By Sahana Ghosh
Kolkata, Jan 28 (IANS): Upping the ante for a competent drug delivery system that specifically destroys cancer cells and ensures reduced toxicity to the normal ones, Indian scientists have successfully used a new strategy to enhance targeted drug release by nanoparticles.

Targeted drug release confines the medication - which for cancer is fraught with side effects - to the specific location within the body, prolongs its action on the affected part and reduces the amount of drug circulating in body fluids, preventing exposure to healthy cells.

According to a WHO report, one in every 10 Indians runs the risk of getting cancer before 75 years of age, while seven in every 100 is at risk of dying from cancer before their 75th birthday.

This rising graph necessitates cutting-edge therapy.

Small but powerful in impact, carbon nanotubes (miniscule spaghetti-like particles fabricated from carbon) have dominated the scientific arena for their myriad applications in electronics, material science and medicine.

As their name suggests, carbon nanotubes (CNT) measure in nanometres - 50,000 times smaller than the width of human hair - while their length extends till a few millimetres.

This size is perfect for loading considerable amount of cargo (drugs, proteins and the like) and because they can spontaneously cross through cell membrane barriers, they are quite a sensation with scientists studying drug delivery mechanisms.

Being solid, CNTs are aided by a dispersing agent to ease their diffusion into biological fluids and liquid mediums.

A group at the Indian Association for the Cultivation of Science (IACS) here used a type of vitamin - biotin or Vitamin B7 - as part of the dispersal medium of the CNT.

Attached to the nanoparticle surface (as part of its dispersing agent) biotin facilitated the "selective" unloading of the drug at the destined stop - the lethal cancer cell. Doxorubicin, a popular chemotherapy drug, was chosen for the study.

"The structure of the CNT-dispersing agent was simplified and modified so that it could effectively deliver the drug to the cancer cell and cause minimum damage to normal cells," Prasanta Das, who led the study at the department of biological chemistry at IACS, told IANS.

"A good drug delivery vehicle needs to remain intact while it carries out its function. It should be compatible with the host's body (biocompatible) and, most importantly, it should be target-specific so that it does not destroy neighbouring normal body cells," Das explained.

Here lies the importance of biotin, which is an essential vitamin for the growth of all cells.

But the demand for this vitamin is considerably higher in rapidly dividing cells and tissues, like cancer cells. Cells absorb this substance via receptors on their surface, like a key fitting into a particular lock.

"Biotin receptors (that absorb the vitamin molecule) are produced at elevated levels in certain types of tumours like breast, ovary, kidney, liver, prostate, and some lung cell lines," said Das about the study that is published in the January issue of Journal of Materials Chemistry.

So, when a biotin-equipped CNT was administered (in a cell culture), it recognised the desired cancer cells through the receptor and stealthily released doxorubicin inside them.

"Not only was it selective, it remained intact during transit. Moreover, toxicity to normal cells was remarkably reduced."

If 100 cancer cells were decimated, then around 20 normal cells were affected, which is an "improvement" over other variants of CNTs tested across the world. Besides, it did not interfere with the nanotube's function.

The next step for Das and his team is to verify the findings in a living organism and assess its toxicity to the host, including if it can be naturally flushed out from the body, Alok Dhawan, an expert in nanomaterial toxicology, said.

"CNTs should be modified in such a way so as to reduce their direct interaction with vital molecules in cells like DNA and proteins. Their excretion from the body is an important factor in determining long-term toxicity," Dhawan, Director of Ahmedabad University's Institute of Life Sciences, told IANS via email.