Different types of cationic clay minerals and their applications in various biological systems.

Natural compounds are emerging as effective agents for the treatment of malignant diseases. Curcumin (diferuloylmethane), the active constituent of turmeric extract, has gained significant interest as a plant-based compound with anti-cancer properties. Curcumin is physiologically very well tolerated, with negligible systemic toxicity observed even after high oral doses administration. Despite curcumin's superior properties as an anti-cancer agent its applications are limited due to its low solubility and physico-chemical stability, rapid systemic clearance and low cellular uptake. This review focuses on the development of curcumin nano-particle formulation to improve its therapeutic index through enhanced cellular uptake, localization to targeted areas and improved bioavailability. The feasibility of nano-formulation in delivering curcumin and the limitations and challenges in designing and administrating the nano-sized curcumin particles are also covered in this review. Nanotechnology is a promising tool to enhance efficacy and delivery of drugs. In this context, formulation of curcumin as nano-sized particles could reduce the required therapeutic dosages and subsequently reduced its cell toxicity. These nanoparticles are capable to provide local delivery of curcumin targeted to specific areas and thereby preventing systemic clearance. In addition, using specific coating, better pharmacokinetic and internalization of nano-curcumin could be achieved. However, the potential toxicity of nano-carriers for curcumin delivery is an important issue, which should be taken into account in curcumin nano-formulation.

Although smectite clays have gained much interest in recent years as potential sustained local drug delivery vehicles, they have not been yet utilized or assessed as a local drug delivery device for treatment of periodontal disease. In this paper we showed that unique nanostructure and gel-formation ability of clay holds great promise as an effective drug carrier. In particular, we demonstrated the feasibility of using laponite XLG, a smectite clay, as a carrier for in situ delivery of tetracycline that can potentially be used in the treatment and prevention of periodontal disease. The intercalation of tetracycline between the layers of laponite at different acidic pHs and different concentrations of tetracycline was examined. The laponite–tetracycline composite was characterized using X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR) and differential thermal analysis (DTA). The results showed that, in a pH and concentration dependent manner, tetracycline can be intercalated between the layers of laponite nanoparticles. The release study in a simulated saliva solution demonstrated a sustained release of tetracycline from laponite over a 72 hour period. The antimicrobial activity of the released tetracycline was maintained and was not affected by the intercalation of tetracycline into the carrier (laponite) and its release from the carrier.

Hydroxyapatite (HA) is a material of choice for bone grafts owing to its chemical and structural similarities to the mineral phase of hard tissues. The combination of osteogenic proteins with HA materials that carry and deliver the proteins to the bone-defective areas will accelerate bone regeneration. The study investigated the treatment of HA particles with different amino acids such as serine (Ser), asparagine (Asn), aspartic acid (Asp) and arginine (Arg) to enhance the adsorption ability of HA carrier for delivering therapeutic proteins to the body. The crystallinity of HA reduced when amino acids were added during HA preparation. Depending on the types of amino acid, the specific surface area of the amino acid-functionalized HA particles varied from 105 to 149 m2 g–1. Bovine serum albumin (BSA) and lysozyme were used as model proteins for adsorption study. The protein adsorption onto the surface of amino acid-functionalized HA depended on the polarities of HA particles, whereby, compared with lysozyme, BSA demonstrated higher affinity towards positively charged Arg-HA. Alternatively, the binding affinity of lysozyme onto the negatively charged Asp-HA was higher when compared with BSA. The BSA and lysozyme adsorptions onto the amino acid-functionalized HA fitted better into the Freundlich than Langmuir model. The amino acid-functionalized HA particles that had higher protein adsorption demonstrated a lower protein-release rate.