Yan Xiao

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Name: 肖艳; Xiao, Yan

Organization: East China University of Science and Technology , China

Department: School of Materials Science and Engineering

Title: Associate Professor(PhD)

Chemicals
References

A highly stretchable bioelastomer prepared by UV curing of liquid-like poly(4-methyl-ε-caprolactone) precursors

Co-reporter:Yan Xiao;Sihuan Lang;Miaomiao Zhou;Jing Qin;Rui Yin;Jingming Gao;Andreas Heise;Meidong Lang

Journal of Materials Chemistry B 2017 vol. 5(Issue 3) pp:595-603

Publication Date(Web):2017/01/18

DOI:10.1039/C6TB02507B

A series of biodegradable and crosslinkable precursors based on poly(4-methyl-ε-caprolactone) (PMCL) were prepared by ring-opening polymerization (ROP), followed by the complete acrylation of both hydroxyl ends. Afterwards, biodegradable networks exhibiting totally amorphous character were obtained via photocrosslinking without organic solvent or high temperature. As a result, their mechanical properties varied significantly from brittle to elastic upon increasing the length of the PMCL precursors. Both covalent crosslinking and trapped entanglements between crosslinking segments were likely to contribute to the unique properties of the bioelastomer. In particular, networks formed by the precursors with large molecular weights presented high flexibility and resilience, which match the mechanical properties of soft tissues like blood vessels, bladder and cardiovascular tissue. Preliminary degradation and in vitro cytotoxicity studies of the crosslinked network showed excellent biodegradability and biocompatibility. Moreover, it was demonstrated that the liquid-like PMCL precursor made the patterning easily processable even in the absence of any solvent or heating.

Schizophrenic poly(ε-caprolactone)s: synthesis, self-assembly and fluorescent decoration

Co-reporter:Jun Zhang;Xueli Luo;Lianlei Wen;Andreas Heise;Meidong Lang

Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 21) pp:3261-3270

Publication Date(Web):2017/05/30

DOI:10.1039/C7PY00461C

Double hydrophilic block copolymers (DHBCs) based on poly(ε-caprolactone)s, poly(6-acetoxyl-ε-caprolactone)-b-poly(4-N-piperilactone) (PCCL-b-PPIL), were synthesized via ring-opening polymerization and deprotection. The self-assembly behaviour of these block copolymers in aqueous solutions was thoroughly explored via a combination of UV-vis spectroscopy, zeta potential measurement, 1H NMR spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM). It was observed that “schizophrenic” aggregations were formed and triggered by pH, i.e., the copolymers could self-assemble into PCCL-core micelles at acidic pH and PPIL-core micelles at alkaline pH. In addition, pendant groups in each block of copolymers facilitated further chemical modification with fluorescent dyes such as 1-(hydroxymethyl)pyrene and FITC. The fluorescence properties of pyrene-functionalized copolymers were closely related to their aggregate morphology, which could be adjusted simply by altering the environmental pH values. Meanwhile, it is expected that this novel type of degradable schizophrenic block copolymer holds potential application in stimuli-responsive fluorescent probes.

Synthesis of well-defined carboxyl poly(ε-caprolactone) by fine-tuning the protection group

Co-reporter:Jun Zhang, Yan Xiao, Heng Xu, Chen Zhou and Meidong Lang

Polymer Chemistry 2016 vol. 7(Issue 28) pp:4630-4637

Publication Date(Web):14 Jun 2016

DOI:10.1039/C6PY00932H

The introduction of reactive groups such as –NH2, –COOH etc. onto a poly(ε-caprolactone) (PCL) backbone was necessary for further modification but a well-controlled approach remains a challenge for synthetic chemistry. Carboxyl functionalized PCL was typically prepared via three steps involving the synthesis of the corresponding monomer with a carboxyl-protecting group, polymerization and the removal of the protection. Except for obtaining purified monomers and a decent polymerization, the most critical step in carboxyl PCL synthesis was the deprotection from the degradable main chain. Therefore, electronic effects and steric hindrance of the protecting group were taken into account with the aim for controllable polymerization and feasible deprotection. Substituents including –CH3, H and NO2 with discriminative electronegativity on the para position of the benzyl protecting group have been selected to investigate their behavior in monomer preparation, polymerization and deprotection, respectively. It turned out that the electron donating group (–CH3) displayed the highest selectivity in the monomer preparation, excellent control over the polymerization degree and the most efficient removal of the protecting groups without degradation of the backbone. In addition, the reactivity of the pendant carboxyl groups on PCL was demonstrated by amidation with 4-amino-2,2,6,6-tetramethylpiperidinyloxy (4-amino-TEMPO). Our results also provide guidance information on preparing well-defined biodegradable polymers with pendant reactive groups such as polypeptides, expanding the library of novel biomaterials.

