Fluorescence lateral flow immunoassay based point-of-care nanodiagnostics for orthopedic implant-associated infection

Detection of implant-associated infection at the earliest is necessary to prevent, treat or monitor further complications. In this work, the lateral flow immunoassay (LFIA) based on double antibody sandwich technique is developed using bright fluorescent cadmium telluride quantum dots (CdTe QDs). This point-of-care (POC) nanodiagnostics technique utilizes CdTe QDs for detection of orthopedic implant-associated infection biomarkers such as C-reactive protein (CRP) and interleukin-6 (IL-6). Staphylococcal protein A (SPA) was conjugated with CdTe QDs (SPA-QDs) and antibodies i.e. anti-CRP, anti-IL-6, and anti-rabbit IgG were bound separately on SPA-QDs complex to develop the biosensor mixture. LFIA was developed on the nitrocellulose strip with test and control spot. Color sensor based portable fluorescence strip reader (PorFloR™) was developed and calibrated. The detection range was found to be 1–300 μg/ml and 1-1000 pg/ml for CRP and IL-6, respectively. Limit of detection was found to be 0.3 μg/ml and 0.9 pg/ml for CRP and IL-6, respectively. Developed LFIA was compared with standard ELISA technique and it showed excellent accuracy, sensitivity, reproducibility, and stability. PorFloR™ device provides the quantitative approach to POC nanodiagnostics and has the potential to be utilized for early detection of implant-associated infection and assist surgeons regarding the status of an implanted device.