Solution dynamics of 5-fluorouracil entrapped in poly lactic-co-glycolic acid (PLGA) microsphere—A study with 1D selective NMR methods

In this report, our main focus is to introduce a set of one-dimensional (1D) NMR methods based on chemical shift, relaxation, and magnetization transfer, namely, NOE and chemical exchange involving selective pulse excitation to study the solution dynamics of drug in free and encapsulated state within polymeric microsphere. In this regard 5-fluorouracil (5-FU) loaded poly lactic-co-glycolic acid (PLGA) microspheres are prepared as model system via standard water-in-oil-in-water emulsification method. One-dimensional ¹H and ¹⁹F nuclear magnetic resonance (NMR) spectra of 5-FU in presence of PLGA microspheres presented a significant change in linewidth and relaxation rates compared with free 5-FU confirming encapsulation. Furthermore, loss of coupling pattern in ¹H and ¹⁹F NMR of PLGA encapsulated 5-FU as compared with free 5-FU suggests an enhanced –NH and –H₂O protons exchange dynamics in the interior of the microsphere indicating hydrated microsphere cavity. Quantification of exchange dynamics in case of free and PLGA-encapsulated 5-FU was attempted employing 1D selective NOESY and 1D multiply selective inversion recovery experiments. Analysis of the exchange rates confirmed existence of more than one kind of water population within the cavity as mentioned in an earlier solid state NMR report.     

Novel Carboxymethyl Chitosan Microspheres for Controlled Delivery of Chelerythrine

Novel carboxymethyl chitosan (O-CMCS) microspheres containing an anti-tumor drug chelerythrine (CHE) have been successfully prepared by an emulsion crosslinking method using glutaraldehyde. The optimized microsphere formulation was characterized for particle size, shape, morphology, crystallinity and in vitro drug release. Results for mean particle size, drug loading content, entrapment efficiency and in vitro drug release of chelerythrine loaded microspheres were found to be 12.18 μm, 4.08%, 54.78% and 35.30% at pH 7.4 in 20 h, respectively. The optimized microspheres had an imperfect crystalline lattice and a spherical, rough morphology and the CHE release from O-CMCS microspheres followed the Higuchi matrix model. All these results suggested that O-CMCS microspheres are a promising carrier system for controlled drug delivery.     

壳聚糖丝心蛋白包药微球的结构和释放性能研究

近年,高分子微球的研究与开发十分引人注目.将药物包裹于微球中,经主动和被动控制,进入预定靶器官或组织后缓慢释放出,不仅可降低其毒副作用,还可提高其生物活性利用度,壳聚糖(ＣＳ)可作牛血清白蛋白等药物缓释微球的载体[1～3].丝心蛋白(ＦＢ)含18种氨基酸,具有多孔性和良好的渗透性[4],也是一种理想的生物材料.壳聚糖和丝心蛋白共混可交联成半互穿聚合物网络(ＳｅｍｉＩＰＮ)结构.具有智能水凝胶的性能[5].本实验室已用纤维素铜氨液分别与干酪素、海藻酸钠及魔芋共混制得共混膜,两种分子间存在由次价键力引起的很强的相互作用,使其力学性…     

Graft copolymers having hydrophobic backbone and hydrophilic branches. X. Preparation and properties of water-dispersible polyanionic microspheres having poly(methacrylic acid) branches on their surfaces

The free radical copolymerization of poly(t-butyl methacrylate) (PBMA) macromonomer with styrene in ethanol give monodispersed microspheres with 0.8-1.6 μm diameter. The resulting microspheres were treated with HCl solution to convert into anionic microspheres having poly(methacrylic acid) chains. ESCA analysis of the microsphere surface suggested that PBMA chains were favorably located on the surface of the microspheres. The particle size of the microspheres decreased with increasing molecular weight and concentration of the macromonomer. Water dispersibilities of the microspheres were evaluated by measuring the relative turbidity of the suspension of microspheres as a function of pH. The results show that they were strongly dependent on pH. © 1995 John Wiley & Sons, Inc.     

Development of biodegradable co-poly( -lactic/glycolic acid) microspheres for the controlled release of 5-FU by the spray drying method

The water-soluble anti-cancer drug, 5-fluorouracil (5-fluoro-2,4-pyrimidinedione) (5-FU) is encapsulated into biodegradable co-poly ( -lactic/glycolic acid) (PLGA) using the spray drying method for the development of long-lasting controlled release systems. In this study, the effects of both polymeric composition and technological parameters on release profiles of 5-FU were investigated. The degradation of various microspheres was also investigated. The mixture of dichloromethane/chloroform/methanol (1:1:2 v/v) instead of dichloromethane/chloroform (1:1 v/v) resulted in the modification of morphology, while the physical structure of the microsphere varied from a porous PLGA microsphere to a dense PLGA microsphere. The results show that the average diameter was 2 μm and the anti-cancer drug loading of microspheres approached approximately 8% (w/w). In addition, the lactide/glycolide ratio of the polymer is an important parameter for controlling the release profile of the entrapped anticancer drug. Our results indicate that the mixture solvent using the spray drying method was more efficient than emulsification solvent diffusion.     

