Sustainable biosensing for water security: A review of technologies for heavy metal detection in wastewater

06/11/2025

Abstract

Increased industrialization has led to the widespread contamination of wastewater with toxic heavy metals, creating significant risks for public health and environmental stability and directly challenging the achievement of the United Nations’ Sustainable Development Goal (SDG) 6 (Clean Water and Sanitation). While precise, conventional laboratory-based methods for detecting these pollutants are often too costly, slow, and complex for the rapid, on-site monitoring required for effective environmental management. This technological gap hinders timely progress toward global water safety targets. This paper provides a comprehensive review of recent advancements in biosensor technologies, aiming to highlight their potential as a sustainable and cost-effective tool to support the achievement of water- and environment-related SDGs. The research method involves a systematic review of current scientific literature, examining the fundamental principles, classifications, and components of various biosensor systems. The analysis focuses on case studies that utilize novel biorecognition elements and nanomaterials to improve performance and sustainability. The principal findings indicate that biosensor technology has advanced significantly, achieving high sensitivity for detecting key heavy metals. The development of eco-biosensors using biodegradable components aligns with SDG 12 (Responsible Consumption and Production) by minimizing waste. These technologies also support SDG 13 (Climate Action) by reducing the energy consumption of traditional analyses and contribute to protecting ecosystems as targeted by SDG 14 (Life Below Wate) and SDG 15 (Life on Land). In conclusion, biosensors offer a transformative approach to environmental monitoring that directly supports the broader goals of sustainable development. Although challenges in mass production, long-term stability, and regulatory validation persist, overcoming these hurdles will enable the widespread deployment of biosensor systems as a critical tool for achieving global clean water and sustainability goals.

1. Introduction

Water is integral to the achievement of the United Nations’ Sustainable Development Goals (SDGs), serving as a critical resource that underpins societal progress [1]. Over the years, escalating urbanization and industrialization have led to an increasing demand for water, consequently resulting in substantial wastewater discharge into the environment. In 2022, roughly 42% of global domestic wastewater was released without adequate treatment, amounting to 113 billion m³/year [2]. In low-income countries only 8 % of wastewater receives treatment, compared with 70% in high-income countries. Wastewater sources are broadly categorized into point and non-point sources. Sources of wastewater are typically classified as either point sources, which are specific, identifiable locations like industrial outlets or sewage plants, or non-point sources, such as diffuse agricultural and urban runoff, the latter being more difficult to manage. The complex composition of wastewater, laden with inorganic and organic compounds, HMs, and emerging pollutants like microplastics, antibiotics, endocrine disruptors, and perfluoroalkyl and polyfluoroalkyl substances (PFAS), exacerbates freshwater scarcity by degrading both its quantity and quality [3, 4]. Industrial effluents frequently contain elevated levels of HMs pollutants [5].  Exceeding these limits causes neurotoxicity, kidney damage and cancer in humans as well as reproductive and growth impairments in aquatic species. Addressing the issue of wastewater is imperative, as it directly influences public health and mitigates the prevalence of waterborne diseases. Therefore, creating swift, accurate, and field-deployable detection systems for environmental pollutants becomes crucial for facilitating preventative public health surveillance [6]. Industrial activities cause significant annual global releases of HMs, estimated at around 22,000 metric tons of cadmium, 939,000 tons of copper, 783,000 tons of lead, and 1,350,000 tons of zinc[7]. This underscores the essential requirement for efficient treatment of industrial wastewater prior to its discharge into the environment.

Even trace amounts of pollutants in wastewater can have profound environmental impacts, necessitating the creation of highly sensitive detection techniques [8]. Although sophisticated analytical tools like HPLC, GC, and diverse spectroscopic methods yield precise detection of contaminants, their high cost, time requirements, and need for trained personnel restrict their use for real-time, on-location monitoring [6]. Since the advent of the first biosensor in 1962, significant advancements have been made in biosensor technology, resulting in innovative designs and enhanced functionality [9]. Biosensors, analytical devices engineered to detect and quantify pollutants by transducing biological signals into optical or electrical outputs, provide rapid, precise, and reliable real-time data on analytes. The high specificity inherent to biosensors reduces signal interference from non-target substances, rendering them highly valuable tools for environmental surveillance. The effectiveness of biosensors in continuous or single-point detection and measurement is contingent on the biological elements employed. Utilizing organisms to predict chemical pollution exposure further enhances the predictive power of these devices, enabling exact assessment of environmental pollutants' detrimental effects.

