Do amino acid functionalization stratagems on carbonaceous quantum dots imply multiple applications? A comprehensive review

Sterically chained amino acid-rich water-soluble carbon quantum dots as a robust tumor-targeted drug delivery platform

Effective antitumor nanomedicines maximize therapeutic efficacy by prolonging drug circulation time and transporting drugs to target sites. Although numerous nanocarriers have been developed for accurate tumor targeting, their limited water solubility makes their stable storage challenging, and poses biosafety risks in clinical translation. Herein, we choose reduced glutathione (GSH) to quick synthesize gram-scale water-soluble large amino acids mimicking carbon quantum dots (LAAM GSH-CQDs) enriched in steric chain amino acid groups with solubility of up to 2.0 g mL-1. The water-solubility arises from a hexagonal arrangement formed between amino acid groups and water molecules through hydrogen bonding, producing chair-form hexamer hydration layers covering LAAM GSH-CQDs. This endows a noticeable stability against long-term storage and adding electrolytes. Specifically, they exhibit negligible protein absorption, immunogenicity, and hemolysis, with stealth effect, showing an extraordinarily tolerated dose (5000 mg kg-1) in female mice. The rich amino acid groups simultaneously endow them considerable tumor-specific targeting. The loading of first-line chemotherapeutic drug doxorubicin onto LAAM GSH-CQDs through π-π stacking without sacrificing their merits achieves superior tumor inhibition and minimal side effects compared to commercial doxorubicin liposomal. The tumor-targeted drug delivery platform offered by LAAM GSH-CQDs holds significant promise for advancing clinical applications in cancer treatment.

Investigating the electronic properties of edge glycine/biopolymer/graphene quantum dots

This study systematically investigated four types of graphene quantum dots (GQDs) AHEX, ZTRI, ZHEX, and ATRI, and their interactions with glycine to form GQD-glycine complexes. Utilizing density functional theory (DFT) and the PM6 semiempirical method, the study analyzed electronic properties and structure-activity relationships. Global reactivity indices were calculated using Koopmans' theorem, and quantitative structure-activity relationship (QSAR) parameters were assessed via SCIGRESS 0.3. The study further explored interactions using density of states (DOS) and quantum theory of atoms in molecules (QTAIM) analyses. Key findings revealed that glycine interaction significantly increased the total dipole moment (TDM) and decreased the HOMO/LUMO energy gap (ΔE) for the GQD-glycine complexes. Notably, ZTRI/glycine showed a TDM of 4.535 Debye and a reduced ΔE of 0.323 eV, indicating enhanced reactivity. Further interactions with cellulose, chitosan, and sodium alginate identified the ZTRI/glycine/sodium alginate composite as the most reactive, with a TDM of 8.020 Debye and the lowest ΔE of 0.200 eV. This composite also exhibited the highest electrophilicity index (56.421) and lowest chemical hardness (0.145 eV), underscoring its superior reactivity and stability. DOS analysis revealed that biomolecules contributed the most to molecular orbitals, with carbon atoms contributing the least. QTAIM analysis confirmed the greater stability of the ZTRI/glycine/sodium alginate complex compared to other studied composites. These results highlight the enhanced reactivity and stability of GQDs when interacting with glycine and sodium alginate.

Hybrid nanostructures of nitrogen-doped carbon dots and aromatic amino acids: Synthesis, interactions at interfaces and optical properties

Nitrogen-doped carbon dots (NCD) were synthesized using a simple and fast hydrothermal route, employing citric acid and urea as precursors. The resulting NCDs were non-covalently functionalized (conjugated) with aromatic amino acids, namely phenylalanine (Phe) and tryptophan (Trp). Atomic force microscopy revealed that the NCDs exhibit a disk-like morphology with an average diameter of approximately 60 nm and an average height of about 0.5 nm. Following conjugation, the particle height increased to around 3 nm. UV-vis spectroscopy analysis indicated successful conjugation of the amino acids to the NCD nanostructures. Additionally, DFT numerical calculations based on three differently N-doped clusters were performed to elucidate the nature of the non-covalent interactions between NCDs and the corresponding amino acids. Photoluminescent spectra demonstrated a stable and strong fluorescence signal for both hybrids in the UV region. The most significant changes were observed in the case of Trp-conjugation. In contrast to phenylalanine, the non-covalent bonding of tryptophan to NCDs strongly influenced the visible emission (around 500 nm) originating from surface states of the dots.