Abstract
Novel green classes of biodegradable polylactide-based triblock polyurethane (TBPU) polymers were synthesized. Owing to their tailored mechanical properties, improved degradation rates, and the enhance cell attachment potential compared with polylactide-homopolymer, they tested for biomedical applications. Triblock copolymers (TB) of different lactide and polyethylene glycol composition were first fabricated by ring-opening polymerization using tin octoate as catalyst. Afterwich polycaprolactone diole (PCL-diole) is reacted with TB copolymers using 1,4-butane diisocyanate (BDI) as nontoxic chain extender to form the final TBPUs. Final composition, molecular weight, thermal properties, hydrophilicity and biodegradation of the obtained TB and TBPU were studied and characterized using 1H-NMR, GPC, FTIR, DSC, SEM and contact angle measurements. Results obtained from the high molecular weight members of TBPUs showed improved hydrophilicity and degradation rates along with tailored mechanical properties. Nanocomposites obtained by reinforcing TBPU3 with 7% (w/w) BCNW showed ~16% increase in tensile strength and 330% in % elongation compared with PL-homopolymer. Those polymers and their nanocomposites demonstrated promising potential to be used as bone cement, and in regenerative medicin.
Highlights
The triblock polyurethane (TBPU) of low molecular weight can be utilized as drug delivery carriers and implantable membranes where fast degradation and drug stability are required, whereas the TBPUs of higher molecular weights can be used in fabrication of porous scaffold that are used in tissue engineering scaffolds
The results showed that the cell attachment efficiency on Multi-PLE 4/1(4/1 refers to the molar ratio of lactidyl units to ethylene oxide units) films was close to that on PLLA film, while the cell proliferation on Multi-PLE4/1 and Multi-PLE2/1 scaffolds was better than that on PLLA scaffold, which was closely related to the improved hydrophilicity of Multi-PLE copolymers due to the incorporation of poly(ethylene glycol) (PEG) in comparison with pure PLLA [76]
Results obtained from the mechanical properties study carried out by Qu et al [134] showed that both tensile strength and elongation at break significantly improved and reached a maximum in the composite obtained by blending poly(lactic acid) (PLA)/PEG when cellulose nanofibril of 3% content was added to the blend, and decreased with further increase of cellulose nanofibrils
Summary
Biodegradable polymers are used in an increasingly large number of biomedical applications. To overcome the current limitations that confront the use of the previously mentioned biodegradable homopolymers, the current project focus on the synthesis of wide range of molecular weights of green nontoxic biodegradable triblock polyurethanes (TBPUs) that have improved hydrophilicity, degradation rate and cell attachment abilities over the pure homopolymers PLA and PCL Those newly designed polyurethane can be used either for rapid drug delivery system and MRI contrast agent, as well as in tissue engineering scaffolds. The new BCNW/TBPUs nanocomposite will be envisioned, from one side, to show improved interfacial adhesion with the newly generated cells due to the presence of hydrophilic PEG and BCNW in the hydrophobic polymer matrix, and from the other side to improve the mechanical strength and biodegradation rate This project is a multifaceted challenge, since obtaining a new group of materials with a given set of mechanical and physical properties, to be used in biomedical applications, is conditional upon being biocompatible and biodegradable
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