To date, several excellent reviews in the literature have discussed biosensors across multiple disciplines [6, 9, 10]. However, biosensors are classified based on their transduction mechanisms, such as optical, electrochemical, and piezoelectric, or their biorecognition elements, which encompass antibodies, aptamers, cells, enzymes, receptors, and neurons. This paper reviews current biosensor technologies and highlights recent advances in their use for environmental monitoring, with a focus on improved detection of HMs in wastewater.

2. Principles of biosensors

Functionally, a biosensor operates as a self-contained, integrated system that yields precise quantitative or semi-quantitative analytical results by employing a biological sensing element in direct physical contact with a signal transducer [11]. The components of a biosensor are divided into three segments including (1) the biological recognition elements, such as enzymes, antibodies, and DNA, play a crucial role in biosensors. The device incorporates: (2) a signal transducer to transform the biological interaction into a quantifiable and readily interpretable output, and (3) a signal processor designed to present this converted signal clearly and efficiently. To date, several excellent reviews in the literature have discussed biosensors across multiple disciplines [6, 9, 10]. Nonetheless, a common approach categorizes biosensors according to either their method of signal transduction (e.g., optical, electrochemical, piezoelectric) or the nature of their biorecognition component (including elements like antibodies, aptamers, cells, enzymes, receptors, or neurons). Aptamer-based electrochemical sensors achieve LOD 60.7 nM for Pb²⁺ in lake water via G-quadruplex folding (FAM-Pb-14S) [12]. Co-ions like Cu²⁺ can induce 15% false responses unless blocked by e.g. 6-mercaptohexanol monolayers. ​

2.1 Classifications of biosensor

Electrochemical biosensors see extensive application partly because their design centers on electrodes suitable for immobilizing biomolecules; these electrodes facilitate the detection of biochemical occurrences by translating them into quantifiable electrical signals [11, 13]. This conversion enables the investigation of diverse biochemical reactions and molecular interactions within biosensing applications. A significant advantage of electrochemical biosensors lies in their straightforward integration with existing electronics manufacturing processes, facilitating their suitability for mass production [14]. The adaptability of biosensors has led to their widespread use across varied fields, including ensuring food safety, performing medical diagnostics, and conducting environmental surveillance [9]. Their small footprint and economic advantages position biosensors as strong contenders for environmental monitoring roles, particularly for the early detection of toxic agents like HMs, viruses, or organic pollutants. Despite some limitations, such as a limited operating temperature range, a brief shelf life, and the potential for cross-sensitivity, their cost-effectiveness ensures they are readily available to many. For instance, the hybrid Pt NPs/SiO₂–DNAzyme electrochemical biosensor reported by Skotadis et al. achieves ultralow limits of detection (LODs) of 0.8 nM for Pb²⁺, 1 nM for Cd²⁺, and 10 nM for Cr³⁺, with rapid response times of 7 - 19 s [15]. Calibration was performed using six concentrations (1, 2, 5, 10, 20, 50 nM), yielding a linear range of approximately 1 - 50 nM for Pb²⁺ and Cd²⁺, and 10 - 100 nM for Cr³⁺ [15]. The biosensor also proved excellent precision, with standard deviations ranging from 0.28 - 1.2% across ten independent sensor replicates per ion. In recent work on optical‐plasmonic sensing, nanocrystalline cellulose/PEDOT (NCC/PEDOT) thin films have been shown to enhance surface‐plasmon‐resonance (SPR) sensitivity for mercury ions, achieving a limit of detection as low as 2 ppb (≈10 nM) within 30 min while maintaining selectivity against common co-ions [16]. Similarly, piezoelectric quartz‐crystal‐microbalance (QCM) platforms functionalized with homocysteine and nanoparticle coatings detect Hg²⁺ down to 0.1 ppb (0.498 nM) over a vast dynamic range (0.1 ppb to 1 355 ppm) in under 30 min; their portability, milliliter‐scale sample requirement, and excellent repeatability make them ideal early-warning systems for on-site mercury monitoring [17].

