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| UCSD >> CHEMISTRY AND BIOCHEMISTRY >> SAILOR RESEARCH GROUP >> Research Projects
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RESEARCH SUMMARY: We synthesize nanomaterials and study their fundamental chemistry, photochemistry, electrochemistry, optical physics, and biomaterials properties. Our emphasis is on porous silicon and iron oxide nanoparticles. Research topics involve drug delivery materials, chemical and biochemical sensors, and in-vivo imaging with fluorescent or magnetic nanoparticles. |
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Current projects Prof. Sailor's book "Porous Silicon in Practice" is now available from Wiley-VCH
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| Although the scope of our work at the University is limited to basic research into the fundamental properties of materials, many of the concepts developed in our labs have been translated to products and processes in the commercial world. Any commercial products and processes that emerge from our fundamental discoveries are outside the course and scope of our University-related employment; however, we actively encourage transition of technologies to the commercial sector with the assistance of UCSD’s technology transfer office. | |
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  Magnetic Iron Oxide Nanoworms for Tumor Targeting and Imaging. These nano-worms are made of magnetic iron oxide (magnetite) coated with a polymer. The wormlike structure and a speciallized coating allows these nanodevices to find and attach to tumors. Photos: Ji-Ho Park |
Multifunctional Magnetic Nanoparticles for in vivo Imaging |
| NIH-Bioengineering Research Partnerships, NIH CCNE Nanotechnology in Cancer Center, the Moores UCSD Cancer Center and the UCSD NanoTUMOR Center, supported by NIH grant U54 CA 119335r | |
The goal of this project is to synthesize new nanomaterials that can be used to allow the early diagnosis and effective treatment of cancer. We are engineering multifunctional nanoparticles based on iron oxide (and more recently, manganese oxide and bismuth sulfide) that exploit biological processes to guide the targeting and accumulation of these materials to image tumors in mouse models of cancer. The multidisciplinary team is led by MIT Bioengineering professor Dr. Sangeeta Bhatia, and it also includes tumor biologist Dr. Erkki Ruoslahti of the Burnham Institute at UC Santa Barbara. Our group invented a new synthesis of iron oxide nanoparticles that results in a worm-like morphology. In collaboration with Erkki Ruoslahti’s group at the Burnham Institute and Sangeeta Bhatia’s lab at MIT, we placed short peptide moieties on these nanoworms that demonstrated effective targeting to tumors and other tissues. We found that the nano-worms circulate in mice for > 24 hours—almost 100 times longer than any of the commercially available or previously published iron oxide nanoparticle systems. Because of their significantly improved ability to circulate in the body and the higher contrast they display in MRI images relative to conventional iron oxide nanoparticles, this nanoworm synthesis has been duplicated and used by many other researchers for in-vivo imaging of tumors and for delivery of various therapeutics. Our 2008 Advanced Materials paper describing this work was selected by the editors as the "Best work published in Advanced Materials in 2008" based on feedback from reviewers, citations, and the number of full-text downloads. Publications: Maltzahn, G. v.; Park, J.-H.; Lin, K. Y.; Singh, N.; Schwöppe, C.; Mesters, R.; Berdel, W. E.; Ruoslahti, E.; Sailor, M. J.; Bhatia, S. N., "Nanoparticles that communicate in vivo to amplify tumour targeting." Nature Mater. 2011, 10, 545–552. Park, J.-H.; Maltzahn, G. v.; Zhang, L.; Derfus, A. M.; Simberg, D.; Harris, T. J.; Bhatia, S. N.; Ruoslahti, E.; Sailor, M. J., "Systematic Surface Engineering of Magnetic Nanoworms for in vivo Tumor Targeting." Small 2009, 5, (6), 694-700. Researchers: Matt Kinsella, Joel Grondek |
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  Top: Luminescent porous silicon nanoparticles in a vial. The vial is being illuminated with an ultraviolet ("black") light, and the bright red-orange photoluminescence is observed. Bottom: TEM image of a porous Si nanoparticle embedded with iron oxide nanoparticles. Scale bar is 50 nm. Prepared from high-purity silicon wafers, these nanoparticles provide a non-toxic and biodegradable alternative to conventional quantum dots for drug delivery and medical diagnostic applications. Photo Credits: Luo Gu, Ji-Ho Park, Matt Kinsella, UCSD |
Porous Silicon Nanoparticles Targeted to Tissues |
| Moores UCSD Cancer Center http://cancer.ucsd.edu/aboutus/news/ccbrowser/ccbrowser.asp |
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| The goal of this project is to construct non-toxic, environmentally and systemically benign nanoparticles based on silicon that are capable of homing to diseased tissues in the body and delivering therapeutic or imaging agents. We focus on nanostructured porous particles composed primarily of silicon or silicon oxides. The porous silicon-based scaffolding provides a number of advantages: (1) The photoluminescence features provide a non-toxic, time-dependent imaging modality; (2) The nanoporous carrier has a high capacity for drug or other payloads (typical loadings of 10% by mass); (3) Nanophase silicon shows a high degree of biocompatibility and bioresorbability; (4) The nanoparticles can be modified with multiple tissue-specific homing peptides for multivalent targeting; and (5) The release of nanoparticles, drugs, or imaging agent payloads can be triggered by oxidative degradation, hydrolysis, or enzymatic degradation of the carrier matrix.
