The Latest Advances in Nanotechnology at Pittcon
The Pittcon Conference & Expo is the ideal place to learn about the latest trends in nanotechnology and the impacts of nanomaterials. This article outlines the current trends in nanotechnology, characterization, and regulation, which will be discussed at Pittcon.
Nanotechnology at Pittcon
The Pittcon Conference is an ideal place for researchers to learn about the latest trends in nanotechnology and nanomaterial characterization. Pittcon has evolved to encompass all laboratory-based testing and the analysis of chemical/biological properties of compounds or molecules including techniques and applications relevant to the field of nanotechnology.
This year Pittcon will host a symposium dedicated to nanotechnology. This article outlines some of the areas that will be covered.
Nanotechnology has become an increasingly important area of science with many applications.
It is important that global community develop and use nanotechnology responsibly. Chapter 1 of this article covers some of the challenges that the field of nanotechnology faces including evaluating toxicity, measuring exposure to nanomaterials, and regulating nanotechnology.
The applications of nanotechnology are extensive. Some of the most researched include the effects of nanoparticles in biological systems and nanobiotechnology, topics that are further discussed in Chapters 2 and 3, respectively. Each application of nanotechnology requires specific analysis techniques, and the Pittcon nanotechnology symposium will discuss many of the relevant analytical methods including inductively coupled plasma mass spectrometry (ICPMS) and Raman spectroscopy.
Other nanotechnologies more directly utilize analytical and spectroscopy methods. Nanoimaging and nanosensors, which are discussed in Chapters 4 and 5 and will be extensively covered at the Pittcon 2018 nanotechnology symposium, bring the world of analytical chemistry and applied spectroscopy to the nanoscale, and create a new world of possibilities for analytical chemistry.
Chapter 1 – The Challenges Facing Nanotechnology
Scientists around the globe are harnessing the power of nanotechnology to create and modify materials and technologies, producing products and technologies with properties that were not previously possible.
Nanomaterials are already used in over 1300 commercial applications from sunscreen to medicines and food packaging. The power of nanotechnology stems from exotic quantum effects that are present at such a small scale, combined with properties that are not found in large particles due to the increased surface area to volume ratios and increased active surface areas.
However, the same qualities that make nanotechnology so powerful can also create risks to human health and the environment. A major challenge faced by the field of nanotechnology is assessing the impacts nanomaterials have on human health and the environment, and creating or modifying existing product regulations to ensure that nanotechnology is used responsibly.
The Challenge of Regulating Nanomaterials
To this date, regulatory bodies like the United States Environmental Protection Agency (EPA), the United States Food and Drug Administration (FDA), and the European Food Safety Administration (EFSA) have not created any specific regulations for products containing nanomaterials.
In a recent report, The Scientific Committee on Emerging and Newly Identified Health Risks of the European Commission concluded that current methods for assessing the risks of nanomaterials may not be sufficient and that existing methodologies may need to be changed or new methodologies developed. They stressed that the current lack of knowledge regarding the characterization of nanoparticles and their effects does not allow for satisfactory risk assessments to be performed.
Scientists at the EPA and around the world are researching the effects of the most widely used nanomaterials on the environment and human health. They intend to develop research protocols for characterizing engineered nanomaterials and evaluating their toxicity in biological and environmental systems.
Fully understanding the environmental and health effects of nanoparticles and developing reliable testing methodologies is a multi-stage process.
First of all, it is essential to understand how the composition, shape, size, and morphology of nanomaterials affect their physical and chemical properties. Second, it’s essential to understand how nanomaterials with varying properties interact with biological systems like cells, tissues, and organs. Finally, it’s important to characterize and understand the full life cycle of nanomaterials. This is achieved using a process called environmental mapping, which describes how nanomaterials move through the environment, how they change with time, and how people, animals, plants, and other organisms are exposed to them.
How Nanomaterials Can Harm Human Health
Nanoparticles are the size are viruses, and are therefore small enough to travel through the body’s natural defenses via the lungs, intestinal wall, and skin.
Nanoparticles can make their way into the circulatory systems of human and animals, ultimately reaching all the tissues and organs in the body. Exposure to nanoparticles can influence cellular processes and cause cellular dysfunction, which in turn can lead to a variety of disorders. For example, cancer is caused by uncontrolled cellular proliferation, and neurodegenerative diseases are caused by premature cellular death.
Although nanomaterials have not been directly linked to specific diseases, studies in animals have suggested that exposure to nanoparticles could cause lung injuries. Other studies indicate that nanoparticle exposure could increase the risk of cancer. However, the full effects of nanomaterials on human and animal health are currently largely unknown and the lack of knowledge of the effects of nanomaterials on human health is a major challenge for the field of nanotechnology.