The basis of optical biosensor operation lies in utilizing the interplay between an optical field and the biorecognition element [18]. This sensing modality proves especially helpful for analyzing colored or turbid samples, encompassing various biomolecules or microorganisms like viruses, bacteria, and other pathogens. Optical biosensors operate using one of two primary detection strategies: label-based or label-free. The label-based detection employs a labeling molecule, with the optical signal generated via colorimetric, fluorescent, or luminescent methods. Label-based detection involves labeling the bioanalyte to generate an optical response, commonly used in environmental monitoring of pathogens like Escherichia coli and Salmonella typhimurium in water and food through techniques such as fluorescence and colorimetry [9]. However, label-based methods have certain drawbacks, including the potential for the labeling process to alter the bioanalyte's activity and introduce quantification errors. This has sparked increased interest in label-free methods, particularly SPR, which relies solely on bioanalyte-transducer interactions. In the label-free mode, the detection signal arises directly from the interaction between the analyte and the transducer. Despite its advantages, optical biosensing, particularly label-free methods related to SPR, faces challenges in terms of miniaturization, portability, and sustainability for broader application.

The fundamental operation of mass-based biosensors centers on finding changes in mass that take place when the target analyte attaches to the biorecognition element fixed on the sensor's surface. This mass change is typically measured using transducers like piezoelectric devices, which convert mechanical stress into an electrical signal correlated with the analyte concentration [19]. An illustrative case is the quartz crystal microbalance (QCM) biosensor, which has found extensive application in both research and environmental monitoring. In the context of biological studies, QCM sensors offer notable advantages including heightened sensitivity, ease of use, and cost-efficiency, showing them as useful tools within analytical chemistry. Their versatility enables the detection of various molecules, chemicals, polymers, and biological samples. However, a key challenge is still in optimizing the crystal coating process to ensure uniform and cohesive deposition layers. Addressing this challenge, with a focus on sustainability, could unlock the full potential of QCM sensors for broader applications.

Progress in biosensor technology owes much to nanoscience and nanotechnology, clearly demonstrated by the emergence of nanobiosensors and devices capable of single-molecule detection [20, 21]. Integrating nanomaterials like functionalized nanoparticles, nanowires, or nanotubes into sensor designs has led to considerable gains in sensitivity, selectivity, and overall performance characteristics. These advancements arise from the distinct qualities of nanomaterials, such as their shape and size-dependent properties, extensive surface area, and cost-efficiency. Practical challenges persist, however, encompassing issues like detecting analytes present at extremely low levels, addressing potential target sequence mutations or evolution (particularly for oligonucleotides and proteins), and achieving an optimal trade-off between fabrication cost and operational effectiveness across diverse sensor types.

3. Heavy metals monitoring

Heavy metals (HMs) contamination is commonly released due to human activities and industrial processes, including refineries, metal processing, mining, cement production, and smelting operations [22]. This form of contamination presents considerable dangers to human well-being and ecological systems. HMs pose substantial health risks to ecosystems even at minimal concentrations, primarily because they resist biological breakdown, are not easily chemically degraded, and tend to bioaccumulate within organisms [23, 24]. Additionally, water, soil, and living beings are known to accumulate these metals, underscoring the need of environmental monitoring to prevent contamination and illness [6]. Various methods, including chromatography (gas chromatography, high-performance liquid chromatography), inductively coupled plasma mass spectrometry, or atomic absorption spectroscopy, can be employed at laboratory for qualitative and quantitative HMs analysis [8]. Nevertheless, real-time detection, excessive costs, and by-product release pose significant challenges for environmental monitoring by these techniques. Through biosensors, a method offering high sensitivity for deciding HMs concentrations is available, thereby aiding efforts to manage water safety and quality.

