Year: 2016
Type: dissertation
Abstract: Cancer is one of the major global causes of death.Generally, cancer treatment involves a combination of surgery, radiotherapy and chemotherapy.However, chemotherapy with conventional anticancer drugs has many drawbacks, one of them being the narrow therapeutic index.The systemic exposure to the drug may cause severe side-effects in healthy tissues, even though the drug concentrations remain low in the tumor tissue.Nanoparticulate drug delivery systems provide a tool to increase the drug concentrations in the target tissue and diminish the concentrations in heathy tissues.Despite the potential benefits in drug therapy, there are still many challenges to be overcome in drug targeting and development of nanoparticulate drug delivery systems.Clearly, further understanding of the kinetics of nanoparticulate systems at both the cellular and tissue levels is needed to aid in the more rational design of novel drug delivery systems.The aim of this study was to investigate the pharmacokinetic behavior of the anticancer drug, doxorubicin, and its passively and actively targeted formulations in cells in vitro, in tissues in vivo, and in human placenta ex vivo.An avidin fusion protein expression system was used for the active targeting of biotinylated doxorubicin formulations in vitro and in vivo.Concentrations of free and liposomal doxorubicin were measured by mass spectrometry in whole cells and nuclei (target organelle), and the cytotoxicity of the formulations was evaluated.The obtained data was used to create an in silico pharmacokinetic-pharmacodynamic (PK-PD) model depicting the nuclear concentration -effect relationships.Our studies revealed that free doxorubicin accumulated strongly in cells and their nuclei in a cell concentration dependent manner.The concentration of doxorubicin in nuclei was cell line dependent and did not necessarily correlate with the response, i.e. cytotoxicity.Free doxorubicin accumulated also in human placenta but only low levels of doxorubicin were measured in the fetal circulation ex vivo.Interestingly, the kinetics of doxorubicin delivered in pH-sensitive liposomes resembled that of the free drug in cells and in human placenta.Surface pegylation hindered the cellular uptake of liposomes and subsequently reduced the cytotoxicity of liposomal doxorubicin, although all the cell associated doxorubicin was found in nuclei.Surface pegylation prevented also the penetration of liposomes through human placenta.In active targeting, the limited cytotoxicity of the biotinylated doxorubicin conjugate was attributable to its entrapment in endo-lysosomes.Biotinylated pH-sensitive doxorubicin liposomes restored the cytotoxic activity of the drug.However, both biotinylated formulations used specific and unspecific cell uptake pathways.Biotinylation did not change the pharmacokinetics (i.e.circulation time and tumor tissue uptake) of pH-sensitive liposomes in vivo.The transit-compartment PK-PD model described well the nuclear concentration -effect relationships of free and liposomal doxorubicin.This study provided new information about the cellular, placental and in vivo pharmacokinetics of nanoparticulate drug delivery systems.
Author: Suvi K. Soininen
Language: English
Subfield: Biomaterials
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Funder: Itä-Suomen Yliopisto
OpenAlex ID: W3095237017