Detail of GB/T 16886.6-2022

Introduction of GB/T 16886.6-2022

Biological evaluation of medical devices - Part 6: Tests for local effects after implantation 1 Scope This document specifies test methods for the assessment of the local effects after implantation of biomaterials intended for use in medical devices. This document applies to materials that are ——solid and non-solid, such as porous materials, liquids, gels, pastes, and particulates, and ——non-absorbable, and ——degradable and/or absorbable, which may be solid or non-solid. This document can also be applied to medical devices that are intended to be used topically in clinical indications where the surface or lining might have been breached, in order to evaluate local tissue responses. Note 1: The test sample is implanted into a site and animal species appropriate for the evaluation of the biological safety of the material. The objective of the test methods is to characterize the history and evolution of the tissue response after implantation of a medical device/biomaterial including final integration or absorption/degradation of the material. In particular for degradable/absorbable materials, the degradation characteristics of the material and the resulting tissue response should be determined. The local effects are evaluated by a comparison of the tissue response caused by a test sample to that caused by control materials used in medical devices whose clinical acceptability and biocompatibility characteristics have been established. These implantation tests are not intended to evaluate or determine the performance of the test sample in terms of mechanical or functional loading. This document does not deal with systemic toxicity, carcinogenicity, teratogenicity or mutagenicity. Note 2: The long-term implantation studies intended for evaluation of local biological effects might provide insight into some information about systemic toxicity, carcinogenicity, teratogenicity or mutagenicity. Systemic toxicity studies conducted by implantation might satisfy the requirements of this document. When conducting combined studies for evaluating local effects and systemic effects, the requirements of both standards is to be fulfilled. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute indispensable provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition (including any amendments) applies. ISO 10993-1 Biological evaluation of medical devices - Part 1: Evaluation and testing within a risk management process Note: GB/T 16886.1-2022 Biological evaluation of medical devices - Part 1: Evaluation and testing within a risk management process (ISO 10993-1: 2018, IDT). ISO 10993-2 Biological evaluation of medical devices - Part 2: Animal welfare requirements Note: GB/T 16886.2-2011 Biological evaluation of medical devices - Part 2: Animal welfare requirements (ISO 10993-2: 2006, IDT). ISO 10993-4 Biological evaluation of medical devices - Part 4: Selection of tests for interactions with blood Note: GB/T 16886.4-2022 Biological evaluation of medical devices - Part 4: Selection of tests for interactions with blood (ISO 10993-4:2017, IDT) ISO 10993-12 Biological evaluation of medical devices - Part 12: Sample preparation and reference materials Note: GB/T 16886.12-2017 Biological evaluation of medical devices - Part 12: Sample preparation and reference materials (ISO 10993-12:2012, IDT) ISO 10993-16 Biological evaluation of medical devices - Part 16: Toxicokinetic study design for degradation products and leachables Note: GB/T 16886.16-2021 Biological evaluation of medical devices - Part 16: Toxicokinetic study design for degradation products and leachables (ISO 10993-16:2017, IDT) 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 10993-1, ISO 10993-2, ISO 10993-12, ISO 10993-16 and the following apply. 3.1 absorb/absorption action of a non-endogenous (foreign) material or substance, or its decomposition products passing through or being assimilated by cells and/or tissue over time 3.2 degradation decomposition of a material [Source: ISO 10993-9:2009, 3.1] 3.3 degradation product any intermediate or final by-product which results from the physical, metabolic, and/or chemical decomposition of a material or substance [Source: ISO/TR 37137:2014, 2.2, modified] 3.4 degrade to physically, metabolically, and/or chemically decompose a material or substance [Source: ISO/TR 37137:2014, 2.3] 3.5 biomaterial material or substance intended to interface with biological systems to evaluate, treat, augment or replace any tissue, organ or function of the body [Source: European Society Biomaterials Conference II] 4 Common provisions for implantation test methods 4.1 General It is important that the study be planned in sufficient detail such that all relevant information can be extracted from the use of each animal and each study (see ISO 10993-2, ISO 10993-11 and ISO 10993-16) All animal studies shall be performed in a facility approved by a nationally recognized organization and in accordance with all appropriate regulations dealing with laboratory animal welfare to comply with the requirements of ISO 10993-2. These studies shall be performed under good laboratory practices or other recognized quality assurance systems. The provisions of this Clause shall apply to the test methods specified in Annex A, Annex B, Annex C, and Annex D. 4.2 Preparation of samples for implantation 4.2.1 Test sample and reference or control material preparation shall be in accordance with ISO 10993-12. The implant size and shape shall be documented and justified. Test samples for various implant sites are described in Annex A, Annex B, Annex C, and Annex D. Physical characteristics (such as form, density, hardness, surface) can influence the character of the tissue response to the test material and shall be recorded and taken into account when the response is characterized. Control articles should be matched as closely as reasonably possible for physical characteristics. 