Navigation Links
Nanoparticles, 'pH phoresis' could improve cancer drug delivery

WEST LAFAYETTE, Ind. -- Researchers have developed a concept to potentially improve delivery of drugs for cancer treatment using nanoparticles that concentrate and expand in the presence of higher acidity found in tumor cells.

The concept involves using nanoparticles made of "weak polybases," compounds that expand when transported into environments mimicking tumor cells, which have a higher acidity than surrounding tissues. The researchers used sophisticated modeling to show how the particles would accumulate in regions of higher acidity and remain there long enough to delivery anticancer drugs.

"This phenomenon, which we term pH phoresis, may provide a useful mechanism for improving the delivery of drugs to cancer cells in solid tumor tissues," said You-Yeon Won, an associate professor of chemical engineering at Purue University.

Solutions with a pH less than 7 are said to be acidic, and those with a higher pH are basic or alkaline. The pH phoresis concept hinges on using synthetic "polymer micelles," tiny drug-delivery spheres that harbor medications in their inner core and contain an outer shell made of a material that has been shown to expand dramatically as the pH changes from alkaline to acidic.

A twofold size increase could result in a similar increase in the efficiency of drug delivery to tumors.

"Such an effect would be a game changer by delivering the proper dose of anticancer drugs inside tumor cells," Won said. "This pH phoresis concept also could be combined readily within other established drug-delivery methodologies, making it potentially practical for medical application."

The concept is described in a research paper that will appear in the Journal of Controlled Release on July 15, and an unedited version appeared online June 19. The paper was written by Won and doctoral student Hoyoung Lee. Findings showed how the micelles' expansion is optimized in the specific pH in tumor cells.

The researchers demonstrated that the highest degree of micelle swelling in tumors needs to occur when there is a pH of about 7.0, plus or minus 0.5, for optimal delivery of drugs to tumor tissue.

"Solid tumors have a significantly lower extracellular pH, about 6.5-6.9, compared to normal tissue, which has an average pH of 7.4," Won said.

The weak polybases in the micelles contain molecules called amines, which are made of nitrogen and hydrogen atoms. The micelles swell at lower pH due to the increased "protonation," or the addition of protons to nitrogen atoms in the amines. Because the protons are positively charged, the like-charged amines repel each other, causing the nanoparticles to expand.

The positive charge slows the movement of micelles out of tumor tissue, which would cause the nanoparticles to accumulate inside the tumor mass long enough to enter tumor cells and release anticancer drugs.

"This concept is straightforward to understand, yet no one recognized it previously," Won said. "And it took us a while to put this description on a mathematical footing. To do that, we had to modify the famous Fick's first law diffusion equation."

The law, derived by physician and physiologist Adolf Fick in 1855, describes how molecules diffuse from regions of high concentration to regions of low concentration.

The micelles also are coated with protective varnish so that they might remain intact long enough to reach tumor sites, where they would expand and then biodegrade.

More research is needed to determine how well the approach could enhance drug delivery, but the pH phoresis concept developed by Won and his student represents a step in developing nanomedicine techniques in drug delivery, he said.


Contact: Emil Venere
Purdue University

Related biology news :

1. Heart-powered pacemaker could one day eliminate battery-replacement surgery
2. New test could help track down and prosecute terrorists
3. New antibiotic could make food safer and cows healthier
4. BPA could affect reproductive capabilities, cause infection of the uterus
5. Key to immune system disease could lie inside the cheek
6. New analysis of premature infants heartbeats, breathing could be cues for leaving NICU
7. Tiny electrical sensors could signal faster MRSA diagnosis
8. Corals could survive a more acidic ocean
9. Early warning system for seizures could cut false alarms
10. Rapid method of assembling new gene-editing tool could revolutionize genetic research
11. 800-year-old farmers could teach us how to protect the Amazon
Post Your Comments:
(Date:10/5/2015)... ) releases ... (NASDAQ: NXTD ), a biometric authentication company focused ... ) releases the following market and ... a biometric authentication company focused on the growing mobile ... ) releases the following market and ...
(Date:9/30/2015)... Calif. , Sept. 30, 2015  With nearly ... the number of new SCIs estimated to reach 12,500 ... Southern California Resource Services for Independent Living ... ILCs in California opening doors ... range of programs and services, notably assistive technology services ...
(Date:9/29/2015)... Calif. , Sept. 29, 2015 ... improves employee productivity while also saving energy , ... such as Low Power Active Mode and embedded Fujitsu ... transformation Fujitsu today shows that good ... new and refreshed models to its enterprise desktop and ...
Breaking Biology News(10 mins):
(Date:10/12/2015)... 2015  MiMedx Group, Inc. (NASDAQ: MDXG ), ... and patent-protected processes to develop and market advanced products ... Sports Medicine, Ophthalmic, and the Dental sectors of healthcare, ... filed against the Company has been dismissed by the ... and CEO, stated, "As we suspected, this case was ...
(Date:10/12/2015)... , Oct. 12, 2015  Rebiotix Inc. ... (FDA) has designated its lead Microbiota Restoration Therapy ... treatment of recurrent Clostridium difficile (C ... infection that causes 29,000 deaths in the U.S. ... biotechnology company that was founded to revolutionize the ...
(Date:10/12/2015)... ANNAPOLIS, Maryland , 12 de octubre de 2015 ... O. Matsui (D-CA) llegó a un récord en el ... tercera edición anual de la International Plasma Awareness Week ... octubre. La IPAW está patrocinada por la Plasma ... estando diseñada para: , Aumentar la ...
(Date:10/12/2015)... 2015  Patara Pharma, a clinical-stage biotechnology company ... and conditions, today announced the closing of a ... with the close of its sale of preferred ... Security Agreement with Silicon Valley Bank whereby the ... will use the funds from the financing to ...
Breaking Biology Technology: