Potential Therapeutic Effects of New Ruthenium (III) Complex with Quercetin: Characterization, Structure, Gene Regulation, and Antitumor and Anti-Inflammatory Studies (RuIII/Q Novel Complex Is a Potent Immunoprotective Agent)

Review Article Prospects of Synthetic Biology in the Actualization of Green Chemistry and Environmental Solutions . ABSTRACT Synthetic biology (SynBio) is an emerging field of endeavor that uses modular and replaceable biological parts or devices in standard chassis, or whole organisms to generate intended and programmed outputs that can be quantified and optimized until they meet the desired efficiency. As a result, SynBio is becoming increasingly popular for addressing critical global challenges such as the bioremediation of recalcitrant organic and inorganic pollutants in the environments and the reduction in emission of toxic waste from industrial processes. Although synthetic chemistry and the chemical industry have greatly enhanced the quality of life of the human race, they have also caused significant detrimental effects in terms of pollution, toxic waste emissions, and public health endangerment. SynBio technology has now found application in the bioremediation of polluted environments and to actualize previously unfeasible industrial outcomes and green chemistry. This study elucidates the innovative applications of SynBio concepts in the bioremediation of polluted environments, the actualization of eco-friendly industrial operations, and the realization of green chemistry principles. We also explore SynBio-based strategies for minimizing toxic waste emission and energy consumption, while simultaneously enhancing the production of value-added industrial products from renewable feedstocks, industrial wastes, and greenhouse gases. Several ethical and safety concerns and regulatory framework required to ensure the responsible application of SynBio technology were also reviewed. By unearthing the propitious potential of SynBio in biotechnology, sustainable development, and green chemistry, this study aims to afford insights into the future directions of SynBio technology and its potential impact on various sectors, from industry to environment. Keywords: Synthetic biology; Green chemistry; Bioremediation; Sustainable development 1.0 INTRODUCTION SynBiology or Synthetic biology (SynBio) is a discipline of biology that employs engineering ideas to design and construct new biological systems with predefined functions [1]. Essentially, SynBio encompasses the design of novel approaches for programming predictable cellular modalities and depends immensely on the growing wealth of knowledge and expanding research efforts in genomics, computer sciences, biomedical and chemical engineering, and even mathematics. It entails using genetic engineering, computer modeling, and other methodologies to create biological components and systems for a variety of applications, including industrial microbial processes, environmental microbiology, and green chemistry [2]. System biology is founded on genetic engineering and has been utilized for decades to edit and manipulate the genetic materials of living organisms. Conversely, toggling a step further, SynBio technology alongside modifying existing systems seeks to construct novel and more efficient cellular systems from scratch that do not exist in nature. In connection with this, . SynBio is viewed as a "bottom-up" strategy of cell engineering that entails the assemblage of smaller functional parts to build large cellular systems that can produce intended outcomes [1]. Globally, large portions of land and water resources are already contaminated due to industrial activities, such as mineral mining, polymer synthesis, transportation, and agriculture [3, 4]. As a way to curb this menace, innovative methods of minimizing waste emission, handling tainted waste, and restoring damaged areas are now developed through the application of synthetic biology [2]. Furthermore, before concerns about the environment, human health, and safety came to prominence, the manufacturing and distribution of chemicals had a relatively easy economy [2]. In the past, feedstock expenditures, energy requirements, and product marketability were among the main economic issues at play [5]. Now, however, expenditures have to include expenses related to waste disposal, end-of-pipe waste treatment, liability, and regulatory compliance [6]. Auspiciously, green chemistry is proposed to eliminate or significantly reduce the additional costs associated with meeting the environmental and safety requirements of conventional chemical synthesis by doing away with or drastically reducing the use of toxic or hazardous feedstocks and catalysts as well as abrogating the production of dangerous intermediates and byproducts [7]. Consequently, the tenets of green chemistry are being adopted and propagated in various life domains, including medicines, material sciences, agriculture, biotechnology, and environmental sciences [8]. Also, biodegradable products harnessed from renewable feedstock such as lignocellulosic waste, and agricultural and industrial bioproducts are now used to substitute petroleum-based products, hence mitigating their environmental implications. In the same vein, chemical reactions in the production chain are being controlled and monitored by smart devices, such as biosensors, microfluidic chips, and nanomaterials [9]. In addition, industrial processes continue to adopt more eco-friendly solvents and ionic liquids, including supercritical fluids, deep eutectic solvents, or switchable solvents for the dissolution or extraction of materials [10]. The sustainable synthesis