WO1999043743A1 - Smart aerogel - Google Patents
Smart aerogel Download PDFInfo
- Publication number
- WO1999043743A1 WO1999043743A1 PCT/US1998/027826 US9827826W WO9943743A1 WO 1999043743 A1 WO1999043743 A1 WO 1999043743A1 US 9827826 W US9827826 W US 9827826W WO 9943743 A1 WO9943743 A1 WO 9943743A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- aerogel
- bioaerosol
- receptor
- doped
- bioaerosols
- Prior art date
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D45/00—Separating dispersed particles from gases or vapours by gravity, inertia, or centrifugal forces
- B01D45/04—Separating dispersed particles from gases or vapours by gravity, inertia, or centrifugal forces by utilising inertia
- B01D45/08—Separating dispersed particles from gases or vapours by gravity, inertia, or centrifugal forces by utilising inertia by impingement against baffle separators
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
- G01N1/2205—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling with filters
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
- G01N1/2214—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling by sorption
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/02—Devices for withdrawing samples
- G01N1/22—Devices for withdrawing samples in the gaseous state
- G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
- G01N2001/222—Other features
- G01N2001/2223—Other features aerosol sampling devices
Definitions
- Bioaerosols including bacteria, viruses, toxins, and other biological materials generally have particle sizes ranging from 0.01 to as large as 10 ⁇ m and can sometimes be harmful if contacted with animals and/or inhaled.
- Some sensors now exist to detect bioaerosols current technology lacks the capability to provide unique, sensitive, and rapid detection of particular bioaerosols. Due to the extent and speed at which airborne pathogens may be able to spread and infect, a new generation of biological sensors is needed. There, accordingly, remains a need for a biological sensor material that is adapted for use in efficient collection, rapid detection, specific identification, and near real-time reporting of the presence of certain bioaerosols.
- the "smart aerogel” of the invention constitutes an aerogel combined with bio-affinity receptors that have unique affinities to specific bioaerosols. Aerogels, sometimes referred to as “solid smoke", are multifunctional materials with unique properties that the inventors put to use to enable their use as a collection, assay, and identification media. Aerogels have two major properties of interest: a complex pore structure (micro- and meso-pores) with discrete ranges from 2 nm to 100 nm, as well as a macro structure of over 100 nm, and a large internal surface area (-1500 m 2 /g) that can be coated with reactant compounds. These different properties can be independently controlled during synthesis.
- Aerogel is manufactured into the advanced "smart aerogel” sensor media of the invention by linking reactant bio-affinity compounds to the internal matrix of the aerogel to create “docking" sites. Thereafter, any bioaerosols, including airborne pathogens impinging on the smart aerogel will be in contact with and preferably specifically bond to the receptor and thus selectively attach to the aerogel. After a particular bioaerosol is captured in the smart aerogel, the smart aerogel can be sprayed with a mist of water or other fluids. This dissolves the smart aerogel and the captured bioaerosol into a small amount of solution that can then be analyzed. A device and means for accomplishing this is disclosed in non-provisional patent application No. 09/199,979, filed November 25, 1998, entitled “Aerogel Environmental Sampler and Concentrator”.
- the bioaffmity compounds have a high selectivity and affinity for specified compounds, while the aerogel has a complex pore structure and extremely large internal surface area that renders a highly efficient, lightweight collection media. Combining the bioaffmity compounds with aerogels essentially produces a powerful "sponge" that will only absorb the specified bioaerosol.
- an air sample can be checked for a number of suspected bioaerosols.
- Figure 1 shows the prior art aerogel synthesis process illustrating the sol-gel chemistry and supercritical drying that result in this low-density, high-porosity material.
- Figure 2A shows complex aerogel pore structure consisting of a micro-, meso-, and macro-porosity.
- Figure 2B diagrammatically illustrates sialic acid with a pendant arm incorporated into the aerogel to form the smart aerogel sialoside aerogel.
