In vitro and in vivo evaluation of cubosomes containing 5-fluorouracil for liver targeting

The objective of this study was to prepare cubosomal nanoparticles containing a hydrophilic anticancer drug 5-fluorouracil (5-FU) for liver targeting. Cubosomal dispersions were prepared by disrupting a cubic gel phase of monoolein and water in the presence of Poloxamer 407 as a stabilizer. Cubosomes loaded with 5-FU were characterized in vitro and in vivo. In vitro, 5-FU-loaded cubosomes entrapped 31.21% drug and revealed nanometer-sized particles with a narrow particle size distribution. In vitro 5-FU release from cubosomes exhibited a phase of rapid release of about half of the entrapped drug during the first hour, followed by a relatively slower drug release as compared to 5-FU solution. In vivo biodistribution experiments indicated that the cubosomal formulation significantly (P<0.05) increased 5-FU liver concentration, a value approximately 5-fold greater than that observed with a 5-FU solution. However, serum serological results and histopathological findings revealed greater hepatocellular damage in rats treated with cubosomal formulation. These results demonstrate the successful development of cubosomal nanoparticles containing 5-FU for liver targeting. However, further studies are required to evaluate hepatotoxicity and in vivo antitumor activity of lower doses of 5-FU cubosomal formulation in treatment of liver cancer.Key words: 5-Fluorouracil, Hydrophilic drug, Cubosomes, Liver targeting, Hepatotoxicity     

Zero-order release of 5-fluorouracil from PCL-based films featuring trilayered structures for stent application

A trilayered Poly(ε-caprolactone) (PCL)-based film with a coating layer (CL), a drug-storing layer (DSL) loaded with antitumor drug 5-Fluorouracil (5-FU) and a backing layer (BL) are presented for film-based stent application in malignant stricture or stenosis. V-C diffusion cells were used to investigate the drug permeability of the CL, while scanning electron microscopy (SEM) was employed for observing the microscopic architectures and morphologies. Drug release from the trilayered films exhibited a zero-order pattern, and the release process followed an ‘outer-to-inner’ pattern. The formation mechanism and influencing factors of the zero-order drug release pattern were in-depth elucidated, and factors affecting the drug release were also investigated. The reduction of initial drug loading in DSL slowed the drug release and diminished the zero-order release pattern. Drug permeability of the CL depended significantly on CL thickness, but not significantly on PCL molecular weight. Besides, the addition of PEG porogen in the CL accelerated the drug release by elevation of the drug permeability of CL, and the action mechanism of PEG was revealed by the PEG release test and SEM. The loading of 5-FU in the CL could lead to a two-phased release profile. This study revealed the potential of the trilayered film in controlled drug delivery to intraluminal tumor due to its highly tunable zero-order drug release.     

Stent conditioned media for in vitro evaluation of hydrophobic stent coatings

In vitro cell studies of hydrophobic drugs face difficulties associated with their low aqueous solubility. To study poorly soluble drugs in bio-relevant media, solubilizing agents are frequently used to make stock solutions before final reconstitution in media. This results in drug concentrations that are not representative of in vivo conditions and may pose adverse effects on cells' biological functions. This is especially true of typical hydrophobic stent coatings intended for vascular applications, where poor in vitro to in vivo correlation exists. To this end, a method for preparation of hydrophobic drug suspensions in bio-relevant media via stent conditioned media using paclitaxel (PTX) as a model drug is proposed. Since the drug is present as a suspension, this media was validated for its content uniformity and potency to induce formation of micronuclei, typical of cells undergoing prolonged mitotic arrest. Further, PTX uptake by endothelial cells was quantified and showed that the PTX stent conditioned media (at a theoretical concentration of 100 μM) suppressed cellular growth equivalent to the 0.1 μM DMSO dissolved PTX.     

