Biomedical polymers polyethylene

On the other hand, biomedical applications are very limited in both in vivo and in vitro conditions due to the high toxicity of these nanoparticles to the cells (You-yu et al., 2014). Therefore, nanoparticles are coated with compounds, such as natural polymers (proteins and carbohydrates) (Nair et al., 2010), synthetic organic polymers (polyethylene glycol), polyvinyl alcohol, poly-L-lactic acid. 

The final consideration to be addressed in this chapter on the choice of a polymer fortrsein medical devices is cost. Biomedical polymers can range from inexpensive (PVC, polyethylene) to extremely expensive (e.g., polymers with peptide components). A disposable catheter intended for minutes or hotus use in the body will not jrrstily an expensive polymer. On the other hand, a device implanted with the intent of a lifetime of acceptable performance might rrse an expensive polymeric component if long-term performance benefit can be demonstrated. Also, a higher priced polymer might be justified based on reduced complications. For example, as catheter-related bloodstream infections can add over 56000 to a hospital stay, a more expensive antibacterial catheter should be justified. ... 

Several known and commonly used biomedical polymers are categorised under the USP Class VI classifications. This includes polytetrafluoroethylene (Pl FE) (used in artificial ligaments and grafts and as catheter liners), fluorinated ethylene propylene (FEP) (used in electrocautery devices and fusing sleeves), PEEK (used in implantables, orthopaedic and dental devices). For Class VI materials, as defined by the USP, the most stringent testing procedures are performed. Any substance that may have leaked from the material is usually captured in extract solutions of NaCl, 5% EtOH, cotton-seed oil or polyethylene glycol. 

The most widely investigated temperature-responsive biomedical polymer is poly(A-isopropyl acrylamide) (pNIPAM). This polymer is the focus of Chapter 1 in this book, and therefore it will not be discussed in depth here. However, pNIPAM has been paired with polyampholyte copolymers and applied to nanoparticle separations (Das et al., 2008), drug delivery (Bradley, Liu, Keddie, Vincent, Burnett, 2009 Bradley, Vincent, Burnett, 2009), and tissue engineering applications (Xu et al., 2008). In a related system, latridi et al. (2011) also used the LCST-responsive properties of polyethylene glycol methacrylate (PEGMA) copolymerized with methac-rylic acid and 2-(diethylamino) ethyl methacrylate in a temperature- and pH-sensitive doxorubicin drug delivery system. However, the primary focus of this study was to demonstrate the pH-dependent release properties as discussed earlier. 

Bioerodible polymers offer a unique combination of properties that can be tailored to suit nearly any controlled drug delivery application. By far the most common bioerodible polymers employed for biomedical applications are polyesters and polyethers (e.g., polyethylene glycol), polylactide, polyglycolide and their copolymers). These polymers are biocompatible, have good mechanical properties, and have been used in... 

As mentioned above, the preparation of nanogels by addition reactions of functional macromolecular precursors is mainly used for biomedical applications. Thus, the choice of synthetic precursors for microgel formation is restricted to biocompatible materials. Moreover, as most applications are in drug delivery, the molecular weight of the gel precursors should be below the threshold for renal clearance, a value that depends on the molecular architecture and chemical nature of the polymer but that is usually smaller than 30kDa, which is set as the limit for linear PEG [97], Polymers that are mostly used and thus presented in more detail here are PEG, poly(glycidol) (PG), and polyethylene imine) (PEI). 

Specialty polymers achieve very high performance and find limited but critical use in aerospace composites, in electronic industries, as membranes for gas and liquid separations, as fire-retardant textile fabrics for firefighters and race-car drivers, and for biomedical applications (as sutures and surgical implants). The most important class of specialty plastics is polyimides. Other specialty polymers include polyetherimide, poly(amide-imide), polybismaleimides, ionic polymers, polyphosphazenes, poly(aryl ether ketones), polyarylates and related aromatic polyesters, and ultrahigh-molecular-weight polyethylene (Fig. 14.9). 

The production of polymeric materials is one of the world s major industries. Polymers are utilized in many applications because of their processability, ease of manufacture, and diverse range of properties. Many of the commonest polymers such as polyethylene, polystyrene, and polytetrafluoroethylene (PTFE) are highly hydrophobic materials rendering them unsuitable for many biomedical applications. For applications that require contact with body fluids such as blood or urine, it is necessary for the materials to be hydrophilic and to be capable of maintaining intimate contact with the fluid in question for prolonged periods of time without significant loss of functional performance. 

The application of polymeric materials in medicine is a fairly specialized area with a wide range of specific applications and requirements. Although the total volume of polymers used in this application may be small compared to the annual production of polyethylene, for example, the total amount of money spent annually on prosthetic and biomedical devices exceeds 16 billion in the United States alone. These applications include over a million dentures, nearly a half billion dental fillings, about six million contact lenses, over a million replacement joints (hip, knee, finger, etc.), about a half million plastic surgery operations (breast prosthesis, facial reconstruction, etc.), over 25,000 heart valves, and 60,000 pacemaker implantations. In addition, over AO,000 patients are on hemodialysis units (artificial kidney) on a regular basis, and over 90,000 coronary bypass operations (often using synthetic polymers) are performed each year (]J. 

Several other common industrial polymers are also used in biomedical applications [51]. Because of its low cost and easy processibility, polyethylene is frequently used in the production of catheters. High-density polyethylene is used to produce hip prostheses, where durability of the polymer is critical. Polypropylene, which has a low density and high chemical resistance, is frequently employed in syringe bodies, external prostheses, and other non-implanted medical applications. Polystyrene is used routinely in the production of tissue culture dishes, where dimensional stability and transparency are important. Styrene-butadiene copolymers or acrylonitrile-butadiene-styrene copolymers are used to produce opaque, molded items for perfusion, dialysis, syringe connections, and catheters. 

H. Balakrishnan, M.R. Husin, M.U. Wahit, M.R. Abdul, Kadir. Maleated high density polyethylene compatibilized high density polyethylene/hydroxyapatite composites for biomedical applications properties and characterization. Polym.-Plast. Technol. Eng. 52, 774-782 (2013)... 

Inc., and Teijin Ltd., which is known as Ingeo in the USA and Biofront in Japan. Another company, Purac, also produces biomedical application-oriented PLA-based materials under the PURASORB brand name. Figure 8.1 shows the synthesis, recycUng, and degradation of PLLA [13]. However, due to the recent initiation of the production of biobased polyethylene (PE) from bio-ethanol, PLLA is not the sole mass-produced biobased polymer. To forestall biobased PE and other biobased polymers that will be produced in the near future, high performance PLA-based materials must be developed to suppress their hydrolytic/thermal degradabiUty and increase their mechanical performance. 

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