and utility of novel enzymes to catalyze reactions that would otherwise require hazardous chemicals and extreme conditions is one striking innovation afforded by SynBio technology [11]. The application of SynBio-based technology in industrial operations is proposed to hold promise in curbing environmental pollution [12, 13]. For instance, only recently have bacteria designed using SynBio techniques been deployed to tackle dangerous and recalcitrant heavy metals like mercury and arsenic that elicit deleterious immune reactions [13]. Nowadays, engineered microorganisms that can degrade resistant environmental toxins have found applications in various product and manufacturing sectors. We can now engineer organisms capable of degrading everyday wastes, such as plastics, pharmaceuticals, hydrocarbons, pesticides, and personal care products that predominate in water bodies, air, and polluted soils [14]. In the same vein, SynBio-enhanced biosensors have now emerged and are been deployed to monitor and detect the presence of hazardous substances in the environment; keeping their toxic effects on humans and the environment in check [12]. SynBio technology has found massive utility in the management of industrial sites and the restoration of polluted areas [15]. Interestingly, several environmental merits and assurance have been realized by the adoption of SynBio in addressing certain quintessential global concerns, and it is projected to create a sustainable future (Figure 1). However, some key ethical considerations, safety protocols, and regulatory frameworks must be instituted and constantly reviewed to ensure the responsible application of SynBio technology. The present study reviews the prospects of SynBio technology in the actualization of green chemistry and environmental solutions. Figure. 1: SynBio technology; the new directions for sustainable future 1.1 Challenges and Innovations in Environmental Microbiology Environmental microbiology investigates the dynamic interactions that exist between microorganisms and their ecological niche and utilizes available data to solve several environmental problems. In recent times, as the world currently witnesses the impact of the evolution of novel and more aggressive forms of infectious agents in the environment, new recalcitrant compounds have also been discovered in surface and ground waters that previously served as our potable water sources [12]. Perhaps, this could be due to the increasing strains placed on water resources, as society grows. For example, groundwater is currently being pumped out faster than it can replenish itself in some regions of the United States [16]. With rising waste discharges containing chemical and biological contaminants finding their way into our water resources, it is evident that environmental microbiologists face significant challenges in this regard. These challenges also arise in polluted soils. Land resources are becoming increasingly scarce as the world population grows, and settlements are encroaching on contaminated places such as agricultural fields with years of pesticide use, landfills, and mine tailings sites. The use of molecular genetics and biotechnology tools has considerably improved these subjects in both circumstances. With the worldwide population rise, the development and assessment of new ways of detecting and eradicating germs and pathogens in food and water supply, as well as the air that humans breathe, has become vital to public health. Additionally, pathogens and pollutants detection capacity of modern-day technologies have immensely improved and expanded. Sequel to this, the use of risk assessment to determine the need for control where it is most effective, as well as community education to lessen the dangers associated with living near polluted sites, is becoming increasingly worthwhile. However, despite the horizon and advancement of research efforts, microbial communities remain poorly understood and challenges in replicating complex ecosystems remain an impending factor [17]. Nevertheless, the application of SynBio techniques in environmental microbiology is laying the foundations for more precise genetic engineering, allowing for the introduction of artificial or optimized metabolic pathways into certain microbial strains aiming at bioremediation [2]. Possibly, the addition of SynBio-based functions to microbiological organisms is projected to enhance bioremediation, nutrient recycling, and ecosystem restoration as discussed later on. 2.0 FABRICS OF GREEN CHEMISTRY Green chemistry entails the integration of chemical innovations, expertise, and practicality to reduce or eliminate the use of harmful substances in the design, production, and use of chemical entities along the production chain. The concept of green chemistry is centered on resource conservation, pollution reduction, health, safety, and sustainable environment promotion [18]. As an emerging and multifaceted concept, green chemistry accentuates safe and efficient chemical synthesis, the deployment of alternative solvents, and biocatalysts, and the realization of clean and renewable energy. Green chemistry is targeted at eliminating the detrimental effects of hazardous industrial products or by-products on the environment, and curbing the recently increased modalities and mortality accompanying industrialization [19]. Green chemistry lessens the harmful environmental effects of chemical production processes, contributing to the development of a more sustainable industrial landscape [20]. The 12 principles of green chemistry (Figure 2) can also be successfully applied to organic synthesis, where hazardous solvents are typically used: