Cues from the material to which a cell is adherent (e.g., adhesion ligand presentation, substrate elastic modulus) clearly influence the phenotype of differentiated cells. However, it is currently unclear if stem cells respond similarly to these cues. This study examined how the overall density and nanoscale organization of a model cell adhesion ligand (arginine-glycine-aspartic acid [RGD] containing peptide) presented from hydrogels of varying stiffness regulated the proliferation of a clonally derived stem cell line (D1 cells) and preosteoblasts (MC3T3-E1). While the growth rate of MC3T3-E1 preosteoblasts was responsive to nanoscale RGD ligand organization and substrate stiffness, the D1 stem cells were less sensitive to these cues in their uncommitted state. However, once the D1 cells were differentiated towards the osteoblast lineage, they became more responsive to these signals. These results demonstrate that the cell response to material cues is dependent on the stage of cell commitment or differentiation, and these findings will likely impact the design of biomaterials for tissue regeneration.

REDOX responsive (nano)materials typically exhibit chemical changes in response to the presence and concentration of oxidants/reductants. Due to the complexity of biological environments, it is critical to ascertain whether the chemical response may depend on the chemical details of the stimulus, in addition to its REDOX potential, and whether chemically different responses can determine a different overall performance of the material. Here, we have used oxidation-sensitive materials, although these considerations can be extended also to reducible ones. In particular, we have used poly(propylene sulfide) (PPS) nanoparticles coated with a PEGylated emulsifier (Pluronic F127); inter alia, we here present also an improved preparative method. The nanoparticles were exposed to two Reactive Oxygen Species (ROS) typically encountered in inflammatory reactions, hydrogen peroxide (H 2 O 2) and hypochlorite (ClO À); their response was evaluated with a variety of techniques, including diffusion NMR spectroscopy that allowed to separately characterize the chemically different colloidal species produced. The two oxidants triggered a different chemical response: H 2 O 2 converted sulfides to sulfoxides, while ClO À partially oxidized them further to sulfones. The different chemistry correlated to a different material response: H 2 O 2 increased the polarity of the nanoparticles, causing them to swell in water and to release the surface PEGylated emulsifier; the uncoated oxidized particles still exhibited very low toxicity. On the contrary, ClO À rapidly converted the nanoparticles into water-soluble, depolymerized fragments with a significantly higher toxicity. The take-home message is that it is more correct to discuss 'smart' materials in terms of an environmentally specific response to (REDOX) stimuli. Far from being a problem, this could open the way to more sophisticated and precisely targeted applications.

Poly(propylene sulfide) (PPS) is studied as an oxidation‐responsive macromolecular building block, in the perspective of anti‐inflammatory therapies. Here, we show that the nature of the oxidant has profound effects on the outcome of the oxidation process. PPS was exposed to hydrogen peroxide (H2O2) and hypochlorite (OCl−), which are oxidizing species commonly encountered during inflammatory processes. It was found that the oxidation with H2O2 converted thioethers into sulfoxides, producing water‐soluble macromolecular products with extremely low toxicity (L929 fibroblasts); on the contrary, the reaction with NaOCl produced sulfones in addition to sulfoxides, and this was accompanied by depolymerization, which appears to considerably affect the toxicity of the oxidation products.

Alzheimer's disease, among other pathological features, is characterized by an over-accumulation of amyloid-beta peptide, metal ions, and oxidative stress proteins in the brain. Amyloid-beta aggregated peptides with bound metal ions may initiate free radical generation with consequent protein and lipid oxidation, reactive oxygen species formation and eventually neuronal death. Melatonin is able to dramatically reduce the free radical formation which follows the interaction between transition metal ions and amyloid-beta. This paper reports the scavenging effect of melatonin of reactants generated by amyloid peptides in combination with some metal ions.

A large variety of natural and synthetic polymers have been explored as scaffolds for the seeding and growth of different types of cells. To fabricate a scaffold that can be used as a synthetic extracellular matrix (ECM), it is important to replicate the nanoscale dimensions of natural ECM. The electrospinning process allows to produce ultrathin fibers so that this method represents a suitable approach to scaffold fabrication for tissue engineering applications. In this work, the feasibility of obtaining flat or tubular matrices from biocompatible poly[(ethyl phenylalanato)(1.4) (ethyl glycinato)(0.6) phosphazene] by electrospinning was evaluated and the effect of process parameters on the diameter of nanofibers was examined. The adhesion and growth of rat neuromicrovascular endothelial cells cultured on sheets and tubes composed by the polymer with an average fiber diameter of 850 +/- 150 nm were also reported. Microscopic examination of the seeded tubes demonstrated that, after 16 days of incubation, endothelial cells formed a monolayer on the whole surface. These results are the first step to demonstrate that tubes of biodegradable polyphosphazenes might be a feasible model to construct human tissues such as vessels or cardiac valves.

Polyphosphazenes with amino acid ester as side groups are biocompatible polymers that could provide valid scaffolds for cell growth. In the present study we investigate the adhesion and growth of osteoblasts obtained from rat bone marrow on matrices composed of thin fibers of poly[bis(ethyl alanato)phosphazene] (PAlaP), poly(d,l-lactic acid) (PDLLA), or PAlaP/PDLLA blend. Our data show that scaffolds of PAlaP or PAlaP/PDLLA blend enhanced the cell adhesion and growth in comparison with that observed in cultures seeded on polystyrene tissue culture plates. Although collagenase-digestible protein synthesis remained unchanged, all scaffolds induced a decrease in alkaline phosphatase activity, suggesting that osteoblasts are in the proliferation phase. Both PAlaP and PAlaP blended with PDLLA may represent a new and interesting substrate for bone tissue engineering.

Melatonin is an efficient protector against hydrogen peroxide(H2O2)-induced lipid peroxidation and acts in a concentration-dependent manner. Hydrogen peroxide is rather a water stable molecule which is able to cross the cell membrane much better than some important free radicals such as superoxide anion, and consequently its local production can lead to significant spread by diffusion. In this paper we report data regarding some biochemical properties of melatonin as well as the chemical characterization of the major product formed from the interaction between melatonin and H2O2 (N1-acetyl-N2-formyl-5-methoxykynuramine) that are consistent with previous data reported by other authors. The effect of melatonin on catalase, glutathione peroxidase and superoxide dismutase in in vitro and in vivo experiments is also reported

The absorbance at 260 nm (A(260)) is ubiquitously used for nucleic acid quantification. We show that following oxygenation, DNA solutions experience alterations in both spectral properties (hyperchromism in the UV region, lambda(max) 260 nm) and DNA conformation. The spectral changes caused by oxygen-DNA complexation are stable for at least several weeks at room temperature or several hours at 37 degrees C, but are also reversible by purging with nitrogen. Our data indicate that DNA in working solutions might already exist in the oxygen-complexed state, potentially confounding spectrophotometric analyses. Further, the presence of these complexes does not appear to impart cell toxicity in vitro or affect the biophysical functional behaviour (e.g. hybridisation) of DNA. Interestingly, our work also suggests that hybridisation could determine a release of bound oxygen, a phenomenon that could open the way to the use of such systems as oxygen carriers.