## 1 Introduction  
The use of structured nanomaterials promises to have a positive impact on the development of cancer treatments as well as detection and imaging [1; 2; 3; 4; 5]. Materials for cancer therapy require careful consideration regarding nanostructure shape and dimensions, surface charge, chemical composition, and hydrophobicity, as well as ligand size, orientation, density, and charge [5]. These factors are important and relevant to the toxicology, specificity, and clearance of the therapeutic agent in the human body. Structures with sizes that range from a few A up to 5 nm, for instance, are small enough to enter the smallest blood vessels in humans, including a new vasculature developed as part of metastatic processes. Structures in that size range are also compatible with renal clearance (threshold value of -5.5 nm) [6] and can penetrate pores in cells in the size range of 2 to 8 nm [7]. Nanotechnologies employed in cancer diagnosis and treatment generally consist of a core and a chemical modifier on the surface of the structure that adds molecular recognition and biocompatibility. These nanotechnologies include nanoparticles, polymeric micelles and liposomes, dendrimers, nanocantilevers, carbon nanotubes, and quantum dots. The most common applications for these materials vary, with liposomes, dendrimers, and polymeric micelles usually being employed as encapsulating agents and drug delivery vehicles, nanoparticles and quantum dots as therapeutic agents, and functionalized carbon nanotubes as platforms for both therapeutic agents and drug delivery systems. Functionalized nanocantilevers have tremendous potential for early cancer biomarker detection--including antibodies and antigen detection in vitro--at the single molecule level and can impact early detection of the condition. Current developments in nanotechnology that rely on functionalization to target specific cells and/or tissue usually result in structures with hydrodynamic radios that are too large to fulfill the size requirement to enter the small vasculature developed in tumor angiogenesis and are complex organic or organometallic structures with significant metabolic pathways causing several secondary effects. Such structures, while increasing the residence time of a target drug in the human body, can present a clearance problem by the kidneys and may have limited direct action on cancer cells trapped in small human vasculature associated with the metastatic process and may bring new metabolic processes that limit the amount of intake by humans. In these regards, naked CaS nanostructures and clusters have potential applications as target cell cancer and metastasis therapy agents. CaS is a homeopathic remedy known as _Hepar sulphuris_. It is used as a remedy in alternative medicine to treat colds, coughs, sore throats, creup, abscesses, e, earaches, inflamed cuts and wounds, asthma, arthritis, emphysema, herpes, constipation, conjunctivitis, _Candida albicans_ infections, syphilis, sinusitis, and skin infections [8]. However, the effect of CaS nanostructures on the growth and survival rate of cancer cells is unknown. This is surprising given the fact that it finds wide use as an alternative medicine for the symptoms listed above. The importance of rigorous scientific studies to establish the action of homeopathic remedies to fight cancer--as well as other diseases--has been highlighted recently. Such studies will facilitate easy and reliable medical advice from pseudoscience that is broadly available to the public [9]. Compared to many popular nanomaterials--including noble metals and magnetic nanoparticles--calcium and sulfur-based nanostructures are promising biocompatible inorganic materials. Calcium is an abundant mineral in the human body. It plays major roles in both macroscopic biological functions such as bone remodeling, and biological functions at the molecular level such as intracellular and extracellular communication, protein structures, and mitochondrial metabolism.