Optical detection of heavy metal contaminants: advancements with bio-functionalized gold nanoparticles in environmental monitoring

Heavy metal pollution has toxic repercussions on humans as well as on the environment, and these metals when retained in the environment significantly alter the biological and ecological cycles. The need of the hour is to design an approach for targeted sensing of heavy metal ions present in water bodies. The unique plasmonic and optical properties of gold nanoparticles serve as a foundation for the development of sensitive, selective, and analytical AuNP-based biosensing instruments. Modification/functionalization of AuNPs with different biomolecules such as DNA/DNAzymes, oligonucleotides, aptamers, and peptides serves as linking and capping agents for AuNPs. Functionalization with biomolecules offers biocompatibility, stability, enhanced catalytic activity, low toxicity, and selective binding and sensing to AuNPs. These biomolecules demonstrate distinct recognition skills and unique binding affinities with AuNPs. Bio-functionalized AuNP-based sensors have lately intrigued a significant research interest since they offer a practical use in environmental remediation through the sensing of harmful metal ions along with other pollutants. This review focuses on the new advancements in the development of nano-biosensors based on bio-based surface-functionalized AuNPs as probes, employed in heavy metal ions sensing. The mechanism of functionalization of AuNPs and the development of various optical sensors using bio-functionalized AuNPs have been discussed in depth. Finally, we have discussed the research priorities in this field that will help researchers for further investigations to develop promising future tools serving as "lab-on-chip" sensing devices. [Graphics] .