Mesoscopic Model for Reversible Adsorption Stage of Albumin and Fibrinogen on TiO2 Surface

The competitive behavior of proteins in the reversible adsorption stage plays a crucial role in determining the composition of the protein layer and the subsequent biological responses to the biomaterial. However, such competitive adsorption is a mesoscopic process at physiological protein concentration, and neither a macroscopic experiment nor microscopic MD (molecular dynamics) simulation is suitable to clarify it. Here, we proposed a mesoscopic DPD (dissipative particle dynamics) model to illustrate the competitive process of albumin and fibrinogen on TiO2 surface with its parameters deduced from our previous MD simulation, and proved the model well retained the diffusion and adsorption properties of proteins in the competitive adsorption on the plane surface. We then applied the model to the competitive adsorption on the surfaces with different nanostructures and observed that when the nanostructure size is much larger than that of protein, the increase in surface area is the main influencing factor; when the nanostructure size is close to that of protein, the coordination between the nanostructure and the size and shape of protein significantly affects the competitive adsorption process. The model has revealed many mechanical phenomena observed in previous experimental studies and has the potential to contribute to the development of high-performance biomaterials.

Biomedical Applications of Titanium Alloys: A Comprehensive Review

Titanium alloys have emerged as the most successful metallic material to ever be applied in the field of biomedical engineering. This comprehensive review covers the history of titanium in medicine, the properties of titanium and its alloys, the production technologies used to produce biomedical implants, and the most common uses for titanium and its alloys, ranging from orthopedic implants to dental prosthetics and cardiovascular devices. At the core of this success lies the combination of machinability, mechanical strength, biocompatibility, and corrosion resistance. This unique combination of useful traits has positioned titanium alloys as an indispensable material for biomedical engineering applications, enabling safer, more durable, and more efficient treatments for patients affected by various kinds of pathologies. This review takes an in-depth journey into the inherent properties that define titanium alloys and which of them are advantageous for biomedical use. It explores their production techniques and the fabrication methodologies that are utilized to machine them into their final shape. The biomedical applications of titanium alloys are then categorized and described in detail, focusing on which specific advantages titanium alloys are present when compared to other materials. This review not only captures the current state of the art, but also explores the future possibilities and limitations of titanium alloys applied in the biomedical field.

An efficient protocol for decellularization of the human endometrial fragments for clinical usage

The present study was aimed to compare different decellularization protocols for human endometrial fragments. The freeze-thaw cycles in combination with treatment by Triton X-100 and four concentrations of sodium dodecyl sulfate (SDS; 0.1, 0.5, 1, and 1.5%) with two exposure times (24 and 72 h) were applied for tissues decellularization. After analysis the morphology and DNA content of tissues the group with better morphology and lower DNA content was selected for further assessments. The nucleus by Acridine orange and extracellular matrix (ECM) using Masson's trichrome, Alcian blue, and periodic acid-Schiff staining were studied. The amount of tissues collagen types I and IV, fibronectin, glycosaminoglycans (GAGs), and elastin was analyzed by Raman spectroscopy. The ultrastructure and porosity of decellularized scaffold were studied by scanning electron microscopy (SEM). The MTT assay was applied for assessments of cytotoxicity of scaffold. The treated group with 1% SDS for 72 h showed the morphology similar to native control in having the minimum level of DNA and well preserved ECM. Raman spectroscopy results demonstrated, the amount of collagen types I and IV, GAG, and fibronectin was not significantly different in decellularized scaffold compared with native group but the elastin protein level was significantly decreased (P < 0.001). SEM micrographs also showed a porous and fiber rich ECM in decellularized sample similar to the native control. This combined protocol for decellularization of human endometrial tissue is effective and it could be suitable for recellularization and clinical applications in the future.

Thiol-Poly(Sodium Styrene Sulfonate) (PolyNaSS-SH) Gold Complexes: From a Chemical Design to a One-Step Synthesis of Hybrid Gold Nanoparticles and Their Interaction with Human Proteins

This study highlights recent advances in the synthesis of nanoconjugates based on gold (Au(III)) complex with a bioactive polymer bearing sulfonate groups called thiol-poly(sodium styrene sulfonate) (PolyNaSS-SH) with various molecular weights (5, 10, and 35 kDa). The three nanomaterials differ substantially in shape and structure. In particular, for PolyNaSS-SH of 35 kDa, we obtained a characteristic core-shell flower shape after chelation of the Au(III) ions and successively reduction with sodium borohydride (NaBH₄). The mechanism of formation of the hybrid nanoparticles (PolyNaSS-SH@AuNPs (35 kDa) and their interactions between plasmatic proteins (human serum albumin (HSA), collagen I (Col 1), and fibronectin (Fn)) were deeply studied from a chemical and physical point of view by using several analytical techniques such as Raman spectroscopy, UV-visible, transmission electron microscopy (TEM), ¹H NMR, and X-ray photoelectron spectroscopy (XPS).

