Three-dimensional printing, also known as additive manufacturing, is a fabrication process whereby a 3D object is created layer-by-layer by depositing a feedstock material such as thermoplastic polymer. The 3D printing technology has been widely used for rapid prototyping and its interest as a fabrication method has grown significantly across many disciplines. The most common 3D printing technology is called the Fused Deposition Modelling (FDM) which utilises thermoplastic filaments as a starting material, then extrudes the material in sequential layers above its melting temperature to create a 3D object. These filaments can be fabricated using the Hot-Melt Extrusion (HME) technology. The advantage of using HME to manufacture polymer filaments for FDM printing is that a homogenous solid dispersion of two or more pharmaceutical excipients i.e., polymers can be made and a thermostable drug can even be introduced in the filament composition, which is otherwise impractical with any other techniques. By introducing HME techniques for 3D printing filament development can improve the bioavailability and solubility of drugs as well as sustain the drug release for a prolonged period of time. The latter is of particular interest when medical implants are considered via 3D printing. In recent years, there has been increasing interest in implementing a continuous manufacturing method on pharmaceutical products development and manufacture, in order to ensure high quality and efficacy with less batch-to-batch variations of the pharmaceutical products. The HME and FDM technology can be combined into one integrated continuous processing platform. This article reviews the working principle of Hot Melt Extrusion and Fused Deposition Modelling, and how these two technologies can be combined for the use of advanced pharmaceutical applications.

The bioavailability of drugs is dependent on several factors such as solubility and the administration route. A drug with poor aqueous solubility, therefore, poses challenges with regards to its pharmaceutical advance and ultimately its biological usage. Lipid nanoparticles have been used in pharmaceutical science due to their importance in green chemistry. Their biochemical properties as "green" materials and biochemical processes as "green" processes mean they can be environmentally sustainable. Generally, lipid nanoparticles can be employed as carriers for both lipophilic and hydrophilic drugs. The proposed administration route for nanoparticles can present advantages and disadvantages which should be considered by a formulator. Solid lipid nanoparticles and nanostructured lipid carriers are attractive delivery systems because of their ease of manufacture, biocompatibility, biodegradability and scale-up capacity of formulation constituents. The easy and simple scalability of novel solid lipid nanoparticles and nano lipid carriers, along with their various processing procedures, recent developments, limitation and toxicity, formulation optimization and approaches for the manufacture of lipid nanoparticles, lyophilization and drug release are comprehensively discussed in this review. This review also summarizes the research data related to the various preparation methods and excipients used for solid lipid nanoparticles and nanostructured lipid carriers in recent years.