AGET ATRP Research Articles

A ratiometric electrochemical biosensor based on ARGET ATRP for detection of HER2 gene

Human epidermal growth factor receptor 2 (HER2), a common proto-oncogene, is overexpressed in a subset of breast cancer patients. It is essential to track HER2 expression for early breast cancer diagnosis. Herein, a ratiometric electrochemical biosensor for detection of HER2 based on activators generated by electron transfer for atom transfer radical polymerisation (AGET ATRP) and hairpin DNA was developed. Specifically, hairpin DNA was first self-assembled on the gold electrode by Au–S bond. Upon capturing HER2, the stem-loop structure of hairpin DNA was unfolded, the signal value of methylene blue (MB) decreased as it moved away from the electrode surface. cDNA was linked with HER2 by complementary base pairing to introduce amino group. Then, the initiator 2-bromo-2-methylpropionic acid (BMP) were connected to the amino group on the cDNA to activate ARGET ATRP. The detection performance of biosensors for HER2 was explored by the ratio signal between two signal molecules. Under optimal conditions, this ratiometric electrochemical biosensor shows good selectivity and stability with a wide detection range of 1–1 × 106 pM and a detection limit of 78.47 fM. Furthermore, the biosensor exhibits satisfactory anti-interference ability due to the hairpin DNA and dual signal system, and has promising application prospects in the detection of other DNA disease markers.

Nanofibrous membranes modified by zwitterionic polyelectrolyte brushes for effective adsorption of ciprofloxacin hydrochloride

In this study, zwitterionic polyelectrolyte brushes poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) were grafted on poly (vinyl alcohol)/graphene oxide (PVA/GO) nanofibrous membranes by surface-initiated activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP). The obtained PVA/GO@PMPC nanofibrous membranes were used as adsorbents for removal of ciprofloxacin hydrochloride. The membrane prepared with the most amount of GO in the electrospinning solution and the highest MPC concentration during grafting polymerization displayed the largest adsorption amount of ciprofloxacin hydrochloride (245.6 mg/g). Within 15 h, the adsorption achieved equilibrium, and the removal process agreed well with pseudo-second-order kinetic model. At pH = 7.0, the maximum adsorption capacity was attained, and the adsorption capacity increased gradually with temperature. Study on adsorption mechanism revealed that π-π interactions, hydrogen bonding interactions and electrostatic interactions might be involved for removal of ciprofloxacin hydrochloride. After being repeatedly used for six times, binding affinity of the membrane did not change significantly. This study provided a general method for creating nanofibrous membranes with superior adsorption performance for removal of organic pollutants.

Polyacrylamide Grafted Activated Carbon by Surface‐Initiated AGET ATRP for the Flocculation of MFT

AbstractPolyacrylamide (PAM) is grafted from the surface of activated carbon (AC) by surface‐initiated activators generated by electron transfer atom transfer radical polymerization (SI‐AGET ATRP). This is accomplished by pre‐functionalizing the surface of activated carbon by oxidation, followed by the attachment of an ATRP initiator. From this surface, SI‐AGET ATRP of acrylamide monomers is performed. The resulting AC‐PAM is characterized by FTIR, XPS, TGA, and BET analysis. Additionally, the grafted polymer is cleaved from the surface of AC and its molecular weight distribution is measured by SEC. This material is designed to explore the effect that grafting a polymer flocculant onto AC will have on the polymer's flocculating abilities. This is evaluated by measuring the flocculation and dewatering of mature fine tailings (MFT) when dosed with the AC‐PAM compared to PAM. In all, this work demonstrates the successful grafting of PAM onto AC, as well as potential wastewater applications for this composite material.

Iron-Mediated AGET ATRP of Methyl Methacrylate in Green Polar Ethyl Lactate Solvent without any External Ligand

Iron-Mediated AGET ATRP of Methyl Methacrylate in Green Polar Ethyl Lactate Solvent without any External Ligand

Sugar decorated star-shaped (co)polymers with resveratrol-based core \u2013 physicochemical and biological properties