Stored potential energy increases and elastic properties alterations are produced after restoring dentin with Zn-containing amalgams

The aim of this research was to ascertain the mechanical and chemical behavior of sound and caries-affected dentin (CAD), after the placement of Zn-free vs containing amalgam restorations. Peritubular and intertubular dentin were evaluated using, a) nanoindenter in scanning mode; the load and displacement responses were used to perform the nano-Dynamic mechanical analysis and to estimate the complex (E * ) and storage modulus (E'); b) Raman spectroscopy was used to describe the hierarchical cluster analysis (HCA). Assessments were performed before restoration placement and after restoring, and after 3 months of storage with thermocycling (100,000cy/5 °C and 55 °C). When CAD was treated with Zn-containing restorations, differences between E * and E' at both peritubular and intertubular dentin augmented, with energy concentration and production of implications in the mechanical performance of the restored teeth. E * and E' were very low at intratubular dentin of CAD restored with Zn-containing restorations. The relative presence of minerals, the phosphate crystallinity and the crosslinking of collagen increased their values at both types of dentin (peritubular and intertubular) when CAD was treated with Zn-containing restorations. The nature and secondary structure of collagen improved in CAD treated with Zn-containing amalgams. Different levels of dentin remineralization were revealed by hierarchical cluster analysis.

In vivo osteoconductivity of surface modified Ti-29Nb-13Ta-4.6Zr alloy with low dissolution of toxic trace elements

Simulated Body Fluid (SBF) has served as a useful standard to check the bioactivity of implant materials for years. However, it is not perfectly able to imitate human serum; sometimes disparities between the SBF test and animal test were confirmed. Therefore, to ensure the reliability of the results of the SBF test obtained from our previous study, an animal study was performed to check osteoconductivity of surface modified implant materials. Three types of solution processes, hydrothermal (H), electrochemical (E), and hydrothermal-electrochemical (HE), were performed on the Ti-29Nb-13Ta-4.6Zr alloy (TNTZ) to improve its bioactivity, and their bioactivities were measured in vivo using bone-implant contacts (BICs). BICs of the HE- and H-treated samples were significantly higher than that of the control. Metal ion diffusion towards the bone was also evaluated to examine the adverse effect of metal ions. No metal ion diffusion was observed, indicating the safety of our solution processed implant materials.

Functional engineered mesenchymal stem cells with fibronectin-gold composite coated catheters for vascular tissue regeneration

Vascularization of engineered tissues remains one of the key problems. Here, we described a novel approach to promote vascularization of engineered tissues using fibronectin (FN) incorporated gold nanoparticles (AuNP) coated onto catheters with mesenchymal stem cells (MSCs) for tissue engineering. We found that the FN-AuNP composite with 43.5 ppm of AuNP exhibited better biomechanical properties and thermal stability than pure FN. FN-AuNP composites promoted MSC proliferation and increased the biocompatibility. Mechanistically, vascular endothelial growth factor (VEGF) promoted MSC migration on FN-AuNP through the endothelial oxide synthase (eNOS)/metalloproteinase (MMP) signaling pathway. Vascular femoral artery tissues isolated from the implanted FN-AuNP-coated catheters with MSCs expressed substantial CD31 and alpha-smooth muscle actin (α-SMA), displayed higher antithrombotic activity, as well as better endothelialization ability than those coated with all other materials. These data suggested that the implantation of FN-AuNP-coated catheter with MSCs could be a novel strategy for vascular biomaterials applications.

Zinc oxide microrods and nanorods: different antibacterial activity and their mode of action against Gram-positive bacteria

ZnO micro and nanorods, produced through simple and inexpensive techniques, resulted to be strong antimicrobials against Gram-positive bacteria, in vitro as well as in vivo, by altering cell outer structures like membrane and exopolysaccharides.

Differential contributions of conformation extension and domain unfolding to properties of fibronectin nanotextiles

Fibronectin (FN) textiles are built as nanometer-thick fabrics. When uniaxially loaded, these fabrics exhibit a distinct threshold between elastic and plastic deformation with increasing stretch. Fabric mechanics are modeled using an eight-chain network and two-state model, revealing that elastic properties of FN depend on conformational extension of the protein and that plastic deformation depends on domain unfolding. Our results suggest how the molecular architecture of a molecule can be exploited for designer mechanical properties of a bulk material.

