Nanomaterials-Based Sensing Platforms

Towards the Efficient Detection of Biomolecules and Gases

Aneeya K. Samantara, Sudarsan Raj, Satyajit Ratha, Aneeya K. Samantara, Sudarsan Raj, Satyajit Ratha

• Publisher: Apple Academic Press
• Year: 2022
• ISBN:
  9781000427783
• Edition: 1
• Topic: Tecnologia e ingegneria
• Subtopic: Nanotecnologia e MEMS

Sensors are effective tools used to carry out cost-effective, fast, and reliable sensing for a wide range of applications. This volume presents a brief history behind sensing technology and highlights a broad range of biosensing techniques based on optical and electrochemical response methods. Starting from the traditional enzyme-based biosensing method to functionalized nanostructure-based sensors, this book also provides a detailed overview of some of the advanced sensing methodologies based on photonic crystal cavity-based sensing devices.

The authors showcase the extraordinary success of nanomaterials, their current strategical exploitation, and an unprecedented pool of possibilities they hold for the future. Many of the technologies have been developed recently for the sensing of various bioanalytes and molecules, some of which have been included in this book through dedicated chapters. The book looks at various sensors, such as for biosensing, electrochemical sensing, gas sensing, photoelectrochemical sensing, and colorimetric sensing, all of which have shown vast potential.

CHAPTER 1 Biosensors: Current Trends and Future Perspectives

SABYASACHI DASH¹ and SANDEEP KAUSHIK²

¹Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York–10065, USA, E-mail: [email protected]

²I3Bs-Research Institute on Biomaterials, Biodegradables, and Biomimetics, University of Minho, Barco, Guimarães, Portugal

ABSTRACT

A biosensor is an analytical device employed to sense analytes and associated changes in a given biochemical environment. The output is interpreted in the form of electronic signals read by an appropriate recognition system and an electrochemical transducer. The past few decades have witnessed the evolution of biosensors as well recognized sensitive and selective devices to record subtle changes in analytes of a various chemical or biological system. Due to such potential, biosensors have been implemented across disciplines of pure and applied sciences in some form or the other. Since their birth in the early 1960s, Extensive research and development has happened globally to enhance our existing knowledge on these devices. However, only a handful of biosensors have been commercialized and actively used, for example, the glucose monitors and pregnancy test kits. This chapter will provide details on the inception, evolution, current applications and the probabilistic future of this technology in the context of human health and disease.

