Tertiary Amine Groups Research Articles

A pH-response waterborne epoxy coating based on acid-alkali responsive supramolecular hydrogel

Based on supramolecular interaction, an acid-alkali response supramolecular gel with corrosion inhibitor loading of 50% was designed. By adding the gel to waterborne epoxy coating, a pH-response coating was obtained. The protonation and deprotonation of carboxyl and tertiary amine groups in the gel under different pH led to changes in the microstructure of the gel, which was confirmed by SEM and FTIR, thus controlling the release rate of corrosion inhibitor. After scratched coatings immersed in NaCl solution with pH = 5 for 70 h, the Rct of the coating with 1.5% supramolecular gel higher than that of the coating without gel, indicating the coating with supramolecular gel has good self-healing performance.

Preparation and Cr (VI) Removal Performance of a New Positively Charged PVC Microfiltration Membrane

Poly (vinyl chloride co dimethyl aminoethyl methacrylate) (PVD) and polyvinyl chloride (PVC) were blended, and then the tertiary amine groups of PVD in the casting solution were quaternized in situ with methyl iodide (CH3I) at 60. A new strongly charged positive PVC/PVD (M1) microfiltration membrane was prepared by non solvent induced phase transformation (NIPS), and PVC (M0) microfiltration membrane was prepared and compared with it. The membrane performance parameters such as morphology, pore size, charge, hydrophilicity and pure water flux of M0 and M1 were characterized. The cationic surfactant Octadecyltrimethylammonium chloride (STAC) micelle enhanced filtration was used to remove trace Cr6+(Cr2O7 2-) from the solution. The effects of Cr6+ concentration, pH value and sodium chloride (NaCl) concentration on the interception performance were investigated. The results show that the rejection rate of Cr6+ removal by M1 membrane micelle enhancement is close to 100%. When the mass ratio of Cr6+/STAC is greater than 0.478, the rejection rate of Cr6+ removal by M1 decreases with the increase of Cr6+ concentration; PH value has little effect on the retention of Cr6+ by M1; High concentration of NaCl reduced the rejection rate of Cr6+ by M1. M1 microfiltration membrane has potential development prospects in the treatment of wastewater containing Cr6+.

Removal of high-molecular-weight hexose alkaline degradation products by rosin-based anion adsorbent: Kinetics, thermodynamics, and mechanisms

The dark pigments of beet juice (mainly high-molecular-weight hexose alkaline degradation products , HHADPs) negatively affect the quality of white sugar and should therefore be removed during processing, e.g., through adsorption. Herein, we developed a rosin-based anion adsorbent (RAA) as an effective, regenerable, and green decolorization agent for the removal of HHADPs from beet juice, achieving an equilibrium HHADP adsorption capacity of 6.50 mg/g and a removal efficiency of 89.36%. The investigations of adsorption kinetics, isotherms, thermodynamics, and mechanisms revealed that the adsorption was a spontaneous endothermic multilayer process and mainly corresponded to chemisorption driven by the interactions between the positively charged protonated tertiary amine groups of RAA and the negatively charged carboxylate groups of HHADPs. Our results pave the way to the development of cost-effective and practical adsorbents for an important industrial process, namely beet sugar production. • Rosin-based anion adsorbent (RAA) for beet juice decolorization was developed. • High-molecular-weight hexose alkaline degradation products were used as pigment model. • Equilibrium adsorption capacity of 6.50 mg/g (removal degree = 89.36%) was achieved. • Several adsorption parameters were optimized to improve adsorption performance. • Adsorption was spontaneous and endothermic, mainly corresponding to chemisorption.

