Antitumor Efficacy and Toxicity of 5-Fluorouracil-Loaded Poly(Lactide Co-glycolide) Pellets

The aim of this study was to formulate a biodegradable implant capable of imparting local antitumor activity through the sustained release of the chemotherapeutic agent, 5-fluorouracil (5-FU). Thus, injectable pellets (<1.2 mm diameter) made from poly(lactide co-glycolide) (PLGA) and loaded with 5-FU at varying drug:polymer ratios were fabricated using hot-melt extrusion and tested for their ability to provide sustained release of 5-FU in in vitro and in vivo settings. In addition, these formulations were compared against soluble 5-FU for their antitumor activity in vivo as well as for their toxicity. It was demonstrated that the release rate of 5-FU from PLGA pellets was directly related to the percentage of 5-FU in the pellets. PLGA pellets loaded with 50% w/w 5-FU exhibited comparable, and significantly enhanced, antitumor activity (as measured by tumor volumes and survival) in vivo in a thymoma and colon cancer model, respectively, when compared to an equivalent bolus dose (120 mg/kg) of soluble 5-FU. We concluded that 5-FU-loaded PLGA pellets were more effective and specifically less erythrotoxic than 5-FU bolus injections and therefore may prove to be of benefit as an intraoperative adjunct therapy for patients with cancers that are sensitive to 5-FU and who are undergoing tumor resection.     

Topical delivery of urea encapsulated in biodegradable PLGA microparticles: O/W and W/O creams

This study describes the formulation and characterization of O/W and W/O creams containing urea-loaded microparticles prepared with poly (D, L-lactic-co-glycolic acid) (PLGA) in order to encapsulate and stabilize urea. The solvent evaporation method was used for preparing PLGA microparticles containing urea. The microparticles size was evaluated by laser light diffractometry. The resulting microparticles were then incorporated in O/W and W/O creams and stability and the release pattern from the creams was evaluated by UV-spectrophotometry. The particle size of PLGA microparticles was in the range of 1–5 µm and most microparticles had a particle size smaller than 3 µm. The encapsulation efficiency was calculated as 40.5%?±?3.4. This study also examined release pattern of urea which varied among different formulations. The results showed that the release from O/W creams followed Higuchi kinetics while the release from W/O creams showed the zero order kinetics and the creams containing microparticulated urea had slower release than free urea creams.     

Biodegradable three-dimension micro-device delivering 5-fluorouracil in tumor bearing mice

A novel three-dimension micro-device was formulated to control delivery of 5-fluorouracil (5-FU) for the treatment of solid tumors. The poly-(lactic-co-glycolic) acid (PLGA), which is both biocompatible and biodegradable, was used as carrier material. The characteristics of drug release in vitro and in vivo and the performance of the micro-device after implantation in tumor bearing mice were evaluated. A constant release profile from in vitro test was obtained for a period of 7 days, and it correlated well with the in vivo release profile. In the distribution experiment of 5-FU micro-device, it was demonstrated that 5-FU remained in the tumor tissues for more than 7 days after implantation. Likewise, we found that the 5-FU concentration in tumor correlated well with the in vivo release. Tumors treated with 5-FU loaded micro-device of three different dosages showed significant tumor reduction (P < 0.05) compared with empty control micro-device 7 days after administration. Moreover, the implantation treatment showed enhanced efficacy compared with the intraperitoneal administration with the same dosage. These results suggested that the three-dimensional micro-device may provide a promising local and controlled release drug delivery system, which may enable delivery of multiple drugs for post-surgical chemotherapy against solid tumor.     

Layer-by-layer assembly of poly(l-glutamic acid)/chitosan microcapsules for high loading and sustained release of 5-fluorouracil

