Annealing Effect of Glancing Angle Electron Beam Deposited TiO2/In2O3 Nanowires Array on Surface Wettability

TiO₂/In₂O₃ nanowire (NW) array are prepared using catalyst free glancing angle deposition technique. The wettability of TiO₂/In₂O₃ NW surface are tuned and controlled by the annealing treatment without altering the surface with additional chemical coating. The phase change, surface roughness, change in static and dynamic contact angles due to the heat treatment are studied. Moreover, the surface properties such as frictional force and work of adhesion are calculated for all the samples. The samples annealed at 600 °C shows nearly superhydrophilic with static water contact angle of 12°, frictional force of 85.00748 µN and work of adhesion of 142.3721 mN/m. The surface of TiO₂/In₂O₃ NW is controlled to attain desired water contact angles and sliding angles, which is paramount for designing practical application in self-cleaning, electronic and biomedical fields.

Temperature regulation of the contact angle of water droplets on the solid surfaces

We investigate theoretically the stability of the wetting property, i.e., the contact angle values, as a function of the temperature. We find that the estimated temperature coefficient of the contact angle for the water droplets on an ordered water monolayer on a 100 surface of face-center cubic (FCC) is about one order of magnitude larger than that on a hydrophobic hexagonal surface in the temperature range between 290 K and 350 K, using molecular dynamics simulations. As temperature rises, the number of hydrogen bonds between the ordered water monolayer and the water droplet will increase, which therefore enhances the hydrophilicity of the ordered water monolayer at the FCC model surface. Our work thus provides an easily controllable and reversible way to control the degree of hydrophobicity of various solid surfaces exhibiting a similar wetting property of water droplets on the ordered water monolayer as such particular FCC (100) surfaces.

Novel Scaffold Containing Transforming Growth Factor-β1 DNA for Cartilage Tissue Engineering

The current progression in tissue engineering and local gene delivery systems has enhanced applications for cartilage tissue engineering. In this study, porous chitosan/collagen scaffolds were prepared through a freeze-drying process and loaded with plasmid encoding human transforming growth factor-β1 (TGFβ1). Human bone marrow stem cells were seeded in this scaffold, and gene transfection was traced by enhanced green fluorescent protein (EGFP). The expression of type II collagen and aggrecan was detected with reverse transcription-polymerase chain reaction, and cell proliferation was measured every day for six days using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide assay. The pore diameter of the gene-combined scaffolds was lower than that of the pure chitosan/collagen scaffold. The scaffold containing TGFβ1 plasmid exhibited the highest proliferation rate, and the expression of type II collagen and aggrecan was upregulated in the pEGFP-TGFβ1 scaffold. The potential for chitosan/collagen scaffold combined with pEGFP-TGFβ1 as a substrate candidate in cartilage tissue engineering has been investigated.

Chitosan/Carboxymethyl Cellulose Polyelectrolyte Complex Scaffolds for Pulp Cells Regeneration

Novel polyelectrolyte complex (PEC) chitosan/carboxymethyl cellulose (CMC) scaffolds are prepared using a freeze-dry process. The microstructure is characterized by SEM and the average pore diameters and internal porosities are calculated. The morphology and distribution of pulp cells on these three-dimensional scaffolds are investigated by SEM and confocal laser scanning microscopy (CLSM). The expression of osteonectin (ON) and dentin sialophosphoprotein (DSPP) is detected by reverse transcription polymerase chain reaction (RT-PCR). The scaffolds are then implanted subcutaneously into BALB/c mice. The addition of CMC to chitosan decreases the pore diameter and increases internal porosity. The pulp cells co-cultured in these PEC scaffolds show improved adhesion, spreading, cell capacity, and three-dimensional configurations compared to pure chitosan scaffolds. Based on the data obtained, the chitosan/CMC complex provides an improved scaffold material for pulp tissue engineering.