Poly(δ-valerolactone-co-allyl-δ-valerolactone) cross-linked microparticles: Formulation,characterization and biocompatibility

A novel polymeric material, poly(δ-valerolactone-co-allyl-δ-valerolactone) (PVL-co-PAVL), was used to manufacture microparticles (MPs) for sustained drug delivery. PVL-co-PAVL MPs were formulated using a modified oil-in-water approach, followed by a UV-initiated cross-linking process. Prepared MPs had a smooth spherical morphology and cross-linking of the copolymer was found to improve the integrity and thermal stability of the MPs. Paclitaxel (PTX) was successfully loaded into the MPs at a high drug loading capacity, using a post-loading swelling-equilibrium method. In vitro evaluation showed that the PVL-co-PAVL MPs provide sustained release of PTX, which exhibited first-order release kinetics. A subsequent pilot pharmacokinetic study was carried out on the PTX-loaded PVL-co-PAVL MPs. During this study, serum levels of PTX were monitored following subcutaneous administration of the MPs to Sprague-Dawley rats. Overall, the in vivo release of PTX from the MPs was lower than expected based on the in vitro release studies. Detectable serum levels of PTX suggest that sustained release of drug was achieved in vivo. Minimal changes in subcutaneous tissue were observed at the site of injection. Future studies will further examine the localized and systemic distribution of drug following administration in this new polymer-based MP system.     

Dissolution from solid lipid extrudates containing release modifiers

Biodegradable film-based stents emerged as a promising medical platform for drug delivery to resolve stenosis encountered in physiological conduits (e.g. blood vessels, biliary and urethral tracts). Drug release kinetics significantly affects the pharmacological effects of a stent, thus it is desirable for a stent to possess highly adjustable drug release kinetics. In this study, a series of amphiphilic poly(?-caprolactone)-poly(ethylene glycol)-poly(?-caprolactone) (PCL-PEG-PCL) copolymers were used as additives to adjust 5-fluorouracil (5-FU) release from PCL films. The effects of the copolymer addition on drug release behavior, drug permeability, crystalline states, and surface and internal morphologies of the films were investigated. It was found that, the addition of PCL-PEG-PCL could accelerate 5-FU release. The release rate of 5-FU increased with increasing content of PCL-PEG-PCL in the film, but it decreased with the ratio of PCL blocks in the PCL-PEG-PCL copolymer. The diffusion test results showed that 5-FU diffused through the film containing PCL-PEG-PCL faster than it permeated through the pure PCL film, indicating that the addition of PCL-PEG-PCL can improve the permeability of 5-FU in PCL film. The addition of PCL-PEG-PCL copolymer showed high drug-release-regulating ability in the 5-FU-loaded PCL films.     

In vitro cytotoxicity,in vivo biodistribution and antitumor activity of HPMA copolymer–5-fluorouracil conjugates

5-Fluorouracil (5-FU) is an antimetabolite with a broad-spectrum activity against solid tumors. However, its very short half-life in plasma circulation greatly limited the in vivo antitumor efficacy and clinical application. The current work aimed to solve this problem as well as to increase 5-FU biodistribution to tumor by covalently conjugating 5-FU to a biocompatible, non-toxic and non-immunogenic drug carrier – N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer. The in vitro cytotoxicity, in vivo biodistribution and therapeutic efficacy of HPMA copolymer–5-FU conjugates (P-FU) were reported. Cytotoxicity was evaluated by using a serial of tumor cells (A549, CT-26, Hela, HepG₂ cells and 5-FU resistant HepG₂ cells). In vivo biodistribution and therapeutic efficacy were investigated in Kunming mice-bearing hepatoma 22 (H₂₂). Results indicated that P-FU could increase the cytotoxicity of 5-FU in Hela, HepG₂ and 5-FU resistant HepG₂ cells, while it decreases the cytotoxicity of 5-FU in A549 and CT-26. Both in vitro release profile in plasma and biodistribution study showed that P-FU significantly prolonged the drug plasma circulation time. P-FU also showed an over 3-fold larger area under the concentration–time curve (AUC) in tumor when compared with free drug. Therapeutic evaluation also demonstrated that the treatment with P-FU displayed stronger inhibition of the tumor growth when compared with that of control group (physiologic saline) or 5-FU group at the same dose. All the results suggested that P-FU could increase cytotoxicity of 5-FU in certain cancer cell lines, prolong 5-FU circulation time in vivo, enhance 5-FU distribution to tumor and improve therapeutic efficacy. Therefore, HPMA copolymer is a potential carrier for 5-FU for the effective treatment of cancer.     