Preparation, degradation and in vitro release of ciprofloxacin-eluting ureteral stents for potential antibacterial application

Co-reporter:Xiaofei Ma, Yan Xiao, Heng Xu, Kun Lei, Meidong Lang

Materials Science and Engineering: C 2016 Volume 66() pp:92-99

Publication Date(Web):1 September 2016

DOI:10.1016/j.msec.2016.04.072

•Ciprofloxacin-eluting ureteral stents were prepared by the dipping method.•Degradation and release profiles were tailored by altering the copolymer composition.•The release mechanism at stage I was mainly controlled by chain scission of PLCL.•The release profile at stage II was dominated by an erosion-controlled mechanism.•CIP-loaded PLCL coatings showed well resistance against E. coli and S. aureus.Drug-eluting stents with biodegradable polymers as reservoirs have shown great potential in the application of interventional therapy due to their capability of local drug delivery. Herein, poly(l-lactide-co-ε-caprolactone) (PLCL) with three different compositions as carriers for ciprofloxacin lactate (CIP) was coated on ureteral stents by the dipping method. To simulate a body environment, degradation behavior of PLCL as both the bulk film and the stent coating was evaluated in artificial urine (AU, pH 6.20) respectively at 37 °C for 120 days by tracing their weight/Mn loss, water absorption and surface morphologies. Furthermore, the release profile of the eluting drug CIP on each stent exhibited a three-stage pattern, which was greatly affected by the degradation behavior of PLCL except for the burst stage. Interestingly, the degradation results on both macroscopic and molecular level indicated that the release mechanism at stage I was mainly controlled by chain scission instead of the weight loss or morphological changes of the coatings. While for stage II, the release profile was dominated by erosion resulting from the hydrolysis reaction autocatalyzed by acidic degradation residues. In addition, ciprofloxacin-loaded coatings displayed a significant bacterial resistance against E. coli and S. aureus without obvious cytotoxicity to Human foreskin fibroblasts (HFFs). Our results suggested that PLCL copolymers with tunable degradation rate as carriers for ciprofloxacin lactate could be used as a promising long-term antibacterial coating for ureteral stents.

Reversible thermo-sensitivity induced from varying the hydrogen bonding between the side residues of rationally designed polypeptides

Co-reporter:Hong Liu, Yan Xiao, Heng Xu, Yebin Guan, Jun Zhang and Meidong Lang

Chemical Communications 2015 vol. 51(Issue 50) pp:10174-10177

Publication Date(Web):13 May 2015

DOI:10.1039/C5CC03017J

Rationally designed polypeptides with similar molecular structures but varying patterns of hydrogen bonding between the side groups have been synthesized and demonstrated to possess distinct solubility and thermal behaviors. Further balancing the ratio of both isopropylamine and ethylenediamine side groups endows the random copolymer with reversible thermo-sensitivity.

Micelle controlled release of 5-fluorouracil: Follow the guideline for good polymer–drug compatibility

Co-reporter:Ming Yuan, Yan Xiao, Vanminh Le, Chao Wei, Yutong Fu, Jianwen Liu, Meidong Lang

Colloids and Surfaces A: Physicochemical and Engineering Aspects 2014 Volume 457() pp:116-124

