Transcript No Slide Title

NANOSTRUCTURED and MESOSTRUCTURED BIO-HYBRIDS
Rajendra Kumar Kasinath and Laurie Gower
ABSTRACT
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:
METHODOLOGY Ca(OH) + H PO + chitosan
2
3
4
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.
•an interpenetrating assembly of CaP and chitosan was observed,
PO43- ions
•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.
(A)
Meso-structured films
Transfer 25 ml to Petri dish
Sealed
reactor
Oven dry at 37C
Magnetic
stirrer
SEM, TEM,
FTIR, XRD.
Heater and
stirrer plate
After solvent
extraction
RESULTS
pH and
temperature
probe
Chitosan
solution
Effect of chitosan concentration during synthesis
0 g/ml
20 g/ml
40 g/ml
(B)
70 g/ml
without chitosan
150 g/ml
220 g/ml
70 g/ml chitosan
•Composite suspensions (A) were well
dispersed.
(C)
•Dried films were smooth, continuous
(B) and adherent.
•The degree of nano particulate assembly was optimal at about 40-50 g/ml
of chitosan added during synthesis.
•CaP nano-particles are believed to be
assembled (C) here through
electrostatic interactions between
Organic-Inorganic meso-structured hybrid film
pendent organic chains adsorbed onto the
particles.
•The cross section of the films
showed a remarkable graded
organic-inorganic nanostructure.
Mainly
organic
•Further studies are underway to
understand the exact mechanism.
(Chitosan)
XRD/Rietveld analysis and TEM studies
•Possible applications include
a 2-tiered reservoir for drug
delivery, cementum analogue,
for avulsed teeth re-insertion,
and tissue engineering
scaffolds.
25 nm
37 nm
Mainly
inorganic
(nanoHA)
Levels of morphological grading
TOP
70 g/ml chitosan
without chitosan
•XRD, FTIR and Rietveld
analyses showed that the CaP
nanoparticles were hydroxycarbonated apatite or HCA
(refined crystallite shapes
shown in inset).
•Refined shape for the nanoparticles were consistent with TEM
studies indicating suppressed
growth in the [001] direction. Also
SEAD suggested that the particles
were assembled on their 001
planes.
(004)
(002)
Chitosan film with porous
substructure
•Presence of nanoporosity and nanoparticles heightens the
possibility for both high
drug loading capacity as
well as internalization
by nano-particle
mediated transcytosis.
BOTTOM
Assembled CaP
nano-particles
Bioengineering, Montana Tech of the University of Montana
Materials Science and Engineering, University of Florida
Chitosan-CaP
interpenetrating
structure with
nano-porosity