Smartphone-Based Whole-Cell Biosensor Platform Utilizing an Immobilization Approach on a Filter Membrane Disk for the Monitoring of Water Toxicants

Challenges and opportunities in commercializing whole-cell bioreporters in environmental application

Since the initial introduction of whole-cell bioreporters (WCBs) nearly 30 years ago, their high sensitivity, selectivity, and suitability for on-site detection have rendered them highly promising for environmental monitoring, medical diagnosis, food safety, biomanufacturing, and other fields. Especially in the environmental field, the technology provides a fast and efficient way to assess the bioavailability of pollutants in the environment. Despite these advantages, the technology has not been commercialized. This lack of commercialization is confusing, given the broad application prospects of WCBs. Over the years, numerous research papers have focused primarily on enhancing the sensitivity and selectivity of WCBs, with little attention paid to their wider commercial applications. So far, there is no a critical review has been published yet on this topic. Therefore, in this article we critically reviewed the research progress of WCBs over the past three decades, assessing the performance and limitations of current systems to understand the barriers to commercial deployment. By identifying these obstacles, this article provided researchers and industry stakeholders with deeper insights into the challenges hindering market entry and inspire further research toward overcoming these barriers, thereby facilitating the commercialization of WCBs as a promising technology for environmental monitoring.

Whole-Cell Biosensor for Iron Monitoring as a Potential Tool for Safeguarding Biodiversity in Polar Marine Environments

Iron is a key micronutrient essential for various essential biological processes. As a consequence, alteration in iron concentration in seawater can deeply influence marine biodiversity. In polar marine environments, where environmental conditions are characterized by low temperatures, the role of iron becomes particularly significant. While iron limitation can negatively influence primary production and nutrient cycling, excessive iron concentrations can lead to harmful algal blooms and oxygen depletion. Furthermore, the growth of certain phytoplankton species can be increased in high-iron-content environments, resulting in altered balance in the marine food web and reduced biodiversity. Although many chemical/physical methods are established for inorganic iron quantification, the determination of the bio-available iron in seawater samples is more suitably carried out using marine microorganisms as biosensors. Despite existing challenges, whole-cell biosensors offer other advantages, such as real-time detection, cost-effectiveness, and ease of manipulation, making them promising tools for monitoring environmental iron levels in polar marine ecosystems. In this review, we discuss fundamental biosensor designs and assemblies, arranging host features, transcription factors, reporter proteins, and detection methods. The progress in the genetic manipulation of iron-responsive regulatory and reporter modules is also addressed to the optimization of the biosensor performance, focusing on the improvement of sensitivity and specificity.

Whole-cell bioreporter application for rapid evaluation of hazardous metal bioavailability and toxicity in bioprocess

Assessing heavy metal bioavailability and toxicity during bioprocess is critical for advancing green biotechnology. The capability of whole-cell bioreporters to measure heavy metal bioavailability has been increasingly recognized. The advantages of this technology being applied to bioprocess monitoring are less studied. Here we investigate the potential of a cadmium- and lead-sensitive bioreporter to be used for heavy metals as a class, which holds great interest for bioprocess applications. We evaluated the bioavailability of eight individual heavy metals with bioreporter zntA, as well as the bioavailability and toxicity of mixed metals. The bioavailability and toxicity of heavy metals in bioprocess samples were also evaluated. We have demonstrated for the first time that the zntA bioreporter can effectively detect the bioavailability of zinc, nickel, and cobalt with limit of detection lower than 0.01, 0.08 and 0.5 mg·L-1, respectively. The detection limits meet the requirements of the WHO, the U.S. Environmental Protection Agency, and the China drinking water quality standards, which makes this approach reasonable for monitoring heavy metal bioavailability in bioprocess. LIVE/DEAD toxicity experiments have been conducted for the detection of mixed metal solution toxicity to zntA bioreporter which shows an EC50 (as EC50, concentration for 50% of maximal effect) value of mixed metal solution is 3.84 mg·L-1. Samples from wastewater treatment plants, sludge treatment plants and kitchen waste fermentation processes were analyzed to extend upon the laboratory results. The results of this study confirm the potential for practical applications of bioreporter technology in bioprocess monitoring. In turn, development for such practical applications is key to achieve the necessary level of commercialization to further make the routine use of bioreporters in bioprocess monitoring feasible.