Hollow polyelectrolyte microcapsules based on poly(l-glutamic acid) (PLGA) and chitosan (CS) with opposite charges were fabricated by layer-by-layer (LbL) assembly technique using melamine formaldehyde (MF) microparticles as sacrificial templates. The LbL assembly of polyelectrolytes and the resultant PLGA/CS microcapsules were characterized. A hydrophilic anticancer drug, 5-fluorouracil (5-FU), was chosen to investigate the loading and release properties of the microcapsules. The PLGA/CS microcapsules show high loading capacity of 5-FU under conditions of high drug concentration and salt adding. The high loading can be ascribed to spontaneous deposition of 5-FU induced by hydrogen bonding between 5-FU and PLGA/CS microcapsules. The PLGA/CS microcapsules show sustained release behavior. The release rate of 5-FU drastically slows down after loading in PLGA/CS microcapsules. The 5-FU release from PLGA/CS microcapsules can be best described using Ritger-Peppas or Baker-Londale models, indicating the diffusion mechanism of 5-FU release from the PLGA/CS microcapsules. In vitro cytotoxicity evaluation by the MTT assay shows good cell viability over the entire concentration range of PLGA/CS microcapsules. Therefore, the novel PLGA/CS microcapsules are expected to find application in drug delivery systems because of the properties of biodegradability, high loading, sustained release and cell compatibility.     

Development and characterization of hyaluronic acid decorated PLGA nanoparticles for delivery of 5-fluorouracil

The present investigation was aimed to develop and explore the prospective of engineered PLGA nanoparticles as vehicles for targeted delivery of 5-fluorouracil (5-FU). Nanoparticles of 5-FU-loaded hyaluronic acid-poly(ethylene glycol)-poly(lactide-co-glycolide) (HA-PEG-PLGA-FU) copolymer were prepared and characterized by FTIR, NMR, transmission electron microscopy, particle size analysis, DSC, and X-ray diffractometer measurement studies. The nanoparticulate formulation was evaluated for in vitro release, hemolytic toxicity, and hematological toxicity. Cytotoxicity studies were performed on Ehrlich ascites tumor (EAT) cell lines using MTT cell proliferation assay. Biodistribution studies of ^99mTc labeled formulation were conducted on EAT-bearing mice. The in vivo tumor inhibition study was also performed after i.v. administration of HA-PEG-PLGA-FU nanoparticles. The HA conjugated formulation was found to be less hemolytic but more cytotoxic as compared to free drug. The hematological data suggested that HA-PEG-PLGA-FU formulation was less immunogenic compared to plain drug. The tissue distribution studies displayed that HA-PEG-PLGA-FU were able to deliver a higher concentration of 5-FU in the tumor mass. In addition, the HA-PEG-PLGA-FU nanoparticles reduced tumor volume significantly in comparison with 5-FU. Thus, it was concluded that the conjugation of HA imparts targetability to the formulation, and enhanced permeation and retention effect ruled out its access to the non-tumor tissues, at the same time favored selective entry in tumors, thereby reducing the side-effects both in vitro and in vivo.     

Sustained release formulations of rhVEGF165 produce a durable response in a murine model of peripheral angiogenesis

Local delivery of therapeutic angiogenic agents that stimulate blood vessel formation represents a promising strategy for the treatment of peripheral vascular disease (PVD). At present, requirements for temporal and spatial parameters for localized delivery are unclear, with a variety of sustained delivery approaches being examined. Two polymer-based sustained formulations containing the 165 amino acid isoform of human recombinant vascular endothelial growth factor-A (rhVEGF₁₆₅) were evaluated for their potential application in the treatment of PVD following intramuscular injection. Microspheres prepared from a 50:50 ratio of polylactic-co-glycolic acid (PLGA) and a gel of PLGA polymer solubilized in N-methyl pyrrolidone (PLGA:NMP) were each loaded with rhVEGF₁₆₅ and tested in vitro and in vivo. PLGA microspheres averaged ∼30 μm in diameter and contained 8.9% (w/w) rhVEGF₁₆₅, while the PLGA:NMP gel was formulated with varying amounts of spray freeze-dried rhVEGF₁₆₅ to result in final gel formulations having concentrations of 0.36, 0.72, or 3.6 mg/mL rhVEGF₁₆₅. In vitro release of rhVEGF₁₆₅ from PLGA microspheres showed ∼10% cumulative release by day 6, whereas the cumulative release of rhVEGF₁₆₅ from the PLGA:NMP gel matrices (0.65% w/w loading) was less than 0.25% at this same time point. While the in vitro release characteristics of these two sustained release formulations were broadly different, the plasma rhVEGF₁₆₅ concentration-time profiles following hind-limb intramuscular (IM) injection of these formulations in non-compromised rats revealed similar in vivo pharmacokinetics. Three-dimensional resin casts of vascular architecture were prepared at days 3, 7, 14, 21, 28, 60, and 75 following a single IM dosing of these sustained release microsphere and gel matrix formulations in the gastrocnemius muscle of immune-compromised mice. Scanning electron microscopic visualization of these vascular casts demonstrated spatial arrangement of capillary sprouts and vessel enlargement consistent with profound vascular changes occurring within 3 days of dosing that persisted for 2 months, approximately 1 month beyond the anticipated completion of rhVEGF₁₆₅ release from these sustained delivery formulations. Vascular re-modeling events were correlated with histological and immunohistochemical parameters attributed to known biological actions of rhVEGF₁₆₅ signaling. Together, these pharmacokinetic and pharmacodynamic results support the use of sustained release PLGA-based formulations for the local delivery of rhVEGF₁₆₅ to achieve a durable vascular re-modeling response.     

