A Novel Initiator Containing Alkyne Group for the Polymerization of 2-Ethyl-2-oxazoline

A novel trifunctional initiator with one alkyne and two trifluoromethanesulfonate moieties was synthesized from a protected alcohol 5-hydroxyl-2-phenyl-1, 3-dioxane. The alkyne func- tionalized intermediate with two protected alcohol groups was synthesized by reacting with propargyl bromide. The alcohol groups were cleaved using a mixture of tetrahydrofuran and hydrochloric acid aqueous solution. In the last step the initiator was synthesized us- ing triflic anhydride in carbon tetrachloride. The initiator was characterized by 1H NMR and used for the polymerization of 2-ethyl-2-oxazoline which gives polymers with narrow distribution. For comparison a similar initiator with two tosylates was prepared and used for the polymerization of the monomer 2-ethyl-2-oxazoline, the resulting product has a wide molecular weight distribution and most of the initiator remains unreacted after 24 h which may be due to the steric hindrance between the two tosylate groups. To further explore the steric hindrance phenomenon, a linear tosylate initiator was synthesized, but still some of the initiator remains unreacted, illustrating that both steric hindrance and electrophilic balance affect the efficiency of the cationic ring-opening polymerization. All of the polymers were characterized in detail by using IH NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy, and size exclusion chromatography to confirm the purity and distribution of the polymers.

Delivery of docetaxel using pH-sensitive liposomes based on D-α-tocopheryl poly(2-ethyl-2-oxazoline) succinate:Comparison with PEGylated liposomes

This study aimed to investigate the ability of the novel materials D-α-tocopheryl poly(2-ethyl-2-oxazoline) succinate(TPOS) to construct pH-sensitive liposomes. TPOS was initially synthesized and characterized by TLC, FTIR, and ~1H-NMR. The buffering capacity of polyethylene glycol-distearoyl phosphatidylethanolamine(PEG-DSPE) and TPOS was determined by acid-base titration, and TPOS displayed a slower downtrend and gentler slope of titration curve than PEG-DSPE within pH 7.4–5.0. Studies on the in vitro drug release demonstrated that TPOS modified docetaxel(DOC) liposomes(TPOS-DOC-L) had a slower drugrelease rate at pH 7.4 similar to PEGylated-DOC liposomes(PEG-DOC-L), whereas the release rate reached approximately 86.92% ± 1.69% at pH 6.4. In vitro cellular uptake assays by microplate reader, and flow cytometry revealed that TPOS modified coumarin 6 liposomes(TPOS-C6-L) had stronger cellular uptake at pH 6.4 than that at pH 7.4( P < 0.01). Conversely, for PEGylated C6 liposomes(PEG-C6-L) and conventional C6 liposomes(C6-L), very similar cellular uptakes were exhibited at different pH values. Confocal laser scanning microscopy images showed that PEG-C6-L and C6-L were mainly located in lysosomes. By contrast, TPOS-C6-L showed broader cytoplasmic release and distribution at 4 h. MTT assay showed that the cytotoxicity of TPOS-DOC-L was similar to that of PEG-DOC-L and conventional DOC liposomes(DOC-L) at the same DOC concentration and at pH 7.4, but was much lower than those at pH 6.4 after 48 h of incubation. The apoptosis of PEG-DOC-L and DOC-L had no remarkable improvement with decreased pH from 7.4 to 6.4. Meanwhile, TPOS-DOC-Lsignificantly induced the apoptosis of HeLa cells with decreased pH. Therefore, TPOS can be a biomaterial for the construction of a pH-sensitive drug delivery system.

MECHANISM-TRANSFORMATION SYNTHESIS AND CHARACTERIZATION OF POLY(STYRENE-b-2-ETHYL-2-OXAZOLINE) DIBLOCK COPOLYMER

By mechanism-transformation (anionic --> cationic) poly(styrene-6-2-ethyl-2-oxazoline) diblock copolymer, PS-b-PEOx, was synthesized in two steps. The first step is the polymerization of styrene block capped with ethylene oxide and its tosylation; the second step is the cationic ring-opening polymerization of 2-ethyl-2-oxazoline. The products were thoroughly characterized by various methods, such as H-1-NMR, IR, DMA, TEM and SAXS. The results show that the copolymer obtained possesses high molecular weight and narrow molecular weight distribution.

Preparation and in vitro characterization of paclitaxel-loaded pH-responsive polymeric micelles based on poly(2-ethyl-2-oxazoline)-vitamin E succinate

To ensure the delivery of antitumor drugs to tumor site and quick release in tumor cells, we designed and prepared pH-sensitive polymeric micelles by combining cationic ring-opening polymerization of 2-ethyl-2-oxazoline （EOz） with vitamin E succinate （VES）, and then encapsulating paclitaxel （PTX） into the micelles self-assembled by poly（2-ethyl-2-oxazoline）-vitamin E succinate （PEOz-VES）. The structure of the synthesized PEOz-VES was confirmed by ^1H NMR spectrum, and the molecular weight measured by GPC was 1212 g/mol. The pKa of PEOz-VES with a low critical micelle concentration of （5.84±0.02） mg/L was determined to be 6.01. The PTX-loaded PEOz-VES polymeric micelles prepared by film hydration method were characterized to have a nanoscaled size of about 30 nm in diameter, a positive Zeta potential of 4.86 mV and uniform spherical morphology by TEM observation. The drug loading content and encapsulation efficiency were （2.63±0.16）% and （84.1±3.38）%, respectively. The in vitro release behavior of PTX from PEOz-VES micelles in PBS displayed pH-dependent pattern and was gradually accelerated with decrease of pH value, implying that the micelles could distinguish endo/lysosomal pH and tumor extracellular pH from physiological pH by accelerating drug release. Therefore, the designed PEOz-VES micelles might have significant promise for anti-cancer drug delivery.

