Nanoparticles are structures that are between 1 and 100 nanometers in size. Due to their scale, these structures are being developed for drug delivery systems because they are a similar size to many biomolecules found in the cell. This size gives them the ability to bypass normal clearance routes and body defence systems. Work published in the journal Advanced Matter, by researchers at Washington State University (WSU), successfully demonstrated that cancer-killing nanoparticles can access diseased tissue by piggybacking onto white blood cells called neutrophils .
Neutrophils can infiltrate tumors, delivering therapeutic agents, which would normally be removed by the blood clearance pathways that protect tumors. The researchers at WSU exposed a carcinoma tumor in the flank of a mouse to infrared light, which caused an inflammatory reaction and the tumor to release signals to attract neutrophils. They then injected gold nanoparticles covered in antibodies (molecules which attach neutrophils) into the mouse. The nanoparticles adhered to the mouse’s neutrophils and piggybacked into the tumor. When they exposed the tumor to infrared light, the gold nanoparticles produced heat and killed the tumor cells.
One of the biggest challenges in Oncology is destroying malignant tissue without damaging the surrounding healthy tissue. Nanostructures like gold nanoparticles may offer a more precise delivery strategy for cancer therapeutics in the future.
The first Food and Drug Administration (FDA) approved nano-drug was Doxil®, which is the chemotherapy agent doxorubicin surrounded by a lipid-bilayer. The lipid shell surrounding the drug prolongs the circulation time and targets the drug directly to the tumor due to the enhanced permeability and retention (EPR) effect .
EPR is a phenomenon associated with solid tumors, as they have a high density of blood vessels and the cells lining these blood vessels have gaps between them which allows the accumulation of large molecules and nanoparticles; this means that drugs tend to accumulate in tumor tissue much more that healthy tissue. This phenomenon is one of the primary reasons why companies and researchers are pursuing nanotherapeutic strategies, as they can capitalise on the EPR effect to deliver drugs directly to tumor tissue .
 Adv. Mater. 2017, 1701021., , , , ,
 Yechezkel (Chezy) Barenholz, Doxil® — The first FDA-approved nano-drug: Lessons learned, Journal of Controlled Release, Volume 160, Issue 2, 10 June 2012, Pages 117-134, ISSN 0168-3659.
 Jun Fang, Hideaki Nakamura, Hiroshi Maeda, The EPR effect: Unique features of tumor blood vessels for drug delivery, factors involved, and limitations and augmentation of the effect, Advanced Drug Delivery Reviews, Volume 63, Issue 3, 18 March 2011, Pages 136-151, ISSN 0169-409X,