Immobilization of HSA on polyamidoamine-dendronized magnetic microspheres for application in direct chiral separation of racemates

A penicillinase-modified poly(N-isopropylacrylamide-co-acrylamide) smart hydrogel biosensor with superior recyclability for sensitive and colorimetric detection of penicillin G

Antibiotics are widely used for treating bacterial infections. However, excessive or improper use of antibiotics can pose a serious threat to human health and water environments, and thus, developing cost-effective, portable and effective strategies to analyze and detect antibiotics is highly desired. Herein, we reported a responsive photonic hydrogel (RPH)-based optical biosensor (PPNAH) with superior recyclability for sensitive and colorimetric determination of a typical β-lactam antibiotic penicillin G (PG) in water. This sensor was composed of poly(N-isopropylacrylamide-co-acrylamide) smart hydrogel with incorporated penicillinase and Fe3O4@SiO2 colloidal photonic crystals (CPCs). The sensor could translate PG concentration signals into changes in the diffraction wavelength and structural color of the hydrogel. It possessed high sensitivity and selectivity to PG and excellent detection performances for other two typical β-lactam antibiotics. Most importantly, due to the unique thermosensitivity of the poly(N-isopropylacrylamide) moieties in the hydrogel, the PG-responded PPNAH sensor could be facilely regenerated via a simple physical method at least fifty times while without compromising its response performance. Besides, our sensor was suitable for monitoring the PG-contaminated environmental water and displayed satisfactory detection performances. Such a sensor possessed obvious advantages of superior recyclability, highly chemical stability, low production cost, easy fabrication, wide range of visual detection, simple and intuitive operation for PG detection, and environmental-friendliness, which holds great potential in sensitive and colorimetric detection of the PG residues in polluted water.

Surface modified nanoparticles and their applications for enantioselective detection, analysis, and separation of various chiral compounds

The development of efficient enantioselective detection, analysis, and separation relies significantly on molecular interaction. In the scale of molecular interaction, nanomaterials have a significant influence on the performance of enantioselective recognitions. The use of nanomaterials for enantioselective recognition involved synthesizing new materials and immobilization techniques to produce various surface-modified nanoparticles that are either encapsulated or attached to surfaces, as well as layers and coatings. The combination of surface-modified nanomaterials and chiral selectors can improve enantioselective recognition. This review aims to offer engagement insights into the production and application of surface-modified nanomaterials to achieve sensitive and selective detection, better chiral analysis, and separation of numerous chiral compounds.

Enantioseparation/Recognition based on nano techniques/materials

Enantiomers show different behaviors in interaction with the chiral environment. Due to their identical chemical structure and their wide application in various industries, such as agriculture, medicine, pesticide, food, and so forth, their separation is of great importance. Today, the term "nano" is frequently encountered in all fields. Technology and measuring devices are moving towards miniaturization, and the usage of nanomaterials in all sectors is expanding substantially. Given that scientists have recently attempted to apply miniaturized techniques known as nano-liquid chromatography/capillary-liquid chromatography, which were originally accomplished in 1988, as well as the widespread usage of nanomaterials for chiral resolution (back in 1989), this comprehensive study was developed. Searching the terms "nano" and "enantiomer separation" on scientific websites such as Scopus, Google Scholar, and Web of Science yields articles that either use miniaturized instruments or apply nanomaterials as chiral selectors with a variety of chemical and electrochemical detection techniques, which are discussed in this article.

A chiral magnetic molybdenum disulfide nanocomposite for direct enantioseparation of RS-propranolol

We herein report a novel chiral magnetic molybdenum disulfide nanocomposite (MMoS₂/PNG-CD) with a high enantioselectivity and excellent thermosensitivity and magnetism. The prepared MMoS₂/PNG-CD shows temperature-dependent chiral discrimination and enantioselectivity toward a chiral drug RS-propranolol (RS-PPL), which is based on the molecular recognition ability of beta-cyclodextrin (β-CD) and the thermosensitivity of poly(N-isopropylacrylamide) (PNIPAM). The synthesized MMoS₂/PNG2-CD by using a monomer molar ratio of GMA to NIPAM of 2 : 1 demonstrates a high selectivity toward R-PPL over S-PPL due to the synergistic effect of the PNIPAM moieties and β-CD hosts. The thermo-induced volume phase transition (VPT) of the introduced PNIPAM moieties significantly affects the inclusion constants of the β-CD/R-PPL complex, and thus the loading and desorption of R-PPL on the MMoS₂/PNG2-CD. The enantioselectivity at temperatures below the lower critical solution temperature (LCST) of the PNG-β-CD grafting chains is much higher than that at temperatures above the LCST. As a result, the regeneration of the MMoS₂/PNG2-CD is easily achieved via simply changing the operating temperature. Moreover, the regenerated MMoS₂/PNG2-CD can be readily recovered from the RS-PPL solution under an external magnetic field for reuse. Such a multifunctional molybdenum disulfide nanocomposite with a high enantioselectivity and excellent thermosensitivity and regenerability is promising to serve as a high-performance nanoselector for direct resolution of various β-blocker drugs.

