Susanta Kumar Bhunia

Imaging cancer cells expressing the folate receptor with carbon dots produced from folic acid

Development of new imaging tools for cancer cells in vitro and in vitro is important for advancing cancer research, elucidating drug effects upon cancer cells, and studying cellular processes. We showed that fluorescent carbon dots (C‐dots) synthesized from folic acid can serve as an effective vehicle for imaging cancer cells expressing the folate receptor on their surface. The C‐dots, synthesized through a simple one‐step process from folic acid as the carbon source, exhibited selectivity towards cancer cells displaying the folate receptor, making such cells easily distinguishable in fluorescence microscopy imaging. Biophysical measurements and competition experiments both confirmed the specific targeting and enhanced uptake of C‐dots by the folate receptor‐expressing cells. The folic acid‐derived C‐dots were not cytotoxic, and their use in bioimaging applications could aid biological studies of cancer cells, identification of agonists/antagonists, and cancer diagnostics.

Lipid-Bilayer Dynamics Probed by a Carbon Dot-Phospholipid Conjugate

Elucidating the dynamic properties of membranes is important for understanding fundamental cellular processes and for shedding light on the interactions of proteins, drugs, and viruses with the cell surface. Dynamic studies of lipid bilayers have been constrained, however, by the relatively small number of pertinent molecular probes and the limited physicochemical properties of the probes. We show that a lipid conjugate comprised of a fluorescent carbon dot (C-dot) covalently attached to a phospholipid constitutes a versatile and effective vehicle for studying bilayer dynamics. The C-dot-modified phospholipids readily incorporated within biomimetic membranes, including solid-supported bilayers and small and giant vesicles, and inserted into actual cellular membranes. We employed the C-dot-phospholipid probe to elucidate the effects of polymyxin-B (a cytolytic peptide), valproic acid (a lipophilic drug), and amyloid-β (a peptide associated with Alzheimers disease) upon bilayer fluidity and lipid dynamics through the application of various biophysical techniques.

Bifunctional Carbon‐Dot‐WS2 Nanorods for Photothermal Therapy and Cell Imaging

Multifunctional nanoparticles have attracted significant interest as biomedical vehicles, combining diagnostic, imaging, and therapeutic properties. We describe herein the construction of new nanoparticle conjugates comprising WS2 nanorods (NRs) coupled to fluorescent carbon dots (C-dots). We show that the WS2 -C-dot hybrids integrate the unique physical properties of the two species, specifically the photothermal activity of the WS2 NRs upon irradiation with near-infrared (NIR) light and the excitation-dependent luminescence emission of the C-dots. The WS2 -C-dot NRs have been shown to be non-cytotoxic and have been successfully employed for multicolour cell imaging and targeted cell killing under NIR irradiation, pointing to their potential utilization as effective therapeutic vehicles.

Thenoyltrifluoroacetone (TTA)–Carbon Dot/Aerogel Fluorescent Sensor for Lanthanide and Actinide Ions

Contamination of groundwater with radioactive substances comprising actinides and lanthanides is a significant environmental hazard and thus the development of selective, sensitive, and easy-to-apply sensors for water-soluble actinide and lanthanide ions is highly sought. We constructed a new selective fluorescent sensor for UO22+, Sm3+, and Eu3+ based on a carbon dot (C-dot)–aerogel hybrid prepared through in situ carbonization of 2-thenoyltrifluoroacetone (TTA), a high-affinity heavy metal chelator. The TTA–C-dot–aerogel enabled the detection of UO22+ ions, which induced a significant red fluorescence shift, whereas Eu3+ and particularly Sm3+ ions gave rise to pronounced fluorescence quenching. Importantly, the lanthanide/actinide ion-selective TTA–C-dots could be synthesized only in situ inside the aerogel pores, indicating the crucial role of the aerogel host matrix both in enabling the formation of the C-dots and in promoting the adsorption and interactions of the lanthanide and actinide metal ions with the embedded C-dots.

Lysine-Derived Carbon Dots for Chiral Inhibition of Prion Peptide Fibril Assembly

The transmissible spongiform encephalopathies are a family of diseases characterized by abnormal folding and aggregation of the prion protein. One of the directions in the search for cure for these and other amyloid diseases focuses on the inhibition of protein aggregation by small molecules, short peptides, and nanoparticles. Nanoparticles seem to be particularly promising therapeutic candidates since they are stable, can be made biocompatible, and might readily traverse physiological barriers such as the blood–brain barrier. Here, a novel class of chiral amyloid inhibitors consisting of carbon quantum dots (C‐dots) that are synthesized from either d‐ or l‐lysine (Lys) as the sole carbonaceous building block are reported. The interactions of the chiral lys‐C‐dots with the amyloidogenic determinant of the prion peptide (PrP, 106–126 sequence) in the presence of lipid bilayers appears to be highly stereoselective, with the l‐Lys‐C‐dots being superior to the d‐Lys‐C‐dots in their ability to modulate the structural transformations and aggregation of PrP(106–126). This work provides new insights into chiral effects upon amyloid peptides and opens the way to developing chiral carbon‐based nanostructures as advanced amyloid inhibitors.