Biocompatibihty/biocompatible

Rihova, B. Biocompatibihty of biomateiials hemocompatibility, immunocompat-ibility and biocompatibility of sohd polymeric materials and soluble taigetable polymeric carriers. Adv. Drug. Delivery Rev. 1996,21, 157-176. 

Although FDA does not have specific guidance for biocompatibility testing of polymers, the hitemational Standard ISO-10993 is recommended by the FDA for biological evaluation of biomedical devices. ISO-10993 entails 20 detailed standards to evaluate the biocompatibihty of a material device prior to clinical testing. These tests include both in vitro and in vivo assays as well as physicochemical characterization... 

In vitro models are the first approach used to understand the ceU-substrate interaction and biocompatibihty of the materials. Cell cultures are ideal systems for the analysis of a specific cell type under certain conditions because they avoid the complexity of the numerous variables involved in in vivo studies. It is not possible, however, to directly extrapolate in vitro results to in vivo results. Indeed, in a previous study performed with two CaP glass formulations with different solubihties, in vitro studies indicated that the differences in solubility affect cell cultures [23,43]. However, in vivo, the differences in solubility were not evident and the two materials presented good biocompat-ibiUty. 

Caleium phosphate cements (CPCs) have been investigated extensively as injectable bone replacement biomaterials due to their similar chemical composition to the mineral component of bone. A Umitation of CPCs is their brittle mechanical properties and slow degradation in vivo Therefore, enhancing the mechanical properties, injectability, and rate of cellular infiltration and remodeling of CPCs while preserving their favorable biocompatibility is an important and active area of research. While ceramic biomaterials are discussed in greater detail in Chapter 2, the biocompatibihty of conventional CPCs, as well as the implications of recent advancements on the biocompatibility of these biomaterials, will be reviewed in this chapter. 

Biocompatibility as defined in Section 2.5 is a main prerequisite for the proper and safe use of medical devices consisting of a single material or material composition. In Section 4.5.1, it was demonstrated that the biophysical characterization of material surfaces only draws attention to some aspects of their response to biological systems. In order to assess biocompatibility for a device or a material, it is necessary to do a battery of tests depending on its intended use, with body contact ranging from transient skin contact to contact with blood to permanent implantation. Biocompatibihty is usually examined with three types of biological tests in vitro tests, animal experiments (in vivo tests), and clinical tests. 

For hemodialysis membranes, biocompatibility is the primary requirement. It is known that surface properties such as surface roughness play important roles in determining membrane biocompatibihty. It has also been reported that for a given material, smoother surfaces are more biocompatible [64]. Hence, the sinfaces of three different commercial hollow fibers were studied by AFM to compare their roughness parameters. Figures 4.42 and 4.43 show AFM images of inner and outer surfaces, re-... 

Fig. 10.20 presents the release of Ag from polyester/Ag (160 s) and polyester/ Ag-TaN (20 s). For the polyester/Ag samples up to the eighth cycle, the level of Ag release drops from 8 to about 4 ppb/cm, and for the Ag-TaN (20 s) sample, Ag release drops from 4 to about 1 ppb/cm. TaN sputtered on polyester will therefore improve the biocompatibUity level of Ag because the disinfection process occurs at a lower Ag release level. The TaN is known for its excellent biocompatibility, which makes Ag-TaN an important material in biorelated applications.This feature makes polyester—Ag-TaN important to biochemical applications in implants because of nitride TaN-proven biocompatibihty concomitant with observed accelerated bacterial... 

SU-8 was originally developed as a photoresist for the microelectronics industry, to provide a high-resolution mask for fabrication of semiconductor devices. It is now mainly used in the fabrication of microfluidics (mainly via soft lithography) and micro-electromechanical systems (MEMS) (Fig. 13.3) and bio-MEMS applications [8]. This stems from its excellent biocompatibihty—it is one of the most biocompatible materials known. SU-8 is now also used in conjunction with imprinting techniques such as nanoimprint lithography [2]. 

It is evident that particle-based vectors have yet to reach their envisioned capabilities. Research focus has shifted from viral vectors, which continue to offer the highest transfection efficiency, through synthetic polymer and Hposome systems, commercially available and suitable for in vitro transfection, to natural compounds in search of transfection using a biodegradable vector. The enhanced biocompatibility of peptides and natural biopolymers will certainly drive research as the quest for suitable in vivo vectors continues, though the balance between attaining biocompatibihty while preserving transfection efficiency has yet to be found. 

Cell culture testing is used widely in vitro to evaluate the biocompatibihty of HA samples. For this, several osteoblast cell lines have been developed to assess biomaterials performance in vitro, including a murine osteoblastic cell hne (MC3T3-El) [121], a human osteoblastic precursor cell line (OPCl) [122] and a human osteoblast cell line (hFOB 1.19) [123]. Osteoblast cells interact differently with material structures, depending on the combinations of chemical, structural and environmental variables. The biocompatibility of HA surfaces can be assessed using ceU-material interaction studies such as attachment, proliferation and differentiation. Cell proliferation on HA samples is normally investigated with a mitochondrial (MTT) assay, which permits the quantitative estimation of the number of living cells on a material. 

Material-tissue interactions are best described by the term biocompatibility. Generally defined, biocompatibihty is the ability of a material to perform with an appropriate host response in a specific application [96]. This implies that any material placed into a body will not be inert but will interact with the tissue. The biological response of a material is basically dependent on three factors the material properties, the host characteristics, and the functional demands on the material. Therefore, the biocompatibility of a material can only be assessed on the basis of its specific host function and has to be uniquely defined for each application. 

Poly(ethylene glycol) (PEG) is a water-soluble and nontoxic material with no antigenicity and immunogenicity. PEG is considered as polymer that can prevent protein absorption and improve the biocompatibility for blood contact compound [6]. Additionally, PEG was also introduced into several polymers such as PCL, polylactide (PLA) [7], poly(glycolic acid) (PGA), or their copolyesters (PLGA) [8] to increase the biocompatibihty and used as drag carriers, which allows PEG to be used for clinical applications. 

The hydrophobic nature of polysiloxanes has limited their uses in biomedical appHcations, especially in those involving biocompatible devices. Obviously, increasing the hydrophilicity of any polymer surface improves its wettability and this, in turn, improves biocompatibihty. 

Facial prostheses may fail due to the limitations in the properties of existing materials, especially the biocompatibility. Biocompatibility of PDMS elastomers (LIM 6050, MDX 4-4210, Silastic 732) was tested in subcutaneous tissue of rats [85]. A histomorphometric evaluation was conducted to analyze the biocompatibihty of the implants. Mesenchymal cells, eosinophils, and foreign-body giant cells were counted. Initially, all implanted materials exhibited an acceptable tissue inflammatory response, with tissue reactions varying from light to moderate. Afterward, a fibrous capsule around the sihcone was observed. In conclusion, the tested silicones were found biocompatible and suitable to use for implantation in both medical and dental areas. Their prosthetic indication is conditioned to their physical properties. Solid sihcone is easier to adapt and does not suffer apparent modifications inside the tissues [85]. 

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