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A systematic study of the real-time initial adhesion properties of fibroblasts on a fetal bovine serum-preadsorbed hydroxyapatite surface was successfully realized using a quartz crystal microbalance with dissipation analysis.

The promotion of the K-ion introduction into Ca-deficient hydroxyapatite (CDHA) via a citric acid coordination technique was clarified, resulting in a characteristic phase transition via the thermal stabilization of K-ion-doped CDHA.

Silicate-containing hydroxyapatite (SiHA) particles were synthesized and functionalized with polyethylene glycol-silane (PEG-silane) for clarifying the effect of the bioceramic surface hydration layer states on the collagen (Col) fibrillation degree. Plate-like SiHA particles were obtained containing the SiO

Hydroxyapatite (HA), as the main mineral component in hard tissues, has good biocompatibility. In particular, HA films are widely used as bioactive coatings for artificial bones and dental implants in biomedical fields. However, it is currently difficult to prepare a nanostructure-controlled HA film by a wet process for further applications. Herein, we report the synthesis of HA nanoparticles coordinated by citric acid (Cit/HA) based on the interactions between carboxylate and calcium ions to control the sizes and shapes of the hybrid nanoparticles, to improve their dispersibility in water and to eventually form uniform transparent films with nanospaces, and investigated the film formation mechanism. As compared with the well-known rod-like HA nanoparticles (size: 48 × 15 nm

Development of a technology for effectively controlling the precipitation of CP particles on PVA films via a biomimetic process was achieved using the CA-modification technique.

Interfacial interactions between anionic porphyrin (TCPP) and α-tricalcium phosphate in hydrolysis reaction were clarified, and the orientation of TCPP molecules on the reactive calcium phosphates can be controlled by the mineralization process.

Autogenous bone and metallic implant grafting has been used to repair and regenerate bone defects. However, there are still many unresolved problems. It is suggested that bioceramic nanoparticles should be developed and designed to promote effective bone regeneration. In addition, it is necessary to synthesize bioceramic nanoparticles that can support proteins related to bone repair and regeneration such as collagen and albumin. As the protein-interactive bioceramic, hydroxyapatite (HA) deserves to be mentioned and has several attractive properties that are useful in biomedical fields (

Alpha‐tricalcium phosphate (α‐TCP), which can be converted to calcium‐deficient hydroxyapatite (HA) by hydrolysis reaction, has been researched as a bone filling. Although the composites of α‐TCP with various organic molecules can exhibit a novel functionality, the reaction based on the addition of the interactive organic molecules has not been understood. Investigation of the hydrolysis conversion process under various conditions can lead to the elucidation of the biomineralization process. In this study, we investigated the hydrolysis conversion of α‐TCP to HA in the presence of orotic acid (Ort). As a result, the conversion rate from α‐TCP to HA at the reaction time of 3 h was improved to be more than five times as compared to that in the absence of Ort. Moreover, the addition of Ort promoted the crystal growth and suppressed the crystal growth in the m‐plane direction. Furthermore, the mechanism for promoting HA formation is assumed to be related to the molecular structure of Ort, which is capable of forming the interactions between carboxylate and Ca2+ ions.

The highly-oriented collagen fibrils that paralleled to one (rubbing) direction were fabricated by which the collagen molecular solution was spin-coated and self-assembled on the rubbed polyimide film. Subsequently, the hydroxyapatite crystals were precipitated on the collagen fibrils by immersing into simulated body fluid. In details, the carboxyl groups on the collagen fibrils were used as a reaction field for adsorption of Ca2+ ions and promoted the formation of hydroxyapatite crystals. As a result, the hydroxyapatite crystals grew along the a-axis leading to the formation of stable interfaces between hydroxyapatite crystals and collagen fibrils. Moreover, the oriented collagen fibril arrays were more useful for the nucleation and growth of hydroxyapatite. Therefore, we successfully fabricated the highly-oriented collagen fibril arrays which were useful for the precipitation of hydroxyapatite crystals.

