Polyethyleneimine/poly-(γ-glutamic acid)/poly(lactide-co-glycolide) nanoparticles for loading and releasing antiretroviral drug

Nanoparticles (NPs) with ternary components of polyethyleneimine (PEI), poly-(γ-glutamic acid) (γ-PGA), and poly(lactide-co-glycolide) (PLGA) were applied to carry and release saquinavir (SQV). Hydrophobic SQV was encapsulated in the particle core composed of PLGA to form SQV-PLGA NPs, and the surface of SQV-PLGA NPs was grafted successively with hydrophilic γ-PGA and PEI (PEI/γ-PGA/SQV-PLGA NPs). The morphological images revealed that PEI/γ-PGA/SQV-PLGA NPs were spheroid-like, in general. An increase in the concentration of didecyl dimethylammonium bromide and a reduction in the dose of SQV enhanced the entrapment efficiency of SQV in PLGA NPs. In addition, an increment in the molecular weight of γ-PGA reduced the grafting efficiency of PEI on γ-PGA/SQV-PLGA NPs. An increase in the weight percentage of PEI enhanced the average particle diameter. However, the grafting efficiency of PEI on γ-PGA/SQV-PLGA NPs and the dissolution rate of SQV from PEI/γ-PGA/SQV-PLGA NPs reduced when the weight percentage of PEI increased. PEI/γ-PGA/SQV-PLGA NPs are an innovative drug delivery system and can be used for antiretroviral trials.     

Surface coverage of didecyl dimethylammonium bromide on poly(lactide-co-glycolide) nanoparticles

Coverage of didecyl dimethylammonium bromide (DDAB) on the surface of poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) was investigated. DDAB-stabilized PLGA NPs (DDAB/PLGA NPs) were prepared by emulsification-diffusion technique with high shear stress. The fabricated DDAB/PLGA NPs were ellipsoidal and positively charged. An increase in the homogenizing stirring rate and in the weight percentage of DDAB in microemulsion reduced the particle size of DDAB/PLGA NPs. When the homogenizing stirring rate increased or the DDAB level in microemulsion decreased, the zeta potential of DDAB/PLGA NPs reduced. In addition, a high homogenizing stirring rate reduced the surface coverage of DDAB on PLGA NPs. The surface coverage of DDAB on PLGA NPs enhanced with increasing the weight percentage of DDAB in microemulsion. The quantity of DDAB attached on the surface could appreciably affect the properties of DDAB/PLGA NPs.     

Loading efficiency and surface conductance of heparin-modified poly(lactide-co-glycolide) nanoparticles

Poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) with surface modification of heparin were fabricated by microemulsion–diffusion method. These novel colloidal particles were stabilized by lecithin and Tween 80. The effects of lecithin on the loading of heparin onto PLGA NPs and on the surface conductance were analyzed. The electronic micrographs revealed that spherical colloids were prepared and the incorporation of heparin caused a slight coalescence of the particles. In addition, the average diameter of heparin-modified PLGA NPs was between 70 and 220 nm. An increase in the weight percentage of lecithin or in the concentration of heparin enlarged the average diameter. Based on constant amount of surfactants, the loading efficiency of heparin on the particle surfaces reached a maximum when the weight percentage of lecithin was 50%. Moreover, the surface conductance of heparin-modified PLGA NPs was improved by an increased weight percentage of lecithin. A high concentration of heparin in microemulsion also promoted the loading efficiency and surface conductance of heparin-modified PLGA NPs.     

Impact of arginine-modified solid lipid nanoparticles on the membrane charge of human brain-microvascular endothelial cells

Electrokinetic and electrostatic properties of human brain-microvascular endothelial cells (HBMECs) with the uptake of l-arginine (Arg)-modified solid lipid nanoparticles (RSLNs) were investigated. The exposure of these HBMECs to radiofrequency electromagnetic field (EMF) was also considered. As compared with the original culture of HBMECs, the uptake of the biomimetic RSLNs induced smaller absolute values of electrophoretic mobility, zeta potential, Donnan potential, and fixed charge density. In addition, an increase in the coverage fraction of Arg on the external layers of the RSLNs reduced the electrical characteristics of HBMECs. An increase in the power of EMF also decreased the charge of RSLNs-incorporating HBMECs. On the contrary, softness of HBMECs was enhanced by an increased coverage fraction of Arg and an increased power of EMF. Electrophysiology of HBMECs can be efficiently mediated by the novel RSLNs and exposure to EMF through fluctuation and redistribution of the membrane charge.     