- Figure 3 shows potential chemical binding methods to incorporate the bio-affinity receptors into the aerogel matrix.
- Figure 4 is a schematic illustration of the process of incorporating bio-affinity compounds (dopants) directly into the aerogel pore matrix during synthesis.
- Figure 5 shows the chemical structure of sialic acid.
- Figure 6 illustrates the ionic and hydrogen bonding modes that prohibit functional group interaction.
- Figure 7 depicts chemical bonding of the aerogel surface with a polymerizable pendant arm.
- Figure 8 illustrates one method of attaching a pendant arm to form sialoside and incorporating it into the aerogel to form the smart aerogel sialoside aerogel.
- Figure 9 is a diagrammatic illustration comparing pore sizes of aerogels doped with sialic acid to accommodate an influenza virus.
- Figure 10 is a scanning electron microscope view of a standard recipe aerogel with pore sizes of about ⁇ 0.1 ⁇ m.
- Figure 11 is a scanning electron microscope view of a macro-pore recipe for aerogel with a pore size of about ⁇ 2 ⁇ m.
- Figure 12 is a block diagram of the aerosol testing apparatus, A) mono-dispersion aerosol testing, B) poly-dispersion aerosol testing.
- Chart 1 compares free virus of solution for a virus solution, an aerogel control, and the sioloside aerogel of the invention to illustrate the selective uptake by the sioloside aerogel of the influenza virus.
- Table 1 shows the primary characterization methods and the information obtained from each analysis.
- Table 2 sets forth various reaction conditions in forming aerogels and the physical characteristics associated with these reaction conditions.
- sol-gel process where a solution of silicate monomer (sol) undergoes polymerization to a gel, as shown in Figure 1.
- a solution of silicate monomer (sol) undergoes polymerization to a gel, as shown in Figure 1.
- an ethanol solution of tetraethoxysilane Si(OCH 2 CH 3 ) 4 in the presence of water, ethanol, and catalyst undergoes partial hydrolysis and a condensation reaction to form a sol (a colloidal dispersion of particles in liquid).
- a solid silicate network separates out of the solution (gel point).
- the solid is still "soaking" in the ethanol solution; this biphasic system is usually referred to as the alcogel.
- Subsequent removal of the liquid phase from the alcogel by supercritical drying results in a low density, highly porous silica aerogel.
- the processes of forming aerogels are well-known.
- Figure 2 shows the three regimes of pore size that evolve during polymerization: micropores ( ⁇ 2 nm), mesopores (2 nm - 100 nm), and macropores (> 100 nm).
- micropores ⁇ 2 nm
- mesopores 2 nm - 100 nm
- macropores > 100 nm.
- Reaction conditions yield control over pore size and include pH, solvent, temperature, hydrolysis ratio, and monomer concentration. Further discussion of how pore size can be controlled is set forth in the section below on pore engineering.
- Doping refers to the process of adding a substance to the aerogel matrix.
- the surface of the silica aerogel pores is covered with silanol (SiOH) groups shown in Figure 2A and 2B, which give the aerogel its characteristic pore structure and hydrophilic nature.
- the surface silanol groups can be utilized for attachment of specified molecules (dopants) via hydrogen bonding, ionic bonding, or covalent bonding as illustrated in Figure 3. It has been found that covalent bonding results in the most useful bonds.
- the modified sol-gel process for incorporating dopants is shown in Figure 4.
- Dopants are added at the alcogel stage and allowed to react with the surface silanols. Subsequent washing stages, followed by supercritical extraction, will result in a surface modified "doped" aerogel.
- the smart aerogels of the invention consist of a silica aerogel matrix doped with a high bio-affinity receptor drug.
- the first model used to test the feasibility of doping aerogel with high bio-affinity receptors for bioaerosols is for sialic acid directed toward the influenza virus. This virus is an envelope virus that probably infects hundreds of millions of people each year.
