Biomedical subjects

Markku Leskelä

Publications and source records attributed to Markku Leskelä.

7 recordsLinked to original sources

PubMed2005

Destruction of Deinococcus geothermalis biofilm by photocatalytic ALD and sol-gel TiO2 surfaces.

The aim of the present work was to explore possibilities of photocatalytic TiO2 coating for reducing biofilms on non-living surfaces. The model organism, Deinococcus geothermalis, known to initiate growth of durable, colored biofilms on machine surfaces in the paper industry, was allowed to form biofilms on stainless steel, glass and TiO2 film coated glass or titanium. Field emission electron microscopy revealed that the cells in the biofilm formed at 45 degrees C under vigorous shaking were connected to the surface by means of numerous adhesion threads of 0.1-0.3 microm in length. Adjacent cells were connected to one another by threads of 0.5-1 microm in length. An ultrastructural analysis gave no indication for the involvement of amorphous extracellular materials (e.g., slime) in the biofilm. When biofilms on photocatalytic TiO2 surfaces, submerged in water, were exposed to 20 W h m(-2) of 360 nm light, both kinds of adhesion threads were completely destroyed and the D. geothermalis cells were extensively removed (from >10(7) down to below 10(6) cells cm(-2)). TiO2 films prepared by the sol-gel technique were slightly more effective than those prepared by the ALD technique. Doping of the TiO2 with sulfur did not enhance its biofilm-destroying capacity. The results show that photocatalytic TiO2 surfaces have potential as a self-cleaning technology for warm water using industries.

Biofilms↗

PubMed2005

Atomic layer deposition in nanometer-level replication of cellulosic substances and preparation of photocatalytic TiO2/cellulose composites.

TiO2 replicas of filter paper with nanometer-level accuracy were prepared by atomic layer deposition of thin conformal TiO2 coating, followed by a removal of the paper by air-anneal at 450 degrees C. Photocatalytic anatase TiO2/cellulose composites were also made by leaving the paper intact. The TiO2 films were deposited from Ti(OMe)4 and H2O at 150-250 degrees C. The photocatalytic activity of the TiO2/cellulose composite was verified by photocatalytic reduction of Ag(I) from an aqueous solution to Ag nanoparticles on the TiO2 surface. The TiO2/cellulose composites are mechanically more stable than the free-standing TiO2 replicas and are therefore potentially suitable as lightweight, high surface area photocatalysts.

Adsorption↗

PubMed2005

In situ quadrupole mass spectrometry study of atomic-layer deposition of ZrO2 using Cp2Zr(CH3)2 and water.

Reactions during the atomic layer deposition (ALD) process of ZrO(2) from Cp(2)Zr(CH(3))(2) and deuterated water as precursors were studied with a quadrupole mass spectrometer (QMS) at 210-440 degrees C. The detected reaction byproducts were CpD (m/z = 67) and CH(3)D (m/z = 17). Almost all (90%) of the CH(3) ligands were released during the Cp(2)Zr(CH(3))(2) precursor pulse because of exchange reactions with the OD-terminated surface, and the rest, during the D(2)O pulse. About 40% of the CpD was released during the metal precursor pulse, and 60%, during the D(2)O pulse. ALD-type self-limiting growth was confirmed from 210 to 400 degrees C. However, below 300 degrees C the growth rate was low. Precursor decomposition affected the film growth mechanism at temperatures exceeding 400 degrees C.

Journal Article↗

PubMed2004

Synthesis and characterisation of cyclopentadienyl complexes of barium: precursors for atomic layer deposition of BaTiO3.