The powerful and potentially unknown nature of nanomaterials means that great care must be taken to protect people, animals, and the environment from unnecessary exposure to potential harm. This begins by determining which nanoparticles are dangerous, and which are benign. Nanotoxicology is a new field of nanoscience that aims to create an understanding of the properties and toxicity of nanomaterials.
Not all nanoparticles are toxic; toxicity is dependent on the chemical composition of particles, along with their shape, size, crystallinity, and particle age. While free nanoparticles can be particularly toxic to humans and animals due to their ability to penetrate the bodily defenses, fixed nanostructured materials such as those used as thin film coatings and microchip electronics are generally benign.
Some nanoparticles can even have positive effects on human health, and even nanomaterials that do display toxicity could be used to fight diseases like cancer on a cellular level. However, to regulate nanoparticle use and ensure that nanoparticles are used in an effective, responsible manner, it is important to understand the toxicology of each material, and how factors such as morphology, and particle age can affect the human body. The right methods for characterizing and assessing the toxicology of nanomaterials are, therefore, vital.
Assessing the Risks of Nanomaterials
Advanced analysis techniques are required for understanding the physical and chemical properties of nanomaterials and establishing correlations with their biological and environmental effects.
Robust knowledge of the relationships between nanoparticle properties and their impacts on biological systems allows us to predict which nanomaterials may pose the greatest risk to human health and the environment based on their physical properties, rather than requiring us to study the toxicity of each new nanomaterial individually. Such relationships could, in future, form the basis for nanotechnology-specific regulations.
Environmental mapping of nanomaterials requires advanced nanomaterial characterization techniques and adequate testing protocols. Measuring the concentration and size distribution of nanomaterials is vital for environmental mapping and studying environmental behavior. Tools such as single particle ICPMS can be used to count metal-containing nanoparticles and measure their mass, allowing nanoparticles to be tracked as they move through the environment. Diane Beauchemin from Queens University will give a talk at Pittcon 2018’s nanotechnology symposium on the latest advances in single particle ICPMS.
Advances in Raman spectroscopy relevant to nanomaterial characterization will be subject of talks from Eric Potma of the University of California and Bin Ren of Xiamen University.
Pittcon 2018 is the ideal setting to learn more about nanomaterial characterization techniques, testing methodologies, and mapping protocols for nanotechnology regulation.
References and Further Reading
1. ‘Test strategy for assessing the risks of nanomaterials in the environment considering general regulatory procedures’ – Kerstin Hund-Rinke, Monika Herrchen, Karsten Schlich, Kathrin Schwirn, Doris Völker, Environmental Sciences Europe, 2015.
2. ‘Nanomaterials and nanoparticles: Sources and toxicity – methods to evaluate the toxicity of nanomaterials’ – Cristina Buzea, Ivan I. Pacheco, Kevin Robbie, Biointerphases, 2007.
3. ‘Research on Nanomaterials’ United States Environmental Protection Agency https://www.epa.gov/chemical-research/research-nanomaterials
4. ‘Nanotechnology Programs at FDA’ United States Food and Drug Administration https://www.fda.gov/scienceresearch/specialtopics/nanotechnology/default.htm
5. ‘Nanotechnology’ European Food Safety Administration https://www.efsa.europa.eu/en/topics/topic/nanotechnology
6. ‘An assessment by the European Commission Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR)- Nanotechnology’ http://ec.europa.eu/health/scientific_committees/opinions_layman/en/nanotechnologies/index.htm#6
Chapter 2- Nanoparticles in Biological Environments
Nanomaterials have found applications in biological environments from drug delivery to imaging. However, to fully understand both the efficacy and potential toxicity of nanoparticles, it’s important to understand how they behave in complex biological solutions, tissues, organs, and bodily systems.
A lack of adequate characterization techniques means that determining the behavior of nanoparticles in biological systems remains challenging. Pittcon 2018 will cover the latest advances and cutting-edge technology for the characterization nanoparticles in biological environments.
Nanoparticles Demonstrate Complex Biological Behavior
Nanoparticles are precisely designed with specific physical and chemical properties that enable them to carry out their functions. For example, nanoparticles that actively target tumors are designed to be small and stable enough to travel through the body’s systems to the tumor, they must bind preferentially to receptors in the tumor, and they must release the drugs within them in response to specific changes in their environment. These demands result in specific chemical and physical requirements for nanoparticles depending on the application they are to be used in.
