Switchable Release of Bone Morphogenetic Protein from Thermoresponsive Poly(NIPAM-co-DMAEMA)/Cellulose Sulfate Particle Coatings

Thermoresponsive coatings of poly(N-isopropylacrylamide-co-DMAEMA)/cellulose sulfate (PNIPAM-DMAEMA/CS) complexes are reported eluting bone-morphogenetic-protein-2 (BMP-2) on demand relevant for implant assisted local bone healing. PNIPAM-DMAEMA/CS dispersions contained colloid particles with hydrodynamic radii RH = 170–288 nm at T = 25 °C shrinking to RH = 74–103 nm at T = 60 °C. Obviously, PNIPAM-DMAEMA/CS undergoes volume phase transition (VPT) analogously to pure PNIPAM, when critical VPT temperature (VPTT) is exceeded. Temperature dependent turbidity measurements revealed broad VPT and VPTT 47 °C for PNIPAM-DMAEMA/CS colloid dispersions at pH = 7.0. FTIR spectroscopy on thermoresponsive PNIPAM-DMAEMA/CS particle coatings at germanium model substrates under HEPES buffer indicated both wet-adhesiveness and VPT behavior based on diagnostic band intensity increases with temperature. From respective temperature courses empirical VPTT ≈ 42 °C for PNIPAM-DMAEMA/CS coatings at pH = 7.0 were found, which were comparable to VPTT found for respective dispersions. Finally, the PNIPAM-DMAEMA/CS coatings were loaded with BMP-2 and model protein papain (PAP). Time dependent FTIR spectroscopic measurements showed, that for T = 37 °C there was a relative protein release of ≈30% for PAP and ≈10% for BMP-2 after 24 h, which did not increase further. Heating to T = 42 °C for PAP and to 47 °C for BMP-2 further secondary protein release of ≈20% after 24 h was found, respectively, interesting for clinical applications. BMP-2 eluted even at 47 °C was found to be still biologically active.

Neutralization of acidic sulfates with ammonia in volcanic origin aerosol particles

Volcanic pollutants emitted during the Grimsvötn volcano eruption in Iceland on 21 May 2011 were unexpectedly captured from 24 until 29 May 2011 at the Institute of Physics, Vilnius. Measurements were performed using an Aerodyne quadrupole aerosol mass spectrometer. This paper aims to address the question whether the extent of neutralization is dependent on the aerosol particle size in submicron range particles (PM1). Data from two episodes of volcanic pollutants in advected air masses were chosen for examination. The first episode lasted from 0700 to 1400 UTC 25 May and the second episode lasted from 0400 until 1100 UTC 26 May. It was observed that the extent of acidic sulfate particle neutralization with atmospheric ammonia depends on the aerosol particle size. The extent of neutralization decreased when the particle aerodynamic diameter increased. Particles with an aerodynamic diameter of few tenths of nanometres tended to be fully neutralized and those with a consecutively increasing diameter of up to 1 µm were only partially neutralized. The assessment of ambient ammonia flux onto the adjacent aerosol particle surface was performed. It was shown that the flux of ammonia can vary approximately from 30 to 74 µg m–2 h–1.

Source apportionment of PM_2.5 in Cork Harbour, Ireland using a combination of single particle mass spectrometry and quantitative semi-continuous measurements

An aerosol time-of-flight mass spectrometer (ATOFMS) was co-located with a suite of semi-continuous instrumentation for the quantitative measurement of elemental carbon (EC), organic carbon (OC), sulfate, particle number and PM2.5 mass at a site in Cork Harbour, Ireland for three weeks in August 2008. Off-line analysis of polar organic markers was also performed for the same period. The data collected was used to identify and apportion local and regional sources of PM2.5. Over 550 000 ATOFMS particle mass spectra were generated and classified using the K-means algorithm. The vast majority of particles ionised by the ATOFMS were attributed to local sources, although one class of carbonaceous particles detected is attributed to North American or Canadian anthropogenic sources. The temporality of the ambient ATOFMS particle classes was subsequently used in conjunction with the semi-continuous measurements to apportion PM2.5 mass using positive matrix factorisation. Six factors were obtained, corresponding to vehicular traffic, marine, long-range transport, power generation, domestic solid fuel combustion and shipping traffic. The estimated contribution of each factor to the measured PM2.5 mass was 23%, 14%, 13%, 11%, 5% and 1.5%, respectively. Shipping was found to contribute 18% of the measured particle number (20–600 nm mobility diameter), and thus may have implications for human health considering the size and composition of ship exhaust particles.