Addition-fragmentation Chain Transfer Polymerization Method Research Articles

Design and synthesis of thermosensitive target segment resin with precisely controlled distance between immobilization sites for immobilization of penicillin G acylase

PurposeTo save the economic cost and improve the performance of enterprises, this study aims to synthesize high performance immobilized penicillin G acylase (PGA) carriers with fast reaction speed, high recovery rate of enzyme activity and good reusability through corresponding theoretical guidance and experimental exploration.Design methodology approachA diblock resin was synthesized by reversible addition-fragmentation chain transfer polymerization method using N, N-diethylacrylamide (DEA) and β-hydroxyethyl methacrylate (HEMA) as functional monomers poly(N, N-diethylacrylamide)-b-poly(β-hydroxyethyl methacrylate) (PDEA-b-PHEMA) was obtained, and the effect of the ratio of DEA and HEMA on the activity of PGA was investigated, and the appropriate block ratio of DEA and HEMA was obtained. After that, the competitive rate of HEMA and glycidyl methacrylate (GMA) under the carrier preparation conditions was investigated. Based on the above work, a thermosensitive resin carrier PDEA-b-PHEMA-b-P(HEMA-co-GMA) with different target distances was synthesized, and the chemical structures and molecular weight of copolymers were investigated by hydrogen NMR (1H NMR).FindingsThe lower critical solution temperature of the resin support decreases with the increase of the monomer HEMA in the random copolymerization; the catalytic performance study indicated that the response rate of the immobilized PGA is fast, and the recovery rate of the enzyme activity of the immobilized PGA varies with the distance between the targets. When the molar ratio of HEMA to GMA in the resin block is 8.15:1 [i.e. resin PDEA100-b-PHEMA10-b-P(HEMA65-co-GMA8)], the activity recovery rate of immobilized PGA can reach 50.51%, which was 15.49% higher than that of pure GMA immobilized PGA.Originality valueThis contribution provides a novel carrier for immobilizing PGA. Under the optimal molar ratio, the enzyme activity recovery could be up to 50.51%, which was 15.49% higher than that of PGA immobilized on the carrier with nonregulated distance between two immobilization sites.

Highly Efficient Selective Extraction of Chlorpyrifos Residues from Apples by Magnetic Microporous Molecularly Imprinted Polymer Prepared by Reversible Addition–Fragmentation Chain Transfer Surface Polymerization

Chlorpyrifos, as a moderate toxic organophosphorus pesticide, is prone to lingering in the environment and cannot be monitored easily. In this study, a magnetic, microporous, molecularly imprinted polymer was synthesized by using the reversible addition-fragmentation chain transfer polymerization method. The synthesized materials were properly characterized in terms of morphology, selectivity, and sorption capacity and used as sorbents for magnetic solid phase extraction for the selective determination of chlorpyrifos in apple samples. Results showed that the magnetic microporous molecularly imprinted materials were rough and porous spheres at an average size of 5 nm. The materials were highly selective toward chlorpyrifos with a superior sorption capacity of 167.99 mg·g-1 and were resistant to the interference of competitive pollutants. After optimization, the recoveries of chlorpyrifos reached 96.2-106.5%, and the detection limit was 0.028 μg·kg-1 by HPLC. Based on these analytical validation results, the developed method could be effective at determining chlorpyrifos in apples.

Gold Nanoparticle Embedded Stimuli-Responsive Functional Glycopolymer: A Potential Material for Synergistic Chemo-Photodynamic Therapy of Cancer Cells.

Photodynamic therapy has emerged as a noninvasive treatment modality for several types of cancers. However, conventional hydrophobic photosensitizers (PS) suffer from low water solubility and poor tumor-targeting ability. Therefore, PS modified with glycopolymers can offer adequate water solubility, biocompatibility, and tumor-targeting ability due to the presence of multiple sugar units. In this study, a well-defined block copolymer poly(3-O-methacryloyl-d-glucopyranose)-b-poly(2-(4-formylbenzoyloxy)ethylmethacrylate) (PMAG-b-PFBEMA) containing pendant glucose and aldehyde units is synthesized via reversible addition-fragmentation chain transfer polymerization method. A water-soluble PS (toluidine blue O; TBO) and a potent anticancer drug, Doxorubicin (Dox) are introduced to the polymer backbone via acid-labile Schiff-base reaction (PMAG-b-PFBEMA_TBO_Dox). The PMAG-b-PFBEMA_TBO_Dox is then anchored on the surface of gold nanoparticles (AuNPs)via electrostatic interaction. This hybrid system exhibits excellent reactive oxygen species (ROS) generating ability under exposure of 630nm light-emitting diode along with triggered release of Dox under the acidic pH of tumor cells. The in vitro cytotoxicity study on human breast cancer cell line, MDA MB 231, for this hybrid system shows promising results due to the synergistic effect of ROS and Dox released. Thus, this glycopolymer-based dual (chemo-photodynamic) therapy model can work as potential material for future therapeutics.

