聚(乳酸-羟基乙酸)共聚物涂层的释药性能

以乙酸乙酯为溶剂,配制聚(乳酸-羟基乙酸)共聚物(PLGA)雷帕霉素溶液,利用滴涂法在316L不锈钢表面制备PLGA载药涂层。于37℃磷酸盐缓冲液(PBS)中进行体外动态药物释放,并用紫外-可见分光光度计测定药物释放量。结果表明:PLGA涂层中PLGA分子量越小,羟基乙酸(GA)含量越高,药物释放越快;药物释放量与滴涂量呈线性关系,药物释放率与滴涂量的倒数呈线性关系;涂层中药物含量增加,其释放量也随之增加,而药物释放率先增加后降低。     

Sorption and Swelling of Poly(D,L-lactic acid) and Poly(lactic-co-glycolic acid) in Supercritical CO2

Summary: The equilibrium sorption and swelling behavior in supercritical CO₂ of poly(D,L-lactic acid) and poly(lactic-co-glycolic acid) has been studied at a temperature of 35 °C and at pressures up to 200 bar. Sorption was measured through a gravimetric technique and swelling by visualization. From these data, the behavior of the different polymers can be compared. In terms of partial molar volume of CO₂ in the polymer matrix, all the polymers exhibit a behavior typical of rubbery systems. The experimental results have been modeled using the Sanchez-Lacombe equation of state, which is able to represent the actual behavior of the polymer-CO₂ systems with reasonable accuracy.     

聚乙丙交酯电纺纳米纤维膜的等离子体改性及性能研究

采用等离子体表面处理的方法, 通过正交实验设计, 以纤维膜表面引入的氮含量为响应变量, 确定了NH3等离子体改性PLGA电纺纤维膜的最佳条件, 并在PLGA纤维膜表面成功地引入了功能性氨基基团. 研究结果表明, 改性后PLGA电纺纤维膜的力学性能有所降低, 但表面亲水性明显增强.     

Sodium caseinate as a particulate emulsifier for making indefinitely recycled pH-responsive emulsions

pH-responsive emulsions are one of the simplest and most readily implementable stimuli-responsive systems. However, their practical uses have been greatly hindered by cyclability. Here, we report a robust pH-responsive emulsion prepared by utilizing pure sodium caseinate (NaCas) as the sole emulsifier. We demonstrate that the emulsification/demulsification of the obtained NaCas-stabilized emulsion can be triggered by simply changing the pH value over 100 cycles, which has never been observed in any protein-stabilized emulsion system. The NaCas-stabilized emulsion maintains its pH-responsive properties even in a saturated salt solution (NaCl ∼ 6.1 M) or seawater. We illustrate how NaCas functions in pH-responsive emulsions and show that when conventional nanoparticles such as zein protein or bare SiO₂ particles were coated with a layer of NaCas, the resulting formulated emulsions could be switched on and off over 10 cycles. The unique properties of NaCas thus enable the engineering of conventional Pickering emulsions to pH-responsive Pickering emulsions. Finally, we have integrated catalytically active gold (Au) nanoclusters (NCs) into the NaCas protein and then utilized them to produce emulsions. Remarkably, these NaCas–Au NCs assembled at the oil–water interface exhibited excellent catalytic activity and cyclability, not only in aqueous solution, but also in complicated seawater environments.

An unprecedented pH-responsive emulsion is shaped by utilizing pure sodium caseinate (NaCas) as the sole emulsifier for recyclable interfacial catalysis. This emulsion could be reversibly switched on and off over 100 cycles.     