Star-shaped glycopolymers due to the attractive combination of the physicochemical, morphological, self-assembly properties along with biological activity have gained increased attention as innovative agents in novel cancer therapies. Unfortunately, the production of these highly desirable biomaterials remains a challenge in modern macromolecular chemistry. The main reason for that is the low polymerizability of ionic glycomonomers originated from their steric congestion and the occurrence of ionic interactions that generally negatively influence the polymerization progress and hinder controllable reaction pathway. In this work, the new ionic sugar monomer was (co)polymerized for the first time via Activator Generated by Electron Transfer Atom Transfer Radical Polymerization (AGET ATRP) using a three-arm resveratrol-based core to obtain star-like (co)polymers. The obtained products were examined in terms of their physicochemical properties and morphology. Aside from the synthesis of these new glycopolymers, also a thorough description of their thermal properties, ability to self-assembly, the formation of stable superstructures was studied in detail. It was found that examined (co)polymers did not show any heterogeneities and phase separation, while their variation of glass transition temperature (Tg) was strictly related to the change in the number of glycomonomer. Also, the stability and shapes of formed superstructures strictly depend on their composition and topology. Finally, we have shown that synthesized carbohydrate-based polymers revealed high antiproliferative activity against several cancer cell lines (i.e., breast, colon, glioma, and lung cancer). The cytotoxic activity was particularly observed for star-shaped polymers that were systematically enhanced with the growing concentration of amine moieties and molecular weight. The results presented herein suggest that synthesized star-shaped glyco(co)polymers are promising as drug or gene carriers in anticancer therapies or anti-tumor agents, depending on their cytotoxicity.Graphical abstract

Screening Design of Experiments of AGET ATRP of Butyl Methacrylate in a Stirred Emulsion Reactor

AbstractThis study investigates the ab initio atom transfer radical polymerization of butyl methacrylate using activator generated by electron transfer in a well‐mixed 2 L emulsion reactor. A first time reported polymerization system initiates by a catalyst complex with hexamethylenetetramine as a ligand and in presence of sodium dodecyl sulfate as an anionic surfactant. The system shows a relatively low monomer conversion rate of 14% and a controlled number average molecular weight (Mn) of 8 kg mol−1 with a polydispersity index (Ð) of 1.24 for 2 h reaction time. A statistical design of experiments is followed to study the effects of reaction temperature, surfactant amount, stirring speed, and ligand amount to assess their impact on the monomer conversion, Mn, and Ð. A fractional factorial with a resolution IV design is adopted and an empirical regression model is developed from eight experimental trials. The results tell that the reaction temperature has the greatest influential on the process outputs. Also, the surfactant amount and stirring speed strongly affect the conversion rate, while the ligand amount strongly affects the Mn and Ð. The results also show that the temperature–surfactant interaction is the most significant on the conversion rate and Mn.

One-Pot Fabrication of Hierarchically Bicontinuous Polystyrene Monoliths with Homogeneous Skeletons and Glycopolymer Surfaces.

The hierarchically bicontinuous polystyrene monoliths (HBPMs) with homogeneous skeletons and glycopolymer surfaces are fabricated for the first time based on the medium internal phase emulsion (MIPE) templating method via activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP). The synergistic self-assembly of amphiphilic diblock glycopolymer (ADG) and Pluronic F127 (PF127) at the oil/water interface via hydrogen bonding interaction contributes to the formation of bicontinuous MIPE with deformed neighboring water droplets, resulting in the highly interconnected HBPM after polymerization. There is a bimodal pore size distribution in the HBPM, that is, through pores (150-5000nm) and mesopores (10-150nm). The HBPMs as prepared show excellent biocompatibility, homogeneous skeletons, strong mechanical strength, and high bed permeability, overcoming the practical limitations of the second generation of polystyrene (PS) monoliths. Glycoprotein concanavalin A (Con A) can be easily and quickly separated by the HBPM in hydrophilic interaction chromatography (HILIC) mode. These results suggest the HBPMs have great potentials in catalysis, separations, and biomedical applications.

Construction of macroinitiators labeled magnetic spheres as a notable signal amplification system for biosensing

Here we report macroinitiators labeled magnetic spheres (MSs) as a notable signal amplification system for biosensing. The macroinitiators as labels with multiple initiators on each polymer backbone facilitate the polymerization process for fluorescent signal amplification, while the carriers of micro-sized MSs are beneficial to reaction kinetics and could be rapidly read via flow cytometer in a high-throughput way. By utilizing an optimal two-step activators generated electron transfer for atom transfer radical polymerization (AGET ATRP) reaction, our proposed macroinitiators labeled MSs strategy exhibits a significantly superior fluorescent signal amplification effect when compared to conventional dye-labeled MSs, indicating the promising potential for biosensing in diagnostic fields.