Fluorination Increases Hydrophobicity at the Macroscopic Level but not at the Microscopic Level

Hydrophobic interactions have been studied before in detail based on hydrophobic polymers, such as polystyrene (PS). Because fluorinated materials have relatively low surface energy, they often show both oleophobicity and hydrophobicity at the macroscopic level. However, it remains unknown how fluorination of hydrophobic polymer influences hydrophobicity at the microscopic level. We synthesized PS and fluorine-substituted PS (FPS) by employing the reversible addition-fragmentation chain transfer polymerization method. Contact angle measurements confirmed that FPS is more hydrophobic than PS at the macroscopic level due to the introduction of fluorine. However, single molecule force spectroscopy experiments showed that the forces required to unfold the PS and FPS nanoparticles in water are indistinguishable, indicating that the strength of the hydrophobic effect that drives the self-assembly of PS and FPS nanoparticles is the same at the microscopic level. The divergence of hydrophobic effect at the macroscopic and microscopic level may hint different underlying mechanisms: the hydrophobicity is dominated by the solvent hydration at the microscopic level and the surface-associated interaction at the macroscopic level.

Ultralow Crosslinked Microgel Brings Ultrahigh Catalytic Efficiency.

Microgel nanoreactors maintain the stability of metallic nanoparticles and regulate their catalytic activity. However, limited by the synthetic method, the recycling ability and long-lasting stability of microgel nanoreactors are challenged. Herein, a brand-new nanoparticle carrier, ultralow crosslinked poly(N-isopropylacrylamide-b-methacrylic acid) (P(NIPAm-b-MAA)) microgel, is synthesized based on the reversible addition-fragmentation chain transfer polymerization method and the self-crosslinking mechanism of PNIPAm. This carrier enables the easy preparation, low cost, long-lasting stability, and high catalytic efficiency of nanoreactors. As far as it is known, the catalytic reduction rates of several dye models used in this work are the highest ones in similar systems. In addition, the presence of the MAA block leads to the agglomeration and dispersion of the microgels under different pH conditions, thus realizing rapid recycling of the nanoreactors. This novel carrier has great potential for a wide range of applications in catalysis.

Smart pH responsive drug delivery system based on poly(HEMA-co-DMAEMA) nanohydrogel

The advent of smart nanohydrogel has revealed new opportunities for scientists to develop the most efficient anti-cancer vehicles with safe and biocompatible profile. In this experiment, using reversible addition-fragmentation chain transfer polymerization method as a novel, safe and smart pH responsive formulation of poly (hydroxyethyl methacrylate-co-N,N-dimethylaminoethyl methacrylate) and poly (ethylene glycol)-diacrylate as cross-linker were synthesized. The synthesized structure was confirmed by Fourier-transform infrared spectroscopy and proton nuclear magnetic resonance methods. The pH responsive behavior of the synthesized particles was checked by size measurement in two different pH values (5.5 and 7.4) by dynamic light scattering and transmission electron microscopy. The prepared structure had nanometer sizes of 180 in medium with pH of 7.4, when it encountered acidic medium (e.g. pH 5.5), the particles swelled to about 400 nm. The efficiency of the prepared pH responsive nanohydrogels was tested as a drug delivery system. An anti-cancer drug, doxorubicin successfully interacted with this material. The release profiles of nanoparticles carrying drug molecules were checked in two different simulated pH of healthy organs (7.4) and tumor site (5.5). Despite lower release in pH of 7.4 (∼20%), an increased drug release of 80% was obtained in pH of 5.5. The in vitro toxicity assay, apoptosis evaluation and uptake experiments were performed on breast cancer cell line (MCF-7), which showed a time dependency cellular entrance, an enhanced cytotoxicity and apoptosis induction by the doxorubicin loaded nanoparticles. Hemolysis assays confirmed the safety and hemocompatibility of the developed nanohydrogel. The suitable size (<200 nm), pH responsive behavior, anti-proliferative activity and apoptosis induction in cancer cells and hemocompatibility were the noticeable features of the developed doxorubicin adsorbed nanoparticle, which introduced this formulation as an ideal vehicle in anti-cancer drug delivery.

