Multiplexed Plasmonic Nano-Labeling for Bioimaging of Cytological Stained Samples

Coiled-Coil-Based Biofunctionalization of 100 nm Gold Nanoparticles with the Trastuzumab Antibody for the Detection of HER2-Positive Cancer Cells

We compared different biofunctionalization strategies for immobilizing trastuzumab, an IgG targeting the HER2 biomarker, onto 100 nm spherical gold nanoparticles because of the E/K coiled-coil peptide heterodimer. First, Kcoil peptides were grafted onto the gold surface while their Ecoil partners were genetically encoded at the C-terminus of trastuzumab's Fc region, allowing for a strong and specific interaction between the antibodies and the nanoparticles. Gold nanoparticles with no Kcoil peptides on their surface were also produced to immobilize Ecoil-tagged trastuzumab antibodies via the specific adsorption of their negatively charged Ecoil tags on the positively charged gold surface. Finally, the nonspecific adsorption of wild-type trastuzumab on the gold surface was also assessed, with and without Kcoil peptides grafted on it beforehand. We developed a thorough workflow to systematically compare the immobilization strategies regarding the stability of nanoparticles, antibody coverage, and ability to specifically bind to HER2-positive breast cancer cells. All nanoparticles were highly monodisperse and retained their localized surface plasmon resonance properties after biofunctionalization. A significant increase in the amount of immobilized antibodies was observed with the two oriented coil-based strategies compared to nonspecific adsorption. Finally, all biofunctionalization strategies allowed for the detection of HER2-positive breast cancer cells, but among the investigated approaches, we recommend using the E/K coiled-coil-based strategy for gold nanoparticle biofunctionalization because it allows for the qualitative and quantitative detection of HER2-positive cells with a higher contrast compared to HER2-negative cells.

Dynamic multispectral detection of bacteria with nanoplasmonic markers

Culture-based diagnosis of bacterial diseases is a time-consuming technique that can lead not only to antibiotic resistance or bacterial mutation but also to fast-spreading diseases. Such mutations contribute to the fast deterioration of the patient's health and in some cases the death depending on the complexity of the infection. There is great interest in developing widely available molecular-level diagnostics that provide accurate and rapid diagnosis at the individual level and that do not require sophisticated analysis or expensive equipment. Here, we present a promising analytical approach to detect the presence of pathogenic bacteria based on their dynamic properties enhanced with nanoplasmonic biomarkers. These markers have shown greater photostability and biocompatibility compared to fluorescent markers and quantum dots, and serve as both a selective marker and an amplifying agent in optical biomedical detection. We show that a simple dark-field side- illumination technique can provide sufficiently high-contrast dynamic images of individual plasmonic nanoparticles attached to Escherichia coli (E. coli) for multiplex biodetection. Combined with numerical dynamic filtering, our proposed system shows great potential for the deployment of portable commercial devices for rapid diagnostic tests available to physicians in emergency departments, clinics and public hospitals as point-of-care devices.

Recent Developments in Plasmonic Alloy Nanoparticles: Synthesis, Modelling, Properties and Applications

Despite the traditional plasmonic materials are counted on one hand, there are a lot of possible combinations leading to alloys with other elements of the periodic table, in particular those renowned for magnetic or catalytic properties. It is not a surprise, therefore, that nanoalloys are considered for their ability to open new perspectives in the panorama of plasmonics, representing a leading research sector nowadays. This is demonstrated by a long list of studies describing multiple applications of nanoalloys in photonics, photocatalysis, sensing and magneto-optics, where plasmons are combined with other physical and chemical phenomena. In some remarkable cases, the amplification of the conventional properties and even new effects emerged. However, this field is still in its infancy and several challenges must be overcome, starting with the synthesis (control of composition, crystalline order, size, processability, achievement of metastable phases and disordered compounds) as well as the modelling of the structure and properties (accuracy of results, reliability of structural predictions, description of disordered phases, evolution over time) of nanoalloys. To foster the research on plasmonic nanoalloys, here we provide an overview of the most recent results and developments in the field, organized according to synthetic strategies, modelling approaches, dominant properties and reported applications. Considering the several plasmonic nanoalloys under development as well as the large number of those still awaiting synthesis, modelling, properties assessment and technological exploitation, we expect a great impact on the forthcoming solutions for sustainability, ultrasensitive and accurate detection, information processing and many other fields.