Preparation of micro-fabricated biodegradable polymeric structures using NCDS

PLGA scaffolds were prepared using a nano-composite deposition system (NCDS). 5-Fluorouracil (5-FU) was used as a model drug. Hydroxyapatite (HA) was included in the scaffolds to improve the mechanical properties of the scaffolds and modulate the release of 5-FU from the scaffolds. 5-FU and HA were dispersed well in the prepared scaffolds when evaluated with SEM, FT-IR, XRPD and DSC. The release of 5-FU from the prepared scaffolds consisting of different compositions was determined using 40 mL PBS as the medium. The release profiles of 5-FU from PLGA scaffolds followed the typical triphasic release pattern. The addition of HA to the compositions increased the release rate of 5-FU from the scaffolds and improved the mechanical properties of the scaffolds, while it retarded the degradation of PLGA. Therefore, NCDS could be a good system to prepare polymeric implants of various shapes with different drug release patterns.     

Improvement of survival in C6 rat glioma model by a sustained drug release from localized PLGA microspheres in a thermoreversible hydrogel

A local drug delivery system based on sustained drug release is an attractive approach to treat brain tumors. We have developed a novel device using drug-incorporated poly(lactic-co-glycolic acid) (PLGA) microspheres embedded in thermoreversible gelation polymer (TGP) formulation (drug/PLGA/TGP formulation). TGP forms a gel at body temperature but sol at room temperature. Therefore, when this formulation is injected into the brain tumor, the PLGA microspheres in TGP gel are localized at the injection site and do not diffuse throughout the brain tissue; eventually, sustained drug release from PLGA microspheres is achieved at the target site. In this study, two chemotherapeutic drugs (camptothecin (CPT) or vincristine (VCR)) were incorporated into PLGA microspheres to prepare drug/PLGA/TGP formulations. VCR/PLGA microspheres exhibited the higher encapsulation efficiency than CPT/PLGA microspheres (70.1% versus 30.1%). In addition, VCR/PLGA microspheres showed a higher sustained release profile than CPT/PLGA microspheres (54.5% versus 72.5% release, at 28 days). Therapeutic effect (mean survival) was evaluated in the C6 rat glioma model (control group, 18 days; CPT/PLGA/TGP treatment group, 24 days; VCR/PLGA/TGP treatment group, 33 days). In particular, the VCR/PLGA/TGP formulation produced long-term survivors (>60 days). Therefore, this formulation can be therapeutically effective formulation for the glioma therapy.     

The use of chitosan-coated flexible liposomes as a remarkable carrier to enhance the antitumor efficacy of 5-fluorouracil against colorectal cancer

Surface-coated nanocarriers have been extensively used to enhance the delivery of anticancer drugs and improve their therapeutic index. In this study, chitosan (CS)-coated flexible liposomes (chitosomes) containing 5-fluorouracil (5-FU) were designed and characterized for use as a novel approach to target colon cancer cells. 5-FU-loaded flexible liposomes (F1, F2, and F3) and 5-FU-loaded chitosomes (F4, F5, and F6) were prepared using film hydration and electrostatic deposition techniques, respectively. The particle size, polydispersity index (PDI), zeta potential, entrapment efficiency (EE%), morphology, and in vitro drug release ability, and cytotoxicity of the formulations were determined. The results revealed that the size of chitosomes ranged from 212 to 271 nm with a positive surface charge of 6.1 to 14.7 mV, whereas the particle size of liposomes ranged from 108 to 234 nm with negative surface charges of ?2.3 to ?16.3. F3 and F6 had a spherical shape with a rough surface structure. The in vitro drug release study revealed that chitosomes retard 5-FU release as opposed to the 5-FU solution and liposomes. The cytotoxicity study using a colon cancer cell line (HT-29) showed that 5-FU-loaded chitosomes were more effective in killing cancer cells in a sustained manner than liposomes and the 5-FU solution. Chitosomes were therefore successfully developed as nanocarriers of 5-FU, with potential cytotoxicity for colorectal cancer cells.     

