Biomedical applications conductivity

Chemical structure of monomers and intermediates was confirmed by FT-IR and FT-NMR. Molecular weight distribution of polymers was assessed by GPC and intrinsic viscosity. The thermal property was examined by differential scanning calorimetry. The hydrolytic stability of the polymers was studied under in vitro conditions. With controlled drug delivery as one of the biomedical applications in mind, release studies of 5-fluorouracil and methotrexate from two of these polymers were also conducted. 

Drug Release from PHEMA-l-PIB Networks. Amphiphilic networks due to their distinct microphase separated hydrophobic-hydrophilic domain structure posses potential for biomedical applications. Similar microphase separated materials such as poly(HEMA- -styrene-6-HEMA), poly(HEMA-6-dimethylsiloxane- -HEMA), and poly(HEMA-6-butadiene- -HEMA) triblock copolymers have demonstrated better antithromogenic properties to any of the respective homopolymers (5-S). Amphiphilic networks are speculated to demonstrate better biocompatibility than either PIB or PHEMA because of their hydrophilic-hydrophobic microdomain structure. These unique structures may also be useful as swellable drug delivery matrices for both hydrophilic and lipophilic drugs due to their amphiphilic nature. Preliminary experiments with theophylline as a model for a water soluble drug were conducted to determine the release characteristics of the system. Experiments with lipophilic drugs are the subject of ongoing research. 

Nucleic acids, DNA and RNA, are attractive biopolymers that can be used for biomedical applications [175,176], nanostructure fabrication [177,178], computing [179,180], and materials for electron-conduction [181,182]. Immobilization of DNA and RNA in well-defined nanostructures would be one of the most unique subjects in current nanotechnology. Unfortunately, a silica surface cannot usually adsorb duplex DNA in aqueous solution due to the electrostatic repulsion between the silica surface and polyanionic DNA. However, Fujiwara et al. recently found that duplex DNA in protonated phosphoric acid form can adsorb on mesoporous silicates, even in low-salt aqueous solution [183]. The DNA adsorption behavior depended much on the pore size of the mesoporous silica. Plausible models of DNA accommodation in mesopore silica channels are depicted in Figure 4.20. Inclusion of duplex DNA in mesoporous silicates with larger pores, around 3.8 nm diameter, would be accompanied by the formation of four water monolayers on the silica surface of the mesoporous inner channel (Figure 4.20A), where sufficient quantities of Si—OH groups remained after solvent extraction of the template (not by calcination). 

Acknowledgements This review article is dedicated to Dr. Takayuki Ohtsu (Professor Emeritus, Osaka City University) who pioneered photoiniferter polymerization. A large number of studies by his research group stimulated and directed me to conduct a series of siuface microarchitectiu e studies focusing on biomedical applications. The author also appreciates Professor Rainer Iordan, volume editor of this special issue, who carefully edited this article with patience. 

Traditional applications for laiices arc adhesives, binders for libers and paniculate matter, protective and decorative coatings, dipped goods, loam, paper coatings, hackings for carpet and upholstery, modifiers for bitumens and concrele. thread, and textile modifiers. More recent applications include biomedical applications as protein immobilizers, visual detectors in immunoassays, as release agents, in electronic applications as photoresists for circuit boards, in batteries, conductive paint, copy machines, and as key components in molecular electronic devices. 

Applications. Polymers with small alkyl substituents, particularly (13), are ideal candidates for elastomer formulation because of quite low temperature flexibility, hydrolytic and chemical stability, and high temperature stability. The ability to readily incorporate other substituents (in addition to methyl), particularly vinyl groups, should provide for conventional cure sites. In light of the biocompatibility of polysiloxanes and P—O- and P—N-substituted polyphosphazenes, poly(alkyl/arylphosphazenes) are also likely to be biocompatible polymers. Therefore, biomedical applications can also be envisaged for (3). A third potential application is in the area of solid-state batteries. The first steps toward ionic conductivity have been observed with polymers (13) and (15) using lithium and silver salts (78). 

