Biofabrication is a popular technique to produce personalized constructs for tissue engineering. In this study we combined laponite (Lap), gellan gum (GG) with platelet-rich plasma (PRP) aiming to enhance the endothelial regeneration through the synergistic effects of their individual properties. Laponite has the ability to form porous three-dimensional networks mimicking the extracellular matrix structure, and PRP delivery of growth factors stimulates the endothelial cell proliferation and migration, offering a composite bioink for cell growth and support. The sustained release of these growth factors from the GG-laponite-PRP composite material over time provides a continuous source of stimulation for the cells, leading to more effective tissue engineering strategies for endothelial tissue regeneration. Four blend compositions comprising 1% w/v GG and 0.5 or 1% w/v Lap and 25% v/v PRP were combined with Wharton jelly mesenchymal stem cells (WJ-MSCs) and bioprinted into vessel-like structures with an inner diameter of 3 mm and a wall thickness of 1 mm. Stress/strain analysis revealed the elastomeric properties of the hydrogels with Young modulus values of 10 MPa. Increasing the Lap concentration led to a non-significant decrease of swelling ratio from 93 to 91%. Live/dead assay revealed cell viability of at least 76%, with the 0.5%Lap-GG viability exceeding 99% on day 21. Gradual increase of glycosaminoglycans accumulation and collagen production indicate promotion of ECM formation. The expression and membranous localization of PECAM-1 from day 7 and the granular intracellular localization of vWF after 2 weeks demonstrate in vitro endothelial functionality. In vivo subcutaneous implantation indicated the absence of any adverse immunological reactions. The results reveal the expression of both vWF and PECAM-1 by WJ-MSCs entrapped in all four construct compositions with significantly higher expression of vWF in the presence of PRP.

Bone is a dynamic tissue that undergoes continuous mechanical forces. Mechanical stimuli applied on scaffolds resembling a part of the human bone tissue affects the osteogenesis [1]. Poly(3,4-ethylenedioxythiophene) (PEDOT) is a piezoelectric material that responds to mechanical stimulation producing an electrical signal, which in turn promotes the osteogenic differentiation of bone-forming cells by opening voltage-gated calcium channels [2]. In this study we examined the biological behavior of pre-osteoblastic cells seeded onto lyophilized piezoelectric PEDOT-containing scaffolds applying uniaxial compression.

Two different concentrations of PEDOT (0.10 and 0.15% w/v) were combined with a 5% w/v poly(vinyl alcohol) (PVA) and 5% w/v gelatin, casted into wells, freeze dried and crosslinked with 2% v/v (3-glycidyloxypropyl)trimethoxysilane and 0.025% w/v glutaraldehyde. The scaffolds were physicochemically characterized by FTIR, measurement of the elastic modulus, swelling ratio and degradation rate. The cell-loaded scaffolds were subjected to uniaxial compression with a frequency of 1 Hz and a strain of 10% for 1 h every second day for 21 days. The loading parameters were selected to resemble the in vivo loading situation [3]. Cell viability and morphology on the PEDOT/PVA/gelatin scaffolds was determined. The alkaline phosphatase (ALP) activity, the collagen and calcium production were determined.

The elastic modulus of PEDOT/PVA/gelatin scaffolds ranged between 1 and 5 MPa. The degradation rate indicates a mass loss of 15% after 21 days. The cell viability assessment displays excellent biocompatibility, while SEM images display well-spread cells. The ALP activity at days 3, 7 and 18 as well as the calcium production are higher in the dynamic culture compared to the static one. Moreover, energy dispersive spectroscopy analysis revealed the presence of calcium phosphate in the extracellular matrix after 14 days. The results demonstrate that PEDOT/PVA/gelatin scaffolds promote the adhesion, proliferation, and osteogenic differentiation of pre-osteoblastic cells under mechanical stimulation, thus favoring bone regeneration.

The development of functional biomaterials scaffolds for bone tissue engineering applications includes the control of specific biological and mechanical parameters that are involved in the growth of bone tissue in a way that mimics the physiological process of healing bone defects. Here, we report on the development of composite scaffolds made from biodegradable natural and synthetic biomaterials with characteristic architectural features, functionalized with the osteoinductive growth factor bone morphogenetic protein BMP-2, and evaluating their osteogenic response in static and dynamic cell culture systems. The results show that scaffold designing with advanced technologies combined with appropriate biochemical and mechanical stimulating factors, results to an enhanced proliferative and osteogenic/chondrogenic differentiation response of cells cultured on the developed scaffolds, and thus controlling the new tissue formation and reconstruction.