Chemists using green chemistry to deliver cutting-edge drugsPublished On: Fri, Sep 14th, 2007 | Biology | By BioNews
Washington, September 14: Chemists at the University of Nottingham are using green chemistry techniques for coating drugs in plastics, which may provide an effective delivery system for the cutting-edge drugs.
The researchers say that with their technique, the bioactive elements of the drug remain completely effective, which is why it may provide the maximum benefit of the therapy to patients.
According to them, the plastic is designed to release the drug over a controlled period of time, minimising the number of injections a patient will need and maximising the effect of the drug.
Professor Steve Howdle outlined the green chemistry processes being pioneered at The University of Nottingham, particularly the use of supercritical fluids to replace conventional solvents such as benzene and chloroform, at the British Association for the Advancement of Science Conference in York on September 12.
He said that his research focused on exploiting the unique properties of supercritical carbon dioxide (CO2).
A supercritical fluid is a solvent, with physical properties between those of a gas and a liquid. At near-room temperature and under modest pressure, supercritical carbon dioxide blurs the boundaries between liquid and gaseous states.
Prof. Howdle says that the process can be used to make polymer drug coatings, using biodegradable plastics, just like those used in dissolvable surgical stitches. The polymer is used to encapsulate the drug before it is injected into the body, he adds.
He said that his research aims at removing conventional solvents from the process altogether because they can destroy up to 50 per cent of the drug molecules intended to help the patient.
The researcher also said that his research had demonstrated that biodegradable polymers could be plasticized at near room temperatures using supercritical CO2, indicating that delicate bioactive components like growth factors or proteins could be mixed into the plasticised polymer without any loss of activity.
“Many very potent new drugs based on proteins are being discovered all the time. But a major problem the pharmaceutical industry faces is that they have to be wrapped up in plastic to be delivered to the patient, so that there is controlled release of the drug over time,” said Prof. Howdle.
He further said that the process overcame a major obstacle to the development of new drug delivery devices, as it meant that patients would be able to receive biopharmaceuticals which do not survive conventional chemical processing because they are either solvent or sensitive to heat.
“Many of these new proteins are fragile and are damaged by high temperatures and harsh solvents used in conventional processes. Our process works in CO2 at close to room temperatures so the molecule is not damaged by the mixing process, and we don’t use normal solvents we don’t have toxic residues left behind in the product and potentially ending up in the patient,” he said.
“The plastics are solids but when they are put under high pressure from CO2, they turn into liquids – they melt, and under these conditions, the bioactive drugs can be mixed in. So we take particles of the drug and wrap every single one up in biodegradable polymer, for injection under the skin,” he added.
Prof. Howdle said that the process being pioneered at the University of Nottingham will help reduce side effects and improve quality of patients’ life.
“Biodegradable polymers are particularly attractive for use in drug delivery, as once introduced into the body they require no retrieval or further manipulation and are degraded into soluble, non-toxic by-products. Different polymers degrade at different rates within the body and therefore polymer selection can be tailored to achieve desired release rates,” he said.
“Thus the process allows for gradual, controlled release of a drug, reducing side effects and improving quality of life. For the patient, it could mean the end of twice-daily injections – in favour of an injection once a week,” he added.