Sensitization biocompatibility testing

As mentioned previously (and discussed in detail in Sec. IX), contact lens products have specific guidelines that focus on compatibility with the contact lens and biocompatibility with the cornea and conjunctiva [75], These solutions are viewed as new medical devices and require testing with the contact lenses with which they are to be used. Tests include a 21-day ocular study in rabbits and employ the appropriate types of contact lenses with which they are to be used and may include the other solutions that might be used with the lens. Additional tests to evaluate cytotoxicity potential, acute toxicity, sensitization potential (allergenicity), and risks specific to the preparation are also required [75-77], These tests are sufficient to meet requirements in the majority of countries, though testing requirements for Japan are currently much more extensive. 

Clinical analysis is one of the most important fields of analytical chemistry because of the importance to the health of the human body of the materials being analyzed. For example, because pharmaceutical products are meant to improve the health of the body, the analysis of pharmaceutical products in vitro as well as in vivo can be considered a branch of clinical analysis. Clinical analysis has two main branches research clinical analysis and routine clinical analysis. As always, it is very important to obtain the optimum conditions for the methods applied in clinical analysis. First, the methods are applied by the researcher for in vitro tests. Then, it is very important to obtain biocompatible materials for in vivo determinations. For clinical analysis, methods with high sensitivity, a low detection limit, and high selectivity are necessary. The rapidity of assurance is one of the most important characteristics of the method that is applied. 

The modified polymer beads [347] passed all of the standard battery of biocompatibility tests required by the International Organization for Standardization guidelines (ISO 10993). The tests included in vitro coagulation tests (plasma recalcification time), hemolysis study (extraction method), cytotoxicity study using the ISO elution method, etc. In in vivo experiments, extracts of the polymer beads did not elicit pyrogenic irritation or sensitization reactions in laboratory animals (acute systematic toxicity study in the mouse, acute intracutaneous reactivity study in the rabbit, rabbit pyrogen study). 

The extract dilution type of cell culture assay requires a solvent extraction of the biomaterial under consideration and testing of this extract, most commonly at various dilutions, for evidence of cytotoxicity and cellular interaction. This type of cell culture assay finds its most common use in providing information for regulatory compliance. As identified in the preceding Materials for Medical Devices section and in Table 1, low-molecular-weight extractables are of concern regarding biocompatibility. The extraction assay, carried out with a series of solvents that are hydrophilic and hydrophobic, permits examination of the potential cytotoxicity of extracts and the identification of materials within a biomaterial that may be cytotoxic. These types of assays ultimately permit identification and characterization of cytotoxic materials within biomaterials or the lack of cytotoxicity, as well as providing correlation with in vivo assays such as sensitization, irritation, intracutaneous (intradermal) reactivity, and other tests where the in vivo injection of extracts is required. 

Antigenicity Test (BPAT), and the dermal sensitization study (a maximization method) were used. The scoring for the dermal sensitization study, shown in Table 9.4 for poly(GGAP), is the same as in Table 9.5 for the intracuta-neous toxicity study. In the latter case, there simply is neither erythema (redness) nor edema (swelling) due to injection of the polymer. In the former case, the test polymer was as innocuous as the negative control of salt water. Obviously, these polymers are remarkably biocompatible. 

The biocompatibility tests brought forth die lack of a sensitizing, irritating and cytotoxic potential of the tested dressing (bandage). ... 

A sensitive and reproductive test of biocompatibility seems to be the cultivation of cells with an increasing content of fine metal powders (<20 xm). The survival rate is measured after a constant exposure time. The limit of toxicity C50 is defined as the value ( xg/ml) of the powder concentration which produces a dying off of 50% of the cells. (The results can be found in the chapters related to biocompatibility.)... 

Biocompatibility, especially safety and mildness to skin, are very important properties of interest for the application of AAS. Animal tests such as the Draise method for primary eye and skin irritation and the maximization test for sensitization have been widely used in the past. Recently, an alternative or in vitro test was actively developed for the purpose of refining, reducing, and replacing the animal test. Although there are still no perfect alternatives... 

Table II. Biocompatibility Test Methods ISO 10993-5 Cytotoxicity ISO 10993-10 Sensitization ISO 10993-10 Irritation Others...

A number of important characteristics must be taken into consideration in addition to the efficacy of the products antimicrobial treatment. Biocompatibility is one of those characteristics. According to the International Organization for Standardization (ISO) 10993-1, Biological Testing of Medical and Dental Materials and Devices, all device materials must undergo cytotoxicity, sensitization and irritation testing as a minimum. 

The three areas of biocompatibility testing, cytotoxicity, sensitization, and irritation mentioned above are by no means all the tests that may be needed when determining the toxicity of a treated medical device. These three test areas are mandated by ISO 10993-1, Guidance on the Selection of Tests and its FDA counterpart, blue book memorandum G95-1, however, other tests listed in this standard may need consideration and are dependent mainly on the device and where it will be used in the human body. 

P4HB and P3HB-4HB have been evaluated in preclinical tests reconunended by the FDA for medical devices. These tests include cytotoxicity, sensitization, irritation and intracutaneous reactivity, hemocompatibility, and implantation. Thus for example, P4HB films and sutures were subjected to a complete series of biocompatibility test protocols that were performed in accordance with the FDA s GLP regulations as set forth in 21 CFR, part 58, as well as ISO 10993-1. The test results confirmed that P4HB is nontoxic and biocompatible (Martin DP, personal communication). 

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