pH-sensitive nanoparticles of poly(amino acid) dodecanoate complexes

Nanoparticles were formed by the complexation of poly( -arginine) (PLA), poly( -histidine) (PLH) and poly( -lysine) (PLL) with dodecanoic acid (C12). Dynamic light scattering, ζ potential measurements, atomic force microscopy, fluorescence, and circular dichroism spectroscopy were used for their characterization. It was found that the diameters of the poly( -arginine) dodecanoate (PLA-C12), poly( -histidine) dodecanoate (PLH-C12), and poly( -lysine) dodecanoate (PLL-C12) complex nanoparticles were in the range 120–200 nm. Furthermore, the pH-sensitive dissolution and the surface charges can be adjusted by choosing PLA, PLH and PLL. The particle stability against basic pH values increases with increasing pK_a value of the poly(amino acid) in the series PLH-C12, PLL-C12 and PLA-C12. The particles as such show a core-shell morphology. Their cores are formed by stoichiometric poly(amino acid) dodecanoate complexes while the shells stabilizing the particles are formed by cationic poly(amino acid) chains in an uncomplexed state. The particles were tested as containers for hydrophobic molecules such as pyrene, which served as a fluorescence probe for measuring the polarity within the particles, and Q₁₀ which functioned as a model drug. The maximum uptake of Q₁₀ into the nanoparticles is about 13% (w/w), thereby making the complexes attractive as simple drug carriers for controlled release purposes. Circular dichroism measurements revealed that the poly(amino acid) chains of PLA-C12 and PLL-C12 adopt predominantly an -helix and that of PLH-C12 a β-sheet.     

羟基喜树碱pH敏感阳离子纳米脂质体的制备

 目的 以羟基喜树碱作为模型药物研究pH敏感阳离子纳米脂质体用于包载抗癌药物的制备工艺。方法 采用薄膜分散法制备羟基喜树碱阳离子脂质体;用羧甲基壳聚糖物理修饰阳离子脂质体;用葡聚糖凝胶柱色谱法分离游离药物;用紫外分光光度法测定包封率;用单一因素考察法优选处方;经高压乳匀得到纳米脂质体(粒径小于100 nm);用激光粒度分析仪测定Zeta电位、粒径大小。结果 最佳处方制备的药物平均包封率为(78.5±0.9)％(n=3);包衣纳米脂质体的Zeta电位为-31.3 mV,平均粒径为96 nm。结论 使用本方法制备pH敏感阳离子纳米脂质体工艺简单,有望获得高靶向性的抗癌药物传递系统。     

Physicochemical aspects of doxorubicin-loaded pH-sensitive polymeric micelle formulations from a mixture of poly(l-histidine)-b-poly(l-lactide)-b-poly(ethylene glycol)

In this study, doxorubicin (DOX) was physically incorporated into pH-sensitive micelles made from a mixture of poly(l-histidine)-b-poly(ethylene glycol)/poly(l-lactide)-b-poly(ethylene glycol) (75/25, wt.%). The DOX-loaded mixed micelles were formulated using dialysis methods and optimal DOX incorporation was achieved at a drug/polymer feed ratio of 0.2 (wt./wt.) when a proper amount of aqueous phase (0.2, v./v.) was added into the common solvent (DMSO) solution, followed by dialysis at 4 °C. Based on the results obtained from dynamic light scattering, UV-Vis absorption, and fluorescence experiments, it was demonstrated that the encapsulated drugs were mainly located inside the hydrophobic micelle cores, well protected and inaccessible to the exterior molecules. Under in vitro conditions, although the microstructure of the micelles was altered below pH 8.0 by the encapsulated drugs, the drug-loaded micelles still exhibited a desirable ability to control the drug release in response to tumor extracellular pH.     