Bioinspired dual dynamic network hydrogels promote cartilage regeneration through regulating BMSC chondrogenic differentiation

How to improve the therapeutic efficacy of cell delivery during mechanical injection has been a great challenge for tissue engineering. Here, we present a facile strategy based on dynamic chemistry to prepare injectable hydrogels for efficient stem cell delivery using hyaluronic acid (HA) and poly(γ-glutamic acid) (γ-PGA). The combination of the guest–host (GH) complexation and dynamic hydrazone bonds enable the HA/γ-PGA hydrogels with physical and chemical dual dynamic network and endow hydrogels a stable structure, rapid self-healing ability, and injectability. The mechanical properties, self-healing ability, and adaptability can be programmed by changing the ratio of GH network to hydrazine bond cross-linked network. Benefitting from the dynamic cross-linking networks, mild preparation process, and cytocompatibility of HA/γ-PGA hydrogels, bone marrow mesenchymal stem cells (BMSCs) show high cell viability in this system following mechanical injection. Moreover, HA/γ-PGA hydrogels can promote BMSC proliferation and upregulate the expression of cartilage-critical genes. Notably, in a rabbit auricular cartilage defect model, BMSC-laden HA/γ-PGA hydrogels can effectively promote cartilage regeneration. Together, we propose a general strategy to develop injectable self-healing HA/γ-PGA hydrogels for effective stem cell delivery in cartilage tissue engineering.     

Surface modification of poly(lactide-co-glycolide) nanoparticles by d-α-tocopheryl polyethylene glycol 1000 succinate as potential carrier for the delivery of drugs to the brain

The potential health benefits of vitamin E (d-α-tocopheryl polyethylene glycol 1000 succinate, TPGS), particularly, in curing of the neurological symptoms associated with vitamin E deficiency have been reported. Hence, vitamin E containing carriers for delivery of drugs to the brain might be useful from different points of view. Herein, in order to obtain desired surface morphology and particle size of poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) and high emulsifying effects, TPGS-modified PLGA NPs were optimized as a potential carrier for the delivery of drugs to the brain. The particle sizes, surface morphology, phase composition correlated with different emulsifiers and different stirring times were characterized. Also, the in vitro cytotoxicity of the samples using PC12 cell line was investigated. According to the obtained results, by increasing the percentages of TPGS, the average particle size decreased and the distribution of particle diameters came closer by further addition, and the larger particles did not create. In addition, no obvious cytotoxicity was observed at various TPGS amounts, and the modified PLGA NPs were considered biocompatible since they show little decrease in cellular viability. With the increase of TPGS ratio, more effective in vitro therapeutic effects could be observed, which achieved the highest cell viability, because the degradation of NPs may release the most amounts of TPGS components that have synergistic activity. Furthermore, it was found that TPGS as a water-soluble derivative of natural source of vitamin E could be a perfect emulsifier for making PLGA NPs as potential carrier for delivery of drugs to the brain.     

Physicochemical and anti-bacterial performance characterization of clarithromycin nanoparticles as colloidal drug delivery system

The objective of the present study was to prepare clarithromycin (CLR) loaded biodegradable nanoparticles (NPS), with a view to investigate its physicochemical properties and anti-bacterial activity. PLGA was used as a biodegradable polymer and the particles were prepared by nano-precipitation method in 3 different drugs to polymer ratios. Evaluation of the physicochemical properties of the prepared nanoparticles was performed using encapsulation efficiency, nanoparticle production yield, dissolution studies, particle size analysis, zeta potential determination, differential scanning calorimetry, Fourier-transform infrared spectroscopy and X-ray powder diffractometry. The antimicrobial activity against Staphylococcus aureus was determined using serial dilution technique to achieve the minimum inhibitory concentration (MIC) of NPs. The particles were between 189 and 280 nm in size with narrow size distribution, spherical shape and 57.4-80.2% entrapment efficiency. Zeta potential of the NPs was fairly negative. The DSC thermograms and X-ray diffraction patterns revealed reduced drug crystallinity in the NPs. FT-IR spectroscopy demonstrated possible noncovalent interactions between the drug and polymer. In vitro release study showed an initial burst followed by a plateau during a period of 24 h. The NPs were more effective than intact CLR against S. aureus so that the former showed equal antibacterial effect at 1/8 concentration of the intact drug. In conclusion, the prepared CLR nanoparticles are more potent against S. aureus with improved MICs and appropriate physicochemical properties that may be useful for other susceptible microorganisms and could be an appropriate candidate for intravenous, ocular and oral and topical preparations.     

