Novel Polysaccharide-Decorated Poly(Isobutyl Cyanoacrylate) Nanoparticles

PURPOSE: The aim of this work was to synthesize new surface-modified nanoparticles using a radical emulsion polymerization of an alkyl cyanoacrylate. METHODS: Isobutyl cyanoacrylate was polymerized in nitric acid 0.2 M containing a polysaccharide (0.1375 g) and cerium (8 x 10(-2) M). After 1 h, the pH was adjusted to 7.0, and the nanoparticles were purified by dialysis. Nanoparticle characterization included scanning electron microscopy, quasi-elastic light scattering, zeta potential determination, measurements of the complement activation induced by different polysaccharide-coated nanoparticles and of the antithrombic activity of heparin. RESULTS: Dispersions of spherical particles were obtained using various polysaccharides. The particle diameter varied from 90 nm to several micrometers, and the zeta potential depended on the molecular weight and the nature and charge of the polysaccharide. Surface analysis performed by ESCA confirmed the presence of polysaccharides at the nanoparticle surface. The nanoparticles were very stable, and the biologic activity of the polysaccharide was preserved. Complement activation was influenced by the polysaccharide characteristics. CONCLUSIONS: A new method based on radical emulsion polymerization of isobutyl cyanoacrylate initiated by polysaccharides and cerium was developed to prepare nanoparticles. It leads, in a single step, to nanoparticles with surface properties defined by the polysaccharide. This method is a new concept for the development of biomimetic drug carriers with multiple functions.     

Polymeric Micelles Based on Amphiphilic Scorpion-like Macromolecules: Novel Carriers for Water-Insoluble Drugs

No HeadingPurpose. The objective was to evaluate amphiphilic scorpion-like macromolecules (AScMs) as drug carriers for hydrophobic drugs.Methods. Indomethacin (IMC) was incorporated into two AScM micelles (M₁₂P₅ and M₁₂P₂) by the O/W emulsion technique. The influences of IMC:polymer feed ratio and molecular weight of the hydrophilic block of AScMs on the micelle size, IMC entrapment efficiency and release behavior were investigated. Furthermore, cytotoxicity of the AScMs was evaluated with human umbilical vein endothelial cells (HUVEC).Results. The maximal IMC entrapment efficiency in M₁₂P₅ and M₁₂P₂ micelles (72.3 and 20.2%, respectively) was obtained at ratios of 0.1 to 1 for indomethacin:polymer. The sizes of IMC-loaded M₁₂P₅ and M₁₂P₂ polymeric micelles were <20 nm with a narrow size distribution. In vitro release studies revealed that IMC released from M₁₂P₅ and M₁₂P₂ polymeric micelles showed sustained release behavior during the 24 h of experiment. Additionally, M₁₂P₅ and M₁₂P₂ polymeric micelles did not induce remarkable cytotoxicity against HUVEC cells at concentrations up to 1 and 0.5 mM, respectively.Conclusions. The amphiphilic scorpion-like macromolecules may be useful as novel drug carriers because of their small size, ability to encapsulate hydrophobic drugs and release them in a sustained manner as well as low cytotoxicity.     

Stability and Release Performance of a Series of Pegylated Copolymeric Micelles

Purpose. The aim of this work is to evaluate the capability of a series of biocompatible amphiphilic copolymers as a nano-sized drug carrier. Methods. The influences of the type of lactone monomer, the feed molar ratios of lactone/PEG, and the molecular weight of PEG on the performance and release behavior of micelles are investigated. Results. These pegylated amphiphilic copolymers efficiently form micelles with a low CMC value in the range of 10^–6-10^–7 M. The average particle size of micelles is 100 nm. The phenomenon of increasing particle size as increasing the chain length of poly(lactone) block is observed. The different hydrophobicity, based on chemical structure of poly(lactone), accounts for different interaction strength between indomethacin and hydrophobic inner core, which further influences the drug loading in copolymeric micelles and their release character. In addition, the PCL/PEG/PCL micellar solutions maintain their sizes at 4°C for 8 weeks without occurring significant aggregation or dissociation. Conclusions. A series of biocompatible pegylated amphiphilic copolymers have been elucidated possessing micellization potential to form nano-sized micelles in an aqueous environment, which enable incorporate hydrophobic drug and regulate drug release.     