1.1 BIOSENSORS AND THEIR UNDERLYING PRINCIPLE

1.1.1 HISTORICAL PERSPECTIVE ON THE BIRTH OF BIOSENSORS

In simple words, Biosensors can be defined as analytical devices that convert a biological or biochemical response to an electronic output. Biosensors have witnessed remarkable progress since their inception. Within the past 40 years, the direct or indirect applications of biosensors supported by research in both pure and applied sciences have established the impact of these devices. The history of biosensors dates to as early as the year 1906 when M. Cremer demonstrated that the concentration of an acid in a liquid is proportional to the electric potential between parts of the fluid located on opposite sides of a glass membrane (Cremer, 1906). Later, Søren Peder Lauritz Sørensen introduced the concept of pH, percentage of hydrogen ion concentration, in 1909, and an electrode for pH measurements was published in the year 1922 by W. S. Hughes. Between 1909 and 1922, Griffin and Nelson demonstrated enzyme immobilization on a surface of aluminum hydroxide and charcoal (1916). In 1956 Professor LeLand C. Clark, also known as the “father of biosensors,” published his work on the development of the first true biosensor, an oxygen probe that could sense the changing oxygen concentrations in a given biochemical environment (2006). This electrode was named as “Clark Electrode” after Professor Clark (Heineman et al., 2006). Employing this invention, the first demonstration was performed using a dialysis membrane containing the enzyme glucose oxidase (GO_x) wrapped over the oxygen detection probe. In this demonstration, observers witnessed the ability of the probe to detect the changes in oxygen concentration in proportion to the activity of the enzyme GO_x (Heineman et al., 2006; Bhalla et al., 2016). Thus, the first biosensor was an “enzyme electrode” marking the activity observed during the scientific demonstration (Heineman et al., 2006; Bhalla et al., 2016). Later in 1967, Updike and Hicks used a similar principle employing the immobilization of enzyme GO_x in a gel (polyacrylamide gel) onto the surface of an oxygen electrode to facilitate rapid quantitative measurement of oxygen concentration (Bhalla et al., 2016). Soon, this innovation sparked a great interest and curiosity in the global scientific community. Only 2 years later, Guilbault and Montalvo developed glass electrode-based sensors to measure urea concentration (Guibault and Montalvo, 1969). Subsequently, from 1970 several authors began accepting and reproducing the idea of biosensors, based on the coupling of enzyme and electrochemical sensors. A new set of sensors were proposed in 1971-based on a novel principle called ion-selective electrode (ISE) to detect the activity of beta-glucosidase enzyme for the formation of benzaldehyde and cyanide (Rechnitz and Llenado, 1971). This marked a transformative approach in the field where researchers attempted to employ various targets as receptors including, tissues, microorganisms, cellular organelles, cell surface receptors, enzymes, antibodies, nucleic acids, etc. (Bhalla et al., 2016). On the other hand, probable transducers included, electrochemical, optical, thermometric, magnetic, and others (Bhalla et al., 2016).

1.1.2 BIOSENSORS FOR DISEASE

The progress made within a decade of the first “biosensor” led the scientific and medical community to collaborate towards a common idea-Can these “biosensors” or sensing devices be used in detection and diagnosis of various human diseases? Little did the scientific community foresee the power of these simple yet innovative devices during that time. Nevertheless, the idea majorly focused towards developing simplified, cost-effective and user-friendly devices. Due to this, biosensor technology has continued to evolve into an ever-expanding and multidisciplinary domain of innovation-driven science since its birth.

1.1.3 SENSORS VS. BIOSENSORS: WORKING PRINCIPLE

The working principle of a biosensor could be imagined similar to that of a classical sensing device (Figure 1.1(A)). Hence, the question is-What exactly is unique about biosensors and how different they are from the conventional sensing devices? Thus, it is important to gain a deeper insight to their structural components which makes them of functionally unique. The functional anatomy of a conventional sensing device includes components that will involve a sensing unit, a converter unit to convert the sensed signal into a digital format, and a display unit to interpret this converted signal to a user-friendly readable format (Figure 1.1(A)). So, to begin with the first component is a sensor: a device that can sense physical changes including, temperature, mass, humidity, light, and pressure. This change measured and captured by the sensor is analog in nature. To ensure proper interpretation, it is important to change the analog signal into a specific electronic potential difference termed as “voltage.” This analog signal is sensitive to fluctuations and constant changes that can be captured using a transducer, the second component of the sensing device. The transducer enables analog to digital (A/D) signal conversion that is efficient enough to capture and convert even the smallest of fluctuations in the analog readings. The transducers can be semiconductors, diodes or transistors (for temperature changes), capacitors (to measure pressure changes) or photodiodes or photoresistors (to detect light-based changes) (Yoon, 2016). Thereafter, the recorded signal is processed with a network of electronic components constituting an amplifier to capture signal changes, an electronic processor and a readable display unit to record the changes detected by the user (Figure 1.1(A)).

FIGURE 1.1 Schematic representations of functional components of biomolecule sensing devices. (A) Classical sensing device-sensor senses the charge-based changes in environment which are recorded by the transducer in connection. Thereafter, the transducer signals the charge recorded to the electronic unit for subsequent processing of data. (B) Design of a biosensor-sensors can include biomolecules to microorganisms which recognize the changes-based on the environment or specific analyte. The signal is thereafter processed by the specific type of transducer-based on the sensing method and transferred to the electronic unit for data processing and analysis.

