Dear Colleagues,

The COVID-19 pandemic has evidenced the pressing need to develop fit-for-purpose diagnostics that can be deployed onsite soon after the identification of a health threat. This urgency applies not only to healthcare but also other fields, such as environmental monitoring and food safety, in which robust, fast, reliable, and accurate diagnostics is required. Biosensors have often been developed as powerful alternatives to laboratory-based diagnostic techniques due to their high sensitivity, simplicity, cost-effectiveness, and point-of-care potential. Nonetheless, the intensive research efforts devoted to their development have only occasionally led to technology adoption. There are several reasons for that but, most likely, the limitations in technology translation come from their often poor reproducibility and reliability, lack of demonstration with real samples due to limitations caused by matrix effects, and difficulties in their fabrication and adaptation to user-friendly prototypes with limited sample processing steps.

In recent years, various strategies have been used to tackle setbacks in translation of the scientific and technological knowledge acquired in biosensors into cost-effective, versatile, and highly efficient commercial diagnostics. Among them, the incorporation of nanotechnological concepts in sensor design has spurred multiple research works harnessing the advantages provided by certain nanomaterials.

The incorporation of nanoporous materials into the design of biosensors has generated a new class of tools exceeding the analytical performance of their planar counterparts. Their large surface area not only enhances bioreceptor immobilization, but also facilitates rapid interaction with the analyte. The possibility of creating various pore architectures and tuning their physical properties, such as pore diameter and depth and porosity, opens a wealth of opportunities for sensing. Indeed, the use of porous materials, such as porous silicon and porous alumina, as photonic structures suitable for label-free biosensing has been a leap forward in the evolution of optical biosensors. Additionally, the possibility to modulate the electrical properties of some of these nanoporous materials has been critical for developing a wide range of electrical and electrochemical biosensors, some of them exploiting sensing mechanisms inspired from principles found in nature. Here, the design of so-called solid-state ion channels that mimic the selective transport of natural ion channels in living organisms is key. The potential to control their surface chemistry and the possibility to finetune their morphology to support infiltration of desired molecules based on their size, while excluding larger molecules that might act as signal interferents, have led to a turning point in the way biosensors deal with matrix effects when challenged with complex clinical, environmental, or food samples. Other advantages attributed to some of these nanoporous materials include their biocompatibility, compatibility with semiconductor processing, and the possibility to easily scale up their fabrication process. All these advantages pave the way to a new flourishing field of diagnostics designed to meet the WHO ASSURED criteria of being affordable, sensitive, specific, user-friendly, robust, equipment-free, and deliverable to end-users. It is expected that advances in the synthesis of nanoporous materials, smart methods for site-specific modification, and engineering of new sensing mechanisms will unlock new paths in the translation of biosensors to match end-user requirements.

This Special Issue aims to cover recent advances in the development of biosensors built on nanoporous structures, highlighting the advantages provided by the nanoscale environment and describing future trends in their evolution toward outperforming diagnostics.

Dr. Beatriz Prieto-Simón
Guest Editor

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• biosensors
• porous materials
• porous silicon
• porous alumina
• porous polymeric membranes
• solid-state ion channels
• bioinspired materials
• photonic crystals
• pore-suspending membranes
• chemical functionalization