Nanoparticles which have been designed to exhibit certain properties in a simple solution may display entirely different behavior when they are exposed to complex biological solutions and systems. Understanding the behavior of nanoparticles in biological solutions, tissues, organs, and bodily systems is key to understanding both their efficacy and toxicity, and designing nanoparticles that fulfill their functions without adverse side effects.
Analytical methods for the detection and characterization of nanoparticles in biological systems are currently underdeveloped. The small size of nanoparticles, combined with their low concentrations and the highly complex nature of biological mixtures makes nanoparticle detection and characterization a challenging area of analytical chemistry. Lack of adequate characterization techniques for the detection and quantification of nanomaterials in biological media has prevented advances in understanding the environmental fate, transport, and potentially toxic effects of nanoparticles and nanomaterials.
The behavior and toxicity of nanoparticles are influenced by a range of physical and chemical properties including composition, surface chemistry, particle size, surface area, crystallinity and solubility. It would be impossible to characterize every nanoparticle property for each experiment, so researchers and regulatory authorities must select appropriate characterization techniques for the sample and decide which properties are the most important.
As nanoparticle systems are so complex, multiple techniques are often required to detect and characterize nanoparticles in complex biological systems. For example, in a study of gold nanoparticles ingested by mice, which aimed to determine where the nanoparticles would accumulate, researchers had to use a combination of autometallography, ICPMS, and neutron activation analysis to determine the nanoparticle in fact accumulated in the liver.
Detecting Nanoparticles in Biological Samples
One of the first challenges of tracking nanoparticles in biological systems is detecting their presence. Elemental analysis techniques such as ICPMS, X-ray absorption, and X-ray fluorescence (XRF) can be used to detect the presence of nanoparticles, depending on their compositions. For example, gold nanoparticles would be easily detected using elemental analysis.
The Pittcon Expo will feature technology such as the M4 TORNADO from Bruker, a Micro XRF tool that provides information on composition and elemental distribution to identify the presence and distribution of nanoparticles in biological samples.
Analyzing Nanoparticle Properties in Biological Milieu
There are many well-established techniques for the characterization of nanoparticles in solutions including calorimetry, dynamic light scattering, and nanoparticle tracking analysis. Malvern Instruments, top suppliers of nanoparticle characterization technology, will be present at the 2018 Pittcon Expo offering a range of solutions for analyzing nanoparticle number, size, zeta potential, and aggregate formation in biological solutions.
To fully understand the behavior of nanoparticles in biological environments, it’s important to understand their interaction with biological milieu, which are complex biological solutions. As nanoparticles exist as colloids in solutions, analytical techniques from colloid science can be used as a starting point for analyzing the properties of nanoparticles in biological milieu. However, they must be adapted to address both the chemical and physical properties of nanoparticles, and to ensure they do not measure biogenic colloids.
Interactions between nanoparticles and other substances present in biological solutions infer a biological identity onto the nanoparticle, which effects how it behaves in the solution and interacts with receptors, cells, and tissues. Flow cytometry-based methods can be used to detect molecular motifs on the surfaces of the nanoparticles that enable biological recognition, allowing researchers to characterize the biological identity of nanoparticles and predict how they will interact with cells.
Characterizing Nanoparticles in Tissues, Organs and Bodily Systems
It’s important to monitor the absorption, distribution, metabolism and excretion from tissues, organs and the body of nanoparticles as a whole to fully understand the efficacy and toxicity. Tracking nanoparticles within the body can be extremely challenging as nanoparticles due to their tiny size compared to the vast and complex bodily networks they are present in.
Various imaging techniques allow the biodistribution of nanoparticles in tissues and organs to be studied including super-resolution optical imaging (see Chapter 4), magnetic particle imaging, and nuclear imaging (see Chapter 3). The majority of imaging techniques require nanoparticles to be tagged with dyes or other labeling molecules. There are a few imaging techniques that enable imaging of unlabeled nanomaterials in tissues and organs without tagging. The majority are elemental imaging techniques including TEM-EDX, SXRF, and LIBS. LIBS offers particular advantages for imaging biological tissues including speed of operation, ease of use and full compatibility with optical microscopy. In a recent proof-of-concept study, LIBS was used to obtain 3D images of nanoparticles in organs.
References and Further Reading
1. ‘Analysis of engineered nanomaterials in complex matrices (environment and biota): General considerations and conceptual case studies’ – Frank von der Kammer, P. Lee Ferguson, Patricia A. Holden, Armand Masion, Kim R. Rogers, Stephen J. Klaine, Albert A. Koelmans, Nina Horne, Jason M. Unrine, Environmental Toxicology and Chemistry, 2011.