Hydroxyapatite (HA) and citric acid (Cit)-coordinated HA (Cit/HA) nanoparticle films with different nanospaces were used to examine the nanospacial effect on the protein adsorption behavior and initial osteoblast-like cell adhesion ability through the premise of the stability and ionic dissociation characteristics of the films in biological solution. In particular, the Cit/HA nanoparticle film with a nanospace of 4.2 nm could realize massive and stereoscopic adsorption of proteins due to its larger specific surface area and smaller nanospace as compared with the case of the HA nanoparticle film. It was also found that the α-helix and (β-sheet + β-turn) component ratios of the adsorbed fetal bovine serum proteins on the Cit/HA nanoparticle films increased as compared with the case of the HA nanoparticle film through the secondary structure analysis of the adsorbed proteins, which contributed to the good initial cell culture properties on the film surfaces. Therefore, we successfully realized the control of protein adsorption states using different nanospacial HA and Cit/HA nanoparticle films to achieve excellent initial cell culture properties, which would provide new insights into the creation of novel cell culture substrate surfaces in the regenerative medicine fields.

The mechanism of highly-oriented collagen (Col) fibril arrays on rubbed polyimide (PI) films was investigated in order to understand the interfacial Col-PI interactions. It was found that the orientation of the surface functional groups of the rubbed PI films was most effectively controlled and optimized by the rubbing conditions. In particular, nano-grooves with a width of 100-600 nm and a depth of 2-10 nm were formed on the rubbed PI films at a rubbing strength of 2.4 m, leading to the formation of the highest density of the Col fibril array. Moreover, highly-oriented Col fibrils were formed inside the nano-grooves by the formation of hydrogen bonds between the CO of the imide groups (@ rubbed PI films) and the N-H of the amino groups (@ β-Sheets of Col molecules), resulting in the orientation of the Col molecules and subsequent assembly to the fibrils. Thus, the orientation and density of the fibril arrays on the rubbed PI films were successfully controlled by the interfacial interactions between the β-Sheet component of Col and the nano-groove surfaces of the rubbed PI films. Therefore, the novel technology of this study will provide an effective method to fabricate the one-directional fibrous nanostructures and to understand how to control the orientation of biomolecules

We successfully synthesized the photofunctionalized octacalcium phosphate (OCP) with layered structures and high biosafety. Specifically, two systems of europium(III) ion (Eu3+)-doped OCP particles...

Highly-oriented homogeneous collagen (Col) fibril arrays were successfully fabricated on a rubbed polyimide (PI) film for precipitating calcium phosphate (CP). The surface functional groups of PI were aligned using the rubbing treatment, where the CO bonds in imide groups had transition moments perpendicular to the rubbing direction and the CC (benzene rings), C–N and C–O–C bonds had transition moments parallel to the rubbing direction. After the Col molecular solution was spin-coated and self-assembled on the rubbed PI film, the Col fibrils parallel to the rubbing direction with an orientation ratio of 68 to 91% and a density of 121 ± 7 to 225 ± 22 number per mm were successfully formed on the rubbed PI film, indicating the occurrence of the interfacial interactions between the PI and Col molecules. Moreover, the carboxyl groups (–COOH) on the Col fibrils were used as the CP nucleation sites for Ca2+ ion adsorption, and subsequently the nucleation of CP was promoted by immersing the Col fibrils into a simulated body fluid. Specifically, the CP crystals were effectively precipitated on the Col fibrils and plate-like CP crystals were formed along the direction of Col fibril arrays. Therefore, this provides an effective method for the fabrication of one-directional Col fibril arrays as well as CP/Col fibrous nanostructures using a biomimetic process.

Green-emitting phosphorus-functionalized mesoporous silica (PMPS) nanospheres were fabricated by modifying their surfaces with (8-hydroxyquinoline) zinc (Znq2). A simulated body fluid soaking test and subsequent gas-adsorption measurements revealed that Znq2-modification could dramatically suppress the biodegradation of the nanospheres. This study establishes Znq2 as a novel and potential surface modifier of mesoporous silicas and demonstrates that effective surface design of the hosts will allow the exploitation of potential functionalities of the modifier.

We successfully synthesized methylene blue (MB

In this study, Eu3+-containing amorphous silica nanoparticles and Eu compounds were successfully synthesized via a mechanochemical solid-state reaction between silica nanoparticles and EuCl3·6H2O. This reaction was induced by a grinding process, and the states of Eu3+ in the silica/europium composites were investigated. The silica/europium composites exhibited orange–red color luminescence owing to the 5D0–7F0, 5D0–7F1, and 5D0–7F2 transitions, which indicated the presence of Eu3+ in the silica framework and the newly formed Eu compounds such as EuOCl and Eu(OH)2Cl. The mechanochemical reaction because of the grinding process effectively induced an interaction between the silica surface and europium chloride; subsequently, Eu(OH)2Cl was formed in the silica/europium composites. Additionally, the Eu(OH)2Cl in the silica/europium composite exhibited a higher thermal stability than that of simple Eu(OH)2Cl, indicating that the mechanochemical reaction mediated the formation of Eu(OH)2Cl and new chemical bonding between the newly formed Eu(OH)2Cl and the silica surface, providing improved thermal stability to Eu(OH)2Cl. Thus, we successfully prepared silica nanoparticles containing not only Eu(III) in the silica framework but also Eu compounds that exhibit unique chemical bonding during a mechanochemical reaction.