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.     

Long-circulating self-assembled cholesteryl albumin nanoparticles enhance tumor accumulation of hydrophobic anticancer drug

The objective of this study was to develop an albumin nanoparticle with improved stability and drug loading capacity. Generation of nanomaterials having physiologically stable and high potential for drug delivery is still challenging. Herein we synthesized cholesteryl albumin conjugate using N,N-disuccinimidyl carbonate coupling reagent and prepared paclitaxel-loaded cholesteryl albumin nanoparticle (PTX-Chol-BSA) by self-assembly with the mean hydrodynamic diameter of 147.6 ± 1.6 nm and with high loading capacity. PTX-Chol-BSA nanoparticle showed much higher colloidal stability than a simple complex of PTX and BSA (PTX–BSA) and sustained release profile. PTX-Chol-BSA nanoparticles exhibited greater cellular uptake and cytotoxicity in B16F10 and MCF-7 cancer cell lines, as compared with PTX in Cremophor EL/ethanol (PTX-Cre/EtOH) and PTX–BSA formulations. A pharmacokinetic study in tumor-bearing mice showed that the area under the concentration–time curve (AUC_{0–8 h}) following the administration of PTX-Chol-BSA was 1.6–2-fold higher than those following the administration of PTX-Cre/EtOH and PTX–BSA. In addition, the tumor AUC_{0–8 h} of PTX-Chol-BSA was around 2-fold higher than that of PTX–BSA. Furthermore, in vivo antitumor efficacy results revealed that PTX-Chol-BSA nanoparticles have greater antitumor efficacy. In conclusion, we demonstrated the potential of PTX-Chol-BSA nanoparticles for anti-tumor chemotherapy, with enhanced in vitro and in vivo behaviors, as compared to PTX–BSA and PTX-Cre/EtOH.     

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.     

Oral transmucosal delivery of domperidone from immediate release films produced via hot-melt extrusion technology

The objective of the study was to prepare and characterize the domperidone (DOM) hot-melt extruded (HME) buccal films by both in vitro and in vivo techniques. The HME film formulations contained PEO N10 and/or its combination with HPMC E5 LV or Eudragit RL100 as polymeric carriers, and PEG3350 as a plasticizer. The blends were co-processed at a screw speed of 50 rpm with the barrel temperatures ranging from 120–160°C utilizing a bench top co-rotating twin-screw hot-melt extruder using a transverse-slit die. The HME films were evaluated for drug content, drug excipient interaction, in vitro drug release, mechanical properties, in vivo residence time, in vitro bioadhesion, swelling and erosion, ex vivo permeation from HME films and the selected optimal formulation was subjected for bioavailability studies in healthy human volunteers. The extruded films demonstrated no drug excipient interaction and excellent content uniformity. The selected HME film formulation (DOM2) exhibited a tensile strength (0.72 Kg/mm²), elongation at break (28.4% mm²), in vivo residence time (120 min), peak detachment force (1.55 N), work of adhesion (1.49 mJ), swelling index (210.2%), erosion (10.5%) and in vitro drug release of 84.8% in 2 h. Bioavailability from the optimized HME buccal films was 1.5 times higher than the oral dosage form and the results showed statistically significant (p < 0.05) difference. The ex vivo–in vivo correlation was found to have biphasic pattern and followed type A correlation. The results indicate that HME is a viable technique for the preparation of DOM buccal-adhesive films with improved bioavailability characteristics.     

