An extract of polyphenols was obtained from organic red grape pomace, chemically analyzed, and used for functionalization of two bioactive glasses and porous hydroxyapatite. Functionalization is effective on hydroxyapatite and the bioactive glass with higher surface reactivity with a different grafting mechanism. Grafting does not inhibit redox and radical scavenging activity of polyphenols. The grafted polyphenols make a continuous layer with an almost complete surface coverage. Polyphenols are released with different kinetics according to the mechanism of grafting and maintain their redox activity. A homogeneous thin layer of polyphenols is still firmly grafted on both substrates after 28 days of soaking and it still maintains radical scavenging activity. The functionalized samples can be sterilized by gamma irradiation.
Chitosan is known for its specific antibacterial mechanism and biodegradability, while polyphenols are known for their antioxidant and anti-inflammatory properties: coupling these properties on a surface for bone contact, such as hydroxyapatite, is of great interest. The system developed here allows the combination of hydroxyapatite, chitosan, and polyphenol properties in the same multifunctional biomaterial in order to modulate the host response after implantation. Crosslinked chitosan is used in this research to create a stable coating on hydroxyapatite, and then it is functionalized for a smart release of the polyphenols. The release is higher in inflammatory conditions and lower in physiological conditions. The properties of the coated and functionalized samples are characterized on the as-prepared samples and after the samples are immersed (for 24 h) in solutions, which simulate the inflammatory and physiological conditions. Characterization is performed in order to confirm the presence of polyphenols grafted within the chitosan coating, the stability of grafting as a function of pH, the morphology of the coating and distribution of polyphenols on the surface, and the redox reactivity and radical scavenging activity of the functionalized coating. All the results are in line with previous results, which show a successful coating with chitosan and functionalization with polyphenols. Moreover, the polyphenols have a different release kinetics that is faster in a simulated inflammatory environment compared to that in the physiological environment. Even after the release tests, a fraction of polyphenols are still bound on the surface, maintaining the antioxidant and radical scavenging activity for a longer time. An electrostatic bond occurs between the negative-charged polar groups of polyphenols (carboxyls and/or phenols) and the positive amide groups of the chitosan coating, and the substitution of the crosslinker by the polyphenols occurs during the functionalization process.
The distribution and interaction of lipids determine the structure and function of the cellular membrane. Surface-enhanced Raman scattering (SERS) is used for selective molecular probing of the cell membrane of living fibroblast cells grown adherently on gold nanoisland substrates across their whole contact areas with the substrate, enabling mapping of the membrane's composition and interaction. From the SERS data, the localization and distribution of different lipids and their interactions, together with proteins in the outer cell membrane, are inferred. Interpretation of the spectra is mainly supported by comparison with the spectra of model liposomes composed of phosphatidylcholine, sphingomyelin, and cholesterol obtained on the same gold substrate. The interaction of the liposomes with the substrate differs from that with gold nanoparticles. The SERS maps indicate colocalization of ordered lipid domains with cholesterol in the living cells. They support the observation of ordered membrane regions of micrometer dimensions in the outer leaflet of the cell membrane that are rich in sphingomyelin. Moreover, the spectra of the living cells contain bands from the groups of the lipid heads, phosphate, choline, and ethanolamine, combined with those from membrane proteins, as indicated by signals assigned to prenyl attachment. Elucidating the composition and structure of lipid membranes in living cells can find application in many fields of research.
There is a growing demand for bioactive compounds derived from green extraction methods from the food and cosmetic industries. Pulsed electric field (PEF)-assisted extraction has been applied for numerous foods but few on macroalgae. The present study examines PEF as part of the extraction process of polyphenols and carbohydrates from the brown macroalga Alaria esculenta. The effect of PEF treatment (0, 720 pulses) and ethanol concentration (0%, 15%) on the extraction of bioactive compounds from Alaria esculenta was assessed. To determine the pigment yield a second extraction was conducted with 60% ethanol or fractionated coconut oil with or without lecithin. The PEF treated aqueous extract had the highest yield for phenolic (10.4 ± 3.7 mg GAE g−1 DW) and carbohydrate content (21.4 ± 1.8 mg GE g−1 DW) as well as ferric reducing activity power and DPPH radical scavenging activity. The 60% ethanol extracts had a higher fucoxanthin content (73 ± 14 mg (100 g)−1 FD pulp) than the oil (2.1 mg (100 g)−1 FD pulp) and oil with lecithin (17 mg (100 g)−1 FD pulp) extracts. We obtained crude aqueous and low ethanolic extracts containing bioactive that show antioxidant activities, with either low temperature or PEF treatment from dried blades of Alaria esculenta. PEF treatment did not influence the pigment extraction with oil or 60% ethanol.
Pulsed electric field (PEF) assisted extraction was used to produce crude aqueous extracts from the brown alga Laminaria digitata to explore different treatment conditions. The experiment was set up using a central composite design and fitted to a response surface model with three factors: biomass concentration (0.17–3.28% dry weight), number of pulses during PEF treatment (12–268 pulses) and the initial temperature of algae suspension (12–48 °C). The temperature change during treatment, the extraction yield, total polyphenol and total carbohydrate content were determined. During PEF treatment the temperature change ranged from − 1 to 13 °C. The yield of supernatant and extraction yield was 70 ± 15% and 15% ± 8%, respectively. The total polyphenol content was 4.0 ± 1.6 mg GAE (100 g)−1 DW and the total carbohydrate content was 2.6 ± 2.9 mg GE g−1 DW. The supernatant yield, polyphenol content and carbohydrate content were the highest for the lowest biomass concentration. The number of pulses during PEF treatment was positively correlated to the temperature change, whilst the initial temperature was negatively correlated to the temperature change. This study shows that PEF assisted extraction can be used for the extraction of valuable compounds from L. digitata without recourse to high heat or organic solvents.