pH敏感前体阳离子脂质体的制备及瘤内分布研究

 目的 以羟喜树碱作为模型药物研究pH敏感前体阳离子脂质体用于包载抗癌药物的制备工艺并考察其pH敏感性及荷瘤鼠体内药动学特性。方法 采用薄膜分散法制备羟喜树碱阳离子脂质体;用羧甲基壳聚糖物理修饰阳离子脂质体;分离游离药物后测定包封率;用激光粒度分析仪测定Zeta电位、粒径大小;采用鸡红细胞溶血实验分析其pH敏感性并考察不同时刻药物在荷瘤小鼠血浆及瘤内浓度。结果 平均包封率为(78.5±0.9)％(n=3);Zeta电位为-31.3 mV,平均粒径为96 nm。溶血实验显示pH敏感前体阳离子脂质体与红细胞膜融合作用有明显的pH值敏感性,荷瘤小鼠体内实验显示pH敏感前体阳离子脂质体瘤内分布较高。结论 本方法制备的pH敏感前体阳离子脂质体作用机制独特,瘤内浓度高,有望成为靶向肿瘤药物的传递系统。
     

Enhanced Intercellular Retention Activity of Novel pH-sensitive Polymeric Micelles in Wild and Multidrug Resistant MCF-7 Cells

Purpose The purpose of this work was to demonstrate the advantage of using pH-sensitive polymeric mixed micelles (PHSM) composed of poly(l-histidine) (polyHis)/poly(ethylene glycol) (PEG) and poly(l-lactic acid) (pLLA)/PEG block copolymers with folate conjugation to increase drug retention in wild-type and MDR tumor cells. Materials and Methods Both wild-type and multidrug resistant (MDR) human breast adenocarcinoma (MCF-7) cell lines were used to investigate the accumulation and elimination of doxorubicin (DOX), PHSM with folate (PHSM/f), and pH-insensitive micelles composed of pLLA/PEG block copolymer with folate (PHIM/f). Results Cells treated with PHSM/f showed decelerated elimination kinetics compared to cells treated with PHIM/f. MDR cells treated with drug-containing PHSM/f for 30 min retained 80% of doxorubicin (DOX) even after incubation for 24 h in the absence of drug. On the other hand, cells treated with drug-containing PHIM/f retained only 40% of DOX within the same period of time. Flow cytometry and confocal microscopy confirmed these results. Conclusions Cellular entry of the micelles occurred via receptor-mediated endocytosis using folate receptors. The pH-induced destabilization of PHSM/f led to rapid distribution of drug and polymer throughout the cells, most likely due to polyHis-mediated endosomal disruption. This reduced the likelihood of drug efflux via exocytosis from resistant tumor cells.     

Programming the composition of polymer blend particles for controlled immunity towards individual protein antigens

In order for a more precise control over the quality and quantity of immune responses stimulated by synthetic particle-based vaccines, it is critical to control the colloidal stability of particles and the release of protein antigens in both extracellular space and intracellular compartments. Different proteins exhibit different sizes, charges and solubilities. This study focused on modulating the release and colloidal stability of proteins with varied isoelectric points. A polymer particle delivery platform made from the blend of three polymers, poly(lactic-co-glycolic acid) (PLGA) and two random pH-sensitive copolymers, were developed. Our study demonstrated its programmability with respective to individual proteins. We showed the colloidal stability of particles at neutral environment and the release of each individual protein at different pH environments were dependent on the ratio of two charge polymers. Subsequently, two antigenic proteins, ovalbumin (OVA) and Type 2 Herpes Simplex Virus (HSV-2) glycoprotein D (gD) protein, were incorporated into particles with systematically varied compositions. We demonstrated that the level of in vitro CD8⁺ T cell and in vivo immune responses were dependent on the ratio of two charged polymers, which correlated well with the release of proteins. This study provided a promising design framework of pH-responsive synthetic vaccines for protein antigens of interest.     

Preparation and Swelling Behaviors of High-Strength Hemicellulose-g-Polydopamine Composite Hydrogels

Hemicellulose-based composite hydrogels were successfully prepared by adding polydopamine (PDA) microspheres as reinforcing agents. The effects of PDA microsphere size, dosage, and nitrogen content in hydrogel on the mechanical and rheological properties was studied. The compressive strength of hydrogel was increased from 0.11 to 0.30 MPa. The storage modulus G’ was increased from 7.9 to 22.0 KPa. The gaps in the hemicellulose network are filled with PDA microspheres. There is also chemical cross-linking between them. These gaps increased the density of the hydrogel network structure. It also has good water retention and pH sensitivity. The maximum cumulative release rate of methylene blue was 62.82%. The results showed that the release behavior of hydrogel was pH-responsive, which was beneficial to realizing targeted and controlling drug release.     

