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Expression of concern for ‘Natural steroid-based cationic copolymers cholesterol/diosgenin-r-PDMAEMAs and their pDNA nanoplexes: impact of steroid structures and hydrophobic/hydrophilic ratios on pDNA delivery’ by Zhao Wang et al., RSC Adv., 2021, 11, 19450–19460, DOI: https://doi.org/10.1039/D1RA00223F.

Crosslinked polymer nanomaterials have attracted great attention due to their stability and highly controllable drug delivery; herein, a series of well-defined amphiphilic PDPA-b-P(NMS-co-OEG) diblock terpolymers (P1–P3) were designed and prepared via RAFT polymerization and were self-assembled into non-cross-linked (NCL) nanomicelles, which were further prepared into shell-cross-linked (SCL) micelles via cystamine-based in situ shell cross-linking. Using P3 as an optimized polymer, SCL-P3 micelles were prepared, which demonstrated remarkable pH/redox-dual responsive behaviour. For drug delivery, camptothecin (CPT)-loaded SCL-P3 micelles were prepared and showed much higher CPT-loading capability than their NCL-P3 counterparts. Notably, the SCL-P3 micelles showed good synergistic pH/redox-dual responsive CPT release properties, making them potential “smart” nanocarriers for drug delivery.

Using natural-based lipids to construct biocompatible, controllable and efficient nanocarriers and elucidating their structure-function relationships, was regarded as an important area for creating sustainable biomaterials. Herein, we utilized two natural steroids: cholesterol and diosgenin (bearing different hydrophobic tails) as the building blocks, to synthesize a series of natural steroid-based cationic random copolymers PMA6Chol

Various three-dimensional TiO2 hollow structures have attracted strong scientific and technological attention due to their excellent properties. 3D hierarchical TiO2 hollow nanocubes (TiO2-HNBs) are not good candidates for industrial photocatalytic applications due to their large energy gap which is only activated by UV light. Herein, visible-light-responsive carbon doped and coated TiO2-HNBs (C@TiO2-HNBs) with a dominant exposure of {001} facets have been prepared via a template-engaged topotactic transformation process using facile one-step solvothermal treatment and a solution containing ethanol, glucose and TiOF2. The effects of reaction time and glucose/TiOF2 mass ratio on the structure and performance of C@TiO2-HNBs were systematically studied. We found that glucose played an important role in providing H2O during the topological transformation from self-templated TiOF2 cubes into 3D hierarchical TiO2 hollow nanocubes versus dehydration reactions, where its main function was as a carbon source. Coated carbon was deposited predominantly on the surface as sp2 graphitic carbon in extended p conjugated graphite-like environments, and doped carbon mainly replaced Ti atoms in the surface lattice to form a carbonate structure. The results were confirmed using TEM SEM, EDS, XRD, FT-IR, XPS and Raman spectroscopic studies. The C@TiO2-HNBs achieved greatly improved RhB photodegradation activity under visible light irradiation. The catalyst prepared with glucose/TiOF2 at a mass ratio of 0.15 (T24-0.15) showed the highest photodegradation rate of 96% in 40 min, which is 7.0 times higher than those of the TiO2-HNBs and P25. This new synthetic approach proposes a novel way to construct carbon hybridized 3D hierarchical TiO2 hollow nanocubes by combining two modification methods, “element doped” and “surface sensitized”, at the same time.

A series of diblock amphiphilic glycopolypeptide analogues poly(6-O-methacryloyl-D-galactopyranose)-SS-poly(γ-benzyl-L-glutamate) (PMAgala-SS-PBLG) with well-defined and tunable structure, and redox-responsive disulfide linkage were prepared through a combination of modulated reactions including RAFT polymerization, ring-opening polymerization, “click” coupling reaction and following TFA-mediated deprotection, and a non-disulfide analogue PMAgala27-CC-PBLG30 was prepared as a control. Molecular structures of the above prepared PMAgala-b-PBLG glycopolypeptide analogues were further characterized and their self-assembly properties were examined. The glycopolypeptide analogues were able to form stabilized micelles (with α-helix PBLG cores) and the uniform-sized PMAgala-SS-PBLG micelles exhibited obvious redox-responsive features in the presence of glutathione (GSH), whereas the non-disulfide control did not show such change. For biological applications, the lectin recognition properties, doxorubicin (DOX) delivery manner and human hepatoma cell receptor targeting capabilities were further evaluated. The results illustrated that the PMAgala-b-PBLG glycopolypeptide analogues might serve as redox-responsive, highly biocompatible multifunctional biomaterial platforms for practical applications.

Developing new amphiphilic polymers with natural product moieties has been regarded as a promising way to achieve biocompatibility and certain biological functions. In prior work, we developed some natural (l)-arginine modified cationic polymers (PAHMAA-Rs) as cationic gene carriers. For the sake of continuing optimize the gene delivery performance, herein, a new series of (l)-arginine and (l)-histidine co-modified cationic poly (ω-aminohexyl methacrylamide)s (PAHMAA-R-H) were synthesized and characterized with 1H NMR, GPC-SLS and FT-IR. Their proton buffering capacities were studied by acid-base titration assay. pDNA binding affinity and self-assembly properties of the polyplexes were analyzed by agarose gel retardation assay, DLS and AFM, respectively. In vitro cytotoxicity of the PAHMAA-R-H was determined by MTT and LDH assays in H1299 cells, the gene transfection efficacy and intracellular uptake capability were evaluated by luciferase assay and FACS, respectively. Moreover, the endocytosis pathways and intracellular distribution of the polyplexes were investigated by using specific endocytic inhibitors and fluorescent co-localization techniques. The results demonstrated that co-modification of (l)-arginine and (l)-histidine onto the PAHMAA polymer could enhance proton buffering capacity, shield surface charge, decrease cytotoxicity, and improve gene transfection efficiency and serum-compatibility. Moreover, the gene transfection and intracellular uptake behaviors were disclosed strongly rely on the (l)-arginine/(l)-histidine modification ratios. The polyplexes tend to be internalized through caveolae-mediated endocytosis gateway and localized with endosomes/lysosomes in H1299 cells. Notably, among the polymers, the PAHMAA-R18-H6 exhibited remarkable gene delivery efficiency and serum compatibility, which made it promising gene transfection agent for practical application.

Crosslinked polymer nanomaterials have attracted great attention due to their stability and highly controllable drug delivery; herein, a series of well-defined amphiphilic PDPA

A new series of cationic block copolymers PHML-b-PMAGal and statistical copolymers P(HML-st-MAGal) with pendant natural galactose and (L-)-lysine moieties were prepared via RAFT (reversible addition–fragmentation chain-transfer) polymerization. The block/statistical copolymers showed a high plasmid DNA binding affinity (N/P < 2) and the as-formed polyplexes were spherical nanoparticles with the average size of 100–300 nm and surface zeta potentials of +30.2 to +46.3 mV. The cytotoxicity and gene transfection efficacy of the PHML-b-PMAGal and P(HML-st-MAGal) vectors strongly depend on the polymer architectures (block/statistical) and the galactose content. Notably, the statistical copolymer P(HML40-st-MAGal4) with 4.8% galactose content showed the highest gene transfection efficiency among the synthesized cationic polymers, 6.8-fold higher than that of the “gold standard” bPEI-25k in the presence of 10% FBS (fetal bovine serum) in various cell lines. An intracellular uptake mechanism (with 10% FBS) study demonstrated that the P(HML40-st-MAGal4)/pDNA polyplexes entered H1299 cells mainly through caveolae-mediated endocytosis and microtubule-dependent endocytosis pathways. Moreover, the fluorescence imaging study showed that the P(HML40-st-MAGal4)/pDNA polyplexes possessed an obvious “lysosomal escaping” effect that led to efficient pDNA release, which might interpret the fact of the significant increase of the related gene transfection efficiency. Moreover, it could be anticipated that the P(HML40-st-MAGal4) cationic glycopolymer might be employed as a low toxic, highly efficient and serum-compatible gene carrier for practical applications.

