Bismuth Selenide Nanostructured Clusters as Optical Coherence Tomography Contrast Agents: Beyond Gold-Based Particles

Toward Upconversion (Yb-Er) and near-Infrared (Yb-Ho-Er, Nd-Yb) Thermometry with Sea Urchin Type GdPO4 Nanoarchitectures

In recent years, optical temperature probes operating in the second near-infrared (BW-II) and third near-infrared (BW-III) biological windows have garnered significant attention in the scientific community. For biological applications these probes offer distinct advantages, including enhanced tissue penetration depth, minimal autofluorescence, and a remarkable improvement in imaging sensitivity and spatial resolution. Moving toward theranostic applications, there is a growing demand for the development of materials that integrate both BW-II and BW-III thermometry systems with drug delivery functionalities. In this study, we concentrate on the development of GdPO4 materials, utilizing both hard and sacrificial template routes to synthesize (hollow) GdPO4 porous sea urchin-like particles. We first investigated the development of a Boltzmann-type thermometer utilizing an Yb-Er upconversion system, designed to operate within the physiological temperature range. Our exploration extends to the potential of GdPO4 particles in near-infrared (NIR) thermometry, spanning the first, second, and third biological windows with systems like Yb-Ho-Er, Nd-Yb, and Ho-Yb, respectively. We further examined the temperature impact of the Yb-Ho-Er system on the NIR emission within a biologically relevant setting, using a phantom that replicates biological tissue. Furthermore, we illustrate the successful loading of these materials with doxorubicin (DOX·HCl), a model anticancer drug, showing these particles exhibit pH-dependent DOX release. This demonstrates the versatility of these materials as upconversion and NIR thermometers while simultaneously serving as an on-demand drug carrier. The investigation involves assessing their cytotoxicity on specific human cells (Normal Human Dermal Fibroblasts (NHDFs)), to determine their viability for potential use in biological applications. The study also investigates how effectively loading the particles with DOX enables targeted delivery to a cellular model of lymphoma (Jurkat E6-1), resulting in cell death. This comprehensive analysis highlights the promising potential of GdPO4 particles for medical applications.

Ag2 S Biocompatible Ensembles as Dual OCT Contrast Agents and NIR Ocular Imaging Probes

Ag2 S nanoparticles (NPs) emerge as a unique system that simultaneously features in vivo near-infrared (NIR) imaging, remote heating, and low toxicity thermal sensing. In this work, their capabilities are extended into the fields of optical coherence tomography (OCT), as contrast agents, and NIR probes in both ex vivo and in vivo experiments in eyeballs. The new dual property for ocular imaging is obtained by the preparation of Ag2 S NPs ensembles with a biocompatible amphiphilic block copolymer. Rather than a classical ligand exchange, where surface traps may arise due to incomplete replacement of surface sites, the use of this polymer provides a protective extra layer that preserves the photoluminescence properties of the NPs, and the procedure allows for the controlled preparation of submicrometric scattering centers. The resulting NPs ensembles show extraordinary colloidal stability with time and biocompatibility, enhancing the contrast in OCT with simultaneous NIR imaging in the second biological window.