The modern-day clinical laboratory has evolved in response to clinical demands and a need to adopt a steady stream of new technologies. Among the technological innovations that have had a large impact are computing and informatics, automation, antibody-based analytical methods, nucleic acid sequencing and probing techniques, sensor technology, and luminescence-based sensing techniques, such as chemiluminescence and fluorescence. The changing landscape of healthcare provides a continuing stimulus to the evolution of clinical testing, both in central laboratories and at the point of care. Progress in miniaturization has created devices with micrometer-sized features designed to perform a range of assays and that integrate all of the steps in an assay onto a single small device—the so-called lab-on-a-chip. The next step in miniaturization is the descent from the micrometer scale to the nanometer scale and the exploitation of nanotechnology—nanosized structures in the interval from 1 to 100 nm. Nanotechnology is now a major area of research and development. Many applications for nanosized materials (e.g., nanoparticles) have emerged in in vitro diagnostics, imaging, and therapeutics. In common with many types of new development, the arrival of nanotechnology has been heralded by considerable hype about its potential and future promise, but these high expectations have been tempered by concerns over the technology's safety (1). This new technological area is multifaceted and already has found extensive applications in >1000 consumer products (http://sis.nlm.nih.gov/enviro/nanotechnology.html; http://www.nanotechproject.org/inventories/consumer/). In clinical testing, 2 avenues of exploitation that have emerged are the use of nanoscale materials as reagents (e.g., nanoparticle labels and therapeutic agents) (2, 3) and the development of nanoscale devices (e.g., nanopores) (4). The latter is a distant prospect, and most work has centered on the former application.
In this Q&A, Dawn Bonnell, Amit Kulkarni, Joseph Wang, Yuri Miyahara, and David Ure, experts in the field of nanotechnology, answer questions about the current status of nanotechnology.
In Vitro Diagnostics
What advantages do you see for nanoparticulate labels in immunodiagnostics and nucleic acid technology?
Dawn Bonnell3: There are several nanotechnologies that are vying for the X Challenge in the DNA-sequencing arena. Examples include isolating polymerase reactions in zero-mode waveguides, threading DNA through nanopores, and bead labeling with multiplexed optical fibers. The demonstrations and prototypes are compelling evidence that this goal will be realized at some level in the near term.
Amit Kulkarni4: Nanomaterials-based techniques promise to be enablers for a variety of in vitro diagnostic assays, where the overarching goal is detection of disease as early as possible to the extent of detecting single defective cells or low-abundance biomarkers capable of predicting onset of disease. The key advantage of nanoparticulate labels is sensitivity—sensitivity for rapid detection and accurate quantification of biomarkers present at very low concentrations. The high sensitivity can enable assays to be quicker, be flexible, and require small amounts of target biomarker, thereby resulting in reduced cost. Nanoparticulate labels, if surface-engineered correctly, can also show superior separation and nonspecific binding compared to state-of-the-art technologies. Gold nanoparticles, quantum dots, magnetic nanoparticles, and carbon nanotubes are examples of labels that can provide new platforms for multiplexed immunoassays with the potential for integration into high-throughput protein arrays and clinical diagnosis.
Joseph Wang5: Nanomaterials, such as nanoparticles, nanowires, and nanotubes have great promise for making major impact on the field of medical diagnostics. For example, certain nanomaterials allow for the design of powerful multiplexed bioassays for simultaneous measurements of multiple disease markers. Such capability reflects the fact that the sizes, shapes, and compositions of metal nanoparticles and quantum dots can be systematically tailored to produce materials with specific absorptive, emissive, and light-scattering properties.
Nanotechnology also offers unique opportunities for designing ultrasensitive bioassays of proteins and nucleic acids (5). Numerous studies have demonstrated the broad potential of bioconjugated nanoparticles as tags (tracers) for amplified transduction of biomolecular recognition events. The remarkable sensitivity of nanomaterials-based sensing protocols opens up the possibility of detecting ultratrace concentrations of target analytes that cannot be measured by conventional methods.
Finally, nanotechnology-based instruments hold the potential for point-of-care applications where assays could be conducted by the primary-care physician in their office or by the patient in their home. Additionally, these systems require much smaller sample volumes, thus reducing the cost associated with reagents and analysis time.
