In recent years, a great deal of research effort has gone into the development of micro- and nano-vectors for controlled release and targeted delivery of active substances. The substrates used to release the active ingredient are often similar in composition to polymers, and therefore sensitive to electron beams.
The release properties of micro/nanoparticles can vary according to their size, shape, surface structure and chemical composition. SEM enables high-resolution analysis of characteristics such as size, morphology and structure of microspheres, helping to optimize their ability to release active ingredients and drug design.
The French National Institute for Research and Safety (INRS) distinguishes between nanoparticles and nanomaterials. A nanoparticle is a particle with three dimensions between 1 and 100 nm. The INRS defines nanomaterials as "a material with at least one external dimension on the nanometric scale, i.e. between 1 and 100 nm, or with an internal or surface structure on the nanometric scale" (definition found in ISO TS 80004-1). The European Commission, for its part, considers a threshold concentration of 50% nanoparticles to define a nanomaterial. For almost ten years, BIOPHY RESEARCH has been a member of the nanoparticle working groups led by LNE. In 2022, the Nanomesure France association, to which BIOPHY RESEARCH belongs, was created with the aim of structuring the nanoparticle industry.
Figure 2 : High-resolution SEM image of drug-releasing PLGA microparticles: large-scale observation (2 x 2 µm2)
The combination of SEM/EDX and ToF-SIMS techniques facilitates comprehensive analysis of the elemental and molecular composition of materials. AFM gives access to the 3D morphology and surface mechanical properties of nanoparticles. X-ray tomography enables non-destructive visualization of internal features such as porosity, cracks and phase distribution. In dynamic mode, it is possible to visualize "in situ" 3D changes in the internal structures of a material when it undergoes modifications such as mechanical deformation, temperature changes or absorption of liquids.