Low-Cost 3D Printers Enable High-Quality and Automated Sample Preparation and Molecular Detection

Most molecular diagnostic assays require upfront sample preparation steps to isolate the target’s nucleic acids, followed by its amplification and detection using various nucleic acid amplification techniques. Because molecular diagnostic methods are generally rather difficult to perform manually without highly trained users, automated and integrated systems are highly desirable but too costly for use at point-of-care or low-resource settings. Here, we showcase the development of a low-cost and rapid nucleic acid isolation and amplification platform by modifying entry-level 3D printers that cost between $400 and $750. Our modifications consisted of replacing the extruder with a tip-comb attachment that houses magnets to conduct magnetic particle-based nucleic acid extraction. We then programmed the 3D printer to conduct motions that can perform high-quality extraction protocols. Up to 12 samples can be processed simultaneously in under 13 minutes and the efficiency of nucleic acid isolation matches well against gold-standard spin-column-based extraction technology. Additionally, we used the 3D printer’s heated bed to supply heat to perform water bath-based polymerase chain reactions (PCRs). Using another attachment to hold PCR tubes, the 3D printer was programmed to automate the process of shuttling PCR tubes between water baths. By eliminating the temperature ramping needed in most commercial thermal cyclers, the run time of a 35-cycle PCR protocol was shortened by 33%. This article demonstrates that for applications in resource-limited settings, expensive nucleic acid extraction devices and thermal cyclers that are used in many central laboratories can be potentially replaced by a device modified from inexpensive entry-level 3D printers.

绝大多数分子诊断检测（molecular diagnostic assays）均需先完成前置样本制备步骤以分离靶标核酸，随后通过各类核酸扩增技术完成靶标的扩增与检测。由于分子诊断方法通常操作门槛较高，未经专业培训的人员难以手动完成，因此自动化集成系统极具应用价值，但在即时检验（point-of-care）或资源匮乏场景中成本过高。
本研究展示了一款低成本快速核酸分离与扩增平台的开发方案，通过改造售价400至750美元的入门级3D打印机实现。改造方案为将打印机的挤出头替换为搭载磁体的梳状吸头组件，用于开展基于磁珠的核酸提取（magnetic particle-based nucleic acid extraction）；随后对3D打印机进行编程，使其可执行符合高质量标准的提取流程。该平台可在13分钟内同时处理最多12个样本，核酸分离效率与金标准离心柱式提取技术（spin-column-based extraction technology）相当。
此外，本研究利用3D打印机的加热床提供热源，实现水浴式聚合酶链式反应（PCR，polymerase chain reactions）。通过加装另一组用于固定PCR管的组件，可对3D打印机编程以实现PCR管在水浴间的自动转移。相较于多数商用热循环仪（thermal cyclers）需要的温度升降环节，35轮循环的PCR流程运行时间缩短了33%。
本研究证实，针对资源受限场景的应用需求，许多中心实验室使用的昂贵核酸提取设备与热循环仪，均可通过改造廉价入门级3D打印机实现替代。