Publications: Park, J.-H.; Gu, L.; Maltzahn, G. v.; Ruoslahti, E.; Bhatia, S. N.; Sailor, M. J., "Biodegradable luminescent porous silicon nanoparticles for in vivo applications." Nature Mater. 2009, 8, 331-336. Researchers: Luo Gu, Nobuhiro Yagi |
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Nanosensors Using Porous Photonic Crystals |
| NIOSH/NPPTL | |
| We are developing the basic science to enable chemical microsensors, with a specific focus on monitors for personal and collective protection equipment for breathable air. One targeted outcome of the work is small, low-power chemical detectors for volatile organic compounds (VOCs) suitable for insertion into activated carbon respirator cartridges as end-of-service-life (ESLI) or residual life (RLI) indicators. We have developed an extrinsic sensor for VOCs by adhering a 0.5 mm-diameter nanostructured porous silicon photonic crystal to an optical fiber. The approach relies on porous silicon-based photonic crystals modified such that they present a high surface area matrix with a high affinity for the indicated compounds. We have demonstrated their ability to act as chemical indicators for VOCs, explosives, and CW agents. When modified with a hydrophobic carbon-like porous matrix, the photonic crystals change color in the presence of a broad class of chemical agents and VOCs at sub-ppm concentrations, and are thus well suited as low-power indicators of chemicals in the respirator environment. The materials can be autonomously monitored with a low-power LED–based optical interrogation subsystem. This project is a close collaboration with Dr. Jay Snyder at NIOSH. Kelly, T. L.; Gao, T.; Sailor, M. J., "Carbon and Carbon/Silicon Composites Templated in Microporous Silicon Rugate Filters for the Adsorption and Detection of Organic Vapors." Adv. Mater. 2011, 23, 1776–1781. Ruminski, A. M.; King, B. H.; Salonen, J.; Snyder, J. L.; Sailor, M. J., Porous silicon-based optical microsensors for volatile organic analytes: effect of surface chemistry on stability and specificity. Adv. Funct. Mater. 2010, 20, 2874–2883. King, B. H.; Ruminski, A. M.; Snyder, J. L.; Sailor, M. J., "Optical fiber-mounted porous silicon photonic crystals for sensing of organic vapor breakthrough in activated carbon," Adv. Mater. 2007, 19, 4530. |
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Waveform encoded into a porous Si photonic crystal. The cross-sectional electron microscope image displays the porous nanostructure that was generated using the current-time waveform depicted at the left. Image credit: Shawn O. Meade. |
Spectrally Barcoded Microparticles |
| NSF DMR-0806859 | |
| The goal of this project is to construct encoded particles that act as robust, non-toxic taggants. The tags are in the form of microscopic particles containing an elaborate nanostructure that is programmed during electrochemical synthesis to display a complex reflectivity spectrum, referred to as a “Spectral Barcode." The reflectivity spectrum can be decoded using simple, low-power optical spectrometers. We are developing these materials for various applications in high throughput screening and encoded bead-based assays.
References: Meade, S. O.; Yoon, M. S.; Ahn, K. H.; Sailor, M. J., "Porous silicon photonic crystals as encoded microcarriers." Adv. Mater. 2004, 16, (20), 1811-1814. Meade, S. O.; Sailor, M. J., "Microfabrication of freestanding porous silicon particles containing spectral barcodes." phys. stat. sol. (RRL) 2007, 1, (2), R71–R73. |
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 Porous Si microparticles injected into rabbit eye. Image credit: Dr. Lingyun Cheng, Jacobs Retina Center. |
Drug Delivery with Porous Silicon Microparticles |
| Whereas systemic administration (by IV injection) is the focus of much of our nanoparticle work, the objective of the microparticle-based drug delivery project is locallized injection into the target organs, such as the eye or peritonneal cavity. The micron-scale vehicles are based on nanostructured porous Si, and the approach involves infusion of a molecule into a chemically modified matrix of nanocrystalline porous Si or SiO2. Drugs such as the anti-inflammatory dexamethasone, the antibiotic vancomycin, and the analgesic ibuprofen are being incorporated into these microscopic particles. The larger sized porous Si microparticles allow the loading of much larger quantities of drug, appropriate for long-term (>4 month) therapies. We are developing chemistries to cap the pores with noble metals, polymers, proteins, and silica derived from silanols, to allow for the slow release of drug under appropriate physiological conditions. The work encompasses new methods of trapping molecules into porous nanostructures, and new methods of monitoring the porous nanostructures using the optical properties of the materials. In particular, we have developed one-dimensional photonic crystals whose spectral signatures can report on the amount or type of drug contained within. Our European partners for this effort are Drs. Frederique Cunin and Jean-Olivier Durand of the CNRS Institut Charles Gerhardt in Montpellier, France. The Montpellier lab has played a major role in the development and commercialization of liposome- and silica-based drug delivery materials. The collaboration involves significant student exchange with UCSD students visiting the Montpellier labs or Montpellier students visiting UCSD for several months each year.