Micelle-assisted synthesis of PANI nanoparticles and application as particulate emulsifier

Well-defined water-dispersible polyaniline (PANI) nanoparticles were synthesized by in situ chemical oxidative polymerization of aniline in the presence of an amphiphilic P(AMPS-co-VM) copolymer micelle. P(AMPS-co-VM) copolymer was prepared by the free radical polymerization of 7-(4-vinylbenzyloxyl)-4-methyl-coumarin (VM) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) which can self-assemble into micelles in aqueous solution. Here, P(AMPS-co-VM) copolymer micelle is used not only as soft template but also as acid dopant in our reaction system. The structure, size, and morphology of PANI nanoparticles were characterized by various experimental techniques. It is found that the morphology and the size of the PANI nanoparticles strongly depend on the molecular characteristics of the P(AMPS-co-VM) copolymer. The synthesized PANI nanoparticles behaved as particulate emulsifier for the stabilization of oil-in-water emulsions.     

Development and Validation of a Reverse-phase High Performance Liquid Chromatography Method for Determination of Exenatide in Poly（lactic-co-glycolic acid） Microspheres

Exenatide(synthetic exendin-4), which has been approved by the Food and Drug Administration(FDA) for the adjunctive treatment of patients with type 2 diabetes, is an incretin mimetic agent. The development and validation of a RP-HPLC method for the quantification of the exenatide in poly(lactic-co-glycolic acid)(PLGA) microspheres is described. Separation was performed on a C4 column via a mobile phase consisting of ACN:KH2PO4(0.02 mol/L, pH=2.5) gradient elution from 30:70 to 45:55(volume ratio) in 30 min. Multi-diode array detection(DAD) appears to be most appropriate to evaluate the spectral purity of exenatide. The limits of detection and quantification of exenatide were 0.4 and 1.2 μg/mL, respectively. The calibration curve of exenatide was linear in a range of 0.025―0.2 mg/mL with a correlation coefficient of 0.9995. The results of validation study show that this method is specific, accurate(recovery95%), precise(RSD2.0%) and robust.     

Poly(ethyleneiminoacetic acid)

A high molecular weight chelating polymer has been prepared by the reaction of poly(ethyleneimine) of molecular weight 50–100 × 10³ with a basic solution of sodium chloroacetate. The polymer which results from this reaction is hydrophilic and possesses rather generalized coordinating abilities. It forms complexes with Hg²⁺, Ca²⁺, Al³⁺, Fe²⁺, Zn²⁺, Pb²⁺, La³⁺, Nd³⁺ and Cd²⁺. Some of the metal complexes show a much lower solubility than the parent chelating polymer. Both the poly(ethyleneiminoacetic acid) and its calcium complex possess thermal and chemical stabilities comparable to that found for EDTA and its calcium complex.     

Poly(terephthalic acid anhydride) as a latent monomer in polybenzoxazole synthesis

High molecular weight poly(p-phenylenebenzobisoxazole) (PBO) was prepared from poly(terephthalic acid anhydride) (PTAA) and 1,3-diamino-4,6-dihydroxybenzene dihydrogenchloride in polyphosphoric acid (PPA). PTAA may react directly with the o-aminophenol groups to form benzoxazoles or react with PPA to generate terephthalic acid (TA) of very small particle size, which dissolves readily in PPA. PTAA provides the advantages of bypassing the requirement of small particle size TA, reducing the amount of water liberated by half, and possibly providing faster kinetics in PBO synthesis. © 1994 John Wiley & Sons, Inc.     

Poly(trimethylene carbonate)/Poly(malic acid) Amphiphilic Diblock Copolymers as Biocompatible Nanoparticles