Yuri Miyahara6: Long-term stability of nanoparticles is one of the important advantages for nanoparticles. Brightness and sharp bandwidth are also good points, if nanoparticles are designed and fabricated properly.
David Ure7: The obvious advantage is one of greater assay sensitivity. While there is an increasing trend towards label-free platforms, labeled methods remain the most powerful route to ultrasensitive biomarker discovery, validation, and clinical use, and while existing labeling methods meet the sensitivity requirements of many immunodiagnostic assays, opening the door to new sets of low-abundance biomarkers could lead to diagnostic applications with major social and commercial impacts.
Can nanotechnology make DNA sequencing quick, cheap, and easy?
Amit Kulkarni: The benefits mentioned above generally apply to DNA sequencing. Gold nanoparticles tagged with short segments of DNA can be used for detection of genetic sequence in a sample. There have been recent advances in nanopore-based devices that provide single-molecule detection and analytical capabilities by electrophoretically driving molecules in solution through nanoscale pores. The nanopore provides a highly confined space within which single nucleic acid polymers can be analyzed in a high-throughput manner. It has been shown that single-stranded genomic DNA or RNA can be identified and characterized without amplification, a unique analytical capability that makes inexpensive, rapid DNA sequencing a possibility. Of course, further research and development efforts are necessary to convert this technology into reality.
Joseph Wang: Nanotechnological advances based on scanning probe microscopes and single-molecule nanopore systems represent attractive new approaches for rapid low-cost DNA sequencing. For example, efforts at the Arizona State University Biodesign Institute and at the University of California – Irvine rely on nanotechnology, particularly on scanning tunneling and atomic force microscopes, to read DNA strands. Eventually, these and related nanotechnological genomic research activities will make genome sequencing a routine diagnostic tool in medical care. This would be particularly attractive for future personalized medicine. For example, such point-of-care DNA sequencing could provide doctors with more resources to predict disease and to customize prescription medication.
Yuri Miyahara: Large-scale integration of biochemical reaction sites/chambers is one of the big advantages for nanotechnology. Also, we can access single biological molecules more easily by the use of nanostructures such as nanopillars, nanogaps, nanowires, nanopores, nanoparticles, and so on. These characteristics of nanotechnology would enable us to realize high-throughput screening of drugs, high-throughput DNA sequencing by parallel processing of biochemical reactions, and highly sensitive or even single-molecule detection of biomolecules. Therefore, early-stage detection of diseases or personalized medicine would be possible. Another aspect for nanotechnology is that analytical systems can be further miniaturized by integrating sensors, tubes, valves, and signal-processing circuits. Thus, we can locate the analytical system near the patient. Highly advanced medical treatment and diagnostics can be provided to patients, not only in large hospitals but also in clinics, doctors' offices, and even the patient's home, thus further advancing the scope of telemedicine systems.
David Ure: Yes, nanotechnology can make DNA sequencing quick, cheap, and easy. The ability to engineer devices on the nanoscale will inevitably improve processing costs and speeds for biological materials, as well as facilitate more rapid detection. Ultimately, integrated “lab-on-a-chip” devices will incorporate numerous elements of “nanotechnology.” For example, the drive to lower cost, and faster, simpler processing will inevitably cross paths with nanoscale circuitry and nanofluidics.
What do you see as the most important advantages of nanoimaging agents, and what barriers to implementation do you envisage?
Dawn Bonnell: In general, there are two advantages of nanoimaging agents: better performance or increased/different functionality. Quantum dots are an example of the former in that they can provide longer lifetimes than organic analogs for optical imaging. Ferromagnetic particles are an example of the latter in that magnetic fields can be used to isolate and/or identify.
Amit Kulkarni: Most magnetic resonance and x-ray contrast agents today are excellent at providing anatomical information, information on structures and features present in the body. As we drive towards a healthcare model where we want to diagnose disease early—sometimes even before symptoms exist—there is a need for imaging agents to provide not just anatomical information but also functional information, information regarding biological processes happening in the body at the cellular or molecular level. While few radiopharmaceutical agents enable functional imaging using nuclear imaging techniques, nanoparticle imaging agents have the potential to do the same in magnetic resonance, x-ray, and computed tomography imaging modalities.
