anticipated, it was observed that this is formulation is suitable for prolonged delivery of anticancer drugs by in vitro and blood-level studies in albino rats, without producing any signiﬁcant hematological disturbances. PEGylation contrib- uted an additional advantage to the dendrimer formulation by reducing drug leakage and hemolytic toxicity. This, in turn, could improve drug-loading capacity and stabilize such systems in the body. Dendrimers for targeted delivery In the last few years there has been a growing interest by various scientists to use dendrimers for targeted delivery especially in cancer therapeutics. The multifunctional nature of the dendritic network makes it easier for researchers to incorporate both the drug and the targeting moieties simultaneously, and thus can be used for active targeting. Furthermore, passive targeting of tumors can also be achieved through PEGylation on the surface of dendrimers. It is well established that PEGylated nanoparticles accumulate in the tumor tissues due to the EPR effect. On the surface of a variety of cancer cells, folate receptors are overexpressed.50 Folate-modiﬁed dendrimers target these cells via ligand- receptor recognition. Folic acid targeted dendrimers which are covalently conjugated with methotrexate speciﬁcally kill receptor-expressing cells after the intracellular delivery of the drug through receptor-mediated endocyctosis.51 Quintana and colleagues52 synthesized an ethylenediamine core PAMAM dendrimer of generation 5 which was covalently attached to folic acid, ﬂuorescein, and methotrexate. This complex provided targeting, imaging and intracellular drug delivery capabilities with 100-fold decreased cytotoxicity over free methotrexate. The unique architecture of dendrimers allows for mul- tivalent attachment of imaging probes as well as targeting moieties. Thus, it can be also used as highly efficient diagnostic tool for cancer imaging. Gadolinium (Gd)- based magnetic resonance imaging (MRI) contrast agents (CAs) can operate using an approximately 100-fold less concentration than iodine atoms required for computed tomography imaging. They can be targeted to a single site which improves the sensitivity of imaging. Furthermore, the size of the complex prevents leakage from the bloodstream into ﬂuids in the body, which also improves sensitivity and image clarity.53 Dendrimer and carbon nanotube The utilization of dendrimers as ‘nanotemplates’ for carbon nanotube formation in a controlled manner has been a International Journal of Nanomedicine 2009:4 Nanoparticles and cancer therapy growing area of research interest since Choi and his group introduced the idea of utilizing PAMAM dendrimers for the synthesis of catalytic nanoparticles for single-walled carbon nanotube (SWNT). Thus, using this dendritic platform, chemical vapor deposition (CVD) nanotubes with a narrow diameter distribution between 1 and 2 nm were obtained.54 Later, in another study by Amama and colleagues, the use of fourth-generation PAMAM dendrimers as a platform for synthesizing multi-walled carbon nanotubes (MWCNTs) with systematically varied diameter distributions and defect densities by microwave plasma-enhanced chemical vapor deposition was demonstrated. This technique involved the utilization Fe2O3 nanoparticles prepared via an interden- dritic templating mechanism involving Fe3+ ions and an amine-terminated dendrimer. The diameter distribution and quality of MWCNTs can be manipulated judiciously by varying the concentration of the catalyst solution and the calcination temperature.55 Alternatively, Pan and colleagues used PAMAM dendrimers to coat single-walled carbon nanotubes (SWCNTs) to reduce cytotoxicity and enhance cellular uptake. It was observed that dendrimer coated SWCNTs were nontoxic as compared to uncoated SWCNTs. Also, the uptake of uncoated SWCNTs in MCF-7 metastatic breast cancer cells was found to be signiﬁcantly less than the dendrimer coated nanotubes, due to increased dendrimer mediated endocytosis.56 Therefore, a homogeneous coating of a glycodendrimers on SWCNT known to decrease cytotocix- ity also shows the potential for nanotubes to be utilized as protein-binding sensors.57 Nanoparticles and toxicity Though in recent years there has been a rapid expansion in nanoparticle and nanotechnology research in consumer products, there is limited information on the possible toxic health effects on humans and the environment to date. To assess the toxicity in a systematic manner, there is an urgent need to investigate the intracellular and in vivo fate of the nanoparticulate systems vis-à-vis in surface properties and morphology. In an early study by Dunford and colleagues58 in 1997, it was demonstrated that titanium dioxide/zinc oxide nanoparticles used in sunscreen can catalyze oxidative damage to DNA in vitro and in cultured human ﬁbroblasts. In 2004, at a nanoscale materials and toxicity conference, Nanotox 2004, Vyvvan Howard revealed his initial ﬁndings that gold nanoparticles have the ability to move across the placenta from mother to fetus when injected into pregnant rats.59 There are a few studies that have assessed of toxicity of carbon nanotubes. Shvedova and colleagues60 hypothesized 5