Session X15: Emerging Nano-based Diagnostics and Therapeutics: Approaches to Cancer Treatment

Intracellular Mechanics-Based Drug Screening for Cancer Metastasis

In 2007 alone, close to 1.5 million new cancer cases and over half of a million deaths from cancer are projected to occur in US. In general, cancer is much easier to be successfully treated before metastasis; the five-year survival rates for most of the cancers in the metastatic stage are lower than 10\%. The origin of cancer is due to genomic instability; however, the genomics or proteomics studies focus on this phenomenon cannot thoroughly elucidate how cancer metastasis proceeds. During this process, cancer cells protrude and conquer their physical barriers, resist shear stress, establish anchorages and finally settle in a new environment. Each development in this process involves mechanical forces. Thus, whether force generation and cancer cells' mechanical properties can be integrated into the current mainstream of cancer research and offer new insight is worthy of being investigated. To measure the change of cell mechanics, specifically intracellular mechanics, a tool that least disrupts the probed cell's behavior and, simultaneously, can obtain real time quantitative measurement is necessary. To satisfy these criteria, we have developed a technique, ballistic intracellular nanorheology (BIN), in which we trace and analyze the trajectories of nanospheres that have been ballistically bombarded into the cytoplasm of individual cells. This technique allows us to probe the effects of chemical or mechanical stimuli on intracellular mechanics in various types of cells, on culture dishes or in a three-dimensional matrix. BIN is, currently, the first and only method available that can be applied to perform such tasks. Using this technique, we have gained detailed information about how the cytoskeletal remodeling pathways control the intracellular mechanics. We have also obtained information on the tempo-correlation between agonists and intracellular mechanics and how cells utilize their intracellular mechanics to react extracellular shear stress. These studies have set the framework for us to understand the mechanical mechanism of cancer cell metastasis on a molecular level. In this talk, I will describe the working principal using this technique to screen cancer drugs that prevent cancer metastasis.   

Targeted Multifunctional Nanoparticles cure and image Brain Tumors: Selective MRI Contrast Enhancement and Photodynamic Therapy

Aimed at targeted therapy and imaging of brain tumors, our approach uses targeted, multi-functional nano-particles (NP). A typical nano-particle contains a biologically inert, non-toxic matrix, biodegradable and bio-eliminable over a long time period. It also contains active components, such as fluorescent chemical indicators, photo-sensitizers, MRI contrast enhancement agents and optical imaging dyes. In addition, its surface contains molecular targeting units, e.g. peptides or antibodies, as well as a cloaking agent, to prevent uptake by the immune system, i.e. enabling control of the plasma residence time. These dynamic nano-platforms (DNP) contain contrast enhancement agents for the imaging (MRI, optical, photo-acoustic) of targeted locations, i.e. tumors. Added to this are targeted therapy agents, such as photosensitizers for photodynamic therapy (PDT). A simple protocol, for rats implanted with human brain cancer, consists of tail injection with DNPs, followed by 5 min red light illumination of the tumor region. It resulted in excellent cure statistics for 9L glioblastoma.   

Microcantilever Biosensors

Micromachined cantilever beams respond to molecular adsorption by with mechanical bending. For small concentrations, the bending signal is directly proportional the surface concentration of adsorbed molecules. Selectivity in detection is accomplished by immobilizing specific receptors on one of the surfaces of the cantilever. We have developed microcantilever arrays for multiplexed, label-free detection of biomolecules. Piezoresistive readout of cantilever bending offers a simple method of signal transduction that is compatible with microfabrication. Although the microcantilever-based biosensing appears to high sensitivity and selectivity, reproducibility of the technique appears to be a challenge. We have developed a novel method of immobilizing receptors that increases the reproducibility. We have demonstrated simultaneous detection of cancer and cardiac markers using cantilever arrays with immobilized receptors. We will also discuss a receptor-free mode of achieving selectivity.   

Magnetic sifters and biochips for early diagnosis and therapy monitoring of cancer

Magnetic nanoparticles conjugated with biomolecules or recognition moieties are finding wide applications in medicine. In this context, we are developing a micromachined magnetic sifter and magnetic nanoparticles aimed for sample preparation applications in early diagnosis of cancer. The microfabricated sifter consisting of arrays of micron sized slits etched through a silicon wafer. A magnetic film is deposited on the wafer, producing high magnetic field gradients, comparable in magnitude to gradients in planar flow devices. As the solution flows through the die, magnetic particles are captured by the magnetic material surrounding the slits. The large number of slits allows for processing of large volumes of liquid, much greater than that of planar microfluidic devices. The sifters can be simply attached to a syringe or tube, resulting in a portable and user-friendly tool for molecular biology. Separation efficiencies of $\sim $ 50{\%} for one pass through the sifter have been achieved. We have also designed and fabricated several types of magnetic biochips consisting of arrays of giant magnetoresistive (GMR) spin valve detectors with appropriate dimensions, surface chemistry, and microfluidics. An advanced electronic test station has been set up as a demonstration vehicle for the integrated evaluation of our magnetic biochips with commercial and custom magnetic nanoparticle labels for DNA or protein biomarkers. The magnetic biochip is capable of detecting down to 1-30 nanotags. Real-time detection of DNA signatures and protein targets in buffer and serum samples has been successfully performed in our laboratories, suggesting that magnetic biochips hold great promises for molecular diagnostics of cancer and other diseases. In collaboration with Chris M. Earhart, Wei Hu, Robert J. Wilson, Sebastian J. Osterfeld, Robert L. White, Nader Pourmand, and Shan X. Wang @ Stanford University. This work was supported by grants from NIH (1U54CA119367-01) and DARPA/Navy (N00014-02-1-0807).   

Microdevices for biomolecular detection and single cell analysis

Recent advances towards developing biomolecular and single cell applications for a mass-based biosensor known as the suspended microchannel resonator (SMR) will be presented. In SMR detection, target molecules or cells flow through a vibrating suspended microchannel and are captured by receptor molecules attached to the interior channel walls. What separates the SMR from the existing resonant mass sensors is that the receptors, targets, and their aqueous environment are confined inside the resonator, while the resonator itself can oscillate at high Q in an external vacuum environment, thus yielding extraordinarily high sensitivity. This approach solves the problem of viscous damping that degrades the sensitivity of cantilever resonators in solution. We have achieved a resolution of approximately 1 femtogram (1 Hz bandwidth) which is represents an improvement of six order of magnitude improvement over a high-end commercial quartz crystal microbalance. This gives access to intriguing applications such as mass based flow cytometry, real-time monitoring of single cell growth, and the direct detection of protein biomarkers.