**Abstract**

Cancer is caused by an uncontrolled cell division, forming a tumor capable of metastasis. Cancer is the second leading cause of death worldwide. Conventional treatments kill healthy cells, causing side effects. Recently, nanomaterials are explored due to properties such as as- nano-size, high loading, and ligands' attachment for a selective delivery. Apart from normal body cells, cancer cells express many receptors in excess, which serve as 'targets' for attacking the cells. Various ligands like proteins, peptides, polysaccharides can be attached to nanoparticles to allow proper and specific reach to the tumor. Such nanoparticles go to their desired site and stick onto the receptors, taken inside the cells by various methods. Antibodies are natural proteins that bind to foreign substances and remove them. IgG being the most explored antibody, suffers from many disadvantages such as non-specificity for required antigen, limited binding sites, low tumor penetration. Hence many researchers experimented by removing and adjusting the binding sites, using only the binding sites, enhancing the valency of naturally available IgG. It gave many benefits such as enhanced penetration, reduced immunogenicity, better delivery of drugs with fewer side effects. Continuing advancements in the field of protein engineering will help scientists to come up with better solutions. The properties allow easy surface interaction and entry, achieve better biodistribution, and reduce the amount of drug required. Targeting is based on Paul Ehrlich's 'magic bullet, 'where the therapeutic moiety has two parts-one to identify the target and the second to eliminate it. This concept is revised to incorporate a third component, a carrier. Many nanocarriers can be used to target cancer cells containing ligands to identify malignant cells. Approaches to targeting are passive, active and physical targeting. Many such nanoparticles are in clinical trials and can be a better solution to cancer therapy.

**Keywords:** nanoparticles, cancer immunotherapy, targeted drug delivery, cancer, targeting, nanomedicine, antibody fragments