Amphiphilic polycarbonate–poly(hydroxyalkanoate) diblock copolymers, namely, poly(trimethylene carbonate) (PTMC)‐b‐poly(β‐malic acid) (PMLA), are reported for the first time. The synthetic strategy relies on commercially available catalysts and initiator. The controlled ring‐opening polymerization (ROP) of trimethylene carbonate (TMC) catalyzed by the organic guanidine base 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD), associated with iPrOH as an initiator, provided iPrO?PTMC?OH, which served as a macroinitiator in the controlled ROP of benzyl β‐malolactonate (MLABe) catalyzed by the neodymium triflate salt (Nd(OTf)₃). The resulting hydrophobic iPrO?PTMC‐b‐PMLABe?OH copolymers were then hydrogenolyzed into the parent iPrO?PTMC‐b‐PMLA?OH copolymers. A range of well‐defined copolymers, featuring different sizes of segments (M_n,NMR up to 9300 g mol^?1; Ð_M=1.28–1.40), were thus isolated in gram quantities, as evidenced by NMR spectroscopy, size exclusion chromatography, thermogravimetric analysis, differential scanning calorimetry, and contact angle analyses. Subsequently, PTMC‐b‐PMLA copolymers with different hydrophilic weight fractions (11–75 %) self‐assembled in phosphate‐buffered saline upon nanoprecipitation into well‐defined nano‐objects with D_h=61–176 nm, a polydispersity index <0.25, and a negative surface charge, as characterized by dynamic light scattering and zeta‐potential analyses. In addition, these nanoparticles demonstrated no significant effect on cell viability at low concentrations, and a very low cytotoxicity at high concentrations only for PTMC‐b‐PMLA copolymers exhibiting hydrophilic fractions over 47 %, thus illustrating the potential of these copolymers as promising nanoparticles.     

Study of poly(lactic-co-glycolic acid) interactions with collagen

Poly(lactic-co-glycolic acid) (PLGA) is excellent to fabricate drug delivery systems that prolong the release of recombinant human growth hormone (rhGH), with current research focusing on their possible use for bone regeneration in odontological practice.Herein, we evaluate PLGA interactions with a component of the buccal cavity, as collagen, using monolayers and differential scanning calorimetry (DSC) techniques.Our results indicate that interactions in the PLGA-collagen mixtures showed no phase separation and attraction forces were detected irrespective of the concentration ratio.     

Photo-grafting Poly(acrylic acid) onto Poly(lactic acid) Chains in Solution

Poly(lactic acid)(PLA)is one of the most important bio-plastics,and chemical modification of the already-polymerized poly(lactic acid)chains may enable optimization of its material properties and expand its application areas.In this study,we demonstrated that poly(lactic acid)can be readily dissolved in acrylic acid at room temperature,and acrylic acid can be graft-polymerized onto poly(lactic acid)chains in solution with the help of photoinitiator benzophenone under 254 nm ultraviolet(UV)irradiation.Similar photo-grafting polymerization of acrylic acid(PAA)has only been studied before in the surface modification of polymer films.The graft ratio could be controlled by various reaction parameters,including irradiation time,benzophenone content,and monomer/polymer ratios.This photo-grafting reaction resulted in high graft ratio(graft ratio PAA/PLA up to 180%)without formation of homopolymers of acrylic acid.When the PAA/PLA graft ratio was higher than 100%,the resulting PLA-g-PAA polymer was found dispersible in water.The pros and cons of the photo-grafting reaction were also discussed.     

Prediction of microclimate pH in poly(lactic-co-glycolic acid) films

An equilibrium mathematical model that accurately predicts microclimate pH (mupH) in thin biodegradable polymer films of poly(lactic-co-glycolic acid) (PLGA) is described. mupH kinetics was shown to be primarily a function of: (i) kinetics of water-soluble acid content and composition in the polymer matrix and (ii) polymer/water partition coefficient of water-soluble degradation products (P(i)). Polymers were coated on standard pH glass electrodes, and mupH was measured potentiometrically. Water-soluble acid distribution and content in PLGA films were determined by pre-derivatization HPLC. Polymer degradation products partitioned favorably in the polymer phase relative to water (P(i) range: approximately 6-100), and P(i) increased with increasing hydrophobicity of the acidic species according to a linear free energy law related to reversed phase HPLC retention time for the corresponding derivatized bromophenacyl esters. The mupH predicted by the model was in excellent agreement with experimental mupH for several PLGAs as a function of time and PLGA lactic/glycolic acid ratio. These data may be useful to slowly release pH-sensitive PLGA-encapsulated bioactive substances and provide a general framework for predicting partitioning behavior of degradation products in biodegradable polymers.     

