Design of Nanoparticles as Drug Carriers for Cancer Therapy

This review explores the recent chemotherapeutic work on drug delivery using nanoparticles as carriers for the targeted treatment of cancer. Compared to direct drug delivery, delivery through a carrier can increase the efficacy of a drug, but decrease the side-effects by utilizing the enhanced permeability and retention (EPR) effect and tumor-specific targeting. The search for efficient and safe transport vehicles (carriers) to achieve better drug availability at the target site has been a challenging yet exciting area of research. Current interest focuses on the colloidal nanoparticles (diameter 85%) are related to solid tumors, current cancer therapy usually involves intrusive processes including the application of catheters for chemotherapy, with initial chemotherapy to shrink any cancer present, surgery to remove the tumor(s) if possible, followed by chemotherapy and radiation to kill the tumor cells. Research efforts to improve chemotherapy over the past 25 years have led to an improvement in patient survival. However, the efficacy of the therapy and the possible side-effects vary among different agents. Some drugs may have excellent efficacy, but also serious side-effects affecting the quality of life. In addition, they may be in limited supply and, therefore, very expensive. More effective and less expensive anticancer drugs have been under development. A typical example is dEpoB, which was synthesized based on the mechanism of action of paclitaxel and is reportedly 30 times more effective than paclitaxel (3). However, it normally takes at least 10 years and billions of dollars to discover a new drug. The development of new anticancer drug delivery systems or new administration schedules offer less expensive, but more effective, treatment with negligible side-effects. Usually, a pharmaceutical agent will distribute evenly within the body. However, ideal chemotherapeutics require a high local concentration of the drug at the disease site(s), while the concentration in other non-target organs and tissues should be below a certain minimal level to prevent any negative side-effects. The concept of drug targeting, also called the "magic bullet", comes from the experience of the 19th century German chemist, Paul Ehrlich, who selectively stained bacteria for histological examination. The "magic bullet" as an entity comprises two components: one should recognize and bind the target, while the other should provide a therapeutic action in this target. In the clinical setting, anticancer payloads, such as radionucleotides, toxins and