Quiz inorganic non-metallic solid made up of

Quiz in ECE 322 Nano-Ceramics Sean Clarvin Andor 3ECE-D Department of Electronics Engineering Faculty of Engineering, University of Santo Tomas España, Manila, Philippines [email protected] Abstract— In this research paper, the researcher presented the concepts and applications of ceramic nanoparticles or Nano-ceramics including its environmental impact and health hazard. The organization of the discussion provides an extensive explanation on how, why, when, and what questions about the topic. From the developmental history to its composition and material properties and its application in biomedical field is discussed in the paper. At the last section of the paper, the biological hazard of using and production of nanomaterials, in general, provides explanation on different ways on how the exposure of nanomaterials can affect an individual.

Index Terms –Ceramics, Nanotechnology, Nano-ceramics I. INTRODUCTION A ceramic is an inorganic non-metallic solid made up of either metal or non-metal compounds that have been shaped and then hardened by heating to high temperatures. The properties of such materials are hard, corrosion-resistant and brittle. A senior research scientist with Industrial Research Limited, Dr. Ian Brown, explains that the term ‘ceramics’ has a more extensive meaning today. The origin of the word 'Ceramic' comes from the Greek word meaning ‘pottery’. The clay-primarily based domestic wares, artwork items and building merchandise are acquainted to us all, but pottery is simply one a part of the ceramic world.

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In recent times the term ‘ceramic’ has more meaning and consists of materials like glass, advanced ceramics and a few cement systems as well. Traditional ceramics are clay–base. The composition of the clays used, kind of additives and firing temperatures decide the character of the end product. Advanced ceramic substances these days are properly established in lots of regions of regular use, from refrigerator magnets to a growing variety of industries, inclusive of metals production and processing, aerospace, electronics, automotive and employee’s safety.

Manufacturing processes firstly contain thoroughly mixing the very fine constituent material powders. The high temperature permits the tiny grains of the individual ceramic additives to fuse collectively, forming a tough, hard, durable and corrosion-resistant product. 1 It has been well established that the majority behavior of materials can be dramatically altered when made out of nanoscale building blocks. Mechanical, magnetic, optical, and different characteristics of substances have been discovered to be favorably affected. Hardness and strength, for instance, can be significantly more advantageous through consolidating ceramic materials from nanoscale particles.

Ductility and superplastic-forming abilities of nanophase ceramics have now end up viable, leading to new processing routes as a way to be more price-effective than traditional techniques. exceptional development in synthetic chemistry has caused significant advances in material science, making viable the synthesis of numerous substances and materials. The manufacture of ceramics includes heat treatment of tightly squeezed powders. The scale of the building block of those powders has been discovered to have an effect on the properties of the final product. The technique of preparation is very often a determining element in shaping the material and its properties. 2 Ceramic nanoparticles are generally made from oxides, carbides, phosphates and carbonates of metals and metalloids which includes calcium, titanium, silicon, and many others.

They have a huge variety of applications due to a lot of favorable properties, including high heat resistance and chemical inertness. Out of all of the regions of ceramic nanoparticles applications, biomedical field is the most explored one. within the biomedical field, ceramic nanoparticles are taken into consideration to be outstanding carriers for pills, genes, proteins, imaging agents and so on.

Deciding on a suitable approach to put together nanoparticles, together with loading of considerable quantity of drug(s) results in development of effective drug delivery systems which are being explored to an exceptional extent. Ceramic nanoparticleswere efficiently used as drug delivery systems against some of diseases, including bacterial infections, glaucoma, and many others., and most extensively, against cancer. 3 II. DEVELOPMENTAL HISTORY Ceramics is one of the most historical industries on the earth. as soon as people determined that clay may be dug up and shaped into objects through first mixing with water after which firing, the industry was born.

As early as 24,000 BC, animal and human figurines had been crafted from clay and different substances, then fired in kilns partly dug into the ground. Nearly 10,000 years later, as settled groups were set up, tiles had been manufactured in Mesopotamia and India. the primary use of practical pottery vessels for storing water and food is idea to be around 9000 or 10,000 BC.

