Advanced Static and Dynamic Fluorescence Microscopy Techniques to Investigate Drug Delivery Systems

Abstract

In the past decade(s), fluorescence microscopy and laser scanning confocal microscopy (LSCM) have been widely employed to investigate biological and biomimetic systems for pharmaceutical applications, to determine the localization of drugs in tissues or entire organisms or the extent of their cellular uptake (in vitro). However, the diffraction limit of light, which limits the resolution to hundreds of nanometers, has for long time restricted the extent and quality of information and insight achievable through these techniques. The advent of super-resolution microscopic techniques, recognized with the 2014 Nobel prize in Chemistry, revolutionized the field thanks to the possibility to achieve nanometric resolution, i.e., the typical scale length of chemical and biological phenomena. Since then, fluorescence microscopy-related techniques have acquired renewed interest for the scientific community, both from the perspective of instrument/techniques development and from the perspective of the advanced scientific applications. In this contribution we will review the application of these techniques to the field of drug delivery, discussing how the latest advancements of static and dynamic methodologies have tremendously expanded the experimental opportunities for the characterization of drug delivery systems and for the understanding of their behaviour in biologically relevant environments.

Fluorescence Recovery after Photobleaching in Colloidal Science: Introduction and Application

“…Diffusion characteristics of diverse materials are critical for nonbiological as well as biological applications, such as drug delivery, cell culture, and tissue engineering. − The behavior of material components determines material stability and mechanical characteristics; similarly, diffusion of active chemicals in the bulk material determines their presentation or release. In 1827, Robert Brown observed the free migration of plant organelles expelled from pollen grains into a surrounding aqueous solution.…”

Assessing the interactions between nanoparticles and biological barriers in vitro: a new challenge for microscopy techniques in nanomedicine

“…Among the different fluorescent-related microscopy techniques, laser scanning confocal microscopy (LSCM) is extensively applied because, compared to the conventional epifluorescence microscopy, it provides an increase in the effective signal-to-noise ratio and allows visualizing the 3D distribution of NPs by the collection of serial optical sections from the entire sample thickness. 19 Numerous works have exploited the potential of LSCM to detect the uptake, diffusion and localization of several kind of NPs through different biological barriers (blood vessel, skin, intestine, mucus, tumor) simulated in vitro under static or dynamic conditions. [20][21][22][23][24][25][26][27][28][29][30][31][32][33] George and collaborators investigated the translocation of silica NPs in a transwell model of the human bronchial epithelial barrier, obtaining also quantitative information on the NP distribution in the apical and basolateral compartments.…”

Structural Characterization Study of a Lipid Nanocapsule Formulation Intended for Drug Delivery Applications Using Small-Angle Scattering Techniques

“… 17 However, many novel drug delivery systems that have showed potential for treating various diseases remain poorly characterized at the nanoscale, and how the drug interacts with the drug delivery systems is still unknown in many cases. 18 , 19 Structural elucidation will thus offer possibilities for a better formulation optimization to suit the desired applications.…”

“…As a result, morphologically they look like ellipsoidal vesicles compared to spherical structures when they have no drug. , This nanoprecipitation ultimately results in increased drug loading and a prolonged drug release . However, many novel drug delivery systems that have showed potential for treating various diseases remain poorly characterized at the nanoscale, and how the drug interacts with the drug delivery systems is still unknown in many cases. , Structural elucidation will thus offer possibilities for a better formulation optimization to suit the desired applications.…”