IGIB team enhances the efficiency of DNA delivery into the skin for treating skin disorders

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Dr. Munia Ganguli (left) and Dr. Manik Vij have improved DNA penetration into skin by pretreating the skin with silicone oil. – Photo: Lavanya Lokhande.

By pretreating the skin with silicone oil, a team of researchers led by Dr. Munia Ganguli from the Delhi-based Institute of Genomics and Integrative Biology (CSIR-IGIB) has been successful in delivering plasmid DNA into the skin with greater efficiency and without destroying the integrity of the skin. Unlike other enhancers currently being used, preliminary studies show that silicone oil did not get into the skin nor cause any harm. Enhancing the ability of the plasmid DNA, packaged as a nanometer-sized complex with a peptide, to penetrate the skin will go a long way in efficiently delivering drugs for skin disorders. The results were published in the journal Molecular Therapy.

“Topical application of silicone oil on the skin prior to applying the DNA-peptide (which acts as a carrier of DNA) complex allows the DNA to reach the lower part of the epidermal layer of the skin; a little bit of DNA gets into the dermis as well,” says Dr. Ganguli, the corresponding author of the paper.

The skin with its three layers — stratum corneum (top layer), the epidermis (middle layer) and dermis (inner layer) — acts as a tough barrier for the entry of any foreign substance. Since the top layer of the skin is rich in lipids it becomes particularly difficult for the DNA (which is water-loving or hydrophilic) to penetrate it.

Only 30% of cells have the DNA complex when the skin is not pretreated with silicone oil. It increases to 45% once the skin is pretreated. “Silicone oil forms an occlusive layer which prevents water loss from the skin and keeps it well hydrated. The rise in hydration pressure, in turn, opens up many porous pathways for entry of the DNA complexes into the skin,” says Dr. Manika Vij from CSIR-IGIB and the first author of the paper. Besides increased hydration, there are also minor changes in the lipid and protein organisation in the skin.

The use of another enhancer (sodium laureth sulfate-phenyl piperazine — SLA-PP) in place of silicone oil also improves DNA penetration but it was found to damage the skin and was highly toxic to the skin cells; when applied on cell lines, plenty of cells died after 24 hours.

The researchers used hairless mice (the absence of hair follicles makes the skin more closely comparable to human skin) to test the penetration of DNA into the skin. Since the DNA is labelled with fluorescein, it was possible to measure the amount of nanocomplexes that got into the skin by measuring the fluorescence. Other tests revealed that topical application of silicone oil does not damage the integrity of the skin or damage the tissues.

Other potential applications

Talking about potential use of the DNA nanocomplexes along with silicone oil, Dr. Vij says: “In the DNA we can put any gene that encodes for any specific therapeutic protein. This way we can address several skin diseases.”

The researchers are planning to test the ability of the peptide-DNA complexes to cross the skin and enter the blood. “If it does, then it increases the potential to address diseases of other organs,” Dr. Vij says. “We are yet to carry out studies to see if the DNA gets into the blood circulation or gets locally degraded in the skin cells.”

Published in The Hindu on April 14, 2017

IISER Kolkata makes targeted delivery of cancer drug possible

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Dr. Sayan Bhattacharyya (left) and Sutanu Kapri have covalently bound cancer drug to nanospheres to deliver it inside only cancerous cells.

Targeted delivery of anticancer drugs exclusively to cancer cells and controlled release of the drugs in a sustained manner inside cancer cells has been achieved by a group of researchers from the Indian Institute of Science Education and Research (IISER) Kolkata. Porous carbon nanospheres about 150 nm in diameter and packed with drugs inside the pores has been designed in such a way that they cannot get inside normal cells and kill them. The results were published in the journal Carbon.

A team led by Dr. Sayan Bhattacharyya from the Department of Chemical Sciences, IISER Kolkata, used the commonly available lemon grass to synthesise the porous carbon nanospheres, which act as drug carriers. “It’s a very simple and cheap process to produce carbon nanospheres from lemon grass. Also, it is possible to scale up the production,” Dr. Bhattacharyya says.

The anticancer drug doxorubicin is covalently bound both inside the 3.6-3.8 nm diameter pores and also on the surface of the nanospheres. “Since the inside of the cancer cell is acidic (pH 5.5-6), the hydrazone covalent bond gets broken slowly to release the drug. As normal cells have a neutral pH the covalent bonds are less likely to be broken and therefore the drug cannot be released,” says Sutanu Kapri from the Department of Chemical Sciences, IISER, Kolkata, and the first author of the paper. “Also, in the presence of acidic environment, a proton gets added to the amine group of the drug and helps in the release of the drug from the pores.”

The checks and balances in targeted delivery ensures that negligible amount of cancer drug is available inside normal cells.To make the targeted delivery nearly fail-proof, the researchers attached folic acid to the nanospheres. The folic acid attaches to the folate receptors found on the surface of cancer cells and the nanospheres gain entry into cancer cells. Normal cells contain very few folate receptors and so nanospheres are nearly prevented from getting inside. Due to poor folate expression in normal cells, even after 15 hours, the amount of drug available inside normal cells was negligible compared with cancerous cells.

“The efficiency of nanospheres to get inside healthy cells will be less compared with cancerous cells. The larger the size of particles, the slimmer the chances of getting inside cells,” says Dr. Sankar Maiti from the Department of Biological Science, IISER, Kolkata, and one of the authors of the paper, while explaining how the relatively large (150 nm) nanospheres selectively target only the cancerous cells.

All these checks and balances ensure that drug release is minimal inside the healthy cells. In contrast, conventional chemotherapy is not designed to target only the cancerous cells. As a result, cancer treatment tends to kill more of healthy cells than cancerous cells.

Controlled release

Besides targeted delivery, the researchers had designed the nanospheres for controlled release of the anticancer drug. “Usually, there is a sudden burst of drug inside cancerous cells. But we can control the release of the drug inside cancerous cells over a 24-48-hour period, useful for clinical applications. This is mainly because the drug is chemically trapped inside the pores of the nanocarriers,” says Dr. Bhattacharyya.

Since the nanospheres contain numerous pores, the surface area increases, and a greater quantity of drug can be loaded inside the nanocarriers. Unlike when drugs are physically adsorbed on the surface of a nanocarrier, there is slim possibility of premature release of the drug into blood when the drug is bound to a nanocarrier.

Compared with freely available anticancer drug, the researchers found that the quantity of drug carried by nanospheres was 10 times more inside cancerous cells. Though nanocarriers cannot enter the nucleus, higher doses of the drug ended up inside the nucleus after 15 hours.

“So nanocarriers can effectively deliver drug in a controlled manner at targeted sites only if they have a porous structure, the drug remains inside pores and is covalently bound to nanospheres and is released only when the pH is acidic,” says Dr. Bhattacharyya.

Published in The Hindu on October 22, 2016