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In the last decades, silk fibroin and wool keratin have been considered functional materials for biomedical applications. In this study, fabrics containing silk fibers from Bombyx mori and Tussah silk fibers from Antheraea pernyi, as well as wool keratin fabrics, were grafted with phosmer CL and phosmer M (commercial names, i.e., methacrylate monomers containing phosphate groups in the molecular side chain) with different weight gains. Both phosmers were recently proposed as flame retarding agents, and their chemical composition suggested a possible application in bone tissue engineering. IR and Raman spectroscopy were used to disclose the possible structural changes induced by grafting and identify the most reactive amino acids towards the phosmers. The same techniques were used to investigate the nucleation of a calcium phosphate phase on the surface of the samples (i.e., bioactivity) after ageing in simulated body fluid (SBF). The phosmers were found to polymerize onto the biopolymers efficiently, and tyrosine and serine underwent phosphorylation (monitored through the strengthening of the Raman band at 1600 cm−1 and the weakening of the Raman band at 1400 cm−1, respectively). In grafted wool keratin, cysteic acid and other oxidation products of disulphide bridges were detected together with sulphated residues. Only slight conformational changes were observed upon grafting, generally towards an enrichment in ordered domains, suggesting that the amorphous regions were more prone to react (and, sometimes, degrade). All samples were shown to be bioactive, with a weight gain of up to 8%. The most bioactive samples contained the highest phosmers amounts, i.e., the highest amounts of phosphate nucleating sites. The sulphate/sulphonate groups present in grafted wool samples appeared to increase bioactivity, as shown by the five-fold increase of the IR phosphate band at 1040 cm−1.

In knee replacements, vitamin E-doped ultra-high molecular weight polyethylene (UHMWPE) shows a better wear behavior than standard UHMWPE. Therefore, different sets of polyethylene (PE) acetabular cups, i.e. standard UHMWPE and cross-linked polyethylene irradiated with 50 kGy and 75 kGy, were compared, at a molecular level, with vitamin E-doped UHMWPE to evaluate their wear performance after being tested on a hip joint simulator for five million cycles. Unworn control and worn acetabular cups were analyzed by micro-Raman spectroscopy to gain insight into the effects of wear on the microstructure and phase composition of PE. Macroscopic wear was evaluated through mass loss measurements. The data showed that the samples could be divided into two groups: 1) standard and vitamin E-doped cups (mass loss of about 100 mg) and 2) the cross-linked cups (mass loss of about 30-40 mg). Micro-Raman spectroscopy disclosed different wear mechanisms in the four sets of acetabular cups, which were related to surface topography data. The vitamin E-doped samples did not show a better wear behavior than the cross-linked ones in terms of either mass loss or morphology changes. However, they showed lower variation at the morphological level (lower changes in phase composition) than the UHMWPE cups, thus confirming a certain protecting role of vitamin E against microstructural changes induced by wear testing.

Brown human hair was bleached three times (45 min × 3) and four times (45 min × 3 + 15 min) with commercial formulations containing persulfate salts and hydrogen peroxide. The hair samples were characterized by Raman and IR spectroscopy in the Attenuated Total Reflectance (ATR) mode to gain more insights into the possible secondary structure and Cα-Cβ-S-S-Cβ-Cα conformational changes induced by bleaching. The latter were evaluated through band-fitting procedures; the relative content of the disulfide bridges and oxidized sulfur species (cysteic acid, Bunte salt, cystine oxides) was assessed. The observed conformational changes could be significant in developing restoring agents to be used after hair decoloration. The use of two different spectroscopic techniques allowed to discriminate the information coming from the cortical region of hair (Raman) and the cuticle (ATR/IR). This article refers to “Structural investigation on damaged hair keratin treated with α,β-unsaturated Michael acceptors used as repairing agents” (Di Foggia et al., Int. J. Biol. Macromol. 167 (2021) 620–632 https://doi.org/10.1016/j.ijbiomac.2020.11.194 ).

Five alternating polar/non-polar peptides derived from the self-assembling peptide EAK-16 (AEAEAKAK)2 were examined in comparison with the EAK-16 parent form (pept1). The peptides were studied for their possible use as biomimetic materials due to their auto-assembling properties and to the presence, in two of them, of the RGD sequence, an active modulator of cell adhesion. The use of SERS allows the detection of peptides at very low concentrations (10-5-10-6 M), a feature of extreme interest to check their presence in the aqueous environment surrounding a metal implant and to study the effects of systematic amino acid substitution along the peptide chain on the corresponding interaction with the Ag colloidal nanoparticles. Quantum-mechanical data on two of the examined peptides were carried out and were very useful for clarifying the bands assignment debated in the literature. The results indicate that, in general, the peptide-nanoparticle interaction takes place through the carboxylate groups. The SERS spectrum displays an enhancement of the bands attributed to carboxylate vibrations, indicating that these groups directly interact with the nanoparticles. The most prominent band of carboxylate groups appears at 1393 cm-1 (symmetrical COO- stretching), intensified and red shifted of about 10 cm-1, as compared to the FT-Raman spectrum. This effect can be attributed to the proximity of the COO- group to the surface and to a charge transfer mechanism. Moreover, other bands can be attributed to COO- vibrations: 909 cm-1 (C-COO- stretching), 655 cm-1 (COO- bending) and 563 cm-1 (COO- wagging). The theoretical calculations pointed out that the last two bands are mixed with amide motions. As regards the other examined peptides, the spacer substitution in the sequence is a factor able to affect the peptide-Ag particles interaction: the increase in the hydrophobic chain length (Ala substituted by 2-aminobutanoic acid) favors the interaction by NH3+ groups, although the charge transfer interaction with the COO- ions is still the main interaction with the colloid. In fact, the presence of many SERS bands attributable to the NH3+ moieties of the Lys amino acid side chains, indicates the existence of interactions between the NH3+ groups and the nanoparticles, mediated by the Cl- anions present in the colloidal solution. The substitution of Ala with an aromatic Tyr residue strongly affects the interaction mechanism: the Tyr residue lies in a position close to perpendicular to the silver surface, partly as tyrosinate ion.

