Abstract: Photoreactive and cytocompatible polymer nanoparticles for immobilizing and photoinduced releasing proteins were prepared. A water-soluble and amphiphilic phospholipid polymer, poly (2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate (BMA)-co-4-(4-(1-methacryloyloxyethyl)-2-methoxy-5-nitrophenoxy) butyric acid (PL)) (PMB-PL) was synthesized. The PMB-PL underwent a cleavage reaction at the PL unit by photoirradiation at a wavelength of 365 nm. Additionally, the PMB-PL took polymer aggregate in aqueous medium and was used to modify the surface of biodegradable poly (L-lactic acid) (PLA) nanoparticle as an emulsifier. The morphology of the PMB-PL/PLA nanoparticle was spherical and approximately 130 nm in diameter. The carboxylic acid group in the PL unit could be used for immobilization of proteins by covalent bonding. The bound proteins were released by a photoinduced cleavage reaction. Within 60 sec, up to 90% of the immobilized proteins were released by photoirradiation and activity of the protein released in the medium was maintained as well as that the original proteins before immobilization. Octa-arginine (R8) could promote internalization of the protein/PLA/PMB-PL nanoparticles into cells when the R8 was co-immobilized on the nanoparticles. After that, photoirradiation induced protein release from the nanoparticles and proteins distributed more evenly inside cells. From these results, we concluded that PMB-PL/PLA nanoparticles have the potential to be used as smart carriers to deliver proteins to biological systems, such as the inside of living cells.
Abstract: While considerable work has been done on chemically functionalizing hydroxyapatite, little has been done on tailoring the electrical surface potential. This has been due to limitations in the available methods to impart a surface charge. Work to date has charged conventionally manufactured hydroxyapatite exhibiting a random crystal orientation. At the outset, the microstructure has not been optimized for the highest surface potential. The aim of this work was to both orient the crystals as well as fill the structure with hydroxyl ions for further increasing the surface electrical potential. We used hydroxyapatite coatings with the same topography, but different hydroxyl ion concentration; this altered the surface potential that was measured by Kelvin probe AFM. Results indicate that a greater hydroxyl ion concentration increases the surface potential of the hydroxyapatite coating. Coatings with a higher surface potential showed improved biological response, measured as osteoblast attachment and osteoblast related gene expression.
Abstract: In this work, the nucleation of bioglasses particles was approached through Dynamic Light Scattering in order to analyze how different synthesis parameters influence on the particle growth. It was evaluated the following parameters: pH between 10 and 11; surfactant concentration (PEG) between 0 to 20g/L; Three different compositions were chosen based on the 47SiO2-(38 – x)Na2O-(9 + x)CaO-6P2O5 system ( x = 0, 10 and 20). For each experimental condition, the growth kinetics (Kc.t-1) was calculated, and the obtained values were analyzed by factorial design of experiments. The results evidence that higher pH, higher surfactant concentration and lower Na/Ca ionic ratio lead to lower values growth kinetics in which, in turn, are associated with lower particle size.
Abstract: Bacterial issues in ophthalmic applications, with particular reference to postoperative infection of ocular implants, cause significant problems that often require additional, stressful and expensive treatments for the patients. In this work we applied silver-containing antibacterial costings on two kinds of polymeric ocular devices, i.e. silicone scleral buckles for retinal detachment surgery and poly(methyl methacrylate) artificial eyes for enucleated patients. The coatings (thickness around 50 nm), constituted by silver nanoclusters embedded in a silica matrix, were produced by RF co-sputtering and investigated by SEM and EDS. The antibacterial effect of the coating was confirmed by the in vitro formation of an inhibition halo against Staphylococcus aureus, which is one of the most common pathogens involved in ocular infections. The approach proposed in this study for treating implant-related ocular infections can have a significant impact in the field of ophthalmic biomaterials, suggesting a valuable alternative to the administration of antibiotics that may become ineffective towards resistant bacterial strains.