- Hemagglutinin is a protein responsible for viral attachment to the host cell through interactions with sialic acid residues located on the host cell's surface.
- Neuraminidase is responsible for viral release from the host cell and subsequent spreading of infection after viral penetration and multiplication.
- Hemagglutinin is the more abundant surface protein (90%) and plays a critical function in viral adhesion to the host cell.
- the structure of the influenza neuraminidase was initially determined by scientists who are currently designing drugs for both of these influenza surface proteins. (See Longman, R. In Vivo 1994, 5,23-31.)
- sialic acid is a molecular residue that binds to the glycoprotein hemagglutinin on the surface of the flu virus. It was chosen as a model for a biochemical aerosol (BA) specific drug because sialic acid is readily accessible, relatively inexpensive, and has a molecular weight and chemical functionality similar to other B A specific drugs.
- BA biochemical aerosol
- performance testing of aerogels doped with sialic acid can be accomplished with an inactive flu virus; thus, making these studies less hazardous compared to BA performance testing.
- Equation 1 shows that molecular recognition involves the association of a receptor (A) and a substrate (B) to form the complex (AB).
- K 0 is the binding constant that represents the ratio of the concentrations of products to reactants at thermodynamic equilibrium.
- a large K 0 represents a large binding constant signifying that the receptor has a high affinity for the substrate.
- the receptor is a proteinacious active site, which forms a three dimensional pocket that "exactly" fits the substrate, and is sometimes referred to as the lock and key interaction.
- the substrate must be able to utilize its chemical functional groups when binding to the pathogen active site. It is for this reason that hydrogen bonding and ionic bonding may hinder the proper interaction as shown in Figure 6.
- the hydrogen and ionic bonding modes of attachment utilize the drug's chemical functional groups to actively “bond" to the aerogel surface, and thus, prevent these functional groups from interacting with the pathogen active site.
- the modified drug as shown in Figure 7 is synthesized.
- the sol-gel process remains unchanged from the sol to gel steps.
- an ethanol solution of the bio-affinity drug (dopant) will be added.
- the trimethoxysilane functional group of the bioaffinity drug will react with the pore surface silanol groups; thus, attaching the receptor to the matrix.
- a major goal of the invention is to engineer aerogel pores sized to accommodate the bioaerosols intended to be captured. See Figure 9, which diagrammatically illustrates the relationship between the size of the bioaerosol and the pore size, in the case of the influenza virus.
- Figures 10 and 11 are electron microscope images showing, respectively, a standard recipe aerogel with a pore size of about about ⁇ 0.1 ⁇ m, and a macro-pore recipe for aerogel with a pore size of about ⁇ 2 ⁇ m.
- control over the pore size of the aerogel can be accomplished by various methods.
- reaction conditions of the sol e.g., the pH (catalyst is acid or base), type of solvent, temperature, hydrolysis ratio [H 2 O]/[Si(OCH 2 CH 3 ) 4 ], and the degree of dilution of Si(OCH 2 CH 3 ) 4
- the macropore range >100nm
- template pore sizing factors including surfactants, latex microspheres, and multicomponent phase separation.
- viruses and toxins fall within mesopore range, and therefore pore size can be engineered to ideal size by manipulating the reaction conditions.
- Bacteria and Rickettsia fall within the macropore range, and therefore the necessary pore size can be engineered by manipulating pore templating.
- the aerogel can be designed to lessen attachment, for example, of oversized bioaerosols to the receptors bonded to the interior surface of the pores. In this way, the selectability of the smart aerogel is enhanced and a greater percentage of the targeted bioaerosol than if the distribution of pore sizes is left to chance.
