It is increasingly being recognised within the field of tissue
engineering that the regenerative capacity of biomaterial scaffolds can
be augmented via the incorporation of gene therapeutics. However, the
field still lacks a biocompatible gene delivery vector which is capable
of functionalizing scaffolds for tailored nucleic acid delivery. Herein,
we describe a versatile, collagen based, gene-activated scaffold
platform which can transfect autologous host cells in vivo via
incorporation of star-shaped poly(˪-lysine) polypeptides (star-PLLs) and
a plasmid DNA (pDNA) cargo. Two star-PLL vectors with varying number
and length of poly(˪-lysine) arms were assessed. In vitro, the
functionalization of a range of collagen based scaffolds containing
either glycosaminoglycans (chondroitin sulfate or hyaluronic acid) or
ceramics (hydroxyapatite or nano-hydroxyapatite) with star-PLL-pDNA
nanomedicines facilitated prolonged, non-toxic transgene expression by
mesenchymal stem cells (MSCs). We demonstrate that the star-PLL
structure confers enhanced spatiotemporal control of nanomedicine
release from functionalized scaffolds over a 28-day period compared to
naked pDNA. Furthermore, we identify a star-PLL composition with 64
poly(˪-lysine) arms and 5 (˪-lysine) subunits per arm as a particularly
effective vector, capable of facilitating a 2-fold increase in reporter
transgene expression compared to the widely used vector polyethylenimine
(PEI), a 44-fold increase compared to a 32 poly(˪-lysine) armed
star-PLL and a 130-fold increase compared to its linear analogue, linear
poly(˪-lysine) (L-PLL) from a collagen-chondroitin sulfate gene
activated scaffold. In an in vivo subcutaneous implant model,
star-PLL-pDNA gene activated scaffolds which were implanted cell-free
exhibited extensive infiltration of autologous host cells, nanomedicine
retention within the implanted construct and successful host cell
transfection at the very early time point of just seven days. Overall,
this article illustrates for the first time the significant ability of
the star-PLL polymeric structure to transfect autologous host cells in
vivo from an implanted biomaterial scaffold thereby forming a versatile
platform with potential in numerous tissue engineering applications.
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Published Citation
Walsh DP, Raftery RM, Castano IM, Murphy R, Cavanagh B, Heise A, O’Brien FJ, Cryan SA. Transfection of autologous host cells in vivo using gene activated collagen scaffolds incorporating star-polypeptides. Journal of Controlled Release. 2019;304:191-203