Nanoscale tech for better drug delivery

The development of medicine throughout the 20th century has led to astounding outcomes around the world. Today, people are healthier, longer living and less likely to die of cancer or infectious disease. Vaccines, antibiotics and other advances in healthcare have all contributed to better health for us all. Yet, even today, many diseases and cancers are untreatable and treatments simply don’t exist or appropriate drugs produce side effects too severe to be useful.

But what if doctors could tailor drugs to specific targets? What if they could treat only the cancer cells, or deliver a vaccine directly to immune cells, without affecting any other cells along the way? By delivering a drug directly to the cells of choice, side effects caused by interactions with other cells could be minimised and the efficacy of the drug increased.

Professor Frank Caruso leads a research group at the University of Melbourne which is taking steps along the path toward targeted drug delivery by engineering nanoparticles.

“Using cutting-edge assembly strategies, we can engineer nanoparticles to carefully control their size, shape and other structural properties,” Professor Caruso says. “This allows us to tailor the encapsulation and release of therapeutics.”

Yet developing smart drug carriers, with the ability to avoid healthy cells and target only diseased or cancerous cells directly, requires a detailed understanding of cellular processes at the molecular level. 

Cutting-edge science requires cutting-edge instrumentation. Professor Caruso and his team are using advanced super-resolution microscopy techniques to investigate the interactions between cells and engineered nanoparticles at the nanoscale.

“For decades, conventional microscopes have been limited by a perceived limit, the Abbe diffraction limit. We couldn’t resolve particles smaller than 250 nanometres. Now, using super-resolution, we can break that limit and achieve a maximum resolution of 20 nanometres,” he says. “That’s the width of only 10 DNA molecules laid side by side.” 

For reference, bacteria are generally one to two microns in size – that’s 1000 to 2000 nanometres. While other imaging techniques such as electron microscopy can have even higher possible resolutions, the processing involved can damage delicate samples and are suitable only for a narrow range of applications.

Excitingly, the Nobel Prize in Chemistry 2014 was awarded for the development of super-resolution microscopy. One of the microscopes used by Professor Caruso’s group, the Nikon N-STORM system, relies on technologies developed by the three awardees. This instrument has the ability to image single fluorescent molecules and accurately plot their location on the nanoscale. Cleverly, rather than imaging all of the molecules at once, which may overlap and prevent them being positioned accurately, the machine images only a subset of the molecules at a time. By blinking individual molecules on and off and imaging the area each time, a molecule map of all the fluorescent molecules present over time can be calculated. 

Dr Jiwei Cui is a member of Professor Caruso’s group using the Nikon N-STORM system to develop innovative new nanoparticles for drug delivery.

“Particles smaller than 100 nanometres in diameter play a vital role for improved drug delivery, since larger particles are more easily trapped in body organs or removed by the immune system,” he says. 

“However, to investigate the bio-nano interaction in situ, conventional microscopes are limited due to the resolution issue. Fortunately, the N-STORM system can track the bio-nano interactions in much greater detail, meaning we can use the system to characterise our polymer hydrogel particles in cells.”

The Nikon N-STORM system is powerful and sensitive, yet a super-resolution image of a single cell can take up to an hour to acquire. 

Professor Caruso’s group therefore also uses another, faster, super-resolution microscope, the Applied Precision OMX V4 Blaze. This microscope uses a structured illumination technique, carefully shaping a pattern of light to overlay the sample being imaged. By shifting the pattern through a series of orientations and angles, then processing the images through software, the super-resolution image can be obtained at a resolution of 100 nanometres across four different colour channels. A three dimensional, super-resolution image of an entire cell can be obtained in under a minute.

Dr Yan Yan is an Australian Research Council fellow with the group, researching the biological interactions between cells and nanoparticles, who says that with resolution of the OMX down to 100 nanometres, scientists can start to explore how to visualise individual nanoparticles and how they interact with live cells.

“This allows us to gain entirely new levels of information regarding the cellular machineries,” she says.

Professor Caruso’s group is just one of many accessing the super-resolution microscopes. Access is provided through the Materials Characterisation and Fabrication Platform (MCFP) at the University of Melbourne and the facility is open to all researchers, be they from academic institutes or industry. Dr Yan is also the academic leader for the Advanced Fluorescence Imaging node of the MCFP.

“We provide access to not only the super-resolution microscopes, but also a wide range of other fluorescence-based instruments, such as conventional microscopes and flow cytometers. With our instruments, we can look at either a single cell in super-resolution or at thousands of cells at a time to get an idea of the overview of a cellular population.”

Professor Caruso is excited by the future of microscopy and the benefits it brings to his research. “Super-resolution microscopy offers new and exciting opportunities to study the interactions between engineered particles and cells,” he says. “Cutting edge instrumentation is critical in developing the next generation of drug and vaccine carriers.”

www.chemeng.unimelb.edu.au