Titanium dioxide nanoparticles disturb the fibronectin-mediated adhesion and spreading of pre-osteoblastic cells

In the context of rapid development of nanoparticles (NPs) for industrial applications, the question of their toxicity and biological effects must be considered. In this work, we have assessed the influence of titanium dioxide NPs on the adhesion and spreading of MC-3T3 pre-osteoblasts by using a cell subclone that does not produce its own extracellular matrix. Petri dishes were coated with the important adhesion protein fibronectin (Fn). By incubating these Fn-coated surfaces with different amounts of TiO(2) NPs, we have shown that the adhesion of pre-osteoblasts is disturbed, with an important decrease in the number of adherent cells (from 40 to 75% depending upon the concentration and type of NPs). Petri-dish surfaces were analyzed with environmental scanning electron microscropy (ESEM), with images showing that TiO(2) NP aggregates are bound to the layer of adsorbed Fn molecules. The cells cultured on these Fn/NP surfaces adopted an irregular shape and an aberrant organization of actin cytoskeleton, as revealed by fluorescence microscopy. Most importantly, these results, taken together, have revealed that the actin cytoskeleton forms abnormal aggregates, even on top of the nucleus, that coincide with the presence of large aggregates of NPs on top of cells. On the basis of these observations, we propose that some Fn molecules are able to desorb from the Petri dish surface to coat TiO(2) NPs. Fn/NP complexes are not attached firmly enough on the surface to allow for normal cell adhesion/spreading and the development of tense actin fibers. These results stress the paramount need for the assessment of the toxicology of NPs, with special attention to their interactions with biomolecules.

Label-free live-cell imaging with confocal Raman microscopy

Confocal Raman spectroscopy is a noninvasive alternative to established cell imaging methods because it does not require chemical fixation, the use of fluorescent markers, or genetic engineering. In particular, single live-cell, high-resolution imaging by confocal Raman microscopy is desirable because it allows further experiments concerning the individually investigated cells. However, to derive meaningful images from the spectroscopic data, one must identify cell components within the dataset. Using immunofluorescence images as a reference, we derive Raman spectral signatures by means of information measures to identify cell components such as the nucleus, the endoplasmic reticulum, the Golgi apparatus, and mitochondria. The extracted signatures allow us to generate representations equivalent to conventional (immuno)fluorescence images with more than three cell components at a time, exploiting the Raman spectral information alone.

Interaction between oxide nanoparticles and biomolecules of the bacterial cell envelope as examined by infrared spectroscopy

The effects of Al(2)O(3), TiO(2), and ZnO nanoparticles (NPs) on bacteria cells and bacterial surface biomolecules were studied by Fourier transform infrared (FTIR) spectroscopy. All the examined biomolecules showed IR spectral changes after NP exposure. Lipopolysaccharide and lipoteichoic acid could bind to oxide NPs through hydrogen bonding and ligand exchange, but the cytotoxicity of NPs seemed largely related to the function-involved or devastating changes to proteins and phospholipids of bacteria. The three NPs decreased the intensity ratio of β-sheets/α-helices, indicating protein structure change, which may affect cell physiological activities. The phosphodiester bond of L-α-phosphatidylethanolamine was broken by ZnO NPs, forming phosphate monoesters and resulting in the highly disordered alkyl chain. Such damage to phospholipid molecular structure may lead to membrane rupture and cell leaking, which is consistent with the fact that ZnO is the most toxic of the three NPs. The cell surface biomolecular changes revealed by FTIR spectra provide a better understanding of the cytotoxicity of oxide NPs.

Conformational behavior of fibrinogen on topographically modified polymer surfaces

The influence of topographical surface features at the submicron scale on the structural changes in the surface-adsorbed fibrinogen was investigated on poly(lactic-co-glycolic-acid) (PLGA) films. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) was employed in this study for the induced conformational change of fibrinogen over various adsorption times, while the adsorption kinetics of fibrinogen was quantified by the enzyme linked immunosorbent assay (ELISA). When a PLGA surface is modified topographically, the adsorbed fibrinogen undergoes less conformational change when compared to adsorption on the pristine PLGA surface. The extent of conformational change is related to platelet adhesion. Reduced thrombogenicity was demonstrated by the higher ratios of alpha-helix to beta-turn and beta-sheet to beta-turn structures on the topographic PLGA film, which suggests that topographical manipulation of surfaces is a viable approach to influence the thrombogenicity of surfaces.