Near Infrared with Principal Component Analysis as a Novel Analytical Approach for Nanoparticle Technology

Purpose. To progress in the characterization of a poly(MePEGcyanoacrylate-co-hexadecylcyanoacrylate) (poly(PEGCA-co-HDCA) copolymer and the nanoparticles formed from this copolymer. Methods. Poly(PEGCA-co-HDCA) at a MePEG/hexadecyl ratio of 1:4 was investigated by ¹H-NMR and near infrared spectroscopy. The nanoparticle suspensions, obtained by the methods of nanoprecipitation or emulsion—solvent evaporation, as well as the crude nanoparticles and their dispersion medium—were analyzed by MePEG measurement, ¹H-NMR, and near infrared spectroscopy. Results. The ¹H-NMR results showed that the (poly(PEGCA-co-HDCA) copolymer obtained bore lateral hydrophilic MePEG chains and lateral hydrophobic hexadecyl chains in a final ratio of 1:4. However, this ratio, although reproducible from batch to batch, represented only a mean value for different molecular species. Indeed, our results demonstrated the formation of more hydrophobic poly(alkylcyanoacrylate) oligomers (with a higher content of hexadecyl chains) and other more hydrophilic oligomers (with a higher MePEG content). Only the more hydrophobic oligomers were able to form solid pegylated nanoparticles. As far as these nanoparticles were concerned, determination of their MePEG content allowed the calculation of a distance of 1.2 nm and 1.05 nm between 2 grafted MePEG chains at the nanoparticle surface, when obtained by nanoprecipitation and emulsion-solvent evaporation, respectively. Moreover, when the same copolymer batch was used, different nanoparticles were obtained according to the preparation method, as seen by near infrared spectroscopy. Conclusions. The nanoparticles obtained by nanoprecipitation or emulsion-solvent evaporation of poly(PEGCA-co-HDCA) 1:4 copolymer displayed a different supramolecular organization, as evidenced by the near infrared spectroscopy results. Moreover, these nanoparticles showed surface characteristics compatible with a long circulating carrier.     

Novel Polyester-Polysaccharide Nanoparticles

Purpose. The aim of the present study was to develop a new type of core-shell nanoparticles from a family of novel amphiphilic copolymers, based on dextran (DEX) grafted with poly(–caprolactone) (PCL) side chains (PCL-DEX). Methods. A family of PCL-DEX copolymers was synthesized in which both the molecular weight and the proportion by weight of DEX in the copolymer were varied. The nanoparticles were prepared by a technique derived from emulsion-solvent evaporation, during which emulsion stability was investigated using a Turbiscan. The nanoparticle size distribution, density, zeta potential, morphology, and suitability for freeze-drying were determined. Results. Because of their strongly amphiphilic properties, the PCL-DEX copolymers were able to stabilize o/w emulsions without the need of additional surfactants. Nanoparticles with a controlled mean diameter ranging from 100 to 250 nm were successfully prepared. A mechanism of formation of these nanoparticles was proposed. Zeta potential measurements confirmed the presence of a DEX coating. Conclusion. A new generation of polysaccharide-decorated nanoparticles has been successfully prepared from a family of PCL-DEX amphiphilic copolymers. They may have potential applications in drug encapsulation and targeting.     

聚乙二醇化聚氰酯毫微粒作为salvicine载体：合成、制备和体外特性

目的：合成和鉴定聚乙二醇化聚氰酯共聚物,制备聚乙二醇化聚氰酯共聚物和聚氰酯聚合物的毫微粒,测定二种毫微粒的体外特性。方法：用^1H-NMR,^13C-NMR和FTIR测定聚乙二醇化聚氰酯共聚物的结构,用凝胶渗透色谱法测定共聚物的分子量,用乳化／蒸发法制备毫微粒。结果：^1H-NMR,^13C-NMR和FTIR光谱与聚乙二醇化聚氰酯共聚物的结构相符,合成共聚物的分子量是6680,用HPLC测定毫微粒的包封效率时,共聚物对salvicine的测定无干扰,聚乙二醇化聚氰酯共聚物毫微粒的包封率是92．6％,聚氰酯聚合物的包封效率是98．9％。二种毫微粒的粒径均为250nm左右。Zeta电位值受聚合物结构的影响,与聚氰酯毫微粒比较（－23．1mV),聚乙二醇化聚氰酯毫微粒显示低的Zeta电位值（－9.6mV)。毫微粒的体外释放显示一个开始的突释效应,然后缓慢释放达28天。结论：聚乙二醇化聚氰酯毫微粒可能是salvicine体内抗肿瘤作用的一个有效载体。     