茶碱分子表面印迹微球的制备及其体外释药性能

通过分子表面印迹技术,采用铈盐-羟基氧化还原引发体系,以交联聚乙烯醇(CPVA)微球为基质、对苯乙烯磺酸钠(SSS)为功能单体、茶碱(TP)为模板药物分子、N,N′-亚甲基双丙烯酰胺(MBA) 为交联剂,制备了TP分子表面印迹微球MIP-PSSS/CPVA。采用红外光谱测定其结构,扫描电镜观察其表面形貌,静态法考察印迹微球MIP-PSSS/CPVA对TP的结合性能及载药印迹微球的体外释药行为。结果表明：TP分子表面印迹微球MIP-PSSS/CPVA对TP具有较高的识别选择性和结合亲合性,当pH=1时,微球对TP的结合容量达到92 mg/g。该印迹微球在模拟胃液中基本不释药;在模拟小肠液中的第2~6 h,累积释放率仅为21%;而在模拟结肠液中突释,之后持续缓慢地释放,表现出优良的pH敏感和时滞双重型结肠定位释药特性。     

Surface modification of doxorubicin-loaded nanoparticles based on polydopamine with pH-sensitive property for tumor targeting therapy

One major challenge of current surface modification of nanoparticles is the demand for chemical reactive polymeric layers, such modification is always complicated, inefficient, and may lead the polymer lose the ability to encapsulate drug. To overcome this limitation, we adopted a pH-sensitive platform using polydopamine (PDA) as a way of functionalizing nanoparticles (NPs) surfaces. All this method needed to be just a brief incubation in weak alkaline solution of dopamine, which was simple and applicable to a variety of polymer carriers regardless of their chemical reactivity. We successfully conjugated the doxorubicin (DOX)-PDA-poly (lactic-co-glycolic acid) (PLGA) NPs with two typical surface modifiers: folate (FA) and a peptide (Arg-Gly-Asp, RGD). The DOX-PDA-FA-NPs and DOX-PDA-RGD-NPs (targeting nanoparticles) were characterized by particle size, zeta potential, and surface morphology. They were quite stable in various physiological solutions and exhibited pH-sensitive property in drug release. Compared to DOX-NPs, the targeting nanoparticles possessed an excellent targeting ability against HeLa cells. In addition, the in vivo study demonstrated that targeting nanoparticles achieved a tumor inhibition rate over 70%, meanwhile prominently decreased the side effects of DOX and improve drug distribution in tumors. Our studies indicated that the DOX-PLGA-NPs modified with PDA and various functional ligands are promising nanocarriers for targeting tumor therapy.     

Pharmacokinetic evaluation of quetiapine fumarate controlled release hybrid hydrogel: a healthier treatment of schizophrenia

The current study aimed to rationally develop and characterize pH-sensitive controlled release hydrogels by graft polymerization of gelatin (Gel) and hydroxypropyl methyl cellulose (HPMC) in the presence of glutaraldehyde (GA) using quetiapine fumarate for the treatment of schizophrenia. The prepared hydrogels discs were subjected to various physicochemical studies including: swelling, diffusion, porosity, sol-gel analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy. Three different pH values (1.2, 6.8 and 7.4) were used to determine shape, transition, and controlled release behavior of prepared hydrogels. Various kinetic models including zero order, first order, Higuchi model and Power Law equation were applied on drug release data. The optimized hydrogels were subjected to in vivo studies using albino rabbits. Swelling and release results were found to be insignificant (p?In-vivo studies contributed significantly higher plasma QTP-F concentration (C_max), time for maximum plasma concentration (T_max), area under the curve (AUC_0–inf) and half-life (t_1/2) as 18.32?±?0.50 µg/ml, 8.00?±?0.01?hrs, 6021.2?±?5.09 µg.hrs/ml and 10.06?±?0.43?hrs, respectively, for test-hydrogels when compared to reference market brand (Qusel^® 200?mg, Hilton Pharma, Karachi, Pakistan) QTP-F tablets. It might be concluded that QTP-F loaded pH-sensitive hydrogels were developed successfully with reduced dosing frequency for schizophrenia.