Clay bricks had been also made around the same time. Fig. 1.

Jomon Ware Deep Bowl (Middle Period) Glass was believed to be found in Egypt around 8000 BC, when overheating of kilns produced a colored glaze on the pottery. Experts estimate that it was not until 1500 BC that glass was produced independently of ceramics and customary into separate objects. Fast forward to the middle ages, when the metal industry was in its infancy. Furnaces at that time for melting the metal had been built of natural materials. When artificial substances with higher resistance to high temperatures (known as refractories) had been developed within the 16th century, the industrial revolution was born. Those refractories created the essential conditions for melting metals and glass on a commercial scale, in addition to the manufacturing of coke, cement, chemical compounds, and ceramics. Another major improvement happened within the second half of the 19th century, when ceramic materials for electrical insulation had been developed. As different inventions came on the scene-which includes automobiles, radios, televisions, computers-ceramic and glass materials have been needed to assist these emerge as a fact, as proven in the following timeline.

4 Year Development 24,000 B.C. Ceramic figurines used for ceremonial purposes 14,000 B.C. First tiles made in Mesopotamia and India 9000-10,000 B.

C. Pottery making begins 5000-8000 B.C. Glazes discovered in Egypt 1500 B.C. Glass objects first made 1550 A.D.

Synthetic refractories (temperature resistant) for furnaces used to make steel, glass, ceramics, cement Mid 1800’s Porcelain electrical insulation Incandescent light bulb 1920’s High-strength quartz-enriched porcelain for insulators Alumina spark plugs Glass windows for automobiles 1940’s Capacitors and magnetic ferrites 1960’s Alumina insulators for voltages over 220 kV Application of carbides and nitrides 1970’s Introduction of high-performance cellular ceramic substrates for catalytic converters and particulate filters for diesel engines 1980’s High temperature superconductors Table 1 History of Ceramics In the 19th century, with the invention of the electric light with the aid of Thomas Alva Edison and the telephone through Alexander Graham Bell, a brand-new generation which could be called the “generation of electricity” started. Ceramics,previously used only as vessels, began to play completely new roles suitable to this new generation. In general, ceramics do not conduct electricity. in comparison to other insulators, which includes paper and wood, ceramics are much less stricken by environmental elements which includes temperature and humidity, giving ceramic components better reliability. through the history of ceramics going back greater than 10,000 years, we’ve found out modeling technology to provide ceramic merchandise in a myriad of shapes. Ceramics have therefore come into massive use as insulators or as insulating materials in regions starting from power lines to family products and have grown to be essential materials that permit people to apply electricity without difficulty. The 20th century brought the arrival of electronics, with the start of radio and tv broadcasts and the discovery of the transistor. this period was facilitated through ceramics from the start, whilst big vacuum tubes of the early 20th century depended on ceramic materials.

within wireless device, only ceramics possessed the properties important to provide high signal output even over high frequency levels. Ceramics couldn’t be replaced with other materials. Ceramics have helped to lessen the dimensions of capacitors and inductors in electronics. Fig.

2 Transistors Since the middle of the 20th century, ceramics have gone through a persistent evolution, and now own exceptional dielectric and magnetic properties. As an end result, electronic components have been miniaturized and made exceptionally functional. Ceramics therefore made a widespread contribution to the downsizing of electronic equipment. If capacitors had no longer been made from ceramics, the portable electronic gadgets we rely on each day, including pocket-sized cellular phones and laptop computers, would in no way have appeared. 5 Today, fine ceramics (also known as ‘Advanced Ceramics’) can be made to possess a huge type of unique characteristics through variations in raw materials, synthesizing techniques and manufacturing strategies.

therefore, they have turn out to be the standard for new materials in countless fields of advanced technology. Because of their light weight, rigidity, physical stability and chemical resistance, huge ceramic components numerous meters in size at the moment are utilized in system for production semiconductors and liquid crystal displays. further, their high reliability and successful integration with metals permits them for use in a developing variety of automobile additives.

