Hydration behaviors of calcium silicate-based biomaterials.

BACKGROUND/PURPOSE: Calcium silicate (CS)-based biomaterials, such as mineral trioxide aggregate (MTA), have become the most popular and convincing material used in restorative endodontic treatments. However, the commercially available CS-based biomaterials all contain different minor additives, which may affect their hydration behaviors and material properties. The purpose of this study was to evaluate the hydration behavior of CS-based biomaterials with/without minor additives. METHODS: A novel CS-based biomaterial with a simplified composition, without mineral oxides as minor additives, was produced. The characteristics of this biomaterial during hydration were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectrometry. The hydration behaviors of commercially available gray and white MTAs with mineral oxide as minor additives were also evaluated for reference. RESULTS: For all three test materials, the XRD analysis revealed similar diffraction patterns after hydration, but MTAs presented a significant decrease in the intensities of Bi2O3-related peaks. SEM results demonstrated similar porous microstructures with some hexagonal and facetted crystals on the outer surfaces. In addition, compared to CS with a simplified composition, the FTIR plot indicated that hydrated MTAs with mineral oxides were better for the polymerization of calcium silicate hydrate (CSH), presenting Si-O band shifting to higher wave numbers, and contained more water crystals within CSH, presenting sharper bands for O-H bending. CONCLUSION: Mineral oxides might not result in significant changes in the crystal phases or microstructures during the hydration of CS-based biomaterials, but these compounds affected the hydration behavior at the molecular level.

Targeting efficiency and biodistribution of biotinylated-EGF-conjugated gelatin nanoparticles administered via aerosol delivery in nude mice with lung cancer.

Lung cancer is the most malignant cancer today; in order to develop an effective drug delivery system for lung cancer therapy, gelatin nanoparticles (GPs) were modified with NeutrAvidin(FITC)-biotinylated epidermal growth factor (EGF) to form EGF receptor (EGFR)-seeking nanoparticles (GP-Av-bEGF). Aerosol droplets of the GP-Av-bEGF were generated by using a nebulizer and were delivered to mice model of lung cancer via aerosol delivery. Analysis of the aerosol size revealed that 99% of the nanoparticles after nebulization had a mass median aerodynamic diameter (MMAD) within the suitable range (0.5-5 microm) for lower airway deposition. The safety of inhaled nanoparticles was examined by lung edema and myeloperoxidase (MPO) activity assay. There's no finding suggestive of acute lung inflammation following inhalation. The fluorescence images obtained from live mice showed that the GP-Av-bEGF could target the cancerous lungs in a more specific manner. Fluorescence analysis of the organs revealed that the GP-Av-bEGF was mainly distributed in cancerous lungs. In contrast, nanoparticle accumulation was lower in normal lungs. The histological results indicated that the fluorescent GP-Av-bEGF was colocalized with the anti-EGFR-immunostain due to EGFR binding. The results of this study revealed that GP-Av-bEGF could target to the EGFR-overexpression cancer cells in vivo and may prove to be beneficial drug carriers when administered by simple aerosol delivery for the treatment of lung cancer.

Cytotoxicity of partial-stabilized cement.

Partial-stabilized cement (PSC) is a kind of modified calcium silicate cement used for root-end surgery. Minor transition metal elements Co, Cr, and Zn were added for enhancing the setting property of to PSC. In our previous study, minor transition metal additions greatly improved the setting property of PSC. However, the concern of metal toxicity was raised, as the material would be used in the human body. In this study, we evaluated the cytotoxicity of PSC in comparison with mineral trioxide aggregate (MTA), which is one of the commercialized materials used for dental root-end filling. Primary osteoblast cell was used as the target cell. Cell proliferation, cytotoxicity, viability, function, and senescence were analyzed. The cytotoxicity of the PSC-Zn group (PSC with Zn addition) was similar to that of MTA. PSC-Zn is not only nontoxic at the cellular level but also has adequate mechanical property, which makes it a potential root-end filling material for apical surgery.