Light-triggered pH/thermal multisensitive polyelectrolyte/ITO glass hybrid electrode

Surfaces with stimuli-responsive properties have shown prominent applications in bioengineering, controlled drug release and biosensors in recent years. In this work, we report a surface-initiated reversible addition–fragmentation chain transfer polymerization method to graft azobenzene-containing diblock copolymer (azo-BCP) brushes onto an Indium Tin Oxide (ITO) glass surface. In this method, a sequential azo block serves as the outer layer that controls the closure or opening of the brushes, and the second block (PDMAEMA) acts as the inner layer that switches between swollen and collapsed chain states in response to different pH values and temperatures. Upon exposure to UV light, the ITO surface became more hydrophilic (>10° change of contact angles), and its friction coefficient (0.5–0.9) increased; this suggests a loose aggregation of the azo block. Additionally, the ion conductivity of the ITO surface can be influenced by the aggregation state of the azo-BCP brushes, thus leading to the transportation of light-triggered ions under various pH values and temperatures. This work provides a deep understanding of the surface properties of a sensitive hybrid material upon various stimuli for electrode purpose, thereby paving the way for the development of bioengineering and environmental sensory applications.

Development of alanine aminotransferase reactor based on polymer@Fe3O4 nanoparticles for enzyme inhibitors screening by chiral ligand exchange capillary electrophoresis

Alanine aminotransferase (ALT) plays significant role in biological and clinical research. In this study, a unique ALT enzyme reactor based on multifunctional polymer@magnetic nanoparticles has been constructed for the first time and the enzymolysis efficiency has been evaluated by chiral ligand exchange capillary electrophoresis technique. Poly(N-acryloxysuccinimide) has been synthesized by reversible addition-fragmentation chain transfer polymerization method and immobilized on the magnetic nanoparticles via the succinimide group in the polymer. Interestingly, the enzyme also could easily react with the succinimide group, which enables of ALT covalent bonding onto the polymer. The enzyme amount immobilized and the immobilization time have been investigated. Comparing with free ALT in solution (Vmax of free enzyme = 0.6 mM min−1), the resultant enzyme reactor has exhibited good reusability and stability, and displayed about five times enhanced enzymolysis efficiency with L-alanine as the substrate (Vmax of enzyme reactor = 3.4 mM min−1). Furthermore, the prepared enzyme reactor has been applied in ALT inhibitors screening. The enzyme reactors based on the multifunctional polymer@magnetic nanoparticles have depicted great potential in anti-liver drugs development, liver diseases study and ALT related biological process inspect.

Synthesis of dual-sensitive nanocrystalline cellulose-grafted block copolymers of N-isopropylacrylamide and acrylic acid by reversible addition-fragmentation chain transfer polymerization

A core–shell structure of crosslinked poly(2-hydroxyethylmethacrylate) as corona and nanocrystalline cellulose (NCC) as core was synthesized by distillation precipitation polymerization. Then, it was reacted with a chain transfer agent of S-(thiobenzoylthioglycolic) acid to obtain NCC-RA. Homopolymers of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) as temperature- and pH-sensitive materials, as well as their dual-sensitive block copolymers, were grafted at the surface of NCC-RA by an in situ reversible addition-fragmentation chain transfer polymerization method via R-group approach. Grafting of chain transfer agent and polymer chains at the surface of nanocrystals was studied by X-ray photoelectron (XPS), Fourier transform infrared, and Raman spectroscopies. Thermogravimetric analysis and XPS were also used to study the graft content of chain transfer agent and polymers. Sensitivity of the polymer-grafted NCCs to temperature and pH were studied by UV–visible spectroscopy. By the addition of poly(N-isopropylacrylamide) block to the poly(acrylic acid)-grafted nanocrystals, phase transition is observed at 32 °C. When the poly(acrylic acid) block is the outer layer, phase transition is observed at higher temperatures and pH-responsivity is observed at pH 7.0–10.0. Finally, morphology of the neat and polymer-grafted NCCs was studied by scanning and transmission electron microscopies.

Preparation of a monolithic cation-exchange material with hydrophilic external layers by two-step reversible addition-fragmentation chain transfer polymerization.

In recent years, the efficient analysis of biological samples has become more important due to the advances of life science and pharmaceutical research and practice. Because biological sample pretreatment is the bottleneck for fast process, material development for efficient sample process in the high-performance liquid chromatography analysis is highly desirable. In this research, a cation-exchange restricted access monolithic column was synthesized by a reversible addition-fragmentation chain transfer polymerization method. Utilizing the controlled/living property of the reversible addition-fragmentation chain transfer method, a monolithic column of cross-linked poly(sulfopropyl methacrylate) was prepared first and then linear poly(glycerol mono-methacrylate) was immobilized covalently on the surface of the polymer. The monolithic material has both functionalities of cation-exchange and protein exclusion. Protein recovery of 94.6% was obtained after grafting of poly(glycerol mono-methacrylate) while the cation-exchange property of the column is still retained. In the study, the relation between the synthetic conditions and properties of the materials was studied. The synthesis conditions including the porogen, monomer concentration, and ratio of monomers/initiator/reversible addition-fragmentation chain transfer agent were optimized. The study provided a method for the preparation of restricted access monolithic columns: a bifunctional material by reversible addition-fragmentation chain transfer polymerization method.