1: Magnetic Particles: Preparation, Properties and Applications: M. Ozaki. 2: Maghemite (gamma-Fe2O3): A Versatile Magnetic Colloidal Material C.J. Serna, M.P. Morales. 3: Dynamics of Adsorption and Oxidation of Organic Molecules on Illuminated Titanium Dioxide Particles Immersed in Water M.A. Blesa, R.J. Candal, S.A. Bilmes. 4: Colloidal Aggregation in Two-Dimensions A. Moncho-Jorda, F. Martinez-Lopez, M.A. Cabrerizo-Vilchez, R. Hidalgo Alvarez, M. Quesada-PMerez. 5: Kinetics of Particle and Protein Adsorption Z. Adamczyk.

Surface and Colloid Science

Adsorption of proteins from solution at the solid-liquid interface.

Water soluble macromers are modified by addition of free radical polymerizable groups, such as those containing a carbon-carbon double or triple bond, which can be polymerized under mild conditions to encapsulate tissues, cells, or biologically active materials. The polymeric materials are particularly useful as tissue adhesives, coatings for tissue lumens including blood vessels, coatings for cells such as islets of Langerhans, coatings, plugs, supports or substrates for contact with biological materials such as the body, and as drug delivery devices for biologically active molecules.

Gels for encapsulation of biological materials

Hydrogels of polymerized and crosslinked macromers comprising hydrophilic oligomers having biodegradable monomeric or oligomeric extensions, which biodegradable extensions are terminated on free ends with end cap monomers or oligomers capable of polymerization and cross linking are described. The hydrophilic core itself may be degradable, thus combining the core and extension functions. Macromers are polymerized using free radical initiators under the influence of long wavelength ultraviolet light, visible light excitation or thermal energy. Biodegradation occurs at the linkages within the extension oligomers and results in fragments which are non-toxic and easily removed from the body. Preferred applications for the hydrogels include prevention of adhesion formation after surgical procedures, controlled release of drugs and other bioactive species, temporary protection or separation of tissue surfaces, adhering of sealing tissues together, and preventing the attachment of cells to tissue surfaces.

Photopolymerizable biodegradable hydrogels as tissue contacting materials and controlled-release carriers

A comprehensive review of protein adsorption at solid-liquid interfaces is presented, including a brief review of protein structure and the principles of protein adsorption. Adsorption-based biocompatibility hypotheses and correlations are discussed, including surface charge, interface energetics, passivation, protein-resistant surfaces, and the role of adsorbed immunoglobulins and complement. New methods for the study of protein adsorption are discussed, including total internal reflection techniques (absorbance, fluorescence, and Raman) and ellipsometry. Qualitative “rules of thumb” of protein adsorption are also presented.

Protein adsorption and materials biocompatibility: A tutorial review and suggested hypotheses

Classical surface chemistry assumes that solid surfaces are rigid, immobile, and at equilibrium. These assumptions allow one to probe adsorption and wetting or contact angle processes purely from the point of view of the liquid phase, because one assumes that the solid phase does not in any way respond, reorient, or otherwise change in the different liquid environments. Although such assumptions may be partially correct for truly rigid solids, they are generally inappropriate for polymers (see also Chapter 7).

Polymer Surface Dynamics

Information on the outermost few angstroms of solid surfaces is very difficult to obtain. One of the most sensitive methods known for obtaining true surface information is solid/liquid/vapor (S/L/V) or solid/liquid/liquid (S/L/L) contact angles. These methods are unique in that the equipment required is relatively simple and inexpensive. Although interpretation of the results obtained is dependent on a number of assumptions, each of which is somewhat controversial, a first-order interpretation is possible and has proven to be very useful in practically all areas of surface science and engineering. Most of the surface science texts briefly referred to in Chapter 1 contain one or more chapters on surface tension, capillarity, or contact angle methods. In addition, a number of the monographs and review serials cited in Chapter 1 also contain chapters on the contact angle technique.

The Contact Angle and Interface Energetics

Numerous hypotheses exist to explain observed blood–materials interactions. It is the purpose of this article to test two popular hypotheses, namely, the minimum interfacial free energy hypothesis and the optimum polar/apolar ratio hypothesis. Methacrylate polymers and copolymers were characterized using the captive bubble underwater contact angle method; bulk water content was determined by gravimetric methods; streaming potential measurements were made; and surface roughness and possible particulate contamination were evaluated by reflected light microscopy. In vitro blood tests include whole blood clotting time measurements on polymer-coated tubes; centrifugal force platelet adhesion on polymer-coated coverslips; and a measure of the partial thromboplastin time, Russell's viper venom time (Stypven time), and the prothrombin time of native whole blood exposed to polymer-coated microscope slides. Results suggest that platelet adhesion correlates in the opposite direction of whole blood clotting time and partial thromboplastin time, emphasizing the need for a multiparameter approach to blood–materials testing. Based on these tests the minimum interfacial free energy hypothesis is not supported. In fact, the data suggest the opposite to be true. It is apparent that platelet adhesion can be a misleading indicator of blood compatibility. Neither hypotheses can explain the apparent conflict between the platelet adhesion data and the coagulation time data.

Blood–materials interactions: The minimum interfacial free energy and the optimum polar/apolar ratio hypotheses

The characterization of the gel-water interface is considered, particularly with respect to obtaining the interfacial free energy between the gel and water, γ utilizing contact angle data. The question of contact-angle-induced deformation of the three-phase region is examined and visual documentation of such deformation is presented. Air in water and octane in water contact-angle data are used to estimate γdsv γpsv γsv, and γsw for the gel-water interface as a function of bulk water fraction in the gel. It is shown that γ °0 ± 5 erg/cm2 when the bulk water fraction is greater than 0.2. All interfacial parameters determined appear to reach a constant value at a bulk water fraction of about 0.4. These results are for poly(hydroxyethyl methacrylate), poly(methoxyethyl methacrylate), poly(dihydroxypropyl methacrylate), and selected copolymers at 25°C in distilled water.

Surface characterization of poly(hydroxyethyl methacrylate) and related polymers. I. Contact angle methods in water

The concentration of multiple polyatomic gases are determined by Raman light scattering. A gas sample is placed in a cell (26, 50) and a laser beam (18) passed through the cell (26, 50). A portion of the light scattered by the gas sample is detected by collection channels (60). Light scattered by the gas sample contains inelastic Raman and elastic scattered light. Each channel (60) contains a laser line rejection filter (216) which attenuates the elastic scattered laser signals and an interference filter (217) which is specific to the transmission of one or more specific Raman lines. Each interference filter (217) is selected to a specific wavelength which is characteristic of Raman scattering from a particular polyatomic gas. Optical signals representative of these specific Raman lines are sensed by optical detectors (219) and processed into simultaneous visual readouts indicative of the intensity and concentration of each of the polyatomic gas molecules present in the gas sample.

Donald E. Gregonis

Papers

Polymer Surface Dynamics

The Contact Angle and Interface Energetics

Blood–materials interactions: The minimum interfacial free energy and the optimum polar/apolar ratio hypotheses

Surface characterization of poly(hydroxyethyl methacrylate) and related polymers. I. Contact angle methods in water

Multi-channel molecular gas analysis by laser-activated raman light scattering.