6 Fig. 3 Advanced ceramics materials Segment Products Automotive Diesel engine cam rollers, fuel pump rollers, brakes, clutches, spark plugs, sensors, filters, windows, thermal insulation, emissions control, heaters, igniters, glass fiber composites for door chassis and other components Aerospace Thermal insulation, space shuttle tiles, wear components, combustor liners, turbine blades/rotors, fire detection feedthroughs, thermocouple housings, aircraft instrumentation and control systems, satellite positioning equipment, ignition systems, instrument displays and engine monitoring equipment, nose caps, nozzle jet vanes, engine flaps Chemical/ petrochemical Thermocouple protection tubes, tube sheet boiler ferrules, catalysts, catalyst supports, pumping components, rotary sealsCoatings Engine components, cutting tools, industrial wear parts, biomedical implants, anti-reflection, optical, self-cleaning coatings for building materials Electrical/ electronic Capacitors, insulators, substrates, integrated circuit packages, piezoelectric, transistor dielectrics, magnets, cathodes, superconductors, high voltage bushings, antennas, sensors, accelerator tubes for electronic microscopes, substrates for hard disk drives Environmental Solid oxide fuel cells, gas turbine components, measuring wheels/balls for check valves (oilfields), nuclear fuel storage, hot gas filters (coal plants), solar cells, heat exchangers, isolator flanges for nuclear fusion energy research, solar-hydrogen technology, glass fiber reinforcements for wind turbine blades Homeland security/military Particulate/gas filters, water purification membranes, catalysts, catalyst supports, sulfur removal/recovery, molecular sieves Table 2 Applications of Advanced Ceramics The development of products and methods containing ceramic nanoparticles has generated novel and captivating applications of these materials within the past decades. similarly, to these thrilling findings, ceramic nanoparticles tend to be exceptionally stable.

Their routes of synthesis are widely recognized and comparatively cheap. The mixture of technical benefits and profuse funding in research and improvement expanded the wide variety of patents and publications on this area. Even more currently (since 2002), research applications primarily based on toxicology, eco-toxicology, ethics and public notion of nanotechnologies have talked about capable dangers and influences associated with nanotechnologies.

due to their extensive employment, the ceramic nanoparticles considerably have been studied through approach of these new techniques and numerous surprising unsafe consequences which includes high toxicity and environmental persistency were discovered. The future of nanoceramics is most anticipated especially in the field of biomedical area to treat diseases especially cancer while providing a cost-effective method. III.

COMPOSITION/MATERIAL CHEMISTRY Remarkable progress in synthetic chemistry has led to significant advances in material science, making possible the synthesis of various substances and materials. The manufacture of ceramics involves heat treatment of tightly squeezed powders. The size of the building block of these powders has been found to affect the properties of the final product. Fig.

4 Nanoceramic Material A. Preparations The method of preparation is very often a determining factor in shaping the material and its properties. For example, burning Mg in O2 (MgO smoke) yields 40-80-nm cubes and hexagonal plates, whereas thermal decomposition of commercial Mg(OH)2, MgCO3, and especially Mg(NO3)2 yields irregular shapes often exhibiting hexagonal platelets. Surface areas can range from 10 m2/g (MgO smoke) to 150 m2/g for Mg(OH)2 thermal decomposition. On the other hand, aerogel-prepared Mg(OH)2 can lead to MgO with surface areas as high as 500 m2/g. 2 1) Physical Methods a) Vapor condensation methods Gas-condensation techniques to produce nanoparticles directly from a supersaturated vapor of metals are among the earliest methods for producing nanoparticles.

They generally involve two steps: First, a metallic nanophase powder is condensed under inert convection gas after a supersaturated vapor of the metal is obtained inside a chamber. Second, the powder is oxidized by allowing oxygen into the chamber (to produce metal oxide powder). A subsequent annealing process at high temperatures is often required to complete the oxidation. The system consists of a vapor source inside a vacuum chamber containing a mixture of an inert gas, usually argon or helium, mixed with another gas, which is selected based on the material to be prepared. Oxygen is mixed with the inert gas to produce metal oxides. NH3 is usually used to prepare metal nitrides and an appropriate alkane or alkene, as a source of carbon, is usually used to prepare metal carbides. Nanoparticles are formed when supersaturationis achieved above the vapor source. A collection surface, usually cooled by liquid nitrogen, is placed above the source.

