Dendrimers based sorbents: Promising materials for analytical extractions

Modified vermiculite as a sorbent phase for stir-bar sorptive extraction

BACKGROUND

The presence of emerging contaminants (ECs) is a cause of great concern nowadays, and they are present at very low concentrations in surface waters, requiring a preconcentration process for their reliable quantification. The technique of Stir-Bar Sorptive Extraction (SBSE) is a valuable tool for achieving this purpose, and different sorbents have been developed to produce the bars. In this sense, we propose the use of the clay mineral vermiculite (Vt), modified with alkylammonium salts, aiming the determination of the ECs: bisphenol A, diclofenac, ibuprofen and triclosan in surface water samples.

RESULTS

The best conditions for sorption and desorption were: 50.0 mL of sample at pH 4.0, under stirring at 600 rpm (120 min), being the desorption carried out under sonication for 20 min using 500 μL of methanol, and the analytes were determined using LC-DAD. A linear range from 0.50 to 2.50 μg L-1 or from 0.50 to 5.00 μg L-1 and R2 higher than 0.9480 were observed, and attractive real enrichment factors between 116 and 177 times, affording a LOD between 0.11 and 0.33 μg L-1. The method was applied to determine the four ECs in samples of tap, river, and lake waters, presenting recovery results between 42.0 and 128.0 %, and RSD from 0.4 to 19.6 %. The bars prepared using Vt presented good chemical and mechanical resistance, even modified using the alkylammonium salts, permitting them to be employed at least 30 times, without memory effects.

SIGNIFICANCE

The modified Vt, afforded a simple, low-cost, and attractive alternative to work as a sorbent phase for SBSE technique, presenting very appropriate analytical parameters, even employing LC-DAD. Although the sorbent was applied to a limited number of contaminants, it is probable that other analytes could be successfully determined. It is important to notice that this is the first study reported, employing modified Vt for SBSE application.

Fabrication of mixed-mode amphoteric β-cyclodextrin polymer for the simultaneous extraction of acidic and alkaline drugs

A multifunctional mixed-mode β-CD polymer adsorbent PNVCD-SIM containing amphoteric ions and multiple functional groups was prepared. Its physicochemical properties were characterized by scanning electron microscope (SEM), 1H nuclear magnetic resonance (1H NMR), 13C NMR, Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption-desorption test, elemental analysis (EA), and thermogravimetry and differential scanning calorimetry (TGA-DSC). The acidic indomethacin and alkaline promethazine were selected to evaluate the adsorption properties of PNVCD-SIM at different pH. Under optimal neutral pH conditions, the adsorption performance of PNVCD-SIM on acidic NSAIDs, alkaline phenothiazine, and neutral steroid hormone drugs was investigated. The results showed that PNVCD-SIM exhibited excellent diversified adsorption properties for acidic, alkaline, and neutral mixed drug components through the synergistic effects of β-CD inclusion, electrostatic interaction, hydrogen bond, π-π conjugation, and π-cation effect. The adsorption mechanism was consistent with the pseudo-second-order kinetic model and Langmuir isotherm model. Under the optimized conditions, a dispersive solid phase extraction method combined with high-performance liquid chromatography (dSPE-HPLC) using PNVCD-SIM as the adsorbent was established. The simultaneous extraction and detection of acidic-alkaline multi-component drugs in actual urine and lake water samples were successfully realized. This study provides new insight into the design and preparation of mixed-mode adsorption materials suitable for the rapid analysis and detection of multiple analytes.

Polyamidoamine with a hyper-branched structure grafted on modified magnetic graphene oxide for the trace separation of diclofenac and acetaminophen followed by high-performance liquid chromatography determination

Different generations of polyamidoamine dendrimers were synthesized on a focal core of magnetic graphene oxide modified with 3-aminopropyltriethoxysilane. After the characterization of synthesized dendrimers, its second generation was employed as a suitable sorbent for simultaneous separation/preconcentration of diclofenac and acetaminophen by a dispersive magnetic solid phase microextraction. The extracted analytes were then quantified by high-performance liquid chromatography with ultraviolet detection. Under optimized conditions, the limits of detection were 0.3 µg/L for diclofenac and 0.1 µg/L for acetaminophen. The intra-day relative standard deviations at 50 μg L-1 levels were 1.8% for diclofenac and 2.1% for acetaminophen, while the inter-day relative standard deviations were 3.6% and 4.5% for diclofenac and acetaminophen, respectively. The calibration graphs were linear in ranges of 1.0-500.0 µg/L and 0.5-600.0 µg/L for diclofenac and acetaminophen, respectively, with good coefficients of determination (r2 > 0.998). The method was successfully applied to the determination of diclofenac and acetaminophen in water, milk, and biological samples.

