Dendritic Magnetic Nanostructures for Anti-Bacterial Biomedical Applications Revealed by University of Louisiana Scientist

University of Louisiana at Lafayette (Lafayette, LA) Professor of Metallurgy Dr. Devesh K. Misra discloses how to make dendritic magnetic nanostructures for use in medical, sensor, drug delivery and magnetic recording applications in U.S. Patent 7,635,518.  Dendrites are typically the tree-like structures, examples of which include crystals that grow as molten metal freezes; the tree-like structures that form during the freezing of many nonmetallic substances such as ice; and the like. Dendrites are sometimes referred to as having a "spiky" morphology.

Each nanorod of the dendritic magnetic nanostructure is comprised of a chain of nanoparticles that are held together by dipole interaction during their formation by precipitation within the aqueous core of a reverse micelle when an effective magnetic field is applied. Each nanoparticle is comprised of at least two elements, one of which is a magnetic metal. 

Misra prepares dendritic magnetic nanostructures at room temperature by applying a magnetic field to a reverse micelle system wherein at least one salt of a magnetic metal is being precipitated within the core of the reverse micelle.

Quasi one-dimensional magnetic nanostructures, such as nanorods, nanowires, and nanotubes have attracted significant scientific and technological interest because they exhibit unique magnetic properties not displayed by their bulk or nanoparticle counterparts. Crystalline magnetic nanorods belong to this class of magnetic materials known for their spontaneous magnetization. There are multiple potential uses for such nanostructures, such as: their use for high density magnetic recording media; their use in sensors; their use in spintronic devices, and their use in drug delivery applications.

Misra also created titania coated magnetic nanostructures that are suitable for use in biomedical applications because the photocatalytic properties of the titania can be exploited for antimicrobial, or germicidal, activity. The magnetic properties of the nanorods are used to remove the titania coated nanostructures, when applied to the human body, such as when applied to a wound.

A variety of methods have been proposed for synthesizing various types of nanorods. These synthetic methods are typically anisotropic growth with the intrinsic anisotropic crystal structure in a solid material, anisotropic growth using tubular templates, and anisotropic growth kinetically controlled by super-saturation or by using an appropriate capping surfactant. Other approaches to fabricate one-dimensional nanostructures include thermal evaporation and template assisted growth, vapor phase transport process with the assistance of metal catalysts, hydrothermal methods, and electrospinning.

Misra’s method for producing magnetic nanostructures is comprised of an assembly of magnetic nanorods held together by dipole interaction in a dendritic pattern, includes the following steps:

a) dissolving an effective amount of a surfactant into a non-polar organic solvent with sufficient mixing to cause the formation of a reverse micelle microemulsion;

b) dividing said reverse micelle microemulsion into a first fraction and a second fraction;

c) blending into said first fraction an aqueous solution having dissolved therein one or more metal salts wherein at least one of the metals has magnetic properties, thereby forming a metal salt microemulsion comprised of reverse micelles in a continuous non-polar organic phase, which reverse micelles are comprised of an aqueous core of metal salt solution encased in a surfactant shell;

d) blending into said second fraction an effective amount of an aqueous precipitating agent solution, thereby resulting in the formation of a precipitating agent microemulsion comprised of reverse micelles in a continuous non-polar organic phase, which reverse micelles are comprised of an aqueous core of precipitating agent solution encased in a surfactant shell;

e) simultaneously: (i) applying a magnetic field of effective strength; and (ii) blending at least a portion of the metal salt microemulsion with at least a portion of the precipitating agent microemulsion, thereby resulting in the simultaneous precipitation and formation of magnetic nanostructures comprised of an assembly of magnetic nanorods held together by dipole interaction in a dendritic pattern, which nanorods are comprised of a series of magnetic nanoparticles held together by dipole magnetic forces, in the aqueous core of said reverse micelles;

f) extracting at least a portion of the magnetic nanostructures with an effective amount of a C₂ to about a C₆ alcohol wherein the magnetic nanostructures migrate to the alcohol phase in the form of a colloidal dispersion alcohol phase;

g) separating the colloidal dispersion alcohol phase from the non-polar organic phase; and h) heating said colloidal dispersion alcohol phase of step g) above at an effective temperature for an effective amount of time to drive off at least a portion of any remaining water and surfactant, thereby resulting in substantially dried magnetic nanostructures comprised of assemblies of magnetic nanorods held together in a dendritic pattern by dipole interaction.

