Colloid and Interface Science

Projects studying large charged molecules and/or molecules at interfaces between phases.

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Novel Fabrication of Nanostructured Particles with an Arbitrary Shape

Convenient methods for the fabrication of complex nanostructures are emerging in the growing field of nanotechnology for novel optical, electrical, magnetic, and also biological functions. Recently we have developed a simple and effective method to produce various kinds of nanostructured particles like nanorice and nanospears (i.e., tapered nanorods) using alumina membrane as templates. The nanocylindrical pores of anodized alumina membranes are filled with spherical polymer nanoparticles by a solvent assisted nano-injection. Then the membranes are heated in an oven above the glass transition temperature of the polymer. Due to the non-uniform heating, non-equilibrium capillary forces, and the wetting property of the polymer nanospheres confined in the nanocylinders, the spherical nanoparticles coalesce to form both aspect ratio and end-shape controlled nanorods which are shaped in the forms of nanorice, nanospears or tapered nanorods. Other novel nanostructures include nanorods, nanograss, nanodisks, and broken nanodonuts using vaious nanomaterials such as polymers, metals, inorganic particles, and biomolecules.

Investigators (PI is linked): Ilsoon Lee
Categories: Rheology and Multiphase Flow, Colloid and Interface Science, Polymer Science and Engineering, Structural Materials, Nanomaterials

Colloidal Interfaces between Biomaterials and Biological Tissue

Surface properties and how they govern cell adhesion is combined with colloidal assessment of the interfaces between bone and common biomaterials such as alumina, hydroxyapatite, bioglasses, titanium alloys, stainless steels, nickel cobalt alloys, etc. To date, the materials making contact with bone in the total hip and total knee implants have been assessed for their ability to attract mineralized bone. The colloidal properties of differing compositions of Bioglass, a bioactive bioceramic, are also being measured and compared to their ability to create a strong bone/biomaterial interface.

Investigators (PI is linked): Melissa J. Baumann
Categories: Colloid and Interface Science, Biomaterials

Interactions of nisin with selected proteins at the liquid-liquid interface

Nisin is a small (3510 Da), positively charged amphipathic polypeptide; it is produced by Lactococcus lactis and contains dehydrated residues and lanthionine or thioether rings. It has antimicrobial activity against a wide range of gram-positive bacteria and has been widely used as a food preservative in the dairy industry. Its antimicrobial activity stems primarily from permeabilization/pore formation of the cytoplasmic membrane of target organisms, making it a promising candidate for use in formulations that could effectively transfer drugs across cellular membranes and significantly reduce microbial resistance to antibiotics. The goal of this project is to characterize the adsorption dynamics of nisin at a model oil-water interface, and to study its interactions with other macromolecules in sequential and competitive adsorption experiments, using a diverse group of proteins of varying molecular weight.

Investigators (PI is linked): Robert Y. Ofoli
Categories: Biomaterials, Colloid and Interface Science

Engineering Surfaces and Interfaces

Self-assembly, microcontact printing, and layer-by-layer assembly techniques for surface tuning and patterning are utilized to develop new opto-electronic and bio applications. A variety of materials, such as organic and inorganic molecules, polymers, particles, and biomolecules including cells are used to prepare topologically and functionally structured surfaces for their desired purposes using novel self and directed assembly techniques.

Investigators (PI is linked): Ilsoon Lee
http://www.egr.msu.edu/~leeil/ilsoon_research.html#Ilsoon%20Lee%  Categories: Nanomaterials, Biomaterials, Electronic Materials, Polymer Composites, Structural Materials, Polymer Science and Engineering, Colloid and Interface Science, Biotechnology

Adsorption of liposomes on charged polyelectrolyte substrates (Collaborative with Worden and Lee)

One of the problems with some constructions of biomimetic interfaces using lipid bilayers is that no cushion is provided between the bilayer and the substrate to allow for full insertion of membrane proteins, enable their lateral mobility, and provide for ionic reservoirs on either side of the membrane. The deposition of polyelectrolyte multilayers provides ideal cushions for this purpose, and therefore has potential in biosensor applications. In this project, we are studying the adsorption of fluorescently labeled vesicles on charged polyelectrolyte multilayers (PDAC, PAH, PEG, SPS) deposited on glass slides, using total internal reflection fluorescence microscopy (TIRFM) and fluorescence recovery after pattern photobleaching (FRAPP) to estimate the mobility and lateral diffusion coefficients of the lipids in the bilayer. The resulting interfaces were also characterized by cyclic voltammetry (CV) and quartz crystal microbalance (QCM). This work is being done in collaboration with the research groups of Dr. Ilsoon Lee and Dr. RM Worden.