- Figures 2B, 7, and 8 it is necessary to assess the influences of this process on both the aerogel nanostructure and the bio-affinity receptor compound. Specifically, characterization of the aerogel nanostructure will probe physical characteristics including density, surface area, porosity, pore size, and pore volume. Characterization of the doped bioaffinity drug will examine its covalent attachment (as opposed to non-covalent physical absorption) to the aerogel matrix. Non-covalent physical absorption is a secondary reaction, which can occur during the production process and can create problems such as drug leaching, reduced shelf life, and inefficient binding. Lastly, characterization will be performed to verify that the production process does not decompose the drug. Sialic acid survives the harsh conditions of aerogel production.
- sialic acid was dissolved in ethanol and loaded into an autoclave. Liquid CO 2 was added to the mixture. The temperature of the mixture was raised to 45°C and 87,700 Kg/m 2 (1250 psi) for three hours, after which the mixture was brought back to room temperature and pressure. The ethanol was removed by rotary evaporation, and ⁇ NMR spectra of the control and experimental batches were taken. The spectra were identical, indicating no damage to the sialic acid molecule.
- Table 1 shows the primary characterization methods and the information obtained from each analysis. Methods 1-4 probe the bio-affinity drug. [1. Elemental Analysis (EA); 2. FT Infrared Spectrometry (FTIR); 3. Mass Spectrometry; and 4. Solid State Nuclear Magnetic Resonance Spectrometry (NMR)].
- EA Elemental Analysis
- FTIR FT Infrared Spectrometry
- NMR Solid State Nuclear Magnetic Resonance Spectrometry
- An aerogel doped with sialic acid Figures 7 and 8, will be used as an example. Elemental analysis is a simple combustion reaction, which yields a percent composition of elemental carbon, hydrogen, nitrogen, and silicon in the final aerogel product. If for example, sialic acid is doped into the aerogel matrix at a 5% concentration (molar ratio), elemental analysis verifies the true concentration.
- FT infrared spectrometry examines molecular bond stretching and bending frequencies of the bioaffinity drug; sialic acid yields characteristic absorption frequencies consistent with a carbonyl functional group, an alcohol, and an amide. Mass spectrometry will provide secondary verification of drug incorporation. This type of analysis yields the molecular weights of ionized fragments in the aerogel matrix. A positive result shows a mass unit consistent with the molecular weight of the sialic acid.
- Solid state nuclear magnetic resonance (NMR) spectroscopy is the most important method of characterization. The analysis involves probing the bioaffinity drug's molecular connectivity to determine how the atoms in the drug are connected to each other and results in a spectrum of atom frequencies.
- a l3 C NMR experiment involves analyzing the carbon resonances of a sample of sialic acid, which was not doped into the aerogel (control), and then analyzing the sialic acid resonances in the doped aerogel.
- 13 C are ideal for this type of investigation because the aerogel matrix does not have any carbon; it is composed of silicon oxide, which will not interfere with the sialic acid carbon resonances.
- the carbon resonances of sialic acid should remain the same when doped into the aerogel; the spectrum will be identical to the control spectrum. Therefore, 13 C NMR analysis provides verification that the sialic acid is incorporated into the aerogel matrix and does not decompose during the production process. 29 Si NMR analysis of the sialic acid doped aerogel will provide quantitative data in conjunction with the elemental analysis.
- the silicon atom of the polymerizable arm will resonate at a different frequency than the silicon atoms of the aerogel matrix. These different silicon peaks can be integrated in the NMR spectrum, and the ratio of the areas will yield a percent concentration of the dopant in the aerogel matrix. Observation of the 13 C and 29 Si resonances of precursor bio-affinity drug, Figure 7, in the aerogel matrix can unequivocally verify covalent attachment of the bio-affinity drug and that the drug's molecular integrity is maintained.
- Aerogel samples typically yield densities in the range of 5 mg/m 3 to 400 mg/m 3 (air has a density of 1 mg/m 3 ), which will fit in well for applications involving mounting on a micro unattended airborne vehicle (UAV).
- UAV micro unattended airborne vehicle
- Another important method of analysis to be used to determine the physical characteristics of the aerogel is porosimetry.