Incorporating tertiary amine and thioether in polyarylene sulfide sulfone membranes for multiple separations

Polymers have been widely applied for membrane separations; however, most polymer membranes lack adjustable pores and cannot serve in multiple separations once fabricated. Here, a novel block copolymer, polyarylene sulfide sulfone/amide tertiary amine (PASS/ATA), containing tertiary amine and thioether groups was designed for membrane fabrication as it can be self-assembled into a well-defined, uniform, and continuous pores. Via a facile oxidization procedure, the tertiary amine and thioether groups in the membrane molecular chains were converted into amine oxide and sulfone groups, respectively, which dramatically narrows down the pores of the membranes and greatly improves dye rejection, altering the application of the membranes from ultrafiltration (UF) to nanofiltration (NF). Furthermore, after the thioether units were oxidized into sulfone groups, the solvent resistance of the membranes was greatly increased, ensuring the application of the oxidized membranes in organic solvent nanofiltration (OSN). Dissipative particle dynamics (DPD) simulation was applied to shed insight on the formation mechanisms and transformation processes, as well as to explain the decrease of pore size combined with the enhancement of solvent resistance. As a result, combing tertiary amines with thioether groups in polymer chains endows the membrane with multiple functionalities, allowing for multiple separations including UF, NF, and OSN.

Utility of a xanthene-based dye for determination of nilotinib using two spectroscopic approaches. Applications to bulk powder, capsules, and spiked human plasma.

Novel, selective, facile, and precise spectroscopic approaches were validated to determine nilotinib hydrochloride, a tyrosine kinase inhibitor used to treat patients with chronic myeloid leukemia. These approaches depend on the reaction of the tertiary amine group of nilotinib with erythrosine B in the Britton-Robinson buffer at pH4. Method I, depends on measuring the absorbance of the formed complex at 551 nm. The absorbance concentration plot showed linearity over the concentration range of 1.0 to 9.0μg/ml. Method II, involved the measurement of the quenching of the native fluorescence of erythrosine B by adding nilotinib in an acidic medium. The fluorescence quenching of erythrosine B was measured at 549 nm after excitation at 528 nm. This approach showed excellent linearity in the concentration range of 0.04 to 0.7μg/ml. The limit of detection values for Method I and Method II were 0.225 and 0.008 μg/ml, respectively, while the limit of quantitation values for Method I and Method II were 0.68 and 0.026 μg/ml, respectively. To get the optimal conditions, factors that may affect the formation of the ion-pairing complex were thoroughly examined. The two approaches were carefully validated following the International Conference of Harmonization (ICH Q2R1) guidelines. Statistical assessment of the results achieved using the suggested and previously published comparison approaches showed no significant difference. The approaches were successful in determining nilotinib in a pharmaceutical dosage form as well as spiked human plasma samples. The eco-friendly properties of the methods were evaluated by three different tools.

Amine Groups in the Second Sphere of Iron Porphyrins Allow for Higher and Selective 4e-/4H+ Oxygen Reduction Rates at Lower Overpotentials.

Iron porphyrins with one or four tertiary amine groups in their second sphere are used to investigate the electrochemical O2 reduction reaction (ORR) in organic (homogeneous) and aqueous (heterogeneous) conditions. Both of these complexes show selective 4e-/4H+ reduction of oxygen to water at rates that are 2-3 orders of magnitude higher than those of iron tetraphenylporphyrin lacking these amines in the second sphere. In organic solvents, these amines get protonated, which leads to the lowering of overpotentials, and the rate of the ORR is enhanced almost 75,000 times relative to rates expected from the established scaling relationship for the ORR by iron porphyrins. In the aqueous medium, the same trend of higher ORR rates at a lower overpotential is observed. In situ resonance Raman data under heterogeneous aqueous conditions show that the presence of one amine group in the second sphere leads to a cleavage of the O-O bond in a FeIII-OOH intermediate as the rate-determining step (rds). The presence of four such amine groups enhances the rate of O-O bond cleavage such that this intermediate is no longer observed during the ORR; rather, the proton-coupled reduction of the FeIII-O2- intermediate with a H/D isotope effect of 10.6 is the rds. These data clearly demonstrate changes in the rds of the electrochemical ORR depending on the nature of second-sphere residues and explain their deviation from linear scaling relationships.