A nanoparticle imaging agent can pack several hundred atoms of the signal-generating moiety and have significantly higher sensitivity compared to small-molecule imaging agents. While small-molecule agents leak out of blood vessels into the extravascular space, nanoparticle agents tend to remain intravascular (or in the blood pool), which allows for determination of certain hemodynamic parameters important for the physiological understanding of the disease. More importantly, the size and surface nature of nanoparticles can be engineered to get the most favorable in vivo behavior. For example, agents can be tailored to stay visible in the bloodstream long enough for clinicians to more effectively pinpoint disease. Nanoparticles can allow attachment of biomarker-specific vectors that can be targeted to disease sites in the body. The ability to see and target disease at the cellular or molecular level could promote the detection of cancer and cardiac disease at much earlier stages. These agents could also be used to more rapidly and accurately monitor the effectiveness of treatments.
The unique differences between nanoparticle and small-molecule imaging agents provide the benefits mentioned above. However, given that nanoparticles are a new class of compounds, they do pose certain challenges. Reproducible and repeatable manufacturing of these materials at reasonable costs is absolutely essential for commercial realization of these agents. Thoughtful consideration needs to be given to developing the right tools and techniques for complete characterization of nanomaterials. Safety is the most important aspect in the development of any new injectable material. With the right in vitro biocompatibility assays and in vivo models, it is essential to identify and characterize critical parameters related to the absorption, distribution, metabolism, excretion, and toxicity profiles of the nanoimaging agent. While these challenges generally apply across most nanoparticles, I would stress that every nanoparticle is unique and should be treated on a case-by-case basis.
Joseph Wang: Nanotechnology offers considerable promise for designing contrast agents used for highlighting different tissues in the body or to help distinguish between healthy and diseased tissue. Recent nanotechnological advances have led to greatly improved imaging tools and contrast agents towards the end goals of detecting disease as early as possible (eventually at the level of a single cell) and monitoring the effectiveness of therapy. Such imaging capability is often combined with a controlled drug release using multifunctional nanomaterials (such as core–shell nanocapsules). Yet, some of these agents demonstrate prolonged tissue retention and/or contain heavy metals—both of which increase the risk of toxicity.
Yuri Miyahara: Multiple labeling of tissues and simultaneous imaging of the spatial distribution of specific biomolecules are important advantages for nanoimaging. Also, nanoimaging agents that are sensitive to near-infrared light are very useful for noninvasive imaging of tissues localized deep in biological systems such as the pancreas, liver, kidney, and so on. However, safety issues such as cytotoxicity will have to be considered.
David Ure: Improved sensitivity and lower biological disruption are the two primary advantages that I see for nanoimaging agents. The sensitivity improvements, while beneficial, may ultimately be limited to niche markets, as existing imaging platforms may prove proficient for many applications. However, the ability for nanoimaging agents to interact with biological molecules in a less disruptive manner than existing imaging agents could offer more profound benefits by enabling more accurate and less disruptive/invasive imaging techniques.
Will nanoimaging agents displace existing agents for imaging?
Amit Kulkarni: Not necessarily. Existing small-molecule imaging agents have been successfully and safely used over the last two decades for several clinical indications. Existing agents are excellent at providing anatomical information with good spatial and temporal resolution. Nanoimaging agents promise to provide information regarding physiology and function, which, when coupled with anatomical information, will allow more accurate and early diagnosis of disease. Nanoimaging agents also have the potential to open niche areas that are currently unexplored.
Joseph Wang: Yes, certain nanoparticles offer some unique advantages as image-enhancement agents and could eventually replace existing imaging agents. Such new nanoimaging agents hold great promise for a sensitive and accurate detection of early-stage cancer. Yet, routine imaging applications would require investigating the potential adverse effects of such imaging agents and their clearance properties.