Capillary electrophoresis of bone marrow stromal cells with uptake of heparin‐functionalized poly(lactide‐co‐glycolide) nanoparticles during differentiation towards neurons

This study analyzes the varying electrophoretic mobility and zeta potential of bone marrow stromal cells (BMSCs) during their differentiation towards neurons. Electrophoresis of primary BMSCs and neuron growth factor (NGF)‐induced neuron‐like cells with the uptake of heparin‐functionalized poly(lactide‐co‐glycolide) (PLGA) nanoparticles (NPs) are also investigated. Immunofluorescent images revealed that a high concentration of NGF accelerated the differentiation of BMSCs into neurons. When the concentration of NGF increased, the absolute values of electrophoretic mobility and zeta potential of the differentiating BMSCs increased. In addition, a longer inductive period yielded higher charge of the differentiating BMSCs and a smaller uptake amount of heparin‐functionalized PLGA NPs. However, an increase in the loading efficiency of heparin on PLGA NPs enhanced the uptake and reduced the electrical characteristics of the primary and differentiating BMSCs. Hence, a general rule is drawn that an increase in the uptake of heparin‐functionalized PLGA NPs decreased the electrophoretic mobility and zeta potential of BMSCs during differentiation towards neurons.     

Layer-by-layer films of enzymatically synthesized poly(aniline)/bacterial poly(γ-glutamic acid) for the construction of nanocapacitors

Poly(aniline) (PANi) and poly(γ-glutamic acid) (γ-PGA) have been synthesized by enzymatic catalysis and natural bacterial reactions, respectively. Layer-by-layer films have been prepared on glass or quartz slides by alternative immersions of the substrate in dilute solutions of γ-PGA and PANi, with several rinsing in between each deposition. UV-vis spectroscopy has been used to follow the evolution of the self-assembly process as well as to characterize the oxidative states of PANi. The linear dependence of the absorbance vs. the number of layers indicates a constant increase of thickness layer-by-layer. The morphology of the multilayer films, analyzed by atomic force microscopy, is granular type. Enzymatically synthesized PANi nanofilms present good electrical conductivity while γ-PGA acts as an insulating material. These differences in electrical properties and the possibility to obtain alternated multilayered films permit the construction of entirely “biological” nanocapacitors.     

Effect of PLGA as a polymeric emulsifier on preparation of hydrophilic protein-loaded solid lipid nanoparticles

Most proteins are hydrophilic and poorly encapsulated into the hydrophobic matrix of solid lipid nanoparticles (SLN). To solve this problem, poly (lactic-co-glycolic acid) (PLGA) was utilized as a lipophilic polymeric emulsifier to prepare hydrophilic protein-loaded SLN by w/o/w double emulsion and solvent evaporation techniques. Hydrogenated castor oil (HCO) was used as a lipid matrix and bovine serum albumin (BSA), lysozyme and insulin were used as model proteins to investigate the effect of PLGA on the formulation of the SLN. The results showed that PLGA was essential for the primary w/o emulsification. In addition, the stability of the w/o emulsion, the encapsulation efficiency and loading capacity of the nanoparticles were enhanced with the increase of PLGA concentration. Furthermore, increasing PLGA concentration decreased zeta potential significantly but had no influence on particle size of the SLN. In vitro release study showed that PLGA significantly affected the initial burst release, i.e. the higher the content of PLGA, the lower the burst release. The released proteins maintained their integrity and bioactivity as confirmed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and biological assay. These results demonstrated that PLGA was an effective emulsifier for the preparation of hydrophilic protein-loaded SLN.     

PLGA/O-CMC载药纳米粒子的体外释药行为研究

本文以聚乳酸-乙醇酸共聚物(PLGA)和自行制备的O-羧甲基壳聚糖(O-CMC)为原料,以5-氟尿嘧啶(5-FU)为抗癌药物模型,采用自身设计的改良复乳法制备了载药纳米微粒。微粒平均粒径为98.5nm,粒径分布指数为0.192,粒子表面∈电位为61．48eV,载药率高达18．9％,包封率为86％。然后用SEM动态监测载药纳米粒子降解过程中表面形貌的变化,并连续追踪粒子降解过程中的质量损失和降解介质的pH变化。载药纳米粒子在PBS中的释药行为研究表明：(1)前12h的释药动力学符合Huguchi方程,具有一级释放特性;(2)在20天内的释药动力学符合零级释放特性。     

Internalization of PLGA nanoparticles coated with poloxamer 188 in glioma cells: A confocal laser scanning microscopy study

Internalization of poloxamer 188-coated PLGA nanoparticles (NPs) in GL261 murine glioma cells was studied using confocal laser scanning microscopy. For visualization, both poloxamer 188 (P188) and PLGA were labeled covalently with fluorescent dyes Rhodamine B and Cyanine5, respectively. The results indicated that the PLGA NPs coated with poloxamer 188 enter a cell as an integral core–shell structure, which can be helpful for gaining further insight into the in vivo performance of surfactant-coated polymeric NPs as core–shell delivery systems     