Polyurethanes Based on Dicyclohexylmethane 4,4′-Diisocyanate and N-tert-Butyldiethanolamine for Enhancing the Dyeability of Fiber toward Acid Dye

Conventional polyurethane fiber (CPUF) has been widely used in clothes, but it is difficult to color CPUF into a deep hue with acid dyes. In this work, it is proposed that polyurethane is synthesized using dicyclohexylmethane-4,4′-diisocyanate (HMDI) and N-tert-butyldiethanolamine (TBDEA), named poly(HMDI-TBDEA), and is added to a CPUF spinning solution to prepare a modified polyurethane fiber (MPUF) which has an enhanced dyeability toward acid dyes. It is assumed that poly(HMDI-TBDEA) brings tertiary amine groups and tert-butyl groups to MPUF, of which the tertiary amine groups can be protonated under acidic conditions and electrostatically adsorbs anionic ions of acid dyes, and the tert-butyl groups disrupt the ordered arrangement of hard segments in polyurethane to increase the accessible area for acid dyes. The synthesis of poly(HMDI-TBDEA) was validated by proton and carbon nuclear magnetic resonance spectroscopy (1H and 13C NMR) and gel permeation chromatography. MPUF was characterized by differential scanning calorimetry, thermogravimetry, X-ray diffraction, and the tensile test. The study revealed that the addition of poly(HMDI-TBDEA) disrupted the ordered arrangement of the hard segments and strengthened the soft segments but had no obvious influence on the thermal stability. In comparison with CPUF, MPUF exhibited approximately the same elastic recovery, despite a drop in the elongation at break and the break strength. The zeta potential test demonstrated that MPUF might be protonated for enhanced electropositivity under acidic conditions. MPUF displayed superior dyeability than CPUF when dyed with C.I. Acid Orange 7 at pH 3.

Elimination of free fatty acid from palm oil by adsorption process using a strong base anion exchange resin

Deacidification is one of the important processes to obtain a suitable raw feedstock for the production of bio-transformer oil. This work proposed an alternative process for reducing the acidity of refined palm oil by adsorption of the free fatty acids (FFAs) using anion exchange resins (AER). The effect of the types of functional groups (tertiary amine and quaternary ammonium group) and the resin structure (gel and macroporous structure) of the commercially available resins were characterized and investigated for their adsorption ability. The adsorption kinetic and experimental conditions such as adsorption time, the moisture content in resin, and resin amount were studied. The gel-type strong-base anion exchange resins exhibited the best performance for the FFAs removal. This result suggests that the quaternary ammonium functional groups in the resin have a high dissociation capacity for anion exchange and the gel-type resins easily access by the FFAs molecules. The effect of types of functional groups is stronger than that of the resin structure. The adsorption mechanism mainly occurred via an ion exchange equilibrium rather than the hydrogen bond complex. The FFAs adsorption on the resins conformed to the pseudo-second-order kinetic model. Under optimum conditions (room temperature, atmospheric pressure, resin dosage of 0.4 wt%, and 8 h adsorption time), the Pall Tec PTA304 resin reduced the acidity in palm oil from 0.5 to 0.02 mg KOH/g with the adsorption capacity at the equilibrium of 589.5 mg/g, achieving approximately 95 % FFAs removal. The negative values of ΔGads0 and ΔHads0 demonstrated that the FFAs adsorption on the Pall Tec PTA304 resin was a spontaneous and exothermic process. This study provides an insight into the interactions between FFAs and anion exchange resins that is useful for further development of palm based bio-transformer oil.

Pharmacokinetic Evaluation of New Drugs Using a Multi-Labelling Approach and PET Imaging: Application to a Drug Candidate with Potential Application in Neuromuscular Disorders.