Pharmacokinetics and biodistribution of paclitaxel-loaded pluronic P105 polymeric micelles

A novel polymeric micelle formulation of paclitaxel (PTX) has been prepared with the purpose of improving in vitro release as well as prolonging the blood circulation time of PTX in comparison to a current PTX formulation, Taxol injection. This work was designed to investigate the preparation, in vitro release, in vivo pharmacokinetics and tissue distribution of PTX-loaded Pluronic P105 micellar system. The micelles were prepared by thin-film method using a nonionic surfactant Pluronic P105 and a hydrophobic anticancer drug, PTX. With a dynamic light scattering sizer and a transmission electron microscopy, it was shown that the PTX-loaded micelles had a mean size of approximately 24 nm with narrow size distribution and a spherical shape. The in vitro release profiles indicated that the release of PTX from the micelles exhibited a sustained release behavior. A similar phenomenon was also observed in a pharmacokinetic study in rats, in which t _1/2β and AUC of the micelle formulation were 4.9 and 5.3-fold higher than that of Taxol injection. The biodistribution study in mice showed that the PTX-loaded micelles not only decreased drug uptake by liver, but also prolonged drug retention in blood and increased distribution of drug in lung, spleen and kidney. These results suggested that the P105 polymeric micelles may efficiently load, protect and retain PTX in both in vitro and in vivo environments, and could be a useful drug carrier for i.v. administration of PTX.     

Bioadhesive Films Containing Fluconazole for Mucocutaneous Candidiasis

Fluconazole is a broad spectrum antifungal agent that has been extensively applied for the management of oral, pharyngeal and cutaneous candidiasis. Fluconazole has a high volume of distribution (0.55–0.65 l/kg) and has systemic toxicity due to high drug-drug interaction. The present study focuses on the formulation of bioadhesive film as a controlled release carrier for fluconazole. The formulation was intended to provide localized delivery of fluconazole exclusively at the site of infection, thereby reducing its total dose and hence, dose-related toxicities. Bioadhesive films were prepared by solvent casting method using sodium alginate and polyvinyl alcohol alone as well as in various combinations. Prepared films were evaluated for physical characteristics like, weight and content uniformity, film thickness, swelling index, microenvironment pH and folding endurance. In vitro drug release, in vitro and ex vivo residence time, bioadhesive strength and skin irritation were also studied. Accelerated stability study was conducted on the optimized formulation as per ICH guidelines. Weight of all the films were not more than 20 mg. Thickness of the films ranged between 0.09 to 0.15 mm whereas swelling indices showed a high extent of variation. Films composed of polyvinyl alcohol alone provided a swelling index of 6%. Bioadhesive strength was found to be more than 18 g. Microenvironment pH was near to 7.0 for most of the formulations. Ex vivo residence time of optimized batch was more than 5 h and it provided controlled drug release up to 8 h. As revealed in FT-IR and DSC studies, drug was found to be compatible with the excipients used in this study.     

Controllable release of pirfenidone by polyvinyl alcohol film embedded soft contact lenses in vitro and in vivo

To increase the amount of pirfenidone (PFD) loaded in polyvinyl alcohol (PVA) film embedded soft contact lens (SCL), and evaluate its function of sustaining delivery of drug in vitro and in vivo. Drug loading efficiency within PVA film and SCLs, drug release from SCLs in vitro, and the effects of parameters of SCLs and external environment on drug release in vitro were evaluated by ultraviolet–visible spectrophotometer at 312 nm. Safety of SCLs was evaluated in vitro by transformed human corneal epithelial cell. Safety in vivo was determined by optical coherence tomography and histology of anterior segment of rabbits. Drug release study in tear fluid and aqueous humor were measured by ultra-performance liquid chromatography. SCLs had smooth surface and were fit for experimental rabbits. Amount of PFD in PVA film and SCLs were 153.515 μg ± 12.508 and 127.438 μg ± 19.674, respectively, PFD in PVA film was significantly higher than SCLs (p=.006) and closed to 150 μg (targeting amount of PFD to be loaded). Thickness of SCLs, molecular weight of PVA, and amount of PVA used in SCLs affected drug release in vitro significantly. Thickness of PVA film and amount of drug in SCLs had no effect on drug release rate in vitro. SCLs were safe in vitro and in vivo, PFD released from SCLs could be detected around 12 hours in tears and aqueous humor, and the concentration of drug was higher than eye drop at all detected time points while amount of PFD in SCLs was lower than eye drop. Drug loaded PVA film embedded SCLs may be a promising ocular drug delivery system.     

