Plasma modification techniques

Immobilization of Proteins and Enzymes onto Functionalized Polypropylene Surfaces by a Gaseous Plasma Modification Technique... 

Urokinase has been widely used for the clinical treatment of thrombogenetic disease and hemorrhoidal disease. Artificial organ materials, on which urokinase was immobilized for its fibrinolytic activity, have been developed for blood-compatible materials. For example, Liu et al. immobilized urokinase by encapsulation in poly(2-hydroxyethyl methacrylate) and Kbnig et al. introduced urokinase on the surface of the polytetrafluoroethylene using plasma modification technique by covalent bond. Another example of immobilized urokinase application was reported by Kato and coworkers, who had used mokinase immobilized in a Teflon catheter for treatment of thrombosis. 

The techniques for the treatment of plasma in their different forms have moved out of the academic fold to become important industrial processes for modifying the surface properties of polymers. The main advantages of plasma modification techniques can be summarized in the following ... 

Restraining a gaseous plasma from expanding and compressing is also a form of plasma modification. Two reasons for plasma confinement are maintenance of the plasma and exclusion of contaminants. Plasmas may be confined by surrounding material, eg, the technique of wall confinement (23). A second approach to confinement involves the use of magnetic fields. The third class of confinement schemes depends on the inertial tendency of ions and associated electrons to restrain a plasma explosion for a brief but usehil length of time, ie, forces active over finite times are required to produce outward particle velocities. This inertial confinement is usually, but not necessarily, preceded by inward plasma motion and compression. 

B8. Boulanger, P., and Biserte, G., Chromatographie sur papier des acides amines et polypeptides des liquides biologiques. 2. Modifications techniques et r ultats nouveaux (plasma sanguin). Butt. soc. chim. biol. 33, 1930-1939 (1951). 

Fig. 6 Overview of the wavelength ranges that can be routinely achieved using the various modification techniques of PDMS surfaces. The inset displays a 3-D AFM height-image of a plasma-modified surfaces...

Our previous work with PPNVP and GOx-PPNVP/PEUU (6,12,25), which focused on characterization of the surface modified thin films, has demonstrated that a reasonable amount of control can be exerted over the chemistry of plasma modification. The techniques used here to attach active GOx to PEUU may be applied to a wide variety of biomolecules and a wide variety of organic and inorganic substrates. Incorporation of GOx-PPNVP/PEUU into the thin-layer cells extended the potential applicability of GOx-PPNVP/PEUU and similar materials to specific practical applications such as sensing devices. Similarly, the ease of fabrication of the thin-layer cells and the wide variety of electrochemical techniques which are available for use with thin-layer cells warrant further development of this system. 

Biomaterials are non-viable materials used in medical devices, which are biocompatible with minimal non-specific protein adsorption. This paper describes some functionalization techniques of surfaces against non-specific protein adsorption, such as (1) photo-immobilization, (2) y-activation or a rf plasma modification and (3) a wet-chemical treatment. The modification changes the chemical surface composition within the first 10 nm. 

Similar to static contact angles from the sessile droplet method, Wilhelmy dynamic contact angles are an excellent indication of the change in surface characteristics due to surface modification techniques such as plasma polymerization coating. The cosine of dynamic advancing contact angles from the first immersion, cos 0D,a,i of untreated, TMS-treated, and (TMS-I-02)-treated conventional... 

Interest in the roles of both essential and non-essential trace metals in human health and disease has undergone an enormous expansion in the last thirty years. This has come about partly due to major advances in our knowledge of inorganic biochemistry (Frausto da Silva and Williams. 1991), as well as the wider introduction into clinical laboratories of powerful analytical techniques such as graphite furnace atomic absorption spectrometry (Delves, 1987 Slavin, 1988). Developments in instrumentation and chemical matrix modification techniques have also brought about dramatic improvements in analytical performance (Delves. 1987 Baruthio et al.. 1988 Slavin, 1988 Christensen et al., 1988 Savory and Wills, 1991). Other analytical techniques, such as inductively-coupled plasma emission spectrometry (ICP) and ICP-mass spectrometry are also finding wide application in the clinical analysis of trace elements (Kimberly and Paschal, 1985 Delves and Campbell, 1988 Melton et al., 1990). Although the cost of such Instruments tends to restrict their use only to specialist centres, they have very important roles as reference techniques in the characterisation of reference materials (Delves and Campbell, 1988). 