The particles are transported to the surface by a convection current or by a combination of a forced gas flow and a convection current, which is set up by the difference in the temperature between the source and the cold surface. Some improved systems involve a way to scrap the nanoparticles from the cold collection surface so that the particles would fall into a die and a unit where they can be consolidated into pellets. Supersaturated vapor can be achieved by many different vaporization methods. The most common techniques include thermal evaporation, sputtering, and laser methods.

A variety of nanoscale metal oxides and metal carbides have been prepared using laser-vaporization techniques. The advantages of vapor condensation methods include versatility, ease in performance and analysis, and high-purity products. On the other hand, they can be employed to produce films and coatings. Furthermore, laser-vaporization techniques allow for the production of high-density, directional, and high-speed vapor of any metal within an extremely short time. Despite the success of these methods, they have the disadvantage that the production cost is still high because of low yields. Heating techniques have other disadvantages that include the possibility of reactions between the metal vapors and the heating source materials.

b) Spray pyrolysis Fig. 5 Spray pyrolysis process This technique is known by several other names including solution aerosol thermolysis, evaporative decomposition of solutions, plasma vaporization of solutions, and aerosol decomposition. The starting materials in this process are chemical precursors, usually appropriate salts, in solution, sol, or suspension. The process involves the generation of aerosol droplets by nebulizing or” atomization” of the starting solution, sol, or suspension. The generated droplets undergo evaporation and solute condensation within the droplet, drying, thermolysis of the precipitate particle at higher temperature to form a microporous particle, and, finally, sintering to form a dense particle. Different techniques for atomization are employed including pressure, two-fluid, electrostatic, and ultrasonic atomizers.

These atomizers differ in droplet size (2-15 mm), rate of atomization, and droplet velocity (1-20 m/sec). These factors affect the heating rate and residence time of the droplet during spray pyrolysis which, in turn, affect some of the particle characteristics including particle size. For a specific atomizer, particle characteristics, including particle size distribution, homogeneity, and phase composition depend on the type of precursor, solution concentration, pH, viscosity, and the surface tension.

Aqueous solutions are usually used because of their low cost, safety, and the availability of a wide range of water-soluble salts. Metal chloride and nitrate salts are commonly used as precursors because of their high solubility. Precursors that have low solubility or those that may induce impurities, such as acetates that lead to carbon in the products, are not preferred. The advantages of this method include the production of high-purity nanosized particles, homogeneity of the particles as a result of the homogeneity of the original solution, and the fact that each droplet/particle goes through the same reaction conditions. The disadvantages of spray pyrolysis include the need for large amounts of solvents and the difficulty to scale-up the production. The use of large amounts of nonaqueous solvents increases the production expenses because of the high cost of pure solvents and the need for proper disposal. 2) Chemical Methods a) Sol-gel technique Fig.

6 Sol-gel processThe sol-gel process is typically used to prepare nanometer-sized particles of metal oxides. This process is based on the hydrolysis of metal reactive precursors, usually alkoxides in an alcoholic solution, resulting in the corresponding hydroxide. Condensation of the hydroxide by giving off water leads to the formation of a network-like structure. When all hydroxide species are linked, gelation is achieved and a dense porous gel is obtained. The gel is a polymer of a three-dimensional skeleton surrounding interconnected pores. Removal of the solvents and appropriate drying of the gel result in an ultrafine powder of the metal hydroxide.

