Overcoming drug delivery barriers

Editor’s Note: The following is a summary of one of the talks from the 2013 Nano-bio Symposium hosted by Johns Hopkins Institute for NanoBioTechnology held May 17. This summary was written by Randall Meyer, a doctoral candidate in the biomedical engineering and a member of the Cancer Nanotechnology Training Center. Look for other symposium summaries on the INBT blog.

Nanotechnology bears a multitude of possibilities to systematically and specifically treat many well-characterized and currently untreatable diseases.  Despite this, there exist multiple barriers to its development including challenges related to delivery in the human body.

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Justin Hanes, a professor of Chemical and Biomolecular Engineering at Johns Hopkins University, highlighted some of the exciting advances that his laboratory has developed to overcoming these challenges.  According to Hanes, one of the primary functions of nanobiotechnology is to enable a therapy to be delivered to a specific location and only remain there for as long as it is needed.  He likened this idea to applying weed poison to a rose garden.  You only want to apply a little bit of poison to a targeted area, not flood the whole garden.  Unfortunately conventional cancer chemotherapy is like flooding the garden, but only 1 percent of the drug reaches the tumor.  Hanes stated the goal of his work is to flip that so that all but 1 percent of the drug makes it to the site of delivery.

With that in mind, Hanes summarized two stories from his lab of ideas that are successfully being translated from bench to bedside.  One therapy involves the use of custom designed nanoparticles that are capable of penetrating the mucus layers of various human tissues to enable a controlled release of drug into the body.  The second therapy involves the use of injectable particles to the eye that inhibit blood vessel formation,  which is related to diseases such as macular degeneration.

These therapies are being developed by biotech companies launched by Hanes, GrayBug and Kala Pharmaceuticals.

Coated nanoparticles move easily into brain tissue

Real-time imaging of nanoparticles green) coated with polyethylene-glycol (PEG), a hydrophilic, non-toxic polymer, penetrate within normal rodent brain. Without the PEG coating, negatively charged, hydrophobic particles (red) of a similar size do not penetrate. Image by Elizabeth Nance, Kurt Sailor, Graeme Woodworth.

Johns Hopkins researchers report they are one step closer to having a drug-delivery system flexible enough to overcome some key challenges posed by brain cancer and perhaps other maladies affecting that organ. In a report published online Aug. 29 in Science Translational Medicine, the Johns Hopkins team says its bioengineers have designed nanoparticles that can safely and predictably infiltrate deep into the brain when tested in rodent and human tissue.

“We are pleased to have found a way to prevent drug-embedded particles from sticking to their surroundings so that they can spread once they are in the brain,” said Justin Hanes, Lewis J. Ort Professor of Ophthalmology and project leader in the Johns Hopkins Center of Cancer Nanotechnology Excellence.

Standard protocols following the removal of brain tumors include chemotherapy directly applied to the surgical site to kill any cancer cells left behind. This method, however, is only partially effective because it is hard to administer a dose of chemotherapy high enough to sufficiently penetrate the tissue to be effective and low enough to be safe for the patient and healthy tissue. Furthermore, previous versions of drug-loaded nanoparticles typically adhere to the surgical site and do not penetrate into the tissue.

These newly engineered nanoparticles overcome this challenge. Elizabeth Nance, a graduate student in chemical and biomolecular engineering, and Johns Hopkins neurosurgeon Graeme Woodworth, suspected that drug penetration might be improved if drug-delivery nanoparticles interacted minimally with their surroundings. Nance achieved this by coating nano-scale beads with a dense layer of PEG or poly(ethylene glycol). The team then injected the coated beads, which had been marked with a fluorescent tag,  into slices of rodent and human brain tissue. They found that a dense coating of PEG allowed larger beads to penetrate the tissue, even those beads that were nearly twice the size previously thought to be the maximum possible for penetration within the brain. They then tested these beads in live rodent brains and found the same results.

Elizabeth Nance. Photo by Ming Yang.

The results were similar when biodegradable nanoparticles carrying the chemotherapy drug paclitaxel and coated with PEG were used. “It’s really exciting that we now have particles that can carry five times more drug, release it for three times as long and penetrate farther into the brain than before,” said Nance. “The next step is to see if we can slow tumor growth or recurrence in rodents.”

Woodworth added that the team “also wants to optimize the particles and pair them with drugs to treat other brain diseases, like multiple sclerosis, stroke, traumatic brain injury, Alzheimer’s and Parkinson’s.” Another goal for the team is to be able to administer their nanoparticles intravenously, which is research they have already begun.