The effect of gelatin-chondroitin sulfate-hyaluronic acid skin substitute on wound healing in SCID mice.

Tissue-engineered skin substitutes provided a feasibility to overcome the shortage of skin autograft by culturing keratinocytes and dermal fibroblasts in vitro. In this study, we applied bi-layer gelatin-chondrointin-6-sulfate-hyaluronic acid (gelatin-C6S-HA) biomatrices onto the severe combined immunodeficiency (SCID) mice to evaluate its effect on promoting wound healing. Human foreskin keratinocytes and dermal fibroblasts were cultured with reconstructed skin equivalent (rSE) for 7 days. The rSE was then grafted to the dorsum of SCID mice to evaluate its biocompatibility by histologic and immunohistochemistry analysis. The results showed that human epidermis were well-developed with the expression of differentiated markers and basement membrane-specific proteins at 4 weeks. After implantation, the percentages of skin graft take were satisfactory, while cell-seeded group was better than non-cell-seeded one. The basement membrane proteins including laminin, type IV collagen, type VII collagen, integrin alpha6, and integrin beta4 were all detected at the dermal-epidermal junction, which showed a continuous structure in the 4 weeks after grafting. This bi-layer gelatin-C6S-HA skin substitute not only has positive effect on promoting wound healing, but also has high rate of graft take. This rSE would have the potential to be applied on the extensively and deeply burned patients who suffer from severe skin defect in the near future.

Transition element contained partial-stabilized cement (PSC) as a dental retrograde-filling material.

A modified silicate cement has previously been developed as a dental retrograde filling; it has great sealing ability, good biocompatibility, and anti-bacterial properties. However, its clinical application is limited by a long setting time and poor handling property. In the present study, the setting time has been shortened by raising the preparation temperature of the cement and adding transition elements into the partial-stabilized cement (PSC) to increase the rate of hydration reaction of the cement. The rate of the hydration was evaluated by micro-hardness measurement. Phase transformation and micro-structure were examined by an X-ray diffractometer and a scanning electron microscope, respectively.When the preparation temperature increased (1400 degrees C), the phase content of Ca(2)SiO(5)(C(2)S) and Ca(3)SiO(6)(C(3)S) increased but the CaO decreased. The setting time was shortened and the micro-hardness increased because the increased amplitude of vibration of the atoms about their equilibrium resting positions increased by increasing the heating temperature. When the transition elements were added to PSC, crystal defects were effectively created and monoclinic structure of C(3)S was favored to form, which would increase the hydrated reaction of PSC and shorten the setting time. Co addition is the most effective due to its ability to create more defects and stabilize the monoclinic structure. The micro-hardness of the PSC with Co 5 wt% addition was about 66 in the Vickers scale. It also exhibited an early setting within 20 min. We believe that the modified PSC will have a great potential in its application to perforation repair and retrograde filling in endodontic surgery.

Synthesis of partial-stabilized cement (PSC) via sol-gel process.

The traditional method of preparing partial-stabilized cement (PSC), which is a kind of calcium silicate cement, is through power mixing method. Low reaction efficiency and initial strength limited the application of PSC as a dental root-end filling material. This study provides a one-step sol-gel process for the synthesis of PSC. A complexing ligand is used for tuning down the activity of aluminum sec-butoxide (ASB) in order to avoid possible self-polymerization. After the modification with complex ligand, there is no residue of reactant observed on the analysis of SDT, and bonding between metal atoms is observed in the FTIR spectrum. Each component of PSC is identified using XRD. The hydration product, which is called portlandite, of sol-gel-synthesized PSC is observed after 1 day of hydration, and crystallinity of portlandite increases much faster than that of traditional PSC. The initial strength of sol-gel-synthesized PSC achieves detectable level 24 h earlier than that of traditional PSC; microhardness value of sol-gel-synthesized PSC at 7th day is 2.98 HV, which is much higher than that of traditional PSC (2.05 HV). PSC is successfully synthesized and the initial strength of PSC is improved by this modified sol-gel process.