Further heat treatment of the hydroxide leads to the corresponding powder of the metal oxide. As the process starts with a nanosized unit and undergoes reactions on the nanometer scale, it results in nanometer-sized powders. For alkoxides that have low rates of hydrolysis, acid or base catalysts can be used to enhance the process. When drying is achieved by evaporation under normal conditions, the gel network shrinks as a result of capillary pressure that occurs and the hydroxide product obtained is referred to as xerogel. However, if supercritical drying is applied using a high-pressure autoclave reactor at temperatures higher than the critical temperatures of solvents, less shrinkage of the gel network occurs as there is no capillary pressure and no liquid-vapor interface, which better protects the porous structure. The hydroxide product obtained is referred to as an aerogel. Aerogel powders usually demonstrate higher porosities and larger specific surface areas than analogous xerogel powders. Sol-gel processes have several advantages over other techniques to synthesize nanopowders of metal oxide ceramics.

These include the production of ultrafine porous powders and the homogeneity of the product as a result of homogeneous mixing of the starting materials on the molecular level. b) Precipitation from solutions Precipitation is one of the conventional methods to prepare nanoparticles of metal oxide ceramics. This process involves dissolving a salt precursor, usually chloride, oxy-chloride or nitrate, such as AlCl3 to make Al2O3, Y(NO3)3 to make Y2O3, and ZrCl4 to make ZrO2, in water. The corresponding metal hydroxides are usually obtained as precipitates in water by adding a base solution such as sodium hydroxide or ammonium hydroxide solution.

The remaining counter-ions are then washed away and the hydroxide is calcined after filtration and washing to obtain the final oxide powder. This method is useful in preparing ceramic composites of different oxides by co-precipitation of the corresponding hydroxides in the same solution. Solution chemistry is also used to prepare non-oxide ceramics or pre-ceramic precursors that can be converted to ceramics upon pyrolysis. One of the disadvantages of this method is the difficulty in controlling the particle size and size distribution.

Very often, fast and uncontrolled precipitation takes place resulting in large particles. IV. MATERIAL PROPERTIES Ceramics possess their own chemical, physical, mechanical, and magnetic properties that are different from those of other materials such as metals and plastics. The properties of ceramics depend mainly on the type and the amounts of materials in their composition. However, the size of the building blocks of a ceramic material has been found to play an important role in its properties.

When materials are prepared from nanometer-sized particles, a significant portion of the atoms become exposed on the surface. As a result, such materials exhibit unique properties that are remarkably different from those of the corresponding bulk. The physical and chemical properties of nanoparticles show the gradual transition from atomic or molecular to condensed matter systems.

2 1) Chemical Properties Ceramic materials are relatively inert, especially crystalline materials that tend to have perfect structures with minimum number of defects. Most of the reactivity of these materials involves the surfaces where coordinatively unsaturated as well as defect sites exist. The behavior of the surface toward other species and the nature of interaction depend on the composition and the morphology, which determine the nature and the degree of surface interactions with other substances. Most of the time, interactions are limited to adsorption on the surface, which does not affect the bulk making these materials good corrosion-resistant. The possibility of preparing ceramic powders in high surface areas with high porosity makes them well desired in some advanced applications. One example is the use of ceramic materials as supports for heterogeneous catalysts.

Another example is the use of such materials in biomedical applications, where the surface of nanophase ceramics exhibits a remarkably improved biomedicalcompatibility compared to conventional ceramics, as discussed below. 2) Mechanical Properties Ceramics are very strong materials showing considerable resistance against compression and bending. Some ceramic materials are similar to steel in strength. Most ceramics retain their strength at high temperatures. Silicon carbides and silicon nitrides, as an example, retain their strength at temperatures as high as 1400°C. As a result, such materials are used in high-temperature applications. Many of the physical and mechanical properties are particle-size dependent.

As a result, several systems of nanophase ceramics have exhibited quite interesting and favorably enhanced mechanical properties. 3) Electrical Properties Ceramics include electrical conducting, insulating, and semiconducting materials. Chromium oxide is an electrical conductor, aluminum oxide is an insulator, while silicon carbide behaves as a semiconductor.

As a result, ceramic materials have been used in a variety of electronic applications based on their electrical behavior. Several electrical properties are particle-size and composition dependent. Electrical resistance and dielectric constant, as an example, for some systems increased as a result of small particle size.

