Selective Adsorption of Trace Biomolecules by Amino Acid-Functionalized Ti₃C₂T_x MXene

Accurate detection and enrichment of trace-level biomolecules are essential for early disease diagnosis, environmental monitoring, and biotechnological research. However, conventional adsorbents often lack the sensitivity and selectivity required at ultralow analyte concentrations. Here, a systematic study is conducted on dopamine adsorption on amino-acid-surface-modified Ti₃C₂T_x MXene nanosheets covalently grafted onto glass wool via silane linkers. Comprehensive characterization confirms the stability of the MXene lattice and successful functionalization. Continuous-flow columns packed with amino acid-MXene-coated glass wool are fabricated, enabling preconcentration and recovery from real samples. Adsorption follows the Langmuir isotherm and pseudo-second-order kinetics, indicative of chemisorption. Thermodynamic analysis (ΔG⁰ < 0, ΔH⁰ > 0, ΔS⁰ > 0) reveals a spontaneous, endothermic process accompanied by increased interfacial disorder. Among the tested modifiers, the cystine-modified MXene exhibits nearly complete uptake (10 ppm analyte) through synergistic effects of electrostatic attraction, hydrogen bonding, and thiol-catechol interactions. Under optimized conditions, >99% desorption is achieved using ultrasonic-assisted ethanol-acetic acid elution, with stable performance over ten adsorption-desorption cycles. Compared with activated carbon and silica gel, the amino acid-MXene adsorbents demonstrate markedly superior capacity, selectivity, and cycling stability, establishing a versatile platform for trace biomolecule capture and enrichment.