Formulation and Evaluation of 5-FU Loaded Eudragit Microspheres: Effect of Various Eudragit on Micromeretic Properties of Microspheres

The aim of the present study was to prepare and evaluate microspheres of Eudragit (RS, RL and RSPO) containing an anticancer drug 5-FU. Microspheres were prepared by O/O solvent evaporation method using a acetone/liquid paraffin system. Magnesium stearate was used as the droplet stabilizer and n-hexane was added to harden the microspheres. The prepared microspheres were characterized for their micromeretic properties and entrapment efficiency; as well by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray powder diffractometry (XRPD), thin layer chromatography (TLC) and scanning electron microscopy (SEM) revealed the crystalline nature of drug in a final state. The in vitro release studies were performed in a Phosphate Buffer Solution (PBS) pH 7.4. The best fit release kinetics was achieved with a Higuchi plot. The yields of preparation and entrapment efficiencies were very high with a larger particle size for all the formulations. Mean particle size, entrapment efficiency and production yield were highly influenced by the type of polymer and polymer concentration. It is concluded from the present investigation that various Eudragit are promising controlled release carriers for 5-FU.     

Preparation and properties of monodispersed rifampicin-loaded poly(lactide-co-glycolide) microspheres

Monodispersed rifampicin (RFP)-loaded poly(lactide-co-glycolide) (PLGA) microspheres were prepared by a solvent evaporation method. In order to control the sizes of the microspheres, a membrane emulsification technique using Shirasu porous glass (SPG) membranes was applied. RFP/PLGA microspheres with the average diameters of 1.3, 2.2, 5.2, and 9.0 microm were obtained. They were relatively monodisperse and the values of the coefficient of variation (CV) for the size distributions of the microspheres were in the range between 7.0 and 16.0%. The loading efficiency of RFP was in the range between 50.3 and 67.4% independent of the microsphere size. The release ratio of RFP from RFP/PLGA microspheres was measured in pH 7.4 PBS at 37 degrees C. From RFP/PLGA microspheres with average diameters of 1.3 and 2.2 microm, almost 60% of RFP loaded in the microspheres was released in the initial day and the release was terminated almost within 10 days. On the other hand, from those with average diameters of 5.2, and 9.0 microm, the release of RFP was observed even 20 days after the release started.     

Synthesis of NiO nanomaterials with various morphologies and their electrocatalytic performances for <Emphasis Type="Italic">p</Emphasis>-nitrophenol reduction

In the work, several facile and easily controlled procedures were designed to successfully synthesize a few NiO samples with various morphologies, including nanosheets, nanobelts, nanoparticles and empty microspheres, via a hydrothermal method. The as-prepared samples were characterized by X-ray powder diffractometer, TEM and field emission scanning electron microscopy technologies. The results revealed that the as-synthesized NiO samples displayed expected nanosheets, nanobelts, nanoparticles and empty microspheres in shape. The electrocatalytic performance of each NiO sample modified on a glassy carbon electrode for p-nitrophenol reduction in a basic solution using cyclic voltammetry method was investigated. The results indicated that the glassy carbon electrode modified with each NiO sample showed enhanced electrocatalytic activity by comparing a bare glassy carbon electrode, and especially NiO nanopatricles and empty microsphere exhibited the higher electrocatalytic activty for p-nitrophenol reduction.     

作为细胞微载体的明胶基缓释微球的制备

用改良的乳化冷凝法制备载牛血清蛋白(BSA)的大粒径明胶微球. 结果表明, 明胶水溶液的质量分数为25%、水相与油相体积比3∶20、搅拌速度300 r/min、交联剂用0.1 mL质量分数为25%的戊二醛、 表面活性剂用0.1 g span-80为制备平均直径约250 μm明胶微球的理想条件. 所制备微球的后处理方法不同, 则明胶微球的表面形貌也不同, 细胞粘附率不同. 空白明胶微球在体外可以完全降解, 载BSA的明胶微球对BSA具有良好的缓释性, 释放时间可长达30 d. 显微镜观察成纤维细胞在明胶微载体上生长良好.     