Additional authors on the paper include Kurt Sailor, Ting-Yu Shih, Qingguo Xu, Ganesh Swaminathan, Dennis Xiang, and Charles Eberhart, all from The Johns Hopkins University.

Story adapted from an original press release by Cathy Kolf.

 

Additional news coverage of this research can be found at the following links:

Nanotechnology/Bio & Medicine

Death and Taxes Mag

New Scientist Health

Nanotech Web

Portugese news release (in Portugese)

German Public Radio (in German)

Nanoparticles slip through mucus barrier to protect against herpes virus

“Thick, sticky mucus layers limit effectiveness of drug delivery to mucosal tissues. Mucus-penetrating particles or MPPs (in red) are able to penetrate mucus, covering the entire surface of the mouse vagina (in blue). Improved distribution and retention of MPPs led to significantly increased protection in a mouse model for herpes simplex virus infection. Image by Laura Ensign.

Johns Hopkins researchers say they have demonstrated for the first time, in animals, that nanoparticles can slip through mucus to deliver drugs directly to tissue surfaces in need of protection.

The researchers used these mucus-penetrating particles, or MPPs, to protect against vaginal herpes infections in mice. The goal is to create similar MPPs to deliver drugs that protect humans against sexually transmitted diseases or even treat cancer.

“This is the first in vivo proof that MPPs can improve distribution, retention, and protection by a drug applied to a mucosal surface, said Justin Hanes, Ph.D., a professor of ophthalmology at the Johns Hopkins Wilmer Eye Institute and director of the Center for Nanomedicine at the Johns Hopkins University School of Medicine.

Hanes also is a principal investigator with the Johns Hopkins Center of Cancer Nanotechnology Excellence. Results of his team’s experiments are described in the June 13 issue of the journal Science Translational Medicine.

The moist mucosal surfaces of the body, like the eyes, lungs, intestines and genital tract, are protected from pathogens and toxins by layers of moist sticky mucus that is constantly secreted and shed, forming our outermost protective barrier.

“Although many people associate mucus with disgusting cold and cough symptoms, mucus is in fact a sticky barrier that helps keep you healthy,” says Laura Ensign, a doctoral student affiliated with the Center for Nanomedicine at the School of Medicine and with the Department of Chemical and Biomolecular Engineering at Johns Hopkins’ Whiting School of Engineering. She is the lead author of the journal report.

Unfortunately, Ensign noted, mucus barriers also stop helpful drug delivery, especially conventional nanoparticles intended for sustained drug delivery. In a Johns Hopkins laboratory, researchers developed nanoparticles that do not stick to mucus so they can slip through to reach the cells on the mucosal surface, in this case the surface of the mouse vagina, she added.

Ensign explained that conventional nanoparticles actually stick to mucus before releasing their drug payload and are then removed when the mucus is replenished, often within minutes to hours. Working with researchers in the laboratory of Richard Cone, Ph.D., in the Department of Biophysics in the university’s Krieger School of Arts and Sciences, the Hanes team fabricated particles with surface chemistry that mimics a key feature of viruses that readily infect mucosal surfaces.

“Richard Cone’s lab found that viruses, such as the human papilloma virus, could diffuse through human cervical mucus as fast as they diffuse through water. These ‘slippery viruses’ have surfaces that are ‘water-loving,’ ” Hanes said. “In contrast, many nanoparticles intended to deliver drugs to mucosal surfaces are ‘mucoadhesive’ and ‘oil-loving,’ but these nanoparticles stick to the superficial layers of the mucus barrier, the layers that are most rapidly removed.”

To make their mucus-penetrating particles, the team transformed conventional ‘oil-loving’ nanoparticles by coating them with a substance used in many commercial pharmaceutical products: polyethylene glycol. PEG makes the particles “water-loving,” like the viruses that slip right through mucus.

“The key is that the nanoparticles, like viruses, have to be small enough to go through the openings in the mucus mesh, and also have surfaces that mucus can’t stick to. If you think about it,” said Ensign, “mucus sticks to almost everything.”

“Viruses have evolved over millions of years to become slippery pathogens that readily penetrate our protective mucus barriers,” said Cone, “and engineering nanoparticles that penetrate the mucus barrier just like viruses is proving to be a clever way to deliver drugs.”

Hanes emphasized that the MPPs provided greatly improved protective efficacy while at the same time reducing the effective dose of drug needed 10-fold. Furthermore, Hanes added, the MPPs “continue to supply drug for at least a day and provide nearly 100 percent coverage of the mucosal surface of the vagina and ectocervix” in their laboratory mice.

