We investigated the creation of SERS-active hierarchical substrates based on self-assembled nanospheres (HSNs). We demonstrate how the “hierarchical” approach could be systematically exploited to extend the SERS hotspots into the third dimension, by enhancing the hot-spots spatial density and intensity. The proposed hierarchical substrates take advantage of the single layer hexagonal closed packed array nanospheres (CPA). An additional layer of upper nanospheres to obtain dense and intense hot spots pattern is employed. To predict the SERS performance and to identify the promising architectures, a numerical analysis is carried out, offering design criteria, an overview of the operating mechanisms and conditions that affect the SERS behavior of substrates. We fabricated HSNs by using a self-assembling approach and the preliminary results reported. The results highlight that HSNs can be used as cost-effective SERS substrates with better performance than simpler single-layer CPA configurations.
The ability to make an accurate diagnosis at the time of treatment is crucial for many diseases. However, current standard diagnostic procedures can only be performed in specialised healthcare facilities. To bring diagnostic methods from a specialised laboratory to the point of treatment, many alternative methods have been proposed. One of them is surfaceenhanced Raman scattering (SERS), which offers advantageous features such as high sensitivity in biotarget detection and higher accuracy. Here, we have developed an advanced SERS platform for the ultrasensitive, rapid and highly specific identification of tumour biomarkers in liquid biopsies. Our particular focus is on the detection of Thyroglobulin (Tg), the most important tumour biomarker for the diagnosis and prognosis of thyroid cancer. Specifically, SERS-active substrates fabricated by nanosphere lithography on chip or on tips of optical fiber (OF) were functionalized with Tg Capture antibodies. Gold nanoparticles were functionalized with Detection antibodies and conjugated with a Raman reporter. The sandwich assay platform was validated in the planar configuration and a detection limit of only 7 pg/ml was successfully achieved. The same approach has been successfully demonstrated on washout fluids from fine needle aspiration biopsies of cancer patients. Finally, the functionalization strategy was translated to the LOF-SERS platform and successfully used to detect Tg concentration. The proposed SERS-assisted immunoassay platform has proven to be highly versatile and can be used with both microfluidic chip POC devices and SERS-OF-based optrodes to perform sensitive, specific and rapid ex vivo assays for Tg detection in liquid intraoperative biopsies.
Lab-on-Fiber (LoF) technology is a research field aimed at transforming a simple optical fiber into a multifunctional probe, which exploits enhanced light-matter interaction for a variety of applications, with special aptitude for biosensing. An attractive thread in this scenario is the integration of plasmonic metasurfaces onto an optical fiber tip, known as optical fiber “meta-tips”, leading to the development of a new generation of highly sensitive optrodes. Here we report on the latest achievements concerning the investigation of LoF probes assisted by plasmonic phase-gradient metasurfaces for the detection of small molecules as well as clinically relevant cancer biomarkers in the picomolar range. The high biosensing performance, joined with huge potential for miniaturization and integration, makes this platform an excellent candidate for the development of Point-of-Care (PoC) devices aimed at real-time and label-free detection of clinically relevant biomarkers offering several advantages over conventional procedures.
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