Q&A: Meet University of Minnesota’s Nanotech Expert

James Marti, the senior scientist at the Minnesota Nano Center, speaks about some of the small but mighty materials that could lead to big advances in the medtech market.

Kristopher Sturgis

When it comes to the future of medtech, there's no denying that the impact that materials at the micro and nano scale will have on the development and functionality of next-gen devices will be significant. Within the realm of medtech, nanoparticles are expected to impact both the diagnostic and therapeutic side of medicine -- a reality that can open new avenues toward devices that can push diagnostic capabilities to new heights, and create new innovative therapies that can forever improve patient care.

James Marti, PhD, is the senior scientist and outreach coordinator for the Minnesota Nano Center.

James Marti, PhD, senior scientist and outreach coordinator for the Minnesota Nano Center at the University of Minnesota, oversees two laboratories where researchers are exploring a variety of different nanomaterials and the capabilities of next-gen micro and nano materials. Marti will speak at the MD&M Minneapolis conference on "The Micro/Nano Materials Revolution" on Wednesday, Nov. 8.

In this Q&A, Marti previews his MD&M Minneapolis talk by diving into some of the recent developments in micro and nano materials, as well as some of the biomedical applications of nanotechnology, and how these developments will have an impact on many of the medtech devices of the future.

Qmed: What are some of the current major medical technology applications for nanoparticles that are already having a significant impact within the realm of medicine?

Marti: The major medical applications of nanoparticles fall into two groups: diagnostic materials and therapeutic particles. Diagnostic nanoparticles, such gold nanoparticles and quantum dots, are used as imaging agents that offer superior performance over conventional dyes. These imaging nanoparticles are often based on photoluminescence, where the particles embedded in tissues or cells are exposed to a short wavelength ultraviolet light source and then emit in a range of visible wavelengths that can be imaged easily.

The second area, nanoparticle therapies, includes drug delivery by nanocapsules, micelles, and liposomes. These capsules may have their surfaces modified with proteins or other molecules to promote adhesion to a target structure, such as cancerous tissue, which enables them to deliver their payload drug directly to the site of interest. A number of cancer medications employing nanoparticle targeting have been approved for clinical use or are in clinical trials. This approach offers huge benefits in terms of lowering exposure of non-cancerous tissues to the cytotoxic effects of the drug.

A second exciting therapy approach lies in the area of thermal therapies. Here, the nanoparticles consist of solid materials that generate heat under irradiation by long wavelength energy (e.g., radio waves). Adding select molecules to the surfaces of these particles enables targeting them to specific tissues. Once placed, the particle may be irradiated from outside the body, heating them and their immediate environment and destroying the targeted tissue.

Qmed: Considering the future, which applications do you see as the most exciting, or perhaps carry the most potential for impact within the medtech field?

Marti: In the near term, the most impact will be realized from the improved efficacy of nanocapsule drug delivery. We have only begun to tap the potential for delivering therapeutically relevant doses in a completely targeted way. In the near future, we should also expect to see more reliable implantable sensors based on nanofabrication techniques that are able to monitor blood chemistry and other key health parameters.

Looking further into the future, one can envision medical nanoparticles that can function as active nanodevices for tissue repair, cell modification, and infection control, perhaps under the influence of externally applied forces.

Qmed: What will it take to help bring some of these potentialities to fruition, and what are some of the challenges that lie ahead when it comes to finding successful applications?

Marti: There are several challenges facing the use of nanocapsule drugs. The chief obstacle is targeting success. We can coat gold nanoparticles with a protein that should help it bind to the type of cell or tissue that we want a drug delivered to. However, the binding is a stochastic process; as the particles circulate with the blood, only some fraction of the particles makes it to the target. If the particles remain in the bloodstream, they have multiple chances to attach, but our liver is very good at cleansing the blood and removing foreign agents. The means that the drug delivery particles usually have a limited opportunity to attach to their target; most are swept out of the body and excreted before they can perform their mission.

