Sol-gel derived bioactive glass/natural polymer nanocomposite scaffolds Oliver Mahony Ruth Hanly Julian Jones
Project • Goal – Develop a bone tissue regenerating scaffold suitable for in situ bone tissue repair • Strategy – Combine the osteoinductive characteristics of bioactive glass – With tough natural polymers – Gelatin g p y – In class II nanocomposite • GPTMS
Presentation outline • Characterisation of class II materials – C-factor: 0 – 2000 • Techniques – FTIR – Dissolution study – Raman • Preliminary macroporous scaffolds Preliminary macroporous scaffolds
FTIR - Class II nanocomposites Si-O C-Factor • As C-Factor increases the Si-NBO peak disappears. 2000 Amide I Amide II • As C-Factor increases the 1500 influence of the C-O-C/Si- CH 2 peak becomes visible. 1000 • Oxirane peak becomes sorbance 500 visible in high C-Factor Abs samples. 250 100 Si-NBO 0 Si-O-Si Oxirane C-O-C/ C-O-C/ H d Hydrolised li d Si-CH 2 GPTMS 2000 1800 1600 1400 1200 1000 800 -1 ) Wavenumber (cm
Dissolution study C-Factor 500 C Factor 500 C Factor 1500 C-Factor 1500 C F C-Factor 100 t 100 • Amide III peak is 13 Days reduced at longer time points in SBF 8 Days • Indicates polymer is dissolving out of the 5 Days material Absorbance Absorbance bsorbance • With more cross 3 Days y linking this process is A A A slowed 2 Days • C-Factor 1500 shows amide III after 13 id III ft 13 1 Day days retch 6 Hours III I Amide Amide CH Str 1800 1600 1400 1200 1800 1600 1400 1200 1800 1600 1400 1200 -1 ) -1 ) -1 ) Wavenumber (cm Wavenumber (cm Wavenumber (cm
Foam Scaffolds • Extremely high toughness • Stable in solution • Large pore interconnects
Conclusions • GPTMS is working successfully to functionalise gelatin g y g therefore modifying material properties – Improves silica network condensation – fewer NBOs – Improves stability in solution Improves stability in solution • Materials can be foamed using a novel foaming – freeze- drying method – Scaffolds are incredibly tough – Exhibit a pore architecture dictated by foaming process not freeze drying process y g p
Samples
Colorimetric Absorbance
Colorimetric Absorbance Colorimetric Analysis (Combined results - Normalised) Absorbance A 0 100 250 500 1000 1500 2000 C-Factor
Nitrogen Adsorption Modal Pore Size 14 12 10 8 nm 6 4 2 0 100S-HF 100S-I- 100S- 100S- 100S- 100S- 100S- 100S- (OM) 30G 100II- 250II- 500II- 1000II- 1500II- 2000II- 30G 30G 30G 30G 30G 30G
Nitrogen Adsorption Specific Surface Area p 350 300 250 200 m2/g 150 100 50 0 100S-HF 100S-I- 100S- 100S- 100S- 100S- 100S- 100S- (OM) 30G 100II- 250II- 500II- 1000II- 1500II- 2000II- 30G 30G 30G 30G 30G 30G
FTIR - Functionalised Gelatin Si-O Si-O-Si •As GPTMS is increased O i Oxirane peak dominance shifts from C-O-C/ Amide I Si-CH 2 amide peaks to inorganic 2000II-30G Amide II silica-oxygen peaks 1500II-30G •As GPTMS is increased the intensity of the oxirane peak 1000II-30G increases bance 500II-30G 500II 30G •Si-O-Si peak may be Absorb indicative of crosslinking occurring between GPTMS molecules molecules 100II-30G 2000 1800 1600 1400 1200 1000 800 -1 ) Wavenumber (cm
Direct Crosslinking of GPTMS Gelatin Gelatin One bridging and two non bridging oxygens characteristic of functionalised gelatin. g
• Probing the local environment of calcium in apatites • using 43 Ca solid state NMR and X-Ray absorption Spectroscopy •Ca(1) •Ca(2) • Ca 10 (PO 4 ) 6 (OH) 2 •Mg 2+ , Na + •CO 3 2- , HPO 4 2- … • Ca K-edge EXAFS • 43 Ca solid state NMR • Ca K-edge XANES • Simulations •Site preference (at high field) • Preedge intensity • � Distortion around the Ca • � Distortion around the Ca • � Average Ca-O distance • δ iso •in 1 st sphere • � Average Ca-O distance • Edge position • � Changes in the 2 nd • � Coordination number of Ca • P Q Q •coordination sphere • � Disorder around the Ca • Natural apatites • Ca 10-x Mg x (PO 4 ) 6 (OH) 2 • (horse bone cow tooth) (horse bone, cow tooth) •Location of magnesium? •Structure around the calcium?
• Probing the local environment of calcium in Ca 10-x Mg x (PO 4 ) 6 (OH) 2 • using 43 Ca solid state NMR •Natural abundance 43 Ca solid state NMR at 18.8 T •Ca(2) •Ca(1) 80 silicates 60 •0% Mg aluminates d δ iso (ppm) phosphates 40 borates carbonates 20 •calculated •8% Mg 0 -20 -40 •12% Mg •12% Mg -60 2.35 2.40 2.45 2.50 2.55 2.60 2.65 2.70 2.75 •Average d(Ca…O) (in Å) •300 •200 •100 •0 •-100 •-200 •-300 • δ (ppm) (pp ) • 43 Ca NMR seems to show that • Mg enters the Ca(2) site.