Breaking or following the membrane-targeting mechanism:Exploring the antibacterial mechanism of host defense peptide mimicking poly(2-oxazoline)s

Peptides exert important biological functions but their application is hindered by their susceptibility to proteolysis and poor stability in vivo.Thus,functional peptide mimics have drawn a great deal of attention to address this challenge.Poly(2-oxazoline)s,a class of biocompatible and proteolysis-resistant polymer,can work as host defense peptide mimics without following the general membrane-targeting mechanism as shown in our previous work.This observation encouraged us to figure out if poly(2-oxazoline)s are special and break the general membrane-targeting mechanism of host defense peptides and their mimics.In this study,we aimed at the connection between structure and antibacterial mechanism of poly(2-oxazoline)s.A new γ-aminobutyric acid(GABA)-pendent poly(2-oxazoline)was synthesized and investigated to compare with glycine-pendent poly(2-oxazoline)in our previous study,with the former polymer has two extra CH2 groups in the sidechain to increase the hydrophobicity and amphiphilicity.Membrane depolarization assay suggested that incorporating two more CH2 groups into the sidechain of poly(2-oxazoline)resulted in a mechanism switch from DNA-targeting to membrane-targeting,which was supported by the slow time-kill kinetics and slightly distorted and sunken membrane morphology.Besides,GABA-pendent poly(2-oxazoline)showed potent activity against methicillin-resistant S.aureus and low hemolysis on human red blood cells.Moreover,repeated use of the antimicrobial poly(2-oxazoline)did not stimulate bacteria to obtain resistance,which was an obvious advantage of membrane-targeting antimicrobial agents.

Polymeric nanoparticles of poly(2-oxazoline),tannic acid and doxorubicin for controlled release and cancer treatment

A straightforward coassembly strategy was developed for the preparation of polymeric nanoparticles driving by the intermolecular hydrogen bond between neutral poly(2-methyl-2-oxaozline)(PMeOx),tannic acid(TA) and doxorubicin hydrochloride(Dox).The occurrence of the hydrogen-bonding amongst the different functionalities within the formed nanoparticles was verified by infrared(IR) spectroscopy.Scanning electron microscopy(SEM),dynamic light scattering(DLS),UV-vis absorption and photoluminescent measurements indicated the rapid formation of uniform and water dispersible/stable nanoparticles.The relative poor stability of PMeOx-TA-Dox in fetal bovine serum(FBS) solution enabled the rapid separation of Dox and PMeOx-TA,facilitating the release of Dox and its entrance into cellular nuclei as revealed by confocal laser scanning microscopy(CLSM).The presented strategy may provide an efficient alternative for the construction of multifunctional nanomedicines.

模拟宿主防御肽的聚(2-噁唑啉)作为佐剂增强多粘菌素B的抗菌活性并拓展抗菌谱

临床上常用的广谱抗生素无法有效解决抗生素高度耐药ESKAPE菌感染的难题,ESKAPE耐药菌已经成为人类生命健康的重大威胁.抗生素与佐剂的联合治疗是解决抗生素耐药菌感染的重要途径,但是探索对所有ESKAPE耐药菌都具有广谱和高效抗菌活性的抗生素-佐剂组合仍然面临巨大挑战.在这里,我们提出了一种抗生素-佐剂的有效设计策略,将对ESKAPE中耐药阴性菌具有高活性的多粘菌素B(PMB)与模拟宿主防御肽的细菌膜靶向阳离子聚(2-噁唑啉)相结合.我们通过2-噁唑啉单体可控聚合,合成了一系列具有不同疏水性侧链的阳离子聚(2-噁唑啉).研究表明,聚(2-噁唑啉)和PMB的组合效果随着聚(2-噁唑啉)侧链疏水性的提高呈现出从拮抗效应到协同效应的逐渐变化.其中,优选的聚(2-噁唑啉)EACA-POX_(20)显著增强了PMB的抗菌活性,尤其是对于ESKAPE耐药阳性菌的抗菌活性增强了16–32倍.聚(2-噁唑啉)EACA-POX_(20)有效增强了PMB的抗菌活性并扩展了PMB的抗菌谱.聚(2-噁唑啉)和PMB的组合策略能够有效对抗所有耐药ESKAPE病原体,为解决ESKAPE耐药菌提供了新的思路.

抗原改造联合纳米肿瘤疫苗用以克服肿瘤新抗原短缺及在多种肿瘤类型上激起强效抗肿瘤免疫反应

Neoantigen cancer vaccines have been envisioned as one of the most promising means for cancer therapies.However,identifying neoantigens for tumor types with low tumor mutation burdens continues to limit the effectiveness of neoantigen vaccines.Herein,we proposed a "hit-and-run" vaccine strategy which primes T cells to attack tumor cells decorated with exogenous "neo-antigens".This vaccine strategy utilizes a peptide nanovaccine to elicit antigen-specific T cell responses after tumor-specific decoration with a nanocarrier containing the same peptide antigens.We demonstrated that a poly(2-oxazoline)s(POx) conjugated with OVA_(257-264) peptide through a matrix metalloprotease 2(MMP-2) sensitive linker could efficiently and selectively decorate tumor cells with OVA peptides in vivo.Then,a POx-based nanovaccine containing OVA_(257-264) peptides to elicit OVA-specific T cell responses was designed.In combination with this hit-and-run vaccine system,an effective vaccine therapy was demonstrated across tumor types even without OVA antigen expression.This approach provides a promising and uniform vaccine strategy against tumors with a low tumor mutation burden.