Formulation and investigation of 5-FU nanoparticles with factorial design-based studies

This study describes an orthogonal experimental design to optimize the formulation of 5-fluorouracil (5-FU) loaded poly D,L (lactide-co-glycolide) (PLGA) nanoparticles (5FU-NP) by a nanoprecipitation-solvent displacement technique. The type of surfactant, amount of acetone and molecular weight of the polymer with three levels of each factor were selected and arranged in an L18(3(5)) orthogonal experimental table. From the statistical analysis of the data polynominal equations were generated. Optimized formulations have the particle size ranging from 160 to 250 nm. Smallest nanoparticles (161+/-1.22 nm) were obtained using Resomer PLGA 755 and pluronic F-68 with 10 ml acetone amount. Under these conditions the 5-FU entrapment percentage was maximum 78.30%, suggesting 5-FU might be entrapped and adsorbed on the nanoparticle surface. In vitro release of three formulations with maximum drug entrapment efficiency and minimum particle size, were also investigated by release kinetics. According to the determined coefficients, release data fit to Higuchi's diffusion kinetics. The in vitro release of 5FU-NP in phosphate buffered saline (PBS, pH 7.4) is suggested to be controlled by a combination of diffusion with slow and gradual erosion of the particles. Also, the antimicrobial activity was observed even on the end of seventh day with all formulations.     

影响聚酯微球中药物释放的因素

聚酯材料因其原料易得、容易加工、生物相容性好、具有可生物降解性等优点,已经成为当今药物载体材料中的一大研究热点。现综合国内外的有关报道对可生物降解聚酯材料作为药物载体制备微球制剂的研究进展进行了综述。针对目前限制聚酯材料微球制剂临床应用存在的问题,从聚合物、药物、制备工艺、附加剂、辐射灭菌5个方面对影响聚乳酸(PLA)和聚乳酸乙醇酸共聚物(PLGA)缓释微球中药物释放的因素进行了重点介绍,为研究聚酯微球中药物的释放提供思路。     

Nanoporous multilayer poly(L-glutamic acid)/chitosan microcapsules for drug delivery

Nanoporous poly(L-glutamic acid)/chitosan (PLGA/CS) multilayer microcapsules were fabricated by layer-by-layer (LbL) assembly using the porous silica particles as sacrificial templates. The LbL assembled nanoporous PLGA/CS microcapsules were characterized by Zeta-potential analyzer, FTIR, TGA, SEM, TEM and CLSM. 5-Fluorouracil (5-FU) was chosen as model drug. The drug loading content of PLGA/CS microcapsules depends on loading time, loading temperature, pH value and NaCl concentration. High loading capacity of microcapsules can be achieved by simply adjusting pH value and salt concentration. Moreover, 5-Fu loaded microcapsules take on a sustained release behavior, especially in an acid solution, in contrast to burst release of bare 5-Fu. The kinetics of 5-Fu release from PLGA/CS microcapsules conforms to Korsmeyer-Peppas and Baker-Lonsdale models, the mechanism of which can be ascribed to priority of drug diffusion and subordination of polymer degradation. The MTT cytotoxicity assay in vitro reveals the satisfactory anticancer activity of the drug-loaded PLGA/CS microcapsules. Therefore, the novel nanoporous PLGA/CS microcapsules is expected to find application in drug delivery systems.     