Adjustable degradation properties and biocompatibility of amorphous and functional poly(ester-acrylate)-based materials

Tuning the properties of materials toward a special application is crucial in the area of tissue engineering. The design of materials with predetermined degradation rates and controlled release of degradation products is therefore vital. Providing a material with various functional groups is one of the best ways to address this issue because alterations and modifications of the polymer backbone can be performed easily. Two different 2-methylene-1,3-dioxepane/glycidyl methacrylate-based (MDO/GMA) copolymers were synthesized with different feed ratios and immersed into a phosphate buffer solution at pH 7.4 and in deionized water at 37 °C for up to 133 days. After different time intervals, the molecular weight changes, mass loss, pH, and degradation products were determined. By increasing the amount of GMA functional groups in the material, the degradation rate and the amount of acidic degradation products released from the material were decreased. As a result, the composition of the copolymers greatly affected the degradation rate. A rapid release of acidic degradation products during the degradation process could be an important issue for biomedical applications because it might affect the biocompatibility of the material. The cytotoxicity of the materials was evaluated using a MTT assay. These tests indicated that none of the materials demonstrated any obvious cytotoxicity, and the materials could therefore be considered biocompatible.

Polyester copolymer scaffolds enhance expression of bone markers in osteoblast-like cells

In tissue engineering, the resorbable aliphatic polyester poly(L-lactide) (PLLA) is used as scaffolds in bone regeneration. Copolymers of poly(L-lactide)-co-(epsilon-caprolactone) [poly(LLA-co-CL)] and poly(L-lactide)-co-(1,5-dioxepan-2-one) [poly(LLA-co-DXO)], with superior mechanical properties to PLLA, have been developed to be used as scaffolds, but the influence on the osteogenic potential is unclear. This in vitro study of test scaffolds of poly(LLA-co-CL) and poly(LLA-co-DXO) using PLLA scaffolds as a control demonstrates the attachment and proliferation of human osteoblast-like cells (HOB) as measured by SEM and a methylthiazol tetrazolium (MTT) colorimetric assay, and the progression of HOB osteogenesis for up to 3 weeks; expressed as synthesis of the osteoblast differentiation markers: collagen type 1 (Col 1), alkaline phosphatase, bone sialoprotein, osteocalcin (OC), osteopontin and runt related gene 2 (Runx2). Surface analysis disclosed excellent surface attachment, spread and penetration of the cells into the pores of the test scaffolds compared to the PLLA. MTT results indicated that test scaffolds enhanced the proliferation of HOBs. Cells grown on the test scaffolds demonstrated higher synthesis of Col 1 and OC and also increased bone markers mRNA expression. Compared to scaffolds of PLLA, the poly(LLA-co-CL) and poly(LLA-co-DXO) scaffolds enhanced attachment, proliferation, and expression of osteogenic markers by HOBs in vitro. Therefore, these scaffolds might be appropriate carriers for bone engineering.

Effect of Surface Polarity on Water Contact Angle and Interfacial Hydration Structure

We perform molecular dynamics simulations of water in the presence of hydrophobic/hydrophilic walls at T = 300 K and P = 0 GPa. For the hydrophilic walls, we use a hydroxylated silica model introduced in previous simulations [Lee, S. H.; Rossky, P. J. J. Chem. Phys. 1994, 100, 3334. Giovambattista, N.; Rossky, P. J.; Debenedetti, P. G.; Phys. Rev. E 2006, 73, 041604.]. By rescaling the physical partial atomic charges by a parameter 0 <or= k <or= 1, we can continuously transform the hydrophilic walls (hydroxylated silica, k = 1) into hydrophobic apolar surfaces (k = 0). From a physical point of view, k is the normalized magnitude of a surface dipole moment, and thus it quantifies the polarity of the surface. We calculate the contact angle of water for 0 <or= k <or= 1. We find that, at least for the present homogeneous, atomically flat, and defect-free surface model, the magnitude of the surface dipole correlates with the contact angle in a one-to-one correspondence. In particular, we find that polar surfaces with 0 < k <or= kc = 0.4 are macroscopically hydrophobic; that is, the contact angle is larger than 90 degrees . For the cutoff value k = kc, the magnitude of the dipole moment of the polar silica surface unit is 41% that of the water molecule dipole moment. We also study the water orientation distributions next to the walls (a microscopic property). We find that these distributions also correlate with the contact angle in a one-to-one correspondence. Thus, the structure of confined water, the surface polarity, and the contact angle are in a direct correspondence to each other, and therefore, each quantifies the hydrophobicity/hydrophilicity of the surface.