- the porosimeter measures surface area, porosity, pore size, and pore volume based on the absorption and desorption of gas (typically nitrogen) on the surface and in the pores of the aerogel.
- gas typically nitrogen
- the period of time a gas molecule absorbs on the surface of the aerogel depends on the energetics of the surface with which it collides: the physical and chemical nature of the sample and the gas, and the temperature of the sample. Adsorption is the concentration of gas molecules at the surface of the aerogel. When molecules leave the bulk of the gas to absorb onto the surface of a sample, the average number of molecules in the gas decreases; therefore, the pressure decreases. A pressure transducer detects this change in pressure. The analyzer determines the number of adsorbed molecules from the change in pressure, the temperature of the gas, and the volume of the container. It then automatically calculates surface area, porosity, pore size, and pore volume using the BET and B JH methods.
- the criteria to judge smart aerogel performance are pathogen affinity and selectivity. Affinity refers to how "strong" of an interaction there is between the smart aerogel and the pathogen, and selectivity refers to the smart aerogel's ability to distinguish the specified pathogen from a sea of molecules present in the air.
- the goal of a biosensor is to have a high pathogen affinity and selectivity; this creates a sensor that can detect levels of pathogen that are not harmful to personnel and has a selectivity that minimizes background noise and false positives.
- Pathogen affinity K 0
- K 0 is defined by the strength of the noncovalent molecular interactions between the receptor drug and pathogen (receptor and substrate).
- K 0 is represented in Equations 1 and 2 above, where the bioaffinity drug is represented by (A), and the pathogen is represented by (B).
- a large K 0 is equivalent to a high pathogen affinity.
- the average association constant K 0 for a monovalent hapten and a divalent IgG antibody is 3.5 X 10 5 liters/mole.
- Bio-affinity drugs for BA pathogens with a K 0 in the range of 10 6 to 10 9 liters /mole will be developed.
- the smart aerogel performance is based on how efficiently the pores can accommodate the pathogen.
- This kind of pore size engineering provides size exclusion selectivity, which further enhances the aerogel's performance.
- pore size can be varied by controlling the reaction conditions of the sol-gel process. Studies will be performed that probe the effects of varying the reaction conditions on the physical characteristics of the aerogel shown in Table 2. The physical characteristics of the aerogel will be characterized by methods described above. Knowledge of these effects will guide the pore engineering, such that the aerogel matrix can accommodate specified pathogens. The ability to tailor the properties of the smart aerogel matrix for a specific biological pathogen makes aerogel a very attractive material for sensor applications.
- Final performance testing will be executed with the doped aerogel sample, which is expected to provide exceptional performance by utilizing both the high affinity drug and the size exclusion properties of the smart aerogel's pores.
- Qualitative performance testing of the doped bioaerogel can be accomplished with the aerosol system, Figure 12.
- Bioaerosols can be generated with an aqueous solution containing nonspecific biomolecules and the specified pathogen. After the bioaerosol has been passed through a smart aerogel sample, the sample will be taken out of the chamber and assayed through wet chemistry processes to determine how much and what kind of biomolecules the smart aerogel sample absorbed. A control experiment will be done with an undoped smart aerogel sample as a comparison.
- Chart 1 graphically displays an assay measurement of the amount of free virus (influenza) in an aqueous solution, with no aerogel, with a prior art undoped aerogel, and the sialoside aerogel.
- an aqueous solution of influenza virus at a concentration of about 95 will drop to about a concentration of about 62 when a regular aerogel is placed in the solution (indicating an uptake of about 33 by the undoped aerogel.)
- the sialoside aerogel is placed in the viral solution, the virus count drops to about 33, indicating a virus uptake of about 68 out of a total of 95. This clearly indicates an enhanced uptake by the sialoside aerogel of the invention when compared to undoped aerogel.
