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.

Background/Objectives: Bone infection remains a severe clinical challenge characterized by recurrence, antimicrobial resistance, and high morbidity, driving the search for new therapeutic strategies. Despite advances in developing biomaterials with suitable biocompatibility, biodegradability, and structural properties, the lack of effective antibacterial activity continues to significantly limit the treatment of bone defects. To overcome this issue, we investigated the incorporation of silver-based nanostructures into calcium polyphosphate/alginate (CPP/Alg) matrices as an antibacterial reinforcement strategy for bone-related applications. Methods: Silver nanoparticles (AgNPs) were synthesized in aqueous medium via NaBH₄-mediated chemical reduction, using either alginate (Alg) or sodium polyphosphate (PP) as stabilizing agents, enabling a comparative evaluation of biocompatible polymer- and polyphosphate-stabilized systems. Subsequently, AgNPs were incorporated into calcium polyphosphate/alginate (CPP/Alg) matrices to obtain Ag-containing composites. Results: The AgNPs exhibited spherical morphology, Zeta potential values ranging from −38.7 ± 0.2 to −23 ± 0.3 mV, and hydrodynamic diameters between 25.2 ± 0.2 and 143 ± 5 nm. Structural characterization of the biocomposites by X-ray diffraction confirmed hydroxyapatite as the major crystalline phase, while Raman spectroscopy revealed vibrational bands corresponding to both the inorganic and polymeric components. SEM revealed a dense, rough surface, and ICP-OES analysis confirmed the presence of Ag. Antibacterial activity assays demonstrated effective growth inhibition of Staphylococcus aureus and Staphylococcus epidermidis, with inhibition halos growing with increasing composite dosage. Notably, antibacterial activity was achieved at relatively low Ag contents, underscoring the efficiency of these biocomposites. Conclusions: These findings confirm the effective incorporation of AgNPs into the CPP/Alg matrix and support the classification of composites as promising antibacterial biomaterials for bone regeneration applications.

Polyphosphate (PP) is an inorganic polymer formed by the condensation of orthophosphate groups and represented by the formula [PO³⁻]_n. Due to its properties, such as biocompatibility and low toxicity, polyphosphate presents itself as a biomimetic compound of hydroxyapatite, the main constituent of bone tissue. PP can be applied for bone tissue applications as a ceramic material in the form of calcium polyphosphate (CPP), due to its chemical similarity with hydroxyapatite. Thus, CPP has been used to develop scaffolds for bone tissue repair. However, CPP does not have adequate mechanical properties for application in bone, requiring the use of substances that add other properties to the material, such as resistance to compression and tension. For this, polymers, ions, and nanoparticles have been used as additives. In this context, this work presents the development of composite materials based on CPP, PVA, and Mg²⁺ as candidates for bone applications. The production of materials was based on the precipitation of CPP in an aqueous medium containing a pre-solubilized polymer, followed by the addition of Mg²⁺. The materials were characterized by TGA, SEM, EDS, and Raman. The results confirmed the formation of the composites, presenting a porous structure and containing a Ca/P ratio of 0.90. Thus, these composites have the potential to be applied in bone regeneration applications.