Nanoporous anodic alumina (NAA) is a semiconductor material with interesting physical, mechanical, chemical and optical properties [1]. NAA is formed by the electrochemical etching of aluminum and presents a self-ordered hexagonal pore distribution with tunable pore diameters, pore lengths and interpore distances (figure 1) [2].

The high effective surface area of NAA (hundreds of m²/cm³) makes it a versatile and interesting platform for loading active agents like drugs or molecules as pores are used as reservoirs [3]. Based on this principle, we present here the use of NAA to develop advanced drug delivery systems and gated materials for biosensing applications.

The development of a new generation of local and selective drug delivery platforms with sustained release profiles is necessary to overcome the disadvantages of conventional treatments (generally oral or intravenous administrations) with considerable adverse effects [4]. The high effective surface area of NAA makes it an ideal material for drug delivery applications: the pores are nanocontainers with regular and controlled structural characteristics where active agents like drugs or molecules can be loaded [5]. Besides, the surface of NAA can be easily functionalized to be selective for specific molecules and covered with biodegradable, chemical, or pH responsive agents to trigger and regulate the release [6].

The pore geometry is one of the most important factors for the drug loading and for the release profile. Three-dimensional pore structures, with complex pore geometries and increasing surface area are promising morphologies for sustained drug release. However, their fabrication can be expensive and difficult. NAA, readily and cost-effectively fabricated by electrochemical anodization, permits obtaining elaborate and reproducible three dimensional pore geometries for sustained drug release platforms (figure 1) [7].

The biosensors we propose also follow the same concept of nanocontainer-pores introduced for the drug delivery systems. They consist of a NAA platform where the pores are loaded with a fluorophore and blocked by selected molecules that are able to recognize selectively a certain target analyte. The presence of the analyte unblocks the pores resulting in the selected release of the entrapped reporter. These gated biosensors based on NAA have high potential for the selective and sensitive detection of molecules that currently require complex and/or long processing. These nanostructured biosensors are very simple to prepare, easy to handle, reusable, and do not require trained personnel. We report here the use of these NAA biosensors for the selective detection of drugs and bacteria