Extracellular matrix mimetic materials in tissue engineering and regenerative medicine

Introduction: In the past few decades, biomimetic materials have extensively been investigated for the applicability in tissue engineering and regenerative medicine. Electrospinning is one of the most promising methods for generating extracellular matrix (ECM) mimetic porous nano/microfiber-based scaffolds or patches for such applications. Various active components such as therapeutic agents, nanoparticles and biomolecules can be incorporated to enhance mechanical stability, degradation, antimicrobial properties, vascularization potential and tissue regeneration capacity of electrospun fibers.

Methods: We used polymers such as polycaprolactone (PCL), polylactic acid (PLA), polyvinyl alcohol (PVA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) to develop ECM mimetic polymeric scaffolds by electrospinning. We incorporated metal oxide nanoparticles such as zinc oxide (ZnO), titanium dioxide (TiO₂) and cerium oxide (nCeO₂) in polymer fibers (0.5 to 6% w/w). We also incorporated growth factors such as epidermal growth factor (EGF), connective tissue growth factor (CTGF) and stromal cell-derived factor 1 (SDF-1) in the fibers to make them bioactive. The developed membranes were characterized by techniques such as Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) analysis and Fourier Transform Infrared Spectroscopy (FTIR). Tensile mechanical testing was carried out to understand the effect of nanoparticles or growth factors on the tensile strength of the fibers. In vitro cell culture studies using keratinocytes, fibroblasts and endothelial cells were performed. We also performed chicken chorioallantoic membrane (CAM) assay to understand the vascularization potential of the scaffolds. ECM mimetic scaffolds were applied on wounds generated on diabetic rats to evaluate the diabetic wound healing potential.

Results & Discussions:  SEM analysis indicated that the developed scaffolds and patches were highly porous with fiber diameters ranging from 200 to 1200 nm. FTIR and XRD analyses showed the presence of loaded active agents in the fibers. The tensile strength of nanocomposite scaffolds improved at a concentration less than 2% w/w nanomaterial loading. Higher cell attachment and proliferation was observed for nanocomposite and growth factor loaded scaffolds at an optimum loading of nanoparticles and growth factors. CAM assay and in vivo implantation of scaffolds indicated a higher angiogenesis especially when ZnO, TiO₂ and nCeO₂ nanoparticles were incorporated in the scaffolds (1–3). Growth factors such as EGF and CTGF loaded scaffolds also showed a higher angiogenesis response (4,5). When loaded in scaffolds or patches, several metal oxide nanoparticles such as ZnO and TiO₂ could promote wound healing in normal experimental animals. Antioxidant nanoparticles such as nCeO₂ or EGF loaded scaffolds and patches could support diabetic wound healing.

Conclusions:  ECM mimetic scaffolds incorporated with various metal oxide nanoparticles such as ZnO, TiO₂ and nCeO₂ as well as growth factors such as EGF, CTGF and SDF-1 can support cell proliferation, angiogenesis and wound healing.  

Key words: Electrospinning, nanoparticles, growth factors, cell proliferation, wound healing

Acknowledgement: This article was made possible by the NPRP12S-0310-190276 grant funded by Qatar National Research Fund (a part of Qatar Foundation). The statement made here are the sole responsibility of authors.

References

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