Synthesis,characterization and brain targeting potential of paclitaxel loaded thiamine-PPI nanoconjugates

Brain tumor is insidious complication which is difficult to treat because of the poor uptake of many potentially useful antitumor drugs through the blood-brain barrier (BBB). Present study was aimed for developing and exploring the use of thiamine conjugated poly(propylene imine) (PPI) dendrimers for increased delivery of paclitaxel (PTX) across the BBB. PTX loaded thiamine conjugated PPI dendrimers (PTX-Tm-PPI) shown increased drug loading and reduced hemolytic toxicity with suitability for prolonged delivery of PTX during in vitro release. Ex vivo cytotoxicity studies of free PTX, PTX-PPI and PTX-Tm-PPI dendrimers over IMR-32 human neuroblastoma cell line revealed higher potential of PTX-Tm-PPI nanoconjugate to retard tumor cell viability as compared to plain PTX or PTX-PPI. In vivo pharmacokinetics studies revealed significant (p < 0.05) slow clearance of PTX from the body via Tm-PPI nanoconjugate. Biodistribution studies confirmed about the targeting efficiency and higher biodistribution of Tm-PPI conjugates into the brain. The results concluded that the developed nanoconjugate has potential to deliver significantly higher amount of drug to brain tumor for improved therapeutic outcome.     

Thermosensitive Micelles–Hydrogel Hybrid System Based on Poloxamer 407 for Localized Delivery of Paclitaxel

A thermosensitive micelles–hydrogel hybrid system based on Poloxamer 407 (P407) was prepared to resolve the fast erosion and low loading capability of lipophilic drug of P407 gels for local chemotherapy. Different amounts of glutaraldehyde (GA) were applied to generate cross-linked networks with carboxymethyl chitosan (CMCS) interpenetrated in P407 gels, in which paclitaxel (PTX)-loaded N-octyl-O-sulfate chitosan micelles (PTX-M) were dispersed uniformly. The in vitro characteristics of CMCS-modified P407 gels (PTX-M-MG) were performed by examining the viscosity, swelling ratio, mechanical property, and drug release, while the in vivo evaluation included tissue distribution and anticancer efficacy through in-tratumoral administration in hepatoma solidity cell (Heps) tumor-bearing mice. The results showed that PTX-M-MG containing 0.05% (w/v) GA possessed lower viscosity, higher swelling ratio, stronger mechanical property, and longer term drug release, in which the loading efficiency of PTX was enlarged by the introduction of PTX-M. Moreover, PTX-M-MG revealed a prolonged retention at tumor sites, lasting for 20 days, and a superior tumor inhibition rate (64.27%) with reduced toxicity compared with Taxol®, PTX-M, and PTX-M loaded unmodified P407 gels (PTX-M-P407). It can be concluded that PTX-M-MG is a promising local delivery system for hydrophobic drug in cancer therapy, providing both improved efficacy and relieved side effects. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:2707–2717, 2013     

Lipid-albumin nanoassemblies co-loaded with borneol and paclitaxel for intracellular drug delivery to C6 glioma cells with P-gp inhibition and its tumor targeting

Successful chemotherapy with paclitaxel (PTX) is impeded by multidrug resistance (MDR) in tumor cells. In this study, lipid-albumin nanoassemblies co-loaded with borneol and paclitaxel (BOR/PTX LANs) were prepared to circumvent MDR in C6 glioma cells. The physiochemical properties including particle size, encapsulation efficiency and morphology were evaluated in vitro. Quantitative and qualitative investigations of cellular uptake were carried out in C6 glioma cells. The cytotoxicity of the BOR/PTX LANs was determined by MTT assay. After that, the tumor targeting was also evaluated in C6 glioma bearing mice by in vivo imaging analysis. BOR/PTX LANs have a higher entrapment efficiency (90.4 ± 1.2%), small particle size (107.5 ± 3.2 nm), narrow distribution (P.I. = 0.171 ± 0.02). The cellular uptake of PTX was significantly increased by BOR/PTX LANs compared with paclitaxel loaded lipid-albumin nanoassemblies (PTX LANs) in quantitative research. The result was further confirmed by confocal laser scanning microscopy qualitatively. The cellular uptake was energy-, time- and concentration-dependent, and clathrin- and endosome/lysosome-associated pathways were involved. The BOR/PTX LANs displayed a higher cytotoxicity agaist C6 glioma cells in comparion with PTX LANs and Taxol. Moreover, the encapsulation of BOR in LANs obviously increased the accumulation of the drug in tumor tissues, demonstrating the tumor targeted ability of BOR/PTX LANs. These results indicated that BOR/PTX LANs could overcome MDR by combination of drug delivery systems and P-gp inhibition, and shown the potential for treatment of gliomas.     

