Nanoporous Anodic Alumina for Optofluidic Applications

Selective and Sensitive Probe Based in Oligonucleotide-Capped Nanoporous Alumina for the Rapid Screening of Infection Produced by Candida albicans

A robust, sensitive, and time-competitive system to detect Candida albicans in less than 30 min in clinical samples based in capped nanoporous anodic alumina (NAA) is developed. In the proposed design, NAA pores are loaded with rhodamine B and then blocked with an oligonucleotide that is able to recognize C. albicans DNA. The capped material shows negligible cargo release, whereas dye delivery is selectively accomplished when genomic DNA from C. albicans is present. This procedure has been successfully applied to detect C. albicans in clinical samples from patients infected with this yeast. When compared with classical C. albicans detection methods, the proposed probe has a short assay time, high sensitivity and selectivity, demonstrating the high potential of this simple design for the diagnosis of infection produced by C. albicans.

Spontaneous water adsorption-desorption oscillations in mesoporous thin films

Understanding fluid transport and phase changes in nanopore structures is of great interest to many application fields, from energy conversion to water harvesting. This work discusses the spontaneous oscillations of the water saturation of mesoporous thin films, in the zone adjacent to a sessile water drop, at ambient conditions. The wetting-front dynamics onto the film is described by considering three coexisting phenomena: infiltration from the water drop, condensation from air vapor, and evaporation to the ambient. It was found that the oscillations follow spontaneous condensation-evaporation imbalances, which are governed by the hysteretic character of the adsorption-desorption behavior of the mesoporous material. The outcomes of this work provide insights on the complex interplay between water and nanopore structures, which has practical implications for the handling of humid microenvironments in lab-on-a-chip technology, as well as for many processes that take part of the cycle of water in nature.

Molecular gated nanoporous anodic alumina for the detection of cocaine

We present herein the use of nanoporous anodic alumina (NAA) as a suitable support to implement "molecular gates" for sensing applications. In our design, a NAA support is loaded with a fluorescent reporter (rhodamine B) and functionalized with a short single-stranded DNA. Then pores are blocked by the subsequent hybridisation of a specific cocaine aptamer. The response of the gated material was studied in aqueous solution. In a typical experiment, the support was immersed in hybridisation buffer solution in the absence or presence of cocaine. At certain times, the release of rhodamine B from pore voids was measured by fluorescence spectroscopy. The capped NAA support showed poor cargo delivery, but presence of cocaine in the solution selectively induced rhodamine B release. By this simple procedure a limit of detection as low as 5 × 10-7 M was calculated for cocaine. The gated NAA was successfully applied to detect cocaine in saliva samples and the possible re-use of the nanostructures was assessed. Based on these results, we believe that NAA could be a suitable support to prepare optical gated probes with a synergic combination of the favourable features of selected gated sensing systems and NAA.