- the smart aerogel of the invention can be used in an environmental air sampler for bioaerosol collection and fluid reduction such as that disclosed in the co-pending U.S. Patent Application No. 09/199,979. Aerogel has been demonstrated as a forced flow filtration media that is extremely hygroscopic. Experimental and theoretical investigations demonstrated the capability to incorporate sample preparation compounds that enable the assay of biological pathogens using a time-of- flight mass spectrometer.
- the compounds known as MALDI acids (Matrix Assisted Laser Desorption Ionization), were synthesized directly into the aerogel pore structure and did not cause interference in the time-of-flight assay.
- bioaerosol receptor doped aerogels can thus be used as a material to selectively capture bioaerosols including bacteria, viruses, and toxins. While the example of doping an aerogel with sialic acid to form sialoside aerogel for the influenza virus was given, by selecting other dopants and by also engineering the appropriate pore sizes in the aerogel, smart aerogels to selectively collect other particular bioaerosols can be designed. In addition, a single sample of aerogel can be doped, if desired, with more than one different bioaerosol receptors so that the smart aerogel can be used to capture and detect the presence of more than one bioaerosol.
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Abstract
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Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU38584/99A AU3858499A (en) | 1997-12-31 | 1998-12-29 | Smart aerogel |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US60/070,279 | 1997-12-30 | ||
US7027997P | 1997-12-31 | 1997-12-31 |
Publications (2)
Publication Number | Publication Date |
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WO1999043743A1 true WO1999043743A1 (en) | 1999-09-02 |
WO1999043743A9 WO1999043743A9 (en) | 2000-01-27 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/US1998/027826 WO1999043743A1 (en) | 1997-12-31 | 1998-12-29 | Smart aerogel |
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AU (1) | AU3858499A (en) |
WO (1) | WO1999043743A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6677161B2 (en) * | 2000-10-10 | 2004-01-13 | Veridian Erim International, Inc. | Aerogels and other coatings as collection media and matrix supports for MALDI-MS applications |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5360572A (en) * | 1991-11-29 | 1994-11-01 | The United States Of America As Represented By The Secretary Of The Air Force | Aerogel mesh getter |
US5470612A (en) * | 1991-11-29 | 1995-11-28 | The United States Of America As Represented By The Secretary Of The Air Force | Aerogel mesh getter |
US5767167A (en) * | 1996-05-31 | 1998-06-16 | Petrelli Research | Open cell polymeric foam filtering media |
-
1998
- 1998-12-29 WO PCT/US1998/027826 patent/WO1999043743A1/en active Application Filing
- 1998-12-29 AU AU38584/99A patent/AU3858499A/en not_active Abandoned
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5360572A (en) * | 1991-11-29 | 1994-11-01 | The United States Of America As Represented By The Secretary Of The Air Force | Aerogel mesh getter |
US5470612A (en) * | 1991-11-29 | 1995-11-28 | The United States Of America As Represented By The Secretary Of The Air Force | Aerogel mesh getter |
US5767167A (en) * | 1996-05-31 | 1998-06-16 | Petrelli Research | Open cell polymeric foam filtering media |
Non-Patent Citations (1)
Title |
---|
GARRIDO L, ET AL.: "POLYMER DISTRIBUTION IN SILICA AEROGELS IMPREGNATED WITH SILOXANES BY 1H NUCLEAR MAGNETIC RESONANCE IMAGING", POLYMER., ELSEVIER SCIENCE PUBLISHERS B.V., GB, vol. 33, no. 09, 1 January 1992 (1992-01-01), GB, pages 1826 - 1830, XP002919156, ISSN: 0032-3861, DOI: 10.1016/0032-3861(92)90479-G * |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6677161B2 (en) * | 2000-10-10 | 2004-01-13 | Veridian Erim International, Inc. | Aerogels and other coatings as collection media and matrix supports for MALDI-MS applications |
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WO1999043743A9 (en) | 2000-01-27 |
AU3858499A (en) | 1999-09-15 |
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