Biodegradable electrospun poly(ε-caprolactone) (PCL) scaffolds were coated with platelet-rich plasma (PRP) to improve cell adhesion and proliferation. PRP was obtained from human buffy coat, and tested on human adipose-derived mesenchymal stem cells (MSC) to confirm cell proliferation and cytocompatibility. Then, PRP was adsorbed on the PCL scaffolds via lyophilization, which resulted in uniform sponge-like coating of 2.85 (s.d. 0.14) mg/mg. The scaffolds were evaluated regarding mechanical properties (Young’s modulus, tensile stress and tensile strain), sustained release of total protein and growth factors (PDGF-BB, TGF-β1 and VEGF), and hemocompatibility. MSC seeded on the PRP-PCL nanofibers showed an increased adhesion and proliferation compared to pristine PCL fibers. Moreover, the adsorbed PRP enabled angiogenesis features observed as neovascularization in a chicken chorioallantoic membrane (CAM) model. Overall, these results suggest that PRP-PCL scaffolds hold promise for tissue regeneration applications.
In situ gelling solutions for minimally invasive local application of bone growth factors are attracting increasing attention as efficient and patient-friendly alternative to bone grafts and solid scaffolds for repairing bone defects. Poloxamines, i.e., X-shaped poly(ethylene oxide)-poly(propylene oxide) block copolymers with an ethylenediamine core (Tetronic ® ), were evaluated both as an active osteogenic component and as a vehicle for rhBMP-2 injectable implants. After cytotoxicity screening of various poloxamine varieties, Tetronic 908, 1107, 1301 and 1307 solutions were chosen as the most cytocompatible and their sol-to-gel transitions were rheologically characterized. Viscoelastic gels, formed at 37 ºC, sustained protein release under physiological-like conditions. Formulations of rhBMP-2 led to differentiation of mesenchymal stem cells to osteoblasts, quantifi ed as alkaline phosphatase activity with a maximum at day 7, and to mineralized nodules. Interestingly, poloxamine solely gels led to an initial proliferation of the mesenchymal stem cells (fi rst week), followed by differentiation to osteoblasts (second to third week). Histochemical analysis revealed that Tetronic 908 is only osteoinductive; Tetronic 1107 is mostly osteoinductive, although its use leads to a minor differentiation to adipocytes; Tetronic 1307, solely or loaded with rhBMP-2, causes differentiation of both osteoblasts and adipocytes. Enhanced expression levels of CBFA-1 and collagen type I were observed for Tetronic 908, 1107 and 1307, both solely and combined with rhBMP-2. The intrinsic osteogenic activity of poloxamines (not observed for Pluronic F127) offers novel perspectives for bone regeneration using minimally invasive procedures (i.e., injectable scaffolds) and overcoming the safety and the cost/ effectiveness concerns associated with large scale clinical use of recombinant growth factors.
Conjugates of linear and branched polyethyleneimine (PEI) and monoamine polyether Jeffamine M-2070 (PO/EO mol ratio 10/31, 2000 Da) were synthesized through polyether activation by cyanuric chloride followed by attachment to PEI and guanidinylation by 1H-pyrazole-carboxamidine hydrochloride. The resulting guanidinylated PEI-polyether conjugates (termed gPEI-Jeffamine) efficiently complexed plasmid DNA, and their polyplexes possessed enhanced colloidal stability in the presence of serum proteins. In vitro studies with mammalian CHO-1, 3T3, and Cos-7 cell lines demonstrated improved transfection efficiency of the pCMVbeta-gal plasmid/gPEI-Jeffamine polyplexes. The guanidinylation of the amino groups of PEI and the conjugation of PEI with the Jeffamine polyether enhanced the conjugates' interaction with genetic material and reduced the cytotoxicity of the polyplexes in experiments with the L929 cell line.
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