# Hybrid Quantum Dot as Promising Tools for Theranostic Application in Cancer
## 2 Significance of Hybrid Quantum Dot as Cancer Theranostics
### Perspectives of QDs for Diagnostic/Imaging Utility
Ultra-tiny GQDs exploiting imaging agents and labeling cell membranes are promising agents for drug transportation in cancer therapy because of their outstanding optical properties and transmembrane capabilities. The innate immune system and tumor heterogeneity continue to pose challenges to efficient tumor targeting and penetration; however, NIR irradiation, the energy created by photothermal conversion, can not only release therapeutic cargo but also burst the vesicle to suppress the tumor [63]. When NPs first enter the circulatory system, the innate immune system quickly recognizes them as foreign bodies and gets rid of them through the reticulendorthelial system and the mononuclear phagocyte system. This results in poor delivery efficiency. Because the tumor is a strong physiological barrier, only a small part of the dose injected gets to the deep tumor through the increased EPR effect, which helps particle accumulation. The high interstitial fluid pressure (IFP) and cancer-associated fibroblasts in tumors make it hard for therapeutic drugs to reach the perivascular cells of tumors [64; 65]. Thus, in order to improve tumor therapy, it is crucial to create stealthy and permeable drug delivery systems for the efficient transportation of therapeutic agents. For imaging or diagnostic applications, theranostic nanoplatforms must be robust enough to support them, have a superior cargo-loading and -releasing profile, and be able to do so. Hybridization between distinct NPs is a promising strategy because it can result in the accumulation of a wide range of chemical, physical, and biological properties inside a single complex. Because of their exceptional physical and chemical properties [66; 32], GQDs have been put to use in a variety of biomedical settings. If GQD fluorescence could be made stable, it would greatly improve the efficiency of imaging in the life sciences. Due to their unique chemical, physical, and biological properties, graphene quantum dots (GQDs) and magnetic nanoparticles (MNPs) are two promising choices for use in these hybrids. Both magnetic resonance imaging (MRI) and computed tomography (CT) use contrast agents made of magnetic nanoparticles [67]. In addition to its use in biosensing and magnetic separation, this nanoparticle may also be put to use in hyperthermia therapy, thermo-ablation, targeted drug administration, and even bio-sensing. For example, magnetic nanoparticles could be added to GQDs to make even more complexes that could be used in medicine. The most commonly used magnetic nanoparticles are iron oxide NPs (usually Fe\({}_{2}\)O\({}_{3}\) or Fe\({}_{3}\)O\({}_{4}\)), which can be classified as a pure metal, metal oxide, or magnetic nanocomposites [68]. Combining GQDs with other NPs, such as magnetic nanoparticles, could make them even better for use in biology. Carbon quantum dots (CQDs), a novel kind of fluorescent carbon nanomaterial possessing the unique advantages of high stability, remarkable biocompatibility, easy synthesis and surface functionalization, and comparable optical characteristics, have been extensively studied, especially for bioimaging applications due to their tunable strong fluorescence emission property [69]. In light of the drawbacks of conventional chemotherapy, PTT has emerged as a viable option for treating cancer. Tumors can be heated from the inside out by injecting photothermal substances into the affected area or by targeting the tumor with other agents. These photothermal agents are designed to stimulate near-infrared (NIR) radiation and generate heat upon relaxation, killing cancer cells. Researchers have been investigating several facets of theranostic nanosystems [66] since it has been postulated that these systems, which meet both diagnostic and therapeutic needs, could be utilized to effectively eradicate cancer cells. It has been found that a wide range of organic, inorganic, organo-inorganic, and combinations can act as photothermal agents.