Targeted delivery of 5-fluorouracil to HT-29 cells using high efficient folic acid-conjugated nanoparticles

Abstract

The incorporation of a high percentage of targeting molecules into drug delivery system is one of the important methods for improving efficacy of targeting therapeutic drugs to cancer cells. PLGA-based drug delivery carriers with folic acid (FA) as targeting molecule have a low targeting efficiency due to a low FA conjugation ratio. In this work, we fabricated a FA-conjugated PLGA system using a crosslinker 1, 3-diaminopropane and have achieved a high conjugation ratio of 46.7% (mol/mol). The as-prepared PLGA-based biomaterial was used to encapsulate therapeutic drug 5-fluorouracil (5-FU) into nanoparticles. In the in vitro experiments, an IC₅₀ of 5.69?µg/mL has been achieved for 5-FU loaded PLGA-1, 3-diaminopropane-folic acid nanoparticles on HT-29 cancer cells and is significantly lower than that of 5-FU and 5-FU loaded PLGA nanoparticles which only have an IC₅₀ of 22.9 and 14.17?µg/mL, respectively. The fluorescent microscopy images showed that nanoparticles with FA are largely taken up by HT-29 cancer cells and the targeting nanoparticles have more affinity to cancer cells than the pure drugs and untreated nanoparticles. Therefore, the 1, 3-diaminopropane can facilitate the conjugation of FA to PLGA to form a novel polymer and 5-FU loaded PLGA-1, 3-diaminopropane-folic acid nanoparticles can be a highly efficient system for specific delivery of drugs to cancer cells.     

Beyond Q1/Q2: The Impact of Manufacturing Conditions and Test Methods on Drug Release From PLGA-Based Microparticle Depot Formulations

Drug-loaded polymeric microparticles have been used as long-acting injectable (LAI) depot formulations. To obtain U.S. Food and Drug Administration approval, a generic LAI depot product needs to be qualitatively (Q1) and quantitatively (Q2) the same in terms of inactive ingredients as its reference-listed drug. However, Q1/Q2 sameness as the reference-listed drug does not guarantee the same in vitro drug release profile and in vivo performance, especially when the manufacturing methods are different. There is little consensus on how the in vitro testing needs to be done to examine the release profiles of LAI depot formulations. This study examined the manufacturing differences in making risperidone-loaded poly(lactide-co-glycolide) microparticles and their impact on the release kinetics. It also examined the impacts of in vitro testing methods on the drug release profiles. Two in-house manufactured risperidone poly(lactide-co-glycolide) microparticles and Risperdal Consta^® were used in the study. Of the in vitro release methods tested, the orbital agitation method provided the most reproducible release profiles. The results indicate that the in vitro release kinetics depend not only on manufacturing procedures but also on the in vitro testing conditions, such as the agitation speed, vessel-dimensions, solid beads, media exchange volume, and other parameters both under real-time and accelerated testing conditions. In the current case, the in vitro experimental condition seemed to affect the drug release kinetics more than the manufacturing differences. The developed orbital agitation release testing method is simple, robust, and reproducible, which allows the comparison of in vitro release profiles of formulations that are prepared with manufacturing differences.     

Sustained Polymeric Delivery of Gene Silencing Antisense ODNs,siRNA, DNAzymes and Ribozymes: In Vitro and In Vivo Studies

Small interfering RNA (siRNA), antisense oligonucleotides (ODNs), ribozymes and DNAzymes have emerged as sequence-specific inhibitors of gene expression that may have therapeutic potential in the treatment of a wide range of diseases. Due to their rapid degradation in vivo, the efficacy of naked gene silencing nucleic acids is relatively short lived. The entrapment of these nucleic acids within biodegradable sustained-release delivery systems may improve their stability and reduce the doses required for efficacy. In this study, we have evaluated the potential in vitro and in vivo use of biodegradable poly (_d,_l-lactide-co-glycolide) copolymer (PLGA) microspheres as sustained delivery devices for ODNs, ribozyme, siRNA and DNA enzymes. In addition, we investigated the release of ODN conjugates bearing 5′-end lipophilic groups. The in vitro sustained release profiles of microsphere-entrapped nucleic acids were dependent on variables such as the type of nucleic acid used, the nature of the lipophilic group, and whether the nucleic acid used was single or double stranded. For in vivo studies, whole body autoradiography was used to monitor the bio-distribution of either free tritium-labelled ODN or that entrapped within PLGA microspheres following subcutaneous administration in Balb-c mice. The majority of the radioactivity associated with free ODN was eliminated within 24 h whereas polymer-released ODN persisted in organs and at the site of administration even after seven days post-administration. Polymer microsphere released ODN exhibited a similar tissue and cellular tropism to the free ODN. Micro-autoradiography analyses of the liver and kidneys showed similar bio-distribution for polymer-released and free ODNs with the majority of radioactivity being concentrated in the proximal convoluted tubules of the kidney and in the Kupffer cells of the liver. These findings suggest that biodegradable PLGA microspheres offer a method for improving the in vivo sustained delivery of gene silencing nucleic acids, and hence are worthy of further investigation as delivery systems for these macromolecules.     