Preparation of biodegradable polyesteramide microspheres

Biodegradable polyesteramide copolymer P(CL/AU) based on -caprolactone and 11-aminoundecanoic acid was synthesized by the melt polycondensation method. Polyesteramide (PEA) microspheres were prepared by a simple O/W emulsion solvent evaporation method. The effects of variations in preparation parameters (such as emulsifier concentration, polymer concentration, polymer solution adding rate, stirring rate, and whether vacuum was applied) were studied in detail. The obtained microsphere morphologies were observed using an optical microscope and via scanning electron microscopy (SEM). The particle size distribution was determined using a Malvern laser particle sizer. When the PEA microspheres were incubated in PBS saline, the particle size increased at first, and then decreased after a longer time period; the theory that this behavior was due to degradation of the microspheres was confirmed by SEM.     

Interpenetrating polymer network microspheres of hydroxy propyl methyl cellulose/poly (vinyl alcohol) for control release of ciprofloxacin hydrochloride

Hydroxypropylmethylcellulose and Poly (vinyl alcohol) blend microspheres were prepared by water in oil emulsion method and Ciprofloxacin Hydrochloride (CFHcl) was loaded into the interpenetrating polymer network (IPN) microspheres that are crosslinked with glutaraldehyde (GA). Blend microspheres were characterized using Fourier transform infrared Spectroscopy (FT-IR), Scanning electron microscopy, X-ray diffraction and Differential scanning Calorimetry. FTIR spectra results confirmed crosslinking reaction between –OH groups of Poly (vinyl alcohol) and –CHO groups of glutaraldehyde. Scanning electron micrograph showed the formation of plain, uniform and smooth microspheres. X-ray diffraction and thermal studies of plain and drug loaded microspheres indicates that the drug is dispersed at the molecular level in the IPN matrix. In vitro dissolution experiments were performed in pH 7.4 buffer medium at 35 °C which indicates a sustained and controlled release of ciprofloxacin hydrochloride (CFHcl) from the IPN microspheres up to 10 h.     

Genipin crosslinked microspheres as an effective hemostatic agent

Efficient hemorrhage control is of extreme importance to decrease mortality rates arising from traumatic bleeding. However, traditional hemostatic agents are limited to unsatisfied biocompatibility, inconvenient usage, and high cost. To this end, we have devised a novel hemostatic microsphere from chitosan and gelatin by using appropriate amount of genipin as a crosslinker. The performance of these Cs/Gel MPs was evaluated with experiments in vitro and in vivo. Results in vitro showed that the best hemostatic efficacy was achieved by Cs/Gel‐0.75 MPs (the mass fraction of genipin in Cs/Gel mixture is 8.6 × 10⁻⁶). Skin laceration model indicated that the hemostatic time of Cs/Gel‐0.75 MPs was within 12 seconds, which has been significantly shortened in comparison with commercial available products. Moreover, cytocompatibility results displayed that Cs/Gel‐0.75 MPs caused no obvious cytotoxicity even at the high concentration of 40 μg/ml. Cs/Gel‐0.75 MPs also possess satisfactory fluid absorption ratio and low hemolysis. Therefore, these Cs/Gel‐0.75 MPs are promising candidates for further surgical wound hemostatic agent.     

INVESTIGATION OF POLYDL-LACTIDE-b-POLY（ETHYLENE GLYCOL）-b-POLYDL-LACTIDE MICROSPHERES CONTAINING PLASMID DNA

PolyDL-lactide (PDLLA) and the block copolymer, polyDL-lactide-b-poly(ethylene glycol)-b-polyDL-lactide (PELA) were used as the microsphere matrix to encapsulate plasmid DNA. The PDLLA, PELA, pBR322-1oaded PDLLA and pBR322-1oaded PELA microspheres were prepared by solvent extraction method based on the formation of multiple w1/o/w2 emulsion. The microspheres were characterized by surface morphology, mean particle size, particle size distribution and loading efficiency. The integrity of DNA molecules after being extracted from microspheres was determined by agarose gel electrophoresis. The result suggested that plasmid DNA molecules could retain their integrity after being encapsulated by PELA. The PELA microspheres could prevent plasmid DNA from being digested by DNase. The in vitro degradation and release profiles of plasmid DNA-loaded microspheres were measured in pH - 7.4 buffer solution at 37℃. The in vitro degradation profiles of the microspheres were evaluated by the deterioration in microspheres surface morphology, the molecular weight reduction of polymer, the mass loss of microspheres, the changes of pH values of degradation medium, and the changes of particle size. The in vitro release profiles of the microspheres were assessed by measurement of the amount of DNA presented in the release medium at determined intervals. The release profiles were correlation with the degradation profiles. The release of plasmid DNA from PELA microspheres showed a similar biphasic trend, that is, an initial burst release was followed by a slow, but sustained release.     