Detection of HMs can be achieved using DNA probes, which function as recognition elements working via several distinct mechanisms. Among these mechanisms is the specific interaction between DNA bases and target metal ions, leading to the creation of a stable duplex DNA structure [11]. Additionally, HMs can break DNAzymes, and a guanine-rich probe can undergo a transition to a stable G-quadruplex structure [25]. Whole-cell microbial biosensors offer a means to detect HMs through the use of genetic components engineered to react to designated chemical substances [26]. The performance characteristics of such biosensors depend on the interplay between regulatory proteins associated with promoters and the specific reporter genes chosen to signal the presence of pollutants. Within microorganisms engineered for biosensing, reporter genes act as indicators, converting specific biological responses to pollutants into quantifiable physicochemical signals [27]. Table 1 presents typical biosensors for HMs monitoring.

Table 1: Typical biosensors for HMs monitoring

Type of biosensor	Material/Bacteria	Wastewater	Detection limits	Time	Remarks	Reference
Biosensor cell	A luminescent bacterium Vibrio sp. MM1	Synthetic water	Zn2+ (0.97 mg/L), Ni2+ (3.0 mg/L), Cu2+ (3.62 mg/L), Pb2+ (5.75 mg/L), Co2+ (6.16 mg/L, and Cd2+ (14.54 mg/L)	15 min	high sensitivity in detecting HMs	[28]
Light-up biosensor	FAM-Pb-14S	Lake water and serum samples	60.7 nM	1 h	Simple, rapid and reliable,	[29]
Molecular biosensors	Acinetobacter baylyi ADP1 Tox2	River water	-	30 min	detect and manage pollution in urban river systems	[30]
A protein biosensor	mApple-D6A3 protein	Tap water	Cu2+ (18.7 µM), Ni2+ (21.4 µM), and Cd2+ (19.3 µM)	20 min	Detection accuracy exceeds 80%	[31]
Electrochemical biosensor	Oxygen-type electrochemical biosensor by a packed-bed bioreactor	Synthetic water	Cr6+ (0.0762 mg/L)	5 min	Cost-effective, accurate	[8]
Electrochemical biosensor	Cu-TCPP/Au/Pb2+-G4-hemin	Synthetic water	1.7 nM	–	High sensitivity and high selective	[32]
Electrochemical biosensor	Hybrid nanoparticle (Pt NPs/SiO2)/DNAzyme	Synthetic water	Pb2+ (0.8 nM), Cd2+ (1 nM) and Cr3+ (10 nM)	–	good sensitivity, precision, and sufficient dynamic range	[33]
A dual-colored bacterial biosensor	A CadR-regulated vioABE expression module and a MerR-regulated VioC expression module	Sea water	Cd2+ (4.9 nM), Pb2+ (24.4 nM, and Hg2+ (0.5 nM)	4 h	high sensitivity and selectivity	[34]

Whole-cell biosensors show the potential for monitoring and identifying HMs, especially in terms of selectivity and sensitivity. Besides, several biosensors based on colorimetric, and fluorescence, electrochemical measurements were successfully devised for HMs detection. The creation of various biosensors has involved using nanomaterials, including metal oxides and nanostructured forms of carbon.

4. Role of biosensor application on achievement of SDGs

Biosensor applications significantly contribute to achieving various SDGs. About SDG 6 (Clean Water and Sanitation), biosensors enable widespread screening for environmental contaminants, thereby contributing to safer drinking water access by helping to minimize pollution levels affecting both potable water sources and aquatic environments. In relation to SDG 12 (Responsible Consumption and Production), the implementation of biosensors can diminish dependence on hazardous chemicals and minimize waste produced during sample preparation and analysis, hence enhancing environmental monitoring and management practices. On SDG 13 (climate action), biosensors reduce energy consumption and carbon footprints in traditional chemical analyses. Biosensors play a crucial role in addressing pollution management in both marine and terrestrial ecosystems, contributing significantly to the goals of SDG 14 and SDG 15.

5. Chances and challenges of biosensor application

The design possibilities for environmental biosensor applications have been significantly broadened by recent progress in nanomaterial and molecular recognition elements. Nevertheless, increasing attention is being directed towards technologies allowing the direct, real-time monitoring of pollutants at the sampling location. Drones have become valuable tools for environmental monitoring. With the help of advanced technology, drones are now being utilized for a wide range of purposes, including assessing water and air quality, monitoring agricultural activities, and measuring volcano gas emissions [35]. A noteworthy instance involves the incorporation of a whole-cell biosensor into drones to monitor air and water quality in distant regions. This system showcases the capabilities of combining biosensors with drones for cost-effective and efficient environmental monitoring [35, 36].

