Abstract
Optimization of nanofiber (NF) surface properties is critical to achieve an adequate cellular response. Here, the impact of conjugation of biomimetic aspartic acid (ASP) and glutamic acid (GLU) templated peptides with poly(lactic-co-glycolic acid) (PLGA) electrospun NF on osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hMSCs) was evaluated. Cold atmospheric plasma (CAP) was used to functionalize the NF surface and thus to mediate the conjugation. The influence of the CAP treatment following with peptide conjugation to the NF surface was assessed using water contact angle measurements, Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS). The effect of CAP treatment on morphology of NF was also checked using Scanning Electron Microscopy (SEM). Both the hydrophilicity of NF and the number of the carboxyl (-COOH) groups on the surface increased with respect to CAP treatment. Results demonstrated that CAP treatment significantly enhanced peptide conjugation on the surface of NF. Osteogenic differentiation results indicated that conjugating of biomimetic ASP templated peptides sharply increased alkaline phosphatase (ALP) activity, calcium content, and expression of key osteogenic markers of collagen type I (Col-I), osteocalcin (OC), and osteopontin (OP) compared to GLU conjugated (GLU-pNF) and CAP treated NF (pNF). It was further depicted that ASP sequences are the major fragments that influence the mineralization and osteogenic differentiation in non-collagenous proteins of bone extracellular matrix.
Highlights
Synthetic polymers used for scaffolds in tissue engineering applications are Poly (L-lactic acid) (PLA or poly(L-lactic acid) (PLLA)), Poly(lactide-co-glycolide) (PLGA) and Polycaprolactone (PCL)
Our results were consistent with that of Chen et al who reported 40 s of cold atmospheric plasma (CAP) treatment did not change the morphology of poly(L-lactic acid) (PLLA) NF and drastically increased carboxyl groups on NF surface[39]
We found that application of CAP on the surface of NF increases hydrophilicity and the number of carboxylic groups, which could effectively enhance the binding sites for biomimetic glutamic acid (GLU) and ASP templated peptides
Summary
Synthetic polymers used for scaffolds in tissue engineering applications are Poly (L-lactic acid) (PLA or PLLA), Poly(lactide-co-glycolide) (PLGA) and Polycaprolactone (PCL). Improved hydrophilicity along with the presence of particular functional groups on the surface of electrospun NF plays an important role in cell adhesion, proliferation and migration[10,11]. Various techniques such as pulsed laser deposition, ion beam deposition, covalent immobilization, photochemical modification, and plasma treatment have been used to modify the surface chemistry to improve hydrophilicity and introduce functional groups that can serve as biological cues[12,13,14,15,16]. To the best of our knowledge, a comparative study that evaluates the effect of repeating sequences of ASP and GLU on osteogenic differentiation of hMSCs when used to modify the surface of synthetic NF has not been reported
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