Publication Date(Web):5 September 2014

DOI:10.1016/j.colsurfa.2014.04.062

•Flory–Huggins interaction parameter was used to reckon the drug–polymer affinity.•With CAB groups pending on PCL, copolymer showed enhanced 5-FU-polymer affinity.•mPEG-b-PCL copolymer with CAB groups pending (100% substitution) was synthesized.•A 5-FU micelle carrier superior to micelle prepared by mPEG-b-PCL was developed.•Tailored pendant groups on PCL lead to optimal drug loading and release behavior.Flory–Huggins interaction parameter (χpd) was introduced to qualitatively evaluate the drug–polymer compatibility between hydrophilic 5-fluorouracil (5-FU) and hydrophobic core block, which was formed by poly[γ-(carbamic acid benzyl ester)-ɛ-caprolactone] (PCABCL) and poly(ɛ-caprolactone) (PCL). The calculation results indicated that PCABCL had better affinity with 5-FU than PCL. Thus, a series of diblock polymers monomethoxy poly(ethylene glycol)-b-poly[γ-(carbamic acid benzyl ester)-ɛ-caprolactone] (mPEG45-b-PCABCLn) was synthesized, followed by the preparation of 5-FU loaded micelles. The introduction of γ-(carbamic acid benzyl ester) (CAB) group significantly decreased the crystallinity of copolymers and increased the hydrophilicity of the micellar core, leading to an improved drug loading content. These micelles had high stability and spherical morphology. The release behavior could be turned by the length of core-forming block. Moreover, micelles prepared by mPEG45-b-PCABCL19 displayed the highest 5-FU loading content and the most controlled release behavior. These blank micelles showed very low toxicity against HCT116 cancer cells. Meanwhile 5-FU loaded micelles exhibited a concentration dependent increase in HCT116 cell death by inducing cell apoptosis in vitro. These results indicated that these micelles have great potential in cancer therapy.Non-covalent bonding, such as hydrogen bonding interaction, polarity attraction, π–π interaction, etc., is widely existed between carriers and drugs. The presence of these forces is a vigorous supplement to hydrophobic interaction, which has great influence on drug loading and release behavior.

Synthesis and degradation behavior of miktoarm poly(-caprolactone)2-b-poly(L-lactone)2 microspheres

Co-reporter:Xi Zhang;Yan Xiao;Meidong Lang

Polymer Journal 2013 45(4) pp:420-426

Publication Date(Web):2012-10-10

DOI:10.1038/pj.2012.166

Poly(ε-caprolactone)2-b-poly(L-lactide)2 miktoarm block copolymers were successfully synthesized via ring-opening polymerization using pentaerythritol as the initiator and a protection–deprotection procedure. 1H nuclear magnetic resonance (1H NMR) and size exclusion chromatography (SEC) were employed to characterize the miktoarm structure, molecular weight and molecular weight distribution. The microspheres of poly(ε-caprolactone)2-b-poly(L-lactide)2 ((PCL)2-b-(PLLA)2) were produced by an oil-in-water emulsion solvent extraction/evaporation method and studied with scanning electron microscopy (SEM). The hydrolytic degradation of microspheres with different architectures and compositions was performed at 37 °C in a phosphate-buffered saline solution (pH=7.4). The weight loss of the microspheres was strongly affected by the molecular architecture, chain length and composition. The compositional, or molar ratio, changes were monitored during the degradation using 1H NMR, SEC, differential scanning calorimetry and SEM, all of which suggested that the degradation proceeded from the surface to the interior and could be described using a combined degradation model with surface erosion and bulk degradation.

In-situ formation of silver nanoparticles stabilized by amphiphilic star-shaped copolymer and their catalytic application

Co-reporter:Xiujuan Huang, Yan Xiao, Wei Zhang, Meidong Lang

Applied Surface Science 2012 Volume 258(Issue 7) pp:2655-2660

Publication Date(Web):15 January 2012

DOI:10.1016/j.apsusc.2011.10.113

Abstract

Silver nanoparticles (Ag NPs) were prepared via in situ reduction of silver nitrate (AgNO₃) using polymeric micelles as nanoreactors without any additional reductant. The micelles were constructed from the amphiphilic star-shaped copolymer composed of poly(ɛ-caprolactone) (PCL) segment, 2-(dimethylamino)ethyl methacrylate (DMAEMA or DMA) units and oligo(ethylene glycol)monomethyl ether methacrylate (OEGMA or OEG) units. The Ag NPs stabilized by those star-shaped copolymers were characterized using UV–vis spectrum, DLS, TEM and FTIR. It confirmed that PDMAEMA exhibited the reducing property unless pH was above 7. The Ag NPs were sphere-like with a diameter of 10–20 nm, which was independent of the architecture of the copolymer and AgNO₃ concentration. Furthermore, the catalytic activity of these Ag NPs was investigated by monitoring the reduction of p-nitrophenol (4-NP) by NaBH₄. The result showed that the Ag NPs formed by coordination reduction can be effectively applied in catalytic reaction.