• Probing the local environment of calcium in Ca 10-x Mg x (PO 4 ) 6 (OH) 2 • using Ca K-edge X-Ray absorption Spectroscopy • XANES • EXAFS •0 % Mg 0 % Mg •15 % Mg d absorption • 0% Mg k 3 χ (k) • 15% Mg •Normalized • •k (Å -1 ) •4 •6 •8 •10 •0 % Mg •FT of k 3 χ (k) •15 % Mg •-5 •0 •5 •10 •15 •Relative edge position (eV) • •The local geometry around the calcium •is hardly distorted after incorporation of •Mg in the apatite lattice. •1 •3 •5 •7 •9 •r (Å) • 2 nd shell: 2 nd shell: • Ca…O shell: Ca O shell: • Hardly any change in •Decrease in intensity Ca…O distances in Mg-HA • in Mg-HA: sample • presence of Mg in the lattice and loss of crystallinity
• Probing the local environment of calcium in bone and tooth • using 43 Ca solid state NMR • 43 Ca NMR : • Ca K-edge XANES : •14.1 T, MAS 4kHz 14 1 T MAS 4kH •Ca 10 (PO 4 ) 6 (OH) 2 d •absorption •RAPT-1pulse, •bone •24h/spectrum •bone •Normalized •Ca 10 (PO 4 ) 6 (OH) 2 •- •- •5 •-5 •5 •5 •10 •10 •- •5 •0 •0 •0 •5 •10 •15 •15 •15 • 200 • 150 • 100 • 50 • 0 • -50 • -100 • -150 • -200 •Relative •edge •position ( •eV) • δ (ppm) •Comparison of the 43 Ca NMR spectra •of bone and apatite: •Stronger intensity of the pre-edge: • ► δ max of bone at higher frequencies than apatite more distorted environment sample : maximum Ca-O distance in the 1 st shell •around Ca in bone around Ca in bone slightly longer in bone ? li htl l i b ? • ► fwhm in bone bigger than for apatite sample : stronger distribution of chemical shifts and bigger distortion around Ca?
• Probing the local environment of calcium in bone and tooth • using calcium K-edge EXAFS • Ca 10 (PO 4 ) 6 (OH) 2 • Bone • Tooth • Crystallinity: •agrees with XRD agrees with XRD •HA > tooth > bone • Average Ca-O bond distance in the 1st sphere: •agrees with NMR •HA ~ tooth < bone
•Kent ● Warwick ● Imperial ● UCL Sol-Gel Partnership Meeting Sol-Gel Partnership Meeting Friday 29 th August 2008 Department of Physics University of Warwick University of Warwick
XAS measurements of Zn Ti Phosphates p • Phosphate glasses of composition (P O ) (CaO) (P 2 O 5 ) 50 (CaO) 30-x (Na 2 O) 15 (TiO 2 ) 5 (ZnO) x (Na O) (TiO ) (ZnO) • [O]/[P]=3.05 ~ Metaphosphate • Zn K-edge XAS data collected on station 9.3 at Daresbury • Probe the local environment of Zn (first and second neighbour information) g ) • EXAFS data fitted with EXCURV98
EXAFS of Zn Ti Phosphates p 8 6 • ZnO parameters agree 4 k^3 chi(k) 2 0 -2 -4 with tabulated values -6 -8 -10 10 -12 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 • N gives 6 coordination 20 k (ang^-1) 18 16 T k^3 chi(k) •ZnO 14 12 • R is consistent with 4 R is consistent with 4 10 8 6 FT 4 2 coordination 0 -2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 r (ang) 8 6 Sample Neighbour R N d/w factor 4 ) k^3 chi(k) O 1.96 3.94 0.00846 2 ZnO 0 Zn 3.22 11.97 0.01810 -2 -4 O 3.75 9.17 0.01405 -6 -8 Zn 4.57 7.13 0.01834 -10 2 3 4 5 6 7 8 9 10 11 12 13 18 18 O 1.95 6.17 0.01616 T5Z5 k (ang^-1) 16 14 FT k^3 chi(k) P 3.11 1.08 0.00941 •T5Z5 12 10 8 6 O 1.95 6.05 0.01606 T5Z3 4 P 3.09 1.03 0.00911 2 0 -2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 O 1.95 6.41 0.01755 T5Z1 r (ang)
XANES of Zn Ti Phosphates p • Results have characteristics of both four- and six-coordinated environments • Sample has similarity with both crystalline Zn sulfate and Zn phosphate • Mixture of 4 and 6 coordination? Mi t f 4 d 6 di ti ? 1.2 1.0 Absorption (A.U.) ) 0.8 0.6 0.4 0.2 Normalised A 0.0 -0.2 -0.4 Sample T5Z5 Zn sulfate standard (6) -0.6 Zn Phosphate (4) -0.8 0 8 -1.0 9600 9650 9700 9750 9800 9850 9900 Photon Energy (eV)
Possibilities • Samples ground into fine powder for the experiment p • Zn phosphate tetrahydrate has a 4 and 6 coordinated site 4 site is made up of 4 NBOs 6 site is made up of 4 NBOs + 2 water ligands p g • Has sample become hydrated? Proton NMR? Proton NMR? UV-vis and IR to look for change in water peak with heating? g
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