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Editorial

J. Nanotechnol. Eng. Med. 2012;3(2):020201-020201-5. doi:10.1115/1.4007616.

Nanoengineering, using the smallest possible material conformations and related technology, is now being used to successfully address some of the world's greatest problems. New approaches for energy conversion and storage, advanced materials and performance, and smaller, more powerful electronics have all benefited from nanoengineering breakthroughs. More recently, nanoengineering is delivering similar benefits in biomedical sciences and health care where nanoparticles (NPs) for diagnosis and therapy hold the most achievable and significant hope for future improvement.

Commentary by Dr. Valentin Fuster

SPECIAL SECTION: SIMULATION AND EXPERIMENTAL STUDIES AND APPLICATIONS OF CARBON NANOTUBES AND GRAPHENES IN ENGINEERING AND MEDICINE: Guest Editorial

J. Nanotechnol. Eng. Med. 2012;3(2):020902-020902-4. doi:10.1115/1.4007388.

The potential of carbon nanotubes (CNTs) as nanosensors in detection of genes through a vibration analysis is investigated with molecular dynamics. The carbon nanotube based nanosensor under investigation is wrapped by a gene whose structure includes a single strand deoxyribose nucleic acid (DNA) with a certain number of distinct nucleobases. Different genes are differentiated or detected by identifying a differentiable sensitivity index that is defined to be the shifts of the resonant frequency of the nanotube. Simulation results indicate that the nanosensor is able to differentiate distinct genes, i.e., small proline-rich protein 2 A, small proline-rich protein 2B, small proline-rich protein 2D, and small proline-rich protein 2E, with a recognizable sensitivity. The research provides a rapid, effective, and practical method for detection of genes.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2012;3(2):020903-020903-5. doi:10.1115/1.4007215.

Carbon nanotubes (CNTs) can be used as atomic force microscope (AFM) probes due to their robust mechanical properties, high aspect ratio and small diameter. In this study, a model of CNTs clamped in an elastic medium is proposed as CNT AFM probes. The buckling instability of the CNT probe clamped in elastic medium is analyzed based on the nonlocal Euler–Bernoulli beam model and the Whitney–Riley model. The clamped length of CNTs, and the stiffness of elastic medium affect largely on the stability of CNT AFM probe, especially at high buckling mode. The result shows that the buckling stability of the CNT AFM probe can be largely enhanced by increasing the stiffness of elastic medium. Moreover, the nonlocal effects of buckling instability are investigated and found to be lager for high buckling mode. The theoretical investigation on the buckling stability would give a useful reference for designing CNT as AFM probes.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2012;3(2):020904-020904-5. doi:10.1115/1.4007540.

Based on the concept of an energy pump, water transportation in a carbon nanotube (CNT) is studied by molecular dynamics simulations. The influences of CNT pretwist angle, water mass, environmental temperature, CNT diameter, CNT channel length, and CNT channel restrain condition on driving force and transportation efficiency are investigated. It is found that in order to initiate the transportation, the pretwist angle must be larger than certain threshold, 80 deg, for the case of one water molecule in a restrained (8,0) CNT. Furthermore, driving force decreases with increasing water mass and it is more efficient to transport multiple water molecules than one water molecules. The water molecule is found to have higher degrees of collisions in a (8,0) CNT in elevated environmental temperature. By comparing three CNT channel lengths, the channel length of 19.80 nm is identified as a faster and more efficient transporter in an unrestrained (8,8) CNT. Finally, molecular dynamics (MD) simulation indicates that a water molecule can only be transported below 300 K in an unrestrained (8,8) CNT due to the large friction caused by severely deformed channel and the Brownian motion.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2012;3(2):020905-020905-4. doi:10.1115/1.4007538.

The discovery of buckling instability and vibration of polyethylene (PE)/carbon nanotube (CNT) matrices is reported by molecular mechanics simulations. The buckling strains and the resonance frequencies are found to decrease with an increase in the number of polyethylene chains in the polyethylene/carbon nanotube matrices. The van der Waals forces between the polyethylene chains and the carbon nanotube in matrices are investigated to provide physical interpretations on the findings.

Commentary by Dr. Valentin Fuster

Research Papers

J. Nanotechnol. Eng. Med. 2012;3(2):021001-021001-6. doi:10.1115/1.4007044.

Effect of nanoparticle aggregation on the transport properties that include thermal conductivity and viscosity of nanofluids is studied by molecular dynamics (MD) simulation. Unlike many other MD simulations on nanofluids which have only one nanoparticle in the simulation box with periodic boundary condition, in this work, multiple nanoparticles are placed in the simulation box which makes it possible to simulate the aggregation of the nanoparticles. Thermal conductivity and viscosity of the nanofluid are calculated using Green–Kubo method and results show that the nanoparticle aggregation induces a significant enhancement of thermal conductivity in nanofluid, while the increase of viscosity is moderate. The results also indicate that different configurations of the nanoparticle cluster result in different enhancements of thermal conductivity and increase of viscosity in the nanofluid.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2012;3(2):021002-021002-6. doi:10.1115/1.4007245.