Conductivity of some mixed oxide ceramics, such as lithium aluminosilicate, is higher than that of their constituent oxides. 4) Magnetic Properties Some ceramic materials possess magnetic properties. These include iron oxide-based ceramics and oxides of chromium, nickel, manganese, and barium. Ceramic magnets are known to exhibit high resistance to demagnetization. As a result, several ceramic powders have been employed in a wide range of electronic and magnetic applications as discussed below. The fabrication of such materials from ultrafine particles can significantly enhance their magnetic behavior. The fact that in nanometer-sized particles a large portion of the atoms are on the surface, where the coordination numbers are less than that for bulk atoms, affects several parameters including unique surface/interface behavior and different band structure, which both lead to magnetism enhancement.

It is now well established that one of the requirements to achieve appropriate coercivity and high magnetization saturation is to fabricate such materials in highly divided particles, preferably in the nanometer-sized range, with homogeneity and narrow size distribution. 5) Reduced brittleness and enhanced ductility and superplasticity Superplasticity and ductility refer to the capability of some polycrystalline materials to undergo extensive tensile deformation without necking or fracture. Ceramic brittleness is the biggest technical barrier in practical applications, especially in load-bearing applications. Theoretical and experimental results provide evidence for the possibility that traditional brittle materials can be ductilized by reducing their grain sizes. 1 When made from nanoparticles, brittle ceramics can be superplastically deformed at modest temperatures and then heat treated at higher temperatures for high-temperature strengthening.

The capability to synthesize superplastic ceramic materials is now established. Nanocrystalline ceramics deform at faster rates, lower stresses, and lower temperatures. One important use of superplasticity in ceramics is diffusion bonding, where two ceramic parts are pressed together at moderate temperatures and pressures to form a seamless bond through diffusion and grain growth across the interface. Diffusion bonds form more easily in nanocrystalline ceramics than in larger grained ceramics as a result of both the enhanced plastic flow of nanocrystalline ceramics and the larger number of grain boundaries they provide for diffusional flux across the interface. V.

APPLICATIONS Ceramic Nanoparticles: Fabrication Methods and Applications in Drug Delivery 7 Ceramic nanoparticles are inorganic systems with porous characteristics. Since these particles can be easily engineered with the desired size and porosity, keen interest has recently been shown in utilizing ceramic nanoparticles as drug vehicles. Considerable research has been done exploring typical biocompatible ceramic nanoparticles such as silica, Titania, alumina etc. The newly emerging area of utilizing inorganic (ceramic) particles with entrapped biomolecules has potential applications in many frontiers of modern materials science including drug delivery systems.Fig. 7 Types of Nanoceramic drugs The advantages of ceramic nanoparticles include easy preparation with desired size, shape and porosity, and no effect on swelling or porosity with change in pH.

In recent times, the development of new ceramic materials for biomedical applications has hastened. Nanoscale ceramics such as hydroxyapatite (HA), calcium carbonate (CaCO3), zirconia (ZrO2), silica (SiO2), titanium oxide (TiO2), and alumina (Al2O3) were made from new synthetic methods to improve their physical-chemical properties seeking to reduce their cytotoxicity in biological systems. The controlled release of drugs is one of the most exploited areas in terms of ceramic nanoparticle application in biomedicine where, the dose and size are important. Also, some features that make these nanoparticles a potential tool in controlling drug delivery are high stability, high loading capacity, easy incorporation of hydrophobic and hydrophilic systems, and different routes of administration (oral, inhalation, etc.). In addition, a variety of organic groups which may be functionalized on their surfaces allow for a directed effect. Calcium phosphates are suitable to be used as a carrier for drugs, non-viral gene delivery, antigens, enzymes, and proteins.

