Bio-Recognition in Spectroscopy-Based Biosensors for *Heavy Metals-Water and Waterborne Contamination Analysis.

biosensors Review Bio-Recognition in Spectroscopy-Based Biosensors for *Heavy Metals-Water and Waterborne Contamination Analysis Alessandra Aloisi 1,† , Antonio Della Torre 1,† , Angelantonio De Benedetto 2 and Rosaria Rinaldi 1,2,3, * 1 2 3 * † Institute for Microelectronics and Microsystems (IMM), CNR, Via Monteroni, 73100 Lecce, Italy Mathematics and Physics “E. De Giorgi” Department, University of Salento, Via Monteroni, 73100 Lecce, Italy ISUFI, University of Salento, Via Monteroni, 73100 Lecce, Italy Correspondence: These authors contributed equally to this work. Received: 12 June 2019; Accepted: 25 July 2019; Published: 30 July 2019



 Abstract: Microsystems and biomolecules integration as well multiplexing determinations are key aspects of sensing devices in the field of heavy metal contamination monitoring. The present review collects the most relevant information about optical biosensors development in the last decade. Focus is put on analytical characteristics and applications that are dependent on: (i) Signal transduction method (luminescence, colorimetry, evanescent wave (EW), surface-enhanced Raman spectroscopy (SERS), Förster resonance energy transfer (FRET), surface plasmon resonance (SPR); (ii) biorecognition molecules employed (proteins, nucleic acids, aptamers, and enzymes). The biosensing systems applied (or applicable) to water and milk samples will be considered for a comparative analysis, with an emphasis on water as the primary source of possible contamination along the food chain. Keywords: water pollution; environmental water; drinking water; milk; heavy metal ions; biosensor; detection limits; optical spectroscopy; proteins; functional nucleic acids 1. Introduction Biosensors are currently valid tools, other than laboratory analytical instrumentation, for monitoring the quality of natural water (e.g., in the food production chain) [1]. Biosensors are not meant to take over standard analytical methods, but, when optimal features of a sensing device are met, they offer remarkable advantages over conventional techniques. Overall, in certain conditions, their promptness and low-cost manufacturing make them useful tools to analyze many samples for primary warnings. As defined by the International Union of Pure and Applied Chemistry (IUPAC), “a biosensor is an integrated receptor ± transducer device, capable of providing selective analytical information using a biological recognition element” [2]. Optical biosensors are a group of sensors in which (i) the transducer senses optical fluctuations in the input light resultant from bioreceptor—target interaction, and (ii) the amplitude of these changes hinge on the concentration of the analyte [1]. Even in very small amounts, several metal ions may have important effects on health state, as they are hardly degradable but easily accumulated in the body through the diet [3]. Metal ions are generally not essential nutrients; conversely, they could be damaging to all living species [4]. * Widely indicated as “heavy metals” (HMs), in a technical report of 2002, the author concluded: “The term heavy metal has never been defined by any authoritative body such as IUPAC. No relationship can be found between density and any of the various physicochemical concepts that have been used Biosensors 2019, 9, 96; doi:10.3390/bios9030096 www.mdpi.com/journal/biosensors Biosensors 2019, 9, 96 2 of 28 Biosensors 2019, 9, 96 2 of 29 to define heavyismetals and toxicity of attributed to heavy metalsIt .depends . . Understanding bioavailability bioavailability the key to the assessment the potential toxicity... on biological parameters is the key to assessment of the potential toxicity... It depends on biological parameters and on the and on the physicochemical properties of metallic elements, their ions, and their compounds. These physicochemical properties of metallic elements, their ions, and their compounds. These in turn depend in turn depend upon the atomic structure of the metallic elements, systematically described by the upon the atomic structure of the metallic elements, systematically described by the periodic table” [5]. periodic table” [5]. In the last twenty years, with the aim to quantify trace amounts of such possible contaminants, In the last twenty years, with the aim to quantify trace amounts of such possible contaminants, environmental monitoring monitoring has has generated generated aa need need for for innovative innovative and and improved improved approaches approaches that that have have environmental ever-increasing sensitivity and selectivity, as described in a recent review paper on various analytical ever-increasing sensitivity and selectivity, as described in a recent review paper on various analytical techniques-based biosensors biosensors [6]. [6]. The The introduction introduction of of biosensors biosensors has has brought brought in in new and promising techniques-based approaches, but stillstill limited application in thein environmental field if compared with the biomedical approaches, butwith with limited application the environmental field if compared with the one, where most efforts have converged in the past years. biomedical one, where most efforts have converged in the past years. Much research is still needed before biosensors consolidate as a recognized analytical strategy with respect to environmental and and food food trace trace contaminant contaminant detection. detection. In this direction, the integration of nanomaterials and functional biological molecules is part of Actually, nano-structured nano-structured materials materials unveil unveil distinctive distinctive sizesizea new era in the optical biosensor area. Actually, and shape-dependent physicochemical properties, showing a number of possible interactions [7] with shape-dependent physicochemical properties, showing a number of possible interactions [7] the biorecognition component, which may may act asact a reaction catalyst, or may in be equilibrium with with the biorecognition component, which as a reaction catalyst, or be may in equilibrium macromolecules present in theirinnatural biological settings or isolated engineered [2]. Essentially, with macromolecules present their natural biological settings orand isolated and engineered [2]. while the sensor sensitivity is influenced by the selected transducer component, the bioreceptor is Essentially, while the sensor sensitivity is influenced by the selected transducer component, the responsible for the specificity Many biosensing elements that can be coupledthat to different bioreceptor is responsible for[8]. the specificity [8]. Many biosensing elements can be transducers coupled to are now available for HM detection (Figure 1). different transducers are now available for HM detection (Figure 1). Figure 1. Optical Optical biosensor biosensor scheme scheme strategies strategies for for heavy heavy metal metal (HM) (HM) ion ion detecti (...truncated)