Formation and Isolation of Spherical Fine Protein Microparticles Through Lyophilization of Protein-Poly(ethylene Glycol) Aqueous Mixture

Purpose. Preparation of spherical fine protein microparticles by the lyophilization of a protein-poly(ethylene glycol) (PEG) aqueous mixture was investigated. The main objective was to establish a method for preparing protein microparticles suitable for pharmaceutical production. Methods. Aqueous solutions containing bovine serum albumin (BSA) and PEG at various mixing ratios were freeze-dried. The lyophilizates were dispersed in methylene chloride and subjected to particle size analysis. Analogous studies were performed using several model proteins. A phase diagram of the PEG-BSA aqueous system was obtained by the titration method. Results. The particle size of BSA decreased as the PEG-BSA ratio increased. A bending point was observed in this relationship, at which the PEG-BSA ratio coincided with that of the critical point on the phase diagram of the PEG-BSA system. These results were explained by the freezing-induced condensation, followed by phase separation in the PEG-BSA system. Conclusions. Spherical fine protein microparticles were successfully obtained at high yield and without any activity loss under optimum conditions. This new technology could be applicable to proteins with a wide range of molecular weights, and is expected to be developed for dry powder inhalations or long-term sustained release microsphere formulations.     

改良透析法制备MePEG-PLGA-羟基喜树碱共聚物纳米粒

目的 以聚合物单甲氧基聚乙二醇-聚乳酸聚乙醇酸(MePEG-PLGA)为载体,羟基喜树碱(hydroxy camptothecin, HCPT)为模型药物,采用改良的透析法优化制备单甲氧基聚乙二醇-聚乳酸聚乙醇酸-羟基喜树碱共聚物纳米粒(MePEG-PLGA-HCPT-NPs),并进行表征。方法 以粒径和载药量为指标,考察各影响因素优化制备工艺。并进行外观、粒径、Zeta电位、载药量和包封率的测定。结果 优化制备条件：丙酮作为溶剂,透析温度为25 ℃,透析初始含水量为1%,透析外水相pH=4.0,聚合物浓度为3 mg·mL^-1,载体中的PEG含量为15%,载体中的乳酸含量为100%,HCPT与MePEG-PLGA投料质量比为1∶5。优化制备的MePEG-PLGA-HCPT-NPs为实心球形壳核结构,表面圆滑,粒径分布均一,分散性好,平均粒径(120.1±2.4)nm,多分散系数为0.057±0.021,Zeta电位为(-31.2±0.98)mV,载药量为7.42%,包封率为44.5%。结论 改良透析法适合MePEG-PLGA-HCPT-NPs的制备,为后续研究奠定了良好的基础。     

Pegylated nanoparticles based on poly(methyl vinyl ether-co-maleic anhydride): preparation and evaluation of their bioadhesive properties

Pegylated nanoparticles based on poly(methyl vinyl ether-co-maleic anhydride) (PVM/MA) were prepared by simple solvent displacement method, in the absence of catalysts or specific chemical conditions. Pegylation efficiency increased with the increasing of molecular weight and bulk concentration of poly(ethylene glycols) (PEGs) investigated. In fact, the use of PEG with molecular weight less than 1000 Da did not lead to its attachment. ¹H NMR spectroscopy was performed in order to estimate the conformation state of PEG-chains and to predict the nanoparticle structure. Pegylation with PEG 2000 gave surface modified nanoparticles (“brush” conformation), while the chains of PEG 1000 were distributed either in the core or physically adsorbed on the nanoparticle surface. The capacity of nanoparticles to adsorb mucin at pH 7.4 was significantly higher for PEG 1000-NP than for PEG 2000-NP. The “brush” layer seemed to decrease the interaction between PEG 2000-NP and mucin, which facilitated their penetration through the mucus gel. As a consequence, PEG 2000-NP displayed higher capacity to develop adhesive interactions with rat intestinal mucosa in vivo. Independent on the weaker bioadhesive potential of PEG 1000-NP, both types of pegylated nanoparticles demonstrated very high affinity to the intestinal mucosa rather than to the stomach wall, which could be established for drug targeting to the small intestine.     

