**About the Editors**

**Giovanna Marrazza** is a full professor in Analytical Chemistry at the Department of Chemistry "Ugo Schiff" of the University of Florence, Italy. She was the President of the Course of Study in Chemistry Degree at the same university from 2017 to 2021. She has been a distinguished Visiting Professor of the Faculty of Pharmacy "Iuliu Hat¸ieganu" University of Medicine and Pharmacy, Cluj-Napoca (Romania) since 2017.

She is a member of the steering board of Italian Sensors and Microsystems Group (AISEM) and Italian Sensor Group, Italian Chemistry Society (SCI). Her research is focused on new biosensing principles containing nanomaterials and modified interfaces with nucleic acids, enzymes, antibodies, bacteria, and molecular imprinted polymers. She is an expert in the design of procedures suitable for biosensor devices such as microflow systems, thick-film technology, and nanodispensing technologies. She has contributed more than 138 papers in leading international journals and book chapters (H-index = 42, Scopus). She has been a unit leader in national and international projects, and has participated in further national and international projects.

**Sara Tombelli** Institute of Applied Physics, National Research Council (CNR), Italy. Sara Tombelli is a senior researcher at the Institute of Applied Physics (CNR) in Florence, Italy. Her research activity is focused on analytical chemistry, biosensor development and surface modifications with biomolecules, such as antibodies, enzymes, aptamers, and nucleic acid probes. She has experience in intracellular nanosensors and nanoparticle manipulation, as well as in the design and application of optical nanoprobes such as molecular beacons and oligonucleotidic optical switches. On the above topics, she has contributed more than 130 publications in international refereed journals, books, and conference proceedings (H-index = 38, Scopus). She is member of the Editorial Board of Sensors; she has been a Special Issue Editor for several MDPI journals and for the Elsevier journal Sensors and Actuators Reports. She has been part of international commissions as international expert for several international PhD theses (Spain, Switzerland, Italy). She participated in several European projects and in other national and international projects; she has been a unit leader in national projects and is responsible for several measurement campaigns in the frame of European projects.

#### **Preface to "Selected Papers from the 1st International Electronic Conference on Biosensors (IECB 2020)"**

The birth of biosensors dates back to the early 1960s, when Clark and Lyons (1962) introduced the concept of using an enzyme coupled with an electrode as a reagent. After decades of intense research, biosensors attracted the attention of a large scientific community, and they currently have a very wide range of applications due to their simplicity, low cost, and precision, aiming at improving quality of life. This range covers their use for environmental monitoring, disease detection, food safety, defense, drug discovery, and many more applications.

The scope of this Special Issue is to collect some of the contributions to the First International Electronic Conference on Biosensors, which was held to bring together well-known experts currently working in biosensor technologies from around the globe, and to provide an online forum for presenting and discussing new results.

The world of biosensors is definitively a versatile and universally applicable one, as demonstrated by the wide range of topics which were addressed at the Conference, such as: bioengineered and biomimetic receptors; microfluidics for biosensing; biosensors for emergency situations; nanotechnologies and nanomaterials for biosensors; intra- and extracellular biosensing; and advanced applications in clinical, environmental, food safety, and cultural heritage fields.

> **Giovanna Marrazza, Sara Tombelli** *Editors*

### *Article* **Light-Addressable Actuator-Sensor Platform for Monitoring and Manipulation of pH Gradients in Microfluidics: A Case Study with the Enzyme Penicillinase**

**Rene Welden 1,2,†, Melanie Jablonski 1,3,†, Christina Wege 4, Michael Keusgen 3, Patrick Hermann Wagner 2, Torsten Wagner 1,5,\* and Michael J. Schöning 1,5,\***


**Abstract:** The feasibility of light-addressed detection and manipulation of pH gradients inside an electrochemical microfluidic cell was studied. Local pH changes, induced by a light-addressable electrode (LAE), were detected using a light-addressable potentiometric sensor (LAPS) with different measurement modes representing an actuator-sensor system. Biosensor functionality was examined depending on locally induced pH gradients with the help of the model enzyme penicillinase, which had been immobilized in the microfluidic channel. The surface morphology of the LAE and enzymefunctionalized LAPS was studied by scanning electron microscopy. Furthermore, the penicillin sensitivity of the LAPS inside the microfluidic channel was determined with regard to the analyte's pH influence on the enzymatic reaction rate. In a final experiment, the LAE-controlled pH inhibition of the enzyme activity was monitored by the LAPS.

**Keywords:** light-addressable potentiometric sensor; light-addressable electrode; actuator-sensor system; enzyme kinetics; microfluidics
