Therapeutic and Sensing Applications of Nanomaterials

	Nanoparticles are always accompanied with the appearance of novel properties irrespective of the metallic or semiconductor origin. Evolution of the unique physical, chemical and electronic properties at the nanoscale forms the essence of the various applications of nanoscience and nanotechnology. The interplay between the nanomaterials and biological systems is of special significance, especially for the fluorescent nanomaterials, such as quantum dots (Q-dots), which have diverse imaging and sensing applications. However toxicity issues remain a lingering concern and propel research to prepare nontoxic Q-dots. We illustrate the synthesis of non-cadmium (cd) based Q-dots and its biolabeling and sensing applications. The synthesis of biocompatible zinc sulfide (ZnS) Q-dots and its interaction with silver nanoparticles (Ag NPs) leading to the fluorescence quenching of the Q-dots is demonstrated. The detailed mechanism involved was investigated which showed the applicability of the Q-dotsNP pair for possible Förster resonance energy transfer (FRET)/ nanometal surface energy transfer (NSET) applications. The synthesized ZnS Q-dots were employed as a fluorescent label, embedded within chitosan nanocarriers having folic acid (FA) as a targeting agent, for theranostic applications. The film forming ability of chitosan and the ability of ZnS Q-dots to undergo cation exchange transformation reaction was exploited for sensing and removal of heavy metal ions from water. The detailed procedure and mechanism of detection and removal is also demonstrated. Next, a simple microwave mediated synthesis of fluorescent C-dots using a biocompatible polymer, poly(ethylene glycol) (PEG), for the first time as precursor and pasivating agent. The detailed characterization of the C-dots in addition to its biolabeling application is also elucidated. Taking a step further, a simple room temperature based synthesis of gold nanoparticles (Au NPs) utilizing the synthesized C-dots as catalyst is demonstrated. The comprehensive characteristics of the Au NPs, its stability, and the influence of the varying amounts of precursor and catalyst on the synthesis of Au NPs are also unveiled. Further, we demonstrate the synthesis of versatile nanocarriers based on non-covalent interaction between gold nanoparticles and proteins which were able to deliver drug to mammalian cell line and leading to apoptotic cell death.