Innovative biomass-derived P, N-CQDs for the sensitive determination of the novel antiviral baloxavir marboxil in human plasma and dosage forms

This work presents a novel, quick, and economical one-pot synthesis of plant-based phosphorus and nitrogen-doped carbon quantum dots (P, N-CQDs). Microwave treatment of Tricolor Crassula (Crassula ovata) leaves as carbon sources with urea and monobasic ammonium phosphate (NH₄H₂PO₄) as nitrogen and phosphorus sources for 80 s resulted in the formation of blue emissive P, N-CQDs (λ_ex/λ_em of 320/405 nm). The synthesized CQDs were fully characterized, revealing a great quantum yield (35.23 %) and high phosphorus and nitrogen content. Furthermore, they exhibited remarkable efficiency as a fluorescent nanoprobe for the sensitive determination of a new anti-influenza drug, baloxavir marboxil (BXM), which was recently reported to have wide utility as a medication for COVID-19. BXM quantitatively quenched the native fluorescence of P, N-CQDs through a synergistic combination of inner filter effect and static quenching over the concentration range of 0.2–18.0 μg/mL with a LOD of 0.04 μg/mL. The selectivity of the probe was verified in the presence of different metal ions, co-administered drugs, and potential co-existing excipients. The proposed method was further applied for BXM determination in pharmaceutical tablets and spiked human plasma with good percentage recoveries (100.44 ± 1.02 % and 100.23 ± 1.06 %). Finally, the suggested probe’s greenness was assessed using different metrics, confirming its excellent greenness. The rapid synthesis of P, N-CQDs utilizing inexpensive, low-energy microwave radiation and the lack of organic solvents make the produced probe environmentally friendly. This study expands the applications of P, N-CQDs in biomedical and pharmaceutical analysis.