In this work, a series of diblock terpolymer poly(6-O-methacryloyl-D-galactopyranose)-b-poly(methacrylic acid-co-6-cholesteryloxy hexyl methacrylate) amphiphiles bearing attached galactose and cholesterol grafts denoted as the PMAgala-b-P(MAA-co-MAChol)s were designed and prepared, and these terpolymer amphiphiles were further exploited as a platform for intracellular doxorubicin (DOX) delivery. First, employing a sequential RAFT strategy with preliminarily synthesized poly(6-O-methacryloyl-1,2:3,4-di-O-isopropylidene-d-galactopyranose) (PMAIpGP) macro-RAFT initiator and a successive trifluoroacetic acid (TFA)-mediated deprotection, a series of amphiphilic diblock terpolymer PMAgala-b-P(MAA-co-MAChol)s were prepared, and were further characterized by NMR, Fourier transform infrared spectrometer (FTIR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and a dynamic contact angle testing instrument (DCAT). In aqueous media, spontaneous micellization of the synthesized diblock terpolymer amphiphiles were continuously examined by critical micellization concentration assay, dynamic light scattering (DLS), and transmission electron microscopy (TEM), and the efficacies of DOX loading by these copolymer micelles were investigated along with the complexed nanoparticle stability. Furthermore, in vitro DOX release of the drug-loaded terpolymer micelles were studied at 37 °C in buffer under various pH conditions, and cell toxicities of as-synthesized diblock amphiphiles were examined by MTT assay. Finally, with H1299 cells, intracellular DOX delivery and localization by the block amphiphile vectors were investigated by invert fluorescence microscopy. As a result, it was revealed that the random copolymerization of MAA and MAChol comonomers in the second block limited the formation of cholesterol liquid-crystal phase and enhanced DOX loading efficiency and complex nanoparticle stability, that ionic interactions between the DOX and MAA comonomer could be exploited to trigger efficient DOX release under acidic condition, and that the diblock terpolymer micellular vector could alter the DOX trafficking in cells. Hence, these suggest the pH-sensitive PMAgala-b-P(MAA-co-MAChol)s might be further exploited as a smart nanoplatform toward efficient antitumor drug delivery.

In this study, a series of diblock glycopolymers, poly(6-O-methacryloyl-d-galactopyranose)-b-poly(6-cholesteryloxyhexyl methacrylate) (PMAgala-b-PMAChols), with cholesterol/galactose grafts were prepared through a sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and deprotection process. The glycopolymers could self-assemble into aggregates with various morphologies depending on cholesterol/galactose-containing block weight ratios, as determined by transmission electronic microscopy (TEM) and dynamic laser light scattering (DLS). In addition, the lectin (Ricinus communis agglutinin II, RCA120) recognition and bovine serum albumin (BSA) adsorption of the PMAgala-b-PMAChol aggregates were evaluated. The SK-Hep-1 tumor cell inhibition properties of the PMAgala-b-PMAChol/doxorubicin (DOX) complex aggregates were further examined in vitro. Results indicate that the PMAgala-b-PMAChol aggregates with various morphologies showed different interaction/recognition features with RCA120 and BSA. Spherical aggregates (d ≈ 92 nm) possessed the highest RCA120 recognition ability and lowest BSA protein adsorption. In addition, the DOX-loaded spherical complex aggregates exhibited a better tumor cell inhibition property than those of nanofibrous complex aggregates. The morphology-variable aggregates derived from the amphiphilic glycopolymers may serve as multifunctional biomaterials with biomolecular recognition and drug delivery features.

Using renewable and biocompatible natural-based resources to construct functional biomaterials has attracted great attention in recent years. In this work, we successfully prepared a series of steroid-based cationic lipids by integrating various steroid skeletons/hydrophobes with (l-)-arginine headgroups via facile and efficient synthetic approach. The plasmid DNA (pDNA) binding affinity of the steroid-based cationic lipids, average particle sizes, surface potentials, morphologies and stability of the steroid-based cationic lipids/pDNA lipoplexes were disclosed to depend largely on the steroid skeletons. Cellular evaluation results revealed that cytotoxicity and gene transfection efficiency of the steroid-based cationic lipids in H1299 and HeLa cells strongly relied on the steroid hydrophobes. Interestingly, the steroid lipids/pDNA lipoplexes inclined to enter H1299 cells mainly through caveolae and lipid-raft mediated endocytosis pathways, and an intracellular trafficking route of “lipid-raft-mediated endocytosis→lysosome→cell nucleic localization” was accordingly proposed. The study provided possible approach for developing high-performance steroid-based lipid gene carriers, in which the cytotoxicity, gene transfection capability, endocytosis pathways, and intracellular trafficking/localization manners could be tuned/controlled by introducing proper steroid skeletons/hydrophobes. Noteworthy, among the lipids, Cho-Arg showed remarkably high gene transfection efficacy, even under high serum concentration (50% fetal bovine serum), making it an efficient gene transfection agent for practical application.

In this study, we constructed a visible model for drug/gene dual delivery. Firstly, we prepared a series of pyrene fluorophore bearing cationic amphiphiles (Py-amines), which could be further employed as amphiphilic gene carriers and antitumor polyamine drug models. Then, the Py-amines fluorescent amphiphiles were utilized to bind/load plasmid DNA via electrostatic interactions to form nano-sized particles in aqueous solution. The average size, zeta potential and morphology of the self-assembled Py-amines/pDNA complexes were found to be largely dependent on the molecular structures of Py-amines amphiphiles. Moreover, the Py-amines and their pDNA complexes showed an evident cell proliferation inhibition capability in H1299 (human lung cancer) cells. Notably, the lysosomal localization of the Py-amines/pDNA complexes could be directly visualized using fluorescence microscopy in vitro. In summary, this current study could provide new and visible approach to design polyamine-based anti-tumor drug/plasmid DNA dual delivery systems, which could facilitate a greater understanding of the intracellular trafficking/localization of polyamine-based cationic gene/drug payloads.