Influence of HMTA ligand in MMA AGET ATRP emulsion polymerization

AbstractInteractions of hexamethylenetetramine ligand in atom transfer radical polymerization initiated by activator generated by electron transfer were studied. Polymerization of methyl methacrylate was done using two‐step experimental procedure in 2 L emulsion batch reactor at 50, 60, and 80°C. The selection of reactant ratios was quite challenging for a reactor of this size. Replicate runs were conducted for data reproducibility purpose. Gravimetry method and gel permeation chromatography were used to determine monomer conversion, Mn, and PDI of polymer samples. PMMA produced was also characterized by means of dynamic light scattering, Fourier‐transform infrared spectroscopy and nuclear Magnetic Resonance spectroscopy. Results showed high monomer conversion up to 93% and Mn ranging 243–274 kg/mol with PDI from 1.45 to 1.60. Besides, combining HMTA with sodium dodecyl sulfate, an anionic surfactant, a well‐controlled polymer with a lower Mn of 201 kg/mol and PDI of 1.56 was obtained in 3 hr reaction time.

Ultrasensitive DNA electrochemical biosensor based on MnTBAP biomimetic catalyzed AGET ATRP signal amplification reaction.

In this paper, an ultrasensitive, highly selective and green electrochemical biosensor for quantifying DNA sequences (aM DNA) based on a MnTBAP catalyst for AGET ATRP reaction is proposed. For the first time, a combination of biomimetic catalyzed free radical polymerization and DNA electrochemical biosensing was used as a signal amplification strategy.

An ultrasensitive fluorescent aptasensor based on truncated aptamer and AGET ATRP for the detection of bisphenol A.

Given the gigantic harmfulness of bisphenol A (BPA), a novel and ultrasensitive aptasensor, which employs the truncated BPA aptamer, click chemistry, and activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP), was developed herein for the quantitative determination of BPA. Firstly, hairpin DNAs (hairpins) with a thiol at the 5' end and an azide group at the 3' end were conjugated with aminated magnetic beads (MBs) through heterobifunctional cross-linkers. BPA truncated aptamer (ssDNA-A) hybridizes with its complementary single-stranded DNA (ssDNA-B) to form double-stranded DNA. In the presence of BPA, ssDNA-A specifically captures BPA, and then ssDNA-B is released. Subsequently, the ssDNA-B hybridizes with hairpins to expose the azide group near the surface of the MBs. Then, propargyl-2-bromoisobutyrate (PBIB), the initiator of AGET ATRP containing alkynyl group, was conjugated with azide group of hairpins via the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). Consequently, a large number of fluorescein-o-acrylate (FA) were introduced to the MBs through AGET ATRP, resulting in that the fluorescence intensity was increased dramatically. Obviously, the fluorescence intensity was especially sensitive to the change of BPA concentration, and this method can be used in quantitative determination of BPA. Under optimal conditions, a broad liner range from 100fM to 100nM and a low limit of detection (LOD) of 6.6fM were obtained. Moreover, the method exhibits not only excellent specificity for BPA detection over BPA analogues but high anti-interference ability in real water sample detection, indicating that it has huge application prospect in food safety and environment monitoring.

Fabrication of poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) macroporous microspheres through activators regenerated by electron transfer atom transfer radical polymerization for rapid separation of proteins

Activators regenerated by electron transfer atom transfer radical polymerization (AGET ATRP) were firstly used in suspension polymerization to prepare macroporous microspheres based on a copolymer of glycidyl methacrylate and ethylene glycol dimethacrylate. Compared to conventional radical polymerization (CRP), the microspheres by AGET ATRP showed more homogeneous structure, larger pores, and higher protein binding capacity. The body of microspheres are formed by the large clusters resulted from the aggregated little particles. The size of the particles in microspheres by AGET ATRP was 10–300 nm which was smaller than that (400–800 nm) of the microspheres by CRP. AGET ATRP gave larger pore size (275 ± 5 nm) and surface area (59.3 ± 1 m2/g) than CRP (234 ± 5 nm, 37.5 ± 1 m2/g). The microspheres were modified with polyethylene imine for anion resins that were evaluated in term of its protein binding capacity. The results indicated that the static (69 ± 0.5 mg/mL) and dynamic binding capacity (61 ± 0.5 mg/mL) of proteins on modified microspheres by AGET ATRP were higher than that (34 ± 0.5 mg/mL and 19 ± 0.5 mg/mL) by CRP. Meanwhile, the proteins binding capacity on the microspheres by AGET ATRP decreased only less than 10% when the flow rate increased 10 times. These macroporous media show a large potential in rapid separation of proteins.

