Emission characteristics of naphthalene from ship exhausts under global sulfur cap.

The global sulfur limit regulation mandates the use of 0.5 % low sulfur fuel oil (LSFO) to reduce emissions of sulfur oxides (SOx), nitrogen oxides (NOx), and particulate matter (PM). However, the addition of naphthalene (Nap) to LSFO to stabilize its quality has led to an increase in polycyclic aromatic hydrocarbons (PAHs), with Nap being the main pollutant. This study investigates the effects of Nap in ship exhaust by analyzing the emission concentrations of volatile organic compounds (VOCs) and Nap in the exhaust of 16 ships, including 2 container ships, 6 bulk carriers, 1 tanker, 2 ferries, 3 fishing vessels, and 2 harbor crafts, based on USEPA method TO-15A. The results show that the percentage of Nap emissions in the exhaust gases of the 16 ship engines ranged from 77 % to 97 % of the total volatile organic compound (TVOC). The Nap concentration in the exhaust of fishing vessels, tanker, and harbor craft exceeded the occupational exposure limit of 50,000 µg/m3, with fishing vessels having the highest TVOC and Nap concentrations. The enhanced Nap emission in the air degrades air quality in port cities and poses an obvious potential public health risk. While the benefits of the global sulfur cap are being secured, additional efforts should be made to reduce the undetected side effects. Alternative stabilizers of LSFO should be considered, or Nap emission control should be boosted to mitigate the potential negative impact on harbor air quality.

Shrinking mechanism of a porous collagen matrix immersed in solution.

The porous structure of collagen-based matrices enables the infiltration of cells both in in vitro and clinical applications. Reconstituted porous collagen matrices often collapse when they are in contact with aqueous solutions; however, the mechanism for the collapse of the pores is not understood. We, therefore, investigated the interactions between the collagen matrix and different solutions, and discuss the mechanisms for the change in microstructure of the matrix on immersing it in solution. When a dried collagen matrix was immersed in aqueous solutions, the matrix shrunk and pores close to the surface closed. The shrinkage ratio and thickness of the compact microstructure close to the superficial area decreased with increasing ethanol content in the solution. The original porous structure of the collagen matrix was preserved when the matrix was immersed in absolute ethanol. The shrinkage of a porous collagen matrix in contact with aqueous solutions was attributed to the liquid/gas interfacial tension. The average pore diameter of the matrix also significantly affected the shrinkage of the matrix. The shrinkage of the matrix, explained using the Young-Laplace equation, was found to result from the pressure drop, and especially in the pores located superficially, leading to the collapse of the matrix microstructure. The integrity of the porous microstructure allows better penetration of cells in medical applications. The numbers of NIH/3T3 fibroblasts penetrated through the hydrated Col/PBS porous collagen matrices pre-immersed in absolute ethanol with subsequent water and DMEM culture medium replacements were significantly higher than those through matrices hydrated directly in DMEM.

Counting CD4(+) and CD8(+) T cells in the spleen: a novel in vivo method for assessing biomaterial immunotoxicity.

As immunotoxicity assessments of newly developed biomaterials are often restricted to use in assessment of local tissue response at the implantation site, they do not always show an immune response acceptable to qualify them for clinical use. We tested a new method to assess systemic toxicity: counting the CD4(+) and CD8(+) cells in the spleen. Three different biomaterials were subcutaneously implanted in three groups of rats for the same time period. After 31 days, their spleens were harvested, and CD4(+) and CD8(+) cells were counted. The mean CD4(+)/CD8(+) cell counts were 24.5 ± 3.6/19.8 ± 4.0 (porous collagen matrix group), 25.5 ± 7.1/21.6 ± 3.8 [synthetic collagen matrix (Duragen®) group] and 28.1 ± 4.1/19.6 ± 3.7 (porcine dermis group). Differences in cell counts were not significant. The immunotoxic response generated against porous collagen matrix was comparable to that produced by a similar biomaterial already used clinically. This is, to the best of our knowledge, the first study on cytotoxic lymphocytes in the spleen to quantify systemic immune response to a biomaterial; however, such studies have been conducted with bacterial and viral antigens, and with vaccines. We believe that the present study provides a viable method for larger studies to confirm our current findings.

Hyaluronan preserves the proliferation and differentiation potentials of long-term cultured murine adipose-derived stromal cells.

For long-term culture, murine adipose-derived stromal cells (mADSCs) at latter passages demonstrated a marked decline in proliferative activity, exhibited senescent morphology and reduced differentiation potentials, particularly osteogenesis. To extend the lifespan of mADSCs, two culture conditions containing hyaluronan (HA) was compared in our study, one as a culture medium supplement (SHA), and the other where HA was pre-coated on culture surface (CHA). mADSCs cultivated with SHA exhibited a prolonged lifespan, reduced cellular senescence, and enhanced osteogenic potential compared to regular culture condition (control). Upon CHA treatment, mADSCs tended to form cell aggregates with gradual growth profiles, while their differentiation activities remained similar to SHA groups. After transferring mADSCs from CHA to control surface, they were shown to have an extended lifespan and an increase of osteogenic potential. Our results suggested that HA can be useful for preserving the proliferation and differentiation potentials of long-term cultured mADSCs.