3.MICRO AND NANO DRUG DELIVERY SYSTEMS(cont.)

3.MICRO AND NANO DRUG DELIVERY SYSTEMS(cont.)
3.3.Ceramic Nanoparticles

Use of ceramics in medicine is especially significant in dental and orthopedic applications as strengthening materials for the hard tissue implants. Hydroxyapatite (HA) is a ceramic naturally existing in the bone structure and therefore its use in the hip or knee prosthesis can reduce the risk of rejection and stimulate the production of osteoblasts which are the cells responsible for the growth of the bone matrix.Ceramic particles effectively protect the doped molecules (enzymes, drugs, etc) against denaturation induced by external pH and temperature. In addition, their surfaces can be easily modified with different functional groups. They can be conjugated to a variety of monoclonal antibodies or ligands for targeting purposes in vivo. Ceramic particles with entrapped biomolecules have a great potential in delivery of drugs. Such particles, including silica, alumina, titania, etc, are known for their compatibility with biological systems. They have several advantages such as the ease of preparation with the desired size, shape and porosity under ambient conditions, high stability such as no swelling or change in shape in environmental conditions.McQuire et al (2005) synthesized hydroxyapatite sponges by using aminoacid coated HA nanoparticles dispersed within a viscous polysaccharide (dextran sulfate) matrix and examined the use of these materials for the viability and proliferation of human bone marrow stromal cells in order to search possibility for cartilage or soft tissue engineering. Rusu et al (2005) studied size-controlled hydroxyap- atite nanoparticles prepared in aqueous media in a chitosan matrix from soluble precursors salts bone for the purpose of tissue engineering applications. Serbetci et al (2000, 2002, 2004) prepared acrylic bone cements with addition of HA microparticles. They examined the effect of HA addition on the properties of the cement. They reported enhancement of mechanical, thermal and biological properties depending on the added amount of HA.Christel and co-workers (1984) implanted calcium phosphate bioglass ceramics in the tibiae of rabbits to study the interface of bioceramics. It was reported that hydroxyapatite surface give rise to a closer contact with new bone than calcium phosphate glass ceramics. Lin and colleagues (1996) implanted bioglass discs into the condyle area of rabbits. The failure load, when an implant detached from the bone or when the bone itself broke, was measured by a push-out test and compared with sintered hydroxyapatite bioceramic. Vogel and coworkers (2001) implanted bioglass particles in the distal femoral epiphysis of rabbits and examined bone formation at the implant site. They discussed the parameters (implantation model, particle size and surface-area-to-volume ratio) as possible parameters determining bone regeneration. Recently Amaral and colleagues (2002) studied wettability and surface charge properties of Si3 N4 –bioglass biocomposites. They determined that the examined bioglass had comparatively higher hydrophilic character and surface tension value than the most common bioceramics. The presence of very high negative zeta potential at neutral pH influenced albumin adsorption. They also studied mechanisms in terms of entropy and enthalpy gains from conformational unfolding and cation coadsorption (Amaral et al 2002).Zeng and co-workers (2002) prepared Al2 O3 –A/W bioglass coating through tape casting process by selecting low melting point A/W bioglass to decrease the Al2 O3 sintering temperature and modify the bioactivity of implant. On the other hand, Xin and colleagues (2005) investigated the formation of calcium phosphate (Ca-P) on various bioceramic surfaces in simulated body fluid (SBF) and in rabbit muscle. The bioceramics were sintered porous solids, including bioglass, glass-ceramics, hydroxyapatite, -tricalcium phosphate and -tricalcium phosphate. They compared the ability of inducing Ca-P formation and obtained similar results in SBF but observed considerable variations in vivo.

Source:
Nanomaterials and Nanosystems for Biomedical Applications
NESRIN HASIRCI
Middle East Technical University, Faculty of Arts and Sciences, Department of Chemistry, Ankara 06531, Turkey