US researchers have managed to create tiny chemical cages that enclose drugs within a capsule that can be manufactured to deliver drugs to organs or tissues without causing harm elsewhere.
The discovery spells good news for drug manufacturers and producers who have found the act of balancing drug efficacy with delivery an increasingly complex and laborious one.
The delivery of chemotherapy drugs is a classic example of this compromise. Chemotherapy is indiscriminate destroying cancer and normal cells alike. This is the reason why patients often lose their hair and/or suffer devastating side effects.
Previous techniques for assembling molecular cages involved tradeoffs. With one approach, the synthesis technique was straightforward, but the pieces of the molecular cages were not bound as tightly to each other.
Another approach resulted in tighter bonds, but the process required several carefully orchestrated steps.
Researchers at Rutgers, The State University of New Jersey, have created octahedral (eight-sided) capsules, with their cavity volume of almost two cubic nanometers. These cage-like molecules are called nanocontainers or nanoscale capsules because they measure a mere 3.2 nanometers (billionths of a metre) wide.
The process involves combining six larger bowl-shaped molecules with 12 smaller linear molecules, or bridges, that link the bowls together, insides facing each other.
Atoms at four sites along each bowl's rim bond to atoms on the ends of the bridges. The atomic structure and properties of these molecules ensure that they naturally assemble themselves into capsules and do so with high yield when combined in proper proportions.
Early research suggests that the connections between the bridges and bowls can be broken and reattached under controlled conditions to introduce "payload" molecules - such as a drug or pesticide - into the cage and extract them when needed.
"While the concept of chemical cages is not new, we've created new components and advanced the assembly process to increase the chance that they'll become practical," said Ralf Warmuth, associate professor of chemistry and chemical biology at Rutgers and lead researcher.
"We've shown a way to securely link molecules together in a cage using an efficient, one-step process," he added.
What is ultimately hoped is these structures will enclose one or more molecules of a medicine, pesticide or intermediate in a chemical manufacturing process that, if left uncaged, might prematurely decay or interact with other substances in passing.
The process could also make pesticides less hazardous to handle, filter toxic substances out of wastewater and regulate the pace of reactions in chemical production.
In drug delivery applications, higher loading rates, and the rate of release (achieved as the encapsulation material breaks down in the body), are the deciding success factors in producing effective drug release mechanisms.
The structure and quality of the material prevents dose dumping - the release of a higher dose of drug after it is first administered which then gradually tails off.
Slow-release drug delivery is a much larger opportunity, with the market valued at more than $20 billion, although the use of the technology in this setting is not so advanced as in brachytherapy, (short range intratumoural radiotherapy), for example.
Full text of the journal article can be viewed here.