Rebeca Muniz de Melo

The therapeutic use of silver nanoparticles (AgNPs) has been increasing, especially in phototherapy strategies. The plasmonic properties of AgNPs have contributed to their excellent results as phototherapeutic agents, namely for photodynamic therapy (PDT), photothermal therapy (PTT), and photodynamic inactivation of microorganisms. Moreover, the capacity of these nanostructures to release silver ions (Ag⁺) and enhance the production of reactive oxygen species (ROS) has been explored in combination with light to treat several diseases. Moreover, synthesis, functionalization, and conjugation strategies with targeting agents have been widely studied to optimize selectivity and maximize the therapeutic efficacy of these nanoplatforms. In this work, we reviewed the recent advancements (2019–2024) in the use of AgNPs for phototherapy applications, with an emphasis on evaluating therapeutic efficacy and specific targeting. According to the literature, in oncology, AgNPs have been predominately employed in PTT-based strategies, demonstrating significant tumor cell death and preservation of healthy tissues, in both in vitro and in vivo studies. Concurrently, AgNP-mediated PDT has emerged as a promising approach for the eradication of bacteria and fungi, particularly those commonly associated with antibiotic resistance. The compiled data indicate that AgNPs represent an innovative and effective therapeutic alternative, with a strong potential for clinical translation, in both cancer treatment and the management of hard-to-treat infections.

The development of bimodal systems with signals for two diagnostic techniques has been increasing. Magnetic resonance imaging (MRI) is a non-invasive technique that distinguishes pathological tissues from healthy ones. To improve the images’ contrast, nanoparticulate contrast agents (CAs) have been developed, allowing for the attachment of several CA molecules in one nanoparticle. In this work, we associated AgInSe₂ quantum dots (QDs) with gadolinium complexes, obtaining nanoprobes for MRI and optical imaging. The nanosystems showed good optical properties and values of relaxivity superior to the CAs used clinically. Thus, these nanoprobes have the potential to be used as CAs for MRI and optical imaging.

Currently, there is a growing interest in the development of bimodal systems that have a signal for more than one diagnostic imaging technique, such as magnetic resonance imaging (MRI). MRI is able to distinguish pathological from healthy tissues; however, in some cases, a high local concentration of contrast agents (CAs) is necessary to improve the contrast in images. Nanoparticulate CAs are able to concentrate several CA molecules into one nanoparticle, increasing the local concentrations of paramagnetic ions. In this work, we intend to associate AgInSe₂ quantum dots (QDs) with gadolinium complexes (DOTA-Gd) to develop bimodal systems. The QDs were prepared in water and the synthesis parameters were optimized. The ligand DOTA was conjugated with cysteamine and complexed with Gd³⁺. The complex was then conjugated to QDs through the metal–thiol bond, obtaining the bimodal systems. Optical characterization indicated that the QDs remained stable and fluorescent, and an increase in emission intensity after conjugation was observed. The systems were characterized by relaxometry at 20 MHz (0.47 T) and 37 °C, obtaining longitudinal relaxivities by Gd³⁺ higher than the CAs used clinically. Thus, the prepared nanoprobes showed promising properties for MRI and optical imaging.