Specific Binding and Mineralization of Calcified Surfaces by Small Peptides

Several small (<25aa) peptides have been designed based on the sequence of the dentin phosphoprotein, one of the major noncollagenous proteins thought to be involved in the mineralization of the dentin extracellular matrix during tooth development. These peptides, consisting of multiple repeats of the tripeptide aspartate-serine-serine (DSS), bind with high affinity to calcium phosphate compounds and, when immobilized, can recruit calcium phosphate to peptide-derivatized polystyrene beads or to demineralized human dentin surfaces. The affinity of binding to hydroxyapatite surfaces increases with the number of (DSS)n repeats, and though similar repeated sequences—(NTT)n, (DTT)n, (ETT)n, (NSS)n, (ESS)n, (DAA)n, (ASS)n, and (NAA)n—also showed HA binding activity, it was generally not at the same level as the natural sequence. Binding of the (DSS)n peptides to sectioned human teeth was shown to be tissue-specific, with high levels of binding to the mantle dentin, lower levels of binding to the circumpulpal dentin, and little or no binding to healthy enamel. Phosphorylation of the serines of these peptides was found to affect the avidity, but not the affinity, of binding. The potential utility of these peptides in the detection of carious lesions, the delivery of therapeutic compounds to mineralized tissues, and the modulation of remineralization is discussed

Probing the perturbation of lecithin bilayers by unmodified C60 fullerenes using experimental methods and computational simulations

In this study, we aimed to use physicochemical and theoretical tools to understand fundamental problems of the interaction between lipid bilayers (Egg-PC liposomes) and unmodified C60 fullerenes. The morphology, the size, and the electrokinetic properties of plain and C60-loaded liposomes were investigated by means of atomic force microscopy, dynamic light scattering, and ?-potential studies, respectively. The incorporation of C60 molecules into the liposomes increases their size; however, there was no effect on their electrokinetic properties. Visualization studies revealed that the presence of C60 in the membranes induced distortion in vesicle morphology, resulting in nonspherical vesicles. To elucidate further the impact of C60 molecules on lipid bilayers, we assessed their miscibility by fluorescence spectroscopy measurements. Fluorescence measurements showed that the presence of C60 in liposomes causes a pronounced effect on the Nile red emission spectrum due to alterations to the packing of the lipid membrane. The release of vesicle-encapsulated calcein was used as a measure of the integrity of the liposomes. Plain liposomes were found to be more stable compared with C60-loaded (PC) liposomes, suggesting that C60 ruptures the liposome membrane. Toxicity studies of C60 in liposomes were carried out on cultured cells [rodent fibroblasts (3T3)] to assess further their toxicity. The results suggest that fullerene cytotoxic effect was reduced significantly after its incorporation into the liposomal bilayer after 24 h of incubation with the rodent fibroblasts (3T3). Finally, energy minimization studies were employed to underpin the experimental observations. The theoretical calculations show that low concentration of fullerene molecules present in the membrane had no effect on the membrane integrity; however, at high concentrations of fullerenes significant enlargement of the surface area is observed, supporting the experimental finding

pH-responsive polymeric nanoassemblies encapsulated into alginate beads: morphological characterization and swelling studies

The aim of this study is to design and develop novel hybrid pH-responsive hydrogels. For this purpose, new copolymers with different molecular weights and different content of the hydrophobic part are synthesized. The self-assembly behavior of PSMA-co-PDMAEMA copolymerswasstudiedin two different dispersion media (simulated gastric fluid-SGF, pH = 1.2 and simulated intestinal fluid-SIF, pH = 6.8) and in different concentrations. The physicochemical characteristics of the nano-assemblies were found to be dependent on the composition of the copolymer and the aqueous environment. Having a complete knowledge of the self-assembly behavior of the copolymers in aqueous media, the encapsulation of the PSMA-co-PDMAEMA 1/2 nano-assemblies into Alginate beads was achieved by following the protocol of the preparation of hydrogels. The Calcium:Alginate hydrogels were used as reference systems for comparison reasons. The size and the morphology of pure and mixed beads were found to be dependent on the composition of the block copolymer, as revealed from SEM images. The behavior of the mixed hydrogels was the same during the swelling studies, but the rate of the swelling and the amount of weight change were found to be additionally dependent on the composition of the polymeric guest. The hydration state of the polymeric chains plays a key role inthe swelling behavior of the mixed hydrogels. In conclusion, pH-responsive hybrid hydrogels were developed and their behavior and morphology are strongly dependent on the molecular characteristics of the polymeric guest. © 2018, Springer Science+Business Media B.V., part of Springer Nature