The determination of pharmacokinetic properties of new chemical entities is a key step in the process of drug development. Positron emission tomography (PET) is an ideal technique to obtain both biodistribution and pharmacokinetic parameters of new compounds over a wide range of chemical modalities. Here, we use a multi-radionuclide/multi-position labelling approach to investigate distribution, elimination, and metabolism of a triazole-based FKBP12 ligand (AHK2) with potential application in neuromuscular disorders. Target engagement and stabilizing capacity of the drug candidate (AHK2) towards FKBP12-RyR was evaluated using competitive ligand binding and proximity ligation assays, respectively. Subsequently, AHK2 was labelled either with the positron emitter carbon-11 (11C) via 11C-methylation to yield both [11C]AHK2.1 and [11C]AHK2.2, or by palladium-catalysed reduction of the corresponding 5-iodotriazole derivative using 3H gas to yield [3H]AHK2. Metabolism was first investigated in vitro using liver microsomes. PET imaging studies in rats after intravenous (IV) administration at different doses (1 µg/Kg and 5 mg/Kg) were combined with determination of arterial blood time-activity curves (TACs) and analysis of plasma samples by high performance liquid chromatography (HPLC) to quantify radioactive metabolites. Arterial TACs were obtained in continuous mode by using an in-house developed system that enables extracorporeal blood circulation and continuous measurement of radioactivity in the blood. Pharmacokinetic parameters were determined by non-compartmental modelling of the TACs. In vitro studies indicate that AHK2 binds to FKBP12 at the rapamycin-binding pocket, presenting activity as a FKBP12/RyR stabilizer. [11C]AHK2.1, [11C]AHK2.2 and [3H]AHK2 could be obtained in overall non-decay corrected radiochemical yields of 14 ± 2%, 15 ± 2% and 0.05%, respectively. Molar activities were 60-110 GBq/µmol, 68-122 GBq/µmol and 0.4-0.5 GBq/μmol, respectively. In vitro results showed that oxidation of the thioether group into sulfoxide, demethylation of the CH3O-Ar residue and demethylation of -N(CH3)2 were the main metabolic pathways. Fast metabolism was observed in vivo. Pharmacokinetic parameters obtained from metabolite-corrected arterial blood TACs showed a short half-life (12.6 ± 3.3 min). Dynamic PET imaging showed elimination via urine when [11C]AHK2.2 was administered, probably reflecting the biodistribution of [11C]methanol as the major metabolite. Contrarily, accumulation in the gastrointestinal track was observed after administration of [11C]AKH2.1. AHK2 binds to FKBP12 at the rapamycin-binding pocket, presenting activity as a FKBP12/RyR stabilizer. Studies performed with the 3H- and 11C-labelled FKBP12/RyR stabilizer AHK2 confirm fast blood clearance, linear pharmacokinetics and rapid metabolism involving oxidation of the sulfide and amine moieties and oxidative demethylation of the CH3-O-Ar and tertiary amine groups as the main pathways. PET studies suggest that knowledge about metabolic pathways is paramount to interpret images.

Preparation of polymeric vesicles with tertiary amine and epoxy functional groups via polymerization-induced self-assembly

Polymeric vesicles with tertiary amine and epoxy functional groups were fabricated via the reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of 2-(diisopropylamino) ethyl methacrylate (DIPEMA) and glycidyl methacrylate (GlyMA) in an ethanol-water mixture by using poly (ethylene oxide)-4-(4-Cyanopentanoic acid) dithiobenzoate (mPEG45-CPADB) as the macro-chain-transfer agent (macro-CTA). Biocompatible polymer mPEG45 with molecular weight of 2000 and 4-(4-Cyanopentanoic acid) dithiobenzoate (CPADB) were used for the macro-CTA synthesizing via the esterification reaction. Investigation of the degree of polymerization (DP) of the hydrophobic block P(DIPEMA-co-GlyMA) and the solid content indicated that both have significant effect on the particle morphology and particle diameter. 1H NMR and FTIR analysis indicated the existing of tertiary amine and epoxy functional groups on the produced vesicles.

Molecular and Aggregate Structural, Thermal, Mechanical and Photophysical Properties of Long-Chain Amide Gelators Containing an α-Diketo Group in the Presence or Absence of a Tertiary Amine Group

