Application of PHB

The perspective area of PHB application is the development of implanted medical devices for dental, cranio-maxillofacial, orthopedic, cardiovascu- 

The tissue reaction in vivo to implanted PHB films and medical devices was studied. In most cases, a good biocompatibility of PHB was demonstrated. In general, no acute inflammation, abscess formation, or tissue necrosis were observed in tissue surrounding of the implanted PHB materials. In addition, no tissue reactivity or cellular mobilization occurred in areas remote from the implantation site [13, 16, 31, 71]. On the one hand, it was shown that PHB elicited similar mild tissue response as PLA did [16], but on the other hand, the use of implants consisting of poly lactic acid, polyglicolic acid, and their copolymers is not without a number of sequelae related with the chronic inflammatory reactions in tissue [81-85]. 

Subcutaneous implantation of PHB films for 1 month has shown that the samples were surrounded by a well-developed, homogeneous fibrous capsule of 80-100 pm in thickness. The vascularized capsule consists primarily of connective tissue cells (mainly, round, immature fibroblasts) aligned parallel to the implant surface. A mild inflammatory reaction was manifested by the presence of mononuclear macrophages, foreign body cells, and lymphocytes. Three months after implantation, the fibrous cap- 

A substantial decrease in inflammatory cells was observed after 3 months, and tissues at the interface of the polymer were densely organized to form bundles. After 6 months of implantation, the number of inflammatory cells had decreased and the fibrous capsule, now thinned to about 80-100 pm, consisted mainly of collagen fibers, and a significantly reduced amount of connective tissue cells. A little inflammatory cells effusion was observed in the tissue adherent to the implants after 3 and 6 months of implantation [13, 16]. The biocompatibility of PHB has been demonstrated in vivo under subcutaneous implantation of PHB Aims. Tissue reaction to films from PHB of different molecular weights (300 450 1,000 kDa) implanted subcutaneously was relatively mild and did not change from tissue reaction to control glass plate [18, 31]. 

At implantation of PHB with contact to bone, the overall tissue response was favorable with a high rate of early healing and new bone formation with some indication of an osteogenic characteristic for PHB compared with other thermoplastics, such as polyethylene. Initially, there was a mixture of soft tissue, containing active fibroblasts, and rather loosely woven osteonal bone seen within 100 pm of the interface. There was no evidence of a giant cell response within the soft tissue in the early stages of implantation. With time this tissue became more orientated in the direction parallel to the implant interface. 

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The most well known application of PHB and poly(3HB-co-3HV) is as substitute for conventional, non-biodegradable plastics used for packaging purposes and derived products [21, 115, 116]. Single-use bottles for shampoos, cosmetics and biodegradable motor-oil have been manufactured from these biopolyesters by common molding techniques. Containers and cups for food products were developed similarly, and bags have been produced from blown films of the material. 

The idea of increasing the maximum temperature at which a hole can be burnt or can survive after an excursion is very important when one considers the application of PHB to ultra-high density optical storage. Room temperature hole burning has been realized so far only in the case of Sm2+ in alkaline halide crystals and in fluoride or borate glasses.28 It has been reported that an organic system, the dihydrophenazine/fluorene crystal, can be subjected to an excursion to room temperature, with hole recovery when brought back to 4 K. 

Holmes, P. A., Application of PHB a Microbially Produced Biodegradable Thermoplastic, Phys. Technol, 16, 32, 1985. 

Hippe H (1967) Aufbau und Wiederverwertung von Poly-P-hydroxybuttersaure durch Hydrogenomonas H16. Arch Mikrobiol 56 248-277 Hippe H, Schlegel HG (1967) Hydrolyse von PHBS durch intrazeUulare Depolymerase von Hydrogenomonas H16. Arch Mikrobiol 56 278-299 Holmes PA (1985) Application of PHB a microbiaUy produced biodegradable thermoplastic. Phys Technol 16 32-36... 

The present industrial applications of PHB-, or more genraaUy, PHA-based foams, are modest because their preparation is not easy, mainly due to problems of thermal degradation, which are particularly serious in this context, since they make foaming difficult and produce cell coUapse after the application of the foaming agents because of the low viscosity of the material. 

PHB finds numerous applications in packaging. It can be used to prepare films or molded objects. They are compatible with various food products like bever es, dairy, meat etc. So far, the large-scale application of PHB as packaging material is hampered by their high cost. 

P.A. Holmes, "Applications of PHB - a microbially produced biodegradable thermoplastic", Phys. TechnoL, 16, 32-36,1985. 

A detailed discussion on possible applications of PHB has been published [2], especially in medicine but considering also its optical activity and piezoelectric properties (by one order of magnitude lower than polyvinylidene fluoride but without interference from pyroelectricity due to temperature changes). Applications in various areas have been discussed not only for PHB but also for other important biodegradable plastics [77]. 

Holmes, P.A., Applications of PHB-a Microbially Produced Biodegr able Thermoplastics, Phys. Technol, 1985,16, 32-36. 

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