2. ‘Biodistribution of gold nanoparticles in mouse lung following intratracheal instillation’ – Evaldas Sadauskas, Nicklas Raun Jacobsen, Gorm Danscher, Meredin Stoltenberg, Ulla Vogel, Agnete Larsen, Wolfgang Kreyling, Håkan Wallin, Chemistry Central Journal, 2009.
3. ‘In situ characterization of nanoparticle biomolecular interactions in complex biological media by flow cytometry’ – Maria Cristina Lo Giudice, Luciana M. Herda, Ester Polo, Kenneth A. Dawson, Nature Communications, 2016.
4. ‘3D Imaging of Nanoparticle Distribution in Biological Tissue by Laser-Induced Breakdown Spectroscopy’ – Y. Gimenez, B. Busser, F. Trichard, A. Kulesza, J. M. Laurent, V. Zaun, F. Lux, J. M. Benoit, G. Panczer, P. Dugourd, O. Tillement, F. Pelascini, L. Sancey, V. Motto-Ros, Scientific Reports, 2016.
Chapter 3 – Nanobiotechnology
The new and improved properties of nanomaterials have led nanotechnology to find a wide range of applications, particularly in biological systems. The application areas for nanobiotechnology are vast and include nanoscopy, subcellular fractionation, drug delivery, biosensors, cancer therapy, tissue engineering, artificial organ generation, cell tracking, bioimaging, and ‘omics’ data generation.
The 2018 Pittcon nanotechnology symposium will feature a number of talks on the applications of nanobiotechnology.
The type of nanomaterial used in biological systems depends on the desired application. Whilst the applications of nanobiotechnology are vast, the number of nanomaterials that have been created for biological applications is even greater, and growing every day. Nanomaterials that have found biological applications include polymeric nanomaterials such as drug conjugates, micelles, and dendrimers; quantum dots which are used as luminescent nanoprobes; carbon nanotubes which have been used in drug delivery; and metallic nanoparticles which find applications as contrast agents and drug delivery agents.
Nanomaterials for biological applications can be further varied in their precise compositions, structures, dimensions, and surface modifications. This large variability results in an array of physical and chemical properties, which can be tailored to a required application. Silicon nanostructures have been gaining interest as analytical probes as they are well-defined materials with predictable properties and the potential to undergo surface modification. The 2018 Pittcon nanotechnology symposium will feature two talks on silicon nanostructures by Jeffrey Coffer of Texas Christian University and Jonathan Veinot of the University of Alberta.
Using Nanotechnology to Characterize Cells
Characterizing cells at a molecular level is an important step towards drug screening and personalized medicine. The characterization and quantification of the biological molecules that are responsible for the structure, function, and dynamics of an organism is referred to as ‘omics’, encompassing fields such as genomics, proteomics, and metabolomics. The 2018 Pittcon Expo will feature Bruker, who offers a range of unique analytical methods and technological systems in omics fields. The Expo will also feature AMSBio who supply cell systems and tissues ideal for researchers focusing on nanobiotechnology.
A talk at Pittcon 2017 by Dr Chad Mirkin of Northwestern University discussed how spherical nucleic acids can be used to characterize the genetic content of single cells. Spherical nucleic acids consist of strands of DNA or RNA arranged on a nanoparticle surface, enabling them to be recognized by cells and quickly internalized. Once inside the cellular environment they bind to complementary DNA or RNA and map the genetic content of live cells, acting as a diagnostic probe. This behavior means they can be used to diagnose medical conditions such as sepsis and identify tumor cells. Spherical nucleic acids have also found a number of other pharmaceutical applications including as gene regulation agents, and for cancer vaccinations.
Another approach of characterizing the contents of single cells is subcellular compartment analysis. Surface modified superparamagnetic nanoparticles have been used for subcellular compartment isolation. The nanoparticles enter the cells and bind to their target; and their magnetic properties allow them to be moved, taking their target with them and resulting in subcellular compartment isolation. The composition of the isolated compartments can then be analyzed independently.
In-Vivo Imaging Systems using Nanobiotechnology
Traditionally information pertaining to the biomolecular makeup of cells, tissues, blood, organs has been based on obtaining ex-vivo samples followed by biochemical analysis and/or microscopic imaging. However, these approaches lose information such as the exact 3D mapping of molecules within a living body, and how this changes as a function of time. The In-vivo molecular imaging of cells and tissues allows biological processes and cellular functions to be visualized at the molecular and cellular levels, creating opportunities for diagnosis without any invasion of the living organism.