Use of Block Copolymers of Poly(Ortho Esters) and Poly (Ethylene Glycol) Micellar Carriers as Potential Tumour Targeting Systems

Amphiphilic AB and ABA block copolymers have been prepared from poly (ortho esters) and poly (ethylene glycol). Such block copolymers readily form micellar dispersions in water, or buffers. The CMC is in the range of 3 × 10_-4–5 × 10_-4 g/l which is a value low enough to assure retention of micelle integrity upon intravenous injection. The size, as determined by dynamic light scattering was in the 40–70 nm range. The micelles can be stored in lyophilized form for at lest 8 months and easily reconstituted to the original properties. The micelles are stable in PBS at pH 7.4 and 37°C for 3 days and in a citrate buffer at pH 5.5 and 37°C for 2 h. Stability in the presence of bovine serum albumin depends on the structure of the block copolymer and especially the length of the POE block.     

Sheddable Coatings for Long-Circulating Nanoparticles

Nanoparticles, such as liposomes, polymeric micelles, lipoplexes and polyplexes are frequently studied as targeted drug carrier systems. The ability of these particles to circulate in the bloodstream for a prolonged period of time is often a prerequisite for successful targeted delivery. To achieve this, hydrophilic ‘stealth’ polymers, such as poly(ethylene glycol) (PEG), are used as coating materials. Such polymers shield the particle surface and thereby reduce opsonization by blood proteins and uptake by macrophages of the mononuclear phagocyte system. Yet, after localizing in the pathological site, nanoparticles should deliver their contents in an efficient manner to achieve a sufficient therapeutic response. The polymer coating, however, may hinder drug release and target cell interaction and can therefore be an obstacle in the realization of the therapeutic response. Attempts have been made to enhance the therapeutic efficacy of sterically stabilized nanoparticles by means of shedding, i.e. a loss of the coating after arrival at the target site. Such an ‘unmasking’ process may facilitate drug release and/or target cell interaction processes. This review presents an overview of the literature regarding different shedding strategies that have been investigated for the preparation of sterically stabilized nanoparticulates. Detach mechanisms and stimuli that have been used are described.     

Preparation of Nanoparticles by Solvent Displacement Using a Novel Recirculation System

Submicron colloidal suspensions of poly(ε-caprolactone) (PCL) were prepared by the solvent displacement method, using either the conventional form or a new recirculation device. In the latter case, a process that allows the recirculation of the aqueous phase into a device, providing a continuous flow, is proposed. The influence of the organic solution injection rate and polymer concentration on mean particle size and process yield were studied for both methods. The recirculation rate was also analyzed for the recirculation system. Nanoparticles (NPs) showed mean sizes that ranged from 156 to 381. The smallest particles were obtained when recirculation rate, injection rate and polymer concentration were maximized but at the expense of the yield. The only acceptable yields (83–96%) were obtained at the lowest PCL concentration (2.5% w/v). ANOVA tests (α = 0.05) showed that the variables implicated in the recirculation system significantly affected the mean particle size and the process yield. The entrapment efficiencies of NPs prepared by the conventional method were not significantly different (α = 0.05) from those obtained by the recirculation system.     

Analysis of Micelle Formation of an Adriamycin-Conjugated Poly(Ethylene Glycol)–Poly(Aspartic Acid) Block Copolymer by Gel Permeation Chromatography

The micelle-forming behavior of a drug–block copolymer conjugate adriamycm-conjugated poly(ethylene glycol)–poly(aspartic acid) block copolymer; PEG-P[Asp(ADR)] was analyzed by gel permeation chromatography (GPC). Four compositions of the conjugates were observed to form micellar structures in aqueous media, and their micelle-forming behavior was found to be dependent on the composition and media. These micelles did not reach equilibrium within short time periods like low molecular weight surfactants. One composition formed stable micelles in the presence of serum.     

