Linkers: The key elements for the creation of efficient nanotherapeutics.

The limited efficiency of the conventional treatment options against a variety of disorders have created demands towards the development of more efficient theranostic strategies. Advances in nanomedicine have provided promising perspectives for the treatment of hard-to-treat diseases. Application of the high-resolution imaging, multifunctional nanoparticles, and a wide variety of nanodevices for early diagnosis of disease, promoting tissue regeneration, and targeted delivery of therapeutic agents, may result in minimal side effects and improved treatment outcome. Meanwhile, a number of nanotherapeutics have shown poor efficiency that might be due to a variety of factors including the inappropriate design protocols or nonspecific drug release. Selective cell targeting and controlled drug release are the key elements which should be considered in designing the nanocarriers for targeted delivery of therapeutic agents. Linkers, the essential components incorporated in the building blocks of drug delivery systems, provide the stability, high payloads, targeted drug delivery, and controlled release, hence, they might be critically involved in the nanotherapeutic activity. In the present review, the significance of linkers in the development of effective drug delivery systems has been highlighted.