Ultrasensitive fluorescence detection of sequence-specific DNA via labeling hairpin DNA probes for fluorescein o-acrylate polymers

Sensitive detection of DNA is conducive to enhance the accuracy of diseases diagnosis and risk prediction. In this work, we report the use of activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) as a novel on-chip amplification strategy for the fluorescence detection of DNA. More specifically, the target DNA was captured by the on-chip immobilized hairpin DNA probes. Upon hybridization, exposed 3′-N3 of the hairpin was used to attach AGET ATRP initiators onto the silicon surface by click chemistry. Then, numerous fluorescent labeling linked to the end of the probes via the formation of long chain polymers of fluorescein o-acrylate, which in turn amplified the fluorescence signal for DNA detection. Under optimal conditions, it showed a good linear range from 100 fM to 1 μM in DNA detection, with the limit of detection as low as 4.3 fM. Moreover, this strategy showed good detection performance in complex real serum samples, the fluorescence intensity of 0.1 nM tDNA in 1% fetal bovine serum samples was 97.6% of that in Tris-EDTA buffer. Based on its high sensitivity, reduced cost and simplicity, the proposed signal amplification strategy displays translational potential in clinical application.

Cross-Linked Polystyrene Shells Grown on Iron Oxide Nanoparticles via Surface-Grafted AGET-ATRP in Microemulsion.

Most applications of nanoparticles require robust stabilization, for example, by surface-bound ligands or the encapsulation within polymer shells. Furthermore, for biomedical applications, the particles must be dispersible in a complex biological environment. Thus, high-quality nanoparticles synthesized in organic solvents must be transferred into aqueous media. Here, we present a novel scalable method enabling the robust hydrophilic encapsulation of non-agglomerated nanoparticles by growing polystyrene shells via AGET-ATRP in microemulsion. To demonstrate this approach, we encapsulate iron oxide nanoparticles (diameter: 13.7 ± 0.6 nm). Because the ATRP initiator is grafted onto the nanoparticles' surface, the shells are covalently attached to the iron oxide cores. By varying the amount of monomers, the shell thickness can be adjusted precisely, as indicated by the increasing hydrodynamic size from ∼22 to 26 nm (DLS, number mean) with an increasing amount of added monomers. Moreover, the degree of cross-linking can be controlled by the amount of added divinylbenzene (DVB). To evaluate the robustness of the polymer shells against ion infusion, we introduce a novel colorimetric method, which is based on the formation of the red iron thiocyanate complex. After addition of HCl, the increase in absorbance at 468 nm indicates leaching of iron ions from the polymer-encapsulated core particles. These measurements confirm that with increasing shell thickness, significantly improved shielding is achieved. Furthermore, high concentrations of added DVB [33-50% (v/v) in a monomer mixture] improve the shielding effect. However, when smaller amounts of DVB were added [10-25% (v/v)], the shielding effect was diminished, even in comparison to non-cross-linked polymer shells. This finding suggests a higher porosity of shells with a low degree of cross-linking.

γ-valerolactone (GVL) as a bio-based green solvent and ligand for iron-mediated AGET ATRP

AbstractIn this paper, γ-valerolactone (GVL), a bio-based polar solvent, was applied as green solvent for iron(III)-catalyzed AGET ATRP without any external ligand. GVL is a fully degradable, non-toxic green solvent and has complex ability to iron halide complexes through –OCO- group. GVL as the solvent and the ligand for AGET ATRP of MMA in a controlled manner, as proved by kinetic study, the low PDI values and the increase in polymer molecular weight versus monomer conversion. Chain re-initiation experiments and 1HNMR characterization were conducted to further confirm the living feature.

Fabrication of nanoprobe via AGET ATRP and photocatalytic modification for highly sensitive detection of Hg(II)

In this paper, a functional nanoprobe based on graphene oxide (GO) composites was successfully prepared for detection of mercury ion (Hg(II)) with high sensitivity. GO as a substrate was modified and used for the growth of polymer chains to synthesize polyacrylonitrile-grafted GO (PAN-g-GO) by activator generated by electron transfer atom transfer radical polymerization (AGET ATRP). Under the condition of visible light shines, the PAN-g-GO was further modified to prepare [poly(acrylonitrile-co-vinyl(diphenyl pyridine))]-grafted GO (P(AN-co-PHPY)-g-GO) nanomaterial by one-step synthesis. Finally, P(AN-co-PHPY)-g-GO as a nanoprobe was dropped to the surface of the glassy carbon electrode and assembled to the electrochemical sensor. Moreover, it can effectively improve the enrichment capacity of mercury ions and increase the electron transfer rate on the electrode surface. Differential pulse anodic stripping voltammetry (DPASV) was used to evaluate the electrochemical performance. Under optimum conditions, the response of Hg(II) at this resulting sensor was linear in the range of 2.0 μM~0.1 nM with a detection limit of 0.06 nM. Additionally, this sensor showed excellent reproducibility, selectivity and stability.