Positron emission tomography (PET), and single photon emission computed tomography (SPECT) are nuclear molecular imaging tools that are frequently used in clinical practice. Radionuclide-labelled substances are introduced into the body and used as contrast agents, 3D images can then be obtained with the use of a CT X-ray scan. The enhanced permeability and retention (EPR) of nanoparticles in tumors, combined with their potential to undergo surface modifications, and specific target binding makes them ideal contrast agents for nuclear molecular imaging. Gold, carbon and lipid nanostructures have all been utilized in this way. FEI’s Amira software for preclinical imaging, which will be featured at the 2018 Pittcon Expo, combines structural information from micro-CT or MRI systems with functional data from PET, SPECT, or optical imaging to provide 3D images of tissues and organs.
Nanoprobes have also found applications in other molecular imaging techniques including optical imaging (see Chapter 4 for more detail), magnetic particle imaging, and photoacoustic imaging. Magnetic particle imaging is an imaging technique that detects the magnetic properties of iron-oxide nanoparticles injected into the bloodstream. Bruker, who provide of magnetic particle imaging technology, will be featured in the 2018 Pittcon Expo. Photoacoustic imaging produces images of organs and tissues using the photoacoustic effect, which refers to the generation of acoustic waves by the absorption of electromagnetic energy. Raol Kopelman of the University of Michigan will give a talk at the Pittcon 2018 nanotechnology symposium on the use of nanoprobes in 4D molecular tumor photoacoustic imaging.
References and Further Reading
1. ‘Using spherical nucleic acids to track and treat disease’ https://www.news-medical.net/news/20170301/Using-spherical-nucleic-acids-to-track-and-treat-disease.aspx
2. ‘Nanotechnology: from In Vivo Imaging System to Controlled Drug Delivery’ – Maria Mir, Saba Ishtiaq, Samreen Rabia, Maryam Khatoon, Ahmad Zeb, Gul Majid Khan, Asim ur Rehman, Fakhar ud Din, Nanoscale Research Letters, 2017.
3. ‘Designer nanoparticle: nanobiotechnology tool for cell biology’ – Deepak B. Thimiri Govinda Raj, Niamat Ali Khan, Nano Convergence, 2016.
4. ‘Radionuclide-labeled nanostructures for In Vivo imaging of cancer’ – Won-Kyu Rhim, Minho Kim, Kevin L Hartman, Keon Wook Kang, Jwa-Min Nam, Nano Convergence, 2015.
5. ‘Single cell analysis: the new frontier in ‘Omics’’ Daojing Wang, Steven Bodovitz, Trends in Biotechnology, 2010.
Chapter 4 – Nanoscale Optical Imaging
Optical imaging of nanoscale structures has previously been limited by the ‘diffraction barrier.’ Near-field techniques and the use of nanoparticles to enhance optical imaging techniques have previously pushed the boundaries of the traditional diffraction barrier. Super-resolution fluorescence microscopy has recently broken the diffraction barrier leading to a ‘resolution revolution’ in light microscopy.
Nanoscale optical imaging will be covered in detail at Pittcon 2018, where 2014 Nobel Laureate Dr Stefan W. Hell will give the Plenary lecture on “Optical Microscopy: The Resolution Revolution.”
For centuries, optical microscopy and other optical techniques have been vital components of the analytical toolbox. Light microscopes have provided many important discoveries, particularly within the fields of cell biology and microbiology. The resolution of light microscopes has traditionally been limited by the fact that light cannot be focused more sharply than diffraction allows, resulting in a ‘diffraction barrier’ at a resolution of approximately 200 nm, preventing light microscopes from resolving nanoscale objects. As many sub-cellular features are smaller than the resolution limit of optical microscopy, they cannot be observed using traditional light microscopy and other optical techniques.
Nanoscale imaging is an important and rapidly developing area of analytical science. To adequately understand cells and the effects that nanoparticles have on them, it is important to observe and characterize nanoscale structures inside cells, including both natural sub-cellular features, and engineered nanomaterials.
Until recently, observing nanoscale structures has relied on imaging techniques such as atomic force microscopy (AFM), X-ray based techniques, and electron microscopy. These techniques are often combined to provide information about complex biological structures. For example, a recent study by Yangquanwei et al., at the University of Guelph, combined atomic force microscopy, scanning electron microscopy, and scanning transmission X-ray microscopy to study the nanoscale morphology, composition, and biochemical properties of quinoa chromosomes.