A new nanoparticle/block copolymer (NP/BCP) hybrid material combining the unique properties of BCP poly(styrene)b-poly(D-lactide) (PS-b-PDLA) and inorganic NP quantum dots CdSe was developed. A systematic study on the microphase separation of a series of PS-b-PDLAs by small-angle X-ray scattering showed that the degree of order of the separated microdomains depended on the initial state of the BCP and the measurement temperature and can be improved through isothermal crystallization of PDLA, thermal annealing and shear field etc. Incorporating a small amount of NPs into the BCP matrix can improve the mobility of the polymer chains and thus promote self-assembly of the BCP, which leads to hierarchically ordered structures. Excess NPs, however, cannot be completely incorporated into the PDLA domains, resulting in the phase transformation of the BCP, destruction of the ordered structure and even macroscopic phase separation due to the aggregation of NPs. An important observation is that stereocomplexation between PDLA and poly(L-lactide) could provide a driving force to promote microphase separation of the BCP. The strategy presented in the current work has potential applications for developing highly ordered NP/BCP hybrid materials. © 2014 Society of Chemical Industry

In the present work, new amphiphilic macroporous polymeric adsorbent (AMPA) membranes for LDL-apheresis were prepared by 60Co γ-ray irradiation-induced grafting copolymerization of polypropylene (PP) nonwoven fabric with acrylic acid, followed by bonding cholesterol through linkers of different length. The new AMPA membranes were characterized by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscope (SEM), and contact angle microscopy. Static adsorption and hemo-perfusion tests show these new adsorbents could efficiently remove LDL from human plasma. Meanwhile, the AMPA displayed good adsorption capacity for triglyceride (TG) as well. The static adsorption performance of the AMPA membranes depends on the length of linker. In addition, a balance between the amount of bonded cholesterol and remaining carboxyl group was found necessary to reach the optimal adsorption performance. The best result was achieved by the AMPA membrane PA15C6−3, by which 62.8 ± 3.8 μg of LDL-C, 16.5 ± 0.71 μg of HDL-C, 132.4 ± 3.0 μg of TG are removed from human plasma per square centimeter. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 52–61, 2015.

In this work, we prepared a series of cholesterol-based cationic (Cho-cat) lipids bearing cholesterol hydrophobe, natural amino acid headgroups (lysine/histidine) and linkage (carbonate ester/ether) bonds. In which, the natural amino acid headgroups made dominant contribution to their physico-chemical and biological properties. Among the lipids, the l-lysine headgroup bearing lipids (Cho-es/et-Lys) showed higher pDNA binding affinity and were able to form larger sized and higher surface charged lipoplexes than that of l-histidine headgroup bearing lipids (Cho-es/et-His), they also demonstrated higher transfection efficacy and higher membrane disruption capacities than that of their l-histidine headgroup bearing counterparts. However, compared to the contributions of the headgroups, the (carbonate ester/ether) linkage bonds showed much less affects. Besides, it could be noted that, Cho-es/et-Lys lipids exhibited very high luciferase gene transfection efficiency that almost reached the transfection level of "gold standard" bPEI-25k, made them potential transfection reagents for practical application. Moreover, the results facilitated the understanding for the structure-activity relationship of the cholesterol-based cationic lipids, and also paved a simple and efficient way for achieving high transfection efficiency by modification of suitable headgroups on lipid gene carriers.

The development of new non-viral gene vectors with the advantages of low cytotoxicity and high gene transfection efficiency is a recent trend in gene therapy. In this work, we developed a series of termini-modified mPEG-dendritic poly-(l)-lysine cationic diblock copolymers (mPEG5k-DPL4-CG) by coupling various cationic groups to the dendritic skeleton. Their molecular structures were characterized by (1)H NMR, and the buffering capacities were measured by acid titration. The plasmid DNA (pDNA) binding affinities of the mPEG5k-DPL4-CG copolymers were investigated by EB displacement and agarose gel retardation assay, and the average particle size and surface charge of the polyplexes were analyzed by dynamic light scattering. Cytotoxicity and in vitro gene transfection were evaluated in several cell lines in the presence and absence of serum by the luciferase expression assay. The results indicated that the low molecular weight polyethylenimine (PEI800) termini-modified copolymer, mPEG5k-DPL4-PEI800, possessed high pDNA binding affinity, low cytotoxicity, and high gene transfection capability which were maintained in the presence of serum (10% FBS). It is worth noting that the gene delivery efficiency of the dendritic poly-(l)-lysine gene vector was enhanced by termini modification of suitable cationic blocks. The low cytotoxicity and serum-resistance properties of mPEG5k-DPL4-PEI800 make it a potential long-circulating gene vector in gene therapy applications.

In the present work, a new porous low density lipoprotein (LDL) adsorbent membrane is prepared by 60Co γ-ray irradiation-induced grafting copolymerization of polypropylene (PP) non-woven fabric with acrylic acid, followed by immobilizing heparin covalently. The amount of carboxyl group and heparin on the resultant PP non-woven fabric is determined by titration and colorimetry, respectively. The new adsorbent membrane is characterized by attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscope, and contact angle microscopy. Static adsorption and hemoperfusion tests indicate this new adsorbent can efficiently and selectively remove LDL from human plasma. Meanwhile, good adsorption of triglyceride (TG) is also obtained. The best result is achieved by the adsorbent membrane P0.45-A15-H, where 33.3 ± 2.9 µg of LDL-C, 14.7 ± 1.9 µg of high density lipoprotein cholesterol (HDL-C), 64.9 ± 4.3 µg of total cholesterol (TC), and 202.4 ± 5.7 µg of TG are removed from human plasma per square centimeter. Hemocompability and toxicity tests show this new adsorbent membrane has good blood compatibility and low toxicity. Considering the adsorbent performance, safety, low cost, and simple preparation, this new adsorbent membrane has potential clinical application for removal of LDL. Copyright © 2013 John Wiley & Sons, Ltd.

In this work, we present the preparation of water-soluble poly(methacrylate)s with pendant cationic L-lysines PHMLs(6-30 K). Plasmid DNA binding affinity as well as particle sizes and zeta potentials of the polyplexes were examined for these PHML vectors, and their cytotoxicities were assayed with HeLa cells by CCK-8 and lactate dehydrogenase kits. Gene transfection efficacy and intracellular uptake of the polyplexes by the PHML vectors were also studied with HeLa cells. As a result, it was revealed that the low cytotoxic PHMLs tended to exhibit gene transfection efficiencies significantly higher than those of the linear structural PLL (15-30 K) control, in particular the molecular weight of a PHML vector remarkably influenced its pDNA binding affinity, transfection efficacy and intracellular uptake of the polyplexes.

This work presents a new series of polycationic nanoparticles of ( l-)-lysine conjugated amphiphilic triblock copolymer poly(hydroxyletheyl methacrylate-L-lysine)- b-poly(L-lactide)- b-poly(hydroxyletheyl methacrylate-L-lysine)s (PHML- b-PLLA- b-PHML) as potent low cytotoxic vectors for intracellular plasmid DNA delivery. First, the triblock PHML- b-PLLA- b-PHML copolymers were prepared via a combination of metal-free controlled ring opening polymerization and successive atom transfer radical polymerization. Then the cationic PHML- b-PLLA- b-PHML nanoparticles were further prepared by solution self-assembly. The particle size, zeta potential and morphology of as-prepared PHML- b-PLLA- b-PHML nanoparticles were characterized by dynamic light scattering and atomic force microscopy, respectively. The plasmid DNA binding affinities and polyplex stabilities were separately explored by agarose gel retardation and DNase I degradation assays. Then in vitro cytotoxicity and gene transfection efficiency of the PHML- b-PLLA- b-PHML nanoparticles vectors as well as relevant polyplex endocytosis pathway were investigated with H1299 cells. It was revealed that the PHML- b-PLLA- b-PHML nanoparticles exhibited low cytotoxicity, strong plasmid DNA binding affinity, high polyplex stability and efficient plasmid DNA transfection even under serum conditions (10% FBS). Moreover, the endocytosis analysis results disclosed that the PHML30- b-PLLA- b-PHML30 nanoparticle/plasmid DNA polyplexes were predominantly involved in lipid-raft-mediated endocytosis pathway, similar to that of SV40 virus-based vectors.