Synthesis,Characterization and Application of Poly(lactic-co-glycolic acid) with a Mass Ratio of Lactic to Glycolic Segments of 52/48

Poly(lactic-co-glycolic acid)(PLGA) is one of the most representative degradable copolymers and promising drug carriers. In the current paper, the PLGAs with a lactic acid/ glycolic acid(LA/GA) molar ratio of 52/48 and various molecular weights were prepared by a melting method. The molecular weight, molecular weight distribution, and thermal stability were determined by ¹H NMR and thermogravimetric analysis methods. The results demonstrated that PLGAs with the fixed LA/GA molar ratio(52/48), different molecular weights, and narrow molecular weight distribution could be obtained by solely altering the reaction time. The PLGA films were prepared, and their properties including micro-structure, mechanical property, in-vitro cytotoxicity, and biodegradability were characterized. In combination with the homogeneous microstructures and mechanical properties, the drug-loading and releasing properties of PLGA_3.2 films were investigated. The results show that PLGA_3.2 film with an LA/GA molar ratio of 52/48 is a promising curcumin carrier.     

Poly(o-phenylenediamine) colloid-quenched fluorescent oligonucleotide as a probe for fluorescence-enhanced nucleic acid detection

In this Letter, we demonstrate that chemical oxidation polymerization of o-phenylenediamine (OPD) by potassium bichromate at room temperature results in the formation of submicrometer-scale poly(o-phenylenediamine) (POPD) colloids. Such colloids can absorb and quench dye-labeled single-stranded DNA (ssDNA) very effectively. In the presence of a target, a hybridization event occurs, which produces a double-stranded DNA (dsDNA) that detaches from the POPD surface, leading to recovery of dye fluorescence. With the use of an oligonucleotide (OND) sequence associated with human immunodeficiency virus (HIV) as a model system, we demonstrate the proof of concept that POPD colloid-quenched fluorescent OND can be used as a probe for fluorescence-enhanced nucleic acid detection with selectivity down to single-base mismatch.     

Poly(2,3-diaminonaphthalene) microspheres as a novel quencher for fluorescence-enhanced nucleic acid detection

In this Communication, we report on the first preparation of conjugation polymer poly(2,3-diaminonaphthalene) (PDAN) microspheres via chemical oxidation polymerization of 2,3-diaminonaphthalene (DAN) monomers by ammonium persulfate (APS) at room temperature. We further demonstrate the use of PDAN microspheres as a novel quencher for fluorescence-enhanced nucleic acid detection.     

以季戊四醇为核的星形聚(D,L-乳酸)的合成与表征

以廉价易得的D,L-乳酸和季戊四醇为原料,采用直接熔融聚合法合成了以季戊四醇为核的星形聚(D,L-乳酸)(3,Mw 5 200～20 100),Tg均低于线形聚(D,L-乳酸).3的结构经1H NMR,FT-IR,GPC和XRD表征.     

溶剂诱导的聚乳酸/聚乳酸衍生物共结晶行为

通过溶液浇铸法制备不同组分的左旋聚乳酸(PLLA)和聚(L-2-羟基-3-甲基丁酸)(PL-2H3MB)共混物.运用差示扫描量热仪(DSC)、偏光显微镜(POM)、广角X射线衍射(WAXD)和热重分析仪(TGA)分析共混物的结晶、熔融行为和热稳定性.通过观察到DSC加热曲线中新的熔融峰判断PLLA和PL-2H3MB共晶...     

Use of sterically-stabilised polystyrene latex particles as a pH-responsive particulate emulsifier to prepare surfactant-free oil-in-water emulsions

A pH-responsive, sterically-stabilised polystyrene latex is used as a particulate emulsifier for oil-in-water emulsions; demulsification occurs rapidly on lowering the solution pH and the original emulsion can be reformed on pH cycling.     

聚乳酸组织工程支架材料

综述了生物活性因子固定化的聚乳酸-聚氨基酸衍生物共聚物和通过亲-疏水性设计的众多聚乳酸-聚氧化乙烯（PLA-PEO）共聚物的研究进展。展现了其在组织工程材料,药物控释体系和其他生物医用材料中的广泛应用前景。