A second problem is payload. Nanocapsules are attractive because their small size helps them to evade the search-and-destroy functions of white blood cells, and enables the particles to more easily pass into cells, especially those of cancerous tissue with its "leaky" vasculature. On the other hand, that same small size limits the amount of active drug that each particle can deliver. Adding more nanocapsules to up the dosage may trigger undesired responses for the body, so doctors and pharmacologists must tread a fine line between giving their patients too little drug to be effective and too much nanomaterial which may trigger reactions.

What will it take to improve these therapies? Continued research into materials and encapsulation processes to a) increase drug payloads and b) improve capsule targeting success and/or persistence in the bloodstream. Continued clinical experience should also help this area advance.

Qmed: As nanotechnologies become more ubiquitous, what do you think will be needed for medical device manufacturers to get more involved? Will they need new equipment, facilities, or new specific expertise?

Marti: Many drug manufacturers already work in the area of applied particle processing. They have a great deal of experience working with micron-sized powders, and many are already working with preparing nanoparticle dispersions of many types. For those companies entering the field, the extension to nanomaterials will require an extension of larger-particle capabilities, and in some cases, new tools and new hires.

Qmed: What are some of the materials that will see an increase in demand and/or use when it comes to innovative new devices made from nanotechnologies?

Marti: Nanoparticles used as drug vectors must be biocompatible, so particles consisting of gold and silicon dioxide have been heavily used up to this point, and there is every reason to think that will continue to grow.

Nanocapsules for drug delivery will continue to focus on the use of surfactants and how their structure affects the formation of micelles (having a single-layer shell) and liposomes (which have a double layer as a shell). 

For diagnostic imaging, quantum dots (luminescent nanoparticles) consisting of cadmium sulfide and cadmium selenide have been widely used. While these particles are generally stable, the use of toxic heavy metals like cadmium gives many clinicians pause, so there is a great deal of interest in finding alternatives to cadmium-based quantum dots. Silicon quantum dots have been found to be promising in the lab, but challenges remain before they can be introduced as a viable product.

Qmed: As an expert in the field, you must get a lot of questions about your work. What is one common myth or widely misunderstood concept about nanotechnology for biomedical applications that you think could use more clarity?

Marti: If you ask people to give an example of nanotechnology, many will respond "nanobots," nanometer-sized autonomous machines supposedly capable of all kinds of nefarious activity. Science fiction movies and books have convinced many people that these nanomachines are a reality and that in their more benign forms, they are being used to perform microsurgeries. While that day may come, we are a long way away from anything that capable or smart.

Qmed: Which devices do you think will see the most improvement from nanotechnologies, and similarly, which area do you think will see the biggest impact between imaging, diagnostics, and drug delivery?

Marti: I look to advances in nanofabrication to produce compact, self-powered implantable sensors to analyze a patient's blood chemistry and other biomarkers, and then report out the data to an external data logger. From there, we could add automated drug delivery in response to the measured biomarkers while continuously monitoring the patient.  

We will probably see incremental improvements in nanoparticle-based imaging and diagnostics, but the real room for improvement is in drug delivery. I look to see better drug nanocapsule targeting and a greater range of drug doses that are deliverable.

Qmed: Finally, what are some of the trends that stick out to you when you look at how nanomaterials and technologies will shape the future of biomedical devices and technologies?

Marti: Biomedical technologies encompass devices (both external and implantable) as well as nanoparticle-based therapies, and there are promising trends in both areas. The advances in nanometer-scale integrated circuits should continue to be translated into biodevices, especially biosensors. The need for improvements in drug delivery should drive continued exploration of new nanocapsule materials and production methods.

James Marti, PhD, will talk about nanomaterials during MD&M Minneapolis, which will be held Nov. 8-9, 2017.

Kristopher Sturgis is a contributor to Qmed. 

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