Abstract: Structural organization of articular cartilage is rooted in the arrangement of mesenchymal stem cells (MSCs) into morphologically distinct zones during embryogenesis as a result of spatiotemporal gradients in biochemical, mechanical, and cellular factors that direct the formation of stratified structure of articular cartilage. These gradients are central to the function of cartilage as an articulating surface. Strategies that mimic zonal organization of articular cartilage are more likely to create an engineered tissue with more effective clinical outcome. The objective of this work was to measure the expression of human MSCs encapsulated in engineered gels that simulate stiffness of the superficial, middle and calcified zones of articular cartilage supplemented with zone specific growth factors. Size of the encapsulated cells increased from the gel simulating superficial zone to those simulating middle and calcified zones. Glycosaminoglycans (GAG) content progressively increased from the gel simulating superficial zone to those simulating middle and calcified zones. Human MSCs in the gel simulating the superficial zone showed up-regulation of Sox-9 and SZP whereas those in the calcified gel showed up-regulation of ALP. Results demonstrate that a developmental approach can potentially regenerate the zonal structure of articular cartilage.
Abstract: The effect of molecular mobility of the supramolecular surfaces on the intracellular signaling pathway and the downstream cell functions were investigated. As a supramolecular cell culture platform, polyrotaxanes (PRXs) with a varied number of threaded host molecules were synthesized and coated on glass surfaces. As a result, mesenchymal stem cells (MSCs) adhering on the dynamic PRX surface shows down-regulated RhoA-associated signaling pathway resulting in narrow and protruded adhering morphology. Moreover, mouse induced pluripotent stem (iPS) cells on the dynamic PRX surface shows highly up-regulated Rac1-associated signaling pathway resulting in enhanced N-cadherin expression and cardiomyogenic differentiations. Because MSCs and iPS cells on the polymer surfaces with low molecular mobility show the reverse tendency with those of the dynamic PRX surfaces, it could be concluded that the control of molecular mobility induced by supramolecular PRXs is effective to control cytoskeletal signaling pathway and the downstream stem cell differentiation into the preference cells or tissue.
Abstract: Porous silicon (PSi) with a suite of most desirable biomaterial properties has attracted great attention as a multifunctional nanoplatform for bioimaging and drug delivery. Various surface functionalization treatments have been reported for PSi to use as an active tumor cell targeting nanovector. In this study, we investigated surface functionalization treatments using a peptide that is specific to the emerging biomarker legumain. The PSi nanoparticles were coated with dextran and subsequently two types of legumain targeting peptide, Y-shaped and linear chain, were conjugated to produce the functionalized PSi. The functionalized (ligand-conjugated) PSi materials were characterized for morphology, size, functional groups, and fluorescence response using electron and fluorescence microscopy and vibrational spectroscopy techniques. Fluorescence microscopy imaging with two excitation wavelengths (450 nm and 600 nm) suggests comparable fluorescence response of the conjugated PSi to “bare” PSi and the suitability of the PSi functionalized with peptide for bioimaging.
Abstract: A protease-activated ratiometric fluorescent probe based on fluorescence resonance energy transfer between a pH-sensitive fluorescent dye and biocompatible Fe3O4 nanocrystals was constructed. A peptide substrate of MMP-9 served as a linker between the particle quencher and the chromophore that was covalently attached to the antitumor antibody. The optical response of the probe to activated MMP-9 and gastric cell line SGC7901 tumor cells was investigated, followed by in vivo tumor imaging. Based on the ratiometric pH response to the tumor microenvironment, the resulting probe was successfully used to image the pH of subcutaneous tumor xenografts.
Abstract: Sound velocities were measured in relaxor single-crystal plates, included in piezoelectric transducers for medical uses, using an ultrasonic precision thickness gauge with high-frequency pulse generation. The velocities were compared with the ones of piezoelectric ceramics in order to clarify characteristics of the single crystals. Estimating the difference in the sound velocities and elastic constants in the single crystals and ceramics, it was possible to evaluate effects of domain and grain boundaries on elastic constants. Existence of domain boundaries in single crystal affected the decrease in Young’s modulus, rigidity, Poisson’s ratio and bulk modulus. While existence of grain boundaries affected the decrease in Young’s modulus and rigidity, Poisson’s ratio and bulk modulus increased. It was thought these phinomina come from domain alignment by DC poling, and both the boundaries act as to absorb mechanical stress by defects due to the boundaries. In addition, the origin of piezoelectricity in single crystals is caused by low bulk modulus and Poisson’s ratio, and high Young’s modulus and rigidity in comparison with ceramics. On the contrary, the origin of piezoelectricity in ceramics is caused by high Poisson’s ratio by high bulk modulus, and furthermore, low Young’s modulus and rigidity due to domain alignment.