Three structurally related gelators, each containing octadecyl chains, an α-diketo group at the 9,10 positions, and each with a different N-amide group-isobutyl (DIBA), isopentyl (DIPA) or N-(2-(dimethylamino)ethyl) (DMEA)-have been synthesized. Their neat structures as well as the thermal mechanical, and photophysical properties in their gel states with various liquids have been investigated. The gelator networks of DIBA and DIPA in octane, hexylbenzene and silicone oil consist of bundles of fibers. These gels are partially thixotropic and mechanically, thermally (to above their melting or silicone oil gelation temperatures), and photophysically stable. They are mechanically and thermally stronger than the gels formed with DMEA, the gelator with a tertiary amine group. The lone pair of electrons of the tertiary amine group leads to an intra-molecular or inter-molecular charge-transfer interaction, depending on whether the sample is a solution, sol, or gel. Neat, solid DMEA does not undergo the charge-transfer process because its amino and diketo groups are separated spatially by a large distance in the crystalline state and cannot diffuse into proximity. However, the solution of DIPA upon the addition of triethylamine becomes unstable over time at room temperature in the dark or (more rapidly) when irradiated, which initiates the aforementioned charge-transfer processes. The eventual reaction of the gelators in the presence of a tertiary amine group is ascribed to electron transfer from the lone-pair on nitrogen to an α-diketo group, followed by proton transfer to an oxygen atom on the anion radical of the α-diketo group from a methyl or methylene group attached to the nitrogen atom of the cation radical. Finally, the formation of an α-diketyl radical leads to irreversible electronic and structural changes that are observed over time.

Green synthesis of quaternized chitosan nanogel using emulsion-photopolymerization as redox-responsive drug carrier

We report the green synthesis of trimethyl chitosan-functionalized poly(2-hydroxyethyl methacrylate) (PHEMA-TMC) nanogels via surfactant-free emulsion photopolymerization. TMC, a quaternized derivative of chitosan, was synthesized through methylation of chitosan, resulting in quaternary and tertiary amine groups as the main substitution products. TMC tertiary amine moiety and riboflavin (RF) acted as a redox photo-initiating system to generate free radicals for the polymerization under light irradiation. The effects of polymerization parameters such as irradiation time, concentrations of TMC and RF were investigated using MBA as crosslinker. Under the optimal condition of 1 % TMC, 4 % HEMA, 0.8 μM RF, 5 % MBA, and 4 h of polymerization time, the cationic PHEMA-TMC nanogel was synthesized with 76 % monomer conversion and an average diameter of about 106 nm. Moreover, the disulfide-crosslinked PHEMA-TMC nanogel was also synthesized using the disulfide dimethacrylate crosslinker, which exhibited a redox-induced degradation and release of encapsulated melatonin, potentially useful as a redox-responsive drug delivery carrier.

Multifunctionalization of PTFE membrane surface for biofouling resistance and oil/water separation performance improvement

Polytetrafluoroethylene (PTFE) is considered as one of the most promising membrane materials for oil-water separation, mainly because of its excellent chemical and mechanical stability. But its inherent strong hydrophobicity, which can cause the membrane easy fouled by bacteria, limits the application of PTFE membrane. We designed a new surface modification approach, through which hydrophilic and antibacterial PTFE membranes can be fabricated conveniently by combining polymerized dopamine (PDA) and thiolactone chemistries. A copolymer (P(DMAEMA-co-TlaAm)) containing thiolactone and tertiary amine moieties were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization and attached onto the PDA coated PTFE membrane surface, together with glucosamine, via the thoilactone chemistry. Due to efficient glycosylation, the membrane exhibits great hydrophilicity. Water contact angle of the membrane surface dropped from 123° to 13°. Pure water flux of the membrane reached 2490 L m−2 h−1 bar−1, which is 2.7 times that of the original membrane. Also, the separation efficiency of the iso-paraffin emulsion reached 97.5 % at a membrane flux of 90 L m−2 h−1 bar−1. Notably, in addition to the hydrophilicity provided by glucosamine, the modified membranes also showed decent antibacterial property because of the introduction of tertiary amine groups. The bacteria inhibition rate against Staphylococcus aureus reached 99 %.