Calcium phosphate nanoparticles provide the following advantages: • Deliver drugs in minimally invasive manner just as polymeric nanoparticles • Easy to fabricate and inexpensive • Longer biodegradation time • Do not swell or change porosity • Stable upon variation in temperature and pH • Possess same chemistry, crystalline structure and size as the constituents of targeted tissues • Fabrication methods enhance their bioavailability and biocompatibility even before releasing drugs Sol-Gel Process In the soft chemistry route, the metal alkoxides convert to amorphous gels of metal oxides through hydrolysis and condensation reactions. Liu et al. successfully synthesized hydroxyapatite using the sol-gel process at lower temperatures. A two-step procedure was employed. Triethyl phosphite was initially hydrolysed with water, followed by the addition of an aqueous calcium nitrate solution. Subsequently, the amorphous gel transformed into a well crystallized apatite at relatively low temperatures (300-400°C). The calcinated gels showed a nanoscale microstructure, with grains of 20-50 nm diameters. Appropriate heat treatment between 300 and 400 °C resulted in preparation of apatite exhibiting a nanoscale size, low crystallinity, carbonated apatitic structure, resembling that of human bone apatite.

The final product and the optimum synthesis conditions such as calcination temperature largely depend on chemical nature of the precursors. The sol–gel materials are transformed to ceramics by heating at relatively low temperatures and have better chemical and structural homogeneity than those obtained by conventional methods. The sol-gel method offers a molecular-level mixing of the calcium and phosphorus precursors, which is capable of improving the chemical homogeneity of the resulting hydroxyapatite to a significant extent. A number of calcium and phosphate precursor combinations have been employed for sol-gel synthesis. The major limitation of the sol-gel technique is linked to the possible hydrolysis of phosphates. Fig.

8 Drug Delivery using nanoceramic carriers Application of Calcium Phosphate in Drug Delivery, especially hydroxyapatite has been widely used in treatment of bone diseases such as osteoporosis. These are also being explored as drug carriers for the treatment of cancer and other diseases. The formulated delivery systems were able to prolong drug release due to very low rate of degradation of hydroxyapatite (at neutral or alkaline pH) and possessed excellent biocompatibility. The paper concludes that the methods of synthesis and applications of inorganic nanoparticles (Ceramic nanoparticles) in the field of drug delivery makes it evident that these nanoparticles hold agreat potential as drug carriers to deliver and target the active pharmaceutical ingredient to the desired site in a controlled manner, resulting in achievement of a therapeutic concentration of drug at target site. Ceramic nanoparticles offer a number of technical advantages in terms of drug delivery. Most researched area for the application of ceramic nanoparticles is cancer, where promising results have been obtained.

A number of facile methods for preparation of these nanoparticles are available and have been continuously undergoing modifications to achieve better desired characteristics of synthesized nanoparticles. All these favorable facts have resulted in several patents and publications in this area during recent years. Thus, ceramic nanoparticles hold the promise of better, safer and cost-effective drug delivery agents in future of biomedical science.

VI. ENVIRONMENTAL IMPACT Size, shape, and surface chemistry are among key properties central to the utility of nanomaterials. These properties also fundamentally influence the way these materials interact within the human body.

Understanding how the various characteristics of nanomaterials affect their biocompatibility and toxicity will support development of safer nanomaterials and nanotechnology products. Development of well-integrated multidisciplinary research teams is critical to enable these studies. One example of the roles nanomaterial properties play is how changes to surface chemistry can affect the biocompatibility and toxicity of particular nanomaterials. Positively charged nanoscale lipid vesicles (nanovesicles) induce cerebral edema, but neutral and low concentrations of negatively charged nanovesicles do not (Lockman et al., 2004). Studies have shown that modifying the surface of nanomaterials with surfactants or biocompatible polymers (e.

g., polyethylene glycol) reduces the toxicity in vitro (Derfus et al. 2004) and alters the half-life and tissue deposition in vivo (Ballou et aL, 2004). Such findings are relevant to drug delivery, for understanding the potential distribution of nanomaterials in the body, and for evaluating biocompatibility and toxicity. However, these findings are material-specific and are difficult, at present, to extend to broad categories/classes of materials.

Nanoscale materials similarly may vary in their ability to be introduced into and circulated though the body. For example, one study discovered ultrafine carbon transport from the olfactory mucosa in nasal passages, via the olfactory nerve, to the olfactory bulb inside the blood-brain barrier (Oberdorster et al., 2004). Other studies have demonstrated that semiconducting quantum dots translocate to local lymph nodes in animals following intradermal or footpad injections (Kim et al.