As carboranes are chemically stable and exhibit low toxicity to humans, biomedical applications of carborane systems, including cobaltacarboranes, have slowly emerged. The boron isotope °B accounts for about 20% of boron in nature, and it has the ability to capture a slow neutron and release an a-particle (equation 65). This reaction, if conducted in live tissue, will kill the immediate cell, but not its neighbors. Although early studies were done with toxic boron compounds, carboranes, with their low toxicities and high boron content, have been proven to be good substrates for boron capture neutron therapy (BCNT). Cobaltacarboranes have been employed in radioimmunodetection and radioimmunotherapy as well. ... 

Gum Arabica is a natural plant gum that exudates a carbohydrate type and is an electroactive biopolymer. Gum Arabica and its complexes have potential applications in developing ionic devices such as batteries, sensors, bio-sensors, and other electronic applications, in addition to solar material, energy storage material and nanoscience. Biopolymers obtained from bacteria are rapidly emerging because they are biodegradable and available in abundance. Simple methods are being developed to grow and harvest the polymers to exploit them for numerous industrial and biomedical applications. Electronic structures and conduction properties of biopolymers are also discussed in Part III. 

P. L.Nayak is an eminent polymer scientist and is now the Chairman of P.L.Nayak Research Foundation, Cuttack, India. He possesses both PhD and DSc Degrees in Polymer Science and Technology. He has done extensive research work on biopolymers, polymers for biomedical applications, nanomedicine, nanobiotechnology, controlled drug delivery and conducting polymers. About 80 of his students have been awarded a PhD Degree. He has published more than 400 peer reviewed research papers in international journals in various fields of Polymer Science and Technology. 

After qualification by acute and chronic biocompatibility and biodurability evaluations, clinical studies were conducted to confirm that the implants were highly durable. Medical grade high performance silicone elastomer has now become used in various biomedical applications including construction of flexible bone and joint implants as designed by Swanson ( 9) (Figures... 

Furthermore, composite films of nanofibrillated cellulose (NFC)/Ppy and NFC/ PPy-silver NP are a suitable candidate for use in biomedical applications. Due to the electrical conductivity and strong antimicrobial activity of these silver composites, they can be used in various applications, in particular, biomedical treatments and diagnostics. 

Robots will be a part of our everyday lives in the near future. Biomedical applications of both professional and personal service robots are becoming increasingly common. A survey conducted by the United Nations Economic Comission for Europe (UNECE) in conjunction with the International Federation of Robotics (IFR) [2004] estimated that a stock of 21,000 professional service robots at the end of 2003 and projected 75,000 by the end of 2007. These include medical robots, underwater robots, surveillance robots, demolition robots, and many other types of robots for carrying out a multitude of tasks. Medical robots comprised 12% of the 2003 estimates. 

Table 18.1 Sample of the variety of polymer, dopant and solvent combinations investigated for conducting polymers in biomedical applications...

The unique combination of high mechanical stability, electrical conductivity, and surface area make carbon nanotubes (CNTs) a popular material for a wide range of biomedical applications, from microbial fuel cells to biochemical sensors [91-94]. Accordingly, CP composites have been investigated to synergize both mechanical and electrical properties of CNTs. 

CPs designed for biomedical applications generally require good electrical conductivity, physicochemical and mechanical stability, and biocompatibility to effectively interact with biological system. A wide range of analytical techniques to characterize the feasibility of conducting polymers as biomaterials are summarized here. 

Quantitative conductivity of a CP sample is typically measured by a four-point probe technique. CPs for biomedical applications have typically yielded conductivities of between 1 and 200 S cm [44—46,49,50,138]. However, four-point probe measurements can be problematic, as the CP film must be removed from the substrate prior to testing. There have been a number of different methods used for film removal, including doublesided tape, razor blades, and backing the film with polydimethylsiloxane (PDMS) [61]. Fonner et al. found the double-sided tape technique to be most effective, as the CP film was removed firom the substrate undamaged and the presence of the tape did not affect the conductivity measurement [61]. 

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