Our researchers should look into this possibility for delivering tPA. I'm sure a much smaller and less dangerous bolus might be able to be delivered this way. Maybe way past the 4.5 hour current timeframe. But this is a BHAG(Big Hairy Audacious Goal) that will never be attempted because we don't have persons willing to take risks.
http://www.alphagalileo.org/ViewItem.aspx?ItemId=163208&CultureCode=en
Using ultrasound, drug particles can be directed to a specific area
Scientists at Nanyang Technological University (NTU Singapore) have
invented a new way to deliver cancer drugs deep into tumour cells.
The NTU scientists create micro-sized gas bubbles coated with cancer
drug particles and iron oxide nanoparticles, and then use magnets to
direct these bubbles to gather around a specific tumour.
Ultrasound is then used to vibrate the microbubbles, providing the energy to direct the drug particles into a targeted area.
This innovative technique was developed by a multidisciplinary team
of scientists, led by Asst Prof Xu Chenjiefrom the School of Chemical
and Biomedical Engineering and Assoc Prof Claus-Dieter Ohl from the
School of Physical and Mathematical Sciences.
NTU’s microbubbles were successfully tested in mice and the study has
been published by the Nature Publishing Group in Asia Materials, the
top journal for materials sciences in the Asia-Pacific region.
Overcoming limitations of chemotherapy
Asst Prof Xu, who is also a researcher at the NTU-Northwestern
Institute for Nanomedicine, said their new method may solve some of the
most pressing problems faced in chemotherapy used to treat cancer.
The main issue is that current chemotherapy drugs are largely
non-targeted. The drug particles flow in the bloodstream, damaging both
healthy and cancerous cells. Typically, these drugs are flushed away
quickly in organs such as the lungs and liver, limiting their
effectiveness.
The remaining drugs are also unable to penetrate deep into the core
of the tumour, leaving some cancer cells alive, which could lead to a
resurgence in tumour growth.
“The first unique characteristic of our microbubbles is that they are
magnetic. After injecting them into the bloodstream, we are able to
gather them around the tumour using magnets and ensure that they don’t
kill the healthy cells,” explains Asst Prof Xu, who has been working on
cancer diagnosis and drug delivery systems since 2004.
“More importantly, our invention is the first of its kind that allows
drug particles to be directed deep into a tumour in a few milliseconds.
They can penetrate a depth of 50 cell layers or more – which is about
200 micrometres, twice the width of a human hair. This helps to ensure
that the drugs can reach the cancer cells on the surface and also inside
the core of the tumour.”
Clinical Associate Professor Chia Sing Joo, a Senior Consultant at
the Tan Tock Seng Hospital’s Endoscopy Centre and the Urology &
Continence Clinic, was one of the consultants for this study.
A trained robotic surgeon experienced in the treatment of prostate,
bladder and kidney cancer, Assoc Prof Chia said, “For anticancer drugs
to achieve their best effectiveness, they need to penetrate into the
tumour efficiently in order to reach the cystoplasm of all the cancer
cells that are being targeted without affecting the normal cells.
“Currently, these can be achieved by means of a direct injection into
the tumour or by administering a large dosage of anticancer drugs,
which can be painful, expensive, impractical and might have various side
effects.”
The specialist in Uro-oncology added that if NTU’s technology proves
to be viable, clinicians might be able to localise and concentrate the
anticancer drugs around a tumour, and introduce the drugs deep into
tumour tissues in just a few seconds using a clinical ultrasound system.
“If successful, I envisage it can be a good alternative treatment in
the future, one which is low cost and yet effective for the treatment of
cancers involving solid tumours, as it might minimise the side effects
of drugs.”
New drug delivery system
The motivation for this research project is to find alternative
solutions for drug delivery systems that are non-invasive and safe.
Ultrasound uses soundwaves with frequencies higher than those heard
by the human ear. It is commonly used for medical imaging such as to get
diagnostic images.
Magnets, which can draw and attract the microbubbles, are already in
use in diagnostic machines such the Magnetic Resonance Imaging (MRI).
“We are looking at developing novel drug carriers – essentially
better ways of delivering drugs with minimum side effects,” explained
Prof Ohl, an expert in biophysics who had published previous studies
involving drug delivery systems and bubble dynamics.
“Most prototype drug delivery systems on the market face three main
challenges before they can be commercially successful: they have to be
non-invasive, patient-friendly and yet cost-effective.
“Using the theory of microbubbles and how their surface vibrates
under ultrasound, we were able to come up with our solution that
addresses these three challenges.”
Interdisciplinary team
This study, which took two and a half years, involved a 12-man
international interdisciplinary team consisting of NTU scientists as
well as scientists from City University of Hong Kong and Tel Aviv
University in Israel. Two NTU undergraduates doing their Final Year
Project and one student in Summer Research Internship Programme (NTU)
were also part of the team.
Moving forward, the team will be adopting this new drug delivery
system in studies on lung and liver cancer using animal models, and
eventually clinical studies.
They estimate that it will take another eight to ten years before it reaches human clinical trials.
http://media.ntu.edu.sg/NewsReleases/Pages/newsdetail.aspx?news=581d56b4-84d3-46a9-a155-3a68431d615d
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