Synthesis and characterisation of cycloaliphatic and aromatic amines based cardanol benzoxazines: A comparative study

In the current study, an attempt has been made to synthesize cardanol-based mono, bi, and tetra-functional benzoxazines by reacting various aryl amines and cycloaliphatic amines with cardanol (C) in the presence of paraformaldehyde under suitable experimental conditions by Mannich condensation. The resultant benzoxazines were characterized using several analytical techniques for their molecular structure, curing behavior, thermal stability, and hydrophobic nature. By using FTIR and 1H-NMR spectroscopic methods, the structure of benzoxazines was ascertained and assessed with benzoxazines based on aryl and cycloaliphatic amines. Using the DSC technique, the curing temperature of benzoxazines was investigated. Tetra-functional benzoxazines have a lower curing temperature than that of other mono- and bi-functional benzoxazines from the various systems of benzoxazines studied. It was also observed that the curing temperature of cycloaliphatic amine-based benzoxazines is also lower than that of aryl amine-based benzoxazines. The low temperature cure behavior of cycloaliphatic amine benzoxazine systems is due to the presence of a tertiary amine group, which contributes to a more basic nature than that of aryl amines. Thermal stability of polybenzoxazines was studied by TGA technique, among the different benzoxazine systems, the poly(C-ap-ddm) has higher char yield (30%) at 850 °C than that of other polybenzoxazines (poly(C-cha), poly(C-a), poly(C-mbch), poly(C-ddm), poly(C-ap-ipda), poly(C-ap-xyda) and poly(C-ap-mbch)). The value of water contact angle of cycloaliphatic amine-based benzoxazineswas found to be higher than that of aryl amines. Among the polybenzoxazines studied, poly(C-ap-mbch) possesses a higher value of water contact angle of 143°. Poly(C-aP-mbch) filled with 10 wt% SBA-15 (Santa Barbara Amorphous-15) possesses a value of lower dielectric constant (1.62) than that of poly(C-aP-ddm) (1.65). Data from different studies, cardanol based tetra functional benzoxazines can be used as sealants, encapsulants, adhesives, and matrices for microelectronics and automotive applications.

One-Shot Synthesis of B/N-Doped Calix[4]arene Exhibiting Narrowband Multiple Resonance Fluorescence.

A novel macrocycle of B/N-doped calix[4]arene (C-BN) was synthesized by a one-shot double boronation. Owing to the structural tension and electron-donating properties of the nitrogen atoms in the macrocycle, reaction selectively proceeds between the adjacent benzene rings outside the macrocycle. C-BN shows a highly centrosymmetric structure with two multiple resonance (MR) fragments bridged by tertiary amine groups at the 1,3 positions of the benzene ring. Benefiting from the large intermolecular distance (>4.6 Å) between adjacent MR-emitting cores, C-BN also exhibits excellent narrowband emitting features against aggregation-induced quenching and spectrum broadening. Optimized organic light-emitting diode devices based on C-BN exhibit high maximum external quantum efficiencies of 24.7-26.6 % and small full width at half maximums of 25-28 nm over a wide doping range of 1-12 wt %.

One‐Shot Synthesis of B/N‐Doped Calix[4]arene Exhibiting Narrowband Multiple Resonance Fluorescence

AbstractA novel macrocycle of B/N‐doped calix[4]arene (C‐BN) was synthesized by a one‐shot double boronation. Owing to the structural tension and electron‐donating properties of the nitrogen atoms in the macrocycle, reaction selectively proceeds between the adjacent benzene rings outside the macrocycle. C‐BN shows a highly centrosymmetric structure with two multiple resonance (MR) fragments bridged by tertiary amine groups at the 1,3 positions of the benzene ring. Benefiting from the large intermolecular distance (>4.6 Å) between adjacent MR‐emitting cores, C‐BN also exhibits excellent narrowband emitting features against aggregation‐induced quenching and spectrum broadening. Optimized organic light‐emitting diode devices based on C‐BN exhibit high maximum external quantum efficiencies of 24.7–26.6 % and small full width at half maximums of 25–28 nm over a wide doping range of 1–12 wt %.