Co-delivery of paclitaxel (PTX) and docosahexaenoic acid (DHA) by targeting lipid nanoemulsions for cancer therapy

Breast cancer is one of the most common types of cancer in female patients with high morbidity and mortality. Multi-drug chemotherapy has significant advantages in the treatment of malignant tumors, especially in reducing drug toxicity, increasing drug sensitivity and reducing drug resistance. The objective of this research is to fabricate lipid nanoemulsions (LNs) for the co-delivery of PTX and docosahexaenoic acid (DHA) with folic acid (FA) decorating (PTX/DHA-FA-LNs), and investigate the anti-tumor activity of the PTX/DHA-FA-LNs against breast cancer both in vitro and in vivo. PTX/DHA-FA-LNs showed a steady release of PTX and DHA from the drug delivery system (DDS) without any burst effect. Furthermore, the PTX/DHA-FA-LNs exhibited a dose-dependent cytotoxicity and a higher rate of apoptosis as compared with the other groups in MCF-7 cells. The cellular uptake study revealed that this LNs were more readily uptaken by MCF-7 cells and M2 macrophages in vitro. Additionally, the targeted effect of PTX/DHA-FA-LNs was aided by FA receptor-mediated endocytosis, and its cytotoxicity was proportional to the cellular uptake efficiency. The anti-tumor efficiency results showed that PTX/DHA-FA-LNs significant inhibited tumor volume growth, prolonged survival time, and reduced toxicity when compared with the other groups. These results indicated that DHA increases the sensitivity of tumor cells and tumor-associated macrophages (ATM2) to PTX, and synergistic effects of folate modification in breast cancer treatment, thus PTX/DHA-FA-LNs may be a promising nanocarrier for breast cancer treatment.     

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.     

In vitro cytotoxicity, in vivo biodistribution and antitumor activity of HPMA copolymer–5-fluorouracil conjugates

5-Fluorouracil (5-FU) is an antimetabolite with a broad-spectrum activity against solid tumors. However, its very short half-life in plasma circulation greatly limited the in vivo antitumor efficacy and clinical application. The current work aimed to solve this problem as well as to increase 5-FU biodistribution to tumor by covalently conjugating 5-FU to a biocompatible, non-toxic and non-immunogenic drug carrier – N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer. The in vitro cytotoxicity, in vivo biodistribution and therapeutic efficacy of HPMA copolymer–5-FU conjugates (P-FU) were reported. Cytotoxicity was evaluated by using a serial of tumor cells (A549, CT-26, Hela, HepG₂ cells and 5-FU resistant HepG₂ cells). In vivo biodistribution and therapeutic efficacy were investigated in Kunming mice-bearing hepatoma 22 (H₂₂). Results indicated that P-FU could increase the cytotoxicity of 5-FU in Hela, HepG₂ and 5-FU resistant HepG₂ cells, while it decreases the cytotoxicity of 5-FU in A549 and CT-26. Both in vitro release profile in plasma and biodistribution study showed that P-FU significantly prolonged the drug plasma circulation time. P-FU also showed an over 3-fold larger area under the concentration–time curve (AUC) in tumor when compared with free drug. Therapeutic evaluation also demonstrated that the treatment with P-FU displayed stronger inhibition of the tumor growth when compared with that of control group (physiologic saline) or 5-FU group at the same dose. All the results suggested that P-FU could increase cytotoxicity of 5-FU in certain cancer cell lines, prolong 5-FU circulation time in vivo, enhance 5-FU distribution to tumor and improve therapeutic efficacy. Therefore, HPMA copolymer is a potential carrier for 5-FU for the effective treatment of cancer.