maximum atom economy (avoidance of wastes and by-products, especially when using solvent-less techniques, i.e. dry media), safer and innocuous chemical synthesis routes void of harmful chemical substances, use of renewable precursors (biomass replacing fossil fuels), small amounts of catalysts (innocuous and preferably solids to be renewable), safer chemicals and solvents (water, ionic liquids) and biodegradable materials. Ionic liquids have attracted considerable attention as alternative reaction media for a wide range of chemical transformations, because of their low vapor pressure, good solvating characteristics, considerable thermal stability, and easily adjustable physical (e.g. melting point, vapor pressure, or viscosity) and chemical properties (e.g. polarities, basicity, and acidity, basicity). By adhering to green chemistry principles, it is now possible to implement energy-efficient processes that minimize waste production, promote matter and energy economy, employ safer solvents and renewable chemicals, produce less hazardous materials, and execute smart catalysis with fewer byproducts or derivatives under biodegradable process design [21]. Figure 2: The 12 principles of green chemistry 2.1 Renewable Resources Chemistry is required for the creation of most products utilized in daily life, such as fuels, transportation devices, construction materials, food products, pharmaceuticals, personal care products, and communication accessories. Given the breadth of this sector and its expansion requirements to ensure development and technological progress that can satisfy the demands of the growing global population, the time has come for a new chemical era in which the environmental impact of chemical products is minimized in terms of hazards, carbon footprint, life cycle, and resource sustainability. Despite recent reports of global warming and depletion of fossil fuel reserves, international efforts to promote the production of carbon-neutral end products and reduce CO2 emissions following the Kyoto Protocol have not been fully realized. Scientific investigations continue to focus on identifying and developing innovative solutions for the substitution of petroleum-based resources with renewable alternatives [22]. The use of biomass as readily available and internationally scalable feedstock has come into the limelight for the chemical industry and is upheld as a promising alternative to the usage of carbon resources. Green chemistry promotes the utility of renewable feedstock utility, such as biomass and plant-based resources, as opposed to non-renewable resources, to produce sustainable products [22]. Biomass utilization to produce energy, chemicals, and industrial commodities is a significant step toward the realization of sustainable product development. Biomass includes all macromolecular feedstocks derived from agricultural proceeds, forestry products, and their residues. The use of renewable feedstocks, particularly biomass, is a critical component of green chemistry. Using biomass for chemical processes cannot be regarded as an end in itself until all other green chemistry principles are meticulously applied. Hence, the principles of green chemistry are required to guide the entire biomass utility process. The core principles of green chemistry, which entail the efficiency of reactions, atom economy, moderated resource consumption, waste prevention, and increased safety of manufacturing processes and end products, all apply at all stages of biomass utility, from biomass generation and conversion to ultimate utilization of biobased products. 2.2 Atom Economy Atom Economy entails the design of chemical reactions that consumes all starting materials and emits the least amount of toxic waste. The primary objective of atom economy is to optimize the incorporation of starting ingredients into the ultimate result of any given industrial process. If maximum integration cannot be accomplished, then the levels of side products should preferably be minute and ecologically innocuous. Conversely, the reaction yield is solely concerned with the amount of the desired product that is recovered compared to the theoretical amount of the product. Along with the desired output, the atom economy considers all consumed reagents and undesired byproducts. Substitutions and eliminations, for example, account for the majority of uneconomical classical reactions in which intrinsic wastes are unavoidable. There is a fundamental difference between how a reaction yield and an atom economy yield are calculated [23]. 2.3 Biocatalysis Green chemistry emphasizes the deployment of biological catalysts to speed up chemical reactions to greatly reduce the amount of energy and resources consumed during the production of industrial products. In general, a bio-based economy entails multidisciplinary research efforts at the interface of biotechnology and chemical engineering, with an emphasis on the creation of environment-friendly chemo- and bio-catalytic modalities for the conversion of waste biomass into biochemicals, biofuels, and other bio-based products. In this regard, biocatalysis has a lot to offer. They are biodegradable and derived from renewable biomass. In addition, biocatalyst-based production processes generate less waste and use less energy than conventional ones because they operate in milder conditions [22]. Biocatalysis is a sustainable and green technology based on the ideas and measurements of sustainable development and green chemistry. The tremendous break-even made in molecular biology and biotechnology over the last 20 years is primarily responsible for this progress [23]. Through the use of protein