Wu, E. C.; Andrew, J. S.; Buyanin, A.; Kinsella, J. M.; Sailor, M. J., Suitability of porous silicon microparticles for the long-term delivery of redox-active therapeutics. Chem. Commun. 2011, 47, 5699–5701. Gu, L.; Park, J.-H.; Duong, K. H.; Ruoslahti, E.; Sailor, M. J., Magnetic Luminescent Porous Silicon Microparticles for Localized Delivery of Molecular Drug Payloads. Small 2010, 6, 2546-2552. Orosco, M. M.; Pacholski, C.; Sailor, M. J., "Real-time monitoring of enzyme activity in a mesoporous silicon double layer." Nature Nanotech. 2009, 4, 255 - 258. |
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 A porous silicon double-layer interferometer contains two porous layers: one with large pores on top of one with small pores. These layers can discriminate molecules based on size, and the optical response of the film provides a self-compensating sensing function. Photo credit: Claudia Pacholski |
Separating, Processing, and Detecting Biomolecules in Silicon-Based Optical Nanostructures: Multifunctional Biosensors |
| There is a major unmet need for microsensor technologies that can provide rapid and reliable identification and quantification of biological species in air, water, and patient samples. The objective of this project is to develop the fundamental materials science and chemistries needed to enable label-free biosensors that have the ability to perform separation, identification and quantification of key properties of biomolecules at low concentrations. We aim to develop new, unprecendented levels of selectivity and discrimination in optical biosensors by exploiting molecular transport through chemically functionalized and physically engineered porous Si matrices. A key innovation of the present proposal that is not represented in the vast majority of existing optical biosensor work is that the sensor is the same physical entity that is performing analyte separation and isolation. We refer to this approach as “signal processing at the materials level,” and we believe it is an important theme for the general area of functional nano materials. | |
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  Single magnetic porous silicon microparticle delivers a nanogram payload. Delivery of horseradish peroxidase (contained in microparticle indicated by the arrow) to a droplet containing a colorimetric enzymatic substrate is accomplished by manipulation of the particle using a small magnet. This methodology presents an alternative to channel-based microfluidic systems. Thomas, J. C., Pacholski, C. & Sailor, M. J. "Delivery of Nanogram Payloads Using Magnetic Porous Silicon Microcarriers." Lab Chip 2006, 6, 782 - 787. |
Smart Dust: Manipulation of Chemicals, Biochemicals, and Cells with Porous Si Chaperones |
| NSF-Division of Materials Research (NSF-DMR 0806859) | |
| One of the challenges faced by nanotechnology involves the manipulation of minescule amounts of liquid. There is an increasing need to do this, as the required time and cost of many medical and environmental analyses is directly proportional to sample volume. Fifteen years ago, the concept of the "lab on a chip" evolved as a marriage of the methods used by analytical chemists and microbiologists with the tools developed in the semiconductor industry for microfabrication. In the world of microfluidics, the bucket is often preferable to the pipe; as the sample volume becomes smaller, the number of molecules that stick to the insides of a microchannel becomes a significant fraction of the total molecules in the sample. This problem spawned the so-called "lab-on-a-drop" concept. A sphere has the lowest ratio of surface area to volume, and if a droplet containing the sample of interest can be manipulated without it coming into contact with the walls of its container, the amount of material lost can be minimized. In this project, we use micron-sized, nanostructured particles of porous Si as manipulators. The particles can carry a nano payload or surround a much larger liquid droplet. The particles contain superparamagnetic iron oxide, and application of a magnetic field allows them to be manipulated. The method provides a general means for manipulating small volumes of liquids without a microfluidic container or use of a pump.
Publications: Researchers: Chia-Chen Wu |
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| Main address: Department of Chemistry, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0358 Send questions, comments, and suggestions to: msailor@ucsd.edu. |
Porous Si photonic crystal chemical agent sensors. Roughly the size of the diameter of a human hair, these particles change color in the presence of volatile organic compounds. Photo credit: Anne Ruminski and Brian H. King.