Developing new functional biomaterials from biocompatible natural-based resources for gene/drug delivery has attracted increasing attention in recent years. In this work, we prepared a series of cationic nanoparticles (Diosarg-DOPE NPs) by assembly of a natural steroid diosgenin-based cationic lipid (Diosarg) with commercially-available helper lipid 1,2-dioleoyl-sn-glycero-3-phosphorethanolamine (DOPE). These cationic Diosarg-DOPE NPs were able to efficiently bind siRNA and plasmid DNA (pDNA) via electrostatic interactions to form stable, nano-sized cationic lipid nanoparticles instead of lamellar vesicles in aqueous solution. The average particle size, zeta potentials and morphologies of the siRNA and pDNA complexes of the Diosarg-DOPE NPs were examined. The in vitro cytotoxicity of NPs depends on the dose and assembly ratio of the Diosarg and DOPE. Notably, the intracellular transportation efficacy of the exogenesis siRNA and pDNA could be greatly improved by using the Diosarg-DOPE NPs as the cargoes in H1299 cell line. The results demonstrated that the self-assembled Diosarg-DOPE NPs could achieve much higher intracellular transport efficiency for siRNA or pDNA than the cationic lipid Diosarg, indicating that the synergetic effect of different functional lipid components may benefit the development of high efficiency nano-scaled gene carriers. Moreover, it could be noted that the traditional "lysosome localization" involved in the intracellular trafficking of the Diosarg and Diosarg-DOPE NPs, indicating the co-assembly of helper lipid DOPE, might not significantly affect the intracellular localization features of the cationic lipids.

Development of highly efficient nonviral gene delivery vectors still remains a great challenge. In this study, we report a new gene delivery vector based on dendrimer-entrapped gold nanoparticles (Au DENPs) with significantly higher gene transfection efficiency than that of dendrimers without AuNPs entrapped. Amine-terminated generation 5 poly(amidoamine) (PAMAM) dendrimers (G5.NH(2)) were utilized as templates to synthesize AuNPs with different Au atom/dendrimer molar ratios (25:1, 50:1, 75:1, and 100:1, respectively). The formed Au DENPs were used to complex two different pDNAs encoding luciferase (Luc) and enhanced green fluorescent protein (EGFP), respectively for gene transfection studies. The Au DENPs/pDNA polyplexes with different N/P ratios and compositions of Au DENPs were characterized by gel retardation assay, light scattering, zeta potential measurements, and atomic force microscopic imaging. We show that the Au DENPs can effectively compact the pDNA, allowing for highly efficient gene transfection into the selected cell lines as demonstrated by both Luc assay and fluorescence microscopic imaging of the EGFP expression. The transfection efficiency of Au DENPs with Au atom/dendrimer molar ratio of 25:1 was at least 100 times higher than that of G5.NH(2) dendrimers without AuNPs entrapped at the N/P ratio of 2.5:1. The higher gene transfection efficiency of Au DENPs is primarily due to the fact that the entrapment of AuNPs helps preserve the 3-dimensional spherical morphology of dendrimers, allowing for more efficient interaction between dendrimers and DNA. With the less cytotoxicity than that of G5.NH(2) dendrimers demonstrated by thiazoyl blue tetrazolium bromide assay and higher gene transfection efficiency, it is expected that Au DENPs may be used as a new gene delivery vector for highly efficient transfection of different genes for various biomedical applications.

Biodegradable poly(butylene succinate-co-terephthalate)(PBST) copolyester, with 70 mol % butylene terephthalate (BT), was melt-spun into fibers at various take-up velocities ranging from 2.0 to 4.0 km/min. The structure development and mechanical properties of the as-spun PBST fibers were intensively investigated via birefringence, wide angle X-ray diffraction (WAXD) measurement, tensile test, and cyclic stretch test. With increasing the take-up velocity, the initial tensile modulus and breaking strength of PBST fibers increased, while elongation at break decreased. These were attributed to the increasing degree of orientation and crystallinity, which were resulted from the elevating tension of spinning line at higher take-up velocity. To elucidate the effects of soft butylene succinate (BS) unit on the tensile and elastic properties of PBST fibers, poly(butylene terephthalate) (PBT) fibers were adopted as a comparison sample. The results showed that the combination of soft BS unit and hard BT unit for PBST fibers made contribution to the lower initial modulus, higher elongation at break and better elastic recovery than those of PBT fibers. Moreover, PBST fibers were found to undergo PBT-like crystal form transition from α-form to β-form crystal structure under tension load through the measurement of WAXD. A relatively wider strain region for the crystal transition of PBST fibers also endowed them with higher elastic recoverability than PBT fibers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Crystalline structure and molecular dynamics in alpha and alpha' crystals of poly(L-lactide) (PLLA) and PLLA/poly(Dlactide) (PDLA) stereocomplex (sc) crystals have been investigated by the temperature-variable FTIR and solid-state C-13 CP-MAS NMR spectroscopy. The crystal forms of polylactide (PLA) have different band frequencies, correlation field splittings in FTIR spectra and different line shapes, and resonance splittings in solid-state NMR spectra, which become more distinct with cooling to the cryogenic conditions. The well-resolved splittings in NMR resonances of alpha crystals, attributable to the crystallographically inequivalent sites within crystal unit cell, are considered to be due to the dipolar interactions related to the carbonyl, methyl, and methine groups. The splittings in FTIR bands and NMR resonances are absent in alpha' crystals, indicating the disordered conformation and loose molecular lateral packing within their crystal lattices. The significant FTIR frequency shifts of nu(C=O), nu(CH3), and nu(CH) modes during stereocomplex crystallization of PLLA/PDLA blend and the appearance of spectral splittings at cryogenic conditions suggest the coexistence of weak C-H center dot center dot O=C hydrogen bonds and dipolar interactions between PLLA and PDLA chains in the sc crystals of PLA Below the glass transition temperature (T-g), the spin lattice relaxation times of PLA with different crystalline structures increase in the order of amorphous approximate to alpha' < alpha < sc.

In this work, carbon fibers were sized with different plasticizer of sizing agent in order to improve the performances of carbon fibers and the interface of carbon fibers composites. The chemical and physical changes induced by the treatments on carbon fibers surface are examined using dynamic contact angle analysis test(DCAT) , X-ray photoelectron spectroscopy (XPS). The interfacial shear strength (IFSS) of CF/EP composites are analysised by micro-droplet test. At the same time, the wear resistance was also studied in order to understand the effect of the plasticizer of sizing agent on the carbon fibers. The study shows that the 3# sized carbon fiber has the better wetting and surface energy. XPS results reveal that the 3# samples show a significant increase in oxygen-containing groups, such as–C–OH, -COOH, -C–O–C- and -COOR. 3#sizing agent also show better interface adhesion between fibers and matrix and has better wear resistant properties.