Stabilizer‐Free Poly(lactide‐co‐glycolide) Nanoparticles Conjugated with Quantum Dots as a Potential Carrier Applied in Human Mesenchymal Stem Cells

We report that human mesenchymal stem cells (hMSCs) were successfully labeled with poly(lactide‐co‐glycolide) nanoparticles (PLGA NPs) surface‐conjugated quantum dots (QDs) (PLGA‐QD NPs) via endocytosis pathway. These NPs were not toxicity even treated with PLGA‐QD NPs at high concentrations for at least four weeks. Besides, PLGA‐QD NPs‐labeled hMSCs did not change their proliferation and differentiation capability toward the cell fates of adipocytes, osteocytes, and chrondrocytes. It's known that PLGA has been widely employed to act as delivery carrier which encapsulates drugs and releases them under a controlled way. Currently, we have also demonstrated that FITC‐loaded PLGA‐QD NPs degraded in hMSCs to achieve intracellular release of FITC. The aim of this research is to investigate viability, proliferation and differentiation capability and the potential for gene delivery of MSCs labeled with PLGA‐QD NPs. In addition to PLGA‐QD NPs, QDs alone were used to serve as a control set for comparison.     

Poly(ether imide) membranes modified with poly(ethylene imine) as potential carriers for epidermal substitutes

Poly(ether imide) (PEI) membranes were modified with a linear low-molecular weight (PETIM_0.6) and a branched high-molecular weight poly(ethylene imine) (PETIM_60). The membrane surfaces became more hydrophilic and the zeta potentials were shifted from negative to positive zeta values after immobilisation of both PETIM. These measurements also indicated the presence of a swollen surface layer in the case of PETIM_60, while a regular structuring of the surface was observed with scanning force microscopy for PETIM_0.6. A human keratinocyte cell line HaCaT was cultured on the different membranes. It was found that HaCaT cell growth was stimulated by PETIM_0.6. Cells reached earlier confluence on this substratum, while their growth was inhibited on a PEI membrane modified with PETIM_60, which makes PEI membranes modified with PETIM_0.6 a promising material for in vitro culture of epidermal transplants.     

A Serum‐Resistant Low‐Generation Polyamidoamine with PEI 423 Outer Layer for Gene Delivery Vector

A new derivative of polyamidoamine and polyethylenimine, G2.5‐PEI 423 or G1.5‐PEI 423, is prepared by an amidation reaction of PAMAM G2.5 or PAMAM G1.5 using PEI 423. The polycations show a great ability to combine with pDNA to form complexes, which protect the pDNA from nuclease degradation. The polymers display stronger buffer capacity and lower cytotoxicity. The complexes have particle sizes of 120–180 nm and zeta potentials of 20–40 mV. The G2.5‐PEI 423 complexes display much higher transfection efficiencies than PAMAM G5 and Lipo‐2k, and the G1.5‐PEI 423 complexes display higher transfection efficiencies than PAMAM G4 and PEI‐25k. The complexes possess better serum‐resistant capacity. The G2.5‐PEI 423 has a great potential to be used as a serum‐resistant gene vector.

     

Degradation behavior of electrospun microfibers of blends of poly(lactide-co-glycolide) and Pluronic F-108

Electrospun poly(dl-lactide-co-glycolide) (PLGA) microfibers have been explored as extra cellular matrix mimicking scaffolding systems for tissue engineering application. However, the hydrophobic nature of PLGA can be limiting in terms of protein adsorption. Hence, blending of PLGA with a hydrophilic polymer (Pluronic^®) prior to electrospinning has been explored as a potential strategy to impart hydrophilicity to PLGA microfibers. In this study, PLGA (85/15) was blended with small quantities (0.5-2% w/v) of Pluronic^® F-108 (PF-108) and electrospun into microfibers. Blending of PF-108 demonstrated a significant decrease in the surface hydrophilicity of microfibers as was evidenced by an increase in wetting tension. Surface analysis using XPS indicated the presence of PF-108 in the bulk of the fibers in addition to the surface of the fibers. The results of the water uptake studies indicated that the water uptake capacity and consequential fiber swelling was significantly increased in the presences of PF-108. The in vitro degradation studies demonstrated that the trend in molecular weight loss was not significantly influenced by the presence of small quantities of PF-108. Therefore, blending of PLGA with PF-108 could be an effective technique for surface modification of electrospun PLGA microfibers without compromising on the other advantages of PLGA.     