David Ure: In applications where existing imaging agents have limited utility, yes. However, the added utility initially offered by nanoimaging agents is likely to be one of performance rather than cost. Accordingly, initial applications are likely to be mainly limited to emerging/new applications that existing imaging agents cannot address. However, as the technology progresses, some of the new nanoimaging agents have the potential to offer significant cost savings once the production procedures for these materials improve. As such, as this new technology matures, I would anticipate the new class of imaging agents to displace existing ones on cost as well as performance.
How will nanotechnology contribute to advancements in therapy, and which diseases could benefit most?
Dawn Bonnell: Some of the highest-impact “low hanging fruit” in nanotechnology is in the area of targeted therapeutics. Strategies using plasmonic particles and drug delivery are two examples that are advancing toward implementation. The development of “artificial cells” is also exciting. Some of the first impacts will be in treating cancer tumors.
Amit Kulkarni: For therapy applications, nanoparticles have the potential to be very effective as drug-delivery agents. Nanoparticles can improve the bioavailability and pharmacokinetics of therapeutics. Small-molecule drugs that suffer from low solubility can be loaded into a nanoparticle, which can then be tailored to target specific disease sites in the body. The nanoparticle therapeutic agent can also be engineered to control the release of drugs over extended periods of time. Cancer is a disease that can benefit the most from nanotechnology-based therapeutics. There already are a couple of nanochemotherapeutics in the clinic, and several more are in development.
Joseph Wang: The field of nanomedicine may dramatically change the way different diseases are detected and treated. Nanocarriers can be used to bring drugs directly to diseased areas of the body, thus minimizing the exposure of healthy tissues while increasing the accumulation of the drug in the tumor area. This will reduce the dose necessary for treatment and the damage caused to healthy tissue by powerful pharmaceuticals. To further the application of nanoparticles in disease therapy, it is important that the systems are stable, safe, biocompatible, capable of being functionalized, and directed to specific target sites in the body after systemic administration. Nanomedicine is thus poised to make a significant transition from basic to translational research and commercialization. Yet, progress towards clinical trials of specific nanocarriers will depend on the outcomes of efficacy and toxicology studies, which will provide the necessary risk-to-benefit assessments for such nanomaterials.
Yuri Miyahara: Drug-delivery systems for cancer would be most promising in terms of the requirements from society.
David Ure: My focus is on the development of solutions for cancer diagnosis, and our core technology platform integrates numerous “nanotech” elements. To this end, I can say with certainty that the treatment of most forms of cancer will benefit substantially from nanotechnology. From my perspective, this will be driven in part by improved diagnostic solutions (underpinned by nanotech-based devices delivering improved sensitivity, accuracy, and accessibility). In cancer, improved diagnosis leads directly to improved therapy, with early and more accurate diagnoses enabling more targeted and more effective therapies to be administered. Ultimately, I see the focus on cancer treatment moving away from late-stage diagnosis and expensive, socially burdensome treatment to early-stage diagnosis and less-invasive, lower-impact therapies.
Are public concerns justified about the safety of nanosized structures, such as nanoparticles and nanotubes?
Dawn Bonnell: There are some concerns that are rational and can be or are being addressed now. As with any new chemical or pharmaceutical, safety should be determined, and regulatory structures are in place to address this. Workplace exposure risks should be considered when developing new manufacturing processes, and the National Institute for Occupational Safety and Health (NIOSH) has issued guidelines for handling nanoparticles.
There are challenges in the study of toxicology and the environmental impact of nanostructures that center on the lack of measurement tools and standard materials. As these challenges are addressed, the studies will provide more guidance.
Some public concerns are informed by fundamental misconceptions regarding science. These should be addressed with information outreach.
Amit Kulkarni: Nanotechnology-related environmental, health, and safety research is an essential component in the development of nanomaterials for various applications. It is necessary to understand the mechanisms of biological interaction with nanomaterials and to develop broadly useful tools and tests for characterizing nanomaterials in different environments. Safety studies need to happen throughout the life cycle of the nanomaterial—during research and development, manufacturing, consumer use, and, finally, during the disposal or recycle stage of the nanomaterial. These studies need to be performed on a case-by-case basis since every nanomaterial is unique. Accurate conclusions for each nanomaterial can be drawn only based on studies performed using solid, widely accepted scientific methods. Some level of standardization of such tests is necessary to enable accurate safety assessment of the nanomaterial.