Recently, fabrication of functional porous polymer films with patterned surface structures at the scale from nanometer to micrometer has been attracting increasing interests in material science and nanobiotechnology. In this work, we present new preparation of two series of multifunctional amphiphilic copolymers and preparation of their microporous thin films on solid substrates. First, diblock dendritic poly(l-lysine)-b-poly(l-lactide)s and triblock dendritic poly(l-lysine)-b-poly(l-lactide)-b-dendritic poly(l-lysine)s (C1-C6) were synthesized through 4-dimethylaminopyridine (DMAP)-catalyzed living ring-opening polymerization of (l-)-lactide with (l-)-lysine dendron initiators, and their structures were characterized by nuclear magnetic resonance spectrometer (NMR), gel permeation chromatography (GPC) and matrix-assisted laser desorption/ionization Fourier-transformed mass spectra (MALDI-FTMS). Employing the breath-figure (BF) fabrication strategy, thin films of the synthesized amphiphiles (C1-C6) were drop-cast, and their surface topologies were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the effects of new amphiphile structure and drop-casting parameters of amphiphile concentration, humidity and temperature on self-assembly of ordered porous surface were studied. Furthermore, the influence of surface energy of drop-casting substrates was additionally investigated. With a human cervical epithelial carcinoma cell line (HeLa), cytotoxicity of the prepared honeycomb-structured films by new amphiphile C6 was evaluated by thiazoyl-blue-tetrazolium-bromide (MTT) assay, and HeLa cell growth behavior with microporous amphiphile films as the scaffolds was also examined. It was found that tunable micropore diameter sizes and well ordered surface topologies of BF films could be achieved for the new prepared amphiphiles, and utilization of the honeycomb-like microporous films as scaffolds indicated favorable enhancement in cell proliferation. Therefore, the honeycomb-structured films by these biocompatible multifunctional amphiphiles may provide new materials as 3D-scaffold materials for potential application in tissue engineering and regeneration.

Stimuli-responsive biomaterials derived from natural products toward efficient drug/gene delivery have been attracting increasing attention in the past decade. In this work, we first designed and prepared a new series of cholesterol-disulfide lipids, namely CHOSS-N, CHOSS-N+, CHOSS-Lys and CHOSS-4N bearing cholesterol and a variety of headgroups via disulfide and carbonate bond linkages, and their molecular structures were characterized by NMR and ESI-MS. Furthermore, plasmid DNA binding affinity for these new CHOSS lipids was separately examined by ethidium bromide displacement and agarose-gel retardant assay. Average diameter sizes and surface potentials of the CHOSS/pDNA lipoplex particles prepared under various N/P charge ratios were analyzed by dynamic laser light scattering (DLS). Under 10 mm dithiothreitol (DTT), stability and disassembly of the CHOSS/pDNA lipoplex nanoparticles were investigated by agarose-gel retardant assay and atomic force microscopy (AFM). Employing a COS-7 cell line, cell viability was examined for the prepared CHOSS lipids and their pDNA lipoplexes with branched PEI-25k as the reference. Finally, COS-7 cell gene transfection efficacies with these CHOSS lipids as potential delivery vectors were investigated by luciferase and EGFP transfection assay in the absence and presence of serum, and intracellular uptake capability, trafficking and cellular localization of Cy3-labeled pEGFP-N1 DNA were studied with a flow cytometer and fluorescent microscopy with Lipofectamine™ 2000 as the control. The results demonstrated low cytotoxicity, strong pDNA binding affinity and high transgenetic efficacy for new prepared CHOSS lipids, and particularly high intracellular uptake capability and specific cellular localization of pDNA at the periphery of cell nuclei were for the first time interestingly observed for the CHOSS lipid delivery carriers. In general, these may pave a new way to utilize cholesterol, amino acids and other functional natural products to prepare efficient gene/drug delivery carriers with simple structure and low cytotoxicity.

We report on the self-assembly, in water and in bulk, of amphiphilic liquid crystal block copolymers consisting of a cholesterol-based smectic LC polymer block (PAChol) and poly(ethylene glycol) (PEG) block. Two series of block copolymers, PEG 45 - b -PAChol and PEG 114 - b -PAChol (45 and 114 are the degree of polymerization of PEG blocks) with different hydrophilic/hydrophobic weight ratios were synthesized and characterized in detail. Depending on the diblock composition, smectic polymer vesicles and/or nanofibers were formed by adding water into a dilute solution of copolymers in dioxane. If THF is used instead of dioxane as solvent, solid spherical aggregates were obtained upon water addition for PEG 45 - b -PAChol series, while macroscopic precipitation occurred for PEG 114 - b -PAChol series. The mesomorphic and microphase segregation structures of the block copolymers in bulk were studied by X-ray scattering, DSC and POM. The interdigital smectic A (SmA d ) phase with a lamellar period of 4.25 nm was detected in all block copolymers. For PEG 114 - b -PAChol 5 (PEG/PAChol weight ratio = 66/34) and PEG 114 - b -PAChol 12 (45/55), lamellar type of microphase segregation was observed.

Novel amphiphilic chitosan-g-poly(epsilon-caprolactone)-(g-poly(2-(2-methoxyethoxy)ethyl methacrylate)co-oligo(ethylene glycol) methacrylate) (CS-g-PCL(-g-P(MEO(2)MA-co-OEGMA))) copolymers with double side chains of PCL and P(MEO(2)MA-co-OEGMA) were synthesized via combination of ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP) and click chemistry. The molar ratio of PCL and P(MEO(2)MA-co-OEGMA) was varied through variation of the feed ratio and the coupling efficiency of click chemistry is comparatively high. The graft copolymers can assemble into spherical micelles. The micelles show thermosensitive properties and the lower critical solution temperatures (LCSTs) were influenced by CS chains and the ratio of PCL and P(MEO(2)MA-co-OEGMA) side chains. Moreover, the micelles can reversibly swell and shrink in response to the change of temperatures. Furthermore, the micelles present obvious fluorescence and the fluorescent intensity can be adjusted by altering the temperatures. The investigation of doxorubicin release from the micelles indicated that the release rate of the drug could be effectively controlled by altering the temperatures. (C) 2010 Elsevier Ltd. All rights reserved.

A new series of triblock [dendritic poly(L-lysine)]-block-PLLA-block-[dendritic poly(L-lysine)]s (DL(2) -PLLA-DL(2) ) with PLLA block lengths of 11.5-26.5 and double 2-generation PLL dendrons DL(2) as model cationic amphiphiles were synthesized and characterized. Their CAC, self-aggregation and plasmid DNA binding affinities in pure water and PBS were studied. The PLLA block length dependence of particle size, morphology and ξ potential for organized pDNA/amphiphile polyplex aggregates were examined. Finally, toxicities of these DL(2) -PLLA-DL(2) amphiphiles and their polyplexes were assayed by MTT with HeLa, SMMC-7721 and COS-7 cells, and COS-7 cell luciferase and eGFP gene transfection efficacies with these amphiphiles as the delivery carriers were investigated.