Folate receptor-mediated gene delivery using folate-poly(ethylene glycol)-poly(L-lysine) conjugate

For efficient receptor-mediated gene transfection, a new and simple formulation method based on using PEI and FOLPEGPLL conjugate was presented. Luciferase plasmid DNA and PEI were complexed to form slightly positive-charged nanoparticles, onto which FOL-PEG-PLL conjugate was surface coated. With increasing the coating amount of FOL-PEG-PLL conjugate, the FOL-PEG-PLL/PEI/DNA complexes exhibited increased surface zeta-potential values with concomitantly increased diameters, indicating that the PLL part was physically anchored on the surface of preformed PEI/DNA complexes with FOL moieties being exposed on the outside. The formulated complexes exhibited a considerably higher transfection efficiency against FOL receptor over-expressing KB cells than FOL receptor deficient A549 cells. This was caused by an enhanced cellular uptake of the resultant complexes via a receptor-mediated endocytosis process. The formulated complexes showed a higher gene expression level, even in the presence of serum, than the PEI/DNA or Lipofectamine/DNA complexes. This was attributed to the PEG chains present on the surface of complexes that could work as a protective shield layer against aggregation caused by non-specific protein adsorption. The FOL-PEG-PLL/PEI/DNA complexes also demonstrated better cell viability than the PEI/DNA complexes.(1)H NMR spectrum of FOL-PEG-PLL conjugate.     

聚谷氨酸苄酯脱保护制备聚L-谷氨酸的正交实验研究

聚L-谷氨酸苄酯(PBLG)用体积分数为33%的HBr-醋酸溶液脱保护得到聚L-谷氨酸(PLGA). 采用正交实验研究了温度、时间、溶剂及33%HBr-醋酸溶液用量在脱保护过程中对聚L-谷氨酸分子量的影响. 结果表明, 反应温度越高, 时间越长, 溶剂二氯乙酸用量越大, PBLG降解越快, 得到的PLGA分子量越小; 33%HBr-醋酸溶液的影响则相反, 随着33%HBr-醋酸溶液用量的增加, 反应体系酸性减弱, PBLG溶解度降低, 肽键断裂减缓, PLGA分子量也就相对较大.     

pH Responsive Poly(Amino Acid) Nanoparticles as Potent Carrier Adjuvants for Enhancing Cellular Immunity

Adjuvants are widely used in vaccine to improve the protection or treatment efficacy. However, so far they inevitably produce side effects and are hard to induce cellular immunity in practical application. Herein, two kinds of amphiphilic poly(glutamic acid) nanoparticles (α-PGA-F and γ-PGA-F NPs) as nanocarrier adjuvants are fabricated to induce an effective cellular immune response. Amphiphilic PGA are synthesized by grafting phenylalanine ethyl ester to form biodegradable self-assembly nanoadjuvants in a water solution. The model antigen, chicken ovalbumin (OVA), can be loaded into PGA-F NPs (OVA@PGA-F NPs) with the high loading ratio >12%. Moreover, compared with γ-PGA-F NPs, the acidic environment can induce the α-helical secondary structure of α-PGA NPs, promoting membrane fusion and more fast antigen lysosomal escape. Hence, the antigen presenting cells treated with OVA@α-PGA-F NPs show higher secretion of inflammatory cytokines, and higher expression of major biological histocompatibility complex class I and CD80 than those of OVA@γ-PGA-F NPs. Overall, this work indicates that pH responsive α-PGA-F NPs as a carrier adjuvant can effectively improve the ability of cellular immune responses, leading to it being a potent candidate for vaccine applications.     

同载基因和药物的超微载体粒子的制备及体外评价

以聚乳酸_乙醇酸共聚物 (PLGA)和自行制备的O_羧甲基壳聚糖 (O_CMC)为原料 ,以 5_氟尿嘧啶 (5 Fu)为抗癌药物模型 ,以反义EGFR(表皮生长因子受体 )为基因药物模型 ,构建与评价了同载抗癌药物与基因的复合功能纳米药物载体系统。同载超微粒子的平均粒径为 2 5 8 7nm ,粒径分布指数为 0 14 2 ,粒子表面 ξ电位为 - 10 6 7eV。同载超微粒子在PBS中的释药行为研究表明 :超微粒子中 5_FU和基因均具有零级缓慢释放特性。体外肿瘤细胞存活率实验和免疫组化实验均证实同载超微粒子能高效抑制TJ90 5人脑胶质瘤细胞的增殖。最后用荧光共聚焦显微镜动态监测了超微粒子进入瘤细胞的转染过程 ,发现粒子可在不同时间内进入细胞浆和细胞核。