Inside Cover Picture

The cover picture shows a class of pH‐responsive helix‐to‐coil conformationally transitionable polypeptides (pCTPs) by simply conjugating tertiary amine groups (TAs) to polylysine. Their conformation is highly dependent on the charge state of TAs, showing a helical structure when most TAs are deprotonated and a non‐helical structure when majority of TAs are protonated. Such pCTP exhibited a vehicle‐to‐micelle transition when their conformation transformed from helix to coil, and showed potential as an intelligent carrier for controlled drug release. More details are discussed in the article by Xiong et al. on page 2981—2987.image

Modulation of Conformational Transition of Polypeptides under Slightly Acidic Environment†

Comprehensive SummaryControlling the conformational transition of polypeptides under slightly acidic environment is challenging. Herein, we report a class of pH‐responsive helix‐to‐coil conformationally transitionable polypeptides (pCTPs) by simply conjugating tertiary amine groups (TAs) to polylysine. Their conformation is highly dependent on the charge state of TAs, showing a helical structure when most TAs are deprotonated and a non‐helical structure when majority of TAs are protonated. The conformational transition pH can be modulated by tuning the hydrophobicity of TAs and the incorporation of hydrophobic monomers at a pH range of 7.2 to 6.0. Such pCTP showed a vesicle‐to‐micelle transition when their conformation transformed from helix to coil, facilitating controlled drug release. Our study provided an approach to control the conformational transition of polypeptides under slightly acidic condition.

Glycopolymer and Poly(β-amino ester)-Based Amphiphilic Block Copolymer as a Drug Carrier.

Glycopolymers are synthetic macromolecules having pendant sugar moieties and widely utilized to target cancer cells. They are usually considered as a hydrophilic segment of amphiphilic block copolymers to fabricate micelles as drug carriers. A novel amphiphilic block copolymer, namely, poly(2-deoxy-2-methacrylamido-d-glucose-co-2-hydroxyethyl methacrylate)-b-poly(β-amino ester) [P(MAG-co-HEMA)-b-PBAE], with active cancer cell targeting potential and pH responsivity was prepared. Tetrazine end functional P(MAG-co-HEMA) and norbornene end functional PBAE blocks were separately synthesized through reversible addition fragmentation chain transfer polymerization and Michael addition-based poly-condensation, respectively, and followed by end-group transformation. Then, inverse electron demand Diels Alder reaction between the tetrazine and the norbornene groups was performed by simply mixing to obtain the amphiphilic block copolymer. After characterization of the block copolymer in terms of chemical structure, pH responsivity, and drug loading/releasing, pH-responsive micelles were obtained with or without doxorubicin (DOX), a model anticancer drug. The micelles exhibited a sharp protonated/deprotonated transition on tertiary amine groups around pH 6.75 and the pH-specific release of DOX below this value. Eventually, the drug delivery potential was evaluated by cytotoxicity assays on both the noncancerous human umbilical vein endothelial cell (HUVEC) cell line and glioblastoma cell line, U87-MG. While the DOX-loaded polymeric micelles were not toxic in noncancerous HUVEC cells, being toxic only to the cancer cells indicates that it is a potential specific cell targeting strategy in the treatment of cancer.

PH‐responsive amine‐based fluorescent polymers with on–off switchable and concentration‐dependent fluorescence behaviors

AbstractIn this paper, pH‐responsive fluorescent poly(amino ether ester)s with reversible “on–off” switching fluorescence and concentration‐dependent emission behavior were reported. A remarkable difference fluorescence behavior was observed at diverse polymer concentrations with pH values. Moreover, at all investigated concentrations, poly(amino ether ester)s can respond to acid pH and exhibit extreme acid‐induced fluorescence quenching phenomenon. Dynamic light scattering and transmission electron microscopy analyses confirmed that the fluorescence quenching phenomenon is due to the aggregation, which was caused by the protonation of tertiary amine groups in poly(amino ether ester)s under extreme acidic conditions. Interestingly, the quenched fluorescence can be completely recovered by adding an alkaline solution, thereby enabling an “on–off” switch function by adjusting the pH value. Most importantly, the pH‐responsive fluorescent poly(amino ether ester)s exhibit good biocompatibility and cellular imaging, and its cellular imaging function is highly sensitive to acid pH. Thus, this study opens a new idea for the preparation of amine‐based fluorescent polymers as stimuli‐responsive fluorescent probe for cellular imaging, drug delivery, and disease diagnostics.