The objective of this research is to demonstrate that a high resolution magnetic multiplexed bioseparation can be achieved by using multilayered magnetic nanodisks as labels. This new magnetophoretic approach allows a continuous separation of sub-100 nm sized magnetic nanodisks according to their distinct magnetic properties. Intellectual Merit: The proposed multilayered nanodisks, consisting of two magnetic layers separated by a non-magnetic layer with two capping layers, can provide a wide-range tunability of magnetic properties, which results in two important advantages over commonly used superparamagnetic iron oxide nanoparticles: opening up the new possibility of magnetic multiplexing and filling the superparamagnetic nanoparticle size gap, from 30 nm to 200 nm, to provide high-moment magnetic labels for bioseparation. In a microfluidic arrangement, these nanodisks will be subjected to a magnetic field varying with time in a triangle wave format. Nanodisks with different saturation fields can be continuously separated. Since magnetic properties of labels and magnetic fields are exactly known, the whole separation process can be easily modeled, which will provide us a convenient tool to optimize conditions for different kind of separations. Broader Impacts: Separation is an important part of any biochemical analysis. The proposed separation method mimics widely-used electrophoresis, but replacing electric field with magnetic field. Magnetic field does not interfere with biological process and materials, and can be applied externally without physical contact between magnet and any liquid. Magnetic forces are independent on ionic strength, pH or surface charges. It can be seen that this proposed approach, if successful, will provide an important alternative for bioseparation. Moreover, it can introduce valuable multiplexing into many highly sensitive detection methods for biosensing. Both of these will have a broad impact in many biological and biomedical research fields. Also, this project offers an outstanding venue to integrate research activities with the education and training for college and graduate students in nanobiotechnology, which is considered as one of the most potentially valuable technologies for U.S. in the global economic competition and for national security. Three experiment modules will be created for a new practicum approach on undergraduate nanobiotechnology teaching; ?experiment-oriented just-in-time teaching?. In addition, through three existing summer camps at UT Arlington, several hundreds of K-12 students will be exposed to this research. Among them, about thirty percent are Hispanic students. The students will certainly be affected positively and may spark their interest in science and engineering.
Separation is an important part of any biochemical analysis. In this project, a new type of separation method is proposed, which mimics widely-used electrophoresis, but replacing the electric field with the magnetic field. A magnetic approach provides several important advantages over electrical ones, including: magnetic fields do not interfere with biological processes and materials, and can be applied externally without physical contact between magnets and any liquid and magnetic forces are independent on ionic strength, pH or surface charges. The realization of a continuous magnetic separation (termed as magnetophoresis) is largely dependent on the availability of magnetic nanoparticle labels with tunable magnetic properties. In this project, we designed and fabricated a new type of magnetic nanoparticles: multilayered magnetic nanodisks. This nanodisk consists of two magnetic layers (Co and NiFe) separated by a non-magnetic Au layer with two anchorage Au layers (see Figure 1). Such nanodisks can provide wide-range tunability of magnetic properties, and are ideal labels for magnetophoresis. Templated growth methods have been chosen to produce these multilayered magnetic nanoparticles. The general processes are illustrated in Figure 2. First, a sacrificing layer is deposited at the bottom for releasing the mutilayer nanodisks into solution. Different materials will be either electrodeposited or vacuum evaporated into template holes. The templates will be dissolved to release the nanorods into solution. This templated growth process is crucially dependent on the development of low-cost large area templates with nano-scale holes. Anodic alumina templates meet such requirements. First, we developed an anodization process to generate ultra-thin anodic alumina templates on silicon substrates. We found that evaporated ultra-thin (~100 nm) Aluminum films on Si substrate can be anodized in oxalic acid at a potential of 40V at room temperature. A widening process using a 10% phosphoric acid solution resulted in the formation of holes with a diameter around 50 nm. The anodized film stick well to the Si substrate and can be used as evaporation templates for formation of nanodisks (see Figure 3). The shape of holes changed from "bottleneck" to straight holes as widening time changes from 30 minutes to 40 minutes. The bottleneck-shaped templates can be utilized to simultaneously produce both nanodisks and truncated hollow nanocones by evaporation of metals into the holes followed by the dissolution of the templates (see Figure 3). Using this template, we have fabricated multilayered magnetic nanodisks with different spacing layer thicknesses. The magnetic measurement of these nanodisks demonstrated that the designed magnetic properties of nanodisks have been achieved, including high moment, low remanence and tunable saturation field. For the mass production of multilayered magnetic nanodisks, electrochemical deposition into nanoscale channels inside anodic alumina membranes was adopted (as shown in Figure 1.) In such method, many multilayered nanodisks can be produced in one channel in membranes. This is a feasible cost-effective method. Using this method, the diameter of the nanodisks is determined by the channel diameter of the AAO membranes. Currently, the commercial available AAO membranes all have a channel diameter about 300nm. This has become a limiting factor for our mass production of multilayered magnetic nanodisks. To overcome this limitation, we developed a AAO membrane fabrication process, which can provide us AAO membranes with channel diameter less than 100nm. We have developed the electrodepostion process to deposit NiFe into AAO channels (see Figure 4). Also we developed a process to deposit Co/Au bilayers into AAO channels using an electrolyte containing both Au and Co ions (see Figure 5). By simply changing deposition potential, Co and Au layers can be deposited, respectively. In summary, we designed a new type of magnetic nanoparticle, multilayered magnetic nanodisks, suitable as labels for magnetophoresis. We developed the entire process to massively produce such magnetic nanoparticles. The developed magnetic nanodisks can also be utilized in other biomedical applications. We have found that such nanodisks can act as enhancement agents for radiation therapy of cancers, and we are currently conducting research to fully explore this possiblity. They can also be used as magnetic resonance imaging contrast agents of diagnosis of cancers. This project provided an outstanding venue to integrate research activities with the education and training for college and graduate students in nanobiotechnology. Also, it gave us a unique opportunity to spark the interests of K-12 students in science and engineering. From this project, we have created three experiment modules for experiment-oriented course, "Nanoscale Materials", which was offered in every spring semester. Every year, about 15 students took the course. Every year, we participated in three summer camps. About 25 to 30 students from 4th grade to 8th grade got into our lab, and exposed to the research activities related to this project.