An integrated approach to the study of the interaction between proteins and nanoparticles

The rapid development of nanotechnology has raised some concerns about the effects of engineered nanoparticles (NPs) on human health and the environment. At the same time, NPs have attracted intense interest because of their potential applications in biomedicine. Hence, the requirement of detailed knowledge of what takes place at the molecular level when NPs get inside living organisms is a necessary step in assessing and likely predicting the behavior of an NP. The elicited effects strongly depend on the early events occurring when NPs reach biological fluids, where the interaction with proteins is the primary process. Whereas the adsorption of proteins on biomaterials has been thoroughly investigated, the mechanisms underlying the interaction of proteins with NPs are still largely unexplored. Here we report a study of the behavior of four model proteins differing in their resistance to conformational changes, net charge, and surface charge distributions, adsorbed on two nanometric silica powders with distinct hydrophilicity. An integrated picture of the adsorption process has been obtained by applying a whole set of techniques: the extent of coverage of the silica surface and the reversibility of the process were evaluated by combining the adsorption isotherms with the changes in the zeta potential and the point of zero charge for NPs at different protein coverages; the occurrence of protein deformation was evaluated by Raman spectroscopy, and EPR spectroscopy of spin-labeled proteins provided insight into their orientation on the silica surface. We have found that the extent of coverage of the nanoparticle surface is strongly influenced by the protein structural stability as well as by the distribution of charges at the protein surface.

Adsorption and stability of streptavidin on cluster-assembled nanostructured TiOx films

The study of the adsorption of proteins on nanostructured surfaces is of fundamental importance to understand and control cell-surface interactions and, notably, cell adhesion and proliferation; it can also play a strategic role in the design and fabrication of nanostructured devices for postgenomic and proteomic applications. We have recently demonstrated that cluster-assembled nanostructured TiO x films produced by supersonic cluster beam deposition possess excellent biocompatibility and that these films can be functionalized with streptavidin, allowing the immobilization of biotinylated retroviral particles and the realization of living-cell microarrays for phenotype screening. Here we present a multitechnique investigation of the adsorption mechanisms of streptavidin on cluster-assembled TiO x films. We show that this nanostructured surface provides an optimal balance between adsorption efficacy and protein functionality. By using low-resolution protein arrays, we demonstrate that a layer of adsorbed streptavidin can be stably maintained on a cluster-assembled TiO x surface under cell culture conditions and that streptavidin retains its biological activity in the adsorbed layer. The adsorption mechanisms are investigated by atomic force microscopy in force spectroscopy mode and by valence-band photoemission spectroscopy, highlighting the potential role of the interaction of the exposed carboxyl groups on streptavidin with the titanium atoms of the nanostructured surface.

Conformational Changes during Protein Adsorption. FT-IR Spectroscopic Imaging of Adsorbed Fibrinogen Layers

The influence of hydrophobicity of the substrate surface on structural changes during protein adsorption was investigated. Plasma fibrinogen was chosen to model this effect as it is the most important protein in the body that adsorbs to foreign surfaces. Only conformations of adsorbed fibrinogen similar to that of the protein in solution do not activate the process of blood coagulation. Small spots on the substrate surface with conformational changes within the adsorbed protein are already sufficient to deteriorate biocompatibility. Mid-infrared hyperspectral imaging permits the identification of coagulated spots down to a few micrometers in size. The spectra of the FT-IR images that were assessed to be of suitable quality were clustered by a fuzzy c-means algorithm. The determination of the appropriate number of clusters was based on cluster variance. Subsequent evaluation of the centroid spectra of each cluster showed that their amide I band was separated into contributions from different structural units, with the alpha-helix content always being dominant. Significant differences between hydrophobic and hydrophilic surfaces were observed for turn and sheet contributions. Lower sheet/turn ratios appear to indicate inferior biocompatibility. Spots on hydrophilic surfaces could be identified, which exhibit structural changes similar to those on hydrophobic surfaces.

Protein spreading kinetics at liquid-solid interfaces via an adsorption probe method

We report the areal growth kinetics of fibrinogen adsorbed on model hydrophobic and hydrophilic surfaces measured via an adsorption probe method. This approach exploits the adsorption of probe molecules to determine the evolution of fibrinogen test molecules under conditions where the fibrinogen test molecules adsorb at relatively dilute surface conditions, minimizing interactions between them. It is found that fibrinogen test molecules spread from an average initial footprint of 100 nm2 to a final footprint near 500 nm2 per molecule on the hydrophobic surface, with a single-exponential decay of 1735 s. On a hydrophilic monolayer, the area increases from 100 to 160 nm2 with a characteristic time of 6740 s. These results demonstrate the power of the adsorption probe approach and comprise the first measurements of the averaged area relaxations of adsorbed proteins. The observation of single-exponential dynamics is remarkable, given the extensive relaxation on the hydrophobic surface, which must involve fibrinogen denaturing.