RESUMO
BACKGROUND: Topotecan (TPT) is a water-soluble derivate of camptothecin, which undergoes ring-opening hydrolysis in neutral solutions, leading to stability loss and poor cellular uptake. Lipid nanoencapsulation can improve TPT stability, and polymer-lipid hybrid nanoparticles (PLN) are interesting alternatives to improve TPT nanoencapsulation. OBJECTIVE: This study seeks to prepare complexes between the cationic TPT and the negatively charged dextran sulfate (DS) with a view of improving drug loading, chemical stability and release control. METHODS: The optimum ionic molar ratio in DS-TPT complexation was determined, and the selected complex was characterized by FTIR and solid-state 13C NMR. TPT solubility in the free and complexed forms was also assayed. TPT-PLN was then obtained via a microemulsion technique, and particle size, zeta potential, encapsulation efficiency, drug loading and drug recovery were determined. Additionally, the TPT stability and in vitro release were determined from PLN and compared with free TPT, TPT-DS complex and TPT encapsulated in nanostructured lipid carriers (NLC) of similar composition. RESULTS: TPT-DS complexation was confirmed by FTIR and NMR. TPT solubility in the complex was drastically decreased when compared to free TPT. TPT-PLN had high encapsulation efficiency (97%) and drug loading capacity (5.5%). Additionally, TPT-PLN showed a mean diameter, polidispersivity index e zeta potential of 140 nm, 0.2 and -22 mV, respectively. The TPT chemical stability and release from PLN were observed to be superior when compared to NLC. CONCLUSION: PLN has shown to be a more effective nanosystem for TPT nanoencapsulation because TPT loading, stability and release were superior when compared to TPT-NLC.
Assuntos
Sulfato de Dextrana/química , Portadores de Fármacos/química , Lipídeos/química , Nanopartículas/química , Topotecan/química , Liberação Controlada de Fármacos , Polímeros/química , Solubilidade , Inibidores da Topoisomerase I/químicaRESUMO
Treatment of retinoblastoma, the most common primary ocular malignancy in children, has greatly improved over the last decade. Still, new devices for chemotherapy are needed to achieve better tumor control. The aim of this project was to develop an ocular drug delivery system for topotecan (TPT) loaded in biocompatible hydrogels of poly(ε-caprolactone)-poly(ethyleneglycol)-poly(ε-caprolactone) block copolymers (PCL-PEG-PCL) for sustained TPT release in the vitreous humor. Hydrogels were prepared from TPT and synthesized PCL-PEG-PCL copolymers. Rheological properties and in vitro and in vivo TPT release were studied. Hydrogel cytotoxicity was evaluated in retinoblastoma cells as a surrogate for efficacy and TPT vitreous pharmacokinetics and systemic as well as ocular toxicity were evaluated in rabbits. The pseudoplastic behavior of the hydrogels makes them suitable for intraocular administration. In vitro release profiles showed a sustained release of TPT from PCL-PEG-PCL up to 7days and drug loading did not affect the release pattern. Blank hydrogels did not affect retinoblastoma cell viability but 0.4% (w/w) TPT-loaded hydrogel was highly cytotoxic for at least 7days. After intravitreal injection, TPT vitreous concentrations were sustained above the pharmacologically active concentration. One month after injection, animals with blank or TPT-loaded hydrogels showed no systemic toxicity or retinal impairment on fundus examination, electroretinographic, and histopathological assessments. These novel TPT-hydrogels can deliver sustained concentrations of active drug into the vitreous with excellent biocompatibility in vivo and pronounced cytotoxic activity in retinoblastoma cells and may become an additional strategy for intraocular retinoblastoma treatment.
Assuntos
Hidrogéis/química , Topotecan/administração & dosagem , Topotecan/química , Animais , Linhagem Celular Tumoral , Preparações de Ação Retardada , Sistemas de Liberação de Medicamentos/métodos , Humanos , Poliésteres/química , Polietilenoglicóis/química , Coelhos , Retina/metabolismo , Retinoblastoma/tratamento farmacológico , Topotecan/uso terapêuticoRESUMO
DNA topoisomerase I from Plasmodium falciparum (PfTopoI), a potential selective target for chemotherapy and drug development against malaria, is used here, together with human Topo I (HssTopoI), for docking, molecular dynamics (MD) studies and experimental assays. Six synthetic isoflavonoid derivatives and the known PfTopoI inhibitors camptothecin and topotecan were evaluated in parallel. Theoretical results suggest that these compounds dock in the binding site of camptothecin and topotecan inside both enzymes and that LQB223 binds selectively in PfTopoI. In vitro tests against P. falciparum blood parasites corroborated the theoretical findings. The selectivity index (SI) of LQB223 ≥ 98 suggests that this molecule is the most promising in the group of compounds tested. In vivo experiments in mice infected with P. berghei showed that LQB223 has an antimalarial activity similar to that of chloroquine.
Assuntos
Antimaláricos/farmacologia , DNA Topoisomerases Tipo I/metabolismo , Isoflavonas/farmacologia , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/enzimologia , Inibidores da Topoisomerase/farmacologia , Animais , Antimaláricos/química , Antimaláricos/uso terapêutico , Camptotecina/química , Camptotecina/farmacologia , Cristalografia por Raios X , Relação Dose-Resposta a Droga , Resistência a Medicamentos/efeitos dos fármacos , Feminino , Humanos , Concentração Inibidora 50 , Isoflavonas/química , Isoflavonas/uso terapêutico , Malária Falciparum/tratamento farmacológico , Malária Falciparum/parasitologia , Camundongos , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Parasitos/efeitos dos fármacos , Plasmodium berghei/efeitos dos fármacos , Termodinâmica , Inibidores da Topoisomerase/química , Topotecan/química , Topotecan/farmacologiaRESUMO
Topotecan is an important cytotoxic drug that has gained broad acceptance in clinical use for the treatment of refractory ovarian and small-cell lung cancer. The lactone active form of topotecan can be hydrolyzed in vivo, decreasing the drug's therapeutic efficacy. Lipid encapsulation may promote in vivo stabilization by removing topotecan from aqueous media. Earlier reports of topotecan lipid nanoencapsulation have focused on liposomal encapsulation; however, the higher stability and cost-effectiveness of solid lipid nanoparticles (SLN) highlight the potential of these nanoparticles as an advantageous carrier for topotecan. The initial motivation for this work was to develop, for the first time, solid lipid nanoparticles and nanostructured lipid carriers (NLC) with a high drug loading for topotecan. A microemulsion technique was employed to prepare SLNs and NLCs and produced homogeneous, small size, negatively charged lipid nanoparticles with high entrapment efficiency and satisfactory drug loading. However, low recovery of topotecan was observed when the microemulsion temperature was high and in order to obtain high quality nanoparticles, and precise control of the microemulsion temperature is critical. Nanoencapsulation sustained topotecan release and improved its chemical stability and cytotoxicity. Surprisingly, there were no significant differences between the NLCs and SLNs, and both are potential carriers for topotecan delivery.