engineering, it is now possible to create completely new biocatalytic reactions that were not previously known to exist in nature as well as to optimize already existing enzymes. Enzymatic transformations that meet predetermined parameters are now developed with great ease, leading to inherently sustainable processes [24]. Consequently, this approach has been deployed effectively in the industrial production of active pharmaceutical compounds and other value-added industrial products [25]. Other biocatalysis engineering techniques, such as medium, substrate, and reactor engineering, are now applied in addition to protein engineering to increase the productivity, economy, and sustainability of biocatalytic reactions [26]. Moreover, enzyme stability is enhanced even more through immobilization, allowing for repeated use and improved performance as well as commercial viability. As a result, biocatalysis is being used extensively in the manufacturing of several valuable industrial chemical commodities, including active pharmaceutical ingredients [27]. It has also been projected that the developing biobased economy associated with biocatalysis will further encourage its wider adoption in the future [28]. 2.4 Designs for Degradation The concept of design for degradation is targeted at creating chemical products that are easily degraded after use and pose no potential threat to the ecosystem [12]. In the realm of green chemistry, chemicals ought to be made in such a way that, after serving their purpose, they should be able to break down into innocuous byproducts and disappear from the environment. Unintentional hazards associated with the manufacture and use of chemicals pose terrible effects on human health and induce deplorable environmental damage. The lack of integrated thinking during the production and distribution of chemicals has frequently resulted in the manifestation of these adverse impacts on the environment [29]. Traditional industrial processes have not been able to adequately account for the pre- and post-market conditions of industrial products. Too many negative consequences are found after products and chemicals are dispersed throughout our environment, despite the robust testing systems [30]. In solving these problems, the first step is to ascertain the "molecular itinerary" of a product, which entails factoring and forecasting who, what, where, when, and why of an industrial product along its trajectory from production to degradation. This can be likened to a travel agency offering a comprehensive schedule for an extended, multi-city journey. When all the points on the itinerary tract are well considered, everyone is content, healthy, and makes it home safely, with unfavorable events either avoided or significantly reduced. These efforts are the core objectives of green chemistry [31]. 2.5 Safer Solvents Green chemistry promotes the use of non-flammable and non-toxic solvents that pose the least detrimental effect on the environment [21]. Solvents are widely understood to pose severe hazards to the environment. Also, one of the primary goals of green chemistry is to reduce solvent consumption. Furthermore, selecting the appropriate solvent can considerably improve the sustainability of a chemical production process. The use of so-called green solvents, such as supercritical fluids and ionic liquids, has also been extensively researched [32]. Notably, twelve (12) requirements for the conformity of green solvent have been proposed, viz; availability, price, recyclability, grade, synthesis, toxicity, biodegradability, performance, stability, flammability, storage, and renewability [33]. Nonetheless, the majority of solvent technologies that lead to increased sustainability are derived from the use of wellestablished and workable solvents. It is also clear that increases in business performance are necessary for the effective adoption of environmentally friendly procedures. Process chemists and engineers must work closely together to select the right solvents, use the fewest solvent classes possible in each step, steer clear of azeotropes and emulsions, optimize reflux or near-reflux conditions for high-temperature extended reactions, and, lastly, maximize solvent recovery and distillation in the process [34]. Similarly, close cooperation between chemical engineers and process chemists is necessary, as the latter are typically more skilled in azeotrope production, distillation, and process optimization [35]. In addition, several risk control techniques can be employed along the various chemical steps involved in the fabrication process to reduce environmental risks. The use of different precursor molecules, catalysts, solvents, and reagents, as well as alternating target product production, real-time process monitoring, and short-duration synthesis has aided the realization of green chemistry in industrial operations. 3.0 APPLICATION OF SYNBIO IN ENVIRONMENTAL MICROBIOLOGY SynBio has been applied in environmental microbiology operations to produce biotreated systems capable of mitigating the levels of toxic recalcitrant organic pollutants, heavy metals, and other environmental contaminants in the environment. For example, breakthroughs in SynBio have allowed the development of engineered bacteria that can consume recalcitrant non-biodegradable waste such as plastic waste [36]. Synthetic microbes with optimized efficiency in sensing, degrading, and reporting toxic pollutants in the environment are now been designed. Also, the development of SynBio-based biosensors with customized abilities is now not only used as herbicides and pesticides but also applied to sites containing heavy metals or other environmental contaminants that need remediation [37]. SynBio enjoys enormous industrial applications for the implementation of the concept of green chemistry. The application of SynBio principles has enabled the fabrication of enzymatic modalities for the realization of renewable and environmental-friendly bio-products such as bioplastics and biofuels, renewing hopes for the actualization of clean energy and sustainable environment at the heart of industrialization [38, 39]. 