Sensor Array Made with Nanostructured Films to Detect a Phenothiazine Compound

Abstract

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.

On the distinct molecular architectures of dipping- and spray-LbL films containing lipid vesicles

“…The differences resulting from the distinct molecular architectures are corroborated by the PCA plots obtained with the capacitance taken at a fixed frequency for each sensing unit (1 kHz), similarly to previous works [10,32,52,57]. Fig.…”

“…7a shows a PCA plot where the combined response of the sensing units forming a sensor array can distinguish erythrosin solutions down to 1 nM. In order to assess the importance of each sensing unit for the overall high sensitivity, an empirical test was made in which PCA plots were obtained by eliminating one of the sensing units [38,52,57]. The plots were slightly affected when the excluded sensing unit was the Pt bare electrode or the Pt electrode coated with PAH/DPPG, PAH/PSS and DODAB/DPPG dipping LbL films (results not shown).…”

Incorporation of Ag nanoparticles into membrane mimetic systems composed by phospholipid layer‐by‐layer (LbL) films to achieve surface‐enhanced Raman scattering as a tool in drug interaction studies

“…Second, the same conclusion can be reached regarding the spatial distribution of the DPPG molecules taking into account the interaction between DPPG and MB. [29,31] Fig. 5(c) presents two MB SERRS spectra chosen from the Raman mapping shown in Fig.…”

Recent advances in electronic tongues

“…[32][33][34][35][36][37][38] Furthermore, using label-free detection processes is advantageous since uncertainties are removed which are associated with the effects of labels on molecular conformation, blocking of active binding sites, steric hindrance, and the inability to encounter available labels for specific molecules. [32][33][34][35][36][37][38] Furthermore, using label-free detection processes is advantageous since uncertainties are removed which are associated with the effects of labels on molecular conformation, blocking of active binding sites, steric hindrance, and the inability to encounter available labels for specific molecules.…”