Pushing the Limit of the Diffraction Barrier
As the resolution diffraction limit of optical techniques depends on the incident wavelength and the objective lens of the microscope used, using near-field techniques enables imaging resolutions to move beyond the traditional far-field diffraction limit. Near-field techniques place the light source or the detection probe close to the sample (i.e., in the near-field). Such techniques include tip-enhanced Raman Spectroscopy (TERS), which provides resolutions below 25 nm. TERS can be used for the investigation of complex surfaces such as those of heterogeneous catalysts, as Bin Ren of Xiamen University will discuss at Pittcon 2018’s nanotechnology symposium.
Combining Raman spectroscopy and other forms of AFM can provide additional information. For example, a study published in 2012 by researchers from Chemnitz University of Technology combined Raman spectroscopy imaging and current sensing AFM (CS-AFM), to investigate the properties of carbon nanotubes and find out whether the defect concentration in carbon nanotubes increased at the CNT/electrode interface.
Another technique that utilizes the near-field is near-field scanning optical microscopy (NSOM/SNOM), a form of scanning probe microscopy, which can achieve resolutions up to 20 nm. However, the requirement to place the excitation source or detection probe close to the target object makes it difficult to look ‘into’ a live cell or tissue, limiting the applications of near-field techniques in biology.
The Pittcon 2018 Expo will feature a number of companies providing cutting-edge nanoscale imaging equipment. Horiba Scientific will display their range of nanoscale Raman imaging technologies including TERS enabled AFM-Raman spectrometers at the expo. Bruker will also display their nanoscale imaging solutions including the Innova-IRS, a complete TERs solution, and the Dimension Icon Raman, which provides high-performance AFM with co-localized micro-Raman capability.
Using Nanoparticles to Improve Optical Imaging
Multispectral imaging captures image data at frequencies across the electromagnetic spectrum from near infrared to ultraviolet light, providing an array of analytical information. However, multispectral imaging technology is often expensive and bulky.
Metallic nanoparticles can act as optical antennas and concentrate and localize incident light, allowing them to act as near-field optical probes and interact locally with the sample. Nanoparticles can, therefore, be used to improve fluorescence imaging by increasing fluorescence efficiency.
Metallic nanoparticles have been found to enhance the intensity of Raman scattering by 103-108 times, in a phenomenon that has been named surface-enhanced Raman scattering (SERS). SERS has been used in various studies to detect the presence of molecules at low concentrations, and provide spatially resolved nanoscale composition analysis.
The Pittcon 2018 nanotechnology symposium will feature a talk from Eric Potma of the University of California, Irvine on developments in SERS and surface-enhancement coherent anti-stokes Raman scattering (SE-CARS) and their applications.
Breaking the Diffraction Limit with Fluorescence Microscopy
Fluorescence microscopy is an optical technique that utilizes fluorescence tagging to image proteins, structures and cells. The ability to detect specific molecules in live cells makes fluorescence microscopy one of the most widely applicable techniques in cell biology. However, until recently the applications of fluorescence microscopy in biology were limited by the resolution diffraction limit.
Recent advances in fluorescence microscopy have led to the development of a number of super-resolution microscopy techniques that are able to break the ‘diffraction barrier.’ Super-resolution fluorescence microscopy provides ‘diffraction unlimited’ images. The diffraction barrier was broken in 1994 by Dr Stefan W. Hell and his team using a technique is known as stimulated emission depletion microscopy (STED).
In STED the physical or chemical properties of the fluorescent species are used to maintain neighboring molecules in different fluorescent states, turning fluorescence on and off and allowing them to be distinguished from each other. STED resolutions under 3nm have been reported, although 30-80 nm is more typical. Dr Hell received the Nobel Prize in Chemistry in 2014 ‘for the development of super-resolved fluorescence microscopy,’ together with Eric Betzig and William Moerner.
Dr Hell’s team has since developed a new fluorescence microscope called MINIFLUX, which provides a resolution of 1 nm, the ultimate resolution limit for fluorescence microscopy. Overcoming the diffraction barrier allows researchers to obtain images of living cells and tissues at nanoscale. Dr Hell, who is the Director of the Max Planck Institute for Biophysical Chemistry in Göttingen, will give the Plenary Lecture at Pittcon 2018 on the subject of breaking the diffraction barrier in fluoresce microscopy and MINIFLUX nanoscopy.
A variety of STED microscopes are now commercially available and instrumentation is becoming more compact, reliable and economical. Other super-resolution fluorescence microscopy techniques include stochastic optical reconstruction microscopy (STORM), photo-activated localization microscopy (PALM).