K A. Enantioselective Separation of Amino Acids Using Chiral Polystyrene Microspheres Synthesized by a Post-Polymer Modification Approach

The enantioselective separation of a racemic mixture of amino acids was achieved by chiral amino acid-modified polystyrene (PS) that was developed by a post-polymer modification approach. Styrene was polymerized using the reversible addition-fragmentation chain-transfer (RAFT) polymerization technique and further post-polymer modification was applied by Friedel-Crafts acylation reaction with chiral N-phthaloyl-l-leucine acid chloride to obtain the protected PS-l-Leu. The chiral PS (protected PS-l-Leu) was assembled into microspheres using a surfactant and was used for carrying out the enantioselective separation of amino acid racemic mixtures by enantioselective adsorption followed by a simple filtration process. Compared to as-precipitated chiral PS (protected PS-l-Leu) powder, the protected PS-l-Leu microspheres exhibited a better enantioselective separation efficiency (ee %). Furthermore, the protected PS-l-Leu was deprotected to obtain the amine-functionalized deprotected PS-l-Leu chiral PS, which was also assembled into microspheres and used for carrying out enantioselective separation. Deprotected PS-l-Leu-functionalized chiral PS microspheres could achieve up to 81.6 ee % for the enantioselective separation of a racemic mixture of leucine. This is one of the first reports of the synthesis of amino acid-modified chiral PS microspheres and their application to the simple filtration-based enantioselective separation of native amino acids from their racemic mixtures.

Chiral magnetic hybrid materials constructed from macromolecules and their chiral applications

Chirality is a fundamental and ubiquitous feature of living organisms in nature. Magnetic materials, in particular magnetic nanoparticles (MNPs), show some interesting properties such as large specific surface area, easy surface modification, magnetic responsivity and separation ability. Integrating MNPs with chirality in a single material will undoubtedly create a large number of advanced multi-functional materials. Despite the great advancements made in this area, there have been no review articles to summarize the relevant studies. The present work reviews the major progress recently made in constructing chiral magnetic hybrid materials (CMHMs) using macromolecules, which are classified based on the primary chiral macromolecular organic components, namely, biological polymers and synthetic polymers, and the applications of the resulting chiral hybrids in chiral research fields, including asymmetric catalysis, enzymatic resolution, chromatographic separation, enantioselective crystallization and enantioselective adsorption, are also summarized. The challenges and prospects of related research fields are proposed in the last section.

A novel hydrazide Schiff base self-assembled nanoprobe for selective detection of human serum albumin and its applications in renal disease surveillance

Human serum albumin (HSA) is considered as a biomarker for the early diagnosis of renal disease, therefore identifying and detecting HSA in biological fluids (especially urine) with an easy method is of great importance. Herein, we report a novel hydrazide Schiff base fluorescent probe N'-((7-(diethylamino)-2-oxo-2H-chromen-3-yl)methylene)pyrazine-2-carbohydrazide (NPC), which self-assembled into nanoparticles in aqueous solution. Based on disassembly-induced emission and the site-specific recognition mechanism, the binding of NPC with HSA resulted in a fluorescence "turn-on" response. Probe NPC exhibited superior selectivity and sensitivity toward HSA with a detection limit of 0.59 mg L-1 in PBS and 0.56 mg L-1 in the urine sample. The site-binding mechanism of NPC with HSA was explored by fluorescence quenching study, Job's plot analysis, HSA destruction, site marker displacement and molecular docking. Fluorescence imaging of HSA in MCF-7 cells was achieved by using a non-toxic NPC probe, suggesting that NPC could be applied to visualize the level of HSA in vivo. More importantly, further practical applications of probe NPC in human urine samples were achieved with satisfactory results by using a fluorometer or test paper, which could provide extensive application in clinical diagnosis.