Ibuprofen (IbuH), 2-(4-isobutylphenyl) propionic acid, is a well-known nonsteroidal anti-inflammatory drug and is a promising antiatherosclerotic agent. Since IbuH has demonstrated to affect cell membranes structure, the study of the interaction between the membrane components, like phospholipids, and the drug, is of paramount interest. Moreover, liposomes can be used as drug carriers. In this paper, the effect of increasing amounts of Ibuprofen at neutral and acidic pH on the behaviour of dimyristoylphosphatidylcholine (DMPC) liposomes was investigated by means of Raman and differential scanning calorimetry (DSC) techniques. The results showed that pH influenced noticeably the liposome structure. A simple ‘solution-like’ model can explain the system when small or high IbuH or IbuNa (IbuH sodium salt forming at neutral and basic pH) amounts are present (IbuH/DMPC molar ratio ≤1/8.3 or ≥1/2.2 or IbuNa/DMPC molar ratio ≤1/17.5 or ≥1/4), whereas at intermediate amounts, two DSC peaks appeared: these systems could be described as a mixture of ‘phase II’ domains inserted within a structure of smaller and further ramified ‘phase I’ domains. Both DSC and Raman data suggested IbuH can penetrate within the apolar bilayer at pH 3, while at pH 7, the setting up of polar interactions of different strength between the carboxylic groups of IbuNa and the choline head of the DMPC, hamper a further penetration of the drug. Similar results were obtained both inserting directly IbuH molecules into liposomes as well as acidifying IbuNa water solutions, suggesting a possible use of liposomes as drug carriers when polarity is pH dependent.

Ibuprofen is one of the most widely used non-steroidal anti-inflammatory drugs (NSAIDs), in which the carboxylate group is available for metal ligand interactions. The most stable geometries for ibuprofen (in both its protonated and deprotonated forms) were identified by optimizations obtained by the unrestricted Density Functional Theory (DFT). Theoretical study of ibuprofen interacting with Ag colloid in solution, led to two (for the protonated form) and three (for the deprotonated form) different optimized geometries, corresponding to different interaction sites of the Ag-2 cluster. Frequency calculations were performed in the limit of the harmonic approximation, using the aug-cc-pVDZ basis set. Interpretation of the theoretical Raman spectra was performed by the Potential Energy Distribution (PED) analysis of the fundamental vibrations modes. Raman study on the solid Ibuprofen-metal complexes confirmed that Co2+ gives monodentate complexes, while Zn2+ adopts a bidentate coordination. SERS spectra of metal complexes, suggested that at ppm concentration, the formation of stable 2:1 metal complexes is excluded, while is more probable the formation of 1:1 adduct with bidentate binding on the carboxylic group. The metal reaches its total coordination shell by complexation of water molecules. (C) 2014 Elsevier B.V. All rights reserved.

BACKGROUND: Metal ions are implicated in protein aggregation processes of several neurodegenerative pathologies, where the protein deposition occurs, and in the biotechnology field like the food technology where many processes in food manufacturing are based on thermal treatments. OBJECTIVE: The influence of Cu2+ or Zn2+ ions on the thermal aggregation process of Bovine beta-lactoglobulin (BLG) and Bovine Serum Albumin (BSA), two protein models, was studied with the aim of delineating the role of these ions in the protein aggregation kinetics and to clarify the related molecular mechanisms. METHODS: The protein structure changes were monitored by Raman spectroscopy, whereas the aggregate growth was followed by Dynamic Light Scattering measurements. RESULTS: Both metal ions are able to favour the BLG aggregation, whereas only Zn2+ ions have a promoter effect on the thermal aggregation of BSA. The reason of this different behaviour is that the BLG aggregation evolution is manly affected by the redistribution of charges, whereas that of BSA by the metal coordination binding which depends on metal. CONCLUSIONS: Raman spectroscopy, combined with dynamic light scattering experiments, was very useful in identifying the role played by Cu2+ and Zn2+ on the aggregation pathways of BLG and BSA. The results provide evidence for the role of histidine residues both in the redistribution of charges and in the two modes of metal binding that take place in BLG- and BSA-containing systems, respectively.

Molecular basis of the role played by Cu 2 + and Zn 2 + ions during the thermal aggregation processes of beta-lactoglobulin (BLG) was studied by using a joint application of different techniques. In particular, Raman spectroscopy was very useful in identifying the different effects caused by the two metals at molecular level (i.e. changes in His protonation state, disulfides bridge conformation, and micro-environment of aromatic residues), evidencing the primary importance of the protein charge distribution during the aggregation process. Both metal ions are able to act on this factor and favor the protein aggregation, but Zn 2 + is able to alter the natural conformational state of BLG, causing a slight unfolding, whereas Cu 2 + ions play a role only during the thermal treatment. Thus, Zn 2 + ions favor the formation of bigger aggregates and branched fibril-like structures, whereas for Cu 2 + ions a greater number of cross-beta structures during thermal incubation and finally, fibrillar structures. The aggregation process occurs in two phases, as suggested by the measurements on the time evolution of the BLG aggregates: the first one is characterized by a partial unfolding of the protein and aggregate growth, forming oligomers and protofibrils, whereas the second one is characterized by further supramolecular assembly, leading to the formation of fibrils.