The 2018 Pittcon Expo will feature a range of leading companies in super-resolution microscopy technologies including Bruker, who supply the Vutara 352 Super Resolution Microscope; Olympus, who supply the SpinSR10 Super-Resolution Imaging System; Thermo Fisher Scientific, who are leaders in fluorescence technology and Molecular Probes for super-resolution microscopy; Keysight, who provide laser combiners and precision optics ideal for super-resolution microscopy; and Andor Technology, who supply cameras for super-resolution imaging.
References and Further Reading
1. ‘Current achievements of nanoparticle applications in developing optical sensing and imaging techniques’ – Jong-ryul Choi, Dong-Myeong Shin, Hyerin Song, Donghoon Lee, Kyujung Kim, Nano Convergence, 2016.
2. ‘Cytogenetic analysis of quinoa chromosomes using nanoscale imaging and spectroscopy techniques’ Zhong Yangquanwei, Suresh Neethirajan, Chithra Karunakaran, Nanoscale Research Letters, 2013.
3. ‘Nanoscale optical and electrical characterization of horizontally aligned single-walled carbon nanotubes’ – Raul D Rodriguez, Marius Toader, Sascha Hermann, Evgeniya Sheremet, Susanne Müller, Ovidiu D Gordan, Haibo Yu, Stefan E Schulz, Michael Hietschold, Dietrich RT Zahn, Nanoscale Research Letters, 2012.
4. ‘Pittcon Adds Plenary Lecture to 2018 Program Presented by the 2014 Nobel Laureate, Stefan W. Hell’ https://pittcon.org/pittcon-adds-plenary-lecture-2018-program-presented-2014-nobel-laureate-stefan-w-hell/
5. Optical microscopy resolution revolution https://www.news-medical.net/news/20170912/Optical-microscopy-resolution-revolution.aspx
6. ‘MINIFLUX Microscopy: Achieving Ultimate Resolution Limit in Fluorescence Microscopy’ http://www.imaging-git.com/news/miniflux-microscopy-achieving-ultimate-resolution-limit-fluorescence-microscopy
7. ‘Multispectral imaging with vertical silicon nanowires’ – Hyunsung Park, Kenneth B. Crozier, Scientific Reports, 2013.
Chapter 5 – Nanosensors
Nanosensors offer increased specificity and sensitivity compared with traditional sensors and have therefore found a wide range of applications from medicine to food safety.
Nanosensors and related technologies will be featured at the Pittcon 2018 nanotechnology symposium and a variety of relevant companies will be present at the expo.
The term nanosensors include all sensors that use active nanomaterials. The increased sensitivity of nanosensors stems from the ability to finely tune the chemical and physical properties of nanomaterials, meaning they can be designed to only interact with the target molecule, even in complex solutions. The high surface area to volume ratios of nanomaterials and the ability to create nanostructured surfaces further enhances the sensitivity of nanosensors. The unique properties of nanosensors enable them to find a wide range of applications including disease testing, biomarker detection, contaminant detection, pollution monitoring and manufacturing monitoring.
Nanosensors can work in a number of different ways. One of the most widely applied types of nanosensors are electrochemical nanosensors, which detect changes in resistance when an analyte binds with the nanomaterial of the sensor. Electrochemical sensors have historically been an attractive option, due to the high sensitivity that can be obtained using relatively inexpensive equipment. However, previous electrochemical sensors have been limited by sensitivity in highly complex, real-world samples. Nanomaterials have high surface area to volume ratios and can therefore sample large volumes of solution, enabling them to detect target molecules even when they are present in very low concentrations. Other types of nanosensors include electromagnetic or plasmonic nanosensors, spectroscopic nanosensors, magnetoelectric or spintronic nanosensors, and mechanical nanosensors.
Electrochemical Nanosensors for Biomarker Analysis
At Pittcon 2016 Dr Shana Kelly gave a talk on nanostructured microelectrodes for biomarker analysis. She described how electrochemical sensors with nanostructured surfaces allow rapid turnaround in biomarker detection, allowing infectious diseases to be diagnosed within 20 minutes. She also discussed how electrochemical nanosensors could impact transplantation medicine; rapid assessment of donated tissues and organs at a molecular level allows surgeons to quickly assess whether an organ is a good match for the recipient.
In 2018, the Pittcon nanotechnology symposium will feature a talk by Heather Clark of Northeastern University on using an array of tunable nanosensors to detect small molecules and build images of neurotransmitter release in the brain. Paul Bohn of the University of Notre Dame will give a talk on the use of nanomaterials in electrochemical arrays and the use of electrochemical zero-mode waveguide arrays for imaging single reaction events. The food safety symposium at Pittcon 2018 will feature discussions on nanosensors for food safety including talks from Antje Baeumner of the University of Regensburg on nanomaterials for microanalytical systems, and Sam Nugen of Cornell University on nanobots for food safety.
