Cadmium Stannate Films for Immobilization of Phospholipid Bilayers

Abstract

Cadmium tin oxide (CTO) films on glass substrates were synthesized and functionalized by octadecyltrichlorosilane (OTS). CTO films were transparent with the bandgap of 2.92 eV. They exhibited n-type conductivity and carrier concentration of (3.31 ± 0.38) · 1019 cm−3. Weak temperature dependence points out to a nearly degenerative state of the carriers in the CTO films. Silanization by OTS yielded hydrophobic surface with the contact angle values reaching 103 ± 12 degrees. Silanization of films was followed by a significant reduction of the interfacial capacitance, which upon completion of the functionalization reached levels below 3 μF cm−2. The value of the electric capacitance as well as data of ATIR absorption, hints at sparse and disordered coverage of the CTO surface by octadecylalkylsilane molecules. Such organic layer, however, was able to trigger phospholipid (60% dioleoylphosphocholine and 40% cholesterol) vesicle rupture and the formation of a secondary layer of phospholipid, thus rendering hybrid bilayer surface construct. Such hybrid constructs may be useful in applications where electrode coupling to a model biological membranes and membrane bound proteins is required, such as biosensing and photovoltaics.

Formation of mixed hybrid bilayer lipid membrane on transparent thin film oxide electrodes

“…Therefore, CA data showed that increasing short alkylchain VTS in the silanisation solution, decreases the contact angle on the silanised FTO surface accordingly to the spacer unit molar ratio in the silanisation solution. A similar tendency in CA evolution is observed on gold electrodes, using a mixture of a spacer unit and long alkylchain thiols [7]. The silanisation of FTO surface with OTS:VTS 4:6, 6:4, 8:2 and 10:0 molar ratios causes CA values to reach higher than 100° value.…”

“…The procedure of vesicles solution preparation was done according to the previously published papers [7,11]. Briefly, the vesicle solution was made by mixing 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) (Avanti Lipids Alabaster, USA) and cholesterol (Avanti Lipids Alabaster, USA) in molar ratio 6:4 in a phosphate buffer solution (PBS) pH 4.5 (0.1 M NaCl (Reachem Slovakia p.…”

“…To assemble both hybrid and tethered bilayers various solid supports are used: sputtered Au and Ti/TiO 2 [1][2][3], polished Ti [4], Si/SiO 2 [5], SnO 2 doped with either fluorine, cadmium or indium [6][7][8], aluminium [9,10]. Most of these surfaces (except for SiO 2 ) exhibit a good electric conductance, thus providing application of the electrochemical techniques for protein membrane interaction studies.…”

“…Previously, we have shown that tin oxide substrate could be successfully silanised for phospholipid bilayer formation [6,7] using octadecyltrichlorosilane SAM with a subsequent vesicle fusion and formation of 60 mol% 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/40 mol% cholesterol bilayer. However, such solid supported membranes exhibited hybrid bilayer properties, which precluded the reconstitution of transmembrane poreforming proteins.…”

Hybrid bilayer membranes on metallurgical polished aluminum

“…Gold 34 as a substrate has been most extensively studied for the formation of bilayer lipid membranes but other surfaces are viable choice as well e.g. silica 36 , indium tin oxide (ITO) 37 , fluorine-doped tin oxide (FTO) 38 , cadmium tin oxide (CTO) 39 , Ti/TiO 2 40 – 42 , aluminum 43 – 46 , etc. In the majority of these cases, such surfaces require special preparation techniques e.g.…”