Materials Science and Engineering C

abstract Article history:Received 14 December 2007Received in revised form 25 September 2008Accepted 2 October 2008Available online xxxxKeywords:BiomimeticsBiomoleculesHydroxyapatiteWaste materials This work uses biomolecules in waste and medicinally important materials for the synthesis ofhydroxyapatite nanoparticles. Orange and potato peel, eggshell, papaya leaf and calendula flower extractshave varied biomolecules, which exert a significant, control on the in situ synthesis of nanosizedhydroxyapatite particles. The biomimetic synthesis of inorganic particles using known matrices is alreadywell established, however, there are only a few reports using compound extracts. The synthesizednanocomposite has been characterized using X-ray diffraction, Fourier transform infrared spectroscopy andscanning electron microscopy studies. Role of varied biomolecules in controlled inorganic synthesis mayhavetremendous technological impact.© 2008 Elsevier B.V. All rights reserved. 1. IntroductionThere is a growing interest in the principles governing thecomposition, architecture, and methods of assembly of a variety ofbiological ceramics/biomaterials such as those found in bones, teeth,and shells. The interest stems from the desire to create new syntheticmaterials by mimicking the processes involved, i.e., minerals incombination with a complex organic macromolecular matrix ofproteins, polysaccharides and lipids that not only control the sizeand the shape of the synthesized particles but also keep themagglomeration free [1]. Biological systems have evolved strategies tooffset thermodynamic limitations by establishing kinetic control ofnucleation and crystal growth so that materials of specific size,structure, shape, orientation and organization are synthesized forprecise functional use. Synthetic materials for bone-repair andreplacement need to physically attach and biologically function inintimatecontactwithlivingtissue.Itisclearlyestablishedthatcellularfunctions depend on the size, composition, phase, roughness etc ofbioceramics [2]. There is no bioceramic that meets all orthopedicrequirements. Attempts are on to develop a material that overcomesthebrittlenessofHAp,isosteoinductiveandalsoosteoconductive.Theinterfacialinteractionof suchamaterialandthehostwouldresult inagood ‘bond’. With the ever-increasing requirement of artificialreplacements, there is a need for constant innovation in thebiomaterials field. Waste utilization is necessary not only becausewaste materials are accumulating but also because natural rawmaterials are being exhausted and hence it would be great to reusewaste. Chemical analysis has shown that some wastes are similar incomposition to the natural raw materials and often contain materialsthat are not only compatible but also prove beneficial to thefabrication of ceramics [3,4]. In addition, there is an ever-growingneed to develop clean, non-toxic and environmentally friendly (greenNanotechnology) procedure for nanoparticle synthesis [5].Inanattempt to overcome the problems faced by metallurgists innanoparticle synthesis, our laboratory is using biomolecules fornano-metallic particle synthesis for the past 5–6years, a derivativeof the natural biomineralizationprocess termed biomimetics [6–9].Inthispaper,severalbiomolecules(fromwastematerialslikeorangeandpotato peel, eggshell and also medicinally important substances likepapaya leaf and calendula flower extract) have been used for the insitu synthesis of hydroxyapatite (HAp)—the bone material [10]. WhileXRD proves the formation of HAp phase in the nanocomposites,different morphologies in SEM, and peak shifts in FTIR suggest apossible role of these biomolecules in controlled inorganic synthesis.This basic study may be extrapolated to the synthesis of all advancedmaterials in general. In addition, it would be worthwhile to seewhetherincorporationof thesebiomoleculesintheinsitusynthesisofnanosized HAp improves bone bonding.2. Experimental procedureIn situ synthesis of HAp nanocomposites was carried out usingdifferent waste materials like orange and potato peel, egg shell andalso medicinally important substances like papaya leaf and calendulaflower extract.Egg shell was crushed and 2 g by weight was dissolved in 20 ml 1:3hydrochloric acid:water solution. 400 ml of 0.156 M alkaline diammo-nium hydrogen phosphate salt solution (370 ml 0.156 M diammoniumhydrogen phosphate salt solution+30 ml 1:1 25% liquer ammonia:water) was added to the above and stirred gently but thoroughly.