Synthesis of star-shaped PCL-based copolymers via one-pot ATRP and their self-assembly behavior in aqueous solution

Co-reporter:Xiujuan Huang;Meidong Lang

Macromolecular Research 2012 Volume 20( Issue 6) pp:597-604

Publication Date(Web):2012 June

DOI:10.1007/s13233-012-0082-6

A series of star-shaped poly(ɛ-caprolactone) (PCL)-based diblock and triblock copolymers containing 2-(dimethylamino)ethyl methacrylate (DMAEMA or DMA) and oligo(ethylene glycol)monomethyl ether methacrylate (OEGMA or OEG) were synthesized by one-pot atom transfer radical polymerization (ATRP) using a sixarm PCL-based macroinitiator. The precursor and the resultant copolymers were analyzed via proton nuclear magnetic resonance spectra (1H NMR) and size exclusion chromatography (SEC). The monomer reactivity ratios for DMAEMA (r1) and OEGMA (r2) were estimated to be near unity and r1×r2=1, which indicates the random distribution of the monomers in the final copolymers. Self-assembly behavior of these copolymers was investigated by fluorimetry, 1H NMR, dynamic light scattering (DLS), transmission electronic microscopy (TEM), potentiometric titrations, and zeta potential measurements. The results suggested that the star copolymers were responsive to salinity depending on their composition and structure.

R-RAFT approach for the polymerization of N-isopropylacrylamide with a star poly(-caprolactone) core

Co-reporter:Qingqing Bian;Meidong Lang

Journal of Polymer Science Part A: Polymer Chemistry 2012 Volume 50( Issue 3) pp:571-580

Publication Date(Web):

DOI:10.1002/pola.25066

Abstract

Reversible addition-fragmentation chain transfer (RAFT) polymerization is a more robust and versatile approach than other living free radical polymerization methods, providing a reactive thiocarbonylthio end group. A series of well-defined star diblock [poly(ε-caprolactone)-b-poly(N-isopropylacrylamide)]₄ (SPCLNIP) copolymers were synthesized by R-RAFT polymerization of N-isopropylacrylamide (NIPAAm) using [PCL-DDAT]₄ (SPCL-DDAT) as a star macro-RAFT agent (DDAT: S-1-dodecyl-S′-(α, α′-dimethyl-α″-acetic acid) trithiocarbonate). The R-RAFT polymerization showed a controlled/“living” character, proceeding with pseudo-first-order kinetics. All these star polymers with different molecular weights exhibited narrow molecular weight distributions of less than 1.2. The effect of polymerization temperature and molecular weight of the star macro-RAFT agent on the polymerization kinetics of NIPAAm monomers was also addressed. Hardly any radical–radical coupling by-products were detected, while linear side products were kept to a minimum by careful control over polymerization conditions. The trithiocarbonate groups were transferred to polymer chain ends by R-RAFT polymerization, providing potential possibility of further modification by thiocarbonylthio chemistry. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Thermoresponsive biotinylated star amphiphilic block copolymer: Synthesis, self-assembly, and specific target recognition

Co-reporter:Qingqing Bian, Yan Xiao, Meidong Lang

Polymer 2012 Volume 53(Issue 8) pp:1684-1693

Publication Date(Web):3 April 2012

DOI:10.1016/j.polymer.2012.02.031

A novel star amphiphilic block copolymer star poly(ε-caprolactone)-b-poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide)-DDAT [SPCL-b-P(NIPAAm-co-DMAAm)-DDAT] (DDAT: S-1-dodecyl-S′-(α,α′-dimethyl-α″-acetic acid)trithiocarbonate) was synthesized by combination of ring-opening polymerization (ROP) and reversible addition-fragment chain transfer (RAFT) polymerization. DDAT-terminated groups were further transformed into hydroxyl groups by one-pot strategy for aminolysis of DDAT and Michael addition reaction of an α,β-unsaturated ester of 2-hydroxyethyl acrylate (HEA). Biotinylated star copolymer SPCL-b-P(NIPAAm-co-DMAAm)-Biotin was obtained by coupling of biotin to the hydroxyl-terminated star copolymer using carbodiimide coupling chemistry. These star copolymers with DDAT, hydroxyl, and biotin end groups were capable of self assembling into core–shell structural micelles in aqueous solution. The variation of end groups significantly affected the micellar characters, such as hydrodynamic diameter (Dh), critical micellar concentration (CMC), and lower critical solution temperature (LCST). Biotinylated micelle exhibited a phase transition at 41.4 °C. The amount of biotin on the micelle surface as well as the specific recognition between biotinylated micelle and avidin was determined by 4′-hydroxyazobenzene-2-carboxylic acid/avidin (HABA/avidin) binding assay and dynamic light scattering (DLS). In addition, the biotinylated star copolymer displayed good biocompatibility according to a preliminary cytotoxicity study. The novel polymeric micelle with biodegradability, thermoresponse, and specific target recognition was expected to be a promising polymeric carrier material for targeted drug delivery.