3.1 Merits of SynBio in Environmental Microbiology Recently, SynBio has shown great potential in re-engineering microorganisms with enhanced functionalities for performing more efficient biodegradation and bioremediation processes, resulting in more sustainable environments [40]. SynBio technology has improved the degradation of resistant compounds in polluted soil by optimizing the biodegradation capabilities of bacteria via genome manipulation [12]. Presently, microbial consortiums can be modified using SynBio-based technologies for improved biodegradation. A microbial consortium refers to a group of microorganisms working together to undertake a single complex metabolic activity. The design of synthetic microbial consortia with improved biodegradation and bioremediation outcomes is another huge accomplishment brought on by SynBio technology [41]. These microbial consortia are capable of degrading a broad range of pollutants in wastewater and other industrial effluents [40]. The metabolic functions of these synthetic microbes are engineered to exhibit excellent degrading abilities on certain environmental pollutants [14]. Environmental monitoring and biosensoring have also seen massive improvement via the application of SynBio technology. In the last few years, SynBio-based engineered microorganisms have been introduced into the environment to screen and detect harmful compounds or adverse environmental conditions and today is seen as a powerful environmental monitoring and assessment tool [40]. Sequel to this, researchers now design microbial agents capable of detecting certain pollutants occurring in the environment. These microorganisms produce fluorescent proteins in response to target toxic substances and thus monitor the concentrations of these noxious chemicals in the environment (whether air, soil, or water) within certain limits [42]. 3.2. SynBio-Based Bioremediation Synthetic biology has numerous potentials and is being put to good use more and more in industrial microbial operations, particularly in bioremediation [12]. The deployment of engineered bacteria to degrade hazardous materials in the environment and restore the ecosystem is thought to be an efficient approach to bioremediation. These bioremediation efforts have been hugely successful via SynBio-based development of microbial entities capable of digesting environmental recalcitrant pollutants, including polycyclic aromatic hydrocarbons (PAHs), and Per- and polyfluoroalkyl substances (PFAS) as shown in Figure 3 [43, 44, 45]. Currently, researchers are now able to construct key microbial biochemical pathways that effectively target the degradation of certain waste or pollutants, which fuels the pathways as substrates, and in some cases results in the synthesis of value-added products [12]. Also, toxic and environmental recalcitrant heavy metals, such as cadmium, mercury, lead, arsenic, and copper, which are capable of inflicting devastating adverse effects on human health as well as on the environment are now monitored and sequestered from the environment via SynBio techniques. In this regard, certain microorganisms have been engineered as biosensors capable of selectively detecting heavy metals in contaminated areas more rapidly and efficiently, as well as binding and removing these noxious compounds from the affected area [46]. Figure 3: Per-And Polyfluoroalkyl Substances from the Environment [45]. Conventional bioremediation methods are impeded by several drawbacks. They require more time, remove or assimilate fewer pollutants, disrupt natural ecosystems by covering more land for extended periods, and cause unpleasant odors in the surrounding area [47, 2]. For the greatest outcomes, scientists are therefore keen to find novel bioremediation strategies [48]. Application of synthetic biology has been shown to enhance bioremediation processes (Figure 4). In this regard, [49] described synthetic biology as a boosting strategy in bioremediation. It has been demonstrated that this approach captures the metabolic and catabolic complexity while utilizing the synthetic capacity of the microbial population [50]. Basically, information required to develop synthetic microbial models for bioremediation are obtained by mining genes from appropriate databases [51]. Computer logic can then be used to determine how microbial cells interact with compounds that are resistant to their effects [52]. Combining these strategies can help develop microbes into novel and fascinating biological forms utilizing their innate metabolic ability [47]. Figure 4: SynBio-based strategies for improved bioremediation Generally, the identification and removal of hazardous and recalcitrant heavy metals in the environment has been a key challenge to environmental scientists and this continues to pose a threat and has prompted the need to propose novel approaches to deal with this menace [53]. In a bid to address these problems, a study deployed SynBio-based genetic circuits and reporter functionalities to ensure higher sensitivity, greater effectiveness with various types of contaminated materials, and cost-efficiency. A detection range of 100 nM-1 μM and 100 nM10 μM for P. fluorescens and