At present, several nanoparticle-based chemotherapeutics are clinically approved and many more are in various stages of clinical or preclinical development.
Among emergent nanoscale drug carriers, liposomes, polymeric nanoparticles, and micelles have demonstrated great potential clinical impacts. Active targeting approaches may be achieved by conjugating nanocarriers containing chemotherapeutics to molecules that bind to over expressed antigens. Compared to conventional chemotherapeutic agents, nanoscale drug carriers have demonstrated the potential to address some of these challenges by improving treatment efficacy while avoiding toxicity in normal cells due to features such as high selective accumulation in tumors via the enhanced permeability and retention (EPR) effect and active cellular uptake 12, 13. The emergence of nanotechnology has had a profound impact on clinical therapeutics in general in last two decades. In the last few years, a better understanding of tumor biology and increased availability of versatile materials, including polymers 2, 3, 4, 5, lipids 6, 7, inorganic carriers 8, polymeric hydrogels 9, 10, and biomacromolecular scaffolds 11, have led to the development of systems that can deliver chemotherapeutics to tumor sites with improved therapeutic efficacy. Therefore, it is desirable to develop chemotherapeutics that can either passively or actively target cancerous cells, thereby reducing adverse side effects while improving therapeutic efficacy. Additionally, as the bio-accessibility of these drugs to tumor tissues is relatively poor, higher doses are required, leading to elevated toxicity in normal cells and an increased incidence of multiple drug resistance.
In fact, the severe adverse effects induced by chemotherapeutic drugs on healthy tissues and organs are a major reason behind the high mortality rate of cancer patients. The agents are nonselective and can also damage healthy normal tissues, causing severe unintended and undesirable side effects, e.g., loss of appetite and nausea. Conventional chemotherapy works primarily by interfering with DNA synthesis and mitosis, leading to the death of rapidly growing and dividing cancer cells. Current cancer treatment options include surgical intervention, chemotherapy, and radiation therapy or a combination of these options. However, the mortality rate has decreased in the past 5 years due to a better understanding of tumor biology and improved diagnostic devices and treatments. With more than 10 million new cases each year, cancer-related deaths are projected to increase in the near future with an estimation by the World Health Organization of ~13.1 million cancer-related deaths by the year 2030 1. Cancer includes a range of diseases that arise as a result of the unregulated growth of malignant cells, which have the potential to invade or spread to other body parts.