Joseph Wang: The safety of nanoscale materials used for in vivo biomedical applications of nanomaterials, such as imaging and therapy, is of obvious major concern. The ultrasmall size and unique properties of nanomaterials have led to increasing concerns about their potential toxicity. The toxicological profiles and potential adverse effects of such materials are currently being explored by many laboratories around the world. Establishing the risk–benefit balance for nanomaterials used for therapy or imaging will ultimately determine their clinical fate.
Yuri Miyahara: Safety issues are an important publicconcern. We have to demonstrate the safety of nanostructures before medical application. Encouragingly, however, some nanostructures have already been demonstrated to be applicable as drug-delivery systems agents.
David Ure: Health and safety should always be of highest priority with any new technology. Accordingly, it is not right to dismiss public concern. However, it is easy to overstate the risk of “nanotechnology,” and such overstatements are often fuelled by sci-fi–based doomsday scenarios. The reality is that research into nanotechnology needs to adhere to the strict health and safety protocols of any new science, and industry must be vigilant in its implementation of regulations and controls.
Where would you place (a) nanotechnology-based diagnostics, (b) nanoimaging agents, and (c) nanotherapeutic agents on the 5-phase Gartner hype cycle (Table 1)?
Dawn Bonnell: Nanotechnology, as a whole, is past the peak of hype that leads to inflated expectations, but I don't see disillusionment. There is increased attention to toxicological and environmental effects, which is, for the most part, rational and a positive development, but such attention does not constitute disillusionment. In the area of venture capital, the investment level in the last decade has slowed considerably, perhaps waiting for those commercial successes or perhaps due to the recession. Having said this, nanotechnology is not a single technology or even a single sector. It is a descriptor of enabling technologies that cross sectors, ranging from energy to communications to medicine. Superimposed on any overall consideration are the more relevant trajectories of specific technologies, such as DNA sequencing and targeted drug delivery.
Joseph Wang: In my opinion, nanoimaging and nanotherapy are still in phase 2 in the Gartner cycle, while nanodiagnostics is in phase 4.
Yuri Miyahara: Nanotechnology-based diagnostics would be at the trough of the disillusionment phase, and I would place nanoimaging agents and nanotherapeutic agents on the slope of the enlightenment phase.
David Ure: I would place both nanotechnology-based diagnostics and nanoimaging agents on the slope of enlightenment (phase 4), and nanotherapeutic agents in the phases of technology trigger/peak of inflated expectations (phases 1/2).
↵3 Dawn Bonnell, Professor, Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA.
↵4 Amit Kulkarni, Manager, Chemical Nanotechnology Laboratory, General Electric Company, Niskayuna, NY.
↵5 Joseph Wang, Professor, Department of Nanoengineering, University of California San Diego, La Jolla, CA.
↵6 Yuri Miyahara, Managing Director, Biomaterials Center, National Institute for Materials Science, Tsukuba, Japan.
↵7 David Ure, Managing Director, Inanovate Ltd., Birmingham, UK.
Author Contributions: All authors confirmed they have contributed to the intellectual content of this paper and have met the following 3 requirements: (a) significant contributions to the conception and design, acquisition of data, or analysis and interpretation of data; (b) drafting or revising the article for intellectual content; and (c) final approval of the published article.
Authors' Disclosures of Potential Conflicts of Interest: Upon manuscript submission, all authors completed the Disclosures of Potential Conflict of Interest form. Potential conflicts of interest:
Employment or Leadership: D. Bonnell, International Technology Corporation; D. Ure, Inanovate, Inc.
Consultant or Advisory Role: None declared.
Stock Ownership: D. Ure, Inanovate, Inc.
Honoraria: None declared.
Research Funding: None declared.
Expert Testimony: None declared.
Role of Sponsor: The funding organizations played no role in the design of study, choice of enrolled patients, review and interpretation of data, or preparation or approval of manuscript.
- Received for publication June 16, 2010.
- Accepted for publication June 17, 2010.
- © 2010 The American Association for Clinical Chemistry