Activity Of Mats Research Articles

Antiproliferative activity of nanofibers containing quaternized chitosan and/or doxorubicin against MCF-7 human breast carcinoma cell line by apoptosis

The antiproliferative activity of electrospun mats of poly(L-lactide- co-D,L-lactide) (coPLA) containing quaternized chitosan (QCh) and/or doxorubicin hydrochloride (DOX) was evaluated against the Michigan Cancer Foundation-7(MCF-7) human breast carcinoma cell line. QCh- and DOX-containing nanofibrous mats possess good antiproliferative activity and decrease considerably the viability of the MCF-7 cells for the different periods of cell incubation as confirmed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Fluorescent microscopy analyses and scanning electron microscopy observations revealed that apoptosis was one of the major mechanisms of MCF-7 cell death induced by the QCh- and DOX-containing mats.

Preparation and photocatalytic activity of nanoporous zirconia electrospun fiber mats

Nanoporous zirconia electrospun fiber mats (NZEFM) have been prepared by an electrospinning process using nonionic F108 as a pore-forming agent. This nonaqueous synthesis route has been employed to fabricate a stable “building block” porous structure inside the nano-scale fibers. The mats composed of individual fibers proved to be robust after calcination at up to 450 °C or stirring in water. The photocatalytic activity of NZEFM is apparently higher than that of commercial zirconia powder for the degradation of methyl orange in aqueous solution. Moreover, amorphous NZEFM mixed with the tetragonal phase obtained at 450 °C proved to be more efficient than the monoclinic phase NZEFM obtained at 900 °C. Various dyes could be degraded by NZEFM under UV light irradiation. The highly photocatalytic activity of NZEFM could be attributed to its high specific surface area and nanoporous “building block” structure made up of stacked zirconia nanoparticles.

Antibacterial Activity of Electrospun Polymer Mats with Incorporated Narrow Diameter Single-Walled Carbon Nanotubes

Polymer coatings featuring nonleaching antibacterial agents are needed to significantly reduce bacterial colonization and subsequent biofilm formation. Previously, single-walled carbon nanotubes (SWNTs) have been reported to be strong antimicrobial agents that kill microbes on contact. However, the antibacterial activity of freestanding polymer mats with a low weight percent of incorporated SWNTs has not been demonstrated. In this study, four different weight percents of well characterized, small diameter (0.8 nm) SWNTs were incorporated into electrospun polysulfone (PSf) mats. Electrospun PSf-SWNT mats were observed to be flexible and composed of continuous, cylindrical, and randomly oriented fibers. SEM micrographs revealed that SWNT ends were distributed along the longitudinal fiber axis. Loss of bacteria (Escherichia coli) viability was observed to directly correlate to increased SWNT incorporation within the mat, ranging from 18% for 0.1 wt % SWNTs to 76% for 1.0 wt % SWNTs. Time-dependent bacterial cytotoxicity studies indicated that the antimicrobial action of the PSf-SWNT mats occurs after a short contact time of 15 min or less. This study demonstrates the potential applicability of electrospun PSf-SWNT mats as antibacterial coatings.

Electrospun microfibrous poly(styrene- alt-maleic anhydride)/poly(styrene- co-maleic anhydride) mats tailored for enzymatic remediation of waters polluted by endocrine disruptors

Novel bicomponent microfibrous mats containing targeted amount of reactive maleic anhydride groups were prepared by electrospinning of mixed solutions of poly(styrene- alt-maleic anhydride) and poly(styrene- co-maleic anhydride). Then, amino-functionalized P(St- alt-MA)/P(St- co-MA) mats were obtained by reaction with p-phenylenediamine. ATR-FTIR and XPS spectroscopy were used to characterize pristine and modified P(St- alt-MA)/P(St- co-MA) mats. On the next step, laccase from Trametes versicolor was covalently attached onto the modified mats; the average amount of immobilized enzyme was 40 ± 0.7 mg/g mat. The catalytic activity of the immobilized enzyme was studied in respect to bisphenol A (BPA) endocrine disruptor. The optimum activity of the immobilized enzyme was reached at maximum flow rate of 1.3 mL/s. After 90 min the BPA concentration was reduced by 60% and the catalytic activity of microfibrous mats remained stable for about 30 successive reuses. In addition, the relative activity of laccase immobilized on the microfibrous mats was displayed in a broader pH range as compared to that of the free one.

48 The effects of environmental factors on the resumption of photosynthetic activity of cyanobacterial mats following rehydration

Extensive cyanobacterial mats cover the intertidal zone near Guerrero Negro, Baja California Sur. These mats are exposed to extreme desiccation and osmotic stress between tidal flows and rains, and spend most of the time dry and metabolically inactive. Therefore, periods of hydration are extremely important for growth as well as for repair of cellular damage from desiccation and ultraviolet radiation (UVR) accrued when the mat is dry. PAM fluorometry in conjunction with carbon incorporation assays were used to determine the effects of salinity, irradiance and UVR on the recovery of photosynthetic activity in these mats after an extended period of desiccation. The mat used in our study was primary composed of Lyngbya sp. Photosynthetic activity recovery rates (using PAM fluorometry) decreased with increasing salinity. This trend was similar under high and low light intensities, but rates were significantly lower under low light. Alternatively, the carbon incorporation method showed rates increased faster in salinities of 27 and 55 ppt than in salinities of 0 or 75 ppt. The Lyngbya mat also failed to recover photosynthetic potential in the dark. Although these mats recovered faster under high intensity light, the effect of salinity on photosynthesis is more complex. UVR did not affect the recovery of photosynthetic activity, no matter which method was used. This lack of effect is most likely due to the high content of the UVR screening pigment, scytonemin, in the upper layer of the mat.

Hypermethioninemia associated with methionine adenosyltransferase deficiency: Clinical, morphologic, and biochemical observations on four patients

Four patients with hypermethioninemia were ascertained in neonatal mass metabolic screening programs. Hypermethioninemia has persisted in all cases. There were no other abnormalities in sulfur-amino acid concentrations, and routine serum chemical determinations, including the results of "liver function" tests, were normal. Hepatic methionine adenosyltransferase activity was found to be low, ranging from 7.8 to 17.5% (mean 11.4%) of the normal adult control value. Electron microscopy of liver showed increased smooth endoplasmic reticulum, decreased rough endoplasmic reticulum, and increased lysosomes; short breaks in the outer membranes of mitochondria were present to a variable extent. Despite the persistent hypermethioninemia, which argues for continued deficiency of hepatic MAT, all four children appear well. This ostensible well being may be a result of the normal activity of extrahepatic MATs, as shown for erythrocytes and for cultured fibroblasts and lymphoid cells.