YY/T 1898-2024Intravascular catheters and guidewires - Testing method for coating adhesion (English PDF)

4.2 Visual inspection method

4.2.1 Overview In the case of hydrophilic lubricant coating samples, when wetted, the coating absorbs water and swells into a gel-like state. During use, coatings that are poorly bonded to the catheter or guidewire substrate - or those containing defects in their dry state - may undergo peeling or localized detachment. Consequently, a visual inspection allows for the acquisition of information regarding the coating's morphology and defects, thereby enabling a preliminary assessment of its adhesion strength.

4.2.2 Test method After pretreatment, the sample shall be inspected for defects such as damage or detachment of the coating. This inspection may be performed directly or, by reference to Annex A, after staining. Pre-treatment methods include soaking, friction testing, and the selection of appropriate vascular models to simulate clinical use. One or more of these sample treatment methods may be selected based on clinical application and experimental objectives.

4.3 Friction testing method

4.3.1 Overview If the friction force or friction coefficient increases significantly as the number of friction cycles rises, it suggests that the coating may be undergoing detachment. To a certain extent, this reflects the adhesion strength of the coating.

4.3.2 Test model Annex B presents the test model. A constant normal clamping force is applied, and under specified test conditions, a silicone sheet is rubbed repeatedly against the surface of the test specimen. The number of repetitions shall be determined with statistical significance in mind; a minimum of 10 repetitions is recommended. This parameter may also be adjusted as appropriate based on the intended clinical use of the product. The number of repeated friction cycles is recorded. A curve plotting friction force versus friction coefficient is generated, and changes in friction force and friction coefficient are monitored in real time. NOTE

1.For the purposes of this document, normal clamping force refers to the force exerted by the silicone sheet perpendicular to the contact surface between the catheter and the guidewire. NOTE 2.A single friction cycle refers to the process in which a silicone sheet applies a constant normal force to clamp the sample at a starting position, slides a specified distance, and then releases the sample to return to the starting position.

4.4 Particulate testing method

4.4.1 Overview During use, intravascular catheters and guidewires frequently encounter friction against blood vessels or associated devices. This process may result in the shedding of the device's coating. This shedding manifests as the presence of particulates - or even finer residues - within the test solution. The greater the adhesion strength of the coating, the fewer particulates or residues shall be generated. Therefore, by subjecting the device to an immersion treatment - tailored to its specific clinical application and the objectives of the test - or by simulating clinical usage within an appropriate vascular model (see Annex C), a test solution containing the shed particulates can be obtained. By employing particulate counting methods to quantify the size and number of particulates within this test solution, the adhesion strength of the coating can be assessed to a significant degree.

4.4.2 Selection of vascular models and samples An appropriate vascular model from Annex C shall be selected based on the intended clinical use of the device.

4.4.3 Preparation of test solution Depending on the site of vascular access and the complexity involved during the clinical use of the product, select either the immersion method or the vascular model friction method. Prepare the test solution in accordance with Annex D and Annex E.

4.4.4 Particle counting Count the test solution in accordance with the method specified in General Chapter 0903, "Particulate matter in injections" of the "Pharmacopoeia of the People's Republic of China (Edition 2020, Vol. IV)", or the method specified in YY/T 1556. NOTE. Alternatively, use other validated methods to perform particulate counting on the test solution.

4.5 Chemical property testing method If detached components dissolve or form sub-micron or nano-scale particles that cannot be detected via particulate counting, the test solution may be prepared in accordance with Annex F, based on the product's clinical application and the objectives of the study. Appropriate chemical characterization methods (such as tests for reducing substances, evaporation residue, UV absorbance, or other specific analytical techniques) may be selected, so as to assess the detachment of the coating.