The synthesized elliptical hydroxyapatite (E-HAp) and needle-like HAp (N-HAp) nanoparticles (NPs) were electrophoretically deposited on a gold (Au) substrate. A comparative study of the hydration layers on E-HAp, N-HAp, and Au films was achieved to investigate the interfacial effect of the hydration layers on the conformation of the adsorbed fibrinogen (Fgn) and fibroblast adhesion properties. As a result, the ratios of three types of hydration layer states (free water, intermediate water, nonfreezing water) analyzed by a Fourier transform infrared (FT-IR) spectral deconvolution of the O-H stretching absorption band were investigated. The ratio of the bonding water state (i.e., intermediate and nonfreezing water molecules) is almost the same between two HAp films, and the E-HAp film with an elliptical shape and smaller particle size exhibited the smallest ratio of nonfreezing water, which can suppress the denaturation of the adsorbed protein. Subsequently, FT-IR spectral deconvolution results of the amide I band of the adsorbed Fgn on the E-HAp film indicated the higher proportion of α-helix and β-sheet structures as compared with those on the N-HAp and Au films, suggesting that the smaller proportion of nonfreezing waters would play a significant role in the stereoscopic Fgn conformation. In the culture of fibroblasts, FT-IR spectra of the adhered cells on the E-HAp, N-HAp, and Au films exhibited different absorbance intensities of the amide A, I, II, and III bands, suggesting a different amount of collagen-producing states by the cells, which were also supported by immunostaining results of the collagen type I. Therefore, the different hydration structures on the films clearly influenced the conformation of the adsorbed protein, and the preferential conformation was found at the interfaces between the fibroblasts and the underground E-HAp films.

We successfully prepared hybrid nanoparticles (NPs) with photofunctional interfaces between the citric acid (Cit) molecules and europium(III) ion (Eu3+)-doped hydroxyapatite (HA) (Eu:HA) to provide...

The transparent mesoporous silica (MPS) films prepared by a supramolecular templating method was immersed in simulated body fluid (SBF), and subsequently was sterilized to evaluate the film structural stability. With immersing in SBF, the calcium and phosphate ion adsorption on the film surfaces was promoted and the mesopore structures underwent the expansion, collapse and reconstruction processes for the SBF immersion time of 6 h. The MPS films immersed in SBF for 3 h exhibited the mesostructural stability with the sterilization processes. We also investigated the Fgn adsorption states on the sterilized MPS films, which were clearly changed with the immersion time in SBF because of the different adsorption states of calcium and phosphate ions at the mesopores. Furthermore, the proliferation and differentiation behaviors of the osteoblast-like cells on the sterilized MPS films were investigated to evaluate the cell culture ability. The osteoblast–like cells cultured on the sterilized MPS films had the fibrous morphologies while maintaining the high adhesion density and were promoted to be the bone tissue formation for 14 days, indicating the preferential film environment for the cells. Therefore, it was suggested that the MPS films of this study were useful for the cell culture substrate based on their high transparency, stability against sterilization treatment, and preferential cytocompatibility.

Phosphonate-containing mesoporous silica (PMPS) spheres were successfully synthesized using diethyl(2-bromoethyl)phosphonate and non-ionic and cationic surfactants. The spherical PMPS particles with the mesopores were effectively formed under the basic condition through the hydrolysis and condensation reactions of tetraethoxysilane, even though the BET surface area of the particles decreased with increasing the added phosphonate amount. The hollow structures with the mesopores were obtained in the preferential amount of the phosphonate.

The effect of the phosphoric acid addition into the mesoporous silica (MPS) films on the water molecular states was investigated using the infrared spectral separation techniques. When the larger amount of the phosphoric acid was introduced into the MPS films, the surface wettability was changed to hydrophilicity. The interactions between the PO43− and silicate ions would occur to form the phosphoric acid-interacted MPS films, and the surface silanol groups were effectively interacted with the water molecules, indicating the importance of the incorporated phosphoric ions.