The objective of this paper is to demonstrate the use of gold nanoparticles, which accumulate in tumors due to the leakiness of tumor vasculature, as contrast agents for enhanced imaging in a time-resolved optical tomography system using short-pulse lasers for skin cancer detection in mouse model. It is found that intravenously administrated spherical gold nanoparticles broadened the temporal profile of reflected optical signals and enhanced the contrast between surrounding normal tissue and tumors. These results show that gold nanoparticles tuned to the wavelength of the laser can enhance the resolution and precision of laser-based cancer detection system.

Commentary by Dr. Valentin Fuster
J. Nanotechnol. Eng. Med. 2012;3(2):021003-021003-7. doi:10.1115/1.4007161.

In this study, in vivo animal experiments are performed on implanted xenograph prostatic tumors in nude mice to investigate enhanced laser energy absorption in the tumors by an intratumoral injection of gold nanorod solutions. In vivo temperature mapping of the tumors during laser photothermal therapy has shown the feasibility of elevating tumor temperatures higher than 50 °C using only 0.1 ml nanorod solution and a low laser irradiance of 1.6 W/cm2 incident on the tumor surface. The temperature profile suggests that normal tumor tissue still absorbs some amount of the laser energy without nanorod presence; however, the injected nanorods ensure that almost all the laser energy is absorbed and confined to the targeted tumors. The inverse relationship between the temperature elevations and the tumor size implies a relatively uniform spreading of the nanorods to the entire tumor, which is also shown by microcomputed tomography (microCT) imaging analyses. The feasibility of detecting 250 OD gold nanorod solution injected to the tumors is demonstrated via a high resolution microCT imaging system. Compared to other nanostructures, the gold nanorods used in this study do not accumulate surrounding the injection site. The relatively uniform deposition of the nanorods in the tumors observed by the microCT scans can be helpful in future study in simplifying theoretical simulation of temperature elevations in tumors during laser photothermal therapy.

Commentary by Dr. Valentin Fuster

Technical Briefs

J. Nanotechnol. Eng. Med. 2012;3(2):024501-024501-5. doi:10.1115/1.4006923.

Nanotechnology applications in medicine are poised to revolutionize the prevention, diagnosis, and treatment of disease. Researchers, scientists, and physicians across various disciplines and specialties are working to develop innovative clinical tools that incorporate materials, devices, and systems engineered at the nanoscale. Surgical specialties, such as orthopedic surgery, are among those developing nanotechnology applications for clinical use. Orthopedic surgery addresses disorders of the musculoskeletal system including repair by both surgical and nonsurgical means of tendons, ligaments, muscles, bones, and nerves injured due to trauma or disease. Medical interventions targeting orthopedic conditions are becoming increasingly important given current epidemiologic trends in these conditions. The purpose of this article is to highlight current and emerging applications of nanotechnology in orthopedic surgery. Selected, clinically relevant examples are described in the categories of drugs and drug delivery, imaging, sensors, biomaterials, diagnostics, and novel therapeutics. Several promising nanomedicine applications that target orthopedic conditions are in various stages of development from basic scientific research to clinical trials to product development and commercialization. Nanotechnology applications aimed at the prevention, diagnosis, and treatment of orthopedic conditions hold great promise for improving the standard of care in orthopedic surgery in the 21st century.

Commentary by Dr. Valentin Fuster

Review Articles

J. Nanotechnol. Eng. Med. 2012;3(2):025201-025201-7. doi:10.1115/1.4007761.

Propagation of Rayleigh traveling waves from a gas on a nanotube surface activates a macroscopic flow of the gas (or gases) that depends critically on the atomic mass of the gas. Our molecular dynamics simulations show that the surface waves are capable of actuating significant macroscopic flows of atomic and molecular hydrogen, helium, and a mixture of both gases both inside and outside carbon nanotubes (CNT). In addition, our simulations predict a new “nanoseparation” effect when a nanotube is filled with a mixture of two gases with different masses or placed inside a volume filled with a mixture of several gases with different masses. The mass selectivity of the nanopumping can be used to develop a highly selective filter for various gases. Gas flow rates, pumping, and separation efficiencies were calculated at various wave frequencies and phase velocities of the surface waves. The nanopumping effect was analyzed for its applicability to actuate nanofluids into fuel cells through carbon nanotubes.

Commentary by Dr. Valentin Fuster

Errata

J. Nanotechnol. Eng. Med. 2012;3(2):027001-027001-1. doi:10.1115/1.4007685.
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This article should have been included as the fourth article under the Special Section entitled “Simulation and Experimental Studies and Applications for Carbon Nanotubes and Graphenes in Engineering and Medicine.”

Commentary by Dr. Valentin Fuster

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