Pressure-Dependent Tuning of Photoluminescence and Size Distribution of Carbon Nanodots for Theranostic Anticancer Applications

Abstract

Carbon nanodots (CDs) have recently attracted attention in the field of nanomedicine because of the biocompatibility, cost-effective nature, high specific surface, good near infrared (NIR) photothermal conversion into heat and tunable fluorescence properties, which have paved the way toward incorporating use of CDs into innovative anticancer theranostic platforms. However, a reliable synthesis of CDs with established and controlled physiochemical proprieties is precluded owing to the lack of full manipulation of thermodynamic parameters during the synthesis, thus limiting their use in real world medical applications. Herein, we developed a robust solvothermal protocol which allow fine controlling of temperature and pressure in order to obtain CDs with tunable properties. We obtained different CDs by modulating the operating pressure (from 8 to 18.5 bar) during the solvothermal decomposition of urea and citric acid in N,N-dimethylformamide at fixed composition. Atomic force microscopy (AFM), Fourier transform infrared (FTIR), ultraviolet-visible (UV-vis) and fluorescence spectroscopy were used to assess the role of pressure in influencing size, optical and surface properties of the obtained CDs. While preliminary biological and anticancer performance of CDs was established on the MDA-MB-231 cell line, used as triple negative breast cancer model. Our results indicate that pressure impinge on the formation of carbon nanoparticles under solvothermal conditions and impart desired optical, size distribution, surface functionalization and anticancer properties in a facile way. However, we have highlighted that a strategic surface engineering of these CDs is needed to limit the adsorption of corona proteins and also to increase the average surface diameter, avoiding a rapid renal clearance and improving their therapeutic efficacy in vivo.

Ultrafast Interface Charge Separation in Carbon Nanodot–Nanotube Hybrids

“…However, all of them typically display intense and tunable absorption–emission bands in the visible spectral range, , which are their most important hallmark among other nanocarbons. Their excellent optical response is combined with many additional benefits such as low cost, biocompatibility, non-toxicity, and the great sensitivity to external agents as ions or molecules in solution . Most importantly, CDs also display remarkable electron-donating and electron-accepting capabilities. , The combination of all of these characteristics makes CDs suitable substitutes of quantum dots in many optoelectronic or sensing applications.…”

Functionalization of Metal and Carbon Nanoparticles with Potential in Cancer Theranostics

“…However, bottom-up methods do not allow precise control of the size of the products, often leading to the formation of an extremely heterogeneous product. Only a few reports have investigated synthetic protocols to produce CDs via controlled solvothermal conditions (i.e., temperature and pressure), suggesting the possibility of tuning their physicochemical properties by pressure and temperature-dependent procedures [ 20 , 149 ]. As a consequence, post-synthetic purification, through dialysis or size exclusion chromatography (SEC), is always necessary to obtain highly homogeneous carbon dots.…”

“…Another predominant intrinsic factor of CDs is represented by their surface functional groups that can be very variable (e.g., carboxyl, hydroxyl, amino and amide groups), making CDs highly versatile and easy to functionalize. The surface state, extremely influenced by the adopted synthetic scheme, affects more important aspects of CDs’ profile, such as FL, directional capacity and biocompatibility [ 20 , 23 , 153 , 154 , 155 , 156 ]. The concept of surface functionalization as a new strategy to improve optical properties of CDs was proposed for the first time by Sun et al in 2007.…”

“…In detail, the same scheme of reaction was replicated at 8, 13 and 18 bar, in order to evaluate the influence of pressure parameter on CDs profile. The increased pressure conducted to an increment of the average size and surface carboxyl groups, which resulted in a redshift of the emission; proving the key role of another reaction parameter in the determination of CDs features [ 20 ]. In order to modulate the optical properties to obtain performing CDs in cancer theranostic, functional groups on the surface of CDs are an important factor to take into consideration [ 171 ].…”

“…The potential of this multimodal approach is manifold as it offers to simultaneously achieve efficient treatments with an immediate imaging feedback, opening the way to the implementation of highly targeted and innovative patient-tailored therapies that can be customized according to the individual therapeutic response [ 3 , 4 , 5 ]. To fulfill this purpose, several theranostic materials were explored to date, including metallic nanoparticles (e.g., silver, zinc, gold and iron oxide nanoparticles) [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ], carbon nanomaterials (e.g., nanotubes, fullerenes, nanodots and graphene) [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ], rare-earth elements-based structures [ 26 , 27 ] and polymeric assemblies [ 28 , 29 , 30 , 31 ]. Even though unified by the same goal, theranostic nanomaterials can avail of different features that are direct effects of their physical–chemical, optoelectronic, and magnetic properties, as well as the result of the accurate design of the intelligent nanodevice ( Figure 1 ).…”