The grand aim of HOTFLOW was to develop an innovative and sensitive thermal transduction biosensor based on a Lateral Flow ImmunoAssay (LFIA) for the detection and quantification of ultralow concentrations of proteins which could be at once rapid, inexpensive, and versatile.
The selection of the most appropriate high sensitivity point-of-care (PoC) biosensing device for diagnostic applications is critical. According to the World Health Organization diagnostic devices suitable for PoC analysis must be cost-effective, sensitive, specific, user-friendly and capable of providing a rapid real-time result requiring small sample volumes. LFIA is a low-cost, rapid, robust, specific and sensitive technique with limits of detection normally low enough to fulfil the requirements for a wide range of PoC applications, such as the common off-the-shelf hCG pregnancy test. Nonetheless, the sensitivity of LFIA falls short for early diagnosis or detection of some latent diseases where the amounts of analyte are typically low as, for instance, the presence of CEA in human serum for colorectal cancer diagnosis, where the threshold lies between 2.5 and 5 ng/mL in healthy patients. The most popular detection methods for LFIA are colorimetric, fluorescence, electrochemistry and magnetism, among others. But in order to improve the sensitivity of the system the aforementioned approaches usually require special detection devices and/or further technical treatment by trained personnel, all of which calls into question the specific needs of aforementioned PoC applications.
We have adapted the conventional nanoparticle-based LFIA, which uses near infrared (NIR) laser to form a thermoablation spot (a scorched area of nitrocellulose membrane (NC)) observable by the naked eye. The final device would be extremely portable and suitable for rapid multi-detection assays. The use of plasmonic gold nanoparticles as in-built detection agents means that minute amounts of sample and no pre-treatment are required and, furthermore, little or no technical training of the healthcare personnel would be necessary. The principle operational (training) limitation is perhaps the need for a low cost NIR-laser or a light-emitting diode (LED). Our on-going research using combined LFIA and Plasmonic-driven thermal sensing (PTS) technologies is currently focused on developing a suitable immunosensor for commercialised PoC applications in underdeveloped areas or in regions with limited resources.