Numerous applications for nanosensors have been reported, particularly in medicine. In one example, a group of researchers from China designed an electrochemical nanosensor for the quantitative detection of Brucella melitensis, a bacterium that causes brucellosis. The World Health Organization recommends preventing the spread of brucellosis among humans by monitoring and eliminating the infection in animals. However, methods for detecting Brucellae bacteria are often complex, expensive and time-consuming. As brucellosis is mainly an issue in the developing world, rapid, inexpensive, and easy-to-use detection methodologies for Brucellae must be developed.
The team from China were able to quantitatively detect low levels of Brucellae antibodies, which indicate the presence of Brucellae bacteria in animal milk within 1.5 hours. Gold nanoparticles were used to increase the electrode surface area and aid antibody binding to the sensor. The method utilized a cheap, disposable electrode and could provide the basis for an easy-to-use, hand-held device to allow the rapid detection of Brucellae bacteria.
Chemiluminescence and fluorescence nanosensors
Chemiluminescence sensors can also be enhanced using nanoparticles. Chemiluminescence sensors detect the emission of light as a result of a chemical reaction involving the target molecule. For example, in a recently reported cholesterol chemiluminescence sensor, the cholesterol reacts with oxygen to form hydrogen peroxide, the hydrogen peroxide then reacts with luminol, producing a light emitting excited molecule. The light produced by the reaction is detected and measured to determine to concentration of cholesterol in the sample. Nanoparticles and other nanomaterials can catalyze chemiluminescence reactions. Furthermore, they can concentrate and localize the light produced, thereby increasing the sensitivity of the sensor.
Fluorescence nanosensors use an external light source to excite a target or product molecule, the light is then emitted at a different wavelength as the molecule relaxes, allowing the presence of the molecule to be detected. Surface modified nanoparticles can also be used to bind to the target molecule, producing fluorescent nanoparticles. Chemiluminescence and fluorescence nanosensors both require instrumentation that can accurately detect and measure light emissions, while fluorescence nanosensors also require an external excitation source. Companies including PerkinElmer, Malvern Instruments and Oriel will be present at the 2018 Pittcon Expo displaying a range of optical meters and sensors, spectrometers, laser light sources, and fluorescence detection systems.
References and Further Reading
1. ‘Can nanostructured microelectrodes be used to analyze biomarkers? An interview with Dr Shana Kelley’ https://www.news-medical.net/news/20151215/Can-nanostructured-microelectrodes-be-used-to-analyze-biomarkers-An-interview-with-Dr-Shana-Kelley.aspx
2. ‘Rapid Quantitative Detection of Brucella melitensis by a Label-Free Impedance Immunosensor Based on a Gold Nanoparticle-Modified Screen-Printed Carbon Electrode’ – Haiyun Wu, Yueming Zuo, Chuanjin Cui, Wei Yang, Haili Ma, Xiaowen Wang, Sensors, 2013.
3. ‘Design a New Strategy Based on Nanoparticle-Enhanced Chemiluminescence Sensor Array for Biothiols Discrimination’ – Maryam Shahrajabian, M. Reza Hormozi-Nezhad, Scientific Reports, 2016.
4. ‘Nanosensors, A Definition, Applications and How Nanosensors Work’ https://www.azonano.com/article.aspx?ArticleID=1840
Nanoparticles have unique, tunable properties. As a result, nanomaterials have found applications in a vast array of fields including medicine, food technology, cell biology, and analytical chemistry.
For researchers keen to discover the latest trends in nanotechnology and nanomaterial characterization, the Pittcon 2018 Conference is a must-attend event. This year, Pittcon will feature a nanotechnology symposium that will enable delegates to learn from experts in the field of nanotechnology.
The rapidly advancing field of nanotechnology presents new challenges for analytical chemistry. Understanding the behavior of nanomaterials in biological systems is particularly challenging, but vital for biological and medical applications of nanobiotechnology. Often, multiple techniques are required to adequately characterize the properties of nanoparticles and how they interact with complex chemical and biological systems.
The Pittcon Expo will feature many industry-leading equipment manufacturers that supply the latest instruments for characterizing nanomaterials over a wide range of applications and environments. For researchers that are unsure of the best way to characterize their nanomaterial system, Pittcon is the place to find the answer.