Nano-colorimetric sensing coupled with a smartphone platform for highly sensitive detection of MDA-MB-231 cells

Triple-negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer (BC), and the precise detection of MDA-MB-231 cells is important for the early diagnosis, disease monitoring, and evaluation of treatment efficacy in TNBC. However, traditional detection methods have disadvantages such as complex procedures, high costs, and poor portability, and they fail to meet the need for rapid, accurate, low-cost, on-site detection of cancer cells. To address these challenges, we developed a rapid, highly sensitive colorimetric sensing system, which was subsequently applied to detect MDA-MB-231 cells. We first synthesized polydopamine nanoparticles via the conventional oxidative self-assembly method and then immobilized thymolphthalein onto the nanoparticles, achieving a high loading capacity of 283 mg g^-1 and improved detection sensitivity. We further grafted folate onto the nanoparticles for targeted recognition of MDA-MB-231 cells, as it specifically binds to folate receptors on the cell surface. We detected MDA-MB-231 cells by integrating visual identification with quantitative UV-vis absorption spectroscopy, achieving a detection limit as low as 25 cells per mL and a detection time of only 120 s. Furthermore, we integrated the sensing system with a smartphone-based detection platform, enabling highly sensitive and portable detection of MDA-MB-231 cells. Taken together, the developed system exhibits considerable advantages, including simplicity, high sensitivity, low cost, and portability. It provides new technical support for the early screening, disease monitoring, and on-site diagnosis of BC. The smartphone-assisted detection strategy also offers a novel research direction for its application in resource-limited and remote regions.