A fluorometric assay of thrombin using magnetic nanoparticles and enzyme-free hybridization chain reaction

A fluorescence method based on functionalized magnetic nanoparticles (FMNPs) and hybridization chain reaction (HCR) is developed for the enzyme-free amplified determination of thrombin. In the proposed design, aptamer against thrombin was hybridized with the capture DNA-modified magnetic nanoparticles to yield the FMNPs. In the presence of thrombin, aptamers are released due to the specific and high-affinity binding between thrombin and its aptamer. The exposed capture DNA subsequently hybridized with the partial sequence of helper DNA, and the vacant sequence of helper DNA further hybridized with HCR products which is pre-formed by the alternate hybridization of single-stranded DNAs (H1 and H2). The immobilized HCR products were then labeled with YOYO-1 for fluorescence measurement. Fluorescence signal intensity of labeled YOYO-1 was measured at an emission wavelength of 519 nm (excitation under 488 nm) and used for calibration. By taking advantage of HCR amplification, this direct assay strategy showed a linear response in the 20- to 200-pM concentration range, and the limit of detection is 9.2 pM which is about 3-orders of magnitude lower than the serum thrombin concentration (10 nM) that triggers blood clotting. This developed method can efficiently differentiate the target protein from a protein matrix, and it is verified by determination of thrombin in spiked serum samples with recoveries in the range of 94.5-103.3%. Graphical abstract A fluorometry method for thrombin detection using magnetic nanoparticles and enzyme-free hybridization chain reaction.

Decorated single-enantiomer phosphoramide-based silica/magnetic nanocomposites for direct enantioseparation

The nano-composites Fe₃O₄@SiO₂@PTA(+) and Fe₃O₄@SiO₂@PTA(−) (PTA: phosphoric triamide) were prepared and used for the chiral separation of five racemic mixtures.

Enantioselective separation of RS-mandelic acid using β-cyclodextrin modified Fe3O4@SiO2/Au microspheres

β-Cyclodextrin functionalized magnetic microspheres were prepared via a self-assembly method and applied for the enantioselective absorption of enantiomers.

Attachment of enzymes to hydrophilic magnetic nanoparticles through DNA-directed immobilization with enhanced stability and catalytic activity

An efficient enzyme immobilization strategy based on DNA directed immobilization on hydrophilic polydopamine (PDA) modified magnetic nanoparticles was developed in this study.

Efficient immobilization of enzymes onto magnetic nanoparticles by DNA strand displacement: a stable and high-performance biocatalyst

An efficient enzyme immobilization strategy based on toehold-mediated DNA strand displacement on modified magnetic nanoparticles was developed in this study.

Thermo-responsive adsorption and separation of amino acid enantiomers using smart polymer-brush-modified magnetic nanoparticles

A novel type of multifunctional magnetic nanoparticle with highly chiral recognition capability, excellent thermo-sensitive adsorption and decomplexation properties toward amino acid enantiomers, and recyclability was developed in this study.

Microwave-assisted preparation of magnetic nanoparticles modified with graphene oxide for the extraction and analysis of phenolic compounds

Here in, magnetic nanoparticles combined with graphene oxide adsorbent were fabricated via a microwave-assisted synthesis method, and used in the solid-phase extraction of three phenolic compounds (phenol, 4-nitrophenol, and m-methylphenol) in environmental water samples. Various instrumental methods were employed to characterize the magnetic nanoparticles modified with graphene oxide. The influence of experimental parameters, such as desorption conditions, amount of adsorbent, extraction time, and pH, on the extraction efficiency was investigated. Owing to the high surface area and excellent adsorption capacity of the prepared material, satisfactory extraction was achieved. Under optimum conditions, a linear response was observed in the concentration range of 1.000-100.0 μg/L for phenol, 0.996-99.6 μg/L for 4-nitrophenol, and 0.975-97.5 μg/L for m-methylphenol, with correlation coefficients in the range of 0.9995-0.9997. The limit of detection (signal-to-noise ratio of 3) of the method varied between 0.5 and 0.8 μg/L. The relative standard deviations were <5.2%. The recovery percentages of the method were in the range of 89.1-104.3%. The results indicate that the graphene oxide-modified magnetic nanoparticles possess high adsorptive abilities toward phenolic compounds in environmental water samples.

Cationic β-cyclodextrin-modified hybrid magnetic microspheres as chiral selectors for selective chiral absorption of dansyl amino acids

Chiral selective magnetic microspheres based on imidazolium cationic-modified β-CD derivatives have been developed for direct enantioseparation of dansyl amino acids.