Illuminating Progress: The Contribution of Bioluminescence to Sustainable Development Goal 6-Clean Water and Sanitation-Of the United Nations 2030 Agenda

The United Nations Agenda 2030 Sustainable Development Goal 6 (SDG 6) aims at ensuring the availability and sustainable management of water and sanitation. The routine monitoring of water contaminants requires accurate and rapid analytical techniques. Laboratory analyses and conventional methods of field sampling still require considerable labor and time with highly trained personnel and transport to a central facility with sophisticated equipment, which renders routine monitoring cumbersome, time-consuming, and costly. Moreover, these methods do not provide information about the actual toxicity of water, which is crucial for characterizing complex samples, such as urban wastewater and stormwater runoff. The unique properties of bioluminescence (BL) offer innovative approaches for developing advanced tools and technologies for holistic water monitoring. BL biosensors offer a promising solution by combining the natural BL phenomenon with cutting-edge technologies. This review provides an overview of the recent advances and significant contributions of BL to SDG 6, focusing attention on the potential use of the BL-based sensing platforms for advancing water management practices, protecting ecosystems, and ensuring the well-being of communities.

Biolum' RGB: A Low-Cost, Versatile, and Sensitive Bioluminescence Imaging Instrument for a Broad Range of Users

Luminometer and imaging systems are used to detect and quantify low light produced by a broad range of bioluminescent proteins. Despite their everyday use in research, such instruments are costly and lack the flexibility to accommodate the variety of bioluminescence experiment formats that may require top or bottom signal acquisition, high or medium sensitivity, or multiple wavelength detection. To address the growing need for versatile technologies, we developed a highly customizable bioluminescence imager called Biolum' RGB that uses a consumer color digital camera with a high-aperture lens mounted at the bottom or top of a 3D-printed dark chamber and can quantify bioluminescence emission from cells grown in 384-well microplates and Petri dishes. Taking advantage of RGB detectors, Biolum' RGB can distinguish spectral signatures from various bioluminescence probes and quantify bioluminescence resonant energy transfer occurring during protein-protein interaction events. Although Biolum' RGB can be used with any smartphone, in particular for low bioluminescence signals, we recommend the use of recent digital cameras which offer better sensitivity and high signal/noise ratio. Altogether, Biolum' RGB combines the benefits of a plate reader and imager while providing better image resolution and faster acquisition speed, and as such, it offers an exciting alternative for any laboratory looking for a versatile, low-cost bioluminescence imaging instrument.

Whole-cell bacterial biosensor with the capability to detect red palm weevil, Rhynchophorus ferrugineus, in date palm trees, Phoenix dactylifera: a proof of concept study

The red palm weevil (RPW), Rhynchophorus ferrugineus, is considered a severe pest of palms. Usually, the early stages of infection are without visible signs. An attractive early sensing approach of non-visible infections is based on volatile organic compounds (VOCs). In this study, a whole-cell bacterial biosensor was used for the identification of RPW in date palm (Phoenix dactylifera). The cells are genetically modified to produce light in the presence of general stresses. The bioluminescent bacterial panel is based on three genetically engineered Escherichia coli strains that are sensitive to cytotoxicity (TV1061), genotoxicity (DPD2794), or quorum-sensing (K802NR). The bioluminescent bacterial panel detects the presence of VOCs and a change in the light signal is then generated, reflecting the health status of the date palm tree. The bioreporter bacteria cells are immobilized in calcium alginate tablets and placed in a sealed jar without direct contact with the tested sample, thereby exposing them only to the VOCs in the surrounding air. The immobilized bacteria cells were exposed to the air near infected by RPW or uninfected sugar canes, date palm tree pieces, and on date palm trees. Commercial plate reader was used for signal measurement. The findings show that quorum-sensing was induced by all the tested samples of infected sugar canes, date palm tree pieces, and date palm trees. While, cytotoxicity was induced only by infected date palm tree pieces, and genotoxicity was induced only by infected date palm trees. The bacterial monitoring results enable the identification of specific signatures that will allow a quick and accurate diagnosis.

