Biomedical Engineering Reference
In-Depth Information
octoate [0.05% (w/w) of PPG] as a catalyst. (By mass, polypropylene glycol
(PPG) : polylactide (L) : stannous octate is 100 : 138 : 0.05.) The reaction is
carried out under vacuum and a nitrogen atmosphere at 150 1C for 6 h. After
cooling, the products are dissolved in isopropanol and isolated from insol-
uble un-reacted lactide by filtration. Isopropanol is removed via rotary
evaporation and chemical product purity and molecular weight determined
by NMR.
d
n
3
r
4
n
g
|
1
7.5.2 Methacrylation of Poly(lactide-co-propylene
glycol-co-lactide) co-oligomer
Reaction products from the first step (Section 7.5.1) are cooled in a reaction
flask using an ice bucket. Dichloromethane is added to obtain a solution
containing 0.02 mol of PPG-100 mL dichloromethane solvent. Triethylamine
(TEA) and methacryloyl chloride (MAC) (1 : 1 molar ratio) are slowly added at
1 : 4 PPG : MAC molar ratio and then left to react at room temperature
overnight. After filtration, solvent is removed by evaporation. The resultant
product is further purified by repeated dissolution in acetone, filtering and
rotary evaporation until a clear, product is obtained. Further purification is
achieved by product redisolution in dichloromethane and addition of an
equal volume of 1% aqueous HCl. After repeated washing and separation of
organic and aqueous phases the organic phase is further washed with first
followed by distilled water. After final rotary evaporation of solvent, the
product composition can be confirmed using nuclear magnetic resonance
(NMR).
.
7.5.3 Preparation of the Composite
The resultant purified dimethacrylate is combined with 10 wt% hydroxy-
ethyl-methacrylate (HEMA) (Sigma-Aldrich) containing 10 wt% camphor-
quinone (CQ) initiator or 10 wt% N,N-dimethyl-p-toluidine (DMPT) activator
(Sigma-Aldrich). An equal mass of initiator and activator containing mono-
mers are then combined with equimolar monocalcium phosphate mono-
hydrate (MCPM) and b-tricalcium phosphate (b-TCP) filler at levels up to
80 wt%. The resultant paste can be cured using blue light (e.g., a Dentsply
Trubyte Triad
s
2000TM light box or dental curing gun). Typically 20-60 s
light exposure is required with the dental gun to cure 1 mm thick specimens.
7.6 Advances and Challenges
The future of biomaterials is to deliver composite interfaces that instigate
specific cellular functions and direct cell-cell interactions. These smart
interfaces should be capable of sensing and accordingly interacting with the
dynamic surrounding environment. The smart multi-functional composites
represent the future generation platforms for designing three-dimensional
scaffolds for various biomedical applications.
76
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