Bioconjugation Between CdTe Quantum Dots and a Cationic Protein: An Analytical Method to Determine Protamine in Drug and Urine Samples

CdTe quantum dots (QD-CdTe) functionalized with mercaptosuccinic acid (MSA) were synthesized in an aqueous medium, varying synthesis time from 0.5 to 4 h. The nanoprobe characterized by a direct relationship between and QD size (2.61-3.04 nm). QD-CdTe-MSA interacted protamine (PT), cationic protein, forming bioconjugate, thus quenching the photoluminescence intensity generating on-off system. produced at of 1 h (QD-CdTe1) presented PT’s best sensitivity succinate buffer (pH = 5). Under optimized conditions, proposed method linear range 0.05-0.5 mg L-1 (10-100 nM), limit detection (LOD) 0.01 (2 relative standard deviation (RSD) ≤ 2.01% (n 10). interaction PT led aggregation due bioconjugate formation. systems’ hydrodynamic radius varied 4.31 nm (QD‑CdTe1) 30.50 for (QD-CdTe1-PT). was sensitive variation ionic strength based on thermodynamic parameters; it demonstrated that mechanism occurred preferentially through electrostatic forces. Finally, proved be fast, sensitive, viable quantifying drugs synthetic urine samples recoveries above 95%.