4.2.2 Each implant sample shall be manufactured, processed, cleaned of contaminants, and sterilized by the method intended for the final product and this shall be confirmed in the study documentation. After final preparation and sterilization, the implant samples shall be handled aseptically and in such a way as to ensure that they are not damaged or contaminated in any way prior to or during implantation. 4.2.3 For materials used as scaffolds for tissue-engineered medical products, it may be appropriate not to use the final preparation pre-populated with cells and/or proteins, as the immune reaction of the animal to the cellular/protein components of such products and the reaction of the cells to the animal may interfere with the resulting local tissue response, making it difficult to interpret. 4.2.4 For composite materials (e.g. bone cements, dental materials), the components may be mixed before use and allowed to set before implantation. For multicomponent materials designed to be cured prior to placement, the components may be mixed before use and allowed to set before implantation. However, materials that are designed to polymerize in situ (e.g. bone cements, many dental materials) shall be introduced in a manner such that in situ polymerization occurs. The procedure used shall be documented and justified. 4.2.5 Non-solid materials (including powders) may be contained in open-ended cylindrical tubes for the purpose of testing for local effects after implantation (see ISO 10993-12 for the selection of materials for tubes). Prepare the test material according to the manufacturer’s instructions and insert the material into the tube until level with the end, taking care not to contaminate the outer surface of the tube with the test material. If contamination occurs, the sample shall not be implanted. Avoid entrapment of air in the tube and ensure that the end surfaces of the inserted material in the tube and the tube ends are smooth. Polyethylene (PE), polypropylene (PP), or polytetrafluoroethylene (PTFE) tubes are commonly used for this purpose. PE tubes can be deformed by autoclaving. 4.2.6 Evaluation shall be performed by comparing the tissue reaction to that of a similar sample/material whose clinical acceptability and biocompatibility characteristics have been established. Note: For further guidance, see ISO 10993-12. 4.2.7 The physical characteristics such as shape, and especially the surface condition of the control(s), shall be as similar to that of the implant test samples as is practical, with any deviations being explained and justified. When the test material is contained in a tube, the control shall be of the same material as the tube and have the same diameter as the outer diameter of the tube. The choice of the control rod or tube shall be documented and justified. 4.2.8 For implantation studies, the amount or size of the test and control sample shall be documented. 4.3 Study design For devices comprising/composed of two or more different materials, the test articles should be of similar composition or multiple implants may be needed, e.g. if a device is made of HDPE and titanium then the test article should be made of HDPE and titanium. 5 Test methods, general aspects 5.1 Tissue and implantation site 5.1.1 The test sample shall be implanted into the tissues most relevant to the intended clinical use of the material. The justification for the choice of sample numbers, tissue and implantation sites shall be documented. Test methods for various implantation sites are given in Annex A, Annex B, Annex C, and Annex D. If other implantation sites are chosen, the general scientific principles behind the test methods described in Annex A, Annex B, Annex C, and Annex D shall still be adhered to and the justification provided. Note: For some devices, there are vertical standards prescribing specific implant studies to evaluate local tissue responses, e.g. intraocular lens implant and dental usage tests. These studies can be used to satisfy the requirements in this document. 5.1.2 For absorbable materials, the implantation site shall be marked in a manner suitable for identification of the site at the end of the designated time periods. The use of a non-invasive permanent skin marker and/or a template marking the placement of the sample is recommended for short-term study intervals only. In most circumstances, a location marker comprised of an appropriate nonabsorbable negative control (e.g. HDPE 1mm by 2mm by 5mm, PP suture, gold band, clips) may be used to identify the location of the implant site. These location markers can be removed without inducing artefacts to the test article-tissue interface prior to histology processing. Exceptionally, a sham surgical procedure might be used to evaluate the impact of the procedure on the tissue involved; in these cases, the specific justification shall be provided. 5.2 Animals 5.2.1 All aspects of animal care and accommodation shall be in accordance with ISO 10993-2. In general, small laboratory animals such as mice, rats, hamsters, or rabbits are preferred. 5.2.2 The use of larger animals may be justified based upon special scientific considerations of the particular biomaterial under study, or if needed to accommodate implant size, with whole device testing. 