignin, but also increase its application in various fields. In this study, softwood Kraft lignin/polyamidoamine dendritic polymer (PAMAM) blends were fabricated by the solution electrospinning to produce bead-free nanofiber mats for the first time. The mats were characterized through scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, zeta potential, and thermogravimetry analyses. The chemical intermolecular interactions between the lignin functional groups and abundant amino groups in the PAMAM were verified by FTIR and viscosity measurements. These interactions proved to enhance the mechanical and thermal characteristics of the lignin/PAMAM mats, suggesting their potential applications e.g. in membranes, filtration, controlled release drug delivery, among others.

New route for synthesis of 2-(2,2-dimethoxyethyl)-1,2,3,4,5,6-hexahydro-1,5-methanoazocino[4,3-b]indole and DFT investigation

Development of efficient sequences for the synthesis of the title compound (2-(2,2-dimethoxyethyl)-1,2,3,4,5,6-hexahydro-1,5-methanoazocino[4,3-b]indole) (7) was described. The title compound was synthesized through several steps starting from phenylhydrazine hydrochloride and dimethyl (R)-2-(3-oxocyclohexyl)malonate. In this route, all synthesized compounds were observed by spectroscopic tools (FT-IR, NMR): Methyl-2-(2,3,4,9-1H-carbazol-2-yl)acetate (3), 2-(2,3,4,9-tetrahydro-1H-carbazol-2-yl)acetic acid (4), N-(2,2-dimethoxyethyl)-2-(2,3,4,9-tetrahydro-1H-carbazol-2-yl)acetamide (5), 2-(2,2-dimethoxyethyl)-1,2,4,5,6,7-hexahydro-3H-1,5-methanoazocino[4,3-b]indol-3-one (6), 2-(2,2-dimethoxyethyl)-2,3,4,5,6,7-hexahydro-1H-1,5-methanoazocino[4,3-b]indole (7). The central step in these syntheses is the dehydrogenative reaction, which constructs the tetracyclic ring system from a much simpler tetracyclic precursor. The six-stable conformers of the compound (7) were used for further calculations such as FT-IR, NMR, NLO, and FMO analyses, performed at the B3LYP/6-311++G(d,p) level. This work revealed that (7) can be a good material to use in the non-linear optical material because its β tensor is greater ten times than that of the urea.

One-pot synthesis of multi-functional and environmental friendly tannic acid polymer with Fe3+ and formaldehyde as double crosslinking agents for selective removal of cation pollutants

A novel multi-functional and environmental friendly tannic acid polymer (Fe³⁺-TA-HCHO) with Fe³⁺ and formaldehyde as double crosslinking agents together with cysteine as heteroatom source was prepared by a one-pot hydrothermal method. Characterization with transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), and elemental analysis demonstrated that the Fe³⁺-TA-HCHO possessed uniform structure and particle size as well as plentiful functional groups. The resulted Fe³⁺-TA-HCHO material as a adsorbent to remove methylene blue, sunset yellow, Pb²⁺, Hg²⁺, and AsO₃^3- from water. The results suggested that Fe³⁺-TA-HCHO polymer (pHpzc is 2.33) showed different adsorption properties for anionic pollutants (sunset yellow and AsO₃^3-) and cationic pollutants (methylene blue, Pb²⁺, and Hg²⁺). The material exhibited remarkable selectivity for adsorption and separation of pollutants. The maximum adsorption capacities calculated from Langmuir model for methylene blue, Pb²⁺, and Hg²⁺ were 154.32, 819.67, and 699.30 mg g^-1, respectively. This is the first time that tannic acid polymer is synthesized by double crosslinking method, which not only developed a promising adsorbent for selective removal of cation pollutants, but also opened up a new avenue for synthesis and application of tannic acid polymer.