Layered Nanocapsule Shows Promise in Cancer Drug Delivery

Scientists at the University of Alabama at Birmingham have developed polymer capsules that could play a key role in delivering targeted cancer therapies.

The multi-layer capsules show traits that have been traditionally hard to achieve through 1 delivery vehicle. The capsules have idea imaging contrast, can encapsulate the cancer therapy doxorubicin, and can release the drug through low- and high-dose ultrasound, according to a press release. These 3 aspects of the capsules are able to work together to create a targeted drug therapy.

The study authors believe that therapeutic efficacy could be further improved through modifications that boost targeting, according to the release. Then, low-dose ultrasound could image the capsules that aggregate in the tumor, while higher-dose ultrasound would release the drug. This method would prevent the rest of the body toxicity associated with cancer drugs, and could reduce side effects.

In the study, published by ACS Nano, the authors reported that the increased control of when and where cancer drugs are released could offer patients an alternative to surgery or chemotherapy.

“We envision an entirely different approach to treating solid human tumors of numerous pathologic subtypes, including common metastatic malignancies such as breast, melanoma, colon, prostate and lung, utilizing these capsules as a delivery platform,” said researcher Eugenia Kharlampieva, PhD. “These capsules can protect encapsulated therapeutics from degradation or clearance prior to reaching the target and have ultrasound contrast as a means of visualizing the drug release. They can release their encapsulated drug cargo in specific locations via externally applied ultrasound exposure.”

Although there are more targeted treatment options available, the authors said there is still an unmet need for an easily producible, targeted drug delivery approaches.

In the study, the scientists used layers of biocompatible tannic acid and poly(N-vinylpyrrolidone) (TA/PVPON) to create the novel nanocapsules. The core of the capsules are composed of solid silica or porous calcium carbonate that are dissolvable.

Through varying the layers of the capsule, the authors were able to change the physical traits of the drug delivery vehicle and its sensitivity to ultrasound, according to the release.

The authors discovered that one-fourth of empty capsules composed of 4 layers of TA/low-molecular weight PVPON ruptured 3 minutes following ultrasound, while 15 layer capsules composed of the same materials did not rupture. These findings suggest that the ratio of the thickness of the capsule wall is the key to controlling rupture.

To test the ultrasound imaging contrast of the nanocapsules, the authors developed capsules that were 5 micrometers wide, which were 2 times the size of those included in the rupture analyses, according to the study.

Compared with empty capsules, when the capsules were loaded with doxorubicin, the imagining contrast increased 2- to 8-fold. These capsules were observed to be highly stable, even after 6 months of storage, according to the release.

The study authors said the novel capsules show promise as an effective cancer drug delivery vehicle when used with ultrasound. Next steps include studying the efficacy in animal models to determine how long the capsules persist in the blood and where they distribute, the press release concluded.