Current analytical approaches for characterizing nanoparticle sizes in pharmaceutical research

Nanotechnologies exploit a material's 10-9 nanometric scale properties, which differ in physicochemical and biological properties. Various biological mechanisms of the human body activate at the nanometric scale. Nanoparticles (NPs) can traverse via natural obstacles to find new delivery targets and engage with DNA or small proteins at various levels, making NPs useful in pharmaceutical, biomaterial, and diagnostic applications. Producing nanomaterials for specific uses requires controlling synthetic NP's size distribution, shape, surface chemistry, dispersion, aggregation stability, elemental, and nanocrystalline content. NPs are becoming increasingly relevant in fundamental research and applications. The size measurement of NPs still poses a challenge for many researchers and pharmaceutical companies. NPs may frequently be assessed using several techniques, including dynamic light scattering, nanoparticle tracking analysis, tunable resistive pulse sensing, atomic force microscopy, and disc centrifugation, but there are advantages and disadvantages associated with each technique. As per regulatory requirements, the particle size of nanoparticles used in biomedical applications requires an orthogonal approach for characterizations. Therefore, a combinatorial characterization approach is needed to measure the sizes of nanoparticles in pharmaceutical formulations. This review provides a piece of detailed knowledge on recent advancements in analytical techniques with their sample preparations, data interpretations, operational principles, and critical strategies of each technique used for measuring nanoparticle size in various pharmaceutical formulations and vaccine research which will help researchers choose the best appropriate techniques for measuring NP's size.