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Cancer is still a leading cause of death worldwide. Despite the progress in the molecular understanding of cancer diseases, there’s an urgent need in novel therapeutics and drug delivery strategies. Many novel anti-cancer compounds in early development are characterized by unfavorable physico-chemical properties and lack in drug-like properties. As a result, many of these compounds suffer from insufficient pharmacokinetic properties and show a high accumulation in off- target tissue that can induce dose-limiting side effects. Nanomedicines depict a promising strategy to optimize the pharmacokinetics of such compounds and to deliver them to their site of action: The cancer cell. The goal of this thesis was to develop nanoparticulate drug delivery platforms for passive and active drug targeting. In addition, a novel nanoparticle-based gene therapeutic for the treatment of liver cancer was evaluated. This thesis can be summarized in two main parts as follows: In a first part, a biocompatible and biodegradable polymer was used to prepare micelles for the delivery of small molecular anticancer drugs. These micelles were tested subsequently on in vitro and in vivo models. A highly reproducible protocol for the formulation of doxorubicin-loaded micelles was developed and micelles were characterized extensively for their physico-chemical properties. Cellular uptake of micelles was analyzed and their therapeutic potential was assessed in vitro on human cancer cells. To passively accumulate in solid tumors, nanoparticles need to be long-circulating and must remain in the blood circulation for hours. Therefore, the pharmacokinetic profile and biodistribution of doxorubicin-loaded micelles in rats was analyzed and compared to the gold standard of long-circulating nanoparticles: PEGylated liposomes. In a next step, a protocol for the preparation of so-called gold-nanohybrids was developed. Such nanohybrids are valuable tools to analyze nanoparticle-cell interactions and the intracellular fate of nanoparticles in detail. Further, such nanoparticles can be used as diagnostic tools. In a last step, micelles were functionalized with an antibody for targeted drug delivery. Cellular internalization of these micelles was analyzed using an array of methods. In a second part, a novel therapeutic strategy using the main effector protein of the rat parvovirus (H-1) for the treatment of hepatocellular carcinoma (HCC) was developed. H-1 parvovirus showed promising results in the preclinical setting and was consequently tested in a clinical trial in patients suffering form glioma. Despite this development, viral therapies may be linked with several issues. Therefore, the potential of the viral effector protein NS1 for the treatment of liver cancer was analyzed after non-viral gene delivery. In a first step, the gene-delivery efficiency and the therapeutic effect were analyzed in a panel of human liver cancer-derived cell lines. Various in vitro assays were used to study the NS1-induced cell death in detail. To show that this therapeutic approach is specific for cancer cells, the treatment was furthermore tested on healthy human liver cells. To identify cells that are susceptible for this therapeutic approach, a biomarker for the sensitivity to non-viral NS1 therapy was evaluated. Finally, safety of this therapy was analyzed in mice after single and multiple dosing.