Plasma techniques - plasma modification, plasma deposition and plasma and grafting reactions - are illustrated for the elaboration of tools, medical devices and biomaterials. These promising techniques are developed either for the sterilization, antifouhng surfaces or for enhancing the biofilms formation. 

FIGURE 23.2 Surface modification techniques of electrospun nanofibers, (a) Plasma treatment or wet chemical method, (b) Surface graft polymerization. (c) Coelectrospinning. Reprinted with permission from Ref. [43]. Copyright 2009. Elsevier. 

The plasma tocopherol technique used was essentially simihir to that described by Quaife and Biehler (1945) and the peroxide hemolysis method used was a modification of that reported by Rose and GySrgy (1952). The most important artifact in the peroxide hemolysis test is the varying rate at which different batches of peroxide are decomposed. This artifact does not change the rank order of the results on a given day but precautions must be taken to standardize the peroxide if results obtained at different times are to be compared. In recent years, the 2.5% peroxide solution used in the test has been aged in Pyrex glass bottles for several days before use, and this procedure has made the results more uniform from day to day. 

Plasma treatment is one of most common and suitable surface modification techniques for polymeric materials. This treatment can selectively introduce certain functional groups at a polymer sur ce with little damage to the bulk of the polymer. However, it is known that a plasma-treated polymer surface loses its properties gradually with aging. One reasonable explanation for this phenomenon is that the nctional groups, introduced by plasma treatment, rotate or move away from the surface into the bulk. Thus the changing surface properties may reflect... 

Other surface modification techniques include the use of free radical-, photochemical-, radiation- redox- and plasma-induced grafting. These are used to covalently attach some useful monomers onto the membrane surface [20]. Gas plasma treatment is also used to induce surface modification water permeabihty is improved by oxygen plasma treatment due to the introduction of hydrophihc carboxylate groups, whereas argon plasma treatment can enhance chlorine resistance by increasing the extent of cross-linking at the nitrogen sites. 

Yet another important class of modification techniques for PE, comprises those methods which atfect only the sur ce of the polymer. Plasma polymerization is a modification technique that uses a radio fiequency (rt) generated plasma to polymerize a monomer on the surface of the material. 

This is a long essay question which can be answered using any of the major modification techniques listed in the chapter on polyethylene modification. All information needed to compare and contrast two modification techniques, the changes in polyethylene physical and chemical properties, and an example of real world applications for that modified polyethylene are to be found for each ofthe techniques Sulphochlorination, Chlorination, Plasma Modification, Crosslinking - Chemical and E-Beam, and Graft Modification with Maleic Anhydride. 

A wide array of surface modification techniques, ranging from simple to sophisticated, wet to dry, and vacuum to nonvacuum, are available for a host of polymeric materials. They include plasma surface treatment laser surface treatment corona, flame, UV, ozone, UV/ozone, photochemical, photografting, chemical grafting, and chemical methods of stuface modification and modification of polyamide surfaces by microorganisms [7]. 

Based on the membrane surface properties and the HA properties, various researchers have attempted to change the membrane surface characteristics by surface modification. Different techniques have been performed, such as ion beam irradiation, plasma treatment, redox-initiated graft polymerization, photochemical grafting, and interfacial polymerization (IP). In this chapter, two surface modification techniques, IP and photochemical grafting, are discussed by means of experimental examples. The surface characteristics of the unmodified membrane and the modified membranes are studied and their relationships with irreversible fouling and NF performance are reported. 

---