Carbon nano-dot for cancer studies as dual nano-sensor for imaging intracellular temperature or pH variation

Abstract

Cellular temperature and pH govern many cellular physiologies, especially of cancer cells. Besides, attaining higher cellular temperature plays key role in therapeutic efficacy of hyperthermia treatment of cancer. This requires bio-compatible, non-toxic and sensitive probe with dual sensing ability to detect temperature and pH variations. In this regard, fluorescence based nano-sensors for cancer studies play an important role. Therefore, a facile green synthesis of orange carbon nano-dots (CND) with high quantum yield of 90% was achieved and its application as dual nano-sensor for imaging intracellular temperature and pH was explored. CND was synthesized from readily available, bio-compatible citric acid and rhodamine 6G hydrazide using solvent-free and simple heating technique requiring purification by dialysis. Although the particle size of 19 nm (which is quite large for CND) was observed yet CND exhibits no surface defects leading to decrease in photoluminescence (PL). On the contrary, very high fluorescence was observed along with good photo-stability. Temperature and pH dependent fluorescence studies show linearity in fluorescence intensity which was replicated in breast cancer cells. In addition, molecular nature of PL of CND was established using pH dependent fluorescence study. Together, the current investigation showed synthesis of highly fluorescent orange CND, which acts as a sensitive bio-imaging probe: an optical nano-thermal or nano-pH sensor for cancer-related studies.

Carbon dots: Types, preparation, and their boosted antibacterial activity by photoactivation. Current status and future perspectives

“…That is, fragments of graphene sheets and amorphous carbon structures are linked disorderly, as shown in Figure 1a, so they do not exhibit quantum confinement as CQDs and GQDs (Carbonaro et al, 2019). The CNDs have a high degree of carbonization in their nuclei, which is the main responsible for their optical performance (Gadly et al, 2021; Mansuriya & Altintas, 2021). However, CNDs can share certain peculiarities with CQDs, such as a quasi‐spherical morphology, size, percentages of carbon–oxygen material, and light absorption regions (Cayuela et al, 2016).…”

“…CNDs are usually obtained by methods which involve heating. T. Gadly et al (2021) synthesized CNDs from citric acid using acidic conditions to form amorphous and crystalline structures of CNDs. Likewise, C. Fan et al (2018) acquired CNDs using one‐step hydrothermal synthesis from the same precursor (citric acid).…”

Effective strategies to enhance the diagnosis and treatment of RCC: The application of biocompatible materials

“…The significance of temperature and pH in the functionality of organelles, enzyme activity, and protein degradation in tumor cells highlights the importance of nanosensors with dual sensing capabilities that are responsive to changes in temperature and pH. Such sensors demonstrate heightened sensitivity in detecting tumor cells, coupled with excellent photostability and intense fluorescence intensity [ 73 , 74 ].…”

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

“…The popularity of CDs for bioimaging have been attributed to their unique photoluminescence properties and high quantum yields. , Their π-conjugated system absorbs UV light and provides emission of visible light facilitated by both n → π* and π → π* transitions of C=N and C=O, and C=C bonds, respectively. , Many studies suggest that N doping (adding nitrogen) of CDs leads to higher quantum yields . These inherent photoluminescence properties and biocompatibility of CDs make them ideal fluorescent probes, where they have been utilized to image cells, , biomolecules, and various other biological systems. − …”