Nanoparticles that can comprise the nanorods include M-Au, M-Ag, M-Pt, M-Pd, M-Au--Pt, M-Sm, and Nd-M-B wherein M is a magnetic metal selected from iron, nickel and cobalt.

Harvard Offers License for Universal Platform for Drug Delivery Via Vertical Silicon Nanowires

Vertical silicon nanowires as a universal platform for highly efficient delivery of bioactive molecules into living cells have been developed by Harvard scientists Hongkun Park,  Marsela Jorgolli, JinSeok Lee, Jacob Robinson, Alex Shalek, Amy A Sutton,  EunGyeong Yang, and Myung-Han Yoon and are offered for license by the University Office of Technology Development.

This platform consists of an array of surface-modified vertical silicon nanowires that have been chemically grown or etched on a wafer and to which virtually any kind of bioactive species (drug, protein, nucleic acid, nanoparticles) may be attached by covalent or electrostatic means. When cells are plated on the surface of the array, they are penetrated by the functionalized nanowires, and the bioactive material is thus efficiently delivered into the cytosol of the cells. Since the cells remain viable after penetration, the effects of the delivered material on the cells can be monitored over time.

Existing strategies for delivering exogenous materials into cells (e.g., viral vectors, physio-chemical means, or microinjection) are limited either by the range of chemical and biological species that each can deliver, or by the efficiency or throughput of the delivery. While there have been previous efforts to use nanostructured materials to introduce bioactive species into cells, they too have been inefficient and generally limited to the delivery of genetic material.

The potential to deliver a wide range of molecules at sites of one’s choosing lends itself to a broad variety of implementations, including the following:

1. Massive, parallel screening for drug discovery: the cellular effects of many proteins (proteomics), siRNAs (knockdown efficacy), and small molecules (drug/antibiotic resistance) may be assayed simultaneously, either singly or in combinations; by perturbing different elements of a particular cellular pathway, the causal relationships between those elements can be discovered.

2. Cell-based ADME/Tox assays: the concentration-dependent effects of a particular protein, drug, and/or combinations can be studied in cell-based assays.

3. Derivation of induced pluripotent stem (iPS) cells: the platform is suitable for efficiently delivering (and discovering) molecules capable of reprogramming adult cells into iPS cells.

4. Designer cell networks and disease models: the platform can be used to construct complex cellular systems, such as synaptic pairs of differentially perturbed neurons for modeling neurodegenerative diseases.

5. Assays of epigenetic factors: the platform could be used to discover molecules that usefully affect the differentiation and development of any set of cells (e.g., stem cells, iPS cells, or differentiated tissues), and then further used to generate cells of a particular lineage for use in cell-based therapies.

By optimizing the cell-nanowire interface through the use of novel surface chemistry and the precise control over nanowire density, diameter, and height, investigators in the laboratory of Chemistry and of Physics Professor Professor Hongkun Park at Harvard University have created a platform suitable for delivering a wide range of materials (including small molecules, nanoparticles, siRNAs, and proteins) into living cells in a highly efficiently, massively parallel, arrayed fashion. There are three general steps involving to implement the procedure:

1. The nanowires are fabricated by either growing them from a precursor material on the surface of a patterned substrate, or by etching the structures out of a substrate material from the top down.

2. The surface of the nanowires is then chemically treated to facilitate their electrostatic linkage to the compound of interest. (Covalent linkage strategies may also be employed.)

