P88: In vitro Nasopharyngeal Cavity Model for Comparative Performance Evaluation Between New Nasopharyngeal and Commercial Swabs in Viral Detection

Background: During SARS-CoV-2 pandemic, one of the challenges during the planning and execution of control strategies was the global shortage of supplies and personal protection elements (PPEs). For instance, nasopharyngeal swabs for the collection of mucosal samples were one of the scarcest. In Colombia, the limited capacity for characterization, evaluation, validation and the absence of clear regulatory pathways was a major obstacle for manufacturers. The aim of this study is to design, manufacture a bench testing platform as a nasal cavity to evaluate the performance of locally produced nasopharyngeal swabs for mucosal sample collection. Methods: Experimental nasopharyngeal swabs were designed and manufactured via a one-step injection in collaboration with Plastinovo S.A.S. (Bogota, COL). Commercial nasopharyngeal swabs were acquired from Nodford International Co., Ltd and HanChang Medic Co., Ltd. A 3D digital reconstruction of the nasopharyngeal cavity was generated from computed tomography images of an adult patient. An anatomical model of the soft tissues was 3D printed, using a flexible translucent polymeric material (Agilus30, Stratasys) while a rigid white material (VeroWhite, Stratasys) was employed for the bone. A mucous substitute made from egg albumin was loaded with a RNA based vaccine (Stamaril) and placed on the internal cavity of the 3D model. Swabs were introduced into the nasopharyngeal cavity to simulate the conventional sampling process and the sample was transferred to a viral transport medium for RNA extraction followed by RT-qPCR for viral RNA detection. Locally manufactured swabs were tested against commercial counterparts. Results: The 3D printed nasopharyngeal model accurately replicated the anatomy of cavities and the mechanical properties of soft and hard tissue structures. The collection of viral samples proceeded successfully with the mucosal substitute. The substitute exhibited appropriate viscoelastic properties and do not interfere with RT-qPCR. The released/collected sample percentage of injection and commercial swabs was 77.06±5.14% and 63.74±6.28%, respectively. The Plastinovo swabs provide a detection limit and viral load comparable to commercial swabs as demonstrating by Ct values close to the positive control of the vaccine alone (16.51). Conclusion: Nasopharyngeal cavity allows for the bench testing of nasopharyngeal swabs and could be tough for other medical devices. On the other hand, swabs developed by Plastinovo were validated and showed to be suitable for large-scale local production. The next steps will focus on devising the routes to complying with the regulatory schemes for local and international commercialization of nasopharyngeal swabs.