“We’ve shown that mucus-penetrating particles are safe for vaginal administration in mice. Our next move will be to show that they are safe for vaginal administration in humans,” Ensign said. “Now our laboratory currently is working on an MPP formulation of a drug that protects against HIV infection that we hope will be tested in humans.”

Their technology could lead to a once-daily treatment for preventing sexually transmitted diseases, for contraception and for treatment of cervico-vaginal disorders, Ensign said.

Ensign added that MPP technology has the potential to prevent a wide range of mucosal diseases and infections, including chronic obstructive pulmonary disease, lung cancer, and cystic fibrosis,” Ensign said.

Additional authors on the paper include postdoctoral fellow Ying-Ying Wang and research specialist Timothy Hoen from the Department of Biophysics; former master’s student Terence Tse from the Department of Chemical and Biomolecular Engineering; and Benjamin Tang, formerly of Johns Hopkins School of Medicine and currently at the Massachusetts Institute of Technology.

Under a licensing agreement between Kala Pharmaceuticals and the Johns Hopkins University, Hanes is entitled to a share of royalties received by the university on sales of products used in the study.

Hanes and the university own Kala Pharmaceuticals stock, which is subject to certain restrictions under university policy. Hanes is also a founder, a director and a paid consultant to Kala Pharmaceuticals. The terms of this arrangement are being managed by The Johns Hopkins University in accordance with its conflict of interest policies.”

Story by Mary Spiro

Additional news coverage of this research may be found at the following links:

Phys.org

WYPR: The Mucus Ruse

Scientific American

 

Biodegradable nanoparticles ideal carrier for drug delivery

Johns Hopkins University researchers have created biodegradable nanosized particles that can easily slip through the body’s sticky and viscous mucus secretions to deliver a sustained-release medication cargo. The researchers say that these nanoparticles, which degrade over time into harmless components, could one day carry life-saving drugs to patients suffering from dozens of health conditions, including diseases of the eye, lung, gut or female reproductive tract.

The mucus-penetrating biodegradable nanoparticles were developed by an interdisciplinary team led by Justin Hanes, a professor of chemical and biomolecular engineering in Johns Hopkins’ Whiting School of Engineering*. The team’s work was reported recently in the Proceedings of the National Academy of Sciences. Hanes’ collaborators included cystic fibrosis expert Pamela Zeitlin, a professor of pediatrics at the Johns Hopkins School of Medicine and director of Pediatric Pulmonary Medicine at Johns Hopkins Children’s Center.

Individual biodegradable nanoparticle developed by the Justin Hanes Lab at Johns Hopkins University (shown here at microscale for easier imaging) displaying polymer coating as a red fluorescent glow. Hanes' biodegradable nanoparticles have the ability to penetrate mucus barriers in the body to deliver drugs. (Photo by Jie Fu/JHU)

Individual biodegradable nanoparticle developed by the Justin Hanes Lab at Johns Hopkins University (shown here at microscale for easier imaging) displaying polymer coating as a red fluorescent glow. Hanes’ biodegradable nanoparticles have the ability to penetrate mucus barriers in the body to deliver drugs. (Photo by Jie Fu/JHU)

These nanoparticles, Zeitlin said, could be an ideal means of delivering drugs to people with cystic fibrosis, a disease that kills children and adults by altering the mucus barriers in the lung and gut. “Cystic fibrosis mucus is notoriously thick and sticky and represents a huge barrier to aerosolized drug delivery,” she said. “In our study, the nanoparticles were engineered to travel through cystic fibrosis mucus at a much greater velocity than ever before, thereby improving drug delivery. This work is critically important to moving forward with the next generation of small molecule– and gene-based therapies.”

Beyond their potential applications for cystic fibrosis patients, the nanoparticles also could be used to help treat disorders such as lung and cervical cancer and inflammation of the sinuses, eyes, lungs and gastrointestinal tract, said Benjamin C. Tang, lead author of the journal article and a postdoctoral fellow in the Department of Chemical and Biomolecular Engineering. “Chemotherapy is typically given to the whole body and has many undesired side effects,” he said. “If drugs are encapsulated in these nanoparticles and inhaled directly into the lungs of lung cancer patients, drugs may reach lung tumors more effectively and improved outcomes may be achieved, especially for patients diagnosed with early stage non–small cell lung cancer.”