A spheres-in-sphere structure for improving protein-loading poly (lactide-co-glycolide) microspheres

In present study, protein loaded poly (lactide-co-glycolide)/chitosan microspheres (PLGA/CS MSs) with spheres-in-sphere structure were prepared in order to weaken the burst release of protein from PLGA microspheres (PLGA MSs) and to buffer acidic micro-milieu. The PLGA MSs and PLGA/CS MSs were characterized in terms of their size distribution, morphology, drug-loading rate, zeta potential and physical-chemical properties. The incubation experiments of PLGA MSs and PLGA/CS MSs were manipulated in PBS solution at pH 7.4, 37 °C to monitor the release of BSA and the vehicles degradation. The release kinetic of BSA was illuminated mainly based on the degradation processes of the matrices. External CS crusts were proved to strikingly improve the release kinetic of the model protein by reducing initial burst release and extending continuous release while acting as a diffusion barrier. Moreover, using PLGA/CS MSs could avoid the decrease of pH value resulted from the acidic products of PLGA MSs because of the effective buffer action of the basic groups in CS. The results demonstrated that the spheres-in-sphere structure is an effective way to control the initial burst release of protein and to overcome the acidic problem of protein-loading PLGA MSs.     

离子凝胶反应法制备壳聚糖/N,O-羧甲基壳聚糖微球

以一氯乙酸与壳聚糖反应形成N,O-羧甲基壳聚糖两性聚电解质,分光光度法测定其等电点IEP=2．86。以此两性聚电解质与壳聚糖可以在一定条件下形成微球,光学显微镜和电子显微镜测试表明,控制两种聚电解质配比可以制备不同粒径大小的微球,而超声功率对微球粒径的影响较小。红外光谱测试表明微球中N,O-羧甲基壳聚糖羧基以羧酸根形式存在,分光光度与电导法联合测定表明两种聚电解质以离子凝胶作用形成微球,其最佳制备条件为IEP（CM-CHITOSAN）〈pH〈pKa（CS）,在此较宽的pH值范围内微球可稳定存在。     

Preparation and Characterization of Vanillin Cross-Linked Chitosan Microspheres of Pterostilbene

A vanillin cross-linked chitosan microsphere delivery system was established for stabilization and controlled release of pterostilbene. The prepared microspheres were characterized by SEM images, FT-IR spectra, thermogravimetry, and X-ray diffraction. FT-IR spectra results indicated that chitosan was cross-linked by vanillin successfully. Thermal analysis showed that pterostilbene had been totally incorporated into the microspheres and the encapsulation of pterostilbene decreases the rate of degradation and increases the stability. XRD analysis was conducted to confirm the results of DSC analysis. The release rate of pterostilbene from microspheres in pH 3.6 buffer solution could be up to 58.1 % within 48 h.     

Core–Shell Hollow Microspheres of Magnetic Iron Oxide@Amorphous Calcium Phosphate: Synthesis Using Adenosine 5′‐Triphosphate and Application in pH‐Responsive Drug Delivery

Drug nanocarriers with magnetic targeting and pH‐responsive drug‐release behavior are promising for applications in controlled drug delivery. Magnetic iron oxides show excellent magnetism, but their application in drug delivery is limited by low drug‐loading capacity and poor control over drug release. Herein, core–shell hollow microspheres of magnetic iron oxide@amorphous calcium phosphate (MIO@ACP) were prepared and investigated as magnetic, pH‐responsive drug nanocarriers. Hollow microspheres of magnetic iron oxide (HMIOs) were prepared by etching solid MIO microspheres in hydrochloric acid/ethanol solution. After loading a drug into the HMIOs, the drug‐loaded HMIOs were coated with a protective layer of ACP by using adenosine 5′‐triphosphate (ATP) disodium salt (Na₂ATP) as stabilizer, and drug‐loaded core–shell hollow microspheres of MIO@ACP (HMIOs/drug/ACP) were obtained. The as‐prepared HMIOs/drug/ACP drug‐delivery system exhibits superparamagnetism and pH‐responsive drug‐release behavior. In a medium with pH 7.4, drug release was slow, but it was significantly accelerated at pH 4.5 due to dissolution of the ACP shell. Docetaxel‐loaded core–shell hollow microspheres of MIO@ACP exhibited high anticancer activity.     

