A comprehensive review on different approaches for tumor targeting using nanocarriers and recent developments with special focus on multifunctional approaches

Background: Despite tremendous advancements in cancer treatment delivery, we are still far from achieving successful cancer prognosis and cure. The use of new nanocarriers for site-specific delivery of anticancer medicines with lower toxicity has shown promise. However, the successful translation of these works into products remains a challenge. Hence, a thorough examination of the various nanocarrier systems is required, with particular emphasis on the more recent approaches. Area Covered: The review discusses how nanocarrier designs have evolved with each generation based on EPR, overexpressed receptors, stimuli-responsive systems, intracellular and extracellular targeting, immunotherapy, and the recent multifunctional theranostic approach, as well as their potential and limitations. The clinical translations of these systems, as well as the issues that have arisen, have been examined, along with potential future opportunities. Newer immunosystems and multifunctional theranostic methods have received special attention. Expert Opinion: It has been observed that nanocarrier systems have evolved in three major generations. Despite all of the efforts, clinical success is limited to the first generation of EPR-based passive targeting. Active targeting is mostly limited to the preclinical stage. Tumor heterogeneity and poor delivery to the location remain a key worry and roadblock. Hence, the newer generation nanocarriers need a more multifunctional approach, combining active targeting with immunotherapy and diagnostic contrast agent delivery. Newer theranostic designs with combined effects of chemotherapy, immunotherapy, and other therapies such as photodynamic, photothermal, and photoacoustic need to be worked on. Besides, there is a need of finding new cancer markers, toxicity studies, and scale-up approaches to these nanosystems.