Theranostic medicine is based on the concept of delivering both therapeutic and imaging agents to the same targeted location in the body, using a single delivery platform enabled by nanotechnology. These nanosystems can improve drug delivery and diagnosis, and also monitor therapeutic responses to medication. These capabilities will play an important role in the progress of personalized medicine.
Quantum dots, iron oxide nanoparticles, carbon nanotubes, gold and silica nanoparticles have all been studied in biological imaging techniques. they are usually used to enhance the resolution and contrast from existing techniques such as fluorescence microscopy and MRI scans.
Nanostructures like these have unique and often highly tuneable surface chemistry, which allows them to be designed so that pharmaceutical agents can be attached and prevented from acting until they reach the target location. Combining nanoparticle drug delivery systems with nano-enhanced imaging techniques results in theranostic treatments.
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Nanoparticles can be designed for enhanced biological imaging, and can deliver cancer drugs to targeted locations within the body. The combination of these two functionalities into a single platform has been dubbed "theranostics" - a combination of therapy and diagnostics. Image Credits: Photos.com
Nanoparticles for Pancreatic Cancer
Pancreatic cancer is one of the most difficult types of cancer to treat, because advanced-stage patients often do not respond to presently available radiotherapies and chemotherapy.
As part of a partnership with the National Cancer Institute's Alliance for Nanotechnology in Cancer, researchers at Emory University are attempting to develop a multifunctional theranostic nanoparticle platform that combines the receptor specificity and imaging capability of the nanoparticles with innovative drug delivery systems targeted at specific tumors.
This drug delivery platform leverages the unique pharmokinetic properties and surface functions of magnetic iron oxide nanoparticles, and offers a solution for overcoming intrinsic and physical barriers that cause drug resistance in pancreatic cancer.
Doctors Mao and Yang led the research team, which aims to develop the magnetic iron oxide nanoparticle (IONP) based nanoconstructs targeted to cellular receptors, such as the urokinase plasminogen activator receptor (uPAR). These nanoconstructs enable penetration of drug-carrying nanoparticles into the endothelial cell layer of the tumor, destruction of tumor stromal fibroblasts, and also enhance intracellular drug delivery by receptor-mediated endocytosis.
The research team are also working on methods and strategies for controlled release and loading of multiple or single therapeutic agents such as small molecules, chemotherapy drugs and siRNA-expressing DNA cassettes, into the pancreatic cancer cells.
Nanoparticles for Breast Cancer
Swedish scientists published research in Particle & Particle Systems Characterization in February 2013, which shows how nanoparticles can be used for effective delivery of cancer drugs to tumor cells, and how they can be given properties to make them easily trackable using an MRI scanner.
The research team included scientists from the Royal Institute of Technology (KTH) in Stockholm, Karolinska Institutet (KI) and from Chalmers University of Technology in Gothenburg. They succeeded in developing theranostic nanoparticles which combine diagnostic and therapeutic functionalitites in the same material.
The study targeted breast cancer cells, aiming to deliver a targeted chemotherapy drug payload. The nanoparticles were designed to collect and concentrate in and around the cancer cells specifically, minimizing the amount of the damaging drug released in healthy parts of the body.
This ability to target cancer cells can also be used diagnostically - the nanoparticles can be detected in an MRI scan, indicating the location and size of any tumours.
The researchers also made sure that the nanoparticles themselves were not harmful - the building blocks used to create them are biodegradable, and non-toxic, so use of this technique does not introduce any additional risk to the patient.
The theranostic nanoparticles were created by self-assembly of tailored polymer macromolecules, with a balanced combination of hydrophobic and hydrophilic components. The hydrophobic components enable the particles to be filled with the drug.
The nanoparticles also contained fluorine markers - the naturally occurring isotope 19F makes the particles clearly visible in high-resolution MR tomograms, allowing tracking of the theranostic particles through the body. This helps researchers to study how the tumor has taken up the drug and how effective the treatment is.
Conclusion
Theranostic nanoparticles are now being developed which can be used as delivery vehicles for both imaging agents and drugs. Materials which are of interest in this field include iron oxide nanoparticles, gold nanoparticles, and quantum dots.
The advent of theranostics marks an important milestone in the development of cancer treatments. The ability to track chemotherapy drugs as they move through the body, as well as simultaneuously targeting them at cancer cells, will improve the efficacy of the drugs, reduce side effects, and provide valuable data for development of new drugs.
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