We synthesized hydroxyapatite nanocrystals under the existence of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)europium(III) (EuTH) complex to form inorganic/organic hybrid nanocrystal (EHA). Then, the folic acid derivative (folate N-hydroxysuccinimidyl ester (FA-NHS)) as the targeting ligand for the HeLa cancer cells was immobilized on the EHA by the mediation of both 3-aminopropyltriethoxysilane and methyltriethoxysilane molecules. Here, we investigated the photofunctions based on the interfacial interactions between the FA-NHS and EHA nanohybrids for preparing the novel bioimaging nanomaterials. As a result, the photofunctions could be changed by the FA-NHS molecular occupancy on the EHA. When the molecular occupancy ratio to the EHA surfaces is at around 3–5%, the intense luminescence from the f–f transition of the Eu3+ ions as well as the charge transfer between the EuTH–FA-NHS was observed to exhibit higher quantum efficiency. Moreover, effective dispersibility in phosphate-buffered saline was confir...

Addition of poly (oxyethylene)cholesteryl ether in the synthesis promoted the formation of the hydroxyapatite nanoparticles (HAp NPs) with the elliptical morphologies. The adsorption mechanism, interfacial interactions and conformation of the adsorbed fibrinogen (Fgn) on the HAp NP films were investigated. The Fgn adsorption behavior demonstrated the higher affinity of Fgn with the HAp NP films. At the lower temperature at 22 °C, Fgn was preferentially adsorbed on the gold though hydrophobic interactions with the larger Fgn adsorption amount. At the higher temperature at 37 °C or at the higher phosphate ion concentrations caused the structural changes of the adsorbed Fgn. Moreover, the temperature increment in PBS increased the Fgn adsorption amount with the rearrangement into the end-on orientation of the Fgn. Accordingly, HAp induced the electrostatic force and hydrogen bonding to be the stable Fgn-HAp NP film, minimizing the interactions among the water molecules. The HAp NP films with the preferentially elliptical crystalline shapes induced the Fgn steric conformation structures, and the secondary structural changes of the adsorbed Fgn by the increment of temperature were also supported by the Fourier transform infrared spectroscopy (FTIR) deconvolution results.

This study aims to reveal the effects of pressure during cold isostatic pressing (CIP) on the microstructure and optical properties of fluorescent HAp complexes. Although the microsturucture-dependent properties of fluorescent HAp complexes have been reported to improve the antibacterial properties of photocatalyst coating layers, the mechanism behind the changes in the fluorescence properties of highly compressed HAp complexes has not yet been unveiled. CIP was successfully used to fabricate fluorescent HAp – amino acid complexes, and their fluorescence intensities increased with increasing fabrication pressure. Peak wavelength of fluorescence emitted by the HAp – amino acid complexes exhibited yellow to red shift. Although the thickness of the amino acid layer was saturated in higher pressure cases, the concentration of amino acids increased proportionally with pressure, which suggests changes in the packing structures of the ligands in the HAp– amino acid complexes. Polarized Raman spectroscopy measurements clearly detected ligands normally arranged to the HAp layer under high pressure fabrication conditions, which can provide the tightly packed ligand structure in the HAp– amino acid complexes. These tightly packed ligand structure in the HAp– amino acid complexes could emit stronger fluorescence owing to the increased density of complexations. This newly found pressure dependency in the optical properties of HAp–amino acid complexes is beneficial for developing biocompatible fluorescence materials or enhancement agents for antibacterial coating layers.

