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Electrospray deposition of protein films
BIOMATERIALS FOCUS
RESEARCH NEWS
With the growth in the aged population and the need to extend average individual healthspan, biomaterials have an increasingly important role in the development of new generation medical devices, drug delivery systems, and medical diagnostic technologies. This column seeks to provide an insight into the latest developments in biomedical materials and related technologies through brief synopses and expert commentaries of recent presentations, publications, and patents. Andrew Lloyd, University of Brighton.
Alternatives to PVC MEDICAL MATERIALS
Platelet adhesion on PE and PE/PMPC alloy membranes. (© 2004 Elsevier Ltd.)
In recent years, there has been increasing environmental concern over the use of poly(vinyl chloride) or PVC materials in the manufacture of medical devices, such as extracorporeal tubing and blood bags. To produce flexible PVC for such applications, plasticizers are compounded with the PVC. Recent reports suggest that some of these plasticizers leach out during use, leading to reduced biocompatibility and possible complications associated with the estrogenic-like properties of some of the additives. In addition, concern has been expressed over the increased level of dioxins in the atmosphere because of the incineration of PVC products. There is, therefore, considerable interest in the development of materials that use alternative plasticizers or are fabricated from completely different biocompatible materials.
Polyethylene (PE) offers significant advantages over PVC as no toxic waste products are formed upon incineration. Although PE has been used in various medical devices, its use in blood-contacting applications is limited by its rapid contact activation of the clotting cascade, which leads to thrombus formation on the material surface. To improve biocompatibility, Kazuhiko Ishihara and colleagues from The University of Tokyo and Tokyo Medical and Dental University, Japan have investigated a novel polymer alloy of PE and biocompatible poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) [Ishihara et al., Biomaterials (2004) 25, 1115]. The mixed polymer system is produced by dissolving PE and PMPC in xylene and n-butanol, respectively. The polymers are then mixed and a transparent solution is obtained through heating. Polymer films are obtained by solvent evaporation, vacuum drying, and thermal curing under pressure. Examination of the surface of the material using scanning electron microscopy, X-ray photoelectron spectroscopy, and dynamic contact angle analysis demonstrates that polar phosphorylcholine groups are present across the surface of the alloy. Platelet adhesion to the PE/PMPC alloy is markedly reduced compared with the original PE material. The study suggests that the new alloy may offer a useful alternative to PVC for blood-contacting medical device applications.
Electrospray deposition of protein films SURFACE ENGINEERING Protein conditioning of implanted materials has long been known to dictate their biocompatibility. The adsorption, denaturation, and ligation of proteins plays a key role in determining whether a material will initiate thrombus formation, stimulate an inflammatory response, or provide a natural substrate for tissue integration. The surface engineering of biomedical devices with proteins has the potential to generate an extracellular matrix mimic and enhance integration of the materials into the body. A key challenge will be the controlled deposition of protein while maintaining its conformational structure.
Atomic force microscopy images of electrospray-deposited thin films. (© 2004 Elsevier Ltd.)
Ikuo Uematsu and colleagues from Tokyo Institute of Technology, The Institute of Physical and Chemical Research, and Fuence Co. Ltd. in Japan have demonstrated the electrospray deposition of α-lactalbumin, while
maintaining its biological activity [Uematsu et al., J. Colloid Interface Sci. (2004) 269, 336]. Scanning electron and atomic force microscopy analysis show that the protein films have a fine structure with pores of
40-600 nm. Although further work will be required before this technique could be more widely used, electrospray deposition offers the potential to produce controlled, nano-engineered surfaces for biomedical applications.
February 2004
19
RESEARCH NEWS
With the growth in the aged population and the need to extend average individual healthspan, biomaterials have an increasingly important role in the development of new generation medical devices, drug delivery systems, and medical diagnostic technologies. This column seeks to provide an insight into the latest developments in biomedical materials and related technologies through brief synopses and expert commentaries of recent presentations, publications, and patents. Andrew Lloyd, University of Brighton.
Alternatives to PVC MEDICAL MATERIALS
Platelet adhesion on PE and PE/PMPC alloy membranes. (© 2004 Elsevier Ltd.)
In recent years, there has been increasing environmental concern over the use of poly(vinyl chloride) or PVC materials in the manufacture of medical devices, such as extracorporeal tubing and blood bags. To produce flexible PVC for such applications, plasticizers are compounded with the PVC. Recent reports suggest that some of these plasticizers leach out during use, leading to reduced biocompatibility and possible complications associated with the estrogenic-like properties of some of the additives. In addition, concern has been expressed over the increased level of dioxins in the atmosphere because of the incineration of PVC products. There is, therefore, considerable interest in the development of materials that use alternative plasticizers or are fabricated from completely different biocompatible materials.
Polyethylene (PE) offers significant advantages over PVC as no toxic waste products are formed upon incineration. Although PE has been used in various medical devices, its use in blood-contacting applications is limited by its rapid contact activation of the clotting cascade, which leads to thrombus formation on the material surface. To improve biocompatibility, Kazuhiko Ishihara and colleagues from The University of Tokyo and Tokyo Medical and Dental University, Japan have investigated a novel polymer alloy of PE and biocompatible poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) [Ishihara et al., Biomaterials (2004) 25, 1115]. The mixed polymer system is produced by dissolving PE and PMPC in xylene and n-butanol, respectively. The polymers are then mixed and a transparent solution is obtained through heating. Polymer films are obtained by solvent evaporation, vacuum drying, and thermal curing under pressure. Examination of the surface of the material using scanning electron microscopy, X-ray photoelectron spectroscopy, and dynamic contact angle analysis demonstrates that polar phosphorylcholine groups are present across the surface of the alloy. Platelet adhesion to the PE/PMPC alloy is markedly reduced compared with the original PE material. The study suggests that the new alloy may offer a useful alternative to PVC for blood-contacting medical device applications.
Electrospray deposition of protein films SURFACE ENGINEERING Protein conditioning of implanted materials has long been known to dictate their biocompatibility. The adsorption, denaturation, and ligation of proteins plays a key role in determining whether a material will initiate thrombus formation, stimulate an inflammatory response, or provide a natural substrate for tissue integration. The surface engineering of biomedical devices with proteins has the potential to generate an extracellular matrix mimic and enhance integration of the materials into the body. A key challenge will be the controlled deposition of protein while maintaining its conformational structure.
Atomic force microscopy images of electrospray-deposited thin films. (© 2004 Elsevier Ltd.)
Ikuo Uematsu and colleagues from Tokyo Institute of Technology, The Institute of Physical and Chemical Research, and Fuence Co. Ltd. in Japan have demonstrated the electrospray deposition of α-lactalbumin, while
maintaining its biological activity [Uematsu et al., J. Colloid Interface Sci. (2004) 269, 336]. Scanning electron and atomic force microscopy analysis show that the protein films have a fine structure with pores of
40-600 nm. Although further work will be required before this technique could be more widely used, electrospray deposition offers the potential to produce controlled, nano-engineered surfaces for biomedical applications.
February 2004
19