聚乙二醇-聚十六烷基氰丙烯酸酯聚合物及其纳米粒的制备

聚乙二醇氰乙酸酯和十六烷基氰乙酸酯聚合得到两亲性的标题聚合物,通过IR、1HNMR及凝胶渗透色谱法等确证结构.将此聚合物用溶剂-非溶剂法所制得的纳米粒粒径为100～400nm,分布均匀.     

Long Circulating Poly(Ethylene Glycol)-Decorated Lipid Nanocapsules Deliver Docetaxel to Solid Tumors

Purpose The purpose of this study was to evaluate the ability of poly(ethylene glycol)-coated lipid nanocapsules (LN) to deliver the highly potent hydrophobic anticancer drug docetaxel to solid tumors. Methods Docetaxel-loaded nanocapsules (80–120 nm) were produced by a solvent-free phase inversion process and were coated with polyethylene glycol distearoylphosphatidylethanolamine conjugate by a postinsertion step. In vivo studies were conducted in mice bearing subcutaneously implanted C26 colon adenocarcinoma to assess the pharmacokinetics and biodistribution of both the drug and LN. Results Incorporation of docetaxel into the LN dramatically increased the drug's biological half-life while providing substantial accumulation at the tumoral site. The pharmacokinetics and biodistribution pattern were found to depend on the specific surface area and shell composition of the nanocapsules. Conclusion This study demonstrates that docetaxel physically entrapped into a lipid colloidal drug carrier can be efficiently targeted to neoplastic tissues.     

Intracellular Delivery of Saquinavir in Biodegradable Polymeric Nanoparticles for HIV/AIDS

Purpose This study aims at developing poly(ethylene oxide)-modified poly(epsilon-caprolactone) (PEO-PCL) nanoparticulate system as an intracellular delivery vehicle for saquinavir, an anti-HIV protease inhibitor.Materials and Methods Saquinavir-loaded PEO-PCL nanoparticles were prepared by a solvent displacement process. The formed nanoparticles were characterized for size, surface charge, and surface presence of PEO chains. Cellular uptake and distribution of the nanoparticle was examined in THP-1 human monocyte/macrophage (Mo/Mac) cell line. Intracellular saquinavir concentrations were measured as a function of dose and duration of incubation.Results The PEO-PCL nanoparticles had a smooth surface and spherical shape and showed a relatively uniform size distribution with a mean particle diameter of approximately 200 nm. The surface presence of PEO chains was confirmed by an increase in the –C–O–(ether) signature of the C1s spectra in electron spectroscopy for chemical analysis. Rapid cellular uptake of rhodamine-123 encapsulated PEO-PCL nanoparticles was observed in THP-1 cells. Intracellular saquinavir concentrations when administered in the nanoparticle formulation were significantly higher than from aqueous solution.Conclusions This study shows that PEO-PCL nanoparticles provide a versatile platform for encapsulation of saquinavir and subsequent intracellular delivery in Mo/Mac cells.     

Improvement of physicochemical and biopharmaceutical properties of theophylline by poly(ethylene glycol) conjugates

In the present paper two theophylline esters with poly (ethylene glycol) (PEG) and methoxy poly (ethylene glycol) (mPEG) were prepared. Quantitative yields of the pure products were obtained. Unlike the free drug, the drug-polymer conjugates are freely water-soluble at room temperature. In vitro release experiments in aqueous buffer demonstrate that both conjugates are stable in buffer of pH 7.4 and 1.2. In vivo release studies after oral administration of theophylline conjugates demonstrate a good release of parent drug.     