Local drug delivery using poly(lactic-co-glycolic acid) nanoparticles in thermosensitive gels for inner ear disease treatment

Intratympanic (IT) therapies have been explored to address several side effects that could be caused by systemic administration of steroids to treat inner ear diseases. For effective drug delivery to the inner ear, an IT delivery system was developed using poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) and thermosensitive gels to maintain sustained release. Dexamethasone (DEX) was used as a model drug. The size and zeta potential of PLGA NPs and the gelation time of the thermosensitive gel were measured. In vitro drug release was studied using a Franz diffusion cell. Cytotoxicity of the formulations was investigated using SK-MEL-31 cells. Inflammatory responses were evaluated by histological observation of spiral ganglion cells and stria vascularis in the mouse cochlea 24 h after IT administration. In addition, the biodistribution of the formulations in mouse ears was observed by fluorescence imaging using coumarin-6. DEX-NPs showed a particle size of 150.0 ± 3.2 nm in diameter and a zeta potential of −18.7 ± 0.6. The DEX-NP-gel showed a gelation time of approximately 64 s at 37 °C and presented a similar release profile and cytotoxicity as that for DEX-NP. Furthermore, no significant inflammatory response was observed after IT administration. Fluorescence imaging results suggested that DEX-NP-gel sustained release compared to the other formulations. In conclusion, the PLGA NP-loaded thermosensitive gel may be a potential drug delivery system for the inner ear.     

Preparation,Characterization, and In Vitro Evaluation of 1- and 4-Month Controlled Release Orntide PLA and PLGA Microspheres

Purpose. To prepare, characterize and evaluate in vitro sustained delivery formulations for a novel LHRH antagonist, Orntide acetate, using biodegradable microspheres (ms). Methods. Poly(d,l-lactide) (PLA) and poly(d,l-lactide-co-glycolide) (PLGA) were characterized for molecular weight (M_w, M_n) using gel permeation chromatography (GPC) and content of free end carboxyl groups (acid number, AN) by a titration method. 1- and 4-month Orntide ms were prepared by a dispersion / solvent extraction / evaporation process and characterized for drug content (HPLC), bulk density (tapping method), particle size (laser diffraction method), surface morphology (scanning electron microscopy, SEM), and structural integrity of encapsulated peptide by Fourier Transform Matrix Assisted Laser Desorption mass spectrometry (FT-MALDI). Peptide binding to PLA and PLGA and non-specific adsorption to blank ms was studied in 0.1 M phosphate buffer pH 7.4 (PB) and 0.1 M acetate buffer pH 4.0 (AB). In vitro release of peptide was assessed in PB and AB. Results. M_w for the PLGA copolymers varied from 10,777 to 31,281 Da and was 9,489 Da for PLA. AN was between 4.60 and 15.1 for the hydrophilic resomers and 0.72 for the hydrophobic 50:50 PLGA copolymer. Spherical ms (3.9 μ to 14 μ in diameter) with mostly non-porous surface and varying degree of internal porosity were prepared. FT-MALDI mass spectra of the extracted peptide showed that the encapsulation process did not alter its chemical structure. Peptide binding to PLGA and PLA and non-specific adsorption to blank PLGA ms were dependent upon pH and were markedly higher in PB than in AB. The initial in vitro release in PB varied from 0.5 to 26%/24 h but due to substantial binding of the peptide to the polymeric matrix the long-term release in PB could not be determined. Application of a dialysis method allowed for a more accurate determination of in vitro release and a good total drug recovery. Conclusions. Orntide acetate was successfully incorporated into PLA and PLGA ms and the 1- and 4-month in vitro release profiles were achieved by polymer selection and optimization of the manufacturing parameters.     