, 2003; Roberts et aL, 2005) or following topical application to dermabraded skin (Gopee et al., 2006). Seemingly more so than at larger scales, the shapes of nanomaterials have interesting implications for biocompatibility. Current manufacturing technologies with atom-by-atom assembly of nanomaterials under highly controlled conditions allow synthesis of materials having the same chemical composition but different shapes. Studies of zinc oxide (ZnO) nanomaterials suggest that changes in shape alone (e.g.

, particles, cages, and “belts’) influence physicochemical properties (Wang et al., 2004), which in turn can influence biological activity. 8 Exposure Routes Assessing exposure to nanomaterials requires understanding relevant routes of exposure. For a material (nanoscale or otherwise) to induce a measurable biological response, it must enter the body, usually through the respiratory tract, skin, eyes. or digestive tract, or through intravenous exposure of patients and healthy donors, and reach an appropriate site in the body at sufficient concentration and for a necessary length of time. The relationship of exposure to uptake differs for each route of exposure and is a function of the physicochemical characteristics of the material and the structure and function of the organ or system that acts as the entry point. 8 A. Respiratory Tract The upper airways of the lung have a relatively robust protective cellular layer (epithelium), but the alveoli (the regions of the lungs where gas exchange occurs) are deeper and more vulnerable.

Research has shown that nanomaterials smaller than 100 am (that is, those not in large agglomerates) deposit at higher concentrations in the alveoli, whereas agglomerated nanomaterials with diameters larger than 100 am deposit at higher concentrations in the upper Sway. Research has also demonstrated that nanoscale particles can be taken up by sensory nerve endings within the airway epithelia. followed by axonal translocation to ganglionic and central nervous system structures. For example. as noted earlier.

animal studies have shown that inhaled or intranasally instilled nanoscale particles can be transported via the olfactory nerve to the olfactory bulb (Oberdorster et aL, 2004; International Commission of Radiologic Protection, 2003). B. Skin The skin has a strong external bather, the stratum come= which protects sensitive internal organs from environmental exposures. Although healthy skin is generally considered impervious to particle exposures.

some studiessuggest that nanoscale materials penetrate hair follicles and sebaceous glands or move through the lipid pathway located between the cells of the stratum corium (Banat Muller-Goymana, 2000). The relationship of the dose of nanomaterial to which the skin is exposed and the dose absorbed into the skin is not well understood. Furthermore, there is conflicting evidence regarding the ability of particulates to penetrate through the stratum comeum. Several unpublished studies suggest that nanoscale titanium dioxide does not penetrate the skin (RS/RAEng, 2004). whereas other recent reports demonstrate that nanoscale particles can enter the epidermis and dermis though intact stratum comeum (Ryman-Rasmussen et al., 2006) and through compromised stratum corium, resulting in translocation of materials to the lymph nodes and liver (Gopee et al.

20067). C. Digestive Tract Particle uptake in the digestive tract has been well studied mostly for drug delivery. This complex system absorbs macromolecules at numerous points along its length. Several studies demonstrate uptake of nanomaterials, including organ-spPrifir targeted uptake that tailinis surface modification as the targeting methodology.

Nanomaterials also can be ingested when they are transferred from hand to mouth, and ingestion accompanies inhalation exposure when particles are cleared from the respiratory tract via the mucosocilialy escalator (International Commission of Radiologic Protection, 2003). D. Injection or Implantation Particles may be injected into a patient via the subcutaneous. intramuscular. or intravenous routes. or may be injected directly into a tissue. organ. or tumor.

These may be intended to target specific organs. tumors, and diseases or may serve as imaging and diagnostic agents. The disposition and biocompatibility of the particles will depend on ADNIETOX profiles—which are blown to be tightly linked to particle size and surface chemistry. Particles may also be released from implanted devices.

whether as a result of designed resorption. or as a result of matrix material wear and degradation. These may accumulate in local tissues or be transported to filter organs. or maybe excreted. VII. REFERENCES 1 “What are ceramics?,” 27 April 2010. Online. Available: https://www.

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