Source: Adapted with permission from: Bhalla, Jolly, Formisano, and Estrela (2016).

Although, the overall structure of a biosensor primarily overlaps with the principle of a general sensing device as described above however it differs significantly with a few unique features (Figure 1.1(B)). For example, the sensor used in a “biosensor” module is a sensitive biochemical element called bioreceptor, also otherwise known as a biomimetic material (Figure 1.1(B)). Bioreceptors prove superior in determining the differences in biochemical analytes (tissue changes, microbes, nucleic acid changes, etc.), which the conventional sensors (for temperature, pressure, etc.), fail to detect (Bhalla et al., 2016; Yoon, 2016). For example, to detect E. coli in a given sample, a voltage signal will be generated only when the bioreceptor (for instance, anti-E. coli antibody) will recognize and bind to the bacteria. As of today, the commonly used bioreceptors include nucleic acids (DNA, RNA) and antibodies that target proteins of interest. Second, the transducer of a biosensor primarily features electrochemical (measures voltage differences), optical, thermal (change of temperature) and piezoelectric (to measure antigens, nucleic acids, biomolecules, enzymes) (Yoon, 2016). Like the conventional sensing device, the third unit is the electronic module comprising of the electronic unit to record the changes detected by the user (Figure 1.1(B)).

1.2 CHARACTERISTICS OF A BIOSENSOR

A biosensor constitutes of unique components integral for its function. Therefore, the device should include components that harness optimized properties for the efficient detection of the analyte and its associated changes with minimal error.

1.2.1 SPECIFICITY AND SELECTIVITY

Selectivity and specificity enable a bioreceptor to detect a specific analyte in a given sample containing various biomolecules and other constituents (Yoon, 2016; Holzinger and Goff, 2014). One can imagine the interaction of an antigen with the antibody which is of very specific and selective in nature. Considering this example, antibodies can be considered as bioreceptors that are clamped (attached) on the transducer’s surface. A buffering solution (containing salts) with the antigen when exposed to the transducer allows the antibodies to interact only with its target antigens (Yoon, 2016). Hence, these features are an important consideration for designing of a biosensor.

1.2.2 PRECISION AND ACCURACY

Precision ensures to provide similar results each time an analyte is measured while accuracy ensures the digital readings obtained with a mean value nearest to the true value when an analyte is measured in multiple replicates (Bhalla et al., 2016). This property is further characterized by the reproducibility to generate identical responses for experiments conducted in replicates. Such properties are very much dependent on the quality of transducer and electronic components used in the given biosensor. Therefore, the accuracy in the obtained signals or digital readings provides high reliability and robustness towards the functioning of a biosensor.

1.2.3 LINEAR RANGE OF SENSING

The linearity or linear range of a biosensor can be defined as the range of analyte concentration changes to which the biosensor responds linearly. It is the feature that is indicative of the accuracy of the detected changes in the analyte (Gupta et al., 2017). This unique property of the biosensor helps to recognize the smallest of any change associated with the analyte during a given response of the biosensor (Gupta et al., 2017).

1.2.4 BIOSENSING STABILITY

Stability defines the degree of susceptibility to ambient changes occurring within the vicinity of the biosensing system (Bhalla et al., 2016; Yoon, 2016; Gupta et al., 2017). These changes can potentially induce drifts or biases in the output signal during measurement of analyte-associated changes. This results in error in the end results obtained. Stability of a biosensor also helps to record changes with the analyte in long experimental conditions. Factors including the functioning of transducers and electronics, affinity of the bioreceptor (interaction between analyte and bioreceptor) may influence the stability of a biosensor. Therefore, appropriate tuning of electronics is required to ensure a stable response of the sensor.

1.2.5 SENSITIVITY

The sensitivity of a biosensor defines its ability to detect the least amount of analyte and associated changes (Gupta et al., 2017). This is important since the concentrations of various analytes occur in the range of nanograms to femtograms in a given biological system.

1.3 TYPES OF BIOSENSOR...