Anticancer drugs lack specificity and act only at certain stages of cancer growth. And radiation and hyperthermia treatments are non-target specific. These treatments are given for debulking tumors, before surgery. However, each one has inherent side effects.
In such a scenario, what we need are therapeutic cargo agents that can deliver multiple drugs to cancer sites to precisely target and kill cancer cells. With this in mind, Sonal Thakore from the University of Baroda, in collaboration with Sriram Seshadri from the Nirma University, came up with a multi-functional system.
They synthesized a multifaceted agent using a simple one-pot method. The agent had a magnetic core of iron oxide nanoparticles. The team functionalized the core with cyclodextrin, an oligosaccharide, using a linker molecule. Cyclodextrin is non-toxic and can encapsulate both hydrophobic and hydrophilic drugs.
As hydrophobic drug, they chose curcumin, a phytomolecule from turmeric. Curcumin is known for its anticancer and antioxidant properties. The hydrophilic drug was doxorubicin, commercially used in chemotherapy.
Cancer cells express more folic acid receptors. So, the team introduced folic acid ligands to make the cargo bind specifically to cancer cells. They added fluorescein molecules to help image the location of the delivered cargo.
To make it a smart cargo, the team exploited the pH of the micro-environment of the cancer cells. The changes in pH help the cargo unload the drug molecules. Acidic pH facilitated doxorubicin release and neutral pH helped curcumin release.
When alternating magnetic fields are applied, the high magnetization values of the iron oxide core produces heat and aids in thermal therapy.
“We observed that, at a safer field frequency of 285 kilohertz, the temperature of one milligram per millilitre of the nano-conjugates rises to 40-45 ⁰C in twenty minutes, without affecting normal cells,” says Sonal Thakore, University of Baroda.
The team found 45% of curcumin and 32% of doxorubicin entrapped in the nano-conjugates. They observed that 80% of both drugs are released at 40 ⁰C.
In-vitro studies showed enhanced cellular uptake of the folic acid bound nano-conjugates. The internalization increased under a magnetic field. This could be easily visualized because of the fluorescein molecules attached to the cargo.
Electron microscopy revealed spherical nano-conjugates of 55-65 nano-meters, a size range that was enough to avoid them being engulfed by macrophages and to facilitate removal from blood circulation.
A hemolysis study revealed the nano-conjugates to be non-hemolytic. “Nano-conjugates without drug were safe. But drug-loaded nano-conjugates killed cancer cells. Even at ten micrograms per litre concentration,” says Apeksha Joshi from the University of Baroda.
The team used a hepatocellular cancer mouse model to study in-vivo efficacy. In the nano-conjugate group, they observed no change in body or liver weight, a change that normally happens due to tumor growth. Alpha fetoprotein, an important biomarker, was reduced. Inflammatory cytokines and matrix metalloproteinase levels also diminished. And functional indices of liver were also restored.
The team hopes that these multi-functional nano-conjugates will soon be used as theranostic agents for cancer diagnosis and therapy. Good news for cancer specialists and patients.
Carbohydrate Polymers, 206: 694-705 (15 FEB 2019); DOI: 10.1016/j.carbpol.2018.11.049