Advanced functional polymer membranes

Polymer surface modification for the attachment of bioactive compounds

Although many methods for enzyme immobilization have been described in patents and publications, relatively few processes employing immobilized enzymes have been successfully commercialized. The cost of most industrial enzymes is often only a minor component in overall process economics, and in these instances, the additional costs associated with enzyme immobilization are often not justified. More commonly the benefit realized from enzyme immobilization relates to the process advantages that an immobilized catalyst offers, for example, enabling continuous production, improved stability and the absence of the biocatalyst in the product stream. The development and attributes of several established and emerging industrial applications for immobilized enzymes, including high-fructose corn syrup production, pectin hydrolysis, debittering of fruit juices, interesterification of food fats and oils, biodiesel production, and carbon dioxide capture are reviewed herein, highlighting factors that define the advantages of enzyme immobilization.

Industrial use of immobilized enzymes

This review surveys methods for the fabrication, by plasma surface treatments or plasma polymerization, of polymeric surfaces and thin plasma polymer coatings that contain reactive chemical groups useful for the subsequent covalent immobilization, by solution chemical reactions or vapor phase grafting, of molecules or polymers that can exert bio-specific interfacial responses. Surfaces containing amine, carboxy, hydroxy, and aldehyde groups are the subject of this review. Aminated surfaces have been fabricated using various plasma vapors or mixtures and have found wide use for bio-interface applications. However, in many cases the amine surfaces have a rather limited shelf life, with post-plasma oxidation reactions and surface adaptation leading to the disappearance of amine groups from the surface. Aging is a widespread phenomenon that often has not been recognized, particularly in some of the earlier studies on the use of plasma-fabricated surfaces for bio-interfacial applications, and can markedly alter the surface chemistry. Plasma-fabricated surfaces that contain carboxy groups have also been well documented. Fewer reports exist on hydroxy and aldehyde surfaces prepared by plasma methods. Hydroxy surfaces can be prepared by water plasma treatment or the plasma polymerization of alkyl alcohol vapors. Water plasma treatment on many polymer substrates suffers from aging, with surface adaptation leading to the movement of surface modification effects into the polymer. Both hydroxy and aldehyde surfaces have been used for the covalent immobilization of biologically active molecules. Aging effects are less well documented than for amine surfaces. This review also surveys studies using such surfaces for cell colonization assays. Generally, these surface chemistries show good ability to support cell colonization, though the effectiveness seems to depend on the process vapor and the plasma conditions. Carboxylate co-polymer surfaces have shown excellent ability to support the colonization of some human cell lines of clinical interest. Immobilization of proteins onto plasma-carboxylated surfaces is also well established.

Plasma Methods for the Generation of Chemically Reactive Surfaces for Biomolecule Immobilization and Cell Colonization ‐ A Review

Modification of polyethersulfone membranes – A review of methods

Modification of polysulfone membranes 1. CO2 plasma treatment

Modification of polysulfone membranes: 3. effect of nitrogen plasma

Modification of polysulfone membranes. 4. Ammonia plasma treatment

Polysulfone membranes were modified with acrylic acid using plasma initiated graft polymerization (both in solution and vapor phase) and plasma polymerization. Changes on the surface were monitored by contact angle measurements and FTIR-ATR technique. Pore size and ultrafiltration properties were also evaluated. Grafting in solution gave as a result hydrophobic membranes with pore size diameter signficantly reduced. Such membranes lost their ultrafiltration properties. Grafting in vapor phase seems to give brush-like structure. Membranes possess hydrophilic surface and unique filtration properties in basic environment. Plasma polymerization of acrylic acid on the PSU surface creates a layer of material highly reminding pure poly(acrylic acid). Performance of such membranes was also pH-dependent showing better properties in basic solution.

Irena Gancarz

Papers

Modification of polysulfone membranes 1. CO2 plasma treatment

Modification of polysulfone membranes: 3. effect of nitrogen plasma

Modification of polysulfone membranes. 4. Ammonia plasma treatment

Modification of polysulfone membranes. 2. Plasma grafting and plasma polymerization of acrylic acid

Plasma modified polymers as a support for enzyme immobilization II. Amines plasma