RESUMO
Gold nanoparticles are valuable photothermal agents owing to their efficient photothermal conversion, photobleaching resistance, and potential surface functionalization. Herein, we combined bioinspired membranes with in vitro assays to elicit the molecular mechanisms of gold shell-isolated nanoparticles (AuSHINs) on ductal mammary carcinoma cells (BT-474). Langmuir and Langmuir-Schaefer (LS) films were handled to build biomembranes from BT-474 lipid extract. AuSHINs incorporation led to surface pressure-area (π-A) isotherms expansion, increasing membrane flexibility. Fourier-transform infrared spectroscopy (FTIR) of LS multilayers revealed electrostatic AuSHINs interaction with head portions of BT-474 lipid extract, causing lipid chain disorganization. Limited AuSHINs insertion into monolayer contributed to hydroperoxidation of the unsaturated lipids upon irradiation, consistently with the surface area increments of ca. 2.0%. In fact, membrane disruption of irradiated BT-474 cells containing AuSHINs was confirmed by confocal microscopy and LDH leakage, with greater damage at 2.2 × 1013 AuSHINs/mL. Furthermore, the decrease in nuclei dimensions indicates cell death through photoinduced damage.
Assuntos
Carcinoma , Nanopartículas Metálicas , Nanopartículas , Humanos , Ouro/química , Nanopartículas/química , Linhagem Celular Tumoral , LipídeosRESUMO
Thin films of cobalt phthalocyanine (CoPc) were deposited onto solid substrates through physical vapor deposition (PVD) by thermal evaporation up to 60 nm thick to determine their molecular architecture and electrical properties. The growth was monitored using UV-Vis absorption spectroscopy, revealing a linear increase for absorbance versus thickness. PVD films were found in the crystalline alpha phase and with the CoPc molecules forming ca. 45 degrees in relation to the substrate surface. The film surface was fairly homogeneous at the micro and nanoscales, with the roughness at ca. 3 nm. DC and AC electrical measurements were carried out for devices built with distinct structures. Perpendicular contact was established by depositing 60 nm CoPc PVD films between indium tin oxide (ITO) and Al, forming a sandwich-type structure (ITO/CoPc/Al). The current versus DC voltage curve indicated a Schottky diode behavior with a rectification factor of 4.2. The AC conductivity at low frequencies increased about 2 orders of magnitude (10(-9) to 10(-7) S/m) with increasing DC bias (0 to 5 V) and the dielectric constant at 1 kHz was 3.45. The parallel contact was obtained by depositing 120 nm CoPc PVD film onto interdigitated electrodes, forming an IDE-structured device. The latter presented a DC conductivity of 5.5 x 10(-10) S/m while the AC conductivity varied from 10(-9) to 10(-1) S/m between 1 Hz and 1 MHz, respectively, presenting no dependence on DC bias. As proof-of-principle, the IDE-structured device was applied as gas sensor for trifluoroacetic acid (TFA).
RESUMO
The detection of trace amounts of phenothiazines with fast, direct methods is important for medical applications and the pharmaceutical industry. In this paper we explore the concept of an electronic tongue to detect methylene blue (MB), with a sensor array comprising 6 units. These units were a bare Pt electrode, and Pt electrodes coated with 1-layer LB films of dipalmitoyl phosphatidylcholine (DPPC) and dipalmitoyl phosphatidylglycerol (DPPG), a 5-layer LB film of stearic acid, and 10 nm PVD films of bis benzimidazo perylene (AzoPTCD) and iron phthalocyanine (FePc). The electrical response obtained with impedance spectroscopy varied with the sensing unit, in spite of the small film thickness, thus indicating good cross-sensitivity. Upon treating the capacitance data at 1 kHz with Principal Component Analysis (PCA), the sensor array was capable of distinguishing MB solutions from ultrapure water down to 1 nM. This unprecedented high sensitivity was probably due to strong interactions between MB and DPPC and DPPG, as the sensing units of these phospholipids gave the most important contributions to the PCA plots. Such strong interaction was not manifested in the surface pressure-area isotherms of co-spread monolayers of MB and DPPC or DPPG, which emphasizes the high sensitivity of the electrical measurements in ultrathin films in contact with liquids, now widely exploited in electronic tongues.