Progress in pre-treatment and extraction of organic and inorganic pollutants by layered double hydroxide for trace-level analysis

Continuous release of pollutants into the environment poses serious threats to environmental sustainability and human health. For trace-level analysis of pollutants, layered double hydroxide (LDH) is an attractive option to impart enhanced sorption capability and sensitivity toward pollutants because of its unique layered structure, tunable interior architecture, high anion-exchange capacities, and high porosity (e.g., Zn/Cr LDH/DABCO-IL, Ni/Al LDH, CS-Ni/Fe LDH, SDS-Fe₃O₄@SiO₂@Mg-Al LDH, Boeh/Mg/Al LDH/pC, and Fe@NiAl LDH). In concert with the well-defined analytical methodologies (e.g., HPLC and GC), the LDH materials can be employed to detect trace-level targets (e.g., as low as ∼ 20 fg/L for phenols) in aqueous environments. This review highlights LDH as a promising material for pre-treatment of a variety of organic and inorganic target pollutants in complex real matrices. Challenges and future requirements for research into LDH-based analytical methods are also discussed.

Aramid-wrapped CNT hybrid sol–gel sorbent for polycyclic aromatic hydrocarbons

This work describes the preparation of an analytical microextraction sorbent using a simple and versatile sol–gel hybrid composite, i.e., aramid oligomers wrapping multi-walled carbon nanotubes (CNTs) covalently bonded to a porous silica network.

Electrochemical and Electrochemiluminescence Dendrimer-based Nanostructured Immunosensors for Tumor Marker Detection: A Review

The usage of dendrimers or cascade molecules in the biomedical area has recently attracted much attention worldwide. Furthermore, dendrimers are interesting in clinical and pre-clinical applications due to their unique characteristics. Cancer is one of the most widespread challenges and important diseases, which has the highest mortality rate. In this review, the recent advances and developments (from 2009 up to 2019) in the field of electrochemical and electroluminescence immunosensors for detection of the cancer markers are presented. Moreover, this review covers the basic fabrication principles and types of electrochemical and electrochemiluminescence dendrimer-based immunosensors. In this review, we have categorized the current dendrimer based-electrochemical/ electroluminescence immunosensors into five groups: dendrimer/ magnetic particles, dendrimer/ferrocene, dendrimer/metal nanoparticles, thiol-containing dendrimer, and dendrimer/quantum dots based-immunosensors.

Engineered Fluorescent Carbon Dots and G4-G6 PAMAM Dendrimer Nanohybrids for Bioimaging and Gene Delivery

Carbon dots (CDs) and G4-G6 (polyamidoamine)PAMAM-NH2 dendrimers were self-assembled to produce CDs@PAMAM nanohybrids for transfection and bioimaging purposes. CDs were synthesized by the hydrothermal method, using ascorbic acid as a starting precursor and characterized by transmission electron microscopy, UV-Vis, and fluorescence (in solution and solid-state) techniques. CDs were electrostatically combined with PAMAM dendrimers at room temperature, and the UV-Vis, fluorescence, and NMR spectroscopies were used to confirm the self-assembly. When compared to pristine CDs, nanohybrids were more photostable, resisting high acidic and basic pH. Moreover, they were considerably internalized by cells, as assessed by flow cytometry and fluorescence microscopy, and, when excited, displayed multi-color emission easily quantified and visualized. These nanoscale hybrids, coined hybridplexes, can condense pDNA and transfecting cells successfully, particularly the G5 CDs@PAMAM nanohybrids. In summary, CDs prepared in mild and smooth lab conditions, showing good optical properties, were used to prepare elegantly CDs@PAMAM nanohybrids with promising biomedical applications.

Nanoparticles Based Extraction Strategies for Accurate and Sensitive Determination of Different Pesticides

Sample preparation methods have become indispensable steps in analytical measurements not only to lower the detection limit but also to eliminate the matrix effect although more sophisticated instruments are being commonly used in routine analyses. Solid phase extraction (SPE) is one of the main extraction/preconcentration methods used to extract and purify target analytes along with simple and rapid procedures but some limitations have led to seek for an easy, sensitive and fast extraction methods with analyte-selective sorbents. Nanoparticles with different modifications have been used as spotlight to enhance extraction efficiency of target pesticides from complicated matrices. Carbon-based, metal and metal oxides, silica and polymer-based nanoparticles have been explored as promising sorbents for pesticide extraction. In this review, different types of nanoparticles used in the preconcentration of pesticides in various samples are outlined and examined. Latest studies in the literature are discussed in terms of their instrumental detection, sample matrix and limit of detection values. Novel strategies and future directions of nanoparticles used in the extraction and preconcentration of pesticides are also discussed.

Miniaturized analytical methods for determination of environmental contaminants of emerging concern - A review

The determination of contaminants of emerging concern (CECs) in environmental samples has become a challenging and critical issue. The present work focuses on miniaturized analytical strategies reported in the literature for the determination of CECs. The first part of the review provides brief overview of CECs whose monitoring in environmental samples is of particular significance, namely personal care products, pharmaceuticals, endocrine disruptors, UV-filters, newly registered pesticides, illicit drugs, disinfection by-products, surfactants, high technology rare earth elements, and engineered nanomaterials. Besides, an overview of downsized sample preparation approaches reported in the literature for the determination of CECs in environmental samples is provided. Particularly, analytical methodologies involving microextraction approaches used for the enrichment of CECs are discussed. Both solid phase- and liquid phase-based microextraction techniques are highlighted devoting special attention to recently reported approaches. Special emphasis is placed on newly developed materials used for extraction purposes in microextraction techniques. In addition, recent contributions involving miniaturized analytical flow techniques for the determination of CECs are discussed. Besides, the strengths, weaknesses, opportunities and threats of point of need and portable devices have been identified and critically compared with chromatographic methods coupled to mass chromatography. Finally, challenging aspects regarding miniaturized analytical methods for determination of CECs are critically discussed.

