This review also supports significant future research for developing multi-core and shell-based functional nanosystems to investigate nano-therapies that are needed for advanced, precise, and personalized healthcare systems. A method is disclosed for synthesizing core-shell nanoparticles or microparticles in an aqueous solution. Keeping the scope, demand, and challenges in view, the present review explores state-of-the-art developments and advances in core–shell nanoparticle systems, the desired structure–property relationships, newly generated properties, the effects of parameter control, surface modification, and functionalization, and, last but not least, their promising applications in the fields of drug delivery, biomedical applications, and tissue engineering. In such core/shell nanocrystals, the shell provides a physical barrier between the optically active core and the surrounding medium, thus making the nanocrystals less sensitive to environmental changes, surface chemistry, and photo-oxidation.
Several types of core–shell nanoparticles, such as metallic, magnetic, silica-based, upconversion, and carbon-based core–shell nanoparticles, have been designed and developed for drug delivery applications. Such unique advantages can facilitate the use of core–shell nanoparticles for the selective mingling of two or more different functional properties in a single nanosystem to achieve the desired physicochemical properties that are essential for effective targeted drug delivery. These functional nanoparticles are emerging as a particular class of nanosystems because of their unique advantages, including high surface area, and easy surface modification and functionalization. In this regard, core–shell type nanoparticles are promising nanocarrier systems for controlled and targeted drug delivery applications. However, the controlled and targeted delivery of drugs or genes can be limited due to their physicochemical and functional properties. Nanosystems have shown encouraging outcomes and substantial progress in the areas of drug delivery and biomedical applications.