3. The compound of interest is then tethered to the nanowire by pipetting a few uLs of a solution containing the compound atop the nanowires. Microarraying techniques may also be used for the multiplex deposition of an assortment of molecular species. Once the solvent evaporates, the nanowire wafer may be used immediately or stored until needed.

4. Cells are then plated on the nanowire surface. As they settle, they are impaled by the wires (typically within an hour) and the electrostatically linked agent detaches from the wires and is thus released into the cell cytosol.

This single platform has been shown to be able to deliver small molecules, nanoparticles, RNAs, peptides, and proteins, into a number of primary and clonal cell with an efficiency greater than 95%. It should be noted that the Park laboratory has been able to mass-produce the wires on six-inch silicon wafers using a technique that could easily be implemented by any semiconductor foundry. The high-throughput, low-cost production of these silicon wafer arrays using widely available semiconductor processing should enable the wide adoption and rapid commercialization of this technology.

Intellectual Property Status: A patent application is pending.

Publications:

"Vertical silicon nanowires as a universal platform for delivering biomolecules into living cells," A. Shalek, J. T. Robinson, E. S. Karp, J. S. Lee, D-R. Ahn, M-H. Yoon, A. Sutton, M. Jorgolli, R. S. Gertner, T. S. Gujral, G. MacBeath, E. G. Yang, H. Park, submitted (2009).

For further information, please contact:

Bob Benson, Director of Business Development

(617) 496-3830

Email: robert_benson(at)harvard.edu, Harvard Reference: 3211

RF Hand Hygiene Monitoring System Proposed to Quell $36 Billion Hospital Acquired Infections Problem

A radio frequency (RF) system could optimize the compliance by workers in handwashing in the effort of reducing cross infections that occur frequently in health care settings, food service and food processing facilities, hotels, cruise lines, spas/fitness centers/gyms, schools and homes.

Ching Ching Huang (Glendora, CA), Jennifer Peng (Huntington Beach, CA), Francine N. Hwang (Los Angeles, CA) developed a hand hygiene monitoring system that can identify the personnel, the frequency of his/her handwashing and hand cleaning with rinse-free disinfectant as well as the thoroughness of his/her handwashing effort each time The wrist band or the integral band carrying the wrist watch sized transmitter can be composed with material impregnated with very small (such as nano size) silver particles as an antibacterial agent to allow the band to remain germ-free, according to U.S. Patent Application 20090195385.

According to the publications of U.S. Center for Disease Control and Prevention (CDC), more than 2 million patients annually are inflicted in U.S. hospitals with hospital acquired infections (HAI), such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), Clostridium difficile, etc., and every year more than 80,000 patients (one every 6 minutes) die from these complications. More than 36 billion dollars loss a year can be attributed to HAI, and this number does not count the suffering of the patients and liability law suits.

By using an identification tag to collect the handwashing and cleaning data, it will proactively remind the wearer to undergo handwashing or cleaning as required to reduce propagation of infection. Furthermore, by using a unique identification method to accurately link the person conducting a hand hygiene event and by further linking all the identification tags with a central data processor, this invention can accurately report the compliance of workers to the hand hygiene guidelines issued by many governmental agencies and institutions, such as hospitals, nursing care facilities, outpatient clinics, food processing/delivery entities to reduce the incidences and costs resulting from cross infection by unclean hands.

The U.S. Department of Agriculture estimates that annually more than 79 million Americans suffer from food borne illnesses due to infectious germs, like, E Coli salmonella, hepatitis, etc., and hundreds of thousands require hospitalization. Again, billions of dollars in medical expenses and loss of business resulted yearly. Similar conditions occur in the hotel, spa, fitness center and cruise line industries, where infectious germs are propagated by clients and staff unknowingly through contacts or unclean surfaces.