Ondansetron-loaded biodegradable microspheres as a nasal sustained delivery system: In vitro/in vivo studies

The aim of this study was to prepare ondansetron-loaded biodegradable microspheres as a nasal delivery system. Microspheres were prepared with emulsification/spray-drying technique using poly(d,l-lactide) (PLA) and two different types of poly(d,l-lactide-co-glycolide) (PLGA). The effect of the type of organic solvent (dichloromethane (DCM) or a mixture of DCM and ethyl acetate) on the microsphere characteristics was also examined. The prepared microspheres were evaluated with respect to the morphological properties, particle size, zeta potential, drug loading efficiency, and in vitro drug release. The mean particle size (d₅₀) of microsphere formulations was ranged from 11.67–25.54 μm, indicating suitable particle size for nasal administration. All microspheres had low drug loading efficiency in the range of 12.28–21.04%. The results indicated that particle size of microspheres were affected by both type of polymer and organic solvent, however drug loading efficiency of microspheres were affected by only the type of organic solvent used. All microspheres were negatively charged due to the polymers (PLA or PLGA) used. A prolonged in vitro drug release profile was observed for 96?h. Based on in vitro data, the selected microsphere formulation has been applied via nasal route to rats in vivo. Following nasal administration of ondansetron-loaded microsphere to rats, ondansetron plasma levels were within a range of 30–48?ng/mL during 96?h, indicating a sustained drug delivery pattern and relatively a constant plasma drug concentration level. The results suggested that biodegradable microspheres prepared with emulsification/spray-drying technique could be considered to deliver ondansetron via nasal route to obtain a prolonged release.     

Influence of 5-Fluorouracil-Loaded Microsphere Formulation on Efficient Rat Glioma Radiosensitization

PURPOSE: To determine (i) the efficiency of radiosensitizing 5-FU-loaded microspheres and (ii) the impact of microparticle formulation on response to treatment. METHODS: C6 tumor-bearing rats were stereotactically implanted with microspheres and/or allocated to: control groups (untreated) or treatment (only radiotherapy; fast-release 5-FU microspheres + radiotherapy; slow-release 5-FU microspheres + radiotherapy). The next day, fractionated radiotherapy, limited to the hemibrain, was initiated in all treated animals. The irradiation cycle included 36 Gy, given in 9 sessions for 3 consecutive weeks. Tumor development was assessed by T2-weighted MRI. RESULTS: 5-FU microspheres associated with radiotherapy caused a 47% complete remission rate (9/19) as opposed to the 8% rate (1/12) when radiotherapy alone or 0% in control animals. Drug delivery for 3 weeks produced better survival results (57%) compared to one-week sustained release (41%). MR images showed exponentially increasing tumor volumes during the first half of the radiotherapy cycle, followed by a decrease, and the disappearance of the tumor if survival exceeded 120 days. CONCLUSIONS: 5-FU controlled delivery is a promising strategy for radiosensitizing gliomas. Drug delivery system formulation is unambiguously implicated in both the response to treatment and the limitation of toxic side effects.     

Structure of 3-Acetyl-5-fluorouracil (5-FU): Implication for Its Rearrangements During Hydrolysis and upon Heating

Single-crystal X-ray diffraction data show that the 3-acetyl group in l,3-diacetyl-5-FU (FU = fluorouracil) is perpendicular to the plane of the 5-FU ring, while the 1-acetyl group is coplanar with the ring. Analyses of ¹H NMR and IR spectra provide evidence that the 1-and 3-acyl groups are in different electronic environments, which is consistent with the X-ray diffraction structure. 3-Acetyl-5-FU is thermally unstable, giving mainly l-acetyl-5-FU (80%) and 5-FU (20%) upon heating. The hydrolysis of 3-acyl derivatives of 5-FU showed a biexponential relationship between In concentration and time which had not been previously observed. The behavior of 3-acetyl-5-FU during hydrolysis can be explained by postulating its initial rapid equilibrium with an intermediate, 2-acetyl-5-FU, which subsequently hydrolyzes to 5-FU or rearranges to l-acetyl-5-FU, which hydrolyzes to 5-FU. The 2-acetyl intermediate was trapped by its reaction with formaldehyde. The formaldehyde adducts of the symmetrical 2-acetyl intermediate rearranged to yield equal amounts of 1- and 3-acetyloxymethyl-5-FU.