Novel materials for dispersive (micro) solid-phase extraction of polycyclic aromatic hydrocarbons in environmental water samples: A review

Polycyclic aromatic hydrocarbons are hazardous environmental pollutants that possess mutagenic and carcinogenic properties. Generally, the concentrations of PAHs in environmental water samples are very low, and it is challenging to detect such levels directly by the analytical instrumentation. Thus, the extraction of PAHs using suitable extraction methodology is required for sample cleanup and analyte enrichment. Dispersive solid-phase extraction has several advantages over conventional approaches for the extraction of PAHs from environmental water samples. In this article, we critically evaluate the role of different nano and micro sorbent materials employed in the extraction of PAHs. Carbon-based nanomaterials, metal-organic frameworks, polymeric nanocomposites, ionic-liquid based composites, and silica-based materials are explicitly covered. This review also provides insight on functional components of all types of sorbents and their way of interaction with PAHs. The factors affecting the dispersive (micro) solid phase extraction of PAHs such as the design of the sorbent, the ratio of functional material to magnetic core, sample volume, amount of sorbent, extraction and desorption times, desorption solvent and its volume, salt addition, and sample pH are critically appraised. Finally, a brief account on the accomplishments, limitations, and challenges associated with such methods is provided.

An update on the use of molecular modeling in dendrimers design for biomedical applications: are we using its full potential?

INTRODUCTION

Dendrimers are well-defined hyperbranched polymers built from a variety of different monomers and with tuneable properties that make them suitable for different biomedical applications. Their three-dimensional (3D) structure cannot be usually determined experimentally due to their inherent nature of repeating patterns in the topology, failure to crystalize, and/or high flexibility. Therefore, their conformations and interactions at the atomistic level can be studied only by using computational chemistry methods, including molecular dynamics, Monte Carlo simulations, and molecular docking.

AREAS COVERED

In this review, the methods that could be utilized in computer-aided dendrimer design are considered, providing a list of approaches to generate initial 3D coordinates and selected examples of applications of relevant molecular modeling methods.

EXPERT OPINION

Computational chemistry provides an invaluable set of tools to study dendrimers and their interactions with drugs and biological targets. There is a gap in the software development that is dedicated to study of these highly variable and complex systems that could be overcome by the integration of already established approaches for topology generation and open source molecular modeling libraries. Furthermore, it would be highly beneficial to collate already built 3D models of various dendrimers with corresponding relevant experimental data.

Magnetic hyperbranched molecularly imprinted polymers for selective enrichment and determination of zearalenone in wheat proceeded by HPLC-DAD analysis

A novel magnetic surface molecular imprinted polymers with 2, 4, 6-trisacrylamido-3, 5-triazine (TAT) as a functional monomer was successfully synthesized and used for the enrichment and determination of zearalenone. The molecular imprinting is reported herein at first time for application of zearalenone in wheat. The magnetic imprinted materials possessed excellent magnetism and uniform appearance, which were characterized by fourier transform infared spectroscopy and transmission electron microscope. The results proved the magnetic molecular imprinted polymers was successfully prepared. The magnetic molecular imprinted polymers exhibited satisfactory sensitivity, stability and potential reusability. The binding affinity was investigated by selectivity experiment, which possessed high selectivity. To obtain the optimal application conditions, the amount of adsorption, extraction time, elution solvent and time were optimized. The limited detection of zearalenone was 0.55 ng g^-1 and the recoveries of zearalenone were 92.1-96.0%. The relative standard deviation was lower than 5.4%. This indicated that a simple, efficient and low-cost method was established and successfully applied in spiked wheat sample.

Cyclodextrin-based sorbents for solid phase extraction

Cyclodestrins (CDs) are cyclic oligosaccharides well-known for their ability to form host-guest inclusion complexes with properly sized compounds. They have been used for decades as chiral selectors as well as drug delivery systems within the frameworks of separation science and pharmaceutical science. More recently, their use has been extended to the field of extractive science under the stimulus of additional advantageous characteristics, such as low-price, negligible environmental impact, non-toxicity, as arising from the fact that natural CDs are starch degradation products. To abate their solubility in water and generate novel sorbents for solid phase extraction, the following approaches have been employed: (i) immobilization onto inert materials (silica, attapulgite, etc.); (ii) immobilization onto nanomaterials (magnetic nanoparticles, titanium oxide, carbon nanotubes, graphene oxide, etc.); (iii) polymerisation with specific cross-linkers to form the so-called CD-based nanosponges. Particularly promising are these last ones for their selectivity, mesoporous structure, insolubility in aqueous media and good dispersibility. This review offers a concise overview on the state of art and future prospects of CDs in this important sector of the analytical chemistry, offering a critical perspective of the most significant applications.