Recent progress in 0D optical nanoprobes for applications in the sensing of (bio)analytes with the prospect of global health monitoring and detailed mechanistic insights

Continuous monitoring of a variety of biomolecules and bio-relevant ions is of tremendous importance in maintaining the physiological balance and evaluation of metabolic parameters. Therefore, the development of fast, selective, sensitive and reliable sensors and their application in point-of-care testing (POCT) analysis are one of the main interests. Over the past few decades, a variety of zero-dimensional nanomaterials have been extensively developed for the optical biosensing of different bio-analytes due to their unique characteristics, such as high sensitivity, bio-compatibility, and low toxicity. In the present review, the current trends of the research endeavours (2017-2022) based on emerging optical biosensing applications including the systematic classification of various zero-dimensional nanomaterials including carbon quantum dots (CQDs), graphene quantum dots (GQDs), inorganic quantum dots (IQDs), noble metal nanomaterials such as silver nanoparticles (AgNPs), gold nanoparticles (AuNPs), magnetic nanoparticles (MNPs), upconversion nanoparticles (UCNPs) and polymer dots (PDs) are comprehensively described towards the detection of various target-specific bio-analytes, such as deoxyribonucleic acid (DNA), proteins, enzymes, adenosine triphosphate (ATP), adenosine, dopamine (DA), uric acid (UA), glucose, hydrogen peroxide (H2O2), biothiols, cysteamine, and cancer biomarkers. Additionally, an in-depth discussion of the chromo-fluorogenic signaling mechanisms, the detection thresholds, and linear dynamic ranges of detection is presented. The sensitivity of the developed nanomaterials is also summarized for a broad range biological applications in complex bio-matrices, such as human blood plasma, serum, and urine. Ultimately, the gaps and challenges in the present research strategies and future perspectives are highlighted herein to strengthen the current research strategies for the commercialization of "next-generation" nanosensors. The significant research endeavours and technical breakthroughs towards the development of optical nano biosensing platforms give rise to new motivation, which will be highly beneficial in the domain of non-invasive clinical diagnosis.