5.2.3 Select an animal species in line with the principles set out in ISO 10993-2, giving due consideration to the size of the implant test samples, the number of implants per animal, the intended duration of the test in relation to the expected lifespan of the animals, as well as potential species’ differences regarding biological response. 5.2.4 For short-term testing, animals such as rodents or rabbits are commonly used. For long-term testing, animals such as rodents, rabbits, dogs, sheep, goats, pigs, and other animals with a relatively long life expectancy are suitable. 5.2.5 Before starting an animal study with degradable materials, relevant information from in vitro degradation studies should be considered. For absorbable materials, a pilot study in rodents may be considered to determine the expected rate of degradation before embarking on studies on larger animals. 5.2.6 The samples of test and control materials shall be implanted under the same conditions in animals of the same species and of the same age, sex, and strain in corresponding anatomical sites. The number and size of implants inserted into an animal depends on the size of the species and the anatomical location. Whenever possible, the reference control and the test samples should be implanted into the same animal. 5.2.7 However, when a neuroimplantation study (see Annex D) is conducted or when the local effects after implantation are investigated as part of a systemic toxicity study by implantation, control and test samples shall not be placed in the same animal. 5.3 Test periods 5.3.1 The test period shall be determined by the likely clinical exposure time or be continued until or beyond when a steady-state with respect to the biological response has been reached. The time points selected shall be explained and justified. 5.3.2 For non-absorbable materials, the short-term responses are normally assessed from 1 week up to 4 weeks and the long-term responses in tests exceeding 12 weeks. The local biological response to implanted materials depends both on the properties of the materials and on the response to the associated trauma of surgery. The tissue configuration in the vicinity of an implant changes with the time elapsed after surgery. During the first two weeks after implantation, the reaction due to the surgical procedure itself may be difficult to distinguish from the tissue reaction evoked by the implant. In muscle and connective tissue, depending on the species, and the severity of the surgical trauma, a steady-state is seen in the cell population after 9 weeks to 12 weeks. Implantation in bone tissue may need longer observation periods before a steady-state is reached. 5.3.3 For absorbable materials, the test period shall be related to the estimated degradation time of the test product at a clinically relevant implantation site. When determining the time points for sample evaluation, an estimation of the degradation time shall be made. This can be accomplished in vitro by real-time or accelerated degradation studies or in certain circumstances by mathematical modelling. In general, study duration should extend up to or beyond the point of complete absorption. The evaluation period for absorbable materials will depend in part on the degradation rate of the materials. Study intervals should span a significant portion of the degradation time frame for the implant, and shall include, as a minimum, the following time points: a) early time frame (where there is no or minimal degradation)——For absorbable materials, usually a study interval of between 1 week and 2 weeks post-implantation should be used to assess the early tissue response. b) mid time frame (when degradation is taking place)——Subsequent study intervals for absorbable devices should be guided by the degradation profile of the specific absorbable material. The target interval should allow assessment of histological response when the tissue response is expected to be most pronounced (e.g. substantial structural disruption and/or fragmentation of the device is most likely to occur). Implants with longer-term degradation profiles may require multiple assessment time points, with intervals targeted in accordance with the expected pattern of degradation. c) when a device with multiple materials with differing absorption rates is implanted, implant intervals reflecting the degradation profile of those components should be included. d) late time frame (when the implant is essentially absorbed)——This interval is targeted to observe when minimal amounts of the absorbable component remain at the implant site. Gross and microscopic evaluation after complete implant absorption is highly desirable. However, in the absence of complete absorption, the overall data collected should be sufficient to allow characterization of the local effects after implantation if: ——the affected tissue’s response, structure, and function have achieved an acceptable steady-state condition, and ——the absorbable material and/or its degradation products are in a state of limited visually-identifiable presence.

Contents of GB/T 16886.6-2022

Foreword i Introduction iii 1 Scope 2 Normative references 3 Terms and definitions 4 Common provisions for implantation test methods 5 Test methods, general aspects 6 Test report Annex A (Normative) Test methods for implantation in subcutaneous tissue Annex B (Normative) Test method for implantation in muscle Annex C (Normative) Test method for implantation in bone Annex D (Normative) Test methods for implantation in brain tissue Annex E (Informative) Examples of evaluation of local biological effects after implantation Bibliography