Taxonomic studies on Acrodictys and related genera in China has yielded 13 taxa including a new species, Acrodictys porosiseptata sp. nov., characterized by indeterminate conidiophores with successive lageniform proliferations and muriform conidia usually with 4–5 parallel transverse septa, several longitudinal or oblique septa, and the presence of conspicuous septal pores. Acrodictys atroapicula, A. irregularis, A. micheliae, Pseudoacrodictys deightonii, and Rhexoacrodictys fuliginosa are newly recorded for China. Descriptions and illustrations of all taxa are provided, and similarities or differences with morphologically close taxa are discussed.

In this work, we prepared a novel series of cationic amphiphiles denoted as the Py-cations (Py-Gly, Py-Ala, Py-Cap, Py-G 1 -Lys and Py-G 2 -Lys) bearing fluorescent pyrene and various hydrocarbon linkers between the pyrene hydrophobe and cationic block. Employing these new cationic amphiphiles with pyrene as the fluorescent probe, the interactions between these Py-cations and plasmid DNA (pDNA) in distilled water and 0.1 M PBS buffer solution have been explored by means of UV-vis and fluorescent spectrometers, and ethidium bromide dye displacement and agarose-gel retardant assays were also implemented to evaluate their pDNA binding affinities in aqueous solution. Furthermore, the average sizes and morphologies of self-assembled Py-cation/ pDNA lipoplex aggregates were examined by dynamic laser light scattering (DLS) and atomic force microscopy (AFM). It was found that these fluorescent cationic amphiphiles showed blue fluorescence emission of pyrene probe at λ = 340 nm in distilled water while their interactions with pDNA led to new strong green emission at λ = 490 nm, and this may be due to the stacking of pyrene and new formation of excimers via the rigid pDNA templated self-assembly. It was also revealed that the binding between new Py-cations and pDNA in aqueous solution was strongly influenced by the Py-cation hydrophobicity, charges of the cation and the presence of electrolytes. With respect to the Py-cation/pDNA aggregate morphologies, very interesting 1-D hybrid nanofibers were predominantly observed by AFM for the Py-Cap/pDNA aggregates. In addition, utilizing a COS-7 cell-line, in-vitro cellular uptakes of new cationic amphiphiles with pyrene probe were studied and visualized by fluorescent microscopy. As a result, this may provide a new approach to investigate the interactions between synthetic cationic lipids and nucleic acids, and pave an alternative clue to design new organic gene delivery carriers.

In this article, biodegradable poly(butylene succinate-co-butylene terephthalate) (PBST) copolyesters with high molecular weights were synthesized by direct esterification and polycondensation route. The reaction conditions and catalytic systems were investigated in detail. Through balancing the reaction efficiency and the costs of reactants, the proper molar ratio of diol to diacid was determined. Titanium tetraisopropoxide (TTiPO) was found to be an effective catalyst both in esterification and polycondensation reaction, and its content was optimized based on the esterification ratio and amount of formed by-products. The complex reaction was determined to be the dominant catalytic reaction mechanism. By importing the additives of metal oxides coupled with TTiPO, the weight-average molecular weights of PBST increased sharply from 8.51 × 104 to 14.38 × 104, manifesting the additives promoted the polymerization reaction greatly. The enhancement of carbonyl polarization and provision of suitable reaction space arose from the metal oxides were the reasons for promoting the polymerization reaction. With respect to thermal properties, the same melting point and heat of fusion were found, while thermal stability increased with the import of additives. The result was prone to be interpreted by the higher molecular weights of PBST in the presence of additives. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Spontaneous stereocomplex aggregation of diblock poly(styrene)-b-poly(L-lactide) PS-b-PLLA/poly(D-lactide) PDLA pairs has been investigated under ambient temperature in tetrahydrofuran solution. First, diblock PS260-b-PLLA165 and PS260-b-PDLA162 bearing similar lengths of respective PLLA and PDLA blocks were synthesized through controlled atom-transfer radical polymerization of styrene, and a subsequent living ring-opening polymerization of optically pure lactides, and their structures were further characterized by nuclear magnetic resonance spectroscopy (NMR) and gel-permeation chromatography (GPC). Subsequently, new enantiomeric poly(D-lactide) stabilized core-shell fluorescent CdSe quantum dots (CdSe/PDLA QD) were designed and prepared as sensitive fluorescence labels to shed new lights on the spontaneous stereocomplex aggregation in THF, which was mediated by stereocomplexation of the PLLA and PDLA chains. Upon simply mixing two individual THF solution of diblock PS260-b-PLLA165 and HO-PDLA30-SH, spontaneous stereocomplex aggregation was studied, and the aggregated uniform spherical particles were observed by scanning electronic microscopy (SEM) to exhibit average particle diameters of 2.0 μm. Finally, utilizing the prepared CdSe/PDLA QDs as new fluorescent labels, morphologies of the spontaneous aggregates by new diblock PS260-b-PLLA165/HO-PDLA30-SH pair were for the first time directly visualized by a confocal laser scanning fluorescence microscopy (CLSFM). These results might suggest alternative ways to simply prepare functional fluorescent particles with tunable diameter sizes and would be helpful to understand the mechanism of stereocomplex particle aggregation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1393–1405, 2009

As an effort to prepare new efficient gene delivery vectors, we have recently developed and reported an amphiphilic dendritic poly(L-lysine)-b-poly(L-lactide)-b-dendritic poly(L-lysine) D(2)-PLLA-D(2) with two-generation PLL dendrons and a PLLA block. In this work, we continued to explore the roles of dendritic PLL generation in DNA binding and intracellular delivery of gene, and a new series of amphiphilic dendritic poly(L-lysine)-b-poly(L-lactide)-b-dendritic poly(L-lysine)s D(n)-PLLA-D(n) (n = 3-5) were synthesized and were structurally characterized. Furthermore, plasmid DNA binding affinity for these cationic amphiphiles was examined by agarose gel electrophoresis and fluorescence titration assay in pure water and PBS buffer solution containing 150 mM NaCl (pH = 7.4), respectively. By dynamic light scattering (DLS) and transmission electronic microscopy (TEM), the interaction and complexation in between were investigated, concerning the DNA/vector polyplex particle morphologies and zeta potentials. Utilizing a human hepatocellular carcinoma cell-line SMMC-7721, cell toxicity, and gene transfection in vitro were explored. To further improve transgene efficiency for these synthetic cationic amphiphiles as gene delivery vectors, new structural DE(n)-PLLA-DE(n) (n = 2-3) were prepared through an amino termini modification of the D(n)-PLLA-D(n) (n = 2-3) with less toxic 4,7,10,13-tetraazatridecanoic acids, and gene transfection with these DE(n)-PLLA-DE(n) (n = 2-3) was examined with an alternative human gastric carcinoma cell-line HGC-27. As a result, the high plasmid DNA binding affinity, low cytotoxicity, and much enhanced transgene efficacy suggest a new possible clue to design effective synthetic gene delivery vectors with amphiphilic skeleton and less toxic polyamine building blocks.