Novel Polymeric Micelles Based on the Amphiphilic Diblock Copolymer Poly(N-vinyl-2-pyrrolidone)-block-poly(D,L-lactide)

Purpose. The purpose of this work was to synthesize a new amphiphilic diblock copolymer of poly(N-vinyl-2-pyrrolidone and poly(D,L-lactide) (PVP-b-PDLLA) capable of self-assembling into polymeric micelles with multiple binding sites and high entrapment efficiency. Methods. The copolymer was synthesized by ring-opening polymerization of D,L-lactide initiated by potassium PVP hydroxylate. It was characterized by gel permeation chromatography, ¹H- and ¹³C-NMR spectroscopy. The ability of the copolymer to self-assemble was demonstrated by dynamic and static light scattering, spectrofluorimetry and ¹H-NMR. The hydrophobic model drug indomethacin was incorporated into the polymeric micelles by a dialysis procedure. Results. A series of amphiphilic diblock copolymers based on PVP-b-PDLLA were successfully synthesized. The critical association concentrations in water were low, always below 15 mg/L. Micellar size was generally bimodal with a predominant population between 40 and 100 nm. PVP-b-PDLLA micelles were successfully loaded with the poorly water-soluble drug indomethacin and demonstrated an entrapment efficiency higher than that observed with control poly(ethylene glycol)-b-PDLLA micelles. It was hypothesized that specific interactions with the hydrophilic outer shell could contribute to the increase in drug loading. Conclusion. PVP-b-PDLLA micelles appear to exhibit multiple binding sites and thus represent a promising strategy for the delivery of a variety of drugs.     

Novel pH-sensitive hydrogels for colon-specific drug delivery

The purpose of this study is to develop novel intestinal specific drug delivery systems with pH-sensitive swelling and drug release properties. Acryloyl ester of 5-[4-(hydroxy phenyl) azo] salicylic acid (HPAS) as an azo derivative of 5-amino salicylic acid (5-ASA) was prepared under mild conditions. The HPAS was covalently linked with acryloyl chloride, abbreviated as APAS. Cubane-1,4-dicarboxylic acid (CDA), linked to two 2-hydroxyethyl methacrylate (HEMA) groups, was the cross-linking agent (CA). Methacrylic-type polymeric prodrugs were synthesized by free radical copolymerization of methacrylic acid, poly(ethyleneglycol monomethyl ether methacrylate), and APAS in the presence of cubane cross-linking agent. The effect of copolymer composition on the swelling behavior and hydrolytic degradation were studied in simulated gastric (SGF, pH 1) and intestinal fluids (SIF, pH 7.4). The composition of the cross-linked three-dimensional polymers was determined by FTIR spectroscopy. The hydrolysis of drug–polymer conjugates was carried out in cellophane membrane dialysis bags containing aqueous buffer solutions (pH 1 and pH 7.4) at 37°C. Detection of the hydrolysis product by UV spectroscopy shows that the azo prodrug (HPAS) was released by hydrolysis of the ester bond located between the HPAS and the polymer chain. Drug release studies showed that the increasing content of MAA in the copolymer enhances hydrolysis in SIF. These results suggest that pH-sensitive systems could be useful for preparation of a muccoadhesive system and controlled release of HPAS as an azo derivative of 5-amino salicylic acid (5-ASA).     

Chitosan and Chitosan/Ethylene Oxide-Propylene Oxide Block Copolymer Nanoparticles as Novel Carriers for Proteins and Vaccines

Purpose. The aim of this study was to investigate the interaction between the components of novel chitosan (CS) and CS/ethylene oxide-propylene oxide block copolymer (PEO-PPO) nanoparticles and to evaluate their potential for the association and controlled release of proteins and vaccines. Methods. The presence of PEO-PPO on the surface of the nanoparticles and its interaction with the CS was identified by X-ray photoelectron spectroscopy (XPS). The mechanism of protein association was elucidated using several proteins, bovine serum albumin (BSA), and tetanus and diphtheria toxoids, and varying the formulation conditions (different pH values and concentrations of PEO-PPO), and the stage of protein incorporation into the nanoparticles formation medium. Results. BSA and tetanus and diphtheria toxoids were highly associated with CS nanoparticles partly due to electrostatic interactions between the carboxyl groups of the protein and the amine groups of CS. PEO-PPO also interacted electrostatically with CS, thus competing with the proteins for association with CS nanoparticles. A visible amount of PEO-PPO was projected towards the outer phase of the nanoparticles. Proteins were released from the nanoparticles at an almost constant rate, the intensity of which was closely related to the protein loading. Furthermore, the tetanus vaccine was released in the active form for at least 15 days. Conclusions. CS and CS/PEO-PPO nanoparticles prepared by a very mild ionic crosslinking technique are novel and suitable systems for the entrapment and controlled release of proteins and vaccines.