A colorimetric glucose sensor with gradient porous polyglycolic acid (PGA) microneedle array patch

Rapid glucose detection holds significance to diabetes. Here, a novel colorimetric glucose sensor for interstitial fluid (ISF) glucose detection is proposed, comprising a gradient porous polyglycolic acid (PGA) microneedle array patch (MAP) for ISF extraction and a porous 3,3',5,5'-tetramethylbenzidine (TMB)-functionalized PGA film for glucose sensing. Instead of using pore-forming agents, porous PGA structure is fabricated by solvent volatility method, which brings the benefit of eliminating residual agents and enabling the formation of uniform, tunable micropores. PGA MAP was designed and fabricated with a gradient porosity from tip (7.2 ± 2.3%, N = 10) to the substrate (48.5 ± 1.1%, N = 10), providing high mechanical strength at the tip and hygroscopicity across the microneedle. With a compression failure force of 0.51 ± 0.13 N (N = 10), it successfully punctured artificial skin model and absorbed 1.40 ± 0.06 µL of liquid in 1 min (N = 10). By using the co-precipitation method, TMB was uniformly distributed inside the microstructure of porous PGA film. It effectively prevents the color errors caused by coffee ring effect. Furthermore, enzymes were well immobilized onto TMB-functionalized PGA film due to its hydrophilicity and porosity. Finally, the sensor exhibits uniform, distinct, and linear color changes in response to glucose with a detection limit of 0.13 mM in the range of 2 to 10 mM.