ABSTRACT

1. PO43- ions 0 g/ml 20 g/ml 40 g/ml pH and temperature probe Chitosan solution 70 g/ml 150 g/ml 220 g/ml Sealed reactor Magnetic stirrer Heater and stirrer plate Mainly organic (Chitosan) Mainly inorganic (nano-HA) Chitosan film with porous substructure Chitosan-CaP interpenetrating structure with nano-porosity Assembled CaP nano-particles (A) (B) (C) BOTTOM 25 nm TOP 37 nm (004) (002) NANOSTRUCTURED and MESOSTRUCTURED BIO-HYBRIDS Rajendra Kumar Kasinath and Laurie Gower ABSTRACT METHODOLOGY Ca(OH)2 + H3PO4 + chitosan hybrid susp. Reaction temperature ~100C; acid feed rate 4 ml/min. Chitosan was introduced to the reactants at the point when CaP crystals start to nucleate. Upon completion of the reaction the suspension was sonicated for ½ hr and fixed volumes oven dried at 37C. • Mesostructured hybrid materials are potentially applicable in several biological analogues especially when they possess hierarchical ordering at several length scales. Here we aim to synthesize one such hybrid system consisting of inorganic calcium phosphate (CaP) nano-particles and chitosan bio-polymer. Upon synthesis: • an interpenetrating assembly of CaP and chitosan was observed, • two distinct levels of structure were observed when the composite suspension of CaP-chitosan was dried into films:20-30 nm (primarily nano CaP) and at several microns (consisting of CaP and chitosan) and • films were graded from mainly inorganic (CaP) on the bottom surface to organic (chitosan) on the top. Meso-structured films Transfer 25 ml to Petri dish Oven dry at 37C SEM, TEM, FTIR, XRD. Effect of chitosan concentration during synthesis RESULTS After solvent extraction without chitosan 70 g/ml chitosan • Composite suspensions (A) were well dispersed. • Dried films were smooth, continuous (B) and adherent. • CaP nano-particles are believed to be assembled (C) here through electrostatic interactions between pendent organic chains adsorbed onto the particles. • Further studies are underway to understand the exact mechanism. • The degree of nano particulate assembly was optimal at about 40-50 g/ml of chitosan added during synthesis. Organic-Inorganic meso-structured hybrid film • The cross section of the films showed a remarkable graded organic-inorganic nano-structure. • Possible applications include a 2-tiered reservoir for drug delivery, cementum analogue, for avulsed teeth re-insertion, and tissue engineering scaffolds. XRD/Rietveld analysis and TEM studies Levels of morphological grading without chitosan 70 g/ml chitosan • Refined shape for the nano-particles were consistent with TEM studies indicating suppressed growth in the [001] direction. Also SEAD suggested that the particles were assembled on their 001 planes. • XRD, FTIR and Rietveld analyses showed that the CaP nanoparticles were hydroxy-carbonated apatite or HCA (refined crystallite shapes shown in inset). • Presence of nano-porosity and nano-particles heightens the possibility for both high drug loading capacity as well as internalization by nano-particle mediated transcytosis. Bioengineering, Montana Tech of the University of Montana Materials Science and Engineering, University of Florida