Chlorophyll derivatives as catalysts and comonomers for atom transfer radical polymerizations

Derivatives of chlorophyll were investigated as both catalysts and comonomers to generate well-defined polymers with narrow dispersities under AGET ATRP conditions.

The Influence of Activating Agents on the Controlled Synthesis of Poly(methyl methacrylate) in the Presence of Ruthenacarboranes

The radical polymerization of methyl methacrylate catalyzed by systems based on the carborane complexes of ruthenium(III) is studied in the presence of a number of activating agents: tin 2-ethyl hexanoate, aluminum isopropoxide, isopropylamine, and AIBN. It is shown that in the presence of the systems under consideration, polymerization proceeds in a controlled mode via the ATRP mechanism (AGET or ICAR ATRP) at catalyst concentrations with ppm level relative to that of the monomer. As the degree of monomer conversion grows, the molecular weight of the polymer increases linearly while its polydispersity coefficients decrease linearly. The role of the mentioned agents is to transfer the catalyst to the active form containing a metal atom in the oxidation number +2 and able to interact with halogen-terminated dormant polymer chains. It is first shown that the carborane complexes of ruthenium(II) are applicable for the catalysis of controlled radical polymerization.

Investigating the Effect of Silica Aerogel Nanoparticles on the Kinetics of AGET ATRP of Methyl Methacrylate

Abstract Hexamethyldisilazane-modified silica aerogel nanoparticles were used for in situ polymerization of methyl methacrylate by activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP) to synthesize tailor-made PMMA nanocomposites. Appropriate dispersion of silica aerogel nanoparticles in the monomer solution and improvement in interfacial interaction between the PMMA matrix and nanoparticles are two main reasons for application of HMDS-modified silica aerogel nanoparticles. Nitrogen adsorption/desorption isotherm was employed to examine surface area and structural characteristics of the HMDS-modified silica aerogel nanoparticles. Evaluation of size distribution and morphological studies were also performed by SEM and TEM. Conversion and molecular weight determinations were carried out using GC and SEC, respectively. Addition of 3 wt% HMDS-modified silica aerogel nanoparticles leads to decrement of conversion from 85 to 64%. Molecular weight of PMMA chains also decreases from 13,912 to 10,810 g⋅mol−1 by addition of only 3 wt% HMDS-modified silica aerogel nanoparticles; however, polydispersity index values increases from 1.18 to 1.51. Linear increase of ln(M0/M) with time for all the samples shows that polymerization proceeds in a living manner. In addition, suitable agreement between theoretical and experimental molecular weight in combination with low PDI values can appropriately demonstrate the living nature of the polymerization. TGA results indicate that by increasing HMDS-modified silica aerogel nanoparticles content, slight improvements in thermal stability of the nanocomposites were obtained. DSC results show a decrease in Tg from 86.9 to 80.1°C by addition of 3 wt% HMDS-modified silica aerogel nanoparticles.

Surface modification of carbon nanotubes by using iron-mediated activators generated by electron transfer for atom transfer radical polymerization.

Herein, a surface-initiated activator generated by electron transfer for an atom transfer radical polymerization (AGET ATRP) system was developed on the surface of multiwall carbon nanotubes (MWCNTs) by using FeCl3·6H2O as the catalyst, tris-(3,6-dioxoheptyl) amine (TDA-1) as the ligand and ascorbic acid (AsAc) as the reducing agent. A wide range of polymers, such as polystyrene (PS), poly(methyl methacrylate) (PMMA) and poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA), were successfully grafted onto the surfaces. The core–shell structure of MWCNTs@PS was observed by TEM. Both Raman spectra and the results of hydrolysis of MWCNTs@PS (after extraction by THF) confirmed that the PS chains were covalently tethered onto the surfaces of the MWCNTs. Due to superior biocompatibility of the iron catalyst, the strategy of modification of MWCNTs via iron-mediated AGET ATRP provided a promising method for the controllable and biocompatible modification of nanomaterials.