Small silica bottles filled with medication and a special temperature-sensitive material could only be used for drug delivery to kill malignant cells only in certain parts of the body, according to a study recently published by researchers at the Georgia Institute of Technology.
The research team devised a way to create silica-based hollow spheres about 200 nanometers in size, each with a small hole in the surface that could allow the spheres to encapsulate a wide range of payloads that could only be released later at certain temperatures.
In the study, published on June 4 in the journal Applied Chemistry International Edition, the researchers describe packing the balls with a mixture of fatty acids, an almost infrared dye and an anticancer agent. The fatty acids remain solid at human body temperature but melt a few degrees above. When an infrared laser is absorbed by the dye, the fatty acids are quickly lubricated to release the therapeutic drug.
"This new method could allow infusion therapies to target certain parts of the body and potentially negate certain side effects because the drug is released only where there is an elevated temperature," said Younan Xia, professor and Brock Family Chair of the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. "The rest of the drug remains encapsulated by the solid fatty acids inside the bottles, which are biocompatible and biodegradable."
The researchers also showed that the size of the hole could be changed, allowing nanocapsules to release their payload at different speeds.
"This approach holds great promise for medical applications that require drugs to be released in a controlled manner and have advantages over other methods of controlled drug release," Xia said.
An earlier method of obtaining controlled drug release involves loading the temperature sensitive material into low density lipoproteins, often referred to as "bad cholesterol". Another method involves loading the mixture into gold nanocages. Both have disadvantages in how the material used to encapsulate the drugs interact with the body, according to the study.
To make the silicon-based bottles, the research team started producing polystyrene balls with a small gold nanoparticle embedded in its surface. The beads are then coated with a silica-based material everywhere except where the gold nanoparticle is embedded. Once the gold and polystyrene are removed, there is only a hollow silica ball with a small opening remaining. To adjust the size of the orifice, the researchers simply resized the gold nanoparticle.
The process of filling the bottles with their payload involves softening the balls in a solution containing the mixture, removing the trapped air, then washing of excess material and payload with water. The resulting nanocapsules contain an even mixture of the temperature sensitive material, the therapeutic drug and the dye.
To test the release mechanism, the researchers then put the nanocapsules in water and used an almost infrared laser to heat the dye while tracking the concentration of the released therapeutic agent. The test confirmed that without the use of laser, the drug remains encapsulated. After several minutes of heating, the therapeutic agent's concentrations in the water increased.
"This controlled release system allows us to deal with the deleterious effects associated with most chemotherapies by only releasing the drug at a toxic dose level in the diseased place," said Jichuan Qiu, a postdoctoral fellow at Xia- group.
This research was supported by the National Science Foundation under grant number ECCS-1542174 through the national nanotechnology coordinated infrastructure. The work was also supported by the China Scholarship Council through a graduate student scholarship. The content is the author's responsibility and does not necessarily represent the official views of the sponsoring agencies.
CITATION: Jichuan Qiu, Da Huo, Jiajia Xue, Guanghui Zhu, Hong Lui, and Younan Xia, "Encapsulating a phase change material in nanocapsules with a well-defined hole in the controlled drug release wall," (Applied Chemistry International Edition, July 2019). http: // dx.
Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases sent to EurekAlert! by contributing to institutions or to using information through the EurekAlert system.