Ultrabright Föster Resonance Energy Transfer Nanovesicles: The Role of Dye Diffusion

Nanotherapeutic Heterogeneity: Sources, Effects, and Solutions

Nanomaterials have revolutionized medicine by enabling control over drugs' pharmacokinetics, biodistribution, and biocompatibility. However, most nanotherapeutic batches are highly heterogeneous, meaning they comprise nanoparticles that vary in size, shape, charge, composition, and ligand functionalization. Similarly, individual nanotherapeutics often have heterogeneously distributed components, ligands, and charges. This review discusses nanotherapeutic heterogeneity's sources and effects on experimental readouts and therapeutic efficacy. Among other topics, it demonstrates that heterogeneity exists in nearly all nanotherapeutic types, examines how nanotherapeutic heterogeneity arises, and discusses how heterogeneity impacts nanomaterials' in vitro and in vivo behavior. How nanotherapeutic heterogeneity skews experimental readouts and complicates their optimization and clinical translation is also shown. Lastly, strategies for limiting nanotherapeutic heterogeneity are reviewed and recommendations for developing more reproducible and effective nanotherapeutics provided.

Amphiphilic Fluorinated Unimer Micelles as Nanocarriers of Fluorescent Probes for Bioimaging

The unique self-assembly properties of unimer micelles are exploited for the preparation of fluorescent nanocarriers embedding hydrophobic fluorophores. Unimer micelles are constituted by a (meth)acrylate copolymer with oligoethyleneglycol and perflurohexylethyl side chains (PEGMA90-co-FA10) in which the hydrophilic and hydrophobic comonomers are statistically distributed along the polymeric backbone. Thanks to hydrophobic interactions in water, the amphiphilic copolymer forms small nanoparticles (<10 nm), with tunable properties and functionality. An easy procedure for the encapsulation of a small hydrophobic molecule (C153 fluorophore) within unimer micelles is presented. UV-vis, fluorescence, and fluorescence anisotropy spectroscopic experimental data demonstrate that the fluorophore is effectively embedded in the nanocarriers. Moreover, the nanocarrier positively contributes to preserve the good emissive properties of the fluorophore in water. The efficacy of the dye-loaded nanocarrier as a fluorescent probe is tested in two-photon imaging of thick ex vivo porcine scleral tissue.

Aggregates of Cyanine Dyes: When Molecular Vibrations and Electrostatic Screening Make the Difference

Aggregates of cyanine dyes are currently investigated as promising materials for advanced electronic and photonic applications. The spectral properties of aggregates of cyanine dyes can be tuned by altering the supramolecular packing, which is affected by the length of the dye, the presence of alkyl chains, or the nature of the counterions. In this work, we present a joint experimental and theoretical study of a family of cyanine dyes forming aggregates of different types according to the length of the polymethinic chain. Linear and nonlinear optical spectra of aggregates are rationalized here in terms of an essential-state model accounting for intermolecular interactions together with the molecular polarizability and vibronic coupling. A strategy is implemented to properly account for screening effects, distinguishing between electrostatic intermolecular interactions relevant to the ground state (mean-field effect) and the interactions relevant to the excited states (excitonic effects). To the best of our knowledge, this is the first attempt to simulate nonlinear spectral properties of aggregates of symmetric dyes accounting for molecular vibrations.

Quatsomes Loaded with Squaraine Dye as an Effective Photosensitizer for Photodynamic Therapy

Photodynamic therapy is a non-invasive therapeutic strategy that combines external light with a photosensitizer (PS) to destroy abnormal cells. Despite the great progress in the development of new photosensitizers with improved efficacy, the PS’s photosensitivity, high hydrophobicity, and tumor target avidity still represent the main challenges. Herein, newly synthesized brominated squaraine, exhibiting intense absorption in the red/near-infrared region, has been successfully incorporated into Quatsome (QS) nanovesicles at different loadings. The formulations under study have been characterized and interrogated in vitro for cytotoxicity, cellular uptake, and PDT efficiency in a breast cancer cell line. The nanoencapsulation of brominated squaraine into QS overcomes the non-water solubility limitation of the brominated squaraine without compromising its ability to generate ROS rapidly. In addition, PDT effectiveness is maximized due to the highly localized PS loadings in the QS. This strategy allows using a therapeutic squaraine concentration that is 100 times lower than the concentration of free squaraine usually employed in PDT. Taken together, our results reveal the benefits of the incorporation of brominated squaraine into QS to optimize their photoactive properties and support their applicability as photosensitizer agents for PDT.

Fluorescent Multifunctional Organic Nanoparticles for Drug Delivery and Bioimaging: A Tutorial Review

Fluorescent organic nanoparticles (FONs) are a large family of nanostructures constituted by organic components that emit light in different spectral regions upon excitation, due to the presence of organic fluorophores. FONs are of great interest for numerous biological and medical applications, due to their high tunability in terms of composition, morphology, surface functionalization, and optical properties. Multifunctional FONs combine several functionalities in a single nanostructure (emission of light, carriers for drug-delivery, functionalization with targeting ligands, etc.), opening the possibility of using the same nanoparticle for diagnosis and therapy. The preparation, characterization, and application of these multifunctional FONs require a multidisciplinary approach. In this review, we present FONs following a tutorial approach, with the aim of providing a general overview of the different aspects of the design, preparation, and characterization of FONs. The review encompasses the most common FONs developed to date, the description of the most important features of fluorophores that determine the optical properties of FONs, an overview of the preparation methods and of the optical characterization techniques, and the description of the theoretical approaches that are currently adopted for modeling FONs. The last part of the review is devoted to a non-exhaustive selection of some recent biomedical applications of FONs.