Synthesis of PEGylated hyaluronic acid for loading dichloro(1,2-diaminocyclohexane)platinum(Ⅱ)(DACHPt) in nanoparticles for cancer treatment

Dichloro(1,2-diaminocyclohexane)platinum(II)(DACHPt), a cisplatin(CDDP) analog, has shown lower toxicity than CDDP and no cross-resistance with CDDP in many CDDP-resistant cancers. PEGylated hyaluronan(m PEG-HA) is an m PEG conjugated with hyaluronan biodegradable polymer which is a naturally occurring biopolymer in the interstitium, is primarily cleared by the lymphatic system. m PEGhyaluronan–DACHPt(PEG-HA–Pt) conjugate could circulate long-term in the bloodstream and increase DACHPt concentration in the tumor site and decrease systemic toxicity. m PEG-HA conjugates with the range of 1%–5% substitution were synthesized, and the structures were confirmed by1 H NMR and IR. The particle size of DACHPt incorporated with m PEG-HA was about 86 nm and the loading content and efficiency were about 19%(w/w) and 86%, respectively. The synthesized m PEG-HA with different PEG substitution degrees presented non toxicity, and the cell viability of DACHPt loaded in m PEG-HA nanoparticles increased with increasing doses of DACHPt. DACHPt release from nanoparticles slightly decreased with increasing PEG substitution degree from 1% to 5% at 37 8C, pH 7.4 PBS solution. The DACHPt loaded in m PEG-HA nanoparticles significantly inhibited the growth of A549 xenografts in nude mice when compared to the DACHPt loaded in HA nanoparticles and the control group after 4 weeks treatment(p 0.01 compared with control). The body weight change curve shows that the mice weight loss was less than 5% by treating with both DACHPt loaded in m PEG-HA and HA nanoparticles. In conclusion, a novel DACHPt loaded m PEG-HA delivery system was developed with sustained release and increased platinum concentration in the tumor.     

Crosslinked Networks Based on Polysaccharides and Collagen for Pilocarpine Sustained Release

The paper presents the experimental studies regarding synthesis and characterization of hydrogels based on gellan (Gel)/chitosan (CS) and collagen (Col), obtained by crosslinking with glutaraldehyde (GLA). The influence of the polysaccharide content and GLA ratio on the final composition and swelling characteristics was evaluated. Hydrogels swelling analysis, in distilled water and phosphate buffer (PBS, pH 7.2) has shown higher swelling degrees at increased concentration of polysaccharide into hydrogels. In vitro release of pilocarpine has demonstrated the possibility to use gellan-collagen and chitosan-collagen hydrogels as ophthalmic drug delivery matrix.     

Effects of lung surfactants on rifampicin release rate from monodisperse rifampicin-loaded PLGA microspheres

We have prepared inhalable and monodisperse poly(lactide-co-glycolide) (PLGA) microspheres targeting tubercle bacilli residing in alveolar macrophages. The effects of pulmonary surfactant on the rifampicin (RFP) release rate from RFP-loaded poly (lactide-co-glycolide) microspheres were studied. Also, those of their surface properties of RFP-loaded PLGA microspheres were studied. The RFP release from RFP/PLGA microspheres was accelerated by adsorption of pulmonary surfactant on the particle surface. The fastest RFP release rate was observed from pulmonary surfactant-adsorbed PLGA particles in pH 7.4 buffer solution compared with those in pH 4.0 buffer solution and saline solution. The slowest release rate was observed in the case when saline solution was used as dispersion phase of RFP/PLGA microspheres, although RFP release rate increased by the addition of pulmonary surfactant. From these results it is suggested that when RFP/PLGA microspheres are administrated by inhalation, the RFP release rates from the particles which are not taken up by alveolar macrophages and remain in the alveoli will be small. On the other hand, the RFP release rates and release amounts will be high after RFP/PLGA microspheres are taken up by alveolar macrophages existing in phagosomes, but they become relatively small after RFP/PLGA microspheres move into phagosome-lysosomes by the fusion of phagosomes with lysosomes. The absolute values of the electrophoretic mobility of PLGA microspheres increased by the adsorption of pulmonary surfactants on the surfaces of PLGA microspheres. By analyzing the experimental data using the soft-particle theory, it was indicated that the microspheres became 'softer' and the surface charge density of microspheres increases by the degradation. On the other hand, the surface of PLGA microspheres became harder and the electric charge density increased by the adsorption of pulmonary surfactant on the surfaces of PLGA microspheres. The changes in the surface charge density with degradation became larger by the adsorption of the lung surfactant on PLGA microsphere surfaces. It is considered that the changes in surface properties of PLGA microspheres affect their uptake efficiency by alveolar macrophage.