Development of cellulose nanocrystals from waste cotton fabric and polyvinyl alcohol composite hydrogel as non-invasive colorimetric sensor for cysteine detection

Cellulose nanocrystals (CNCs) extracted and purified from cotton fabric waste serve as a promising reinforcing material for developing hydrogel-based colorimetric sensors. The synthesized CNCs were analyzed using X-ray diffraction spectroscopy (XRD), and Transmission electron microscopy (TEM). Then, the PV/Cu²⁺-CNCs/CNFs/PVA hydrogel was synthesized via chemical crosslinking using borax. With the integration of CNCs, the sensor's sensitivity was notably improved, allowing for a more distinct color change visible to the naked eye. Furthermore, the as-prepared hydrogel was applied as a non-invasive urinary cysteine colorimetric sensor using an indicator-displacement assay (IDA). This sensor exhibits a visible color transition from greenish-blue to orange-red in the presence of cysteine, with a linear range of 0-0.6 g/L and a limit of detection (LOD) of 0.017 g/L, covering cut-off (0.25 g/L) in human urine for monitoring Alzheimer’s disease. Ultimately, this hydrogel-based cysteine sensor was successfully tested in artificial urine samples with acceptable results. Consequently, this platform has a potential for Alzheimer’s disease monitoring in the near future.

从棉织物废弃物中提取纯化的纤维素纳米晶（Cellulose nanocrystals, CNCs）是一类极具应用前景的增强材料，可用于开发水凝胶基比色传感器。所合成的CNCs经X射线衍射光谱法（XRD）与透射电子显微镜（TEM）完成表征分析。随后，以硼砂作为化学交联剂，合成了PV/Cu²⁺-CNCs/CNFs/PVA水凝胶。引入CNCs后，该传感器的灵敏度得到显著提升，肉眼可观测到更为鲜明的颜色变化。进一步地，采用指示剂置换法（IDA），将所制备的水凝胶用作无创型尿液半胱氨酸比色传感器。该传感器在半胱氨酸存在时，可呈现从青绿色到橙红色的可见颜色转变，其线性检测范围为0~0.6 g/L，检测限（LOD）为0.017 g/L，覆盖了用于阿尔茨海默病监测的人体尿液半胱氨酸临界浓度（0.25 g/L）。最终，该水凝胶基半胱氨酸传感器在人工尿液样本中完成测试并取得了良好结果。综上，该传感平台在未来具备用于阿尔茨海默病监测的应用潜力。