Microfluidic technology and its application in the point-of-care testing field

Since the outbreak of the coronavirus disease 2019 (COVID-19), countries around the world have suffered heavy losses of life and property. The global pandemic poses a challenge to the global public health system, and public health organizations around the world are actively looking for ways to quickly and efficiently screen for viruses. Point-of-care testing (POCT), as a fast, portable, and instant detection method, is of great significance in infectious disease detection, disease screening, pre-disease prevention, postoperative treatment, and other fields. Microfluidic technology is a comprehensive technology that involves various interdisciplinary disciplines. It is also known as a lab-on-a-chip (LOC), and can concentrate biological and chemical experiments in traditional laboratories on a chip of several square centimeters with high integration. Therefore, microfluidic devices have become the primary implementation platform of POCT technology. POCT devices based on microfluidic technology combine the advantages of both POCT and microfluids, and are expected to shine in the biomedical field. This review introduces microfluidic technology and its applications in combination with other technologies.

Improvements in Smartphone and Night Vision Imaging Technologies Enable Low Cost, On-Site Assays of Bioluminescent Cells

Technologies enabling on-site environmental detection or medical diagnostics in resource-limited settings have a strong disruptive potential compared to current analytical approaches that require trained personnel in laboratories with immobile, resource intensive instrumentation. Handheld devices, such as smartphones, are now routinely produced with CPUs, RAM, wireless data transfer capabilities, and high-resolution complementary metal oxide semiconductor (CMOS) cameras capable of supporting the capture and processing of bioluminescent signals. In theory, combining the capabilities of these devices with continuously bioluminescent human cell-based bioreporters would allow them to replicate the functionality of more expensive, more complex, and less flexible platforms while supporting human-relevant conclusions. In this work, we compare the performance of smartphone (CMOS) and night vision (image intensifier) devices with in vivo (CCD camera), and in vitro (photomultiplier tube) laboratory instrumentation for monitoring signal dynamics from continuously bioluminescent human cellular models under toxic, stable, and induced expression scenarios. All systems detected bioluminescence from cells at common plating densities. While the in vivo and in vitro systems were more sensitive and detected signal dynamics representing cellular health changes earlier, the night vision and smartphone systems also detected these changes with relatively similar coefficients of variation and linear detection capabilities. The smartphone system did not detect transcriptional induction. The night vision system did detect transcriptional activation, but was less sensitive than the in vivo or in vitro systems and required a stronger induction before the change could be resolved.

Remote Recognition of Moving Behaviors for Captive Harbor Seals Using a Smart-Patch System via Bluetooth Communication

Animal telemetry has been recognized as a core platform for exploring animal species due to future opportunities in terms of its contribution toward marine fisheries and living resources. Herein, biologging systems with pressure sensors are successfully implemented via open-source hardware platforms, followed by immediate application to captive harbor seals (HS). Remotely captured output voltage signals in real-time mode via Bluetooth communication were reproducibly and reliably recorded on the basis of hours using a smartphone built with data capturing software with graphic user interface (GUI). Output voltages, corresponding to typical behaviors on the captive HS, such as stopping (A), rolling (B), flapping (C), and sliding (D), are clearly obtained, and their analytical interpretation on captured electrical signals are fully validated via a comparison study with consecutively captured images for each motion of the HS. Thus, the biologging system with low cost and light weight, which is fully compatible with a conventional smartphone, is expected to potentially contribute toward future anthology of seal animals.