Cyclopentadienyl complexes Ba(C5Me5)2(THF)2 (1), Ba(C5Me5)2(A) (A = THF, dien, trien, diglyme, triglyme) (2-5), Ba(Pr(i)3C5H2)2(THF)2 (6), Ba(Bu(t)3C5H2)2(THF) (7), Ba(Me2NC2H4C5Me4)2 (8) and Ba(EtOC2H4C5Me4)2 (9) were prepared and characterised with TGA/SDTA, NMR and MS. Crystal structures of 2, 4, 5, 7, 8 and 9 are presented. All complexes prepared sublime under reduced pressure and complexes 1, 6 and 7 showed volatility also under atmospheric pressure. Complexes 1, 6 and 7 lose the coordinated THF when evaporated while complexes 2-5 are sublimable as complete molecules under reduced pressure. Complexes with bulky cyclopentadienyl ligands (6 and 7) are the most thermally stable and volatile among the prepared barocenes. X-ray structure determinations reveal that all the complexes studied are monomeric. Complexes 1, 7 and 8 were successfully tested in BaTiO3 thin film depositions by atomic layer deposition (ALD).

Journal Article↗

PubMed2003

Atomic layer deposition chemistry: recent developments and future challenges.

New materials, namely high-k (high-permittivity) dielectrics to replace SiO(2), Cu to replace Al, and barrier materials for Cu, are revolutionizing modern integrated circuits. These materials must be deposited as very thin films on structured surfaces. The self-limiting growth mechanism characteristic to atomic layer deposition (ALD) facilitates the control of film thickness at the atomic level and allows deposition on large and complex surfaces. These features make ALD a very promising technique for future integrated circuits. Recent ALD research has mainly focused on materials required in microelectronics. Chemistry, in particular the selection of suitable precursor combinations, is the key issue in ALD; many interesting results have been obtained by smart chemistry. ALD is also likely to find applications in other areas, such as magnetic recording heads, optics, demanding protective coatings, and micro-electromechanical systems, provided that cost-effective processes can be found for the materials required.

Journal Article↗

PubMed2002

Synthesis, crystal structure and initial biological evaluation of the new enantiomerically pure chiral palladium(II) complex trans-bis[endo-(1R)-1,7,7-trimethylbicyclo[2.2.1]-heptan-2-amino]palladium(II)dichloride.

The palladium(II) complex trans-bis[(R)-(+)-bornylamino]palladium(II) dichloride was synthesised and characterised. The solid state structure of the complex was determined by X-ray structure analysis. The compound crystallises in the monoclinic space group P2(1) with a=12.383(2), b=23.689(5), c=12.769(3) A, beta=93.25(3) degrees, and V=3739.6(13) A(3). The complex was tested for its cytotoxicity against L(929), K(562) and HeLa cell lines using the MTT assay technique. It is also tested for its anticomplementary activity using a test that detects complement proteins inhibition. These activities were compared with those of the reference standards, cisplatin, carboplatin and oxaliplatin. The significance of these results is given and discussed.

Antineoplastic Agents↗

PubMedDate not supplied

Parallel screening of homogeneous copper catalysts for the oxidation of benzylic alcohols with molecular oxygen in aqueous solutions.

A simple and efficient parallel screening method to evaluate the catalytic activities of homogeneous copper complexes for the oxidation of benzylic alcohols in aqueous solutions with molecular oxygen is reported. Copper(II) sulfate was treated in situ with 22 nitrogen donor ligands, and the catalytic activities of these combinations were studied at four different pH values with two substrates (benzyl alcohol and 3,4-dimethoxy benzyl alcohol (veratryl alcohol)), resulting in 176 oxidation experiments in the primary screening stage. Copper complexes based on N,N,N',N'-tetramethyl ethylenediamine (TMEDA), 9,10-diaminephenanthrene (DAPHEN), and 1,2-diaminocyclohexane (DACH) were determined to be the most active catalysts. In the second screenings, the influence of reaction conditions on Cu(DACH)-, Cu(TMEDA)-, and Cu(DAPHEN)-catalyzed reactions were investigated in more detail. It was found that highly basic reaction conditions favor the reaction with the exception of Cu(TMEDA), which is active at a lower pH range. Under optimized conditions, Cu(DAPHEN) catalyzes the transformation of veratryl alcohol to the corresponding aldehyde with 100% conversion.

Journal Article↗