Within environmental monitoring, electrochemical and enzymatic biosensors find significant use, with acetylcholinesterase-based systems being prime examples frequently employed for pesticide detection [26, 37]. Such biosensing systems gain appreciation due to their user-friendliness, dependable accuracy, and relatively low cost. Broader adoption of certain biosensors faces hurdles such as the significant expense of enzyme purification, insufficient thermal stability, and limitations in their effective operating conditions. On the other hand, aptamers offer a hopeful alternative because of their capacity to rehybridize, identify a wide range of targets, and endure different environmental conditions. Immunosensors, employed for the monitoring of organic molecules like toxins and endocrine-disrupting chemicals, offer an impressive degree of specificity [19]. Nonetheless, they face specific hurdles related to the regeneration of antibodies, their immobilization, and the optimization of their activity. These challenges pose significant obstacles to the development of immunosensors, requiring added research to improve their practical applications.

A primary limitation hindering the deployment of many current environmental biosensors is the insufficient validation using authentic environmental matrices; testing is often confined to synthetic samples or tap water, restricting assessment of their real-world performance, as presented in Table 1. Many biosensors are typically confirmed using tap water or synthetic samples, which limits their practicality in real-world situations. The lack of commercial biosensors for environmental monitoring is primarily due to this gap, which stands in stark contrast to their extensive use in clinical settings. The diverse aspects of biosensor development, along with the difficulties in achieving consistent results and on-site functionality, contribute to this discrepancy. Notwithstanding the existing challenges, considerable progress has occurred on the deployment of biosensors in actual environmental contexts. Recent research has proved the effective use of biosensors in various environments, such as lakes, rivers, seawater, soil, and wastewater. Such research initiatives reflect a committed focus on tackling the difficulties associated with environmental biosensors and expanding their practical, field-based applications. In summary, while the field of environmental biosensors has seen noteworthy progress, several hurdles stay that require solutions. Continuous improvements in designing biosensors, particularly focusing on boosting enzyme stability, broadening the applicability of aptamers, and refining immunosensor performance, are vital for the field's advancement. Successfully translating laboratory-validated performance into reliable, practical field use is essential to foster wider adoption and deployment of biosensors specifically for environmental monitoring purposes.

The worldwide market for biosensors is projected to experience substantial growth, increasing from USD 30.6 billion in 2024 to USD 49.6 billion by 2030. This represents a compound annual growth rate of 8.4%, with environmental applications poised to emerge as a significant sub-segment [38]. The integration of artificial intelligence and data analytics, particularly through the combination of multiplex sensor arrays with machine learning algorithms, has improved the ability to deconvolute analyte signals and can predict pollution events up to 48 h in advance [39]. As the field evolves, the development of ISO standards for biosensor calibration and data formatting will play a critical role in ensuring interoperability, consistency, and regulatory acceptance across international markets.

6. Conclusion

Employing biosensor technology to detect HMs in wastewater provides fundamental benefits compared to traditional analytical methods, chiefly through enabling swift, portable, and economical measurements. Innovations in nanomaterial design and ecofriendly biorecognition elements have produced sensors that detect trace concentrations of lead cadmium mercury and arsenic with high precision. Feasibility studies have confirmed their applicability in matrices such as industrial discharge, municipal wastewater, and agricultural runoff. Combining these sensors with internet-connected monitoring grids and compact chip-based platforms promises to enable ongoing, real-time surveillance and provide timely alerts for pollution incidents. Key barriers remain in mass production of consistent sensors validation in complex sample matrices and compliance with evolving environmental regulations. Addressing these issues through standardized manufacturing protocols robust material functionalization and comprehensive field trials will be critical. Successfully bridging these gaps will empower practitioners to implement biosensor systems at scale thereby supporting sustainable water management initiatives and advancing public health protection goals.

Phạm Thị Thanh Hoa

Faculty of Engineering and Technology, Van Hien University, Ho Chi Minh City

Nguyễn Tấn Thông

Ho Chi Minh City University of Natural Resources and Environment (HCMUNRE)

(Source: The article was published on the Environment Magazine by English No. III/2025)

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