New, biodegradable poly( L -lactide) disulfides, PLLA-SS-PLLA, were first prepared through the DMAP-catalyzed ring-opening polymerization of L -lactide with a dihydroxyethyl disulfide initiator, and were further catalytically reduced into thiol-end-functionalized poly( L -lactide)s, HO-PLLA-SH, with a tributyl phosphine catalyst (PBu 3 ). Employing the HO-PLLA-SH as the ligand, new core-shell CdSe/PLLA quantum dots (QDs) were continuously prepared via a facile ligand-exchanging process with the CdSe/TOPO OD precursor. The chemical structures, morphologies and solvent solubility of these prepared CdSe/PLLA QDs were investigated by NMR spectroscopy, FTIR spectroscopy, XRD, TEM and excitation under either room light or UV radiation at 365 nm, demonstrating the successful ligand replacement and the new formation of core-shell CdSe/PLLA QDs (diameter:4.0 ± 0.3 nm). Finally, UV and FL results indicate the two factors of the HO-PLLA-SH ligand molecular weight and the ligand/ OD precursor feeding weight ratio were important for preparing stable and highly photoluminescent CdSe/ PLLA QDs.

Four new soluble polymers containing a 2,7-carbazole unit and a 2,1,3-benzothiadiazole unit in the main chain were synthesized by Suzuki polycondensation. Variation of the substituent groups (R) at 5-position of 2,1,3-benzothiadiazole unit resulted in different color emission of the copolymers. Thus, when R was CH3 (or H), the polymer showed yellow–green (or red) emission; whereas the polymers showed the emission from green to yellow–green, when R was CH2(CH2)5CH3 or CH2OCH(CH3)2. To investigate the nature of the color change, a Gaussian 03 program was used for estimation of the dihedral angles between a 5-R-2,1,3-benzothiadiazole unit and a 2,7-carbazole unit. The results showed that the different substituents at 5-position of 2,1,3-benzothiadiazole brought about different the dihedral angles, which gave the different conjugation levels to the polymers. Hence, the tunablity of emission color may be attributed to the different conjugation levels between 2,7-carbazole units and 5-R-2,1,3-benzothiadiazole units induced by simply changing substituent groups at 5-position of benzothiadiazole unit. Electrochemically, the copolymers exhibited a higher oxidation potential as well as the reversible reduction behavior bearing from 2,1,3-benzothiadiazole unit. To investigate the electroluminescent properties of the polymers, the nonoptimized devices were fabricated and the results showed that the electroluminescent emission wavelength was basically similar to that of the photoluminescent. All polymers showed good thermal stability with 5 wt % loss temperature of more than 296 °C. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1376–1387, 2008

In this work, the enzymatic degradation of poly(butylene succinate- co -butylene terephthalate) (PBST) copolyesters was studied using the lipase from Pseudomonas (Lipase PS ® ). The biodegradation behavior was found to strongly depend on the overall impacts of several important factors as the BT comonomer structure and molar content, thermal characteristics, morphology, the enzyme-substrate, and so forth. Further, the biodegraded residual film samples were allowed to be analyzed by means of gel permeation chromatography (GPC), proton nuclear magnetic resonance ( 1 H NMR), differential scanning calorimeter (DSC), small angle X-ray scattering (SAXS), and scanning electron microscope (SEM). On the experimental evidences, an exo-type mechanism of enzymatic chain hydrolysis preferentially occurring in the amorphous region was suggested for the PBST film samples.

In comparison with poly(9,9-dialkylfluorene)s widely used in organic optoelectronic devices, poly(9,9-dialkylfluoreneethynylene)s (PFEs) have attracted less attention partly because of their poor fluorescence quantum yield (FQY) in the solid state. In order to improve the FQY, a 1,4-bis(perfluorohexyl)benzene (BFB) unit was introduced to PFEs, and the results showed that the absolute FQY in the solid state was dependent on the mol-% of the BFB unit in the copolymers. When mol-% was 40 and 50%, respectively, the absolute FOY had greatly increased from 4.9% of PFE to 7.8 and 17.4% of the copolymers, respectively. For comparison, a 1,4-dihexylbenzene (DHB) unit was also introduced to PFE, whereas the obtained copolymer showed the absolute FQY of 3.8%, suggesting that the DHB unit was not suitable for improvement of the FQY of PFEs. Electrochemically, the PFE containing BFB units showed lower reduction potential than that of PFE. All the fluorine-containing polymers have good thermal stability.

In this study, thermal degradation and their related kinetics have been investigated mainly by means of thermal gravimetrical analyzer (TGA) under the dynamic nitrogen and air atmospheres for the chemically prepared biodegradable aliphatic–aromatic copolyesters of poly(butylene succinate-co-butylene terephthalate) (PBST). To further shed new lights on the comonomer molar composition and experimental condition dependences of thermal degradation kinetics, the as-known Friedman model was at first applied to quantitatively evaluate the kinetic parameters in terms of activation energy (E), degradation reaction order (n) and the frequency factor (Z). The results clearly demonstrated that thermal stabilities of these PBST copolyesters were substantially enhanced with the incorporation of more rigid butylene terephthalate comonomer, and tended to be much better in nitrogen than in air. Furthermore, the Friedman, Freeman–Carroll and Chang models were concurrently employed to quantitatively evaluate the thermal degradation kinetic parameters of the PBST copolyesters in nitrogen at different heating rates of 1, 2 and 5 K/min. It was found that the thermal degradation kinetic parameters for the PBST copolyesters were strongly dependent on the heating rate and calculating models. In addition, life-time parameters of the biodegradable PBST copolyesters were first calculated to predict the maximum usable temperatures, and this would be useful for practical application of these new bio-based green plastics.

Novel metal complexes with a single catalytic site and less transesterification seem to provide alternative efficient synthetic approaches to preparing new biodegradable and biologically responsive materials with well-defined structures. In this study, we rationally designed a new category of aluminum metal complexes bearing a bulky Salen ligand and diverse steroidal alkoxy moieties to synthesize novel biodegradable aliphatic polyesters end-capped with steroidal building blocks. At first, three new aluminum metal complexes (9–11) were synthesized with good yields of 80–90%, bearing cholesterol and diosgenin derivatives as functional alkoxy moieties. By means of nuclear magnetic resonance (NMR) spectrometry, matrix-assisted laser desorption/ionization Fourier transform mass spectrometry (MALDI–FTMS), and Fourier transform infrared spectrometry, the molecular structures of 9–11 were characterized. Furthermore, new biodegradable aliphatic polyesters, poly(e-caprolactone) and poly(δ-valerolactone) end-capped with diverse steroidal moieties, were synthesized through the ring-opening polymerization of e-caprolactone and δ-valerolactone catalyzed by these new metal complexes under 100 °C in toluene, and they were also characterized by gel permeation chromatography, NMR, MALDI–FTMS, differential scanning calorimetry, and thermogravimetric analysis. Very narrow molecular weight distributions were revealed for these new polymer products, and their thermal crystallization and stability strongly depended on the degree of polymerization of the polyester building blocks and the distinct steroidal moieties. Because of the nature of the steroidal moieties, these biodegradable polymers may pave a path to new possibilities as potential biomaterials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2045–2058, 2006

In this work, new investigations on the effect of comonomer sequential structure on the thermal and crystallization behaviors and biodegradability have been implemented for the biodegradable poly(butylene succinate-co-butylene terephthalate) (PBST) as well as aliphatic poly(butylene succinate) (PBS). At first, these copolyesters were efficiently synthesized from dimethyl succinate and/or dimethyl terephthalate and 1,4-butanediol via condensation polymerization in bulk. Subsequently, their molecular weights and macromolecular chain structures were analyzed by gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy. By means of differential scanning calorimeter (DSC) and wide-angle X-ray diffractometer (WAXD), thermal and crystallization behaviors of these synthesized aromatic-aliphatic copolyesters were further explored. It was demonstrated that the synthesized copolyesters were revealed to have random comonomer sequential structures with thermal and crystallization properties strongly depending on their comonomer molar compositions, and that crystal lattice structures of the new crystallizable copolyesters shifted from the monoclinic crystal of semicrystalline PBS to triclinic lattice of the poly(butylene terephthalate) (PBT) with increasing the terephthalate comonomer composition, and the minor comonomer components were suggested to be trapped in the crystallizable component domains as defects. In addition, the enzymatic degradability was also characterized for the copolyesters film samples. (c) 2006 Wiley Periodicals, Inc.

