Label Free Biosensing

This volume summarizes the state-of-the-art technologies, key advances and future trends in the field of label-free biosensing. It provides detailed insights into the different types of solid-state, label-free biosensors, their underlying transducer principles, advanced materials utilized, device-fabrication techniques and various applications. The book offers graduate students, academic researchers, and industry professionals a comprehensive source of information on all facets of label-free biosensing and the future trends in this flourishing field. Highlights of the subjects covered include label-free biosensing with: · semiconductor field-effect devices such as nanomaterial-modified capacitive electrolyte-insulator-semiconductor structures, silicon nanowire transistors, III-nitride semiconductor devices and light-addressable potentiometric sensors · impedimetric biosensors using planar and 3D electrodes · nanocavity and solid-state nanopore devices · carbon nanotube and graphene/graphene oxide biosensors · electrochemical biosensors using molecularly imprinted polymers · biomimetic sensors based on acoustic signal transduction · enzyme logic systems and digital biosensors based on the biocomputing concept · heat-transfer as a novel transducer principle · ultrasensitive surface plasmon resonance biosensors · magnetic biosensors and magnetic imaging devices

A detailed technical review of label-free biosensor techniques with worked examples.

This book is dedicated to label-free, non-invasive monitoring of cell-based assays and it comprises the most widely applied techniques. Each approach is described and critically evaluated by an expert in the field such that researchers get an overview on what is possible and where the limitations are. The book provides the theoretical basis for each technique as well as the most successful and exciting applications. Label-free bioanalytical techniques have been known for a long time as valuable tools to monitor adsorption processes at the solid-liquid interface in general – and biomolecular interaction analysis (BIA) in particular. The underlying concepts have been progressively transferred to the analysis of cell-based assays. The strength of these approaches is implicitly given with the name 'label-free': the readout is independent of any label, reagent or additive that contaminates the system under study and potentially affects its properties. Thus, label-free techniques provide an unbiased analytical perspective in the sense that the sample is not manipulated by additives but pure. They are commonly based on physical principles and read changes in integral physical properties of the sample like refractive index, conductivity, capacitance or elastic modulus to mention just a few. Even though it is not implied in the name, label-free approaches usually monitor the cells under study non-invasively meaning that the amplitude of the signal (e.g. electric field strength, mechanical elongation) that is used for the measurement is too low to interfere or affect. In contrast to label-based analytical techniques that are commonly restricted to a single reading at a predefined time point, label-free approaches allow for a continuous observation so that the dynamics of the biological system or reaction become accessible.

This thesis describes novel substrate embedded physical sensors that can be used to monitor different types of cell-based assays non-invasively and label-free. The sensors described provide integrative information of the cells under study with an adaptable time resolution (ranging from milliseconds to days). This information about the dynamic cell response to chemical, physical or biological stimuli defines a new paradigm in fundamental biomedical research. The author, Maximilian Oberleitner, describes approaches in which the cells are directly grown on different sensor surfaces (gold-film electrodes, shear wave resonators or dye-doped polymer films). This approach, with the reacting cells in particularly close proximity and contact with the sensor surface, is key to a remarkable sensitivity, opening the way for a variety of new applications. This thesis not only introduces the fundamentals of each approach, but it also describes in great detail the design principles and elucidates the boundary conditions of the new sensors.

Over the past decade, we have witnessed significant advancements in the label-free biosensing field. Label-free biosensors aim at detecting the target molecules or biological processes without labels, thus allowing evaluation of their intrinsic properties in their natural forms, as well as easy operations without sophisticated pre-treatments of samples, which has drawn more and more attention in biological studies and rapid clinical tests. The main challenges include two aspects. First, the measurement system should be sensitive enough to detect the tiny signals corresponding to the specific target properties. Second, the signal processing protocols should be able to recognize the signals from the complex background. Owing to the great advances of commercial detection components with high sensitivity, more and more ingenious but economic label-free biosensors have been presented for diverse applications. This Special Issue, entitled "Label-free Biosensors", focuses on recent advances in producing sensitive and easy-to-use label-free biosensors and their applications in diverse fields. This collection presents several novel label-free detection techniques to introduce design strategies and operation protocols in practical application, which might be of particular value to beginners and graduate students who have just entered this field.

The present book is devoted to all aspects of biosensing in a very broad definition, including, but not limited to, biomolecular composition used in biosensors (e.g., biocatalytic enzymes, DNAzymes, abiotic nanospecies with biocatalytic features, bioreceptors, DNA/RNA, aptasensors, etc.), physical signal transduction mechanisms (e.g., electrochemical, optical, magnetic, etc.), engineering of different biosensing platforms, operation of biosensors in vitro and in vivo (implantable or wearable devices), self-powered biosensors, etc. The biosensors can be represented with analogue devices measuring concentrations of analytes and binary devices operating in the YES/NO format, possibly with logical processing of input signals. Furthermore, the book is aimed at attracting young scientists and introducing them to the field, while providing newcomers with an enormous collection of literature references.