E. coli, respectively was recorded. Another study by [54] used a pmerRBPmerlux genetic circuit to detect mercury in soil samples, in which the rate of release of mercury into the water from the soil was speed-up by using a rhamnolipid biosurfactant and a bioluminescent immobilized E. coli MC106 cell, which contained the genetic circuit. Progressively, [55] developed a cell-free system using an evolved mutant of ArsR that enabled efficient, sensitive detection of Arsenic with a limit of 3.65 μg/L which is within the limit given by WHO. In a study carried out by [56] to establish the most effective biosensor combination, thirty whole-cell cadmium biosensors were constructed using WCB KT-5-R with P. putida KT2440 as the host, and a gene circuit comprising mCherry and CadR. To boost the efficiency, a positive feedback amplification module and a larger reporter gene dose were introduced. From their result, whole-cell biosensors (WCBs) with the T7RNAP amplification module, p2T7RNAPmut-68, demonstrated great specificity and enhanced cadmium tolerance with a detection limit of 0.01 [57] engineered E. coli Rosetta that was able to express ribB and OprF with promoter PcusC and Pt7, respectively that could produce porin and detect Cu2+ to generate riboflavin. This modified strain's cell membrane permeability was increased, and the concentration of riboflavin generated (1.45-3.56 M) was correlated positively with Cu2+ levels (0-0.5 mM). Furthermore, increased production of riboflavin was observed upon activation of PcusC in the presence of Cu2+ in water. This strain was then employed in microbial fuel cell (MFC)-based biosensors. Resultantly, the liberation of riboflavin into the extracellular matrix by the OprF-encoded porin enhanced MFC voltage generation. A linear correlation was also recorded between Cu2+ at concentrations ranges of 0.1-0.5 mM and MFC biosensor voltage generation (248-407 mV), indicative of the suitability of this system in Cu2+ monitoring in drinking water [57]. 3.3 Biosensors Biosensors are analytical tools that translate electrical signals from a biological reaction [58]. There are several varieties of biosensors, such as enzyme-based, thermal, tissue-based, DNA, piezoelectric, immunosensors, and immunosensors. Biosensors are essentially required to have high specificity, be reusable, and be unaffected by physical conditions like pH and temperature [59]. Essentially, transcription-factor-based (TFB), RNA-based (RNAB), and twocomponent biosensors (TCBs) are examples of genetically encoded biosensors [60, 61, 62]. The TCB is composed of a transmembrane sensor histidine kinase (SK), which measures extracellular levels of a given metabolite, alongside an SK cognate cytoplasmic response regulator (RR), and an RR cognate promoter [63]. Specific metabolite concentrations within cells are detected by TFBs and RNABs [64]. Therefore, the variations in the spatial distribution of the metabolites that are identified dictate how these biosensors should be used. 3.3.1 Biosensor Fabrication The biosensor output and performance are optimized by using different engineering strategies to fine-tune the biosensor components (promoters, RBS, and operator) [65]. Additionally, biosensor specificity are being modified using RNA and protein domain swapping strategies [66]. The designed biosensors usually respond to extracellular or intracellular level of a single specific compound by generating visible signals, such as bioluminescence or cell growth [67]. Hence, coupled with the desired biosensors and the diverse mutagenesis strategies, the intended genotype can be tested via high-throughput screening of the measurable phenotype. By doing this, TCBs can detect changes in the extracellular concentration of a target chemical substance and can be used in directed evolution [68]. Directed evolution is a valuable tools used for manipulating the structure and functions of protein by exploring natural evolution, but on an abridged duration. It allows for rapid selection of variants of biomolecules with more suitable properties required for a particular application [69, 70]. Intracellular substances can be detected by TFBs and RNABs. Notably, the spatial distribution of the substances identified should determine which biosensor type is applied [71]. However, currently, the biggest constraint to this technique is to precisely and effectively construct these biosensors [59]. The primary source of time and labor expenditures associated with trial-and-error methods for producing the intended biosensors is the optimization of TF, SK, RR, and riboswitch expression levels and structures [72]. To address this issue, deep learning, and machine learning-based artificial intelligence technologies are starting to be included in the biosensor design process, greatly enhancing the accuracy and productivity of the final product [73]. [59] opined that because biosensor design does not yet have a unified large data-collecting method for artificial intelligence model training, it is premature to use artificial intelligence in biosensor design. 