PLGA−POSS End-Linked Networks with Tailored Degradation and Shape Memory Behavior

Abstract

Biodegradable PLGA oligomers were synthesized to feature a hybrid organic-inorganic moiety, POSS, incorporated at the center of each chain by using it as the ring-opening initiator. After end-capping with vinyl groups, the macromers were photocured into networks with POSS content ranging from 10 to 41 wt %. Increasing POSS inclusion increased the crystallinity of the network while decreasing the degradation rate due to its hydrophobic and nonhydrolyzable properties. It was found that co-curing PLGA oligomers with and without POSS in the backbone could be utilized to create networks with a reduced POSS loading level, at a given cross-link density, allowing tuned crystallinity. Hydrolytic degradation of the co-cured networks was slower than for the PLGA homonetwork but still led to complete degradation after 14 weeks in PBS buffer at 37°C. The networks exhibited versatile shape memory properties, exploiting the combination of covalent cross-linking and the glass transition, POSS-phase melting temperature, or both as the shape-switching trigger. Using the glass transition was found to yield the best shape fixing, while the best recovery percentages (∼100%) were achieved when the melting transition was used. One network, with 24 wt % POSS, was able to be fixed in a temporary shape by POSS crystallization and to largely preserve this shape during degradation. After 4 weeks and 60% mass loss, 50% of the initial deformation still remained while the PLGA network (shape fixed through T g ) had recovered fully. Our findings are expected to impact future design of biodegradable polymers with shape memory, having revealed the precise tuning of properties possible through controlled placement of a crystallizable and hydrophobic moiety in the polymer network chain.

Star-shaped polyhedral oligomeric silsesquioxane-polycaprolactone-polyurethane as biomaterials for tissue engineering application

“…The degradation rate can be determined by varying POSS content; a higher POSS content corresponds to a slower degradation rates. 27 Together with the mechanical integrity, the degradation rate of the POSS-PCL-PU films can be controlled to achieve a scaffold that degrades slowly during the initial period, followed by rapid degradation at the later phase after the growth of the cells. This behavior is desired because the scaffold's structural integrity is required in the initial phase for cells to attach and proliferate.…”

Synthesis of grafted polysilsesquioxane by ring-opening polymerization of lactide and trimethylene carbonate

“…The presence of poly(TMC) also affected the crystallization of poly(LA), as expected. 14,24 The GrPLC1 curve shows an undetectable peak for T m , even in the first heating run. The results demonstrate that the incorporation of TMC units changes the crystallinity of the graft chains containing LA units.…”

“…Poly(TMC) has been reported to have a lower T g , of less than À20 1C. 24 Consequently, the observed T g s are thought to show those of the grafted LA polymer. The peak observed at ca À15 1C seems to be the T g of the grafted poly(TMC) in the case of GrPCL2.…”

Hydrolytic degradation of POSS–PEG–lactide hybrid hydrogels

“…Several studies have assessed the influence of POSS moieties on the degradation of polymeric biomaterials. Knight et al [17] investigated the in vitro degradation of PLA-based polyurethanes with 20.8 wt.% POSS incorporation and found a slower rate of degradation compared with the non-POSS material after eight weeks exposure in a PBS buffer at 37 C. More recently, Knight et al [16] studied the effect of POSS content on the degradation profile of poly(lactide-co-glycolide) (PLGA) containing 10e41 wt.% POSS. The authors observed that by increasing the POSS content in the system the rate of degradation decreased.…”