A series of new pi-conjugated poly(aryleneethynylene)s containing a 1,3,5-triazine unit in the main chain were synthesized in yields higher than 70% by poly-condensation between dibromophenyl-1,3,5-triazine monomers and alkyl-substituted diethynylbenzene (or diethynylfluorene) comonomers with Pd(PPh3)(4) and CuI as catalysts in the presence of triethylamine. The polymers had a number-average molecular weight in the range of 5000-10,000 and showed good solubility in common organic solvents. The polymers were photolumineseent both in solutions and in the solid state. X-ray diffraction patterns of the powders of the polymers revealed that the polymers were semicrystalline. Electrochemically, the polymers appeared to be reversible under reduction. (c) 2006 Wiley Periodicals, Inc.

This study presents investigations on new approaches to novel biodegradable amphiphilic poly(L-lactide)-b-dendritic poly(L-lysine)s bearing well-defined structures. First, two new Boc-protected poly(L-lysine) dendron initiators G(2)OH 4 (generation = 2) and G(3)OH 6 (generation = 3) with hydroxyl end functional groups were efficiently derived from corresponding precursors 3 and 5 via methyl ester substitution with ethanolamine. Subsequently, two series of new diblock copolymers of poly(L-lactide)-b-dendritic Boc-protected poly(L-lysine)s (S1-S2, S3-S4) were prepared in chloroform through ring-opening copolymerization of poly(L-lactide)s with a metal-free catalyst of organic 4-(dimethylamino) pyridine (DMAP) in the presence of a corresponding new poly(L-lysine) dendron initiator. Further, molecular structures of the prepared new dendron initiators as well as those of poly(L-lactide)-b-dendritic Boc-protected poly(L-lysine)s bearing different dendron blocks and PLLA lengths were examined by means of nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), mass spectrometry (ESI-MS, MALDI-FTMS), and thermal gravimetric analysis (TGA). The results demonstrated successful formation of the synthetic precursors, functional dendron initiators, and new diblock copolymers. In addition, the very narrow molecular weight distributions (PDI = 1.10-1.14) of these poly(L-lactide)-b-dendritic Boc-protected poly(L-lysine)s further indicated their well-defined molecular structures. After the efficient Boc-deprotection for the dendron amino groups with TFA/CH(2)Cl(2), new diblock poly(L-lactide)-b-dendritic poly(L-lysine)s bearing lipophilic PLLA and hydrophilic dendritic PLL were finally prepared. It was noteworthy that the MALDI-FTMS result showed that no appreciable intermolecular chain transesterification happened during the ROP of L-lactide catalyzed by the DMAP. Moreover, self-assembly of these new biodegradable amphiphilic copolymers in diverse solvents were also preliminarily studied.

Two new soluble arylenevinylene-based polymers comprising of an electron-donating carbazole unit and an electron-accepting 2,1,3-benzothiadiazole (or fluorenone) unit in the main chain were synthesized by Heck polycondensation between 3,6-divinylene-9-decyl carbazole and 4,7-dibromo-2,1,3-benzothiadiazole (or 2,7-dibromofluorenone). In the toluene solution, a polymer with benzothiadiazole unit showed strong red photoluminescence, whereas the polymer with fluorenone unit showed white–yellow photoluminescence. The polymers had good thermal stability with 5 wt% loss temperature of more than 430 °C. Electrochemically, the polymers appeared to be reversible under reduction.

A new poly(fluorene-co-carbazole) (PFC-1) with a large substituent group (ADN, a naphthalene-anthracene derivative moiety) at the 9-position of carbazole was synthesized. Compared with poly(fluorene-co-carbozole)s that have an alkyl substituent group at the 9-position of the carbazole, the UV-vis absorption (or photoluminescent emission) peaks of PFC-1 are in almost the same position both in solution and in the solid state, whereas films of the former give peaks at longer wavelengths than those in solution. The photoluminescent (PL) spectra of PFC-1 indicate that the attachment of ADN to the poly(fluorene-co-carbazole)s gives rise to an efficient blue emission from non-aggregated ADN. There is no difference evident between PFC-1 and other reported poly(fluorene-co-carbazole)s in PL quantum yield, thermostability, and electrochemical behavior, which suggests that PPC-1 is an efficient blue emitter.

In our previous study [J. Yang, L. Jia, L. Yin, J. Yu, Z. Shi, Q. Fang, A. Cao, Macromol. Biosci. 2004, 4, 1092.], new biodegradable copolymers of diblock methoxy poly(ethylene glycol)-block-poly(epsilon-caprolactone) and methoxy poly(ethylene glycol)-block-poly(delta-valerolactone), and triblock poly(epsilon-caprolactone)-block-poly(ethylene glycol)-block-poly(epsilon-caprolactone) and poly(delta-valerolactone)-block-poly(ethylene glycol)-block-poly(delta-valero-lactone) bearing narrow molecular weight distributions and well-defined block architectures were reported to be prepared with our original aluminum metal complex templates. This work will continue to report new investigations on their water solubility, and reversible thermal responsive micellization and solution to gel transition in distilled water. Among the new synthesized copolymers (P1-P23), seven diblock or triblock samples (P3, P6, P7, P11, P12, P19, and P21) with higher hydrophilic building block populations were revealed to be water soluble under ambient temperature. By means of UV spectrophotometer attached with a thermostat, important parameters as critical micellization mass concentrations (CMCs) and critical micellization temperatures (CMTs) were characterized for these new amphiphile dilute aqueous solution with the aid of an lipophilic organic dye probe of 1,6-diphenyl-1,3,5-hexatriene (DPH). Furthermore, the critical gelation temperatures (CGTs) were simultaneously investigated for these water-soluble block copolymers via a tube tilting method. It was found that the CMC, CMT, and CGT were strongly affected by the population and nature of the hydrophobic building blocks, and a higher hydrophobicity of the new amphiphilic block copolymer finally led to lower CMC and CMT, and higher CGT. In addition, the salts of KBr and NaCl were found to play as a salt-out effect on the solution to gel transition for the diblock P6 and triblock P11, exhibiting an interesting tunable gelation temperature close to 35-42 degrees C. These results will pave new possibility for the synthesized block structural amphiphiles as potential biomaterials to be applied in vivo.