Smart assembly of Mn-ferrites/silica core-shell with fluorescein and gold nanorods: robust and stable nanomicelles for in vivo triple modality imaging

Gold-Based Nanostructures for Antibacterial Application

Bacterial infections have become a fatal threat because of the abuse of antibiotics in the world. Various gold (Au)-based nanostructures have been extensively explored as antibacterial agents to combat bacterial infections based on their remarkable chemical and physical characteristics. Many Au-based nanostructures have been designed and their antibacterial activities and mechanisms have been further examined and demonstrated. In this review, we collected and summarized current developments of antibacterial agents of Au-based nanostructures, including Au nanoparticles (AuNPs), Au nanoclusters (AuNCs), Au nanorods (AuNRs), Au nanobipyramids (AuNBPs), and Au nanostars (AuNSs) according to their shapes, sizes, and surface modifications. The rational designs and antibacterial mechanisms of these Au-based nanostructures are further discussed. With the developments of Au-based nanostructures as novel antibacterial agents, we also provide perspectives, challenges, and opportunities for future practical clinical applications.

Biological Applications of Silica-Based Nanoparticles

Silica nanoparticles have been widely explored in biomedical applications, mainly related to drug delivery and cancer treatment. These nanoparticles have excellent properties, high biocompatibility, chemical and thermal stability, and ease of functionalization. Moreover, silica is used to coat magnetic nanoparticles protecting against acid leaching and aggregation as well as increasing cytocompatibility. This review reports the recent advances of silica-based magnetic nanoparticles focusing on drug delivery, drug target systems, and their use in magnetohyperthermia and magnetic resonance imaging. Notwithstanding, the application in other biomedical fields is also reported and discussed. Finally, this work provides an overview of the challenges and perspectives related to the use of silica-based magnetic nanoparticles in the biomedical field.

An Application of Multivariate Data Analysis to Photoacoustic Imaging for the Spectral Unmixing of Gold Nanorods in Biological Tissues

Gold nanorods (GNRs) showed to be a suitable contrast agent in photoacoustics (PA), and are able to provide a tunable absorption contrast against background tissue, while a detectable PA signal can be generated from highly localized and targeted areas. A crucial issue for these imaging techniques is represented by the discrimination between exogenous and endogenous contrast and the assessment of the real PA signal magnitude. The application of image resolution/unmixing methods was implemented and optimized to recover the relative magnitude spectra and distribution maps of image constituents of the biological sample based on multivariate analysis (multivariate curve resolution-alternating least squares, MCR-ALS) in the presence of GNRs with tunable absorption properties. The proposed data analysis methodology is demonstrated on real PA images from experimental animal models and ex-vivo preparations.

Current concepts in nanostructured contrast media development for in vivo photoacoustic imaging

To overcome the endogenous photoacoustic contrast arising from endogenous species, specific contrast agents need to be developed, allowing PAI to successfully identify targeted contrast in the range of wavelength in which the interference from the biomatrix is minimized.

Impact of metallic trace elements on relaxivities of iron-oxide contrast agents

In this work, well-defined 3 nm-sized Ca²⁺, Fe³⁺, Na⁺, Mg²⁺, Zn²⁺, Ni²⁺, Co²⁺, and Cd²⁺ cation-adsorbed Fe₃O₄/γ-Fe₂O₃ nanoparticles were used as prototype systems to investigate the influence of metallic trace elements in body fluids on the relaxivities of iron-oxide contrast agents. It was found that surface-adsorbed cations formed a deterioration layer to induce pronounced relaxivity loss. Theoretical study showed that such relaxivity loss can be well described by a modified GCAS function, taking into account the harmonic cation oscillations around Fe₃O₄/γ-Fe₂O₃ nanoparticles. Quantum mechanics analyses revealed that even-parity and odd-parity states of harmonic oscillations are dominant in r₁ and r₂ relaxivities, respectively. Moreover, the harmonic oscillations of Na⁺ and Mg²⁺ cations around Fe₃O₄/γ-Fe₂O₃ nanoparticles are found to be classical forbidden, which are quite different from their counterparts located in the classical permissive area.

Distribution of relaxivity loss can be well described by a modified GCAS function.