Biological Designer Self-Assembling Peptide Nanofiber Scaffolds Significantly Enhance Osteoblast Proliferation, Differentiation and 3-D Migration

A class of self-assembling peptide nanofiber scaffolds has been shown to be an excellent biological material for 3-dimension cell culture and stimulating cell migration into the scaffold, as well as for repairing tissue defects in animals. We report here the development of several peptide nanofiber scaffolds designed specifically for osteoblasts. We designed one of the pure self-assembling peptide scaffolds RADA16-I through direct coupling to short biologically active motifs. The motifs included osteogenic growth peptide ALK (ALKRQGRTLYGF) bone-cell secreted-signal peptide, osteopontin cell adhesion motif DGR (DGRGDSVAYG) and 2-unit RGD binding sequence PGR (PRGDSGYRGDS). We made the new peptide scaffolds by mixing the pure RAD16 and designer-peptide solutions, and we examined the molecular integration of the mixed nanofiber scaffolds using AFM. Compared to pure RAD16 scaffold, we found that these designer peptide scaffolds significantly promoted mouse pre-osteoblast MC3T3-E1 cell proliferation. Moreover, alkaline phosphatase (ALP) activity and osteocalcin secretion, which are early and late markers for osteoblastic differentiation, were also significantly increased. We demonstrated that the designer, self-assembling peptide scaffolds promoted the proliferation and osteogenic differentiation of MC3T3-E1. Under the identical culture medium condition, confocal images unequivocally demonstrated that the designer PRG peptide scaffold stimulated cell migration into the 3-D scaffold. Our results suggest that these designer peptide scaffolds may be very useful for promoting bone tissue regeneration

The role of peptides in bone healing and regeneration: A systematic review

Background: Bone tissue engineering and the research surrounding peptides has expanded significantly over the last few decades. Several peptides have been shown to support and stimulate the bone healing response and have been proposed as therapeutic vehicles for clinical use. The aim of this comprehensive review is to present the clinical and experimental studies analysing the potential role of peptides for bone healing and bone regeneration. Methods: A systematic review according to PRISMA guidelines was conducted. Articles presenting peptides capable of exerting an upregulatory effect on osteoprogenitor cells and bone healing were included in the study. Results: Based on the available literature, a significant amount of experimental in vitro and in vivo evidence exists. Several peptides were found to upregulate the bone healing response in experimental models and could act as potential candidates for future clinical applications. However, from the available peptides that reached the level of clinical trials, the presented results are limited. Conclusion: Further research is desirable to shed more light into the processes governing the osteoprogenitor cellular responses. With further advances in the field of biomimetic materials and scaffolds, new treatment modalities for bone repair will emerge

Dynamic force spectroscopy to probe adhesion strength of living cells

We studied the mechanical strength of the adhesion of living cells to model membranes. The latter contained a RGD lipopeptide which is a high affinity binding site for a cell adhesion molecule (integrin alpha(V)beta(3)). Cells adhered specifically to the vesicles. We used micropipette aspiration for breaking this adhesion with well defined forces. Systematic variation of the rate of force application revealed pronounced kinetic effects. The dependence of the detachment forces on the loading rate was well described by a power law (exponent approximate to0.4), in agreement with recent theoretical work

FRIES REARRANGEMENT OF ARYL FORMATES PROMOTED BY BCL3. MECHANISTIC EVIDENCE FROM 11B NMR SPECTRA AND DFT CALCULATIONS

The Fries rearrangement of model aryl formate esters, promoted by boron trichloride, has been investigated by means of NMR spectroscopy (both experimental and computational) and by DFT calculations. Firstly, the B-11 NMR chemical shifts of a series of model boron compounds have been predicted by GIAO-B3LYP/6-31G(d,p) calculations, in order to make predictions of the chemical shifts of transient reaction intermediates observable by B-11 NMR. Such B-11 spectra for the reaction of two esters (phenyl and 3-methyoxyphenyl formates) have been obtained, and are found to follow different patterns which can be rationalized on the basis of computed chemical shifts. Secondly, DFT calculations (B3LYP/6-31G(d,p) level) have been employed to investigate several mechanistic pathways of the rearrangement of phenyl formate. It is found that the pathways leading to the lowest activation energies are those in which formyl chloride is generated from a complex between phenyl formate and BCl3, which then acts as the formylating agent