Hydrothermal Fabrication of Highly Porous Titanium Bio-Scaffold with a Load-Bearable Property.

Porous titanium (P_Ti) is considered as an effective material for bone scaffold to achieve a stiffness reduction. Herein, biomimetic (bio-)scaffolds were made of sintered P_Ti, which used NaCl as the space holder and had it removed via the hydrothermal method. X-ray diffraction results showed that the subsequent sintering temperature of 1000 °C was the optimized temperature for preparing P_Ti. The compressive strength of P_Ti was measured using a compression test, which revealed an excellent load-bearing ability of above 70 MPa for that with an addition of 50 wt % NaCl (P_Ti_50). The nano-hardness of P_Ti, tested upon their solid surface, was presumably consistent with the density of pores vis-à-vis the addition of NaCl. Overall, a load-bearable P_Ti with a highly porous structure (e.g., P_Ti_50 with a porosity of 43.91% and a pore size around 340 µm) and considerable compressive strength could be obtained through the current process. Cell proliferation (MTS) and lactate dehydrogenase (LDH) assays showed that all P_Ti samples exhibited high cell affinity and low cell mortality, indicating good biocompatibility. Among them, P_Ti_50 showed relatively good in-cell morphology and viability, and is thus promising as a load-bearable bio-scaffold.

Nanofabricated SERS-active substrates for single-molecule to virus detection in vitro: a review.

The surface-enhanced Raman scattering (SERS) method has great potential for the detection of Raman-active species, ranging from single molecules to biomolecules. In the last five years, various approaches have been developed to fabricate SERS-active substrates with high sensitivity using noble metal nanostructures via top-down, bottom-up, combination, or template-assisted routes. Nanostructured substrates with high average SERS enhancement factors (EFs) can now be easily produced, with the EF depending strongly on the size and shape of the nanostructures that give rise to the effect. For SERS substrates to be used as a platform for applications such as trace detection and bio-sensing, several issues, including sensitivity, intensity-concentration dependency, and selectivity, need to be addressed. Although several challenges remain before SERS-active substrates become consistent analytical tools, many successful examples have been demonstrated with promising results.

Focused-ion-beam-fabricated Au nanorods coupled with Ag nanoparticles used as surface-enhanced Raman scattering-active substrate for analyzing trace melamine constituents in solution.

A well-ordered Au-nanorod array with a controlled tip ring diameter (Au_NRsd) was fabricated using the focused ion beam method. Au_NRsd was then coupled with Ag nanoparticles (Ag NPs) to bridge the gaps among Au nanorods. The effect of surface-enhanced Raman scattering (SERS) on Au_NRsd and Ag NPs/Au_NRsd was particularly verified using crystal violet (CV) as the molecular probe. Raman intensity obtained from a characteristic peak of CV on Au_NRsd was estimated by an enhancement factor of ≈10(7) in magnitude, which increased ≈10(12) in magnitude for that on Ag NPs/Au_NRsd. A highly SERS-active Ag NPs/Au_NRsd was furthermore applied for the detection of melamine (MEL) at very low concentrations. Raman-active peaks of MEL (10(-3) to 10(-12)M) in water or milk solution upon Au_NRsd or Ag NPs/Au_NRsd were well distinguished. The peaks at 680 and 702 cm(-1) for MEL molecules were found suitable to be used as the index for sensing low-concentration MEL in a varied solution, while that at 1051 cm(-1) was practical to interpret MEL molecules in water or milk solution bonded with Au (i.e., Au_NRsd) or Ag (i.e., Ag NPs/Au_NRsd) surface. At the interface of Ag NPs/Au_NRsd and MEL molecules in milk solution, a laser-induced electromagnetic field or hotspot effect was produced and competent to sense low-concentration MEL molecules interacting with Ag and Au surfaces. Accordingly, Ag NPs/Au_NRsd is very promising to be used as a fast and sensitive tool for screening MEL in complex matrices such as adulteration in e.g., food and pharmaceutical products.

Hydrophilic gelatin and hyaluronic acid-treated PLGA scaffolds for cartilage tissue engineering.

