**4. Attachment of ligands to carriers**

Most of the nanoparticles as specially lipid-based formulations and polymeric nanoparticles are emerging as the best carrier system to deliver the molecule in cancerous tissues [24]. Monoclonal antibodies and peptides are possibly the best carriers. The surface-bound ligands specifically bind to the target cells. The various techniques viz., covalent and non-covalent techniques help in effective active targeting of cancer cells (**Figure 1**).