“If drugs are encapsulated in these nanoparticles and inhaled directly into the lungs of lung cancer patients, drugs may reach lung tumors more effectively and improved outcomes may be achieved, especially for patients diagnosed with early stage non–small cell lung cancer.” ~ Ben Tang

In the lungs, eyes, gastrointestinal tract and other areas, the human body produces layers of mucus to protect sensitive tissue. But an undesirable side effect is that these mucus barriers can also keep helpful medications away.

In proof-of-concept experiments, previous research teams led by Hanes earlier demonstrated that latex particles coated with polyethylene glycol could slip past mucus coatings. But latex particles are not a practical material for delivering medication to human patients because they are not broken down by the body. In the new study, the researchers described how they took an important step forward in making new particles that biodegrade into harmless components while delivering their drug payload over time.

“The major advance here is that we were able to make biodegradable nanoparticles that can rapidly penetrate thick and sticky mucus secretions, and that these particles can transport a wide range of therapeutic molecules, from small molecules such as chemotherapeutics and steroids to macromolecules such as proteins and nucleic acids,” Hanes said. “Previously, we could not get these kinds of sustained-release treatments through the body’s sticky mucus layers effectively.”

The new biodegradable particles comprise two parts made of molecules routinely used in existing medications. An inner core, composed largely of polysebacic acid, or PSA, traps therapeutic agents inside. A particularly dense outer coating of polyethylene glycol, or PEG, molecules, which are linked to PSA, allows a particle to move through mucus nearly as easily as if it were moving through water and also permits the drug to remain in contact with affected tissues for an extended period of time.

In Hanes’ previous studies with mucus-penetrating particles, latex particles could be effectively coated with PEG but could not release drugs or biodegrade. Unlike latex, however, PSA can degrade into naturally occurring molecules that are broken down and flushed away by the body through the kidney, for example. As the particles break down, the drugs loaded inside are released.

This property of PSA enables the sustained release of drugs, said Samuel Lai, assistant research professor in the Department of Chemical and Biomolecular Engineering, while designing them for mucus penetration allows them to more readily reach inaccessible tissues.

Biodegradable nanoparticles produced by the Justin Hanes Lab at Johns Hopkins University visualized under a scanning electron microscope. (Photo by Ben Tang and Mark Koontz/JHU)

Biodegradable nanoparticles produced by the Justin Hanes Lab at Johns Hopkins University visualized under a scanning electron microscope. (Photo by Ben Tang and Mark Koontz/JHU)

Jie Fu, an assistant research professor, also from the Department of Chemical and Biomolecular Engineering, said, “As it degrades, the PSA comes off along with the drug over a controlled amount of time that can reach days to weeks.”

PEG acts as a shield to protect the particles from interacting with proteins in mucus that would cause them to be cleared before releasing their contents. In a related research report, the group showed that the particles can efficiently encapsulate several chemotherapeutics, and that a single dose of drug-loaded particles was able to limit tumor growth in a mouse model of lung cancer for up to 20 days.

Hanes, Zeitlin, Lai and Fu are all affiliated with the Johns Hopkins Institute for NanoBioTechnology. Other authors on the paper are Ying-Ying Wang, Jung Soo Suk and Ming Yang, doctoral students in the Johns Hopkins Department of Biomedical Engineering; Michael P. Boyle, an associate professor in Pulmonary and Critical Care Medicine at the Johns Hopkins School of Medicine; and Michelle Dawson, an assistant professor at the Georgia Institute of Technology.

This work was supported in part by funding from the National Institutes of Health, a National Center for Research Resources Clinical and Translational Science Award, the Cystic Fibrosis Foundation, the National Science Foundation and a Croucher Foundation Fellowship.

The technology described in the journal article is protected by patents managed by the Johns Hopkins Technology Transfer Office and is licensed exclusively by Kala Pharmaceuticals. Justin Hanes is a paid consultant to Kala Pharmaceuticals, a startup company in which he holds equity, and is a member of its board. The terms of these arrangements are being managed by The Johns Hopkins University in accordance with its conflict-of-interest policies.

(*At the time that this research was published, Hanes had his primary affiliation with the Whiting School of Engineering Department of Chemical and Biomolecular Engineering. Hanes’ current primary affiliation is with the Johns Hopkins School of Medicine Department of Ophthalmology.)

Related Links

Biodegradable polymer nanoparticles that rapidly penetrate the human mucus barrier. PNAS 2009 106:19268-19273; published online before print November 9, 2009.  [Institutional access required.]

Hanes Lab

Johns Hopkins Children’s Center

Institute for NanoBioTechnology

Story by Mary Spiro and Jacob Koskimaki with materials provided by Johns Hopkins Technology Transfer.

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