Biomaterial surface modifications: Difference between revisions

Revision as of 14:57, 3 June 2015

Revision as of 06:56, 4 June 2015

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==== Plasma Treatment to Reduce Thrombogenesis ====

Ammonia plasma treatment can be used to attach amine functional groups. These functional groups lock on to anticoagulants like Heparin decreasing thrombogenicity.<ref>{{cite journal |doi=10.1002/jbm.820270614 |title=Immobilization of high-affinity heparin oligosaccharides to radiofrequency plasma-modified polyethylene |year=1993 |last1=Yuan |first1=Shengmei |last2=Szakalas-Gratzl |first2=Gyongyi |last3=Ziats |first3=Nicholas P. |last4=Jacobsen |first4=Donald W. |last5=Kottke-Marchant |first5=Kandice |last6=Marchant |first6=Roger E. |journal=Journal of Biomedical Materials Research |volume=27 |issue=6 |pages=811–9 |pmid=8408111}}</ref>

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==== Covalent Immobilization by Gas Plasma RF Glow Discharge ====

[[Polysaccharide]]s have been used as [[thin film]] coatings for biomaterial surfaces. Polysaccharides are extremely hydrophilic and will have small [[contact angle]]s. They can be used for a wide range of applications due to their wide range of compositions. They can be used to reduce the [[adsorption]] of proteins to biomaterial surfaces. Additionally, they can be used as receptor sites, targeting specific biomolecules. This can be used to activate specific biological responses.

Covalent attachment to a substrate is necessary to immobilize polysaccharides, otherwise they will rapidly desorb in a biological environment. This can be a challenge due to the fact that the majority of biomaterials do not possess the surface properties to covalently attach polysaccharides. This can be achieved by the introduction of [[amine|amine groups]] by RF glow discharge plasma. Gases used to form amine groups, including ammonia or n-heptylamine vapor, can be used to deposit a thin film coating containing surface amines. Polysaccharides must also be activated by oxidation of anhydroglucopyranoside subunits. This can be completed with sodium metaperiodate (NaIO₄). This reaction converts anhydroglucopyranoside subunits to cyclic hemiacetal structures, which can be reacted with amine groups to form a Schiff base linkage (a carbon-nitrogen double bond). These linkages are unstable and will easily [[dissociation (chemistry)|dissociate]]. Sodium cyanoborohydride (NaBH₃CN) can be used as a stabilizer by reducing the linkages back to an amine.<ref name=immobilization>{{cite journal |doi=10.1002/(SICI)1096-9918(200001)29:1<46::AID-SIA692>3.0.CO;2-6 |title=Biomedical coatings by the covalent immobilization of polysaccharides onto gas-plasma-activated polymer surfaces |year=2000 |last1=Dai |first1=Liming |last2=Stjohn |first2=Heather A. W. |last3=Bi |first3=Jingjing |last4=Zientek |first4=Paul |last5=Chatelier |first5=Ronald C. |last6=Griesser |first6=Hans J. |journal=Surface and Interface Analysis |volume=29 |pages=46–55}}</ref>

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=== Surface Cleaning ===

There are many examples of contamination of biomaterials that are specific to the preparation or manufacturing process. Additionally, nearly all surfaces are prone to contamination of organic impurities in the air. Contamination layers are usually limited to a monolayer or less of atoms and are thus only detectable by surface analysis techniques, such as XPS. It is unknown whether this sort of contamination is harmful, yet it is still regarded as contamination and will most certainly have an impact on surface properties.

Glow discharge plasma treatment is a technique that is used for cleaning contamination from biomaterial surfaces. Plasma treatment has been used for various biological evaluation studies to increase the surface energy of biomaterial surfaces, as well as cleaning.<ref name=RFGD>{{cite journal |doi=10.1002/jbm.820290411|title=Effect of parallel surface microgrooves and surface energy on cell growth |year=1995 |last1=den Braber |first1=E.T. |last2=de Ruijter |first2=J.E. |last3=Smits |first3=H.T.J |last4=Ginsel |first4=L.A. |last5=von Recum |first5=A.F. |last6=Jamsen |first6=J.A. |journal=Journal of Biomedical Materials Research |volume=29 |pages=511-518511–518 |pmid=7622536 |issue=1}}</ref>. Plasma treatment has also been proposed for [[sterilization (microbiology)|sterilization]] of biomaterials for potential implants.<ref name=glow>{{cite journal |doi=10.1002/(SICI)1097-4636(199704)35:1<49::AID-JBM6>3.0.CO;2-M |title=Glow discharge plasma treatment for surface cleaning and modification of metallic biomaterials |year=1997 |last1=Aronsson |first1=B.-O. |last2=Lausmaa |first2=J. |last3=Kasemo |first3=B. |journal=Journal of Biomedical Materials Research |volume=35 |pages=49–73 |pmid=9104698}}</ref>

[[File:Glow Plasma Discharge Schematic Polymer Chemistry.png|framed|center|Schematic of cleaning of a polymer surface using glow plasma discharge. Note the removal of adsorbed molecules and presence of dangling bonds.]]