3.3.2 Coupling Biosensors with Omics Technologies Furthermore, it has been reported that biosensors could function more efficiently when combined with high-throughput omics technologies, ultimately affording a systems-level view of the organisms, macromolecules, and metabolites of study [74]. Data obtained from -omics studies could be leveraged to restore microbial activities and ecological functions, as well as discover molecular switches in microbial populations, such as genes linked to greenhouse gas production. The deployment of -omics technologies in microbial population studies has been very operative in establishing ecological hypotheses. It is insufficient to solely provide allinclusive information regarding certain cause-and-effect conditions [75]. On the other hand, a reductionist approach that investigates the distinct impacts of individual microbial cells and their liberated biomolecules on environmental outcomes could be achieved using biosensors [76]. Biosensors can generate additional temporal and spatial clue on the activities of certain members of a given microbial community, the environmental determinants that stimulate cellular behaviors, and the impacts of the local environment on the bioavailability of biomolecule [77]. 3.3.3 SynBio-Enhanced Biosensors Applications SynBio technology has enabled the fabrication of improved biosensors used in environmental monitoring, which in turn has facilitated the production of clean water, void of heavy metal toxicity. A recent submission documented the discovery of a genetic circuit in bacteria that, in response to traces of heavy metal exposure (such as arsenic), produced chromophoric proteins. Investigators are now able to create biological systems that can react to and identify dangerous ubiquitous substances that are difficult to control, such as pesticides and herbicides, thanks to SynBio concepts [78]. Generally, advances in biosensor development have had significant impacts on the implementation of environmental monitoring, clean energy, medical diagnostics, improved agriculture, and food safety, in recent years. Recently, investigators and medical associations have switched focus toward using low-cost biosensors to test food and water pollutants, manage human biological processes, determine precise health diagnoses, and other applications [79]. Researchers and medical practitioners require safe and cost-effective methods of conducting research, guaranteeing public safety, and providing personalized health care to patients. Biosensors application is one of such approach that can be simply implemented [80]. Biomedical diagnostic research is becoming increasingly important in the modern medical profession. The applications of biosensors include infectious disease screening and early diagnosis, chronic illness therapy, health management, and wellbeing monitoring. Improved biosensor technological capabilities enable disease detection and tracking of the body's reaction to therapy [81]. Basically, a biosensor comprises three modules, viz; the sensitive biological element, which attaches to the target molecule, the transducer, which converts the interaction into a measurable signal; and the signal processor, which presents the result in an easy-to-read manner. Usually, DNA circuit diagrams, which show details on the genes in each module, the regulation of gene expression, and the interactions between module components, are used to illustrate biosensors. Biosensor input and output relationships usually have a sigmoidal form. A sensor's dynamic range is the difference between its maximum input before saturation and the threshold environmental input required for activation, also known as the limit of detection. The recent influx of novel synthetic biology modules has significantly expanded the spectrum of detectable inputs, the intricacy and functionalities of processing modules, and the range of conditions where outputs can be identified. Thus, there is an opportunity to develop biosensors that address fundamental questions in fields such as environmental engineering, biogeochemistry, geobiology, and ecosystem ecology. Although a few early tools were utilized in environmental samples [82,83], these resources have not been widely accessible to the Earth and environmental science communities. Furthermore, advanced biosensors provide an opportunity to investigate unresolved environmental research inquiries. This includes detecting biogenic substances at micro concentrations, observing organisms interactions, monitoring how environmental cues influences cell-cell signaling, quantifying variations in horizontal gene transfer (HGT) in the changing environments, and recording information in cells while preserving spatial and temporal heterogeneity in the natural environment. Biosensors, which continuously capture information at the micron scale, offer unique opportunities for studying ecosystems from a microbial perspective. Moreover, the evolving innovations of SynBio technology have pulled through the development of an avalanche of improved biosensors. These encompass the creation of more sophisticated genetic circuits and approaches for fine-tuning circuit components for environmental applications. SynBio principles have made feasible the development of in-vitro and in-vivo biosensors [84]. Originally, biosensors were developed by programming easily modifiable and rapidly growing bacteria strains. However, while these bacteria laid the foundation of biosensor creations, the recent growing initiative to broaden the horizon of reliable and programmable microbial strains via SynBio concepts remains the mainstay of modern biotechnology [85]. Biosensors derived from environmental microbes could prove valuable in reporting new types of information within more realistic settings. For instance, enabling biosensors to report on their own experiences in situ within environmental matrices. Recent innovations in cell-free biosensors have facilitated the creation of fast and easily deployable sensors capable of monitoring macroscale spatial and temporal heterogeneity at field sites. This is analogous to point-of-care diagnostics commonly used in biomedical applications. 