The single most effective mean to stop or greatly reduce the cross infections, according to the CDC and the World Health Organization (WHO) after years of research and studies, is proper handwashing. Lately, the CDC has added hand cleaning with rinse-free disinfectant such as alcohol or alcohol gels as an effective alternative to handwashing to reduce the frequency of time-consuming handwashing procedures and therefore to improve hand hygiene compliance. Both organizations had issued comprehensive guidelines to healthcare workers and those working in the food processing and delivery industries as well as to the public on what constitutes as proper handwashing steps and hand cleaning to achieve effective killing of both transient and resident germs on hands to reduce cross infection.

However, even with all healthcare workers, especially physicians, having the common knowledge as well as the education and training that having clean hands is the key in reducing infection propagation, most of them do not conduct hand hygiene procedures at the thoroughness and frequency required. Without human monitoring, only 15% of doctors and 35% of nurses comply with the hand hygiene guidelines established by CDC for hospitals. Knowing someone is monitoring them, the percentage increases to around 50%. Worst of all, the intensive care units in hospital typically have the worst hand hygiene compliance record.

Many studies had been done by government agencies and hospitals to understand why the low compliance by the healthcare staff. Some tangible reasons were heavy work load, inconvenient location of wash basins, skin irritation and dryness due to frequent handwashing, the misconception of wearing gloves would eliminate the need of hand hygiene, etc. Very few cited lack of education, training or comprehension of the importance of hand hygiene in HAI reduction.

With those studies in mind, virtually every hospital has undergone improvements such as addition and relocation of wash basins (making handwashing convenient to all staff), addition of numerous rinse-free disinfectant dispensers in hallways and in patient rooms facilitating each staff member to clean his/her hands before handling a patient, increasing and strengthening periodic education session(s) emphasizing the importance of hand hygiene in reducing HAI and instituting extensive human monitoring. Yet the compliance rate only showed limited improvement when extensive and long term human monitoring was carried out.

This outcome clearly points to three critical factors toward increasing the hand hygiene compliance by healthcare workers: (1) continuous monitoring is a must; (2) timely reminder to the staff members to clean hands; (3) the monitoring process must not create additional work for healthcare workers or interrupt their busy work routines.

 Huang, Peng and Hwang's invention describes a proactive hand hygiene monitoring system that utilizes:

1. An intelligent identification tag (can be in the form of a wrist band or an foot ankle band) assigned to each personnel to be monitored, which uses active RFID or a combination of passive and active RFID technology to interact with pre-programmed soap and rinse-free disinfectant dispensers as well as entry-exit sensors to record the time-date of each of this person's hand hygiene event and its thoroughness. Based on the ID tag's record and notification from an entry-exit sensor, it will also proactively prompt (by either vibration or low tone) the wearer to conduct hand cleaning prior to perform the next task, such as handling next patient or after handling raw meat.

2. Pre-programmed soap and rinse-free disinfectant dispensing (wall-mounted and/or counter top placed) units which will notify a user's ID tag via radio frequency of the dispensers' own unique identification codes after triggering by that user's ID tag

3. Entry-exit sensors which will detect the entering into or exiting from a controlled access area of one or more persons and inform each person's ID tag via radio frequency to record the time-date of the unique identification codes of the sensor as well as prompting each ID tag to check the last time of hand hygiene event of the wearer to determine whether a prompt for hand cleaning is required.

4. Data transfer stations which will download the recorded data from every personnel ID tag placed on their slots. They will verify the data integrity and convert them into a proper format (such as TCP/IP for Ethernet) for transmission to the central data processor (computer). They will also charge the internal battery of an ID tag to maintain its functionalities.

5. A central computer (which can be a personal computer or a server) which will receive the collected data from all the data transfer stations and processing them into a daily and/or periodic hand hygiene compliance report. It will also query the maintenance conditions of each component of this system (such as soap and rinse-free disinfectant refills as well as battery power level) and perform diagnostic to detect any malfunctions. During the data collection process, it will synchronize its clock with all the ID tags to assure the entire system is in synchronization with respect to timing of all events. It will also archive all the collected data and information.