Investigators (PI is linked): Robert Y. Ofoli
Categories: Biotechnology, Colloid and Interface Science, Biomaterials, Nanomaterials

Catalytic transformation of biorenewables to petrochemicals

An important global challenge is the need to eventually replace finite fossil fuels with viable renewable resources. Currently, there are many significant initiatives on converting biomass to alternative fuels, but much less activity on using renewables for petrochemicals production. There is much knowledge on the transformation of crude oil to fuels and chemical feedstocks. However, due to significant differences between crude oil and biomass, these well-tested transformation pathways are not suitable for biomass conversion. In this project, we are developing generic methods for synthesizing catalytic nanoparticles (NPs) and surface modification to attach molecular catalysts (MCs), developing protocols for physical and/or chemical immobilization of catalytic NPs and NP-MC complexes in microfluidic channels, and assessing and optimizing catalytic NPs in both classical and microfluidic reactors. We will use the conversion of lactic acid to glycerol as the model reaction. Fatty acids from plant oils represent another important class of abundant biorenewables. To convert these to petrochemicals, we will anchor molecular catalysts to catalytic bimetallic nanoparticles to obtain NP-MC hybrid (NMH), and assess NMH catalyst effectiveness in microreactors using the hydrogenation of selected fatty acids to petrochemicals as model reactions. This is a collaborative project with Professor Obare (Department of Chemistry at UNCC; adjunct in CHEMS).

Investigators (PI is linked): Robert Y. Ofoli
Categories: Nanomaterials, Colloid and Interface Science, Biotechnology, Biobased Industrial Products, Sustainable Economy

Opto-electrochemical characterization of bilayer-embedded biomacromolecules in TIR geometry

Membrane-bound enzymes and proteins can serve as ion channels and/or catalyze a variety of biological processes. These processes can be characterized by a variety of techniques, including optics and electrochemistry. In this project, we are developing surface chemistries to enable us to use ITO as an effective electrode on which bilayer lipid membranes can be deposited to provide an electrode platform for simultaneous optical and electrochemical measurements of protein activity. We also have capabilities for physical characterization of biomacromolecules (fluidity and mobility measurements) on planar as well as tethered bilayers by fluorescence recovery after pattern photobleaching (FRAPP) experiments, enabling us to do a complete study of many enzymes and proteins of medical interest.

Investigators (PI is linked): Robert Y. Ofoli
Categories: Nanomaterials, Biomaterials, Colloid and Interface Science, Biotechnology

Quantitation of biomolecular coverages at the liquid-liquid interface

We revisit work done earlier in our laboratory on estimating interfacial coverages of proteins at the oil-water interface, using total internal reflection fluorescence microscopy (TIRFM) and fluorescence photobleaching recovery (FPR). This method, first proposed by Zimmerman et. al (J. Colloid Interface Sci. 1990, 139, 268-280) for estimating surface coverages at the solid-liquid interface, is based on the principle that macromolecular interfacial coverages are related to the ratio of bulk and interfacial contributions to the total fluorescence emission detected. Interfacial coverages obtained for the adsorption of bovine serum albumin (BSA) at the oil-water interface using this technique are in the range of 0.02 to 0.3 mg/m2 in the bulk concentration region of 0.2 mg/ml to 3.5 mg/ml. These values are lower than those typically reported in the literature for similar proteins, most likely due to the low shear rates (<0.5 s-1) used in our experiments. We are investigating the effect of low shear rates on protein relaxation and spreading, and associated implications on ultimate coverages at fluid-fluid interfaces. We are also using this technique to obtain interfacial coverages at the oil-water interface for human plasma fibronectin, a large glycoprotein that has a rod-like structure and exhibits considerable flexibility. As part of this work, we are investigating fluorescence lifetimes of dye-labeled proteins at the liquid-liquid interface using two-photon excitation spectroscopy. This segment of the project is being done in collaboration with Dr. Gary J. Blanchard of the Department of Chemistry at MSU.