UNLABELLED: Tissue engineering provides a new strategy for repairing damaged cartilage. Surface and mechanical properties of scaffolds play important roles in inducing cell growth. AIM: The aim of this study was to fabricate and characterize PLGA and gelatin/hyaluronic acid-treated PLGA (PLGA-GH) sponge scaffolds for articular cartilage tissue engineering. METHODS: The PLGA-GH scaffolds were cross-linked with gelatin and hyaluronic acid. Primary chondrocytes isolated from porcine articular cartilages were used to assess cell compatibility. The characteristic PLGA-GH scaffold was higher in water uptake ratio and degradation rate within 42 days than the PLGA scaffold. RESULTS: The mean compressive moduli of PLGA and PLGA-GH scaffolds were 1.72 ± 0.50 MPa and 1.86 ± 0.90 MPa, respectively. The cell attachment ratio, proliferation, and extracellular matrix secretion on PLGA-GH scaffolds are superior to those of PLGA scaffolds. CONCLUSIONS: In our study, PLGA-GH scaffolds exhibited improvements in cell biocompatibility, cell proliferation, extracellular matrix synthesis, and appropriate mechanical and structural properties for potential engineering cartilage applications.

Synergistic stimuli by hydrodynamic pressure and hydrophilic coating on PLGA scaffolds for extracellular matrix synthesis of engineered cartilage.

Scaffold surface properties and mechanical stimuli have been known to have a critical influence on cell proliferation and extracellular matrix synthesis in cultured cells for tissue engineering. Hydrophilic surface and hydrodynamic pressure (HP) stimulation have been shown to have a beneficial effect on chondrocyte activity. The aim of this study was, thus, to assess the synergic influences of HP and hydrophilic coating on cell activity using primary porcine chondrocytes inoculated in hydrophilic-coated poly(lactide-co-glycolide) (PLGA) sponge scaffolds. The natural materials hyaluronic acid (HA), chitosan and HA/chitosan were cross-linked on porous PLGA as a hydrophilic surface modification. HP was applied to scaffolds at an amplitude of 2.24 MPa and a frequency of 0.1 Hz for 30 min per day, twice a week, over a period of 28 days. Cell activities were determined by the MTS assay and the dimethylmethylene blue assay for glycosaminoglycan (GAG) quantification. Our results displayed that PLGA coated with both HA and chitosan had the best hydrophilicity (contact angle 49.46°) and initial compressive modulus (1.10 ± 0.13 MPa) among the tested scaffold groups. Additionally, HP stimulation enhanced cell proliferation as well as GAG production (up to 3-fold in culture medium and 15-fold in scaffolds at 28 days compared to static culture of PLGA alone in the scaffold group) in the hydrophilic-coated scaffold groups. The synergistic benefit from hydrophilic coating and HP stimulation may be imperative in regenerating engineered cartilage in the long-term.

Enhanced Schwann cell adhesion and elongation on a topographically and chemically modified poly(L-lactic acid) film surface.

A dense poly-L-lactic acid (PLLA) film was employed as the primary material and hot-embossed with the formation of microgrooves (g-PLLA). A thin layer of Au was then deposited on the film to obtain a morphologically modified substrate (Au/g-PLLA). The Au/g-PLLA film surface was then chemically modified by imprinting octadecanethiolate (ODT) self-assembled monolayers on the upper surface (ODT/Au/g-PLLA), followed by Arg-Gly-Asp (RGD) peptide sequences on the microgrooves (RGD_ODT/Au/g-PLLA). The surface chemistry of the as-prepared RGD_ODT/Au/g-PLLA samples was examined. The bioactivity and spreading function of Schwann cells cultured on the morphologically and chemically modified surfaces were assessed. The results demonstrate that Schwann cells adhered to the RGD/Au/g-PLLA surface and proliferated along the microgrooves without crossing over the ODT/Au/PLLA surface. The proposed film surface can be used for manipulating the outgrowth of axons by modifying and arranging a selected region to induce cell growth and to prevent cells from spreading out nondirectionally.