Nanomedicine and Chemotherapeutics Drug Delivery: Challenges and Opportunities

Cancer is considered as one of the biggest threats to human worldwide. Researchers suggest that tumour is not just a single mass, it comprises cancerous cells surrounded by noncancerous cells such as immune cells, adipocytes, and cancer stem cells (CSCs) in the extracellular matrix (ECM) contains distinct components such as proteins, glycoproteins, and enzymes; thus tumour microenvironment (TME) is partially complex. Multiple interactions happen in the dynamic microenvironment (ME) lead to an acidic, hypoxic, and stiff ME that is considered as one of the major contributors to cancer progression and metastasis. Furthermore, TME involves drug resistance mechanisms and affects enhanced permeability and retention (EPR) in tumours. In such a scenario, the first step to accomplish satisfying results is the identification and recognition of this ME, then designing proper drug delivery systems can perform selectively toward cancerous cells. Several targeting and stimuli/enzyme responsive drug delivery systems have been designed. More importantly, it is necessary to design a drug delivery system that can penetrate deeper into the tumours, efficiently, and selectively. Various drug delivery systems such as exosomes and size-switchable nanocarriers (NCs) could decrease side effects and increase tumour treatment results by selective accumulation in tumours. In this review, TME features, current drug delivery approaches, challenges, and promising strategies toward cancer treatment will be discussed.