We have synthesized novel inorganic–organic hybrid systems based on the interactions between calcium phosphate (CP) and tris(2,2,6,6-tetramethyl-3,5-heptanedionato)europium (III) (EuTH) complex to clarify the states of the EuTH molecules. We achieved the nucleation and crystal growth of electronically localized of EuTH molecules using two different synthetic processes (based on the timing of the addition EuTH before and after the CP nucleation stage). The coordination environment of the Eu3+ ion inside/on the hybrids was clearly changed, having the higher spatial symmetry states in the hybrid. The aspect ratios of the hybrid crystallites were 2.5–6.0, suggesting that the EuTH molecules selectively interacted with the a–plane of the CP nuclei to induce preferential crystal growth along with the uncovered c–plane. The segregated EuTH molecules on CP surfaces suppressed Ca2+ dissolution from the hybrids in phosphate buffer saline. In the excitation spectra of the hybrids, the 7F0 → 5L6 transition appeared as a result of the interaction between the EuTH and phosphate ions, suggesting that the phosphate ions affected the coordination environment. In the luminescence spectra of the hybrids, the luminescence intensity ratio of the magnetic dipole transition (5D0 → 7F1) to electric dipole transition (5D0 → 7F2) were higher than those of EuTH and the other Eu3+-doped inorganic systems. Thus, the higher spatial symmetry states of the Eu3+ ion in the hybrids resulted in greater luminescence intensities and quantum efficiencies, which would be affected by the phosphorus anti-quenching. In the future, CP hybrids with various organic complexes will be prepared, and these could be applied in the biomedical fields such as in bio-imaging and drug delivery systems.

The highly-oriented cylindrical mesoporous silica films were synthesized on the rubbing-treated polyimide by adjusting the molar ratio of the orientation-directing agent (Brij56) to the structure-directing agent (P123) as surfactants in the silica precursor solutions for guiding protein adsorption states. As a result, the diameter and the orientation degree of mesopores changed with the molar ratio of Brij56 to P123. The maximum orientation degree (93%) of cylindrical mesopores oriented in the direction perpendicular to the rubbing direction was observed when the molar ratio of Brij56 to P123 was 3. Then, the dissolution features in simulated body fluid and the protein adsorption properties of the oriented cylindrical mesoporous silica films were investigated. The silica skeletons were gradually dissolved from the upper film surfaces and subsequently, the mesopore structures were collapsed when the films were immersed for 90 min. Moreover, the protein adsorption amount and the ratio from the mono-component and two-component solutions on the films were higher than those on the unoriented cylindrical mesoporous silica films due to the formation of open-ended cylindrical mesopore shapes and sizes. In addition, the shapes of the proteins adsorbed on the films had anisotropy, which would be reflected by the cylindrical mesopore shapes generated by the dissolution of silica layers and subsequent exposure of inner mesopore surfaces. Therefore, the synthesized highly-oriented cylindrical mesoporous silica films were useful to adsorb mesoscale biomolecules such as proteins and can effectively guide their anisotropic adsorption shapes, and therefore have the potential to be used as surface-coating films of polyimide in biomedical fields.

Transparent phosphorus-containing MPS (PMPS) films were synthesized by the introduction and reaction of phosphoric acid into the silica framework during the sol-gel reaction. We then investigated the hydration layer structures formed on the PMPS films and achieved the selective adsorption of fibronectin (Fn). In particular, the surface analyses indicated that the P atom was distributed at the outermost surfaces of the PMPS films. The PMPS films exhibited a high transparency (e.g., averaged transmittance value in the visible light region: 79%), and the haze value (0.14%) decreased with the increasing P/Si molar concentration. Solid-state 29Si-NMR and Fourier transform infrared spectroscopy (FT-IR) spectra indicated the formation of Si-O-P bonds, suggesting that the condensation reaction between the Si-O- and P-O- groups effectively occurs in the silica framework. The larger amount of P-O- and P[double bond, length as m-dash]O groups at the Si-O-P bonding site on the films affects the water molecular adsorption states (i.e., formation of the hydration layer), which was supported by the Brunauer-Emmett-Teller (BET) surface areas of N2 and water vapor, leading to enhancement of the hydrogen bondability of the PMPS films with the increased formation of Si-O-P bonds. The deconvolution results of the FT-IR spectra demonstrated that the ratio of free water to bonding water increased significantly with an increase in the formation of Si-O-P bonding, and the resulting O-H stretching vibration in the hydration layer became more asymmetric. It is suggested that the water molecules are irregularly hydrogen-bonded with the different functional groups of Si-O-, P-O- and P[double bond, length as m-dash]O. In the immersion experiment of the PMPS films in phosphate buffer, the resultant P/Si molar concentration of the PMPS film decreased upon increasing the immersion time and the mesostructures were preserved. The amount of Fn adsorption significantly increased as the O-H stretching vibration of the water molecules became more asymmetric, whereas the adsorption of fibrinogen was completely suppressed by the films. Therefore, we found that the addition of phosphoric acid in the MPS film synthesis significantly affects the hydration layer structures on the film surfaces to provide the possibility of selective protein adsorption.