Investigators (PI is linked): Robert Y. Ofoli
Categories: Colloid and Interface Science, Biomaterials

Self-assembled, Nanostructured Biomimetic Interfaces

Living cells efficiently perform many vital sensing, signaling, catalytic, and bioelectronic processes at the molecular scale. These processes typically occur at cell membranes, whose principal components include a bilayer lipid membrane (BLM) and membrane proteins. The BLM's nanoscale thickness (5 nm) and high electrical resistance give it unique optical and bioelectronic properties. A diverse array of membrane proteins embedded in the BLM imparts the highly specific activities exhibited by cell membranes. These activities can, in principle, be mimicked in the laboratory by reconstituting appropriate membrane proteins into artificial BLM. We are using self and directed assembly tools to fabricate functional and nanostructured biomimetic-interfaces that use lipid bilayers, membrane proteins (such as neuropathy target esterase), and other nanostructured components (e.g. polyelectrolyte multilayers) to reproduce cell-membrane processes. These systems have outstanding potential for conducting fundamental studies of nanoscale biological processes and for developing new technologies, including high-throughput drug screening systems, research tools to study membrane proteins, and high-performance biosensors.

Investigators (PI is linked): Ilsoon Lee
http://www.biomimetic.org/  Categories: Nanomaterials, Biomaterials, Polymer Composites, Structural Materials, Polymer Science and Engineering, Colloid and Interface Science, Biotechnology

Bio-Carbon Nanomaterials

Carbon nanoparticles are available in several geometries, including spherical fullerenes, cylindrical nanotubes and planar nanoplatelets. While these nanoparticles all share the same graphenic structure that imparts semiconductor properties, the diverse geometries afford a spectrum of unique chemical, electrical, magnetic, and optical properties. Composite materials containing carbon nanoparticles electrically coupled to biomolecules could yield an array of high-performance technologies. Inclusion of a biological recognition element, and any necessary cofactor or mediator, allows the composite electrode to serve as an integrated, bioactive electrode unit (i.e., bio-carbon network). This work includes (1) development of simple and rapid methods to modify and process carbon nanoparticles for self and directed assembly, (2) incorporation of the nanoparticles into bio-carbon networks, and (3) characterization of the network’s fundamental properties.

Investigators (PI is linked): Ilsoon Lee
Categories: Nanomaterials, Biomaterials, Polymer Composites, Structural Materials, Polymer Science and Engineering, Colloid and Interface Science, Biotechnology

Nanomixing or Nanodispersion of Nanomaterials

We have established a strategic partnership with the Primix Corporation to study the nanomixing, nanodispersion, and nanoparticulate processes. Due to the enhanced high shear forces, the dispersed nanomaterials have superior stability in solvents. We are currently studying why it helps the stability of the nanodispersion. The mixer, named T.K. Filmics, uses a multiphase swirling flow to achieve extremely high energy dissipation and achieve the dispersion. The mixer has a stationary outer cylinder, within which an inner cylinder rotates very rapidly. The two phases are introduced separately from the bottom and the particulates are dispersed by shear in the annular region between the two cylinders. The high shear force, thin film mixing system has been newly developed from the conventional mixers by the Primix Corporation located in Japan (http://www.primix.jp/en/index.html).

Investigators (PI is linked): Ilsoon Lee
http://www.primix.jp/en/index.html  Categories: Nanomaterials, Polymer Science and Engineering, Rheology and Multiphase Flow, Colloid and Interface Science

Wrinkle-free Nanomechanical Films

Wrinkling or buckling is a common natural phenomenon which occurs in numerous forms on many different length scales. Common forms of buckling include the wrinkling of human skin, the surface of many dried fruits, and even the formation of mountain ranges. Generally buckling occurs when a stiff upper material on a more compliant substrate is compressed. Compressive forces can be generated physically (e.g., stretching or compressing a compliant substrate) or simply by raising or lowering the temperature of the materials. Wrinkling and related phenomena in various materials have been studied from the standpoint of micro and bio mechanics. How and why wrinkles form has been well studied; however, preventing the occurrence of such a phenomenon remains a challenge. The goal of this proposed work is to study how nanoparticles influence the mechanical (or thermal) wrinkling (or buckling) of thin films, and to develop such wrinkle free films for various applications.

Investigators (PI is linked): Ilsoon Lee
Categories: Biotechnology, Colloid and Interface Science, Polymer Science and Engineering, Structural Materials, Polymer Composites, Nanomaterials