Ceramic nanoparticles are primarily made up of oxides, carbides, phosphates and carbonates of metals and metalloids such as calcium, titanium, silicon, etc. They have a wide range of applications due to a number of favourable properties, such as high heat resistance and chemical inertness. Out of all the areas of ceramic nanoparticles applications, biomedical field is the most explored one. In the biomedical field, ceramic nanoparticles are considered to be excellent carriers for drugs, genes, proteins, imaging agents etc. To be able to act as a good and successful drug delivery agent, various characteristics of nanoparticles need to be controlled, such as size range, surface properties, porosity, surface area to volume ratio, etc. In achieving these properties on the favourable side, the method of preparation and a good control over process variables play a key role. Choosing a suitable method to prepare nanoparticles, along with loading of significant amount of drug(s) leads to development of effective drug delivery systems which are being explored to a great extent. Ceramic nanoparticles have been successfully used as drug delivery systems against a number of diseases, such as bacterial infections, glaucoma, etc., and most widely, against cancer. This review gives a detailed account of commonly used methods for synthesising nanoparticles of various ceramic materials, along with an overview of their recent research status in the field of drug delivery.

Microemulsions are isotropic, thermodynamically stable transparent (or translucent) systems of oil, water and surfactant, frequently in combination with a cosurfactant with a droplet size usually in the range of 20-200 nm. They can be classified as oil-in-water (o/w), water-in-oil (w/o) or bicontinuous systems depending on their structure and are characterized by ultra low interfacial tension between oil and water phases. These versatile systems are currently of great technological and scientific interest to the researchers because of their potential to incorporate a wide range of drug molecules (hydrophilic and hydrophobic) due to the presence of both lipophilic and hydrophilic domains. These adaptable delivery systems provide protection against oxidation, enzymatic hydrolysis and improve the solubilization of lipophilic drugs and hence enhance their bioavailability. In addition to oral and intravenous delivery, they are amenable for sustained and targeted delivery through ophthalmic, dental, pulmonary, vaginal and topical routes. Microemulsions are experiencing a very active development as reflected by the numerous publications and patents being granted on these systems. They have been used to improve the oral bioavailability of various poorly soluble drugs including cyclosporine and paclitaxel as professed by Hauer et al., US patent 7235248, and Gao et al., US patent 7115565, respectively. Furthermore, they can be employed for challenging tasks such as carrying chemotherapeutic agents to neoplastic cells and oral delivery of insulin as diligently described by Maranhao, US patent 5578583 and Burnside et al., US patent 5824638 respectively. The recent commercial success of Sandimmune Neoral® (Cyclosporine A), Fortovase® (Saquinavir), Norvir® (Ritonavir), etc. also reflects the tremendous potential of these newer drug therapeutic systems. A critical evaluation of recent patents claiming different approaches to improve the drug delivery is the focus of the current review.