3.4 Advances of SynBio in Harnessing Environmental Sustainability Despite the significant improvement in the standard of living synthetic chemistry and the chemical industry have offered humans, they have also posed tremendous negative impacts on human health and the environment in terms of toxic waste, and pollution, and represent serious threats to public health [30]. The growing awareness and rising need for a clean environment geared in part by global warming and environmental sustainability have driven the emerging concept of green chemistry, which is the act of designing synthetic processes and products in ways that generate the least toxic compounds as well as reduces the requirements of energy and natural resources [86] nature has contributed immensely to the actualization of this goal. Several years of evolution have resulted in an extremely diversified assortment of natural products and their associated enzymatic processes [87]. Synbiologists are taking advantage of the wealth of possibilities nature affords to design chemicals and synthetic processes in more renewable forms to mitigate pollution at all phases of production, which is the mainstay of the goal of green chemistry [88]. There are many advantages that biosynthetic technologies have over industrial chemical synthesis. Naturally, enzymes catalyze their specific reactions most efficiently and frequently under certain optimized conditions, including normal temperatures and pressures, neutral pH, and aqueous solutions, and allow for the simultaneous operation of a variety of enzymes within the same medium, such as organelles or cells [89]. This concept has enhanced the creation of multiple-step synthetic pathways for the in vivo production of complex compounds from less expensive and renewable feedstock (Figure 5). Figure 5: A schematic of the possible contribution of SynBio to green chemistry. Engineered organisms can produce a wide range of key compounds from renewable resources, waste, and potentially harmful substances such as carbon dioxide. 3.5 Potential Impacts of SynBio on the Environment and Society The possible impacts of SynBio on the human community and its environment are broad and complicated. Although SynBio renders clear-cut potential to address several sustainable development goals as well as provide solutions to deal with environmental and societal bottlenecks, it also raises crucial social and ethical concerns [90]. The design and deployment of synthetic microbes or biomacromolecules into the environment can result in alteration in the normal composition of ecosystems which could ultimately be detrimental to human health. The high possibility of spreading genetically modified microbes into natural populations, which could sprout unintended repercussions poses great concerns among policymakers [91]. There are also several social and ethical concerns associated with SynBio as pertain to the main beneficiaries of the technology and risk bearers. Therefore, it is necessary to consider a caseby-case basis to achieve a balanced compensation for beneficial attributes of SynBio technologies as well as considering possible detrimental outcomes for vulnerable groups [92]. Hence, it would be appropriate to design and implement regulatory frameworks regarding the application of SynBio technologies [92]. 3.6 Safety Concerns and Ethical Issues Among the drawbacks of SynBio are its safety profile and that of any of its end-products. The major safety concerns focus on the possibility of accidental escape into nature by these artificial microbes, which could cause harm to human health or have negative environmental impacts [93]. A case of reference is the recent COVID-19 outbreak that claimed many lives [94]. Therefore, learning from experience with such heinous threats, many ethical issues and safety concerns have been raised about the application of SynBio technologies. For policymakers, the danger that artificial cells or their products will be abused and weaponized, in addition to the fear that artificial pathogens could mutate and become invasive or harmful, then spawn diseases affecting public health or even distorting ecosystems are the major hindrances to the full adoption of this innovation [95]. Therefore, many experts have come up with the view that safety measures and standards governing artificial microorganisms should be continuously reviewed at each stage of their progress to ensure they are not harmfully deployed. Moreover, the fear that some of these synthetic organisms might cause unexpected threats to human health or the environment in the future has also caused many researchers' ethical concerns [96]. In fact, the ethical considerations and moral implications of creating life in the lab are also worrisome [97]. As a result, several regulatory frameworks have already been developed with the aid of which it will be possible to monitor global conformity with respect for ethical values when designing and using synthetic cells [97, 98]. 4.0 CONCLUSION Since its inception in the 1970s, pioneered by the early developments in genetic engineering, SynBio has since advanced immensely, with the development of newer and more sophisticated techniques and tools for editing microbial genomes. SynBio has shown enormous prospects in actualizing several sustainable development goals, such as the generation of sustainable food products and renewable energy supply. SynBio technologies are increasingly deployed to produce novel and sustainable commodities as alternatives to traditional environmentally detrimental products. The actualization of green chemistry and bioremediation of contaminated environments has been greatly enhanced with the introduction of SynBio technology. 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