Self-assembly of pH-sensitive mixed micelles based on linear and star copolymers for drug delivery

Co-reporter:Xiujuan Huang, Yan Xiao, Meidong Lang

Journal of Colloid and Interface Science 2011 Volume 364(Issue 1) pp:92-99

Publication Date(Web):1 December 2011

DOI:10.1016/j.jcis.2011.08.028

Comicellization of a star block copolymer poly(ε-caprolactone)-block-poly(diethylamino)ethyl methacrylate (S(PCL-b-PDEAEMA)) and a linear block copolymer methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) (mPEG-b-PCL) was developed to enhance the stability and lower the cytotoxicity of the micelles. The two copolymers self-assembled into the mixed micelles with a common PCL core surrounded by a mixed PDEAEMA/mPEG shell in aqueous solution. This core–shell structure was transformed to the core–shell–corona structure at high pH due to the collapse of the PDEAEMA segment. The properties of the polymeric micelles were greatly dependent on the weight ratio of the two copolymers and the external pH. As increasing the mPEG-b-PCL content, the size and the zeta potential of the mixed micelles were lowered while the pH-dependent stability and the biocompatibility were improved. Moreover, an increase in pH accelerated the release of indomethacin (IND) from the mixed micelles in vitro. These results augured that the mixed micelles could be applied as a stable pH-sensitive release system.Graphical abstractThe mixed micelles constructed from the star and linear copolymers were transformed from a core–shell structure into a core–shell–corona one with pH value.Highlights► pH-sensitive mixed micelles were readily formed by comicellization of two copolymers. ► The mixed micelles could be kept stable in wide pH range. ► The mixed micelles exhibited low cytotoxicity and high positive zeta potential. ► An increase in pH accelerated the release of drug from mixed micelles in vitro.

Organometallic and enzymatic catalysis for ring opening copolymerization of -caprolactone and 4-methyl--caprolactone

Co-reporter:Cui Wang;Andreas Heise;Meidong Lang

Journal of Polymer Science Part A: Polymer Chemistry 2011 Volume 49( Issue 24) pp:5293-5300

Publication Date(Web):

DOI:10.1002/pola.25007

Abstract

A series of copolymers containing ε-caprolactone (CL) and 4-methyl-ε-caprolactone (MeCL) were synthesized by ring-opening polymerization (ROP) using Tin(II) bis(2-ethylhexanoate)(Sn(Oct)₂) or Novozym 435 as catalyst. The molecular structure and weight of copolymers were determined by nuclear magnetic resonance (NMR) and size exclusion chromatography (SEC), respectively. Our kinetic study showed that the monomer reactivity ratios for CL (r₁) and MeCL (r₂) using Sn(Oct)₂ as catalyst were estimated to be near unity and r₁ × r₂ = 1, indicating the random distribution of the monomers in the final copolymer. The results of DSC and XRD consistently indicated that the copolymers were inclined to be amorphous with the increasing of MeCL fraction. Microspheres were prepared from copolymers and characterized by SEM. The preliminary degradability and biocompatibility studies on these copolymers were also assessed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Reversible thermo-sensitivity induced from varying the hydrogen bonding between the side residues of rationally designed polypeptides

Co-reporter:Hong Liu, Yan Xiao, Heng Xu, Yebin Guan, Jun Zhang and Meidong Lang

Chemical Communications 2015 - vol. 51(Issue 50) pp:NaN10177-10177

Publication Date(Web):2015/05/13

DOI:10.1039/C5CC03017J

A highly stretchable bioelastomer prepared by UV curing of liquid-like poly(4-methyl-ε-caprolactone) precursors

Co-reporter:Yan Xiao, Sihuan Lang, Miaomiao Zhou, Jing Qin, Rui Yin, Jingming Gao, Andreas Heise and Meidong Lang

Journal of Materials Chemistry A 2017 - vol. 5(Issue 3) pp:NaN603-603

Publication Date(Web):2016/12/06

DOI:10.1039/C6TB02507B