"Kasoj Supplementary data"

"Matrix Metalloproteinase-9 (MMP-9) is a promising prognostic, monitoring, and predictive biomarker for a range of inflammatory and proteolytic disorders like cardiovascular diseases, autoimmune conditions, kidney disorders, and various cancers. Matrix Metalloproteinase-9 monitoring helps in disease identification, tracking progression, understanding drug effects, and efficacy; however, constant monitoring using standard methods like ELISA and mass spectrometry is expensive, making it inaccessible for widespread use. Our primary objective was to develop a rapid, affordable, non-invasive, and label-free method for Matrix Metalloproteinase-9 quantitation. To achieve this, we utilized gold nanoparticles, taking advantage of their unique size-dependent localized surface plasmon resonance property, which causes them to change color according to their size. We created an Aptasensor by conjugating gold nanoparticles with the Matrix Metalloproteinase-9-specific aptamer, a single-strand DNA which is highly specific and simple to synthesize compared to antibodies. We have used the adsorption method for aptamer functionalization, eliminating the complicated and expensive thiol modification usually needed by current Matrix Metalloproteinase-9 nanosensors, which is a significant improvement in our design. Our sensor showed a limit of detection of 15 ng\/mL, displaying high sensitivity, and high specificity. A mean recovery rate of 99 \u00b1 7% was achieved in diluted urine samples demonstrating the sensor's effectiveness for non-invasive Matrix Metalloproteinase-9 level detection. This simplified, highly sensitive sensor design